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We study the problem of constructing a data gathering tree over a wireless sensor network in order to minimize the total energy for compressing and transporting information from a set of source nodes to the sink. This problem is crucial for advanced computationally intensive applications, where traditional "maximum" in-network compression may result in significant computation energy. We investigate a tunable data compression technique that enables effective trade-offs between the computation and communication costs. We derive the optimal compression strategy for a given data gathering tree and then investigate the performance of different tree structures for networks deployed on a grid topology, as well as general graphs. Our analytical results pertaining to the grid topology and simulation results pertaining to the general graphs indicate that the performance of a simple greedy approximation to the Minimal Steiner Tree (MST) provides a constant-factor approximation for the grid topology and good average performance on the general graphs. Although, theoretically, a more complicated randomized algorithm offers a polylogarithmic performance bound, the simple greedy approximation of MST is attractive for practical implementation.
Parallel and Distributed Systems, IEEE Transactions on (Volume:19 , Issue: 2 )
Date of Publication: Feb. 2008 | <urn:uuid:c25c43e9-657c-4484-afba-3ea3e9798bba> | {
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- primal heuristic (1) (remove)
- Lotsize optimization leading to a p-median problem with cardinalities (2007)
- We consider the problem of approximating the branch and size dependent demand of a fashion discounter with many branches by a distributing process being based on the branch delivery restricted to integral multiples of lots from a small set of available lot-types. We propose a formalized model which arises from a practical cooperation with an industry partner. Besides an integer linear programming formulation and a primal heuristic for this problem we also consider a more abstract version which we relate to several other classical optimization problems like the p-median problem, the facility location problem or the matching problem. | <urn:uuid:cca2b85f-a95e-4f47-8458-a2c069cde003> | {
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Assessing and achieving alignment between an organization’s strategies and its IT/business functions has long been recognized as a critically important question. This paper reports on a project that seeks to overturn established management orthodoxy by establising that strategies can be adequately modeled using conceptual modeling notations and that methodological and tool support can be provided for the task of assessing and achieving alignment between the strategies of an organization and its service offerings. A key element of this enterprise has been the design of SML - the Strategy Modeling Language. This paper presents an interim report from this project that describes how a notation inspired by i* has been used to obtain the diagrammatic modeling component of SML, and how i*-like notions have been used to represent strategy decomposition (required to be able to refine strategies to a level where there is an onotlogical match between the languages used to describe strategies and services). We also comment on how i*-like notions would play a greater role in this project, as a complete model of the enterprise context is brought to bear on the alignment exercise. We provide a brief illustration, and a description of the toolkit implemented on the Eclipse platform. | <urn:uuid:f7b8f7fb-dbd3-4e06-a667-2d4b2c6e1018> | {
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Image Processing & Computer Vision
Abstract: In this paper a new algorithm for recognizing handwritten Hindi digits is proposed. The proposed algorithm is based on using the topological characteristics combined with statistical properties of the given digits in order to extract a set of features that can be used in the process of digit classification. 10,000 handwritten digits are used in the experimental results. 1100 digits are used for training and another 5500 unseen digits are used for testing. The recognition rate has reached 97.56%, a substitution rate of 1.822%, and a rejection rate of 0.618%.
Abstract: A new approach for form document representation using the maximal grid of its frameset is presented. Using image processing techniques, a scanned form is transformed into a frameset composed of a number of cells. The maximal grid is the grid that encompasses all the horizontal and vertical lines in the form and can be easily generated from the cell coordinates. The number of cells from the original frameset, included in each of the cells created by the maximal grid, is then calculated. Those numbers are added for each row and column generating an array representation for the frameset. A novel algorithm for similarity matching of document framesets based on their maximal grid representations is introduced. The algorithm is robust to image noise and to line breaks, which makes it applicable to poor quality scanned documents. The matching algorithm renders the similarity between two forms as a value between 0 and 1. Thus, it may be used to rank the forms in a database according to their similarity to a query form. Several experiments were performed in order to demonstrate the accuracy and the efficiency of the proposed approach.
Abstract: In this paper, a new algorithm for recognizing partially occluded objects is introduced. The proposed algorithm is based on searching for first three matched connected lines in both occluded and model objects, then left and right lines in both occluded and model objects are marked as matched lines as long as they have the same relations of distance ratio and angle to the last matched and connected lines. The process is repeated until there is no more three matched connected lines. The ratio_test is then performed to detect scattered matched points and lines. The new algorithm is invariant to translations, rotations, reflections and scale changes and has computational complexity of O(m.n).
Abstract: Application areas such as medical imaging or satellite imaging often store large collections of similar images. Lossless compression techniques are usually needed in such critical applications. Previous researches have introduced the centroid method, which gets benefit from the inter-image redundancy ì the set redundancy. In this paper a new algorithm is proposed as an extension of the centroid method. Experimental results with two sets of CT and MRI brain images demonstrate the efficiency and superiority of the proposed algorithm in respect to compression ratio. 1
Abstract: The need for Lossless data compression in medical imaging is becoming essential. Medical image database often store large collection of similar images. Traditional compression techniques focused on exploiting redundancy presented in individual images ignoring the set redundancy, which is the inter-image redundancy. Previous research has introduced the centroid method, which gets benefit from the set redundancy. In this paper a new algorithm is proposed as an extension of the centroid method combined with the Quadtree structure widely used before to represent binary images. Experimental results with two sets of CT and MRI brain images demonstrate the efficiency and superiority of the proposed algorithm in respect to compression ratio.
Abstract: The computation of optical flow can be an important part in a diverse number of applications. However, optical flow algorithms can be categorized as either very accurate and slow or very fast and highly inaccurate. None of the optical flow algorithms combined both accuracy and efficiency. Among these algorithms was the phase-based fleet and Jepson algorithm. Although this algorithm has proved to produce relatively accurate results, it can not be exploited in many real-life applications due to its relatively long run-time. The goal of this paper is to combine the accuracy of the phase-based optical flow algorithm by Fleet and Jepson and exploit the parallelism and high performance capabilities of the FPGAs to provide an accurate and efficient optical flow algorithm for FPGA-based applications.
Abstract: Words have always been important carriers of information. They convey a lot of aspects about images in which they are embedded. Inspite of the many approaches that have been proposed to separate text appearances from images, very few of them have handled Arabic script. This paper presents a technique to extract Arabic words from a variety of colored images with complex backgrounds. In order to accomplish the task we have chosen the Connected Components (CC) approach. It starts with the breakdown of the RGB image into tiny homogeneous regions using the watershed transform, followed by region merging. The resulting CCs are aggregated into blocks, some of which are the candidate words. Each block is then condensed into a single vector holding the values of it features. The features generally describe the geometrical nature of the Arabic script, including a set of invariant moments. The final decision as to classify the blocks as Arabic words or other was left up to a support vector machine (SVM) before passing them to an OCR software. The system showed promising results by achieving an accuracy rate of ≈67. | <urn:uuid:7fca0552-9687-4e19-a3cf-521f11675b8c> | {
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Volume 40, Issue 3 (May 2012)
System Identification of a Reinforced Concrete Building Using the Complex Mode Indicator Function and the Hilbert Transform Techniques
The complex mode indication function (CMIF) technique is a singular value decomposition enhancement of the classical peak picking (PP) technique. The disadvantages of the PP technique, namely, its inability to identify closely spaced modes, are largely resolved in CMIF due to the singular value decomposition. Recently, a frequency domain based technique that uses the biased frequency response functions obtained from the Hilbert transform of power spectral densities has been proposed. In this study, the PP, CMIF, and Hilbert transform techniques are successfully applied to the measured output data from a typical instrumented school building in Istanbul. The study clearly shows that the techniques can successfully identify the modal parameters and give similar results for the eigenfrequencies and mode shapes. However, there are some differences in the damping ratio estimates. | <urn:uuid:5a6f902d-2bd1-4d91-9ec2-d37d40323500> | {
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A proposed framework for simultaneous optimization of evacuation traffic distribution and assignment [electronic resource] /
Abstract (Summary)In the conventional evacuation planning process, evacuees are assigned to fixed destinations based mainly on the criterion of geographical proximity. However, such pre-specified destinations (OD table) almost always lead to sub-optimal evacuation efficiencies due to uncertain road conditions such as congestion, road blockage, and other hazards associated with the emergency. By relaxing the constraint of assigning evacuees to pre-specified destinations, a one-destination evacuation (ODE) concept has the potential of greatly improving the evacuation efficiency. A framework for simultaneous optimization of evacuation traffic distribution and assignment is therefore proposed in this study. Based on the concept of ODE, the optimal destination and route assignment can be determined by solving a one-destination (1D) traffic assignment problem on a modified network representation. When tested on real-world networks for evacuation studies, the proposed 1D model presents substantial improvement over the conventional multiple-destination (nD) model. For instance, for a hypothetical county-wide evacuation, a nearly 80% reduction in the overall evacuation time can be achieved when modeling of traffic routing with en route information in the 1D framework, and the 1D optimization results can also be used to improve the planning OD tables, resulting in an up to 60% reduction in the overall evacuation time. More importantly, this framework can be actually implemented, and its efficiency enhancement can be realized simply by instructing evacuees to head for more efficient destinations determined from the 1D optimization performed beforehand.
School Location:USA - Tennessee
Source Type:Master's Thesis
Date of Publication: | <urn:uuid:1b49f590-3063-4641-9689-caeb21422b3c> | {
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Reducing energy usage in steel industries has a large impact to sustainable society. TMEIC, as an electrical equipment supplier to steel industries, is developing new energy saving solutions for hot strip mill lines in which much energy is consumed. Old equipments have been replaced to more efficient ones such as variable speed AC motors and drives. To earn more savings we propose the intelligent energy control systems which utilize the predictive information of mill process control and predicted material properties such as tensile strength, yield stress. One of the solutions is to control rolled material temperature and thickness draft distribution. Especially material temperature has a large effect to energy usage and material properties. We take an approach to minimize the energy consumption in line under the limitation given by material properties prediction system, MPPS, we have developed. The concept, system configuration, and calculation results of the system will be shown. | <urn:uuid:11b9a837-71a1-4a7d-8e82-42b68c844cb1> | {
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Ahmad, R.K. (2011) Diamond nanostructured devices for chemical sensing applications. Doctoral thesis, UCL (University College London).
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Research in the area of CVD single crystal diamond plates of which only recently has been made commercially available saw significant advancements during the last decade. In parallel to that, detonation nanodiamond (DND) particles also now widely made accessible for requisition are provoking a lot of scientific investigations. The remarkable properties of diamond including its extreme hardness, low coefficient of friction, chemical inertness, biocompatibility, high thermal conductivity, optical transparency and semiconducting properties make it attractive for a number of applications, among which electronic and micro electrical-mechanical systems devices for chemical and biological applications are few of the key areas. A detailed knowledge of diamond devices at the prototypical stage is therefore critical. The work carried out encapsulated in this thesis describes the employment of the nanometer-scale diamond structures for the design, fabrication and testing of electronic devices and micro electrical-mechanical system (MEMS) structures for chemical sensing applications. Two major approaches are used to achieve engineering novelty. The first type being devices based on single crystal diamond substrates, which include state of the art δ-doped single crystal diamond Ion Sensitive Field Effect Transistor with an intrinsic layer capping the delta-doped layer for pH sensing and the fabrication and characterization of a triangular-face single crystal diamond MEMS. A comprehensive set of characterisations was systematically performed on the delta ISFET devices. Cyclic Voltammetry has been used to determine the devices’ potential window determining the limits of the applied potential for the Current-Voltage measurements. In solutions of different pH levels, an improved sensitivity of 55mV/pH compared to cap-less design in a previous study is taken as the salient figure of merit. Electrochemical Impedance Spectroscopy sheds some light on device performance in terms of flatband voltages and conduction pathways through circuit modelling. Improved ISFET characteristics such as lower flat-band voltage at 3.74V, simpler conduction paths and drain current saturation onsets show the chosen design is correct and advances delta-doped diamond ISFET research and development work. For the single crystal diamond cantilever, the theoretical modelling supports the triangular-face design to be a better option, generating 3x greater deflections in relation to the conventional rectangular-face design, when operated as a static mode sensor. Based on experimental characterisation methods such as Raman and Energy Dispersive Spectroscopy, the focusedion beam only milling technique inflicts minimum damage to the beam structure. In the second approach, a novel hybrid device idea was conceived and implemented using off-the-shelf silicon ISFETs and cantilevers with a coat of nanodiamond particles on the ‘active area’ surfaces of the respective devices. These nanodiamond-coated silicon devices exhibit high sensitivity for tracing threat signatures such as explosive precursors and analogues with the former in both liquid and vapour medium, and the latter in the vapour phase. The nanodiamond-gated ISFET shows a voltage response of a commendable maximum voltage shift of ~90 mV throughout 0 to 0.1M concentration range of NO2 - and ClO3 - solutions. In the vapour phase detecting 2,4-DNT, a sensitivity of ~20mV/0.4ppm is observed. The nanodiamond-coated silicon cantilever demonstrates a performance advantage of 7.4 Hz/ppb to 1.7 Hz/ppb in a previous study. Fourier Transform Infra-red spectroscopy was carried out on the nanodiamond surfaces hosted by potassium bromide (KBr) discs to ascertain the vapour chemisorption. With the fabrication technique simplified, commercialisation of these proof-of-concept devices should be less time consuming thus enabling quicker deployment of diamond-based surface sensing technology.
|Title:||Diamond nanostructured devices for chemical sensing applications|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Electronic and Electrical Engineering|
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Archive Staff Only: edit this record | <urn:uuid:e48f9d45-f814-49b8-87dd-c1b7b03f5681> | {
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Total internal reflection optical switch in SOI with defect engineered barrier region
Thomson, D, Reed, G, Knights, A, Yang, P, Gardes, F, Smith, A and Litvinenko, K (2010) Total internal reflection optical switch in SOI with defect engineered barrier region Journal of Lightwave Technology, 28 (17). 2483 - 2491. ISSN 0733-8724
Available under License : See the attached licence file.
|Plain Text (licence)|
Official URL: http://dx.doi.org/10.1364/OE.19.011804
Total internal reflection optical switches offer a switching operation which can be wavelength insensitive, thermally stable and polarisation independent. The implementation of such a switch based upon carrier injection in silicon is difficult due to the long diffusion lengths of injected free carriers. In this paper experimental results are presented which show that a reflective type switching operation is obtainable if a barrier formed of defective silicon is used to reduce free carrier diffusion.
Copyright 2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
|Divisions:||Faculty of Engineering and Physical Sciences > Electronic Engineering > Advanced Technology Institute > Photonics|
|Deposited By:||Symplectic Elements|
|Deposited On:||02 Feb 2012 11:26|
|Last Modified:||08 Jun 2013 16:14|
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HKUST Institutional Repository >
Mechanical Engineering >
MECH Doctoral Theses >
Please use this identifier to cite or link to this item:
|Title: ||FRP strengthened RC beams : taper design and theoretical analysis|
|Authors: ||Gao, Bo|
|Issue Date: ||2005 |
|Abstract: ||External bonding of fiber reinforced plastic (FRP) strips to reinforced concrete (RC) beams has been widely accepted as an efficient and effective method for strengthening and upgrading members. With more and more attention being paid to the strengthening area for RC structures using FRP strips, there was been an exponential growth of research. The objective of the present thesis is to study the enhancement of the mechanical performance of strengthened virgin/precracked RC beams through optimization of design variables (e.g. taper ended FRP strips) based on experimental investigation, accompanied with confirmation by numerical analysis and fracture toughness measurement. This thesis also develops reliable theoretical models for proper evaluation of strengthened beam capacity, identifies the tendency of occurrence of various failure modes and establishes practical guidelines for optimized design criteria and material selection.
To predict the load carrying capacity of a strengthened RC beam when concrete cover separation takes place, a simple and accurate design methodology is built. The analytical expression is developed taking into account the stress concentrations in concrete near the tension rebar closest to the cut off point of the FRP strip. The predictions based on the present analytical model are compared to 58 experimental samples from the literature and good agreement has been obtained.
A failure diagram is established to show the relationship among different failure modes for RC beams strengthened with FRP strips, and how failure modes change with the relative FRP strip thickness and the distance from the end of the FRP strip to the support. The idea behind the failure diagram is that the failure mode associated with the lowest strain in FRP or concrete by comparison is likely to occur. The predictions based on the present failure diagram are compared to experimental data and good agreement on failure mode and load carrying capacity has been obtained. Therefore, a design guideline can be developed based on failure diagram.
The experimental study was carried out using a four point bending test. Several bonding parameters are investigated, such as the FRP strip thickness and end tapering of FRP strips. It is shown that increasing the thickness of FRP strips can give rise to a transition of failure mechanisms from rupture of FRP strips, delamination of FRP strips to concrete cover separation. FRP strips with tapered ends can significantly improve the strengthening performance, including increasing both the load carrying capacity and the deflection at failure for both undamaged and ageing/damaged beams.
To prove the experimental results, the finite element method was used to analyze the interlaminar principal, shear and normal stress distributions along the FRP strip-concrete interface, with a special focus on stress concentration at the end of FRP strips. The numerical study indicates that all stress concentrations at the FRP strip ends are reduced with the tapered ends, which in turn leads to a larger load carrying capacity. In addition, the effects of other taper parameters are studied. A simple guideline is proposed for optimal design of tapered FRP strips for given RC beam properties and dimensions. The solutions are formulated based on the determination of critical transition conditions of FRP strips that can give rise to the maximum strengthening performance. The effect of taper configuration of FRP strips on interlaminar fracture behavior is studied through the asymmetric double cantilever beam (ADCB) test. It is found that the taper configuration can significantly affect the load-displacement behavior as well as the crack growth resistance curves. In the sample with tapered FRP strips, there were apparently separate stages of crack propagation corresponding to different FRP strip thicknesses.|
|Description: ||Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005|
xix, 182 leaves : ill. ; 30 cm
HKUST Call Number: Thesis MECH 2005 Gao
|Appears in Collections:||MECH Doctoral Theses|
Files in This Item:
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Search Swinburne Research Bank
Home List of Titles Bimodal distribution of mechanical properties on plasma sprayed nanostructured partially stabilized zirconia
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/41758
- Bimodal distribution of mechanical properties on plasma sprayed nanostructured partially stabilized zirconia
- Lima, Rogerio S.; Kucuk, Ahmet; Berndt, Christopher C.
- The mechanical behavior of nanostructured partially stabilized zirconia (PSZ) coatings was evaluated via Knoop microhardness. The distribution of the microhardness values of the feedstock particles and coatings under a 10 g load were analyzed via Weibull statistics. The percentage of non-molten material was determined using scanning electron microcopy and image analysis. It was observed that the nanostructured coatings present a bimodal distribution in their Weibull plots, indicating the presence of two phases which are described as molten and non-molten. The presence of the bimodal distribution in the mechanical properties allows the prediction of microhardness values of these nanostructured coatings.
- Publication type
- Journal article
- Materials Science and Engineering A, Vol. 327, no. 2 (Apr 2002), pp. 224-232
- Publication year
- Bimodal distributions; Image analysis; Mechanical properties; Microhardness; Nanostructure; Nanostructured coatings; Nanostructured materials; Partially stabilised zirconia; Plasma spraying; Plasma treatment; PSZ; Raw materials; Scanning electron microscopy; Sprayed coatings; Statistical methods; Thermal barrier coatings; Thermal spray; Weibull distribution; Zirconia; Zirconia-yttria
- Publisher URL
- Copyright © 2002 Elsevier Science B.V. All rights reserved.
- Peer reviewed | <urn:uuid:5994477f-ea05-42b9-8eab-4fba726bae77> | {
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A new method is proposed for simultaneously measuring the size and retroreflection of glass microspheres, and a system of statistical characteristics is introduced for monitoring optical quality. Measurements are carried out for various size fractions in the interval 100−700 µm. A criterion for estimating the quality of the microspheres in terms of the throughput power is proposed that makes it possible to expand the possibilities of the technique, based on an analysis of their images. It is shown that it is possible to take into account the influence of defects of the microspheres on the retroreflective properties of the coatings.
L. A. Ivanov, N. N. Kiselev, V. A. Slugin, D. V. Kiesewetter, and V. I. Malyugin, "Measuring the retroreflection from glass microspheres and predicting the quality of retroreflective coatings," J. Opt. Technol. 73, 29-33 (2006) | <urn:uuid:3e66cfd0-ff6a-42e3-9cbc-9ba90e8134bc> | {
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Extensive Material Model Library
To assure that analysis results are accurate as possible, one of the highest priorities at ANSYS is to provide extensive material models and material data. ANSYS Autodyn technology has set the pace for explicit material model availability with an extensive material model library that combines thermodynamic and constitutive responses for many solids, liquids and gases (for example metals, composites, ceramics, glass, concrete, soil and explosives). Combination of virtually all important equation of state, strength and failure/damage material models is possible and supported by all appropriate solution techniques. The library is organized logically by material name and the type of equation of state (EOS), strength model or failure model used. | <urn:uuid:92519fda-9c93-4a28-8211-26dd91acf09c> | {
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Srinivasan, D and Chattopadhyay, K (1997) Nanocomposite microstructure in a melt spun Al-Cu-Zr alloy. In: Materials Science Forum, 243 . pp. 251-256.Full text not available from this repository.
Rapid solidification of a ternary Al-Cu-Zr alloy results in a nanocomposite microstructure. In this study, melt spinning a Al82Cu15Zr3 alloy has resulted in the combined occurrence of, (a) 0.5 mu m sized grains of Al solid solution and (b) fine grains (10-20 nm) of intermetallic Al2Cu (theta) and alpha-Al, along side each other. The larger alpha-Al grains contain nanometric GP zones, with the Zr addition resulting in a grain refinement. In the other type of microstructure Zr promotes simultaneous nucleation of nanosized grains of the two equilibrium phases, Al2Cu and alpha-Al. Both these lead to a very high hardness of similar to 540 VHN for this alloy and can be used as a candidate for a high strength alloy with good ductility at a low strain rate.
|Item Type:||Editorials/Short Communications|
|Additional Information:||Copyright of this article belongs to Trans Tech Publications Inc.|
|Department/Centre:||Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)|
|Date Deposited:||04 Aug 2011 06:51|
|Last Modified:||04 Aug 2011 06:51|
Actions (login required) | <urn:uuid:91db86d5-9d49-4d47-a800-037d54db0fa3> | {
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Department of Mathematics, North University of China, Taiyuan, Shanxi 030051, China
Copyright © 2011 Yakui Xue and Xiafeng Duan. This is an open access article distributed under the
Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
We invest a predator-prey model of Holling type-IV functional response with stage structure and double delays due to maturation time
for both prey and predator. The dynamical behavior of the system is investigated from the point of view of stability switches aspects. We assume that the
immature and mature individuals of each species are divided by a fixed age,
and the mature predator only attacks the mature prey. Based on some comparison arguments, sharp threshold conditions which are both necessary and
sufficient for the global stability of the equilibrium point of predator extinction
are obtained. The most important outcome of this paper is that the variation of
predator stage structure can affect the existence of the interior equilibrium point
and drive the predator into extinction by changing the maturation (through-stage) time delay. Our linear stability work and numerical results show that
if the resource is dynamic, as in nature, there is a window in maturation time
delay parameters that generate sustainable oscillatory dynamics. | <urn:uuid:efa99561-8050-408b-a708-c9f149714af5> | {
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PERMAS enables the engineer to perform comprehensive analyses and simulations in many fields of applications like stiffness analysis, stress analysis, determination of natural modes,dynamic simulations in the time and frequency domain, determination of temperature fields and electromagnetic fields, analysis of anisotropic material like fibre-reinforced composites.
PERMAS determines a large number of results during the course of these analyses, which may be used in the assessment of the structural behaviour like deflections, stresses and strains, natural frequencies and mode shapes, strain energy distribution, sound vibration power density, time history and interaction with other parts of the structure.
Selected examples demonstrate typical areas of application for PERMAS:
- Car Body Analysis Analysis of various aspects in car body development.
- Engine Analysis Analysis of different physical effects for combustion engines.
- Brake Squeal Analysis Idenitifcation of friction induced dynamic instability.
- Rotating Systems Consideration of special constraints for rotating systems.
- Actively Controlled Systems Coupled simulation of structural dynamics and active control.
- Machine Tools Modeling, analysis and stability study of turning machines
- Robust Optimum Design Combination of optimization and reliability analysis.
- Mechatronic Components Thermal design of mechatronic components by electro-thermal FE analysis coupled to CFD analysis | <urn:uuid:a60360c4-6a2e-41a1-8ca0-9bd3d999b5e6> | {
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239. HEALTH MONITORING OF INTERLAMINAR DELAMINATION IN COMPOSITES
Name: Eduardo Velazquez
Grad Year: 2011
Advanced laminated composite have superior in-plane strength. However, their out-of-plane strength is usually one or two orders of magnitude lower due to the fact that it is a matrix-driven as opposed to a fiber-driven property. In order to avoid failures due to interlaminar damage without using high margins of safety, a Structural Health Monitoring (SHM) system can be used. While extensive literature exists on SHM systems for fiber-driven damage and bond-line damage, there is no mention of an SHM system that specifically addresses this type of matrix-driven damage. The proposed SHM system spans the acquisition, location, and reconstruction of Acoustic Emission (AE) damage signals. An algorithm is presented to calculate the most likely location of AE damage signals in a laminated composite structure. Also, a procedure is presented to decide the damage type and reconstruct the loading source time series for a recorded damage signal from a multi-channel system. The SHM algorithm was experimentally validated using a semi-elliptic laminated composite specimen to induce interlaminar delamination at a prescribed thickness location and with an impacted composite plate to induce multi-mode damage. | <urn:uuid:265bda53-24cd-4c33-9578-e1d7f6bec997> | {
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The preparation of magnetic nanoparticle assemblies for biomedical applications
Ghosh, Swapankumar (2006) The preparation of magnetic nanoparticle assemblies for biomedical applications. PhD thesis, Dublin City University.
Full text available as:
Magnetic nanoparticles and their assemblies are subjects of considerable scientific interest for basic research, but also for applications as contrast agents in magnetic resonance imaging (MRI) and for hyperthermia. Such applications depend on the production of stable suspensions of the particles, it is important therefore to characterise the particles in suspension. In this work photon correlation spectroscopy was used to measure of the hydrodynamic size of the particles. NMR techniques were used to determine the stability and to quantify the contrast efficiency (relaxivity) of the suspensions. This work has also provided insight into the nature of the nanoclusters in suspension and into the mechanisms of their growth.
In the first part of this thesis the synthesis, stabilisation and magnetic properties of aqueous magnetite nanocomposite suspensions which are formed in the presence of fatty acids or DNA are presented. For fatty-acid stabilised nanocomposites the NMR response is sensitively dependent on the method of preparation, which cab result in magnetically blocked or superparamagnetic nanoclusters. In the case of the DNA nanocomposites, the biomolecule acts as a template for the preparation of low dimensional assemblies, or magnetic nanowires, whose suspensions exhibit high relaxivity at low magnetic field.
In this second part the synthesis, stabilisation and magnetic properties of magnetite nanoparticle suspensions formed in organic solvents in the presence of long chain surfactants are presented. The influence of nanoparticle size on the magnetic properties is discussed in detail. The NMR response of the particles in non-aqueous suspension is shown to conform to a model previously developed for aqueous suspensions of magnetite. Studies of the controlled clustering of the nanoparticles in organic solvents are presented. The mechanism and kinetics of nanocluster growth are discussed.
Archive Staff Only: edit this record | <urn:uuid:8a5bf8d4-aa8f-4e37-b3fc-a9e9da21a4c6> | {
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Setan, Halim and Majid, Zulkepli and Tahir, Zie Zie Azeanty and Fazli, Mohd. Kamil (2007) Precise imaging and measurement via laser technology for craniofacial and orthodontics applications. In: Malaysian Science and Technology Congress 2007 (MSTC 2007), 4-6 September 2007, Classics Ballroom, Holiday Villa Hotel, Subang Jaya, Selangor Darul Ehsan, Malaysia..
Restricted to Repository staff only
In craniofacial and orthodontics applications, most local practitioners still use traditional contact method (e.g. calipers) for measuring the appropriate physical (i.e. craniofacial and orthodontics) models. The traditional method is slow and subject to significant errors. Consequently, specialised automated imaging (i.e. non-contact, close range, real time/fast, and precise) and measurement techniques are needed for these applications. This paper discusses the research on the uses of latest technologies for craniofacial and orthodontics applications. The research has developed a procedure for precise imaging (with laser technology), 3D modelling, measurement and analysis of digital craniofacial and orthodontics models. The results show that measurements to sub-mm or mm-level precision are achievable, indicating the suitability of the approach for practical applications. The new approach (i.e. fast, precise, and digital-based) also opens more potential applications, as further analysis could be performed on the digital models depending on the requirements.
|Item Type:||Conference or Workshop Item (Poster)|
|Uncontrolled Keywords:||craniofacial, orthodontics|
|Subjects:||T Technology > TA Engineering (General). Civil engineering (General)|
|Divisions:||Geoinformation Science And Engineering (Formerly known)|
|Deposited By:||En. Tajul Ariffin Musa|
|Deposited On:||16 Jan 2008 02:04|
|Last Modified:||10 Apr 2012 04:46|
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Helichrysum plant named 'Harvest Merlot'
A plant variety of the Helichrysum family resulting from a controlled crossing of the varieties of Helichrysum bracteatum `Harvest Fire`, the subject of a...
Chinese Dogwood Tree Named 'Losely'
A Chinese dogwood named `Losely`, a rounded shrubby tree distinguished by the new leaf growth turning bright yellow in mid summer.
Late harvest avocado tree
A new avocado tree has an intermediate growth pattern, with fruit that mature from the end of March through mid-May. The fruit are found in a diversity of...
PEACH TREE, 'BURPEACHTWENTYFIVE'
A new and distinct variety of peach tree (Prunus persica), which is denominated varietally as `Burpeachtwentyfive`, and which produces an attractively colored...
Apple tree rootstock named 'G.969'
A new and distinct variety of apple tree Malus domestica.times.Malus robusta hybrid `G.969` is described herein. The new variety is resistant to fire blight...
Hybrid tea rose plant named 'Meicalanq'
A new and distinct Hybrid Tea rose plant is provided that commonly commences blooming early in the season and forms abundantly and substantially continuously...
Rosa hybrida shrub named 'AUSkitchen'
A variety of rose plant of the shrub class, named `AUSkitchen`. The `AUSkitchen` rose is a plant suitable for repeat flowering production having flowers with...
Rosa hybrida shrub named 'AUSpanier'
A variety of rose plant of the shrub class, named `AUSpanier`. The `AUSpanier` rose is a plant having a large airy shrub with dainty gray-green foliage. The...
Rosa hybrida shrub named 'AUSlounge'
A variety of rose plant of the shrub class, named `AUSlounge`. The `AUSlounge` rose is a plant suitable for repeat flowering production having flowers that are...
Rosa hybrida shrub named 'AUStobias'
A variety of rose plant of the shrub class, named `AUStobias`. The `AUStobias` rose is a plant suitable for repeat flowering production having flowers with buds...
Rosa hybrida shrub named 'AUSquirk"
A variety of rose plant of the shrub class, named `AUSquirk`. The `AUSquirk` rose is a plant having rosette-shaped white blooms, very bushy growth, matt green...
APPARATUS AND METHOD FOR THE FUNCTIONALISATION OF AFM TIPS
The present invention includes an apparatus that holds the probes to a solid support throughout the passages of the functionalisation process, thus avoiding...
METHOD AND SYSTEM FOR NEAR-FIELD OPTICAL IMAGING
A system and method for optically imaging a sample. The method and system uses a controlled scatterer of light positioned in the near field of a sample. The...
METHODS AND MEANS FOR OBTAINING PLANTS WITH ENHANCED GLYPHOSATE TOLERANCE
The present invention relates to plants with a chimeric DNA molecule encoding a glyphosate tolerant EPSPS enzyme under the control of a plant constitutive...
Nucleic Acid Molecules and Other Molecules Associated with Plants and Uses
Thereof for Plant Improvement
Recombinant polynucleotides and recombinant polypeptides useful for improvement of plants are provided. The disclosed recombinant polynucleotides and...
TRICHODERMA STRAINS THAT INDUCE RESISTANCE TO PLANT DISEASES AND/OR
INCREASE PLANT GROWTH
A method for enhancing growth of plants comprising contacting a Trichoderma strain with the plant or a plant seed under conditions effective for the Trichoderma...
Polypeptides having Beta-glucosidase Activity and Polynucleotides Encoding
The present invention relates to isolated polypeptides having beta-glucosidase activity and isolated polynucleotides encoding the polypeptides. The invention...
REGULATORS INVOLVED IN MUSHROOM FORMATION
The invention relates to a fungus or a mushroom and to a method of producing it wherein the fungus/mushroom has an increased expression level of a polypeptide...
VIRUS INDUCED GENE SILENCING (VIGS) FOR FUNCTIONAL ANALYSIS OF GENES IN
The invention relates to the functional analysis of genes in cotton by employing the Virus Induced Gene Silencing (VIGS) method. More specifically this method...
Soybean Transformation Method
A method is disclosed for the Agrobacterium-mediated germline genetic transformation of soybean. The method is based on Agrobacterium-mediated gene delivery to...
Plants Having Enhanced Yield-Related Traits And/Or Enhanced Abiotic Stress
Tolerance And A Method For Making...
The present invention relates generally to the field of molecular biology and concerns a method for improving various plant growth characteristics by modulating...
Plants Having Enhanced Yield-Related Traits and a Method for Making the
The present invention relates generally to the field of molecular biology and concerns a method for enhancing yield related traits by modulating expression in a...
Identification and Validation of Novel Targets for Agrochemicals
The invention relates to a method for identifying and validating plant targets for agrochemicals, comprising the steps of determining gene or protein expression...
METHODS FOR INCREASING PLANT CELL PROLIFERATION BY FUNCTIONALLY INHIBITING
A PLANT CYCLIN INHIBITOR GENE
The present invention provides methods for modulating the growth and/or yield of plants. In particular the methods comprise the use of agents which functionally...
METHOD FOR PRODUCTION OF CHRYSANTHEMUM PLANT HAVING DELPHINIDIN-CONTAINING
Disclosed are: a method for producing a chrysanthemum plant having delphinidin-containing petals using a transcriptional regulatory region for a...
DGAT GENES FROM OLEAGINOUS ORGANISMS FOR INCREASED SEED STORAGE LIPID
PRODUCTION AND ALTERED FATTY ACID...
Transgenic soybean seed having increased total fatty acid content of at least 10% and altered fatty acid profiles when compared to the total fatty acid content...
ISOLATED POLYNUCLEOTIDES AND POLYPEPTIDES, AND METHODS OF USING SAME FOR
INCREASING NITROGEN USE EFFICIENCY,...
Provided are methods of increasing nitrogen use efficiency, yield, biomass, growth rate, vigor, oil content, fiber yield, fiber quality and/or abiotic stress...
Methods for identification of successful transformation without a need for in vitro selection are provided. Direct detection of nucleotide sequences of interest...
SYSTEM FOR EXPRESSION OF GENES IN PLANTS
The present invention provides trans-complementation systems for expressing gene products in plants. In general, the invention provides systems including a...
NUCLEOTIDE SEQUENCES AND POLYPEPTIDES ENCODED THEREBY USEFUL FOR MODIFYING
The present invention relates to isolated nucleic acid molecules and their corresponding encoded polypeptides able confer the trait of modulated low light...
METHODS AND COMPOSITIONS FOR ENHANCED GENE EXPRESSION THROUGH INTRON FREE
The present invention provides a method for selecting an intron for enhanced expression of a nucleotide sequence encoding a polypeptide, comprising: a)...
RICE TRANSGENIC EVENT 17053 AND METHODS OF USE THEREOF
The present invention provides a transgenic rice event 17053 and plants, plant cells, seeds, plant parts, and commodity products derived from event 17053. The...
METHODS OF PRODUCING POLYKETIDE SYNTHASE MUTANTS AND COMPOSITIONS AND USES
The present invention comprises crystalline polyketide synthases, isolated non-native polyketide synthases having the structural coordinates of said crystalline...
Zantedeschia Variety 110224-64275
A Zantedeschia variety designated 110224-64275 is disclosed. The invention relates to the seeds of Zantedeschia 110224-64275, the plants of Zantedeschia...
Zantedeschia Variety 110066-21104
A Zantedeschia variety designated 110066-21104 is disclosed. The invention relates to the seeds of Zantedeschia 110066-21104, the plants of Zantedeschia...
Lettuce Variety Redglace
The present invention relates to a lettuce variety NUN 9044 LT (referred to as "REDGLACE") having resistance against at least strains Bl: 1 to Bl: 26 of downy...
Inbred Broccoli Line BRM50-3906
Inbred broccoli lines, designated BRM50-3906 are disclosed. The invention relates to the seeds of inbred broccoli lines BRM50-3906, to the plants of inbred...
LETTUCE VARIETY RED BLUFF
A lettuce cultivar, designated Red Bluff, is disclosed. The invention relates to the seeds and plants of lettuce cultivar Red Bluff and to methods for producing...
TOMATO HYBRID PS02420487 AND PARENT LINES THEREOF
The invention provides seed and plants of tomato hybrid PS02420487 and the parent lines thereof. The invention thus relates to the plants, seeds and tissue...
TOMATO HYBRID PS01819578
The invention provides seed and plants of tomato hybrid PS01819578 and the parent lines thereof. The invention thus relates to the plants, seeds and tissue...
Process for Generating Transgenic Animals Using Recombinant Lentiviruses
A process for generating transgenic animals using recombinant lentiviruses. The process comprises injecting recombinant lentiviruses into the interstituim of...
Mice That Make VL Binding Proteins
Genetically modified mice and methods for making an using them are provided, wherein the mice comprise a replacement of all or substantially all immunoglobulin...
EGLN2 VARIANTS AND USE THEREOF IN PREVENTING OR TREATING THROMBOEMBOLIC
DISORDERS AND CORONARY HEART DISEASES
The present invention refers to human EGLN2 variants having at position 58 of the amino acid sequence a serine or a leucine and their use in the prevention or...
BASE FOR PROPAGATING AQUATIC ANIMALS
An aquatic animal such as coral is propagated on a base. The base has a top portion with a groove located therein. The groove has converging side walls. The...
ANTI-IL-6 ANTIBODIES,COMPOSITIONS, METHODS AND USES
The present invention relates to at least one novel chimeric, humanized or CDR-grafted anti-IL-6 antibodies derived from the murine CLB-8 antibody, including...
TRANSGENIC LSD1 ANIMAL MODEL FOR CANCER
The present invention relates to a non-human transgenic animal whose genome comprises a stably integrated transgenic nucleotide sequence encoding...
SYSTEMS AND METHODS FOR MANAGEMENT OF SECURE DATA IN CLOUD-BASED NETWORK
Embodiments relate to systems and methods for the management of secure data in a cloud-based network. A secure data store can store sensitive or confidential...
FIRST COMPUTER PROCESS AND SECOND COMPUTER PROCESS PROXY-EXECUTING CODE ON
BEHALF OF FIRST PROCESS
Upon a first process encountering a triggering device, a second process chooses whether to proxy-execute code corresponding to the triggering device of the...
DEVICE, METHOD AND SYSTEM TO PREVENT TAMPERING WITH NETWORK CONTENT
The present invention discloses a system for preventing network content of one or more network servers from being tampered with. The system comprises a content...
DATA INTEGRITY PROTECTING AND VERIFYING METHODS, APPARATUSES AND SYSTEMS
The disclosure provides data integrity protecting and verifying methods, apparatuses and systems. A data integrity protecting method include: calculating a Hash... | <urn:uuid:f79182d2-cd11-4722-8693-b33f8c7441c6> | {
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La0.84Sr0.16MnO3-[delta] cathodes impregnated with Bi1.4Er0.6O3 for intermediate-temperature solid oxide fuel cells
- ISSN: 03787753
La0.84Sr0.16MnO3-delta-Bi1.4Er0.6O3 (LSM-ESB) composite cathodes are fabricated by impregnating LSM electronic conducting matrix with the ion-conducting ESB for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The performance of LSM-ESB cathodes is investigated at temperatures below 750C by AC impedance spectroscopy. The ion-impregnation of ESB significantly enhances the electrocatalytic activity of the LSM electrodes for the oxygen reduction reactions, and the ion-impregnated LSM-ESB composite cathodes show excellent performance. At 750C, the value of the cathode polarization resistance (Rp) is only 0.11Omegacm2 for an ion-impregnated LSM-ESB cathode, which also shows high stability during a period of 200h. For the performance testing of single cells, the maximum power density is 0.74Wcm-2 at 700C for a cell with the LSM-ESB cathode. The results demonstrate the ion-impregnated LSM-ESB is one of the promising cathode materials for intermediate-temperature solid oxide fuel cells. | <urn:uuid:2e1ba395-24d7-4488-aa03-8efbdc428987> | {
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Junction investigation of graphene/silicon Schottky diodes
Citation and License
Nanoscale Research Letters 2012, 7:302 doi:10.1186/1556-276X-7-302Published: 11 June 2012
Here we present a facile technique for the large-scale production of few-layer graphene flakes. The as-sonicated, supernatant, and sediment of the graphene product were respectively sprayed onto different types of silicon wafers. It was found that all devices exhibited current rectification properties, and the supernatant graphene devices have the best performance. Schottky junctions formed between graphene flakes and silicon n-type substrates exhibit good photovoltaic conversion efficiency while graphene/p-Si devices have poor light harvesting capability. | <urn:uuid:48628a33-74f0-4555-8433-6e5a0938de51> | {
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The optical properties of a cloud of anisotropic dielectric particles when the orientational distribution is made nonrandom by interaction with an electrostatic field are studied. Since the interaction energy is determined by the polarizability of the particles, a general expression for the polarizability of nonspherical particles is worked out. In particular, we investigated the response to the electrostatic field of two different dispersions whose component particles are built as clusters of four identical spheres. Although in one cloud the clusters were shaped as linear chains, and in the other cloud the clusters were shaped as squares, the optical properties of both dispersions as a function of the static field are rather similar. There are, however, noticeable ranges of size within which the optical response of the two kinds of particles is substantially different.
© 1995 Optical Society of America
E. Fucile, F. Borghese, P. Denti, and R. Saija, "Effect of an electrostatic field on the optical properties of a cloud of dielectric particles," Appl. Opt. 34, 4552-4562 (1995) | <urn:uuid:e2eae771-5a0c-441d-9c5e-4a8367fa467d> | {
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Positive ion mass spectra obtained by conventional electron impact and by methane chemical ionization were compared with the negative ion mass spectra of 16 typical organophosphorus pesticides using methane, a methane-oxygen mixture, and oxygen as enhancement/reagent gases. In the negative ion spectra, phosphate and phenate anions typically carry a large fraction of the ion current. Displacement of chlorine by oxygen is noted in some cases, and migration of aryl groups from oxygen to sulfur is occasionally noted. Ion-molecule reactions between two species derived from sample molecules have been observed. The sensitivity of the negative ion techniques for the pesticides examined is greater than conventional electron impact or methane positive chemical ionization techniques, and can be up to 800 times more sensitive for some compounds.
Kenneth L. Busch, Maurice M. Bursey, J. Ronald Hass, and G. Wayne Sovocool, "Comparison of Five Ionization Methods for Producing Mass Spectra of Typical Organophosphorus Pesticides," Appl. Spectrosc. 32, 388-399 (1978) | <urn:uuid:b1ee992d-83c2-4d52-97c1-ddea1a7d83dc> | {
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Volume 49, Issue 4 (July 2004)
Age Calculation Using X-ray Microfocus Computed Tomographical Scanning of Teeth: A Pilot Study
To correlate dental age with an individual's chronological age based on the calculated volume ratio of pulp versus tooth volume measured, an X-ray microfocus computed tomography unit (μCT) with 25μm spatial resolution was used to non-destructively scan 43 extracted single root teeth of 25 individuals with well-known chronological age. Custom-made analysis software was used by two examiners to obtain numerical values for pulpal and tooth volume. The ratio of both was calculated and statistically processed. No significant intra-orinter-examiner differences were found. In fact,a very strong concordance correlation coefficient was found. Linear regression analysis showed a coefficient of determination (r) of 0.31 which suggests that there is a rather weak correlation between the volume ratio of pulp versus tooth and biological age. Although rather time consuming, this technique shows promising results for dental age estimation in a non-destructive manner using X-ray microfocus computed tomography. | <urn:uuid:abaff81e-440f-4d2a-b2c8-f7f5b5d1e6bd> | {
"__label__manufacturing": 0.9028223752975464,
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US 5348617 A
A process for selectively etching silicon comprises preparing a solution of etchant which is a non-selective etch for at least silicon and aluminum. The prepared solution is preconditioned by adding atomic silicon to the solution and aging the solution after the addition of silicon for at least 30 minutes. Then, silicon substrates carrying aluminum are immersed in the preconditioned solution to etch the silicon while leaving the aluminum substantially unaffected.
1. A process for selectively etching silicon comprising the steps of:
preparing a solution of etchant which is a non-selective etch for at least silicon and aluminum;
preconditioning the prepared solution by adding atomic silicon to the solution and aging the solution after the addition of silicon for at least 30 minutes; and
immersing silicon substrates carrying aluminum in the preconditioned solution to etch the silicon while leaving the aluminum substantially unetched.
2. The process as set forth in claim 1, wherein the etchant comprises an aqueous solution of hydrazine and quinoxaline.
3. The process as set forth in claim 2, wherein the preconditioning of the solution includes inserting a sample of silicon in the solution for at least five minutes and aging the solution after removal of the sample of silicon for at least 30 minutes.
4. A process for fabricating an electronic device on a silicon substrate, the device having a patterned conductor and an etched aperture in the substrate, the process comprising the steps of:
providing a silicon substrate;
forming the electronic device on the substrate, the forming step including the step of depositing and patterning at least one aluminum pattern, at least part of the aluminum pattern being exposed to an etchant solution and serving as an etchant stop;
providing the etchant solution comprising an aqueous solution of hydrazine and quinoxaline, and preconditioning the etchant solution by treating the solution with silicon and aging the treated solution, thereby rendering the preconditioned etchant solution selective to silicon; and
utilizing the etchant solution to etch an aperture in the silicon substrate to remove an area of the substrate without removal of the exposed aluminum pattern.
5. The process as set forth in claim 4, wherein the preconditioning of the solution includes inserting a wafer of silicon in the solution for at least five minutes and aging the solution after removal of the wafer for at least 30 minutes.
6. A process for fabricating a thin film resonator comprising the steps of:
providing a silicon substrate having first and second surfaces;
depositing alternating metallization layers and piezoelectric layers on the first surface of the substrate, with the metallization layers being the first and last deposited layers;
etching an aperture in the second surface of the silicon substrate to remove an area of the substrate from below the resonating portion of the thin film resonator, the step of etching comprising immersing the substrate in a selective etchant solution comprising an aqueous solution of hydrazine and quinoxaline, and preconditioning the etchant solution by inserting a sample of silicon in the solution for at least five minutes and aging the solution after removal of the sample of silicon for at least 30 minutes, thereby rendering the preconditioned etchant solution selective to silicon in the presence of the metallization or piezoelectric material of the resonator; and
terminating the etching step when the etching reaches the first deposited layer.
7. The process as set forth in claim 6, wherein the metallization layers are aluminum and the piezoelectric layers are aluminum nitride.
8. The process as set forth in claim 6, wherein the layers are deposited by DC sputtering.
9. The process as set forth in claim 8, wherein the layers are about 5 microns thick.
10. The process as set forth in claim 6 wherein the last deposited layer is deposited by a dielectric liftoff process.
11. A process for fabricating a thin film stacked crystal filter, comprising the steps of:
providing a planar silicon substrate with generally planar opposed first and second surfaces;
employing DC sputtering to deposit on the first surface of the substrate three aluminum electrode layers and two aluminum nitride piezoelectric layers, the layers being deposited in alternation, with the first, third, and fifth layers being aluminum and the second and fourth layers being aluminum nitride;
etching a via in the second surface of the silicon substrate to remove an area of the substrate from below the resonating portion of the stacked crystal filter, the step of etching comprising immersing the substrate in a selective etchant which is selective to silicon in the presence of the metallization or piezoelectric material of the resonators; and
terminating the etching when the etching reaches the first deposited layer.
12. The process as set forth in claim 11, wherein the etchant is preconditioned by inserting a sample of silicon in the etchant for at least 30 minutes and aging the solution etchant after removal of the sample of silicon for at least three hours.
13. The process as set forth in claim 12, wherein the piezoelectric layers are each about 2.5 microns thick.
14. The process set forth in claim 11 wherein the etching step comprises immersing the substrate in an etching solution comprising an aqueous solution of hydrazine and quinoxaline.
15. The process as set forth in claim 14 wherein the etching solution is preconditioned by the addition of atomic silicon followed by aging for at least 30 minutes.
This invention relates to fabricating thin film resonators on silicon wafers, more particularly to an etching process useful in such fabrication, and more broadly to a selective etching process useful for forming electronic devices on silicon.
Thin film resonator, or TFR, technology, has received much interest over the last several years. The thin film resonator technology makes possible a class of thin film microwave acoustic devices that are truly compatible with active semiconductor circuitry. The small size of the thin film resonator is compatible with semiconductor technology, and the thin film resonator can be integrated with semiconductor devices onto a common substrate.
To operate in the fundamental mode at VHF to microwave frequency ranges, a resonator must have a thickness in the range of tens of microns to less than one micron. Devices of such thicknesses are very fragile and easily damaged, and require some form of external support during and after manufacture for any practical application. This requirement has given rise to the development of etching techniques which provide for the placing of the device on a silicon substrate, with a cavity etched into the silicon underneath the device to allow free movement of the device. This permits the edges of the device to be supported by the silicon substrate.
The basic thin film resonator technology uses DC magnetron sputtered highly-oriented thin films of dielectric material, preferably aluminum nitride (AlN) or zinc oxide (ZnO). The dielectric film is sandwiched between a pair of conductive electrodes, typically thin film aluminum electrodes, and the electrodes serve not only as electrical interconnections, but also acoustic reflecting surfaces for guiding and trapping the acoustic energy in the dielectric thin film. The acoustic cavity for the resonator is defined by the aluminum-silicon composite membrane structure. That membrane should be of low mass for high frequency operation, and that, in turn usually requires the removal of substrate material underlying the membrane portion of the thin film resonator. It has been typical to accomplish that by first forming a highly doped p.sup.+ region near the top surface of the semiconductor substrate, then etching a via from the bottom surface terminating at the p.sup.+ layer, which functions as an etchant stop. The thin film resonator is then formed on the p.sup.+ membrane. After formation of the thin film resonator, a selective etching process removes the p.sup.+ membrane, leaving the resonator suspended.
In this process of using a p.sup.+ membrane, several problems exist which contribute to the difficulty of manufacturing thin film resonators. For example, the p.sup.+ membranes are fragile and easily damaged. Moreover, the use of a p.sup.+ membrane causes misfit dislocations. These are inevitable with the diffusion of high dopant concentrations, and reduce the crystal integrity of the wafer surface for device manufacture.
Furthermore, the layers of the thin film resonator are themselves extremely thin and fragile. The requirement that the layers be deposited on a membrane which is itself extremely fragile, adds greatly to the difficulty and expense of manufacture and increases the likelihood of introducing manufacturing defects. Moreover, the creation of the p.sup.+ layer is costly and time consuming, requiring high-temperature equipment and long processing times.
Finally, the etchants used in the manufacturing process are extremely corrosive, especially to metals, and could not be permitted to come in contact with the thin film resonators. In the foregoing process, it was therefore necessary to remove the underlying substrate material with the etching step, and for the etching step to be completed prior to the deposition of the thin film resonator layers onto the substrate.
In view of the foregoing, it is a general object of the present invention to provide a process for constructing thin film resonators on silicon wafers which lessens the difficulty and expense of the manufacturing process, and which reduces the number of defects introduced in the manufacturing process.
In that respect, it is an object of the present invention to provide a process which allows the construction of a thin film resonator without the need for creation of a p.sup.+ layer.
It is a further object of the present invention to provide a process which allows the thin film resonator to be deposited on a substrate at a time when the substrate is relatively non-fragile.
It is still another object of the present invention to provide a process which allows the thin film resonator to be deposited before etching of the substrate takes place.
It is yet another object of the present invention to provide a process which allows etching of the substrate to take place in the presence of an electronic device, but without damaging the device.
Accordingly, it is a feature of the present invention to provide an etchant which is selective to silicon in the presence of aluminum.
It is another feature of the present invention that a thin film resonator can be created by a process which employs the etchant late in the manufacturing process, allowing the thin film resonator to be supported by the silicon substrate during manufacture.
It is an additional feature of the present invention that a thin film resonator can be exposed to the etchant without harming the thin film resonator.
It is still another feature of the present invention that an etchant which is non-selective is rendered selective by a preconditioning step interposed in the process flow, which renders the etchant useful at a point in the process where non-selectivity would render it unsuitable, thereby allowing the etching to take place late in the process.
It is yet another feature of the present invention to provide for the fabrication of any electronic device which includes a patterned aluminum layer on a silicon substrate, with the silicon substrate being etched without damage to the electronic device.
In accordance with one aspect of the present invention, a selective etchant for silicon is provided. The selective etchant comprises an aqueous solution of hydrazine and quinoxaline, and atomic silicon in the solution in a sufficient quantity to render the etchant selective to silicon.
In a related aspect of the present invention, a process for selectively etching silicon is provided. The process comprises preparing a solution of etchant which is a non-selective etch for at least silicon and aluminum. The prepared solution is preconditioned by adding atomic silicon to the solution and aging the solution after the addition of silicon for at least 30 minutes. Then, silicon substrates carrying aluminum are immersed in the preconditioned solution to etch the silicon while leaving the aluminum substantially unaffected.
In another related aspect of the present invention, a process for fabricating an electronic device on a silicon substrate is provided. The device has a patterned conductor and an aperture in the substrate underlying at least a part of the electronic device. The process comprises the steps of providing a silicon substrate, and forming the electronic device on the substrate. The forming step includes the step of depositing and patterning at least one aluminum pattern, with at least part of the aluminum pattern being exposed to an etchant in a subsequent etching step. Then, an aperture is etched in the semiconductor substrate to remove an area of the substrate, but without removal of the exposed aluminum pattern.
In accordance with yet another aspect of the present invention, a process for fabricating a thin film resonator is provided. The process includes the steps of providing a silicon substrate having first and second surfaces, and then depositing alternating metallization layers and piezoelectric layers on the first surface of the substrate, with the metallization layers being the first and last deposited layers. An aperture is then etched in the second surface of the semiconductor substrate to remove an area of the substrate from below the resonating portion of the thin film resonator. The step of etching comprises immersing the substrate in a selective etchant which is selective to silicon in the presence of the metallization or piezoelectric material of the resonator. Then, the etching step is terminated when the etching reaches the first deposited layer.
Other objects and advantages will become apparent from the following detailed description when taken in conjunction with the drawings, in which:
FIG. 1 is a diagram schematically illustrating a thin film resonator exemplifying the present invention;
FIG. 2 is a diagram similar to FIG. 1 illustrating a stacked crystal filter, and showing an additional electronic device which can be created by a process similar to that employed to create the thin film resonator;
FIG. 3 is a block diagram illustrating the process steps employed in the present invention to produce thin film resonators; and
FIGS. 4a-4f sequentially illustrate the process steps for forming a thin film resonator exemplifying the present invention.
While the invention will be described in connection with preferred embodiments, there is no intent to limit the invention to those embodiments. On the contrary, the intent is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined in the appended claims.
Turning to the drawings, FIG. 1 shows a thin film resonator 19, in this instance a two terminal device. The device is based on a semiconductor substrate 14 which has upper 13 and lower 12 opposed surfaces, which are generally planar and parallel. A via 11 formed below the thin film resonator frees a membrane portion 15 for acoustic vibration so that the thin film resonator can operate in the fundamental mode.
Referring in greater detail to the thin film resonator 19, it can be seen that the device includes a lower metal electrode 16, and an upper metal electrode 18 sandwiching an intermediate thin film piezoelectric layer 17. The metal electrodes 16 and 18 as will be described in greater detail below, are typically thin film electrodes deposited as by sputtering or electron beam evaporation. It is important that the metallic layer forming metal electrode 16 be smooth, thin and continuous and provide a smooth surface for receiving a highly oriented thin film of piezoelectric material. The piezoelectric thin film layer 17 is deposited as by DC magnetron sputtering, following which the upper electrode 18 is deposited.
The thin film resonator is formed on the substrate at a time when the substrate is strong and capable of withstanding the various processes for formation of the foregoing elements. Having formed the thin film resonator, metallization for the contacts, and interconnections if desired, the partly formed device is then subjected to an etching step which removes all or at least a portion of the substrate materials from below the membrane portion of the thin film resonator. In accordance with the present invention, the etching step is adapted to selectively etch the pure silicon of the substrate, while being relatively nonreactive to the materials formed on the upper surface of the device, such as the metallization and the dielectric which are exposed on that upper surface. Thus, the process steps provide for a relatively non-fragile wafer during the numerous steps needed to deposit the dopant impurities, perform the lithographic steps, etching steps, sputtering steps and the like, then, late in the process, after the majority of the process steps are completed, etches away the necessary material to free the resonator, but accomplishes the etching step in such a way that the delicate and previously formed resonator is not damaged. The ability to accomplish that is particularly significant when one notes that the mass and size of the silicon which must be removed from below the resonator is orders of magnitude greater than the mass and size of the portions of the device which must be protected.
Turning to FIG. 2, there is shown a stacked crystal filter 25 employed as the thin film resonator, as well as an additional electronic device 45 on the upper surface 13 of the substrate 14. The stacked crystal filter includes a lower electrode 20 and a first piezoelectric thin film 21, an intermediate electrode 22, a second piezoelectric thin film 23, and an upper electrode 24. The piezoelectric films are typically about 5 microns thick in order to provide a resonator frequency response in the range of 1 GHz. The substrate is removed from beneath the central portion of the resonator, providing for free vibration of the resonator.
It is oftentimes desirable (although not easy to accomplish) to include electronic devices on the same substrate as the stacked crystal filter 25 of FIG. 2. For example, when it is desired to produce an integrated oscillator, both electronic components (transistors, etc.) and the resonator are desirably formed on the same substrate, and interconnected to produce an oscillator whose frequency is controlled by the stacked crystal filter. The process of the present invention is particularly amenable to formation of such devices because the electronic devices can be formed on the substrate prior to etching of the via which frees the membrane of the stacked crystal filter. In the FIG. 2 embodiment, the additional electronic devices are schematically represented at 45. The schematic representation encompasses electronic devices of various forms including those which would utilize ion implantation, diffusion, sputtering, other plating techniques, lithographic techniques, and the like, all commonly used in microelectronic fabrication for forming transistors, resistors, or other electronic devices. In accordance with the present invention, those processes can be performed on the semiconductor substrate prior to etching of the via 11. The etchant and etching process according to the present invention have been found to be selective to silicon in the presence of metallization and the like which are either normally present in or can be applied to electronic devices 45, so that the entire integrated device including stacked crystal filter and electronic components can be formed prior to accomplishing the etching step which produces the via 11 to complete the thin film resonator.
Turning to FIG. 3, there is illustrated the sequence of the process steps which will be set out in more detail below. FIG. 3 also shows the parallel sequences of processes employed by the invention. The processes include the preparation of the wafer, the formation of the thin film resonator on the wafer, the masking of the region to be etched, the etching of the wafer, and the cleaning and completion of the wafer, yielding the finished device. In parallel with these process steps are the preparation of the etchant and the preconditioning of the etchant, the preconditioning of the etchant being completed before the etching. It will be apparent from an examination of FIG. 3 that the etching step is one of the last steps involved in manufacturing the thin film resonator. It will also be apparent that the preconditioning of the etchant is an important step in the manufacturing process.
In greater detail, the process flow includes a wafer preparation step 100 which includes all of the standard cleaning and other preparatory steps performed on the raw wafer. Step 102 is a broad step which encompasses all the necessary techniques for forming of the thin film resonator and/or other electronic devices. Of course, the process step 102 does not include the etching which actually frees the membrane, but it preferably includes all of the deposition steps which form the resonator, as well as all of the deposition steps which form the electronic device and the interconnections between such devices. Passivating and metallizing layers can also be formed in the step 102.
There may be situations where it is desirable to perform one or more of the substeps which form the overall process step 102 at a stage later than the etching step. That aspect can also be included within the invention, realizing, however, that it is most desirable to perform most of the fabrication steps prior to the final etching step, since the final etching step substantially increases the susceptibility to damage of the device.
Having performed the process steps 102, a step 103 is performed to mask the via in the region to be etched. In a parallel process, the etchant had been prepared in a step 104 and preconditioned in a step 105. The mixing and preconditioning steps will be described in greater detail below. Suffice it to say, however, at the end of process step 105 the etchant is preconditioned and is at an appropriate temperature so that when a partly fabricated device including thin film resonators (and electronic components if present) is immersed into the etchant, etching of the silicon will proceed while the etchant will be ineffective to attack the metallization.
A step 106 represents the etching process itself, and after etching is complete, a step 107 is utilized to clean and complete the wafer to yield a finished device represented at 108.
Turning now to FIGS. 4a-4f, there are illustrated a sequence of process steps and the state of formation of the device as it progresses from step to step beginning with a raw semiconductor substrate through the manufacture of a thin film resonator. It will be appreciated that the process steps relate to formation of a single thin film resonator, in the present instance a stacked crystal filter which is a two port device, and is representative of a broader range of thin film resonators. Thus, while the masking will differ for formation of different devices, the sequence of process steps will remain substantially the same.
Sputter deposition using a DC magnetron is utilized to form the thin film resonator. Thus, in the exemplary process of FIG. 4, FIG. 4a illustrates the deposition of a first conductive layer or metallization layer 27 which, in that illustrated embodiment, serves as the lower electrode for the thin film resonator. Thus, it is seen that the layer 27 is deposited in a region 26 in which the thin film resonator will be formed. There is no need to pre-etch the wafer in region 26.
Having deposited the metallization layer 27, the metal is then covered with a photoresist, patterned and etched to form the metal layer into the desired pattern.
After the photoresist is stripped and the wafer cleaned of all residue (rinsed with acetone) from the device in the condition illustrated in FIG. 4a, the process proceeds to the stage illustrated in FIG. 4b which includes the formation of a thin film piezoelectric layer 28. The piezoelectric layer 28 is preferably of AlN deposited in an oriented film by DC magnetron sputtering. An available technique for patterning the AlN layer over the lower metallization 27 if desired is by sputtering through an aperture mask. However, in practicing the present invention, it is presently preferred to use a dielectric liftoff process for patterning of the AlN piezoelectric layer.
In utilizing the dielectric liftoff process, an initial layer, which will serve as a sacrificial layer in the dielectric liftoff process, is first deposited. It is currently preferred to utilize zinc oxide as the sacrificial layer and to deposit that material by sputter deposition using a DC magnetron. A zinc target is utilized in an oxygen plasma to deposit a ZnO layer, preferably about 5 microns in thickness, over the entire upper surface of the device. The zinc target is then removed and a silicon target put in its place to deposit about 1000 Å of silicon dioxide over the ZnO layer. A layer of photoresist is then spread over the silicon dioxide and photolithographically patterned to create windows in which the aluminum nitride is to be formed. The silicon dioxide is then etched, using a buffered hydrogen fluoride solution or a plasma etch technique. Following etching of the window in the silicon dioxide, the zinc oxide is then etched using citric acid. The double etching leaves a shelf of silicon dioxide over a cavity in the ZnO which exposes the aluminum below the zinc oxide layer.
Having thus opened windows over the aluminum in the areas in which the piezoelectric resonator material is to be deposited, the device is returned to the DC magnetron. Using a highly pure aluminum target (99.999% purity) in a nitrogen atmosphere, a very pure thin and smooth layer of aluminum nitride is deposited, approximately 2.5 microns in thickness.
After deposition of the aluminum nitride film, the wafer is then soaked in dilute citric acid which tends to dissolve the ZnO. That process is conventionally known as dielectric liftoff. In the present instance, the aluminum nitride in regions other than the window is removed, leaving the aluminum nitride thin film deposited over and in intimate contact with the aluminum in the region which had been defined by the window. The partially completed device at this stage is illustrated in FIG. 4b.
The device is then subjected to a further plating and photolithographic process for formation of an intermediate electrode 29. FIG. 4c shows the intermediate electrode 29 deposited over the aluminum nitride piezoelectric layer 28 and FIG. 4d shows the device after the formation of an additional piezoelectric layer 30, both layers being deposited by the processes previously described. FIG. 4e shows the device after the formation of the upper metallization 31.
The formation of the upper metallization layer 31 is preferably by a liftoff process. Having thus patterned and deposited the dielectric layer, the upper metallization is deposited by a suitable process such as electron beam evaporation. The wafer with deposited upper metallization is then soaked in a bath of acetone to dissolve the photoresist and lift off the metal in all but the desired areas. FIG. 4e illustrates the wafer at this stage and shows the thin film resonator.
In accordance with the present invention, the thin film resonator requires a membrane in the area 26; that membrane is formed by subsequent process steps which selectively remove the silicon substrate but do not attack the thin film resonator. FIG. 4f illustrates the patterning of an aperture 35 on the second surface 14 of the substrate 12 and the etching of that aperture in the area 26. It is seen that the etching proceeds until the lower aluminum layer 27 is reached, with the aluminum layer 27 serving as an etchant stop to define a thin membrane 38 comprising the metallization layers and intermediate aluminum nitride film forming the resonating device of the thin film resonator. It will be appreciated by those skilled in the art that the drawings are not to scale, and that the individual layers 27-31 which make up the thin film resonator are on the order of only several microns in thickness, whereas the substrate 12 is substantially more than an order of magnitude thicker than the combined layers which form the resonator.
It can be seen that the process illustrated in FIGS. 4a-4f is not limited to the formation of thin film resonators, but can be employed for the formation of any electronic device on a silicon substrate which must be etched without damage to the electronic device. The process described above can be employed, for example, to produce a device such as that shown in FIG. 2. FIG. 2 shows an electronic device 45 deposited on the same substrate as a stacked crystal filter 25. The formation of the stacked crystal 25 filter requires the etching of the substrate 12. The process employed by the invention can be employed to fabricate the electronic device 45 on the substrate 12 with the stacked crystal filter 25 before the etching step. The etching required for completion of the stacked crystal filter 25 will not damage the electronic device 45. Further details of the etching process will be provided below (as well as additional detail on the sputtering of the piezoelectric film) to better illustrate the practice of the present invention.
As noted above, the aluminum nitride film is a highly oriented and very pure film formed by sputter deposition. In forming that film, it has been found desirable to utilize specialized techniques to account for the relatively long deposition times which are required. Those techniques involve utilization of a DC magnetron reactive sputtering system which in one implementation uses an 1800 watt, 600 volt DC power supply as the current source. Typical operating parameters are 3 mTorr pressure, 0.75 amp current with a voltage drop across the nitrogen plasma of about 350 volts. The semiconductor substrate is positioned opposite a very pure (99.999%) aluminum target. A ring positioned between the substrate and target acts as an anode to assist in containing and stabilizing the nitrogen plasma. The ring typically has a potential of about 60 volts. The plasma contains a large number of positively charged ions which accelerate into the target, knocking loose atoms of aluminum. The aluminum atoms then traverse the chamber and deposit on available surfaces. When being deposited in the presence of a reactive gas such as nitrogen, the aluminum atoms will form compounds, in the present instance aluminum nitride.
As noted above, the aluminum nitride films are preferably a total of about 5 microns in thickness in order to provide resonator response at about 1 GHz. At optimum deposition parameters, approximately 90 minutes of deposition are required. In addition, the crystal grain growth must be oriented in order to provide good piezoelectric response.
Using those relatively long deposition times, the chamber of the magnetron becomes electrically insulated, which can result in impurities being dislodged from the chamber and deposited in the aluminum nitride film forming on the semiconductor substrate.
As set forth in copending, commonly assigned U.S. patent application Ser. No. 07/813,101, filed Dec. 23, 1991, now U.S. Pat. No. 5,232,571, entitled "Aluminum Nitride Deposition Using A AlN/Al Sputter Cycle Technique", during the relatively lengthy deposition procedure, a layer of aluminum metal is periodically deposited over the aluminum nitride buildup on the chamber to prevent contamination of the AlN film being deposited on the semiconductor substrate. This is accomplished by changing the reactive gas in the chamber to argon in place of the nitrogen for a brief period. To prevent the wafer from being coated with the aluminum during this periodic "cleansing" process, a shutter is moved into place over the substrate to act as a shield. Thus, at periodic intervals, such as about 30 minutes, during the deposition of the aluminum nitride, the shutter is closed and the nitrogen atmosphere replaced with argon, to coat the walls and other elements of the reactor with an aluminum film. The argon is then removed and the nitrogen atmosphere returned, following which the shutter is opened and aluminum nitride deposition continued, until the required thickness has been built up. The alternating of AlN and Al deposition (with shutter closed during Al deposition) is repeated until the required amount of AlN has been deposited onto the semiconductor substrate. This procedure has been found to produce substantially purer films than has been available using conventional sputtering techniques.
In the process description of FIGS. 4a-4f, particular mention was made of the selective etching step for removing substrate material from below the membrane of the thin film resonator, and also the process step for dielectric liftoff in connection with patterning the dielectric layer of the thin film resonator. Additional information will now be given on those two process steps.
In removing substrate material from below the membrane of the thin film resonator, an anisotropic etching process is employed which etches along the (100) crystal axes but not along the (111) crystal axes from the rear surface 26, with the first metal layer 27 serving as an etchant stop. The rear surface 26 of the substrate is masked by suitable materials such as a silicon dioxide layer appropriately patterned using standard techniques to form windows in the areas where the membrane is to be formed. The windows can be aligned with the devices formed on the upper surface 13 as by using infrared alignment techniques.
The etching solution which has been found to be selective to silicon while substantially nonreactive to the aluminum nitride and aluminum metallization is an aqueous solution of hydrazine and quinoxaline preprocessed as will be described below. A desirable solution consists of proportions comprising approximately 850 milliliters of hydrazine hydrate (85 weight percent solution), 650 milliliters of deionized water, and approximately 1 gram of quinoxaline which has been vacuum distilled to remove oxide contamination. The quantity of quinoxaline present is insufficient to cause the quinoxaline to act as a chelating agent. The solution is heated to a reaction temperature of about 108 boiling point.
In accordance with the present invention, the solution is then preprocessed to render it selective to silicon. Once the reactor is at temperature, preprocessing is commenced by immersing a silicon wafer for a short interval, approximately 5 minutes, for example. The immersion of the wafer introduces atomic silicon into the solution in a quantity sufficient to render the etchant selective to silicon. The wafer is then removed and the solution is allowed to precondition for a period, preferably at least 30 minutes. Although the length of the preconditioning is not critical, the preconditioning is necessary to render the solution selective to silicon. The length of the interval of preconditioning is not limited to 30 minutes, and indeed once a solution is employed etch integrated devices on silicon, the preconditioning indeed can extend in time for substantially beyond 30 minutes with the solution remaining selective to silicon.
Having preconditioned the etching solution by treatment with silicon and aging, wafers of the type illustrated in FIG. 4e are then immersed in the heated solution for etching. The solution is selective to silicon and thus will remove the silicon substrate in the area 26 defined by the windows while not attacking the metallization or dielectric layers on the upper surface of the device. In some cases, it may be desirable to passivate the upper surface of the wafer with a material such as silicon dioxide which is not reactive to the etchant. When etching is completed, as will be determined when the etching reaches the aluminum layer 27 to which the etchant is nonreactive, thus serving as an etchant stop, the wafer is then removed from the etchant solution, rinsed with deionized water and dried, such as in a stream of nitrogen gas.
The significance of the foregoing etchant process will be appreciated in that it provides a mechanism for allowing formation of both the semiconductor device and the thin film resonator on wafers which can be readily handled in the ordinary semiconductor fabrication process flow, followed by a subsequent etching step for formation of the thin film resonator membrane by a selective etching process which removes the silicon to form the membrane without attacking the elements previously put in place which make up the devices. Indeed, since the materials of the resonator are nonreactive to the etchant, they can be exposed to the etchant for a long enough time to assure that all undesired materials are removed (about 3-4 hours). This aspect of the invention substantially lessens the time and temperature criticality of the etching process.
The process steps involved in the formation of the thin film resonator are adapted for forming high quality resonators and freeing the membrane for vibration, without the need for the creation of a p.sup.+ layer, and allowing the exposure of the device to the etchant without danger of damage to the device.
Moreover, the invention has broader applications than the production of thin film resonators. The process steps employed by the invention can be used to fabricate any electronic device requiring the deposition of a patterned aluminum layer on a silicon substrate and the subsequent etching of the substrate. The invention allows the etching to proceed without any danger of damage to the device, or any need to take steps to protect the device from damage by the etchant.
Citations de brevets
Citations hors brevets | <urn:uuid:13c3dcbb-93e7-4557-8b1a-2547a6a04bb7> | {
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The correlation of structure and electronic properties near the surface of transition metal oxides
The strong couplings between different degrees of freedom are believed to be responsible for novel and complex phenomena discovered in transition metal oxides (TMOs). The physical complexity is directly responsible for their tunability. Creating surfaces/interfaces add an additional ' man-made' twist, approaching the quantum phenomena of correlated materials. ^ The dissertation focused on the structural and electronic properties in proximity of surface of three prototype TMO compounds by using three complementary techniques: scanning tunneling microscopy, angle-resolved photoelectron spectroscopy and low energy electron diffraction, particularly emphasized the effects of broken symmetry and imperfections like defects on the coupling between charge and lattice degrees of freedom. ^ Ca1.5Sr0.5RuO4 is a layered ruthenate with square lattice and at the boundary of magnetic/orbital instability in Ca2-xSrxRuO4. That the substitution of Sr 2+ with Ca2+ causing RuO6 rotation narrows the dxy band width and changes the Fermi surface topology. Particularly, the γ(dxy) Fermi surface sheet exhibited hole-like in Ca1.5Sr0.5RuO4 in contrast to electron-like in Sr2RuO4, showing a strong charge-lattice coupling. ^ Na0.75CoO2 is a layered cobaltite with triangular lattice exhibiting extraordinary thermoelectric properties. The well-ordered CoO2-terminated surface with random Na distribution was observed. However, lattice constants of the surface are smaller than that in bulk. The surface density of states (DOS) showed strong temperature dependence. Especially, an unusual shift of the minimum DOS occurs below 230 K, clearly indicating a local charging effect on the surface. ^ Cd2Re2O7 is the first known pyrochlore oxide superconductor (Tc ∼ 1K). It exhibited an unusual second-order phase transition occurring at TS1 = 200 K and a controversial first-order transition at TS2 = 120 K. While bulk properties display large anomalies at TS1 but rather subtle and sample-dependent changes at TS2, the surface DOS near the EF show no change at T s1 but a substantial increase below TS2---a complete reversal as the signature for the transitions. We argued that crystal imperfections, mainly defects, which were considerably enhanced at the surface, resulted in the transition at TS2. ^
Physics, Electricity and Magnetism|Physics, Condensed Matter
"The correlation of structure and electronic properties near the surface of transition metal oxides"
(January 1, 2005).
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A comprehensive supervisor control for a hybrid system that comprises wind and photovoltaic generation subsystems, a battery bank, and an ac load is developed in this paper. The objectives of the supervisor control are, primarily, to satisfy the load power demand and, second, to maintain the state of charge of the battery bank to prevent blackout and to extend the life of the batteries. For these purposes, the supervisor controller determines online the operation mode of both generation subsystems, switching from power regulation to maximum power conversion. Decision criteria for the supervisor based on measurable system variables are presented. Finally, the performance of the supervisor controller is extensively assessed through computer simulation using a comprehensive nonlinear model of the plant.
Date of Publication: June 2005 | <urn:uuid:e7f28091-a3c9-43ca-8e22-642280c4fdf7> | {
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Wilson, Bruce, Messac, Achille, Northeastern University, Department of Mechanical Industrial and Manufacturing Engineering
During tests at the Cape Cod Canal, the structure that housed a single helical turbine was found to be inefficient. This paper discusses problems encountered during previous tests, conceptual designs to eliminate these problems, and an analysis of a design for a final prototype structure. This paper further discusses the manufacturing of a prototype support structure. This paper concludes with a detailed description and manufacturing process of the prototype which will be tested by June 1997.
prototype, helical turbine
Northeastern University, Department of Mechanical Industrial and Manufacturing Engineering
Barnes, Terrence; Holley, Steven; Hussin, Faiz; Melloy, Richard; and Tsui, Eric, "Design and Construction of a Helical Turbin Support Structure" (2007). Capstone Design Program: Mechanical Engineering. Paper 26. http://hdl.handle.net/2047/d1001035x
Click button above to open, or right-click to save.COinS | <urn:uuid:f39acb01-d64f-4d76-ad97-e027c532437c> | {
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Francis, G. and Holloway, J.
Beyond comparisons the role for the operational researcher in benchmarking.
Journal of the Operational Research Society, 53(3),
This paper explores the possible roles for the operational researcher in best practice benchmarking. It describes the range of activities which are carried out in the name of benchmarking, locates this approach in the broader context of performance improvement, and notes some critical concerns including the need to adopt a contingency approach to performance improvement. The paper concludes by encouraging operational researchers to contribute their professional skills to enhance the effectiveness of benchmarking.
||benchmarking; performance management; performance measurement; practice of OR
||Open University Business School
||17 Sep 2007
||02 Dec 2010 20:03
Actions (login may be required) | <urn:uuid:ad8c4373-31c0-45f0-be8f-4473582260b0> | {
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Porter Cable Clipped Head Framing Stick Nail
Clipped head, 34 deg. angled stick nails. Ideal for framing, subflooring, wall sheathing, and roof decking. For use in Porter Cable model No. FC350, FC350A Senco model No. SN325+, SN2, SN2+, SN3, SN4, SN70, Paslode model No. 5K-312, 5300, 5325, 5350, Impulse model No. 300, 325, 350, Hitachi model No. NR-83AA, Fasco model No. F-5C-HHN31-83, F6-HHN31-90, and Stan-Tech model No. SDN11PT-1. | <urn:uuid:ac27d4b8-10be-4ec9-a24b-880e075595b9> | {
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Enabling heterogeneous hardware acceleration using novel programming and scheduling models
ENHANCE aims on a better integration and simplified usage of heterogeneous computing resources within current and upcoming computing systems.
Heterogeneous systems contain multiple compute components like multi-core processors, complemented by graphics processing units (GPUs) and/or field programmable gate arrays (FPGAs). Employing such hardware architectures raises several challenges in programmability, performance estimation and scheduling that are approached within the ENHANCE project and shall result in a framework enabling the development and use of applications on heterogeneous systems. The benefit of the developed methods for the industrial application partners is of special importance.
Sebastian Dreßler, Thomas Steinke
04/2011 - 10/2013
Parallel and Distributed Systems | <urn:uuid:f99ed5b0-7581-4144-bed7-f896c4d23cfb> | {
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Skip to Main Content
This letter reports a novel methodology for the orientation-specific parallel heterogeneous integration of parts of various sizes. Assembly sites are designed to only attract specific parts from an unsorted pool using the combined effect of Faraday waves and magnetic forces, achieving one-to-one part-to-site registration. We demonstrate the assembly of two types of thin parts (2000 × 2000 × 100 and 4000 × 4000 × 100 μm3) onto the same substrate through a one-step process. Statistical analysis of the distributions of magnetic forces delimits the suitable range for the strength of Faraday waves to fix nonoptimal initial placements and orientations.
Date of Publication: Dec. 2012 | <urn:uuid:1cddf188-8039-4b00-b011-b055482db26d> | {
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Matted or felted sheet, usually made of cellulose fibres, formed on a wire screen from water suspension. Source materials include wood pulp, rags, and recycled paper. The fibres are separated (by processes that may be mechanical, chemical, or both) and wetted to produce paper pulp, or stock. The pulp is filtered on a woven screen to form a sheet of fibre, which is pressed and compacted to squeeze out most of the water. The remaining water is removed by evaporation, and the dry sheet is further compressed and often (depending on the intended use) coated or infused with other substances. Types of paper in common use include bond paper, book paper, bristol (or bristol board), groundwood and newsprint, kraft paper, paperboard, and sanitary paper (for towels, napkins, etc.). See alsocalendering; Fourdrinier machine; kraft process. | <urn:uuid:d571ab4f-41ab-4e0c-9d3d-40c47e94395a> | {
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These compactors were engineered to densify materials by applying pressure or by combining pressure with heat, binding agents, or moisture. Available in heavy- and severe-duty versions, the easily maintained units are versatile and energy-efficient systems for compacting, densifying, or briquetting material to the size, shape, and density required. They also ensure the solubility and friability needed in the process. These processing capabilities are used to improve flowability, solubility, dust control, and waste by-product recovery. In addition, the units not only reduce storage requirements, but also lower transportation and product-handling costs. The process utilizes counterrotating rolls to densify materials with the application of pressure. Material is transported into the nip area between the rolls by a single or intermeshing multiple screw feeder. Compression is achieved as the volume of material entering the nip area is squeezed through the rolls.
Prater-Sterling, Bolingbrook, IL 630-759-9595 www.prater-sterling.com
Mixer, Blender, and Agglomerator
The Extrud-O-Mix is often used to mix and blend dry powders and liquids into a paste or dough-like consistency. The unit then extrudes the mixture into free-flowing, dust-free pellets or particles. Dispersibility of the finished particles is excellent because, unlike high-pressure designs, the unit uses only the minimum force necessary to maintain particle integrity. The design is energy efficient, easy to clean, and simple to maintain. Features include adjustable shear input and heat transfer capabilities in the rotor and housing. Typical applications include detergent formulations, adhesives, sugars, and sugar blends.
Bepex International, Minneapolis, MN 612-627-1406 www.bepex.com | <urn:uuid:e53fe081-f22f-4999-b351-882da14963d8> | {
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"url": "http://www.powderbulksolids.com/article/agglomeration-spotlight-may-09"
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Roger Azevedo, Amy Witherspoon
Self-regulated learning (SRL) involves a complex set of interactions between cognitive, metacognitive, motivational and affective processes. The key to understanding the influence of these self-regulatory processes on learning with open-ended, non-linear learning computer-based environments involves detecting, capturing, identifying, and classifying these processes as they temporally unfold during learning. Understanding the complex nature of the processes is key to building intelligent learning environments that adapt to learners’ fluctuations in their SRL processes and emerging understanding of the topic of domain. The foci of this paper are to: (1) introduce the complexity of SRL with hypermedia, (2) briefly present an information processing theory (IPT) of SRL and using it to analyze the temporally, unfolding sequences of processes during learning, (3) present and describe sample data to illustrate the nature and complexity of these processes, and (4) present challenges for future research that combine several techniques and methods to design intelligent learning environments that trace, model, and foster SRL.
Submitted: Sep 11, 2008 | <urn:uuid:22665817-3f87-49fd-9b19-31e1f46a056d> | {
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Ali, Rusmidah (2006) Photodegradation of new methylene blue N in aqueous solution using zinc oxide titanium dioxide as catalyst. Jurnal Teknologi F (45F). pp. 31-42. ISSN 0127-9696
- Published Version
Official URL: http://www.penerbit.utm.my/onlinejournal/45/F/JT45...
In this study, ZnO and TiO2 are used as photocatalyst to degrade the dye, New Methylene Blue N. The photodegradation rate was measured using UV-Visible spectrophotometer. New Methylene Blue N showed the absorption values at λ=590 nm and λ=286 nm. UV lamp (λ=354 nm) is used in the photodegradation process. Results showed that ZnO is a better catalyst compared to TiO2. The degradation by ZnO showed TiO2 gave 81 % at λ=590 nm and 77.75 % at λ=286 nm. In contratst, the degradation for TiO2 was 25.68 % at λ=590 nm and 26.37 % at λ=286 nm. Percent degradation for New Methylene Blue N is 88.89 % and 68.94 % at λ=590 nm and λ=286 nm respectively when H2O2 was added. The mixture of ZnO and TiO2 in the ratio of 85: 15 (0.085 g: 0.015 g) is the most optimum mixture of photocatalyst with the degradation percentage of 96.97 % and 93.61 % at λ=590 nm and λ=286 nm. The addition of Cu2+ metal ion gave the highest percentage of degradation (83.83 % at λ=590 nm) compared to other metal ions. The addition of Pb2+ gave the highest percentage of degradation at λ= 286 nm with 81.25 %. The optimum condition was achieved at pH 5.90, which gave the highest percentage of degradation, 92.84 % and 89.30 % at λ=590 nm and λ=286 nm respectively.
|Uncontrolled Keywords:||New methylene blue N, photodegradation|
|Subjects:||Q Science > QD Chemistry|
|Divisions:||Chemical and Natural Resources Engineering (Formerly known)|
|Deposited By:||Assoc. Prof. Dr. Rusmidah Ali|
|Deposited On:||20 Jun 2007 01:00|
|Last Modified:||09 Nov 2010 09:54|
Repository Staff Only: item control page | <urn:uuid:3910cdac-3b47-4f97-90b5-cee00e570a54> | {
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| || Numerical Analysis on Protecting Performance of Layered Arch Structures Subjected to Blast Loading
Author : Yongxiang, Dong ;Changjing, Xia;Shunshan, Feng ;Zhiyu, Shao
Source : Defence Science Journal ; Vol:59(2) ; 2009 ; pp 131-136
Subject : 620.1 Material Science and Technology
Keywords : Layered arch structure;Underground structures;Blast resistance;Protective performance;Numerical analysis
Abstract : Dynamic responses of layered arch structure composed of different materials subjected to blast loading are analysed by numerical simulation. The deflection, the particle velocity and the particle acceleration of the arch inwall and stress curves versus time are obtained comparing properties of blast resistance of different arch structures with the same amount of charge. The results show that the arch structure composed of foam concrete-SFRC-steel has good blast resistance. Furthermore, the dynamic performance of the foam concrete- SFRC-steel composite structures is studied with different amount of charge. Additionally, coupling relationship of blast resistance and explosion charge is analysed. Comparison of numerical results with experimental results, show that they are in good agreement. This numerical analysis may provide important guidance for blastresistant design and analysis of underground structures. | <urn:uuid:7062cf1c-84f0-4585-82fc-d9e25aa11108> | {
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} |
|Type of Publication:||Article|
PT: J; TC: 14; UT: WOS:000272846000017
We demonstrate the use of hydrogel swelling as a mechanism to reversibly induce solvatochromic shifting in single-walled carbon nanotube (SWNT) near-infrared emission within a biocompatible hydrogel. The optical sensor reports the degree of the swelled state and glucose concentration when apo-glucose oxidase is used to cross-link the hydrogel, Photoluminescence emission maxima from dispersed nanotubes in a poly(vinyl alcohol) hydrogel shift as cross-linking is increased, with a maximum of -48 meV for the (6,5) nanotube. The Raman tangential mode also red shifts up to 17 cm(-1), indicative of nanotube lattice strain equivalent to an effective hydrostatic pressure of 3 GPa. While the electronic band gaps of SWNTs are known to either increase or decrease with uniaxial strain or lattice deformation depending on chiral vector, we show that the mechanism of detection is counterintuitively non-strain-dependent. Instead, the data are well-described by a model that accounts for changes in dielectric screening of the 1-D exciton, as the osmotic pressure forces conformational distortions in the PVA by rotating more polar groups to the nanotube surface. The model describes observed changes with hydration state and cross-linking density variation from 0 to 14%. Cross-linking with apo-glucose oxidase renders the hydrogel glucose responsive, and we demonstrate rapid and reversible detection of glucose from these systems after repeated cycling of 10 mM glucose. We also demonstrate detection and imaging in the near-infrared of implanted hydrogel sensors in a mouse tissue model, showing excellent signal-to-noise of 8.6 and contrast with integration times of 60 s.
© Strano Research Group | <urn:uuid:4af7fc02-b5e4-4763-9a32-1efbf83be1e4> | {
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This study proposes a fuzzy sets approach for estimating irrigation efficiency of limited water resource area. Genetic algorithm technique was applied to calibrate membership function condition of fuzzy sets model. The proposed model considered the total available water resource and the farmer participation of water resource management as the input variables. The approach model was applied to determine the irrigation efficiency of the Nong Wei Irrigation Project (in the Northeast region of Thailand). Results showed that the fuzzy sets model can be used to estimate the irrigation efficiencies, given the total available water resources and the farmer participation. Furthermore, the results indicated that the farmer participation in water resource management can be calculated via the proportion of seasonal required-area and the overall land area of the irrigation project. | <urn:uuid:096af966-7c8d-43da-84d2-b974b48b2db1> | {
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Minimization of Load Based Resources in Cloud Computing Systems
Cloud computing is a term, which involves virtualization, distributed computing, networking, software and Web services. The authors' objective is to develop an effective load balancing algorithm using Divisible Load Scheduling Theorem to maximize or minimize different performance parameters (throughput, latency for example) for the clouds of different sizes. Central to these issues lays the establishment of an efficient load balancing algorithm. The load can be CPU load, memory capacity, delay or network load. Load balancing is the process of distributing the load among various nodes of a distributed system to improve both resource utilization and job response time while also avoiding a situation where some of the nodes are heavily loaded while other nodes are idle or doing very little work. | <urn:uuid:62b883ea-e99c-4880-bf51-24cf80b1f3d0> | {
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Inorganic borohydrides are promising compounds for hydrogen storage applications. In this context, there is a need to analyze and understand fundamental structural and dynamic properties of these compounds and their reaction products.
In our research, we synthesize new compounds and, in collaboration with R. Cerny (Lab. Cristallography, Geneva), obtain structural characterizations.
Theoretical DFT calculations and vibrational spectra are also performed and combined with the structural analysis.
Temperature dependent vibrational studies give insight into dynamical properties of the borohydride ion in the crystal.
Current experiments are also directed towards isotope exchange reactions.
This research includes also experiments on samples prepared by collegues in Germany, Denmark and the US.
I. Lindemann, R. Domènech Ferrer, L. Dunsch, Y. Filinchuk, H. Hagemann, V. D'Anna, R. Cerny, L.M. Daku Lawson, L. Schulz and O. Gutfleisch,
Chem. Eur. J. 16, 2010 , 8707-8712 | <urn:uuid:7529fa3a-5cd2-406b-868b-0c98132a5cc7> | {
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The Christian Doppler (CD) Research Association funds application-oriented basic research in laboratories with industry partners, who seek effective access to new knowledge. Partners in the CD-Lab CDL-Flex are institutes at the Vienna University of Technology in the areas of software technology and automation engineering as well as the industry partners logi.cals and Certicon in the application area of industrial automation systems.
The increasing complexity and flexibility of engineering processes for developing modern software-intensive systems require the systematic integration of software tools across engineering disciplines (such as mechanical, electrical, and software engineering). Technical and semantic gaps between software tools and engineering models in the development of automation systems hinder the correct and efficient communication across tool and system boundaries, leading to development delays and risks for system operation. The development of automation systems and also business software development is a group effort of engineering teams that are typically working at distributed locations. The integration of communication and collaboration tools into modern agile engineering workflows is therefore a particularly relevant goal.
- technical integration of software tools and
- semantic integration of knowledge models across engineering disciplines.
This foundation enables quality management across engineering models and tools. We investigate concrete initial research scenarios to demonstrate challenges and advances:
- Change/version management across engineering models in several tools
- Engineering process automation, analysis, and reporting.
- Flexible integration of a range of SCADA systems and simulators that predict run-time events.
- Early defect detection by enabling the “end-to-end test” across engineering models: from the sensors in the field to the associated variables in control software programs.
A key result is a technical integration platform for software tools, the „Engineering Service Bus“, which will be made available to scientists and practitioners as Open Source Software. The Engineering Service Bus (EngSB) applies successful concepts of the Enterprise Service Bus in business software engineering to software tools in the engineering process. The integration approach is vendor neutral and allows the integration of existing tools in an engineering environment.
To ensure the relevance of the research in the CD-Lab for practice, we work with industry application partners who provide use cases and evaluate research prototypes developed in cooperation with the CD-Lab. As starting point we conduct workshops for interested practitioners starting in February 2010. For more detailed information on these workshops please contact Stefan Biffl.
To get an overview on the challenges of the lab and current research activities also check out the videos section | <urn:uuid:65cead4a-5e4b-4604-8c2f-5f990b2d8cef> | {
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Quantifying the end-to-end delay performance in multihop wireless networks is a well-known challenging problem. In this paper, we propose a new joint congestion control and scheduling algorithm for multihop wireless networks with fixedroute flows operated under a general interference model with interference degree K. Our proposed algorithm not only achieves a provable throughput guarantee (which is close to at least 1=K of the system capacity region), but also leads to explicit upper bounds on the end-to-end delay of every flow. Our end-to-end delay- and throughput-bounds are in simple and closed forms, and they explicitly quantify the tradeoff between throughput and delay of every flow. Further, the per-flow end-to-end delay bound increases linearly with the number of hops that the flow passes through, which is order-optimal with respect to the number of hops. Unlike traditional solutions based on the backpressure algorithm, our proposed algorithm combines windowbased flow control with a new rate-based distributed scheduling algorithm. A key contribution of our work is to use a novel stochastic dominance approach to bound the corresponding perflow throughput and delay, which otherwise are often intractable in these types of systems. Our proposed algorithm is fully distributed and requires a low per-node complexity that does not increase with the network size. Hence, it can be easily implemented in practice.
Window-based flow control, rate-based scheduling algorithms, low-complexity and distributed algorithms, supermodular ordering, order-optimal delay bound
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The Manufacturing and Mechanical Engineering Technology (MMET) Program prepares students for a dynamic career in industry. Upon graduation, the MMET graduate is:
1. Prepared to swiftly master the company's technologies, systems and organization.
2. Versatile and effective in diverse areas that require understanding of the dependencies among material properties, product design, costs, and manufacturing systems and process technologies.
3. Able to view manufacturing from a global enterprise and system perspective, recognize the importance of customer and supplier interactions. | <urn:uuid:c2069805-787f-424a-9633-67dfc48fc939> | {
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Skip to Main Content
A temperature of 200degC for the PN junction of power silicon devices (diodes, thyristors, transistors) is known as a limit for their reliable performance. PN junction failure after operation above this temperature consists in excessive high current or even electrical short circuit when reverse bias voltage is applied. Enough information in the published literature on this subject does not exist at this time. PN junction devices available at this time on the market were measured and placed in a hot chamber at constant ambient temperature higher than 200degC. Junction blocking voltage was applied and the level of leakage current was monitored. The silicon die after decapsulation of failed devices exhibits a small region of material degradation located at the junction periphery, causing excessive high leakage or short-circuit of the junction. The leakage current flowing at the interface between semiconductor and the passivating dielectric layer from the junction edge is a key factor involved in device failure. Lower level and uniform distribution of this current around the junction periphery can enable reliable operation above 200degC. Experimental results are presented and analyzed.
Date of Conference: 16-18 April 2007 | <urn:uuid:ad3a2797-d582-4f25-ac4b-6facd76350fd> | {
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Skip to Main Content
Vibratory force sensors are fabricated using piezoelectric capacitors on microcantilever structures for triaxial sensitivity by the individual sensor element. The cantilevers have been formed into a 3-D curved shape by controlling residual stress combination of the multilayered structure. Triaxial tactile sensitivity of the cantilever sensor is analyzed under a tactile load application onto the surface of an elastomer in which the cantilever is embedded, mimicking human skin structure. The cantilever is converse-piezoelectrically excited by an external ac voltage and three resonant modes are developed to detect the applied load vector components by the single sensor element. Resonant frequency shifts of each mode are investigated upon load applications. The results show that the frequencies vary to the three axial tactile loads independently and they can be superposed with corresponding to the superposition of the load components. The applied load vectors are estimated by resonant frequencies of the single cantilever sensor with compensating nonlinearities of the sensor response. The estimated error is less than 1.1% to the full scale of the load ±4 kPa.
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Simultaneous analysis of ion and electron heat transport by power modulation in JET
Ryter, F., Angioni, C., Giroud, C., Peeters, A. G., Biewer, T., Bilato, R., Joffrin, E., Johnson, T., Leggate, H., Lerche, E., Madison, G., Mantica, P., Van Eester, D. and Voitsekhovitch, I.. (2011) Simultaneous analysis of ion and electron heat transport by power modulation in JET. Nuclear Fusion, Vol.51 (No.11). Article: 113016. ISSN 0029-5515Full text not available from this repository.
Official URL: http://dx.doi.org/10.1088/0029-5515/51/11/113016
Heating power modulation experiments using ion cyclotron resonance heating (ICRH) in the (3)He minority scheme have been performed in the JET tokamak to investigate heat transport properties. This RF scheme provides a dominant localized ion heating, but also some electron heating, and therefore both ion and electron heat channels were modulated. This allows us to carry out a simultaneous transport analysis of ion and electron heat transport channels, including transient transport phenomena. This also provides an experimental assessment of the ICRH heat sources of the (3)He scheme. The modulation approach, so far widely used for electron transport studies, has been validated for ion heat transport in these experiments and yields results on stiffness and threshold of the ion temperature gradient (ITG)-driven ion heat transport. The results for the electron channel demonstrate the importance of the ITG-driven, off-diagonal, contribution to electron heat transport in plasmas with significant ion heating.
|Item Type:||Journal Article|
|Subjects:||Q Science > QC Physics|
|Divisions:||Faculty of Science > Physics|
|Journal or Publication Title:||Nuclear Fusion|
|Publisher:||Institute of Physics Publishing Ltd.|
|Page Range:||Article: 113016|
|Access rights to Published version:||Restricted or Subscription Access|
|Funder:||Euratom-IPP Association, European Fusion Development Agreement|
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Compound Semiconductor Manufacturing
Brewer Science is a proven leader in the microelectronics industry, demonstrated by industry-changing innovations such as ARC® technology and the ZoneBOND® thin wafer handling system. Top semiconductor companies rely on our in-depth expertise in materials science, chemistry, physics, optics, and modeling to strengthen their competitive edge, increase yield, and reduce operational costs.
We design and manufacture a broad range of specialty materials and wafer-processing equipment to enable multiple processes used in the creation of compound III-V semiconductor devices.
Spin-applied materials that level the surfaces of processed wafers | <urn:uuid:3ee4eeef-b4d2-43ca-a8d2-c4f438babe99> | {
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Nanoimprint lithography (NIL) is a paradigm-shift method that has shown sub-10-nm resolution, high throughput, and low cost. To make NIL a next-generation lithography tool to replace conventional lithography, one must demonstrate the needed overlay accuracy in multilayer NIL, large-area uniformity, and low defect density. Here, we present the fabrication of 60-nm channel metal–oxide–semiconductor field-effect transistors on whole 4-in. wafers using NIL at all lithography levels. The nanotransistors exhibit excellent operational characteristics across the wafer. The statistics from consecutive multiwafer processing show an average overlay accuracy of 500 nm over the entire 4-in. wafer. The accuracy is much better when the field size is reduced. The overlay accuracies are limited by the current alignment method and can be improved substantially. The work presents a significant advance in nanoimprint development and its applications in manufacturing of integrated electrical, optical, chemical, and biological nanocircuits. © 2003 American Institute of Physics. | <urn:uuid:a2694a89-b2c7-4949-a7a5-b4937508333a> | {
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Date of this Version
Cobalt (Co) composition has detrimental effects on the deposition of diamond films on cemented tungsten carbide (WC-Co) substrates. It decreases adhesion of the deposited films to the substrates and causes a transformation of sp3-bonded diamond to sp2-bonded graphite. In this study, a KrF excimer laser with a wavelength of 248 nm, a pulse width of 23 ns, and a pulse energy range of 84–450 mJ was used in the combustion-flame method to improve the quality of the deposited diamond films. Scanning electron microscopy, energy dispersive x-ray analysis, and Raman spectroscopy of the deposited films showed that a laser irradiation during combustion-flame deposition of diamond decreased the cobalt composition drastically. Based on the experimental results, the influence of the laser irradiation on the deposition process was analyzed. | <urn:uuid:8e57d11a-a461-4628-a782-8110e0be28e7> | {
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The mechanical properties of continuous-fiber-reinforced carbon matrix composites and relationships to constituent properties
Heredia, Fernando E., Spearing, S. Mark, Evans, Anthony G., Mosher, Paul and Curtin, William A. (1992) The mechanical properties of continuous-fiber-reinforced carbon matrix composites and relationships to constituent properties. Journal of American Ceramic Society, 75, (11), 3017-3025. (doi:10.1111/j.1151-2916.1992.tb04381.x).
Full text not available from this repository.
The tensile properties of three carbon matrix composites reinforced with SiC (Nicalon) fibers (materials A, B, C) have been measured with and without notches. One of the three materials (material B) had a relatively low strength and exhibited notch brittleness. This material had both a high interface sliding stress and a low fiber bundle strength, caused by particulates in the matrix. These characteristics have been shown to result in a change in failure mechanism that leads to the inferior properties exhibited by material B. The notch properties of the higher-toughness materials were shown to involve splitting, which alleviates the notch stress concentration and diminishes the notch sensitivity.
|Subjects:||T Technology > TA Engineering (General). Civil engineering (General)|
|Divisions:||University Structure - Pre August 2011 > School of Engineering Sciences
|Date Deposited:||30 Jan 2007|
|Last Modified:||01 Jun 2011 11:11|
|Contributors:||Heredia, Fernando E. (Author)
Spearing, S. Mark (Author)
Evans, Anthony G. (Author)
Mosher, Paul (Author)
Curtin, William A. (Author)
|RDF:||RDF+N-Triples, RDF+N3, RDF+XML, Browse.|
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PublicaHier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.
Simulating micro-electromechanical systems
Modeling micro-electronicmechanical devices with a system of algeraic and non-linear (partial) differential equations, as opposed to ordinary differential equations, simplifies the simulation process and eliminates simulator coupling problems. In this article, we automate the modeling of mechanical parts with electronic devices using MeXeL, which translates the system of equations to Spice-3-netlists. In this way, difficulties caused by coupling different simulators are eliminated. Here, we show the suitability of such a method by dynamically simulating a deformable mirror device (DMD) and its controlling circuit. | <urn:uuid:141429ad-7054-4a63-ab23-5b04ca391bbb> | {
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Dong Yu and Li Deng
Recently we have developed a novel type of structure-based speech recognizer, which uses parameterized, non-recursive ??hidden?? trajectory model of vocal tract resonances (VTR) or formants to capture the dynamic structure of long-range speech coarticulation and reduction. The underlying model of this recognizer carries out bi-directional FIR filtering on the piecewise constant sequences of the VTR targets. In this paper, we elaborate on two key aspects of the model. First, the phonetic context controls the movement direction and thus the formation of the VTR trajectories. This provides ??structured?? context dependency for speech acoustics without using context dependent parameters as required by HMMs. Second, VTR targets as the key context-independent parameters of the model vary across speakers. We describe an effective target-value normalization algorithm that can be applied to both training and unknown test speakers. We report experimental results demonstrating the effectiveness of the normalization algorithm in the context of structure-based speech recognition. We also provide computational analysis on the HTM-based speech decoder.
Index Terms: hidden trajectory model, phonetic contexts, normalization, vocal tract resonance, targets
In Proc. Interspeech
Publisher International Speech Communication Association
© 2007 ISCA. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the ISCA and/or the author. | <urn:uuid:402b5c7e-02c0-4c38-a7c8-dff64b3d2e1f> | {
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DISSERTATION DEFENSE: Helen Xiangyu Chen
xiangyuc at stanford.edu
Mon Aug 20 15:05:38 PDT 2012
DEPT OF PHYSICS
Ph.D. Candidate: Helen Xiangyu Chen
Research Advisor: H.-S. Philip Wong
Date: Monday, August 27, 2012
Time: 9am, refreshment served at 8:45am
Location: Packard 202
Title: Graphene in Back-End-Of-Line Technology
Back-End-Of-Line technology have always been one of the major components of modern high-speed integrated circuits (ICs). In the most advanced IC technology, the capacitance associated with interconnects typically accounts for about 50% of the active processor power consumption, and the associated signal delay along interconnects is one of the main bottlenecks for the routing of high-speed signals. Conventional interconnect materials such as copper are facing great challenges to satisfy requirements when physical dimensions are scaled down to the nanoscale range and the need for new interconnect material becomes prominent.
In this work, we studied applications of graphene in BEOL technology. We successfully demonstrated integration of graphene interconnects with CMOS circuits and studied the high speed performance of these wires. We have also studied the reliability performance and failure mechanism of graphene interconnects. Finally, we demonstrated that application of graphene in BEOL can go beyond being used as interconnect. The unique physical and electrical properties of graphene makes it a promising candidate for being used as copper diffusion barrier as well.
More information about the labmembers | <urn:uuid:5eeaff93-cffd-46c3-bd23-3ddfd7e11789> | {
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Change impact analysis in product-line architectures
Change impact analysis is fundamental in software evolution, since it allows one to determine potential effects upon a system resulting from changing requirements. While prior work has generically considered change impact analysis at architectural level, there is a distinct lack of support for the kinds of architectures used to realize software product lines, so-called product-line architectures (PLAs). In particular, prior approaches do not account for variability, a specific characteristic of software product lines. This paper presents a new technique for change impact analysis that targets product-line architectures. We propose to join a traceability-based algorithm and a rule-based inference engine to effectively traverse modeling artifacts that account for variability. In contrast to prior approaches, our technique supports the mechanisms for (i) specifying variability in PLAs, (ii) documenting PLA knowledge, and (iii) tracing variability between requirements and PLAs. We demonstrate our technique by applying it to the analysis of requirements changes in the product-line architecture of a banking system. | <urn:uuid:89945754-713d-43cb-8e6a-c116f3962a4d> | {
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Simulation and Modeling in Electrical Engineering
The SimulationX domain Electrical Engineering permits the modeling and simulation of electrical and magnetic phenomena using network models. In addition, detailed models for motors and stepping motors as well as the respective controllers link this domain to the libraries of the Power Transmission domain. The parameterization is application-oriented and follows established engineering principles.
Thus, the complex behavior as it appears in controlled electromechanical drives is easily modeled and simulated.
SimulationX Libraries in Electrical Engineering
Using the Electronics library tasks in electrical engineering and electronics can be solved efficiently. The library contains strongly idealized elements as well as realistically modeled components. Therefore, the elements are applicable for various application fields (mechatronics, power electronics, switchgear construction). Special sensor and actuator elements seamlessly integrate the electronics models into other engineering fields.
The Magnetics library allows modeling of electro-magnetic drives in terms of magnetic equivalent circuits. For this purpose, the library provides lumped network elements which can be used to describe approximatively the distribution of the magnetic flux. The structure of the magnetic circuit is strongly oriented towards the real system, which results in efficient and intuitive modeling.
Using the electric motor models, modeling and simulation tasks in electro-mechanic drive technology are solved efficiently. The close-to-reality models use an application-oriented parameterization concept and thus are easy to handle. In combination with the libraries in the Power Transmission domain complex controlled drives can be simulated, considering the mechanical components as well as the controls too. The motor models are applicable to various engineering fields (machinery drives, hybrid automotive powertrains, rail vehicle drives, etc.)
The Converter library provides models, which allow a controlled operation of the motors from the Electric Motors library. The library provides field-oriented controllers for synchronous and asynchronous motors, PWM controllers and 3-phase converters.
The library permits the modeling of stepping motor drives, which operate in full or half step mode, as well as Microstepping. The stepping motors are operated via controllers, which are also part of the library. The controllers operate as voltage or current controllers and additionally support pulse-width-modulated (PWM) and two-point operation. The stepping motor models seamlessly combine with models from the domains Mechanics and Controls. | <urn:uuid:f54d41ea-16d7-42a3-b5eb-0f87572c6ad8> | {
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Pure Appl. Chem., 2000, Vol. 72, No. 8, pp. 1405-1423
Quantum chemistry in the 21st century (Special topic article)
Abstract: Quantum chemistry is the field in which solutions to the Schrödinger equation are used to predict the properties of molecules and solve chemical problems. This paper considers possible future research directions in light of the discipline's past successes. After decades of incremental development—accompanied by a healthy dose of skepticism from the experimental community—the ready availability of fast computers has ushered in a "golden age" of quantum chemistry. In this new era of acceptance, theoretical predictions often precede experiment in small molecule chemistry, and quantum chemical methods play an ever greater role in biochemical and other larger systems. Quantum chemists increasingly divide their efforts along three fronts: high-level (spectroscopic) accuracy for small molecules, characterized by such techniques as Brueckner methods, r12 formalisms, and multireference calculations; parameterization- or extrapolation-based intermediate-level schemes (such as Gaussian-N theory) for medium molecules; and lower-level (chemical) accuracy for large molecules, characterized by density functional theory and linear scaling techniques. These tools, and quantum chemistry as a whole, are examined here from a historical perspective and with a view toward their future applications. | <urn:uuid:1222b93c-0795-41f4-b6b6-5e8fe6a10ca7> | {
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The problem of reabsorption in luminescent solar concentrators (LSC) is discussed. A mathematical development is presented which enables the LSC gain to be calculated based on the optical properties of the materials and a random walk formalism. Two- and three-dimensional analyses are used. A detailed set of calculations for a common dye (rhodamine 6G) is used to examine the practicality of employing a single dye. The effects of diameter, thickness, and quantum yield on the LSC output are presented. The spectrum of the LSC output as a function of concentration is calculated. It is suggested that LSCs can be made more efficient with a system which utilizes radiationless electronic excited state transport and trapping as intermediate steps between absorption and reemission. Trap emission substantially avoids the reabsorption problem.
© 1981 Optical Society of America
R. W. Olson, Roger F. Loring, and M. D. Fayer, "Luminescent solar concentrators and the reabsorption problem," Appl. Opt. 20, 2934-2940 (1981) | <urn:uuid:5fdab956-bc93-4cb8-bea1-c13a317b3d95> | {
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EU-funded scientists developed a novel foundry process using moulds formed by ‘binding’ metallic particles with application of a magnetic field. The process produced high-quality, complex parts at a very competitive cost.
While most people would not be interested in a cake mould that had to be ‘broken off’ the cake after baking and cooling, such moulds are actually among the most common for producing metal components.
Material is placed around a patterned shape, basically the shape one wishes to produce, in two different pieces. The material then hardens, it is removed from the pattern and the two pieces are put together to form the mould for the desired shape.
After the metal is formed using the mould, the mould itself is broken away and the part is retrieved. Among the three most common foundry processes using expendable moulds are sand casting, lost wax and lost foam techniques.
Sand casting uses sand as the mould material. The lost wax and lost foam (from polystyrene beads) techniques rely on wax and foam moulds, respectively.
European researchers developed an innovative expendable-mould foundry process, magnetic moulding, with funding for the Magnet project. Magnetic moulding combined the advantages of the lost foam process with those of permanent moulds. Namely, it was environmentally friendly, cost-effective and capable of producing high-quality, complex parts of a variety of sizes and from numerous materials.
The technology used an expendable pattern around which metallic particles were bonded together by application of a magnetic field. Once the cast metal solidified in the mould, the magnetic field was removed. The metallic particles fell away and could be reused in subsequent castings and the part itself was recovered.
Production of five different pieces using four different metal alloys confirmed that the process produced complex shapes. Components exhibited better metallurgical and mechanical properties than pieces obtained by the three most common expendable mould techniques. In addition, the magnetic mould process reduced cycle time compared to the other foundry processes.
Low investment cost with no major change to present lost foam facilities should make the technology very attractive to European foundries, able to produce higher quality, more complex parts and thus enhance competitiveness in a huge market. | <urn:uuid:e30e5919-eae4-4ab1-877a-3352e856cac9> | {
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A string-like activity system is a purposeful process, structured and governed to achieve its aim. It is depicted as an arrow.
Any activity involves movement and is therefore a process.
If the activity or process is purposeful, it is referred to as an activity system (in our terminology) or process system (by some other systems thinkers). The use of the term process in the management literature (e.g. as in business process) actually refers to a process system or activity system.
An activity or process that is not purposeful, structured and governed to achieve its purpose is a random activity or random process.
More specifically, process refers to a flow of substance in time and space. (Substance consists of matter, energy and information or mei, in short).
If the process is organised as a system, the mei flow has a purpose derived from the values or ethos of the system and gives rise to a specific aim or intended outcome. It also has structure, which gives it stability in time and space, as well as governance, which ensures that the system achieves its intended outcome.
An activity system can be both a function and a project:
Function refers to an activity system that is an inherent part of an entity system. Examples are the circulation function in the body, the work-life of a person, the marketing function of an organisation, the education function of a society, the photosynthesis of plants, or the rainfall and evaporation circulation of the planet.
Project is an activity system that ceases to exist when it is complete. Examples are a building project or an education assignment.
In a process-based worldview, the activity system is the fundamental unit of analysis and (re)design.
relevance for the change manager
Change managers need to be process thinkers.
what is the relevance of this concept in your situation? | <urn:uuid:bd8bac90-8e4d-4fee-a8c8-d75945bddced> | {
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Tyson, Gareth and Grace, P. and Blair, Gordon S. and Mauthe, Andreas (2009) Fine Grained Component Engineering of Adaptive Overlays: Experiences and Perspectives. Working Paper. Lancaster University.
Recent years have seen significant research being carried out into peer-to-peer (P2P) systems. This work has focused on the styles and applications of P2P computing, from grid computation to content distribution; however, little investigation has been performed into how these systems are built. Component based engineering is an approach that has seen successful deployment in the field of middleware development; functionality is encapsulated in ‘building blocks’ that can be dynamically plugged together to form complete systems. This allows efficient, flexible and adaptable systems to be built with lower overhead and development complexity. This paper presents an investigation into the potential of using component based engineering in the design and construction of peer-to-peer overlays. It is highlighted that the quality of these properties is dictated by the component architecture used to implement the system. Three reusable decomposition architectures are designed and evaluated using Chord and Pastry case studies. These demonstrate that significant improvements can be made over traditional design approaches resulting in much more reusable, (re)configurable and extensible systems.
Actions (login required) | <urn:uuid:8d7ac677-c8c2-452e-aa71-2fc1cdd61327> | {
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Zhu, H. (2012) Chunk-Based Resource Allocation in OFDMA Systems - Part II: Joint Chunk, Power and Bit Allocation. IEEE Transactions on Communications, 60 (2). pp. 499-509. ISSN 0090-6778.
|The full text of this publication is not available from this repository. (Contact us about this Publication)|
By grouping a number of adjacent subcarriers into a chunk, resource allocation can be carried out chunk by chunk in orthogonal frequency division multiple access (OFDMA) systems. Chunk-based resource allocation is an effective approach to reduce the complexity of resource allocation in OFDMA systems. In this paper, a chunk-based resource allocation scheme, i.e. joint chunk, power and bit allocation, is proposed and analyzed by maximizing the throughput under a total transmit power constraint. A scaling factor is introduced to achieve optimal allocation. Considering the digital nature of bits per symbol per subcarrier (bits/symbol/subcarrier), a digitization process is proposed to digitize the theoretically allocated bits/symbol/subcarrier to integer. System parameters, such as the power constraint, number of users, coherence bandwidth, number of subcarriers and number of chunks, are introduced and their impacts on the average throughput are studied. The performance of the dynamic power allocation scheme is compared with the fixed power allocation scheme. The numerical results show that the theoretical throughput of the fixed power allocation scheme is quite close to that of the dynamic power allocation scheme. However, when the digital nature of bits/symbol/subcarrier is considered, the average throughput of the dynamic power allocation outperforms the fixed power allocation scheme.
|Uncontrolled keywords:||Resource allocation, orthogonal frequency division multiple Access (OFDMA), dynamic power allocation, digital nature of bits, multiuser diversity|
|Subjects:||T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK5101 Telecommunications > TK5103.4 Broadband (inc wireless broadband)|
|Divisions:||Faculties > Science Technology and Medical Studies > School of Engineering and Digital Arts > Broadband & Wireless Communications|
|Depositing User:||Jenny Harries|
|Date Deposited:||17 Aug 2012 12:46|
|Last Modified:||28 Aug 2012 08:15|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/30181 (The current URI for this page, for reference purposes)|
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Thesis or dissertation
Date of this Version
In this thesis, we investigate the computational methods for both diffuse and general reflections in realistic image synthesis and propose two new approaches: the overrelaxation solution and the Bernstein polynomial solution.
One of the major concerns with the radiosity method is its expensive computing time and memory requirements. In this thesis, we analyze the convergence behavior of the progressive refinement radiosity method and propose two overrelaxation algorithms: the gathering and shooting solution and the positive overshooting solution. We modify the conventional shooting method to make the optimal use of the visibility information computed in each iteration. Based on a concise record of the history of the unshot light energy distribution, a solid convergence speed-up is achieved.
Though a great effort has been made to extend the radiosity method to accommodate general non-diffuse reflection, the current algorithms are still quite limited to simple environment settings. In this thesis, we propose using the piecewise spherical Bernstein basis functions over a geodesic triangulation to represent the radiance function. The representation is intrinsic to the unit sphere, and can be efficiently stored, evaluated, and subdivided by the numerically stable de Casteljau algorithm. We demonstrate that the computation of other fundamental radiometric quantities such as vector irradiance and reflected radiance can be reduced to the integration of the piecewise spherical Bernstein basis functions. A novel geometric integration algorithm based on adaptive domain subdivision is presented for the Bernstein-B´ezier polynomials over a geodesic triangle on the unit sphere.
Date Posted: 14 September 2006 | <urn:uuid:153bc708-8c58-41b5-a3e8-46e3f403fbcd> | {
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Search Swinburne Research Bank
Home List of Titles Principal characteristics of turbulent gas-particulate flow in the vicinity of single tube and tube bundle structure
Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/22025
- Principal characteristics of turbulent gas-particulate flow in the vicinity of single tube and tube bundle structure
- Morsi, Yosry S.; Tu, J. Y.; Yeo, G. H.; Yang, W.
- In this paper the particle rebounding characteristics of a gas–particle flow over a cylindrical body and an in-line tube bundle arrangement is investigated. With the aid of both experimental and numerical approaches, the mean particulate flow patterns, comprising both incident and rebound particles resulting from the impact of particles on solid walls, are examined. In the experimental investigation, a two-dimensional laser-Doppler anemometry (LDA) technique is used in the immediate vicinity of the body surface to measure the instantaneous incident and rebound particle velocities. The Reynolds-averaging Navier–Stokes equations are solved for the continuum gas phase and the results are used in conjunction with a Lagrangian trajectory model to predict the particle-rebound characteristics. For the single tube model, the experimental observations, also confirmed through computations, reveal a particle rebound zone where the mean particulate flow pattern is significantly modified due to the contribution of the rebound particles during the process of particle-wall impact interaction. This particle rebound zone is found to be a function of mainly the Stokes number (particle inertia), and to a lesser extent on the fluid Reynolds number (gas flow condition) except for high gas flow velocities. For the in-line tube bundle model, particles being rebounded from the first row of tubes at upstream migrated downstream and impinged the other tubes in an extremely complex and random disposition. Detailed measurements on the flow and turbulent characteristics within the subset containing two cylindrical tubes representing the flow over the first and second row tubes in the tube bundle configuration revealed that the heavier particles possessed higher axial and transverse velocity fluctuations than the gas and lighter particles. A means of quantifying the erosion rate using a semi-empirical relationship and CFD approach is presented. The erosion distributions were found to be significantly different between the lighter and heavier particles. Analysis of the effect of the above-mentioned parameters on the rebounding particle flow characteristics and their interrelationship has provided a better understanding on the behaviour of particulate flow impinging on a solid wall body or series of solid bodies. The usefulness of employing the experimental and computational approaches to quantify the particle-wall impact interaction phenomena in this study provides the basis for additional investigations to be undertaken to better comprehend the particulate behaviour in tube bundle structure, for example staggered tube arrangement commonly found in many commercial heat exchangers.
- Publication type
- Journal article
- Research centre
- Swinburne University of Technology. Faculty of Engineering and Industrial Sciences
- Chemical Engineering Science, Vol. 59, no. 15 (2004), pp. 3141-3157
- Publication year
- LDA technique; Particle-wall impact; Confined gas-particle flow; Lagrangian approach
- Publisher URL
- Copyright © 2004 Elsevier Ltd. All rights reserved.
- Peer reviewed | <urn:uuid:d8b0f3a1-2f54-44a4-88c6-44a1b6a94ec4> | {
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condensed matter, superconductivity
In this paper we use non-Gaussian hydrodynamics to study the magnetic response of a flux-line liquid in the mixed state of a type-II superconductor. Both the derivation of our model, which goes beyond conventional Gaussian flux liquid hydrodynamics, and its relationship to other approaches used in the literature are discussed. We focus on the response to a transverse tilting field which is controlled by the tilt modulus, c44, of the flux array. We show that interaction effects can enhance c44 even in infinitely thick clean materials. This enhancement can be interpreted as the appearance of a disentangled flux-liquid fraction. In contrast to earlier work, our theory incorporates the nonlocality of the intervortex interaction in the field direction. This nonlocality is crucial for obtaining a nonvanishing renormalization of the tilt modulus in the thermodynamic limit of thick samples.
harvested from arXiv.org | <urn:uuid:4d0ad213-351b-4b6a-af15-6622b377c8cc> | {
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US 7091385 B2
The present invention relates to new molecular sieve SSZ-71 prepared using a N-benzyl-1,4-diazabicyclo[2.2.2]octane cation as a structure-directing agent, methods for synthesizing SSZ-71 and processes employing SSZ-71 in a catalyst.
1. A method for performing an acylation reaction on an aromatic substrate ArHn to form a product ArHn-1COR, the method comprising the steps of:
providing the aromatic substrate,
intimately mixing the substrate and an acylating agent, wherein the acylating agent is selected from the group consisting of a carboxylic acid derivative, a carboxylic acid, an acid anhydride, an ester, and an acyl halide, and
exposing an intimate mixture thus formed to a catalyst comprising a molecular sieve produced by the method comprising:
(1) preparing an as-synthesized molecular sieve having a composition, as synthesized and in the anhydrous state, in terms of mole ratios as follows:
wherein Y is silicon, germanium or a mixture thereof; W is zinc, titanium or mixtures thereof; d is 1 or 2 (i.e., d is 1 when W is divalent or 2 when W is tetravalent); M is an alkali metal cation, alkaline earth metal cation or mixtures thereof; n is the valence of M (i.e., 1 or 2); and Q is a N-benzyl-1,4-diazabicyclo[2.2.2]octane cation, the as-synthesized molecular sieve having the X-ray diffraction lines of Table I;
(2) thermally treating the as-synthesized molecular sieve at a temperature and for a time sufficient to remove the N-benzyl-1,4-diazabicyclo[2.2.2]octane cation from the molecular sieve; and
(3) optionally, replacing at least part of the zinc and/or titanium with a metal selected from the group consisting of aluminum, gallium, iron, boron, indium, vanadium and mixtures thereof.
2. The method of
3. The method of
4. The method of
This application claims the benefit under 35 USC 119 of Provisional Application No. 60/639,214, filed Dec. 23, 2004.
1. Field of the Invention
The present invention relates to new molecular sieve SSZ-71, a method for preparing SSZ-71 using a N-benzyl-1,4-diazabicyclo[2.2.2]octane cation as a structure directing agent and the use of SSZ-71 in catalysts for, e.g., hydrocarbon conversion reactions.
2. State of the Art
Because of their unique sieving characteristics, as well as their catalytic properties, crystalline molecular sieves and zeolites are especially useful in applications such as hydrocarbon conversion, gas drying and separation. Although many different crystalline molecular sieves have been disclosed, there is a continuing need for new zeolites with desirable properties for gas separation and drying, hydrocarbon and chemical conversions, and other applications. New zeolites may contain novel internal pore architectures, providing enhanced selectivities in these processes.
Crystalline aluminosilicates are usually prepared from aqueous reaction mixtures containing alkali or alkaline earth metal oxides, silica, and alumina. Crystalline borosilicates are usually prepared under similar reaction conditions except that boron is used in place of aluminum. By varying the synthesis conditions and the composition of the reaction mixture, different zeolites can often be formed.
The present invention is directed to a family of molecular sieves with unique properties, referred to herein as “molecular sieve SSZ-71” or simply “SSZ-71”. Preferably, SSZ-71 is in its silicate, zincosilicate, aluminosilicate, titanosilicate, germanosilicate, vanadosilicate, ferrosilicate or borosilicate form. The term “silicate” refers to a molecular sieve having a high mole ratio of silicon oxide relative to aluminum oxide, preferably a mole ratio greater than 100, including molecular sieves comprised entirely of silicon oxide. As used herein, the term “zincosilicate” refers to a molecular sieve containing both zinc oxide and silicon oxide. The term “aluminosilicate” refers to a molecular sieve containing both aluminum oxide and silicon oxide and the term “borosilicate” refers to a molecular sieve containing oxides of both boron and silicon.
In accordance with the present invention, there is provided a method for performing an acylation reaction on an aromatic substrate ArHn to form a product ArHn-1COR, the method comprising the steps of:
The molecular sieve of the present invention may be predominantly in the hydrogen form, which hydrogen form is prepared by ion exchanging with an acid or with a solution of an ammonium salt followed by a second calcination. If the molecular sieve is synthesized with a high enough ratio of SDA cation to sodium ion, calcination alone may be sufficient. For high catalytic activity, the SSZ-71 molecular sieve may be predominantly in its hydrogen ion form. As used herein, “predominantly in the hydrogen form” means that, after calcination, at least 80% of the cation sites are occupied by hydrogen ions and/or rare earth ions. It should be noted that the mole ratio of the first oxide or mixture of first oxides to the second oxide can be infinity, i.e., there is no second oxide in the molecular sieve. In these cases, the molecular sieve is an all-silica molecular sieve or a germanosilicate.
The present invention comprises a family of molecular sieves designated herein “molecular sieve SSZ-71” or simply “SSZ-71”. In preparing SSZ-71, a N-benzyl-1,4-diazabicyclo[2.2.2]octane cation (referred to herein as “benzyl DABCO”) is used as a structure directing agent (“SDA”), also known as a crystallization template. The SDA useful for making SSZ-71 has the following structure:
The SDA cation is associated with an anion (X−) which may be any anion that is not detrimental to the formation of the molecular sieve. Representative anions include halogen, e.g., fluoride, chloride, bromide and iodide, hydroxide, acetate, sulfate, tetrafluoroborate, carboxylate, and the like. Hydroxide is the most preferred anion.
Benzyl DABCO and a method for making it are disclosed in U.S. Pat. No. 5,653,956, issued Aug. 5, 1997 to Zones.
SSZ-71 is prepared from a reaction mixture having the composition shown in Table A below.
In practice, SSZ-71 is prepared by a process comprising:
(a) preparing an aqueous solution containing sources of at least one oxide capable of forming a molecular sieve and a benzyl DABCO cation having an anionic counterion which is not detrimental to the formation of SSZ-71;
(b) maintaining the aqueous solution under conditions sufficient to form SSZ-71; and
(c) recovering the SSZ-71.
SSZ-71 can be prepared as a zincosilicate or titanosilicate. However, once the SSZ-71 is made, the zinc and/or titanium can be replaced with other metals by techniques well known in the art. Accordingly, SSZ-71 may comprise the molecular sieve and the SDA in combination with metallic and non-metallic oxides bonded in tetrahedral coordination through shared oxygen atoms to form a cross-linked three dimensional crystal structure. The metallic and non-metallic oxides comprise one or a combination of oxides of (1) a first tetravalent element(s), and (2) one or a combination of a divalent element(s), trivalent element(s), pentavalent element(s), second tetravalent element(s) different from the first tetravalent element(s) or mixture thereof. The first tetravalent element(s) is preferably selected from the group consisting of silicon, germanium and combinations thereof. More preferably, the first tetravalent element is silicon. The divalent element, trivalent element, pentavalent element and second tetravalent element (which is different from the first tetravalent element) is preferably selected from the group consisting of zinc, aluminum, gallium, iron, boron, titanium, indium, vanadium and combinations thereof. More preferably, the divalent or trivalent element or second tetravalent element is zinc, aluminum, titanium or boron.
Silicon can be added as silicon oxide or Si(OC2H5)4. Zinc can be added as a zinc salt such as zinc acetate. Titanium can be added as Ti(OC2H5)4.
A source zeolite reagent may provide a source of metals. In most cases, the source zeolite also provides a source of silica. The source zeolite may also be used as a source of silica, with additional silicon added using, for example, the conventional sources listed above. Use of a source zeolite reagent is described in U.S. Pat. No. 5,225,179, issued Jul. 6, 1993 to Nakagawa entitled “Method of Making Molecular Sieves”, the disclosure of which is incorporated herein by reference.
Typically, an alkali metal hydroxide and/or an alkaline earth metal hydroxide, such as the hydroxide of sodium, potassium, lithium, cesium, rubidium, calcium, strontium, barium and magnesium, is used in the reaction mixture; however, this component can be omitted so long as the equivalent basicity is maintained. The SDA may be used to provide hydroxide ion. Thus, it may be beneficial to ion exchange, for example, the halide to hydroxide ion, thereby reducing or eliminating the alkali metal hydroxide quantity required. The alkali metal cation or alkaline earth cation may be part of the as-synthesized material, in order to balance valence electron charges therein.
The reaction mixture is maintained at an elevated temperature until the crystals of the SSZ-71 are formed. The hydrothermal crystallization is usually conducted under autogenous pressure, at a temperature between 100° C. and 200° C., preferably between 135° C. and 160° C. The crystallization period is typically greater than 1 day and preferably from about 3 days to about 20 days.
Optionally, the molecular sieve is prepared using mild stirring or agitation.
During the hydrothermal crystallization step, the SSZ-71 crystals can be allowed to nucleate spontaneously from the reaction mixture. The use of SSZ-71 or SSZ-42 (disclosed in U.S. Pat. No. 5,653,956, issued Aug. 5, 1997 to Zones) crystals as seed material can be advantageous in decreasing the time necessary for complete crystallization to occur. In addition, seeding can lead to an increased purity of the product obtained by promoting the nucleation and/or formation of SSZ-71 over any undesired phases. When used as seeds, as-synthesized SSZ-71 or SSZ-42 crystals (containing the SDA) are added in an amount between 0.1 and 10% of the weight of first tetravalent element oxide, e.g. silica, used in the reaction mixture.
Once the molecular sieve crystals have formed, the solid product is separated from the reaction mixture by standard mechanical separation techniques such as filtration. The crystals are water-washed and then dried, e.g., at 90° C. to 150° C. for from 8 to 24 hours, to obtain the as-synthesized SSZ-71 crystals. The drying step can be performed at atmospheric pressure or under vacuum.
SSZ-71 as prepared has a mole ratio of an oxide selected from silicon oxide, germanium oxide and mixtures thereof to an oxide selected from zinc oxide, titanium oxide and mixtures thereof greater than about 15. SSZ-71 further has a composition, as synthesized (i.e., prior to calcination of the SSZ-71) and in the anhydrous state, in terms of mole ratios, shown in Table B below.
SSZ-71 can be made with a mole ratio of YO2/WOd of ∞, i.e., there is essentially no WOd present in the SSZ-71. In this case, the SSZ-71 would be an all-silica material or a germanosilicate. If SSZ-71 is prepared as a zincosilicate, the zinc can be removed and replaced with metal atoms by techniques known in the art. See, for example, U.S. Pat. No. 6,117,411, issued Sep. 12, 2000 to Takewaki et al. Metals such as aluminum, gallium, iron, boron, titanium, indium, vanadium and mixtures thereof may be added in this manner.
It is believed that SSZ-71 is comprised of a new framework structure or topology which is characterized by its X-ray diffraction pattern. SSZ-71, as-synthesized, has a structure whose X-ray powder diffraction pattern exhibit the characteristic lines shown in Table I and Table II and is thereby distinguished from other molecular sieves. The XRD data shown in Table I and IA was obtained from a sample of SSZ-71 prepared in the presence of sodium hydroxide. The XRD data shown in Table II and IIA was obtained from a sample of SSZ-71 prepared in the presence of strontium hydroxide.
Table IA below shows the X-ray powder diffraction lines for as-synthesized Zn-SSZ-71 prepared with NaOH including actual relative intensities.
Table IIA below shows the X-ray powder diffraction lines for as-synthesized SSZ-71 (Zn-SSZ-71 prepared with Sr(OH)2) including actual relative intensities.
The X-ray powder diffraction patterns were determined by standard techniques. The radiation was the K-alpha/doublet of copper. The peak heights and the positions, as a function of 2θ where θ is the Bragg angle, were read from the relative intensities of the peaks, and d, the interplanar spacing in Angstroms corresponding to the recorded lines, can be calculated.
The variation in the scattering angle (two theta) measurements, due to instrument error and to differences between individual samples, is estimated at ±0.15 degrees.
The X-ray diffraction pattern of Table I is representative of “as-synthesized” or “as-made” SSZ-71 molecular sieves. Minor variations in the diffraction pattern can result from variations in the silica-to-zinc or silica-to-titanium mole ratio of the particular sample due to changes in lattice constants. In addition, sufficiently small crystals will affect the shape and intensity of peaks, leading to significant peak broadening.
The molecular sieve produced by exchanging the metal or other cations present in the molecular sieve with various other cations (such as H+ or NH4 +) yields essentially the same diffraction pattern, although again, there may be minor shifts in the interplanar spacing and variations in the relative intensities of the peaks. Notwithstanding these minor perturbations, the basic crystal lattice remains unchanged by these treatments.
SSZ-71 can be used as-synthesized, but preferably will be thermally treated (calcined). Usually, it is desirable to remove the alkali metal cation by ion exchange and replace it with hydrogen, ammonium, or any desired metal ion. The molecular sieve can also be steamed; steaming helps stabilize the molecular sieve to attack from acids.
The molecular sieve can be used in intimate combination with hydrogenating components, such as tungsten, vanadium, molybdenum, rhenium, nickel, cobalt, chromium, manganese, or a noble metal, such as palladium or platinum, for those applications in which a hydrogenation-dehydrogenation function is desired.
Metals may also be introduced into the molecular sieve by replacing some of the cations in the molecular sieve with metal cations via standard ion exchange techniques (see, for example, U.S. Pat. No. 3,140,249 issued Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issued Jul. 7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued Jul. 7, 1964 to Plank et al.). Typical replacing cations can include metal cations, e.g., rare earth, Group IA, Group IIA and Group VIII metals, as well as their mixtures. Of the replacing metallic cations, cations of metals such as rare earth, Mn, Ca, Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, and Fe are particularly preferred.
The hydrogen, ammonium, and metal components can be ion-exchanged into the SSZ-71. The SSZ-71 can also be impregnated with the metals, or the metals can be physically and intimately admixed with the SSZ-71 using standard methods known to the art.
Typical ion-exchange techniques involve contacting the synthetic molecular sieve with a solution containing a salt of the desired replacing cation or cations. Although a wide variety of salts can be employed, chlorides and other halides, acetates, nitrates, and sulfates are particularly preferred. The molecular sieve is usually calcined prior to the ion-exchange procedure to remove the organic matter present in the channels and on the surface, since this results in a more effective ion exchange. Representative ion exchange techniques are disclosed in a wide variety of patents including U.S. Pat. No. 3,140,249 issued on Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issued on Jul. 7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued on Jul. 7, 1964 to Plank et al.
Following contact with the salt solution of the desired replacing cation, the molecular sieve is typically washed with water and dried at temperatures ranging from 65° C. to about 200° C. After washing, the molecular sieve can be calcined in air or inert gas at temperatures ranging from about 200° C. to about 800° C. for periods of time ranging from 1 to 48 hours, or more, to produce a catalytically active product especially useful in hydrocarbon conversion processes.
Regardless of the cations present in the synthesized form of SSZ-71, the spatial arrangement of the atoms which form the basic crystal lattice of the molecular sieve remains essentially unchanged.
SSZ-71 can be formed into a wide variety of physical shapes. Generally speaking, the molecular sieve can be in the form of a powder, a granule, or a molded product, such as extrudate having a particle size sufficient to pass through a 2-mesh (Tyler) screen and be retained on a 400-mesh (Tyler) screen. In cases where the catalyst is molded, such as by extrusion with an organic binder, the SSZ-71 can be extruded before drying, or, dried or partially dried and then extruded.
SSZ-71 can be composited with other materials resistant to the temperatures and other conditions employed in organic conversion processes. Such matrix materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and metal oxides. Examples of such materials and the manner in which they can be used are disclosed in U.S. Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat. No. 5,316,753, issued May 31, 1994 to Nakagawa, both of which are incorporated by reference herein in their entirety.
The molecular sieve of the present invention can be used in a catalyst for acylating an aromatic substrate ArHn, where n is at least 1, by reacting the aromatic substrate with an acylating agent in the presence of the catalyst. The product of the acylation reaction is ArHn-1COR where R is an organic radical.
Examples of the aromatic substrate include, but are not limited to, benzene, toluene, anisole and 2-naphthol. Examples of the acylating agent included, but are not limited to, carboxylic acid derivatives, carboxylic acids, acid anhydrides, esters, and acyl halides.
Reaction conditions are known in the art (see, for example, U.S. Pat. No. 6,630,606, issued Oct. 7, 2003 to Poliakoff et al., U.S. Pat. No. 6,459,000, issued Oct. 1, 2002 to Choudhary et al., and U.S. Pat. No. 6,548,722, issued Apr. 15, 2003 to Choudhary et al., all of which are incorporated herein by reference in their entirety). Typically, the acylation reaction is conducted with a weight ratio of the catalyst to the acylating agent of about 0.03 to about 0.5, a mole ratio of aromatic substrate to acylating agent of about 1.0 to about 20, a reaction temperature in the range of about 20° C. to about 200° C., a reaction pressure in the range of about 1 atm to about 5 atm, and a reaction time of about 0.05 hours to about 20 hours.
The following examples demonstrate but do not limit the present invention.
Zn-SSZ-71 is synthesized by preparing the gels, i.e., reaction mixtures, having the compositions, in terms of mole ratios, shown in the table below. 9.06 g of benzyl DABCO hydroxide (0.815 mmol/g) solution are mixed with 13.8 g of deionized water. Then, respectively, an appropriate amount of ammonium hydroxide or alkali hydroxide or alkaline earth hydroxide is added. Subsequently, 0.18 g of Zn(CH3COO)2 are added and stirred at room temperature overnight. Finally, 1.63 g of Cab-O-Sil M-5 are mixed and stirred at room temperature for 1 hour. The resulting gel is placed in a Parr bomb reactor and heated in an oven at 150° C. while rotating at 43 rpm. The reaction is held under these conditions for 17 and 29 days, respectively, of run time.
The products are analyzed by X-ray diffraction and determined to be Zn-SSZ-71.
Zn-SSZ-71 is synthesized using the procedure of Examples 1A–1H except that EDTA (ethylenediaminetetraacetic acid) is added together with NaOH to the benzyl DABCO hydroxide solution. The reaction is run at 150° C. under rotation at 43 rpm. The gel composition is given below.
The products are analyzed by X-ray diffraction and determined to be Zn-SSZ-71.
Si-SSZ-71 is synthesized using the procedure of Example 1A–1H except that (1) no Zn(CH3COO)2 is added, (2) 2 wt. % as-made B-SSZ-42 (on the SiO2 base) is used as seeds and (3) the reaction is run under static conditions. The gel compositions (excluding the seeds) are given below. The reaction is held under these conditions for 14 days of run time.
The products are analyzed by XRD and found to be Si-SSZ-71.
Si-SSZ-71 is synthesized using the procedure of Examples 3A–3B under static conditions except that 2 wt. % as-made Si-SSZ-71 (on the SiO2 base) is used as seeds and no ammonium hydroxide or alkali hydroxide such as KOH is used. The gel composition (excluding the seeds) is given below.
The products are analyzed by XRD and found to be Si-SSZ-71 (the product of Example 4A contained SSZ-42 as an impurity).
Si-SSZ-71 is synthesized as described in Examples 4A–4C under the following conditions:
The gel compositions and conditions are given below:
The products are analyzed by XRD and found to be Si-SSZ-71 with the exception of Example 5C at 15 days, which remained a gel.
Ti-SSZ-71 is synthesized by preparing the gels, i.e., reaction mixtures, having the composition, in terms of mole ratios, shown in the table below. Ti(OC2H5)4 and Cab-O-Sil M-5 are used as titanium and silicon source, respectively. 126.2 g of benzyl DABCO hydroxide (0.614 mmol/g) solution are mixed with 7.3 g of deionized water. Then, 0.61 g of Ti(OC2H5)4 are added under vigorous stirring and then further stirred at room temperature overnight. Subsequently, an appropriate amount of water is added to reach the water content given in the gel composition below because some water is evaporated when stirred overnight. Finally, 18.14 g of Cab-O-Sil M-5 are mixed and stirred at room temperature for 1 hour. The resulting gel is placed in a Parr bomb reactor and heated in an oven at 150 or 160° C. while rotating at 43 rpm.
The products are analyzed by X-ray diffraction and determined to be Ti-SSZ-71.
Ti-SSZ-71 is synthesized by preparing the gels, i.e., reaction mixtures, having the composition, in terms of mole ratios, shown in the table below. Ti(OC2H5)4 and Si(OC2H5)4 are used as titanium and silicon source, respectively. 39.13 g of Si(OC2H5)4 are placed in a plastic beaker. 1.30 g of Ti(OC2H5)4 are then quickly added to Si(OC2H5)4 under stirring. The mixture of Ti(OC2H5)4 and Si(OC2H5)4 is placed in an ice bath. 107.0 g of benzyl DABCO hydroxide (0.614 mmol/g) solution are added to this mixture under vigorous stirring and then further stirred at room temperature overnight. Subsequently, an appropriate amount of water is added to reach the water content given in the gel composition below because some water is evaporated when stirred overnight. The resulting gel is placed in a Parr bomb reactor and heated in an oven at 150 or 160° C. while rotating at 43 rpm.
The products are analyzed by X-ray diffraction and determined to be Ti-SSZ-71.
Si-SSZ-71 is synthesized as described in Examples 7A–7F except that 2 wt. % as-made Si-SSZ-71 (on the SiO2 base) is used as seeds. The gel composition (excluding the seeds) is given below. Ti(OC2H5)4 and Si(OC2H5)4 are used as titanium and silicon source, respectively. The resulting gel is placed in a Parr bomb reactor and heated in an oven at 150° C. while rotating at 43 rpm.
The products are analyzed by X-ray diffraction and determined to be Ti-SSZ-71.
Na/Zn-SSZ-71 as synthesized in Example IC with NaOH is calcined to remove the structure directing agent (SDA) as described below. A thin bed of Na/Zn-SSZ-71 in a calcination dish is heated in a muffle furnace from room temperature to 120° C. at a rate of 1° C./minute and held for 2 hours. Then, the temperature is ramped up to 540° C. at a rate of 1° C./minute and held for 5 hours. The temperature is ramped up again at 1° C./minute to 595° C. and held there for 5 hours. A 50/50 mixture of air and nitrogen passes through the muffle furnace at a rate of 20 standard cubic feet (0.57 standard cubic meters) per minute during the calcination process.
The calcined Na/Zn-SSZ-71 (5 g) prepared in Example 9 is with combined with 500 grams of 1 M aqueous Al(NO3)3 solution and treated under reflux for 100 hours. The resulting Al-SSZ-71 product is then washed with 1 liter of water, filtered and air-dried at room temperature in vacuum filter.
The Al-SSZ-71 material prepared in Example 10 is loaded with 1.0 wt.-% Pt via impregnation with aqueous Pt(NH3)4(NO3)2 solution and tested with bifunctionally catalyzed hydrocracking of FCC LCO (light cycle oil). The FCC LCO is first hydrotreated over a Ni/Mo hydrotreating catalyst at 660° F. and 1700 psig to reduce its sulfur and nitrogen contents. The hydrotreated LCO is then hydrocracked over Pt/Al-SSZ-71 at 750° F. and 1000 psig. The results from the simulated distillation via GC analysis are given below.
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Explore Careers - Job Market Report
Central control and process operators, mineral and metal processing, operate and monitor multi-function process control machinery and equipment to control the processing of mineral ores, metals or cement. They are employed in mineral ore and metal processing plants such as copper, lead and zinc refineries, uranium processing plants, steel mills, aluminum plants, precious metal refineries and cement processing plants.
blast furnace operator, central control caster, central control room operator, chief flotation operator, console operator – cement manufacturing, pelletizing control operator, roaster operator, rolling mill control operator.
- Co-ordinate and monitor the operation of a particular aspect of mineral ore, metal and cement processing production through control panels, computer terminals or other control systems, usually from a central control room
- Operate multi-function central process control machinery to grind, separate, filter, melt, roast, treat, refine or otherwise process mineral ores
- Observe computer printouts, video monitors and gauges to verify specified processing conditions and to make necessary adjustments
- Co-ordinate and supervise production crew such as machine and process operators, tenders, assistants and helpers
- Start up and shut down the production system in cases of emergency or as required by schedule
- Provide or organize training for members of production crew
- Maintain shift log of production and other data and prepare production and other reports.
Wages for Central Control and Process Operators, Mineral and Metal Processing in Yorkton--Melville Region
Wages depend on job requirements and work conditions. They also vary between regions, for reasons such as location, labour agreements, and the availability of workers. The wages below are estimated before taxes.
|Newfoundland and Labrador||15.75||33.16||38.18||Note|
|Prince Edward Island||N/A||N/A||N/A||Note|
- Date Modified: | <urn:uuid:5de5ef60-e7bc-4317-b9ec-0429a9d34146> | {
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In this letter, we investigate the problem of CFO estimation in OFDM systems when the timing offset and channel length are not exactly known. Instead of explicitly estimating the timing offset and channel length, we employ a multi-model approach, where the timing offset and channel length can take multiple values with certain probabilities. The effect of multimodel is directly incorporated into the CFO estimator. Results show that the proposed estimator outperforms the estimator selecting only the most probable model and the method taking the maximal model.
Date of Publication: March 2010 | <urn:uuid:048cad78-077f-429a-9be5-4b67a3aa6cf3> | {
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This paper treats gunshot detection in audio streams from movies as a maximization task, where the solution is obtained by means of dynamic programming. The proposed method seeks the sequence of segments and respective class labels, i.e., gunshots vs. all other audio types, that maximize the product of posterior class label probabilities, given the segments' data. The required posterior probabilities are estimated by combining soft classification decisions from a set of Bayesian Network combiners. Tests that have been performed on a large set of audio streams indicate that the proposed method yields high performance in terms of both precision and recall of detected gunshot events.
Date of Conference: March 31 2008-April 4 2008 | <urn:uuid:7ca3cdb8-06d2-4c05-880d-30805d4653e2> | {
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With the development of grid technology, sensitive files and data protection become difficult tasks multi-domains. Traditional access control mechanisms are not suitable to such distributed environment. Several models and mechanisms utilize trust to assist access control decision. But few explicitly consider trust and risk as two separate factors which affect interactions between peers. In this paper, we present a novel mechanism which considers both trust and risk as two vital parameters to assist access control decision. In addition, a novel model of trust evaluation is proposed to represent the confidence in the peer. And to appease peoplepsilas anxiety about loss, a new model of risk assessment is also presented to indicate impacts on resources. At the end of this paper, simulation results will indicate that our mechanism is able to secure local system more efficiently and reliably.
Date of Conference: 13-15 Dec. 2008 | <urn:uuid:03721e6f-9bfc-40a3-876b-2ee583561d96> | {
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Engineering and Environmental Sciences
Turkish Journal of Engineering and Environmental SciencesStability for Structures Armored with Core-LocTM
Yıldız Technical University, Department of Civil Engineering,
Abstract: In conventional two-layer systems various armor units such as tetrapod, dolos, and tribar have been commonly used. Recent developments are accropode and core-locTM, which can be used in a single layer of armoring. The units for one-layer systems have an interlocking response under waves and hence their stability is high. The structure slope, wave conditions and placement methods are other areas of interest related to the stability of breakwater armor units. This study was intended to investigate the stability of core-locTM units over a 1:1.5 slope under non-breaking / breaking and regular/random wave conditions and also to compare two different placement methods of core-locTM as they affect breakwater stability. The results are also reviewed in comparison with previous studies of one-layer breakwater stability. In addition, run-up and run-down on core-locTM armor layers were also investigated.
Key Words: Core-locTM, stability, placement, run-up, breakwater
Turkish J. Eng. Env. Sci., 29, (2005), 225-233.
Full text: pdf
Other articles published in the same issue: Turkish J. Eng. Env. Sci.,vol.29,iss.4. | <urn:uuid:ae4885be-fca6-4a60-86d6-34b1e2d34d00> | {
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Jun 24, 2009
Self-assembled nanogaps support molecular electronics
Single-molecule devices provide a pathway to understanding the transport behavior of molecules and a possible mechanism for integrating molecular circuits in nanoelectronics. However, the fabrication of a molecular-scaled nanogap, which provides the framework for the device, can represent a significant challenge. The gap is typically a few nanometers long, which is difficult to realize with conventional micro/nanofabrication techniques.
One way around the problem is to use solution-based self-assembly, as demonstrated by researchers from the University of Copenhagen, Denmark, and Hunan University, China.
An artist's impression of the device is shown above. The molecular device was produced by self-assembly of either a single or a few rigid thiol end-capped molecules onto a gold nanoparticle connected to a conducting nanowire of doped SnO2, followed by further self-assembly of gold nanorods onto the other end of the molecules. No in situ monitoring is required during the process of device fabrication and no advanced electron-beam and other top-down nanofabrication techniques were used.
Conductive tip atomic force microscopy was employed to measure the conductance of the molecular device in the nanogap. This method overcomes some of the challenges faced in the field of molecular electronics such as bridging the gap between the single molecule length scale and the dimensions of the micro-fabricated electrodes.
The team presented its work in Nanotechnology 20 245205.
About the author
The work was performed at the University of Copenhagen, Denmark, and Hunan University, China. Prof. Thomas Bjørnholm is the director of the Nano-Science Center, University of Copenhagen. His research interests span molecular electronics, single-molecule science, nanochemistry and bionanotechnology. | <urn:uuid:fdaa4e91-f277-4a97-8541-707be4a37915> | {
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This study has been conducted within a Research partnership active since 2009 between Piaggio Aero Industries & University of Rome Tor Vergata addressed to the solution of the aeroelastic problem using the mesh morphing software RBF Morph and recently extended to shape optimization methods. A wind tunnel model of a business class aircraft in complete configuration validated using experimental data from a test campaign performed by Piaggio in the ONERA S2MA transonic facility is considered as the baseline geometry. Sweep angles are changed for both wing sections
keeping the leading edges straight, preserving the wing area imposing relative movement between root section, kink section and wing tip using an accurate two step morphing strategy. A first RBF solution is used to reshape the wing (step 1), the set-up is then completed limiting the morphing domain with a box and constraining other surfaces (step 2). The quality of the mesh is verified in advance for full range of both modifiers. The baseline Fluent model is iterated until a good convergence is achieved (1500 its). Such model is then parameterized using custom parameters to update shape at initialization; each shape is calculated (500 its) starting from converged flow solution of baseline. Drag and Lift are exported as output parameters (Cd, Cl). Shape parameters (eps-1, eps-2) are steered from Workbench whilst efficiency is computed as a derived parameter. MOGA algorithm is used on Kriging response surface (optimal space filling points + validated optimal candidates). As expected slight improvements are achieved (less than 1%) with respect to the baseline, already optimized for the same flight condition; nevertheless a wide variation range of efficiency (25%) is observed in the design space, near the maximum the optimal area exhibits a flat behavior. | <urn:uuid:34240402-6f68-40dd-9ebe-6199afe7ec7d> | {
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Peroxide is an ion. Its chemical formula is O22-. Peroxide can be a reducing agent or an oxidizing agent. More often it is an oxidizing agent. It can be reduced to oxide or oxidized to oxygen. Hydrogen peroxide is the most common peroxide. Barium peroxide is another peroxide.
Related pages [change] | <urn:uuid:91dc63f7-764c-444c-9c8f-dd3c59965d36> | {
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Biggs, J.D. (2010) Singularities of optimal attitude motions. In: 18th IFAC Symposium on Automatic Control in Aerospace, ACA 2010, 2010-09-06 - 2010-09-10, Nara, Japan.
|PDF (Biggs_JD_-_strathprints_-_Singularities_of_optimal_attitude_motions_Sept_2010.pdf) |
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This paper considers the problem of planning optimal attitude motions for spacecraft. The extremal solutions that result from this optimization problem are characterized and their singularities identified. Following this these singularities are solved analytically inferring the form of particular optimal velocities. These particular solutions are then integrated and their corresponding motions derived independently of a local coordinate chart. These motions have the potential to be used as smooth, optimal reference trajectories for performing certain re-orientations for spacecraft.
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Volume 35, Issue 1 (January 2012)
The Effect of Contact on the Filter Paper Method for Measuring Soil Suction
The filter paper method is one of the most commonly used and critiqued techniques for measuring soil suction. However, many aspects related to its use still require some clarification. The results of a comprehensive study on the effect of the contact between the soil grains and soil water and the filter paper are presented herein. We investigated the influence of the equilibration time, the texture of the porous material and the degree of contact, or lack thereof, between the soil grains and the filter paper using Whatman #42 and three different types of porous material. To enhance the difference between the total suction and the matrix suction, osmotic suction was induced by saturating the specimens with a sodium chloride solution. | <urn:uuid:1c49d4db-0b3f-4770-9d58-eb801477d887> | {
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Patent application title: IMPREGNATED CARBON FOR WATER TREATMENT
Kenn R. Vest (Davidson, NC, US)
Arvind S. Patil (Davidson, NC, US)
IPC8 Class: AB01J3918FI
Class name: Processes ion exchange or selective sorption including rehabilitating or regenerating exchange material or sorbent
Publication date: 2013-01-10
Patent application number: 20130008855
A method for treating aqueous solutions, wherein a filtrate material is
manufactured to have a polymer with ion exchange properties adhered to
the surface or impregnated within a porous, granular particle such that
the resultant structure does not result in any agglomeration or binding
of the granular particles, thereby retaining the maximum surface area of
the particle for reacting with metal impurities in solution. A filtrate
material comprised of a porous granulated particle and an ion exchange
polymer. A method of treating aqueous solutions by passing an aqueous
solution through the filtrate material to remove metal impurities in the
solution. A method of regenerating the filtrate material that is
saturated with metal impurities.
1. A filtrate material for treating liquid solutions comprising: a
porous, unagglomerated and unbound granular material impregnated with a
polymeric material having ion exchange properties.
3. The filtrate material of claim 1 wherein the polymeric material is trapped inside said porous, granular material thereby exposing high levels of surface area of the polymeric ion exchange material without occluding the pores of the granular material.
4. The filtrate material of claim 1 wherein the polymer has anionic or cationic properties or a mixture thereof.
6. The filtrate material of claim 1 wherein the granular material is selected from the group consisting of carbons, titania, alumina, zirconia, iron oxides, zinc oxides, manganese sands, diatomaceous earth, and clays.
7. The filtrate material of claim 1 wherein the granular material is activated carbon selected from the group consisting of coconut shell, bituminous, lignite, wood based, and bamboo.
9. The filtrate material of claim 1 wherein the polymeric material is a polycarboxylic acid, polyacrylic acid, polymethacrylic acid or a mixture thereof.
12. The filtrate material of claim 10 wherein the molecular weight of the poly acrylic acid is about 10,000 to 500,000.
14. The filtrate material of claim 4 wherein the polymeric structure is comprised of polyimine, polyamine, or polydiallyldimethyl ammonium chloride (DADMAC).
15. The filtrate material of claim 14 wherein the molecular weight of the polymer is about 500,000 to 1,000,000.
17. A method of making a filtrate material with ion exchange properties comprising: a) providing a porous, unagglomerated and unbound granular particle, b) blending said granulated particle with a polymer having ion exchange properties, c) crosslinking a portion of said polymer to adhere to the surface of said granular particle.
18. The method of claim 17 wherein the granular material is impregnated with said polymer.
19. The method of claim 17 wherein the granular particle is activated carbon.
20. The method of claim 17 further comprising the step of adding solvent to adjust the viscosity of the polymer to facilitate impregnation into the granular particle.
21. The method of claim 17 further comprising the step of adding a cross-linking agent selected from the group consisting of dicarboxylic acid, glutaric acid, succinic acid, and malonic acid.
23. The method of claim 17 further comprising the step of heating the filtrate material to further crosslink the polymer.
24. A method for treating liquid solutions comprising: a) providing a filtrate material wherein said filtrate material comprises a porous, unagglomerated and unbound granular material impregnated with a polymer that has ion exchange properties such that said polymer is immobilized on the surface of the granular material or impregnated in the granular material, and b) passing a liquid solution through said filtrate material.
25. The method of claim 24 wherein the granular particle is activated carbon.
26. The method of claim 24 wherein the polymer is a polycarboxylic acid, polyacrylic acid, polyimine, polyamine, polydialkyldimeththyl ammonium chloride (DADMAC), or a mixture of these.
32. The method of claim 24 further comprising the step of regenerating the filtrate material by contacting it with a concentrated acid solution to remove cationic metal impurities and flushing said filtrate material with water.
33. The method of claim 24 further comprising the step of regenerating the filtrate material by contacting it with a concentrated caustic solution to remove anionic metal impurities and flushing said filtrate material with water.
34. The filtrate material of claim 1, further comprising glycerine.
FIELD OF THE INVENTION
The present invention relates generally to carbon based, particulate materials useful for treating aqueous solutions. Also, this invention relates to a method for manufacturing carbon based, particulate material for use in treating aqueous solutions. More particularly, the present invention utilizes polymer impregnated, carbon based particulate material to remove dissolved metal and other ionic contaminants dissolved in aqueous solutions. The present invention also provides a method to impregnate carbon or other porous granular media of various sizes with polymeric ion exchange compounds, including polycarboxylic acid, polyamines, and polyimines in a manner which does not result in any agglomeration or binding of the granular particles together.
CROSS-REFERENCE TO RELATED APPLICATION
BACKGROUND OF INVENTION
The removal of metal contaminants and organic compounds from aqueous solutions, including water, is an increasingly important environmental concern. In addition to drinking water necessitating treatment, other sources of water such as acid mine drainage water, industrial waste water, and municipal waste water must all be treated. These water solutions may contain metal ions that need to be removed. Some of the metal ions that may be contained within the water are toxic, while other metal ions can be valuable. Thus, a need exists for a method by which quantities of water may be treated to remove the metal ion impurities and whereby such impurities may be collected. In addition to metal contaminants, examples of organic contaminants in drinking water which can be of concern include disinfectant by-products from chlorination, various pesticides, solvents, gasoline hydrocarbons, and numerous pharmaceutical compounds which can find their way into surface and ground waters.
Removal of metal ion impurities from water is often performed on an industrial scale by use of harsh chemicals. Use of chemicals to remove and recover toxic metal ions from aqueous solutions has been widespread. Such techniques include chemical precipitation, ion exchange, reverse osmosis, electrodialysis, solvent extraction (liquid ion exchange), and chemical deduction. (See U.S. Pat. No. 5,279,245). However, these procedures typically suffer the disadvantages of incomplete metal ion removal, high reagent and energy requirements, and generation of toxic sludge or other waste products that require disposal. Removal of organic contaminants involves the use of activated carbon and can include the processes outlined above.
Further, federally mandated cleanup standards require that effluents discharged to public waters generally contain less than 1 mg/L of metals such as copper, zinc, cadmium, lead, mercury and manganese. Thus, removal techniques must be efficient enough to remove the metal contaminants to ensure compliance with the federal regulations while remaining economically viable for municipalities. There are also US EPA regulations and guidelines for the treatment and removal of organic impurities.
Currently, there are numerous methods and materials used to remove metal ions from aqueous solutions. Typically, in potable and industrial water treatment, as well as waste water treatment, several types of granular media are currently used to aid in the removal or reduction of a broad spectrum of dissolved metals. Such metals include lead, cadmium, mercury, and arsenic, to name a few. These granular media are typically ion exchange resins in the form of polymeric beads. A few years ago, carbon based media was developed (U.S. Pat. No. 6,843,922) which used a polymeric binder with ion exchange capacity. One example of which was polycarboxylic acid (specifically polyacrylic acid, known as PAA) to agglomerate fine, activated carbon powder into larger granules. This allowed the filter media to have improved properties when compared to the then existing polymeric ion exchange beads without carbon, due to the surface area and sorbent capacity of the carbon itself.
Despite the improvements to the state of the art represented by U.S. Pat. No. 6,843,922, several problems with the use of activated carbon based, polymeric materials remain. Problems associated with this treatment media include poor structural integrity of the granule due to variation in the mixing and curing process. Also, there is a tendency for the binder to occlude the pores of the activated carbon. This reduces surface area and reduces the sorbent capacity of the carbon for other organic contaminants. Control of the resulting particle size after agglomeration is also difficult and necessitates additional steps to sort and potentially grind the resulting larger granules into more usable sizes.
Thus, there exists a need for a more effective method by which to remove metal ions in aqueous solutions. More specifically, there is a need for an activated carbon based particulate material that overcomes the problems in the current art. Namely, a need exists for an activated carbon based particulate material that does not necessitate additional processing to achieve a useable and effective size. Further, a need exists for an activated carbon based, particulate material that does not block the pores on the carbon thereby reducing the treatment effectiveness of the material. Still further, there exists a need for an improved method of manufacturing an activated carbon based, particulate material that is less expensive than current methods used in the art. It is these problems that the current invention overcomes by providing the ability to produce an activated carbon based metal reduction media through impregnation versus agglomeration. This results in superior contaminant reduction performance and structural integrity of the particles, with a far lower manufacturing cost. This economic advantage is achieved by eliminating the steps necessary to agglomerate fine powders and subsequently, grind or resize the media after production.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a new filtrate material and method for its manufacture. More specifically, the present invention provides a new method for manufacturing activated carbon based filtrate media used to remove dissolved metals and other organic contaminants from aqueous solutions. The present invention is based upon a novel process which allows the impregnation of activated carbon or other porous granular media of various types and sizes with polymeric ion exchange compounds. This new process allows the combination of the granular material and the ion exchange polymer to occur in a manner which does not result in any agglomeration or binding of the carbon particles together. This process of combination allows for more of the surface area of the coated porous carbon to be exposed than do conventional methods, without interfering with the other sorbent properties of the material.
The process proceeds without chemically binding the carbon particles to each other. Rather, the process traps the polymeric solutions in the carbon pore structure thereby retaining more of the surface area of the carbon for reacting with the waterborne contaminants, while effectively impregnating the carbon pore structure with the polymeric ion exchange material. Since there is no binding or agglomeration of the carbon, the ideal particle size of the carbon can be selected and utilized, and there are no issues with the structural integrity of the resulting particles. With very minimal effort, the substantial proportion (80-95+%) of original particle size in the end product can be realized. This represents a significant improvement over the prior art, and, specifically, over the teachings of U.S. Pat. No. 6,843,922, where considerable effort is needed in agglomeration and subsequent grinding and sieving to realize the desired particle size distribution. Moreover, various types of activated carbon can be used in the present invention, including coconut shell, bituminous, lignite, wood based, and bamboo. Further, various types of ion exchange polymers can be used as well, including those with either anionic or cationic properties.
In the most general terms, the present invention relates to a filtrate material for treating liquid solutions. The filtrate material or media is formed by a porous, granulated material. The granulated material is not agglomerated and does not experience binding of the particles together. The granulated material is combined with a polymer having ion exchange properties. More specifically, the present invention is a filtrate media wherein the granular particles are not chemically bonded to each other by the polymer.
Specifically, the present invention relates to a filtrate material where the polymeric ion exchange compounds are trapped inside the granular carbon pore structure. This trapping allows for the granular particle to continue to expose high levels of surface area despite being impregnated with the polymeric material and thus maintaining the intrinsic capacity of the activated carbon to remove organic contaminants. The present invention also contemplates use of polymeric material that has anionic or cationic properties.
The present invention contemplates and provides a filtrate material wherein the granular material can be activated carbons, titania, alumina, zirconia, iron oxides, zinc oxides, manganese sands, diatomeaceious earths, and clays, or any other sponge-like porous product with a large internal surface.
The present invention also provides and discloses a filtrate material for treating solutions that is made from a porous, unagglomerated and unbound granular material and a polymer. The polymer is impregnated within the granular material and has ion exchange properties.
The present invention also allows the ion exchange capacity of the impregnated filtrate material to be regenerated once the ion exchange capacity has been exhausted after contact with sufficient levels of dissolved waterborne metal contaminants. Once all of the ion exchange sites on the filtrate material have been saturated, and further ion exchange cannot occur, it is possible to regenerate the ion exchange sites by contacting the material with a 5% acid (HCL) solution (for cations), or caustic soda (NaOh) (for anions), followed by a water flush. This restores the ion exchange capacity of the filtrate material, which is once again capable of removing water soluble metal contaminants. This regeneration step allows the filtrate material to have extended life resulting in greater cost effectiveness. Once the ions are transferred to the acidic or basic solutions, they can be recovered, providing certain additional benefits for industries including mining. It should be appreciated that many acid solutions and caustic solutions can be used for regenerating the filtrate material, and the invention is not limited to hydrochloric acid and sodium hydroxide solutions.
The present invention is also directed to a method of manufacturing a filtrate material with ion exchange properties. The method includes providing a porous, unagglomerated and unbound granular particle and impregnating the particle with a polymer that has ion exchange properties. Once blended, the polymer is crosslinked in order to adhere the polymer to the surface of the granular particle. The present invention also contemplates blending the granular material and the polymer so that the granular particle is impregnated with the polymer. Further, the present invention contemplates adding a solvent to adjust the viscosity of the polymer to facilitate the impregnation into the macro and micropores of the granular particle. Further, the present invention contemplates adding a cross-linking agent to aid in cross-linking the polymer after impregnation of the granular material. The cross-linking agent can be selected from such cross-linking agents as dicarboxylic acid, glutaric acid, succenic acid, and malonic acid. Moreover, the present invention further contemplates adding the step of heating the filtrate material to further cross-link the polymer.
The present invention is also directed to a method for treating liquid solutions with a filtrate material. More specifically, the filtrate material is a porous, unagglomerated and unbound granular material, combined with a polymer that has ion exchange properties. The polymer is immobilized on the surface of the granular material or impregnated in the granular material. A liquid solution is passed through the filtrate material and metal and other impurities are removed from the solution. The present invention further contemplates that the granular particle is an activated carbon. The present invention also contemplates the step of recovering the metal and other organic impurities that are removed from the solution.
BRIEF DESCRIPTION OF THE DRAWINGS
There are no drawings associated with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
In the present specification, the terms sorb, sorbing, and sorption are used in the broad sense and as used herein are defined to include all forms of metal and other contaminant uptake and securing, whether by adsorption, absorption, ionic bonding (including ion exchange), among other forms of metal uptake and securing. Parts per million (ppm) and parts per billion (ppb) refer to parts by weight.
The main objective of the present invention is to coat, infuse and/or impregnate fine sized activated carbon particles with polymeric materials with ion exchange properties. The polymeric compounds have pendent end groups that are capable of imparting ion exchange properties. The present invention cross links these polymers in order to secure them to the surface substrate (the porous granular particles) and make them insoluble in water, using a suitable catalyst and/or high temperature. The filtrate material is ideally used as an additive in municipal water treatment facilities to remove heavy metals and organic contaminants, or as an additive in industrial applications where dissolved metals and organic contaminants are present in aqueous solutions.
Although this invention is specifically directed to activated carbon due to its ability to treat aqueous solutions, any high surface porous matrix and or fine particulate media can be used as the substrate. Examples of fine sized media that can be used include activated carbons, titania, alumina, zirconia, iron oxides, zinc oxides, manganese sands, diatomaceous earths, clays and various kinds of sponge-like porous products with large internal surface. Since after cross-linking the polymers are irreversibly immobilized on the surface substrate in a fine, spaghetti-like network, thus leaving the majority of the pores and surface of the underlying substrate exposed. This results in the substrate retaining its inherent properties to remove organic impurities but adds an ion exchange capability to the filtrate media. Such multi-functional capabilities are particularly valuable in consumer water treatment devices where there are space constraints. In a preferred embodiment, granulated, activated carbon (GAC) is used as the fine, particulate substrate.
The polymer used for creating cation exchange capacity for the substrate includes various polycarboxylic acids. In a preferred embodiment, polyacrylic acid (PAA) is used. However, polymethacrylic acid polymers can also be used. The molecular weight of the PAA should be 10,000 to 500,000. In a preferred embodiment, the molecular weight of the PAA should be 200,000 to 400,000. The cross linking catalyst is a polyalcohol, preferably glycerol. However, ethylene glycol, 1,2 propanediol, 1,3 propanediol, or polyvinyl alcohol can also be used.
The polymer used for creating anion exchange capacity for the substrate includes polyimine, polyamine, or polydiallyldimethyl ammonium chloride (DADMAC). The molecular weight of these polymers should be between 500,000 to 1.5 million. The cross liking agent should be a dicarboxylic acid. In a preferred embodiment, glutaric acid is used. However, succenic and malonic acid can also be used.
In a preferred embodiment, the optimum weight percentages on dry basis of granular activated carbon (GAC), polymer and crosslinking catalyst are as follows: 1) GAC: 60-80%, 2) Polymer: 20-40%, 3) Crosslinking Agent: 1-10% of polymer, and 4) Water: only as needed to assist impregnation.
The objective of cross linking the polymer is to bring about entanglement of polymer chains on the surfaces of and within the porosity of the substrate particles. This allows the polymers to be permanently secured to the surface of the granular particle. Care must be taken to not exceed the optimum amount of cross-linking early in the process because excessive polymer cross linking in the initial stages reduces the final ion exchange capacity. Thus, only a portion of the polymer needs to be cross-linked. Too much cross-linking early in the process is detrimental because it reduces the carboxylic acid and amine groups that are responsible for creating the ion exchange capacity. It has been found that a minimum amount of cross linking polymer should be added and is around 1% of the weight of polymer on a dry basis. Lower cross-linking at the early stage is acceptable since later on in the manufacturing process further cross linking is achieved by thermal treatment. Again, however, care must be taken because excess thermal treatment will also lead to the loss of ion exchange capacity.
In the following discussion describing the quantitative addition of polymeric solutions to the porous substrates, a preferred embodiment utilizing activated carbon as the example substrate will be used. It should be understood and readily apparent to those skilled in the art that similar substrates can also be used. Considerations regarding the quantities used for various additives will vary depending on the surface area of alternative substrates and their pore size and distribution.
Since the objective of the present invention is to impregnate the polymer solution into the surface pores of the substrate (activated carbon in the preferred embodiment), appropriate viscosity of the polymer solution must be ensured. If the polymer solution is too viscous to penetrate the surface pores of the substrate, water or other solvent can be added to the solution to lower the viscosity. Since the objective is to not occlude or cover the surface of the substrate, the percentage of polymer that is cross polymerized should be properly controlled. In the preferred embodiment, this quantity for activated carbon has been determined to be in the range of 5 to 40% by the weight of activated carbon. These amounts of cross polymerization will not alter the intrinsic properties of the carbon, such as the Iodine number (which indicates the adsorption capacity of activated carbon for organic molecules per unit weight of the carbon), yet will still impart the added property of ion exchange to the activated carbon filtrate media. As can be seen, the optimum loading of polymer will, therefore, vary depending on the nature of the porous material, its surface area, and pore size distribution. As one skilled in the art can readily appreciate, however, it is possible to undertake higher loading of cross polymerization on the substrate, provided that the main purpose to be achieved is to provide an anchor for the polymer and the intrinsic properties of the substrate are secondary in importance. Thus, on an inert porous substrate such as very fine manganese sand, one could go to much higher loading approaching 90-100% or more of the substrate weight.
The process of impregnating the activated carbon with the polymer solution initially requires adding polymer/cross linking catalyst solution of optimum viscosity to the carbon and thoroughly mixing the resulting paste. This can be achieved using either a sigma mixer, pin mixer, ribbon mixer, screw mixer with twin axis rotation, or any other means that ensures complete wetting of the substrate material by the polymer solution. Typically the polymer paste will have 25-50% solids at this stage, with the balance being a solvent such as water. Typical solvents can also include alcohols. After mixing, the paste is dewatered and subjected to thermal cross linking by raising it to sufficiently elevated temperature to bring about sufficient cross linking. This ensures that the polymer is permanently fixed on the substrate.
During the paste stage, the polymer impregnated mass undergoes a typical course of drying. The moisture or solvent is removed by exposure to an elevated temperature greater than 100° C. The paste is continually stirred and dries at a linear (constant) rate over time as the surface and subsurface moisture is removed. While drying, the consistency of the material changes from paste-like to granular. As the material becomes less paste-like and more granular, removal of moisture or solvent with time stops being linear, as the surface and subsurface moisture or solvent have been removed. Once this occurs, further moisture or solvent removal is limited by the rate of diffusion of moisture or solvent from the interior of granule. At the boundary of paste-like to granule stage, the material is at its viscosity maximum and offers the maximum resistance to stirring. As moisture or solvent removal continues, the rate of drying will slow down further as drying rate is limited by the diffusion of moisture or solvent from the interior of granules.
Despite any addition of additional heat, the temperature of the polymer impregnated carbon mass will not rise until all the solvent is removed. In order to get the optimum degree of cross linking, the temperature of the mass should reach 230-250° C. and must be held at that temperature for 1-2 hours. One of the telling characteristics of adequate cure or cross linking is the absence or minimum of swelling in the mass of the material when re wetted with water. When the carbon mass is rewetted with water, it should experience swelling of no more than 10% of its original mass. This indicates that the polymer has adequately cross-linked and has permanently adhered to the surface of the substrate. At this stage, no amount of repeated water contact will dislodge the polymer from the substrate, and its remaining carboxylic or amine groups impart permanent ion exchange capacity to the substrate.
To achieve this particular sequence of drying and curing (cross linking of polymer), various kinds of mechanical and electrical equipment can be used. For example, during the impregnation and forming of the paste, a sigma mixer, pin mixer, ribbon mixer, or screw mixer with two axis rotation may be used. In order to facilitate the removal of moisture, a vacuum can be used in conjunction with heat from an electrical, gas, or microwave source. In the granule stage, where initially the mass is in the form of big lumps or clods, various kinds of stirring and chopping means may be used to reduce the size of the lumps to powder. This will facilitate lowering the time required for removal of moisture and attainment of curing. Since the reduction of larger pieces of lumps or clod to smaller granules is essential to dewater, it is possible to take the paste and extrude it either in the form of spaghetti, thin sheets, pan-cakes, small brickettes, or pellets. Once extruded, the paste can be further subjected to thermal treatment for continued drying and curing. Also since the production of activated carbon is typically accomplished in rotating kilns, it is also possible to achieve the curing of the brickettes or pellets made from carbon-polymer mass in a rotating kiln.
The following examples illustrate various aspects of the present invention.
In a 150 liter volume ribbon blender a batch of polymer impregnated carbon was made using the following formulation: a) activated carbon (20×50 mesh): 10 kg, b) 25% PAA (Lubrizol-Carbopol-ISX-1794): 15 liters (4.28 kg dry basis), c) glycerol: 300 ml (0.33 kg), and d) water: 3 liters Activated carbon granules were loaded into the ribbon blender. In a separate reaction vessel, PAA, glycerol and water in the above quantities were mixed. This mixture was added to the granulated activated carbon (hereinafter "GAC") in the ribbon blender under continual agitation. The speed on the agitation was maintained at 20 rpm. The mixture (now in a paste-like form) was agitated for 30 minutes and dropped out of the ribbon blender onto a tray. The paste was extruded through a roller mill into one centimeter thick sheets on trays, and these trays were subjected to heat in a conveyor dryer at 230° C. The temperature of the paste-like material in the trays was measured using an infrared thermometer. The bed temperature remained below 100° C. until substantially all the moisture had evaporated. Once the moisture evaporated, the bed temperature began to rise. Once the temperature reached 230° C., the temperature was maintained 90 to 120 minutes. Afterwards, the cured sheets were broken into small pieces and put through a hammer mill. The material was processed in the hammer mill until it returned to its original 20×50 mesh size.
After curing, the PAA added 30% to the original weight of GAC. The theoretical yield based on the formulation above was 14.61 kg. The actual yield in the example was 14.1 kg, resulting in a 97% yield. The sieve analysis of the resultant coated GAC was as follows: a) Plus 20 mesh: 0%, b) Plus 25 mesh: 6%, c) Plus 30 mesh: 22%, d) Plus 40 mesh: 54%, e) Plus 50 mesh: 16%, and f) Minus 50 mesh: 2%. As clearly seen from the data, sieve analysis shows that 98% of the product was recovered in 20×50 mesh size. It should be noted that 20×50 mesh sized particles are exactly what was originally used to begin the process, and that the end result was that there was virtually no agglomeration or binding together of the particles. The cured product was put in a 1.5 cm diameter test tube to a depth of 1 cm. The height of the column was marked, and water was added to 75% the height of the test tube. Addition of water to the cured GAC generated rapid bubbles as the carbon became wetted. After a few minutes, the solids settled down very close to the original height mark. The swelling was measured to be less than 10%, indicating that the polymer was cured adequately. If the curing or cross linking was insufficient, the uncured PAA polymer chains would expand as they became hydrated, thus causing swelling of the column. The resultant product was tested by conventional methods for cation exchange capacity. The cation exchange capacity of the product was 0.6 meq/g. The untreated GAC did not have any cation exchange capacity.
A trial on impregnating GAC with PAA was conducted in a 130 liter volume Littleford Ploughshare Dryer (Littleford Day, Inc. P.O. Box 128, Florence, Ky. 41022-0128). This state-of-the-art dryer has a mechanically fluidized ploughshare action which agitates and individualizes each particle, thereby continuously exposing tremendous particle surface for drying. The vessel has a heated jacket where hot oil can be circulated to attain the temperatures of approximately 495° F. or 250° C. The particles constantly contact one another, and the heated interior wall of the jacketed Littleford vessel further hastens the drying process. Additionally, the Littleford Ploughshare dryer is equipped with independently-operated, high shear choppers that reduce the particle size of the lumps or agglomerates thereby exposing un-dried materials and ensuring that the particle interiors are thoroughly dried. Combined action of the ploughshare and choppers create a fluidized bed, shortening the drying time. Use of a vacuum further allows removal of moisture at lower temperature.
The 130 liter Littleford Ploughshare Dryer was used for the second trial. Formulations used in the second trial were: a) GAC 20×50: 25 kg, b) 25% PAA CBP-ISX 1794: 30 liters (33 kg), and c) glycerin: 0.085 kg. The 25 kg of GAC (20×50) was added to the Littleford reactor vessel. In a separate mixing vessel, the PAA and glycerol was mixed together. Once mixed, the PAA and glycerol were poured onto the GAC in the Littleford reactor vessel. The reactor top was closed sealing the reactor, and the vacuum was started at 30 inches. Agitation with the ploughshare was maintained at 75 to 85 rpm after the vessel was closed. Heated oil circulation was begun in the jacket with the temperature of oil maintained at 250° C. After 15 minutes of agitation, the resistance to ploughshare agitation increased and was noted from the amperage reading. For about 15 minutes the resistance became too high and threatened to exceed the maximum allowable amperage on ploughshare. As such, agitation was reduced to 10 rpm while continuing the temperature and vacuum on the vessel. Choppers were then used for 5 minutes to reduce the size of lumps and expose more surfaces to evaporation of moisture.
As soon as the material inside became drier and the resistance to agitation decreased, the ploughshare was set at 75 rpm. The product temperature was monitored. When the moisture was removed, the temperature started rising and rose to approximately 250° C. From this point onwards, small samples were taken out every 30 minutes for swelling testing utilizing the test described in Example 1. After the 2 hour point, the material was cured and swelling was determined to be less than 10%. The resultant product was tested by conventional methods for cation exchange capacity. The cation exchange capacity of the product was 0.55 meq/g. The untreated GAC did not have any cation exchange capacity.
Impregnated carbon made pursuant to the instant invention was tested for its ability to remove metallic contaminants such as lead, copper, cadmium, zinc, nickel, manganese, magnesium, chromium, and iron from water. The impregnated carbon was tested with the metal contaminants at both high concentrations (approximately 50 to 100 parts per million) and at low concentrations (wherein the concentrations of metal contaminants in the water were in the parts per billion range).
The impregnated carbon made according to the present invention was packed in a column. 100 bed volumes of metal solutions of low concentration, approximately 0.5 ppm (6.6 ppb for mercury (Hg)) at pH 7 were passed through the column. The filtrate was analyzed to determine the amount of metal reduction in the water. Table 1 shows the percent removal for various metals at low concentrations. Following the low concentration run, 100 bed volumes of metal solutions of high concentration, approximately 50 ppm (690 ppb for mercury (Hg)) at pH 7 were passed through the column. The filtrate was analyzed to determine the amount of metal reduction in the water. Table 2 shows the percent removal for various metals at high concentrations.
Polyacrylic acid impregnated carbon prepared according to the present invention was tested for metal removal using Rapid Small Scale Column Testing Protocol (RSSCT, as described in ICR Manual for Bench and Pilot Scale Treatment Studies (ICR, 1996)). The empty bed contact time used was 1 minute, and the hydraulic loading rate was 70 ml per sq. inch per minute. The influent concentrations for the metals were: a) lead: 85 ppb, b) cadmium: 100 ppb, c) zinc: 100 ppb, and d) copper: 100 ppb. The solution was maintained at a pH of 5.6. The respective graphs showing the reductions of various metals are shown in Tables 3-6. Along with the reductions in metal concentration achieved by the present invention, any reduction in metal concentrations by untreated carbon is presented for comparison. As can easily be seen in Tables 3-6, carbon without any treatment has very little capability to remove metals.
If one considers breakthrough as any effluent or filtrate concentration greater than zero contaminant level, then the reduction in respective bed volumes for various metals were: a) copper: 27,000, b) zinc: 1,400, c) cadmium: 12,500, and d) lead: 36,200. As seen in above examples, the impregnated activated carbon had a broad spectrum capability to remove metals.
In order to show that the intrinsic adsorption properties of the carbon had not changed after its impregnation with polyacrylic acid, an analysis of iodine number values was performed by titrations. Titrations were performed on both untreated and impregnated carbon. After correcting for the gain in weight due to the polyacrylic acid, the iodine numbers were determined to be 900 for untreated carbon, and 955 for polyacrylic acid impregnated carbon. Once experimental error is accounted for, these results indicate that that there is no significant change in the adsorption properties of the impregnated carbon.
As an example of regeneration, the column containing polyacrylic acid impregnated carbon as shown in Example 4 was treated with a 5% solution of hydrochloric acid (HCl) after it was saturated at 40,000 bed volumes of lead solution to regenerate the media. 100 bed volumes of 5% HCl were passed through the column at the rate of hydraulic loading of 70 ml per square inch per minute. Next it was flushed with water repeatedly until the filtrate of the effluent reached a pH of 6.5. The column was then ready to be reused with full ion exchange capacity restored.
Although the present invention has been illustrated and described herein with reference to preferred embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples can perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the invention and are intended to be covered by the following claims.
Patent applications by Arvind S. Patil, Davidson, NC US
Patent applications in class Including rehabilitating or regenerating exchange material or sorbent
Patent applications in all subclasses Including rehabilitating or regenerating exchange material or sorbent | <urn:uuid:71e9eaf7-6743-480c-bf31-9298dcbe4c63> | {
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versión On-line ISSN 1870-9044
Cross-language summarization is the task of generating a summary in a language different from the language of the source documents. In this paper, we propose a graph-based approach to multi-document summarization that integrates machine translation quality scores in the sentence extraction process. We evaluate our method on a manually translated subset of the DUC 2004 evaluation campaign. Results indicate that our approach improves the readability of the generated summaries without degrading their informativity.
Palabras llave : Graph-based approach; cross-language multi-document summarization. | <urn:uuid:0e99601b-6a4f-4263-b054-c41819f7b3d0> | {
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Date of Award
Doctor of Philosophy (PhD)
The kinetics of free-radical polymerization with and without crosslinking have been studied both theoretically and experimentally using methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) as a model system.
The mechanisms involved in the auto-acceleration of polymerization rate due to both chain physical entanglement and/or chemical crosslinking of polymerchains have been further elucidated using on-line electron spin resonance techniques (ESR). It was found that the observed radical trapping effect is associated with the conversion rate auto-acceleration phenomenon and that there exist two radical populations during the auto-acceleration period. The polymerization system is therefore heterogeneous with respect to the radical environment. The trapped radical fraction has been estimated by both post-effect measurement of radical concentration and deconvolution of the ESR signal. Crosslinking has been found to significantly enhance auto-acceleration and radical trapping. The radical concentrations found using large concentrations of crosslinker reach levels as high as 10⁻³ molar. The stability of the radicals trapped on the polymer network has been studied at temperatures up to 180ºC to assess the potential of the so-called reactive gels for various applications.
Radical concentrations versus time were measured by ESR for the copolymerization of MMA/EGDMA over the entire ranges of monomer composition and conversion. Together with conversion measurements, this provides a set of comprehensive kinetic data suitable for the estimation of individual rate constants for propagation, termination and also the initiation efficiency. It was found that these kinetic rate constants and the initiation efficiency fall simultaneously and dramatically when the polymerization system approaches its glass state. The free-radical gelation of MMA/EGDMA system under adiabatic conditions has also been investigated. These kinetic data permits severe testing of existing kinetic gelation models and suggest the need for further effort to develop more realistic models. For the theoretical work done in this thesis. the effort was directed to the development of more realistic kinetic models. Progress has been made in the following aspects: (1) A general method was developed to acount for chain-length dependent bimolecular terminatioll ofpolymer radicals for linear chain systems. With this method, there is no need to propose the full form of the bivariate distribution function which accounts for the dependence ofthe termination constanton the chain lengthsofterminatingpolymerradicals. (2) The Tobita-Hamielec kinetic model for free-radical polymerization with crosslinking was re-examined. The governing moment equations using the pseudo-kinetic rate constant method has been derived to include gel population and extended for asymmetric divinyl monomers.Anewsemi-statistical gelationmodel wasderived. Thismodel clearly illustrates the influenceofcrosslinkdensity distributiononotheraspectsofpolymernetworkformation. Problems in post-gelation modelling were addressed and discussed in terms of further development to provide a more realistic kinetic model. (3) A comprehensive kinetic model for the chemical modification of prepolymer in reactive processing using free-radical initiator has been derived. This model equationswhen solved give the full molecularweight distribution at different degrees of chain scission, long chain branching, crosslinking and grafting (processing time, type and level of initiator and additive). A general scheme for kinetic parameter estimation bas been also suggested.
Zhu, Shiping, "Advances in Free-Radical Polymerization Kinetics" (1991). Open Access Dissertations and Theses. Paper 3582. | <urn:uuid:9165e414-48be-4d64-8704-3bab1abe092e> | {
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Demand-based configuration of modular product architecture
A framework is presented for development of appropriately partitioned modular product architectures tailored both to market variance and to production economics. Beginning with a market assessment, product attribute requirements are arrayed to illustrate and derive priority ratings based on commonality and diversity in demand, and potential revenue from the respective clients. Market attribute information is converted to product specifications using existing methods in quality function deployment, with restrictions in areas of concern with this method, including the need for improved fidelity of product representation, and the validity of additive contribution of design parameters to satisfy design requirements. Candidate product architecture is then developed using existing methods in function-structure networks, with the function structure be developed first for the simplest complete product involving common high priority design parameters. Following this, features may be added to the network for variant products beginning with the externalities of the network that correspond to variant design attributes. Compatibility criteria are presented to merge the variant nodes and flows to the existing function structure network. This network construction technique is proposed as a more efficient alternative to current methods, which create a union network from complete networks of individual products. The product family architecture partitioning decision is conducted using existing heuristics for initial candidate module identification, aided by a new selection tool that considers the economics of production. This tool is used iteratively to groom the product family function-structure network architecture and aid selection decisions on module partitioning with the objective of profitably serving the greatest range of customers. The method concludes by transferring the component, interface, and partition data from the QFD and Function-structure formats into a detailed interface optimization problem, in a collaborative optimization construct. Examples are presented both for the optimization tool development and to illustrate the flow and translation of design information using this framework. ^
Engineering, Industrial|Engineering, Mechanical
Benoit George Gauthier,
"Demand-based configuration of modular product architecture"
Dissertations and Master's Theses (Campus Access). | <urn:uuid:870d7151-2b50-492e-a65b-2fbe4004f9bc> | {
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UNSPECIFIED (2005) Behaviour of high strength reinforced concrete beam with metakaolin under static loading. Masters thesis, Universiti Teknologi Malaysia, Faculty of Civil Engineering.
Restricted to Repository staff only
The need of cement replacement material (CRM) in reinforced concrete has gained its popularity among the researchers to produce a high strength concrete (HSC) for structural engineering application. This paper presents the experimental results of the static loading effect on reinforced concrete beam with metakaolin (MK7003). Three different percentages, 5%, 10% and 15% of MK7003 were incorporated as CRM in reinforced concrete beam, and 0% of MK7003 as the control specimen. Eight no of beams, with dimension of 1400mm x 150mm x 125mm, were tested, two for each different percentages and two beams as control specimens. The beams were subjected to four point loading test until failure. The findings of the experiment been shown that the structural performance were improved with the inclusion of MK7003. The observation made suggested that MK7003 with 10% replacement gave the optimum performance of the reinforced concrete.
|Item Type:||Thesis (Masters)|
|Additional Information:||Thesis (Master of Engineering (Civil - Structure)) - Universiti Teknologi Malaysia, 2005; Supervisor : Assoc. Prof. Dr. Abd. Latif Saleh|
|Uncontrolled Keywords:||Cement replacement material (CRM), Metakaolin, high strength concrete (HSC), structural behaviour|
|Subjects:||T Technology > TA Engineering (General). Civil engineering (General)|
|Deposited By:||Ms Zalinda Shuratman|
|Deposited On:||31 Oct 2007 07:08|
|Last Modified:||07 Aug 2012 06:27|
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Using parallelism in bufferless production lines can improve productivity, with significant productivity gains achieved with crossover. However, including crossover in the line implies additional material-handling requirements that may reduce the availability of the system. This paper examines if parallel systems with crossover between the stages are more productive than parallel systems without crossover between the stages, when one considers the availability of the additional material handling required for the crossover. The minimum material-handling availability necessary for inclusion of crossover is determined for a given parallel line's configuration such that productivity can be maximized.
Note to Practitioners-Two approaches in configuring parallel manufacturing lines are currently being used in industrial plants. These have been characterized as the Japanese approach of parallel independent cells of serial operations, and the European approach of a serial line with each operation being duplicated in parallel. The European approach has a productivity advantage over the Japanese approach when considering machine failures within each operation. However, the European approach requires more material handling which increases the configuration complexity and can reduce productivity. A math model is developed to determine which approach is best for a given line design when line length is defined by process planning and line balancing, and line width is determined by throughput requirements. The analysis is limited to cell configurations that do not use buffers internal to the cell.
Automation Science and Engineering, IEEE Transactions on (Volume:1 , Issue: 1 )
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The purpose of this paper is to explore dimensions that relate to training systems effectiveness in a number of industry categories. The training system is taken as part of the reproducer boundary subsystem within the organisation (Miller 1978). In particular this paper seeks to link the concept of the subsystem, namely the training system effectiveness to its environmental characteristics. This is an exploratory study. To my knowledge there is no research work that tests the relationship between the environmental characteristics and and the effectiveness of training systems. This research is in the same 'vein' as that of Lawrence and Lorch (1969), seeking answers to the elusive concept of organisational effectiveness and its relationship to the environment. | <urn:uuid:8a6a9ee8-36c4-4ac5-9d05-1ea73a18274a> | {
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Shape memory alloy actuators (SMA), thermostatic switch
This invention describes a way to decrease the temperature difference required for the SMA wire to fully actuate. The SMA wire actuates when it is heated from A
s (Austenite Start Temperature) to A f (Austenite Finish Temperature), which are both dependent on the stress applied to the wire. Higher stress increases both A s and A f, while lower stress decreases both. A negative differential spring displaced can decrease the As-Af temperature difference.
US Provisional Patent Application 61/569447 filed 12/12/2011
Last revised: April 4, 2012 | <urn:uuid:766be545-4ff8-45cc-ae55-f8e7e9031337> | {
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Metal Nano Dot (MND) memory
Company: Asahi® Glass Co., Ltd.
What They Say
“The MND memory is applied the deposition technology of MND film based on the synergy ceramic technologies possessed by Asahi Glass Co.”
“The new memory is an application of the formation technology on the ultra fine metallic structure embedded in insulator, which was derived through research into synergy ceramics, a national project in which Asahi Glass Co. has been involved.”
Last Updated 01/01/07 | <urn:uuid:0c77475e-4f99-4f04-b365-e6afedf6cdc0> | {
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ABSTRACT: Single bilayer membranes of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) were formed on micron thin-films of hydrophilized carbon nanotubes (CNT) by fusion of small unilamellar vesicles. The structure of the membrane was investigated using neutron reflectivity (NR). The underlying thin film of CNT was formed by chemical vapor deposition (CVD) in the presence of Fe catalyst, followed by reaction with 5 M nitric acid to render the film hydrophilic. We demonstrate that this platform lends support to homogeneous and continuous bilayer membranes that have promising applications in the fields of biomaterials, biosensors, and biophysics.
Langmuir 01/2007; 22(26):10909-11. · 4.19 Impact Factor | <urn:uuid:85ff4bfb-e2a7-4296-aaca-9453251ac7a8> | {
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The choice of parallel programming models and languages is a major factor in program performance and programmer productivity in HPC. However, evaluation of their relative merits is usually done based on conventional wisdom and subjective beliefs. We present a quantitative approach to evaluate such hypotheses statistically and validate them with empirical data. We apply this approach to compare two languages representing the message passing (MPI) and shared memory programming (UPC) paradigms. We formulate hypothesis tests for comparing the performance and productivity of these two models and evaluate them with data from observational studies of HPC programmers. We present and analyze several results, some of which are statistically significant, that demonstrate the promise of empirical evaluation in HPC development.
Date of Conference: 14-18 April 2008 | <urn:uuid:68b9d955-0471-43ba-9707-d77107db5dd3> | {
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Cloud computing is a computing paradigm which allows access of computing elements and storages on-demand over the Internet. Virtual Appliances, pre-configured, ready-to-run applications are emerging as a breakthrough technology to solve the complexities of service deployment on Cloud infrastructure. However, an automated approach to deploy required appliances on the most suitable Cloud infrastructure is neglected by previous works which is the focus of this work. In this paper, we propose an effective architecture using ontology-based discovery to provide QoS aware deployment of appliances on Cloud service providers. In addition, we test our approach on a case study and the result shows the efficiency and effectiveness of the proposed work.
Date of Conference: 17-20 May 2010 | <urn:uuid:058c677f-c2eb-41ca-aef4-7ae5b3d74e74> | {
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Scientific Grand Challenge
The LMI-EFRC is dedicated to expanding the scientific knowledge base for fundamentally photonic principles and mechanisms in solar energy conversion.
An important set of requirements of photonic materials for solar energy conversion are related to the characteristics of the sun as a light source – it is a broadband and unpolarized light source, and the achievable conversion efficiency for non-tracking converters must be reasonably independent of light incidence angle.
To improve energy conversion efficiency with photonic design and materials requires the simultaneous development of theoretical methods (new photonic principles, mathematical methods, electromagnetic designs and computational approaches) and experimental methods (synthetic methods for nano- and micro-scale fabrication of materials with controlled refractive index profiles and complex two- and three-dimensional architectures). The confluence of these new photonic methods, the performance requirements for solar energy conversion and scientific opportunity has framed the challenges that define the research groups in the LMI-EFRC:
Full Spectrum Photon Conversion
Optics for Spontaneous Emission and Absorption Enhancement
Transformation Optics for Photovoltaics
Complex Architecture and Self-Architected Absorbers | <urn:uuid:1146d4e8-e0e6-467e-8422-f67a74e0b26f> | {
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Click Image to Enlarge
NC program optimization software analyzes cutting forces on a tool for the entire tool path. It automatically optimizes feed rate when those forces exceed or are well below peak tangential force parameters to maximize tool performance and shorten cycle time. This comparison of tangential forces generated before and after feed rate optimization demonstrates the concept.
Bell Helicopter’s Drive Systems Center (DSC) machines more steel than titanium for the aircraft transmission and gearbox assemblies it manufactures. However, a tricky titanium component prompted Bell’s DSC to investigate whether NC program optimization technology would shorten cycle times and unlock capacity on existing equipment as it did for fellow Textron subsidiary, Cessna. Bell’s goal was to reduce manufacturing time, thereby lowering overall costs to its customers.
DSC, located in Grand Prairie, Texas, knew about Cessna’s successes optimizing a number of its part programs using machining process modeling software from Third Wave Systems. Chris Mueninghoff, NC programming supervisor at DSC, says a titanium forging for a commercial application proved to be the ideal test part for Third Wave Systems’ AdvantEdge Production Module software. That’s because the part is one of the most challenging ones Bell machines. Nearly 30 percent of the titanium forging has to be machined away to complete the part, representing more material removal than most other components at Bell. The carrier measures 16 inches in diameter and 6 inches tall.
The Production Module software integrates CAD, CAM, machine dynamics and workpiece material properties as it analyzes machining operations on a given part. As Mr. Mueninghoff explains, the optimization process starts by importing a 3D model of the part and its corresponding machining program. The cutting tools used for each operation are defined by key characteristics such as rake angle, helix angle and tool material. Information about the machine tool and setup is entered, too, including machine horsepower and torque as well as fixture rigidity and cutting force limits. Finally, workpiece material is selected from the software’s database.
The software uses this information to predict the cutting forces tools will experience along their entire tool path. These forces will fluctuate during a cutting operation primarily due to parameters such as feed rate, tool orientation and workpiece material. To optimize each operation, the software compares the calculated force at each line of the original G-code against upper and lower force limits. It then automatically increases or reduces the feed rate accordingly. For example, when force values are well below a defined upper limit, the feed rate is increased to a stable point below the maximum accepted force a tool can experience. This results in not only faster cutting, but also more balanced cutting tool forces. (The graph on the previous page shows typical results of this process balancing for a titanium part.) The software analyzes and generates the modified G-code with new feed rates in 10 to 15 minutes, depending on part complexity, Mr. Mueninghoff says.
Bell validates each modified part program by machining an actual part and sending it through all normal inspection procedures to verify that the modified program will not damage the workpiece, machine tool or cutters. The cycle time for the titanium test part was reduced by 30 percent after process optimization. Since that original test, Bell has used the NC optimization software on approximately 250 components, many made of hardened steel alloys. Most recently, Bell’s NC program optimization efforts have come full-circle to titanium. It refined a program to machine a larger titanium carrier used on the V-22 Osprey tilt-rotor aircraft. These carriers were produced in a two-machine cell. Because Production Module software reduced cycle times for these parts by 25 to 30 percent, however, Bell was able to shift all production to a single machine.
Mr. Mueninghoff says the NC program optimization software has also lead to two other side benefits. One is better cutting tool life and wear resistance. The other is the generation of better overall parts. It’s important to gearbox component designers that Bell limits the amount of fatigue and stress introduced into parts during machining. The optimization software allows Bell to show that it is able to reduce component cycle times without applying techniques that could potentially decrease the life of a key component. In fact, Mr. Mueninghoff notes that DSC is actually putting less stress into the part during machining, ultimately resulting in a higher-quality part.blog comments powered by Disqus | <urn:uuid:1e71d27e-cf89-4f3e-89a8-9d99b59aeaad> | {
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ABSTRACT: Flash ladar systems are compact devices with high frame rates that hold promise for robotics applications, but these devices suffer from poor spatial resolution. This work develops a wavelet preprocessing stage to enhance registration of multiple frames and applies super-resolution to improve the resolution of flash ladar range imagery. The triangle orientation discrimination methodology was used for a subjective evaluation of the effectiveness of super-resolution for flash ladar. Results show statistically significant increases in the probability of target discrimination at all target ranges, as well as a reduction in subject response times for super-resolved imagery.
Applied Optics 02/2010; 49(5):772-80. · 1.41 Impact Factor | <urn:uuid:f48cbb16-f5b8-426d-abff-598fa74e8603> | {
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As data and computational grids grow in size and complexity, the crucial task of identifying, monitoring and utilizing available resources in an efficient manner is becoming increasingly difficult. The design of monitoring systems that are scalable both in the number of sources being monitored and in the number of clients served is a challenging issue. In this paper we investigate the trade-offs of different polling strategies that can be used to monitor resource availability on machines in a distributed environment. We show how adaptive polling protocols can substantially increase scalability with a less than proportional loss of precision, and how these protocols can be personalized for different types of resource usage patterns.
Date of Conference: 22-24 June 2003 | <urn:uuid:d863f681-3d17-4959-9787-b5599e992282> | {
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Type of Document Master's Thesis Author Das, Sanchoy K. URN etd-11142012-040019 Title Selection of an optimal set of assembly part delivery dates in a stochastic assembly system Degree Master of Science Department Industrial Engineering and Operations Research Advisory Committee
Advisor Name Title Sarin, Subhash C. Committee Chair Malmborg, Charles J. Committee Member Sherali, Hanif D. Committee Member Keywords
- Production scheduling
Date of Defense 1985-06-05 Availability restricted Abstract
The scheduling of material requirements at a factory to maximize profits.or productivity is a difficult mathematical problem. The stochastic nature of most production setups introduces additional complications as a result of the uncertainty involved in vendor reliability and processing times. But in developing the descriptive model for a system, a true representation can only be attained if the variability of these elements is considered.
Here we present the development of a normative model based on a new type of descriptive model which considers the element of stochasticity. The arrival time of an assembly part from a vendor is considered to be a normally distributed random variable. We attempt to optimize the system with regard to work-in-process inventory using a dynamic programming algorithm in combination with a heuristic procedure. The decision variable is the prescribed assembly part delivery date. The model is particularly suitable for application in low volume assembly lines, where products are manufactured in discrete batches.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access LD5655.V855_1985.D37.pdf 4.82 Mb 00:22:19 00:11:29 00:10:02 00:05:01 00:00:25next to an author's name indicates that all files or directories associated with their ETD are accessible from the Virginia Tech campus network only.
If you have questions or technical problems, please Contact DLA. | <urn:uuid:e07246ce-a607-40f1-a3d3-019146de5f56> | {
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Zhang, Yizhen (2006) Engineering design synthesis of sensor and control systems for intelligent vehicles. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05252006-221412
This thesis investigates the application of formal engineering design synthesis methodologies to the development of sensor and control systems for intelligent vehicles.
A formal engineering design synthesis methodology based on evolutionary computation is presented, with special emphasis on dealing with modern engineering design challenges, such as high or variable complexity of design solutions, multiple conflicting design objectives, and noisy evaluation results, etc. The efficacy of the evolutionary design synthesis method is validated through multiple different case studies, where a variety of novel design solutions are generated to represent different engineering design trade-offs, and they have achieved performances comparable to, if not better than, that of hand-coded solutions in the same simplified environment. More importantly, this automatic design synthesis method shows great potential to handle more complex design problems, where a good hand-coded solution may be very difficult or even impossible to obtain. Moreover, the evolutionary design synthesis methodology appears promising to deal with uncertainty in the problem efficiently and adapt to the collective task nature well.
In addition, multiple levels of vehicle simulation models with different computational cost and fidelity as well as necessary driver behaviors are implemented for different types of simulation experiments conducted for different research purposes. Efforts are made to try to generate good candidate solutions efficiently with less computational time and human engineering effort.
Furthermore, a new threat assessment measure, time-to-last-second-braking (Tlsb), is proposed, which directly characterizes human natural judgment of the urgency and severity of threats in terms of time. Based on driver reaction time experimental results, new warning and overriding criteria are proposed in terms of the new Tlsb measure, and the performance is analyzed statistically in terms of two typical sample pre-crash traffic scenarios. Less affected by driver behavior variability, the new criteria characterize the current dynamic situations better than the previous ones, providing more appropriate warning and more effective overriding at the last moment. Finally, the possibility of frontal collision avoidance through steering (lane-changing) is discussed, and similarly the time-to-last-second-steering (Tlss) measure is proposed and compared with Tlsb.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Subject Keywords:||collision warning; evolutionary robotics; last-second braking; neural network; sensor evolution; Webots simulation|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Mechanical Engineering|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||3 May 2006|
|Author Email:||yizhen (AT) caltech.edu|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||01 Jun 2006|
|Last Modified:||26 Dec 2012 02:46|
- Final Version
See Usage Policy.
Repository Staff Only: item control page | <urn:uuid:987252f3-cc3b-4019-b3a2-b5f227074687> | {
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Calculation of solid-fluid phase equilibria for ...
|Title||Calculation of solid-fluid phase equilibria for systems of chain molecules|
|Author(s)||J. Polson, D. Frenkel|
|Journal||Journal of Chemical Physics|
|Abstract||We study the first order solid-fluid phase transition of a system of semi-flexible Lennard-Jones chains using molecular dynamics simulations. Thermodynamic integration methods are used to calculate the free energy of the solid and fluid phases. The solid phase free energy per chain can be calculated to an accuracy of +/-0.03k(B)T with relative ease. The Gibbs-Duhem integration technique is used to trace out the complete melting curve, scarring with a single point on the curve obtained from the foe energy calculations. For the short chains studied here, we find that increasing the chain length stabilizes the solid phase; i.e., it raises the melting temperature at fixed pressure, and lowers the density at the transition at fixed temperature. Gibbs-Duhem integration was used also to investigate the effects of chain stiffness on the transition. We find that increasing the stiffness also acts to stabilize the solid phase. At fixed temperature, the transition is shifted to lower pressure and lower density with increasing chain stiffness. Further, we find that the density gap between solid and fluid broadens with increasing chain stiffness. (C) 1998 American Institute of Physics. [S0021-9606(98)50825-2].|
Using APA 6th Edition citation style.
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A possible source for compatibility information is:
Polycarbonate pipe is fabricated either by extrusion or by forming sheet material and welding the seam. Extruded polycarbonate pipe is much stronger than formed polycarbonate pipe but formed polycarbonate is the product of choice when:
- Only low pressure is involved
- The diameter is larger that the available extrusions
- The quantity required is small
- The impact strength of polycarbonate is important.
Polyfab uses extruded polycarbonate pipe in many fabrications but we do not manufacture it.
We roll custom polycarbonate pipes, cylinders and cones for many applications including food handling using FDA approved materials, experimental apparatus for petroleum and biotech applications.
Contactor experimental apparatus designed by Chevron Chemical Company and manufactured for the University of Oklahoma. The stainless steel internal structure was fabricated by others. | <urn:uuid:58fbdd62-fcc5-4429-83d7-3d707828d368> | {
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Hudson, John Matthew (1994) Specular and diffuse X-ray scattering studies of surfaces and interfaces. Doctoral thesis, Durham University.
The behaviour of thin film semiconducting and magnetic devices depends upon the chemical and physical status of the as-grown structure. Since the dimensions of many devices can be in the Angstrom and nanometre region, characterisation techniques capable of measuring chemical and physical parameters in this regime are necessary if an understanding of the effect of specimen structure on observed properties is to be achieved. This thesis uses high resolution x-ray scattering techniques to characterise sub-micron layered structures of semiconducting and magnetic materials. Double crystal diffraction is routinely employed in the semiconductor industry for the on line inspection of sample quality. While material parameters such as sample perfection and layer composition may be rapidly deduced, the non-destructive measurement of layer thickness is more difficult (particularly for multilayered samples) and lengthy simulation procedures are often necessary to extract the thickness information from a double crystal diffraction profile. However, for semiconductor structures which act as Bragg case interferometers, oscillations (known as thickness fringes) appear in the diffracted profile. The period of these fringes can be directly related to layer thickness. Attempts to Fourier transform diffraction data, in order to automatically extract the frequency" of thickness fringes, have previously been only partially successful. It is shown that the relatively weak intensity of the thickness fringes and the presence of the substrate peak in the analysed diffraction data, drastically reduce the quality of the subsequent Fourier transform. A procedure for the manipulation of diffraction data is suggested, where an "average” envelope is fitted to the thickness fringes and used to normalise the data. The application of an auto-correlation is shown to further increase the quality of the Fourier transform of the normalised data. The application of Fourier transform techniques to the routine analysis of double crystal diffraction data is discussedA novel technique for the measurement of absolute lattice parameters of single crystals is presented, which is capable of determining lattice constants with an absolute accuracy of around 2 parts in 10(^5). The technique requires only the use of a conventional triple crystal diffractometer with motorised 20 circle movement and the provision for a fine, precise rocking motion of the analyser. To demonstrate the technique, exemplary measurements on GaAs and InAs crystals are presented. Triple crystal diffi-action analysis has been performed on three material systems of current technological interest; the Hg(_1-x)Mn(_x)Te on GaAs, the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_1-x)Zn(_x)Te and the low temperature grown GaAs systems. Studies on the Hg(_1-x)Mn(_x)Te on GaAs system reveal that the principal contribution to the rocking curve widths of layers grown using the direct alloy growth (DAG) method, arise from the tilt (i.e., mosaicity) of layer sub-grains. This finding is confirmed by double crystal topography which shows that the layers are highly mosaic with a typical grain size of (130±5)µm. Topographic studies of Hg(_1-x)Mn(_x)Te on GaAs, grown using the interdiffused multilayer process (IMP), show that sample quality is significantly improved with single crystal material being produced using this growth method. Triple crystal diffraction studies of the Cd(_1-x)Hg(_x)Te on CdTe/Cd(_0.96)Zn(_0.04)Te systems reveal several findings. These are that the main contribution to rocking curve widths is from lattice tilts and that the tilt distribution increases as the layer thickness decreases. Further, the quality of the Cd(_0.96)Zn(_0.04)Te substrate analysed is superior to that of the CdTe and that Cd(_1-x)Hg(_x)Te layers grown on Cd(_0.96)Zn(_0.04)Te substrates are generally of a higher quality than those grown on CdTe. Triple crystal analysis of MBE and ALE grown GaAs films, deposited at low growth temperatures, show that, at equivalent temperatures, superior quality films are grown by the ALE technique. Narrow lattice dilation and tilt distributions are reported for GaAs films grown at temperatures as low as 300ºC by the ALE method. While diffraction techniques are highly suitable for the study of relatively perfect crystalline material, they are not appropriate to the analysis of heavily dislocated or even amorphous specimens. This is not the case for the Grazing Incidence X-Ray Reflectivity (GIXR) technique, whose sensitivity is not dependent upon sample structure. The GIXR technique is currently attracting increasing interest following the development of commercial instruments. In this thesis, GIXR has been used to probe the layer thickness and interfacial roughness of a series of magnetic multilayer samples and Si/Si(_x)Ge(_1-x) superlattices. The technique is shown to be capable of measuring layer thickness to an accuracy of one monolayer. Modelling of specular GIXR data for the Si/Si(_x)Ge(_1-x) superlattices has shown that the magnitude of interfacial roughness is different for the two types of interface within the high Ge content superlattice samples, the Si(_x)Ge(_1-x)→Si interface possessing a long range sinusoidal roughness of (0.9±0.3)nm, in addition to die short range roughness of (0.5±0.2)nm present at all interfaces. By collecting the diffuse scatter from a GIXR experiment, conformal, or correlated, roughness has been observed in both the multilayer and superlattice samples.
|Item Type:||Thesis (Doctoral)|
|Award:||Doctor of Philosophy|
|Copyright:||Copyright of this thesis is held by the author|
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Skip to Main Content
Today a massive amount of information available on the WWW often makes searching for information of interest a long and tedious task. Chasing hyperlinks to find relevant information may be daunting. To overcome such a problem, a learning system, cognizant of a user's interests, can be employed to automatically search for and retrieve relevant information by following appropriate hyperlinks. In this paper, we describe the design of such a learning system for automated Web navigation using adaptive dynamic programming methods. To improve the performance of the learning system, we introduce the notion of multiple model-based learning agents operating in parallel, and describe methods for combining their models. Experimental results on the WWW navigation problem are presented to indicate that combining multiple learning agents, relying on user feedback, is a promising direction to improve learning speed in automated WWW navigation.
Systems, Man and Cybernetics, Part A: Systems and Humans, IEEE Transactions on (Volume:33 , Issue: 3 )
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The paper considers the problem of robust control redesign of a class of linear discrete-time systems with norm-bounded parametric uncertainties and controller-gain perturbations. In both cases of additive and multiplicative perturbations, the control objective is to design a resilient feedback-stabilisation schemes using guaranteed cost control and H∞ control approaches. The problem under consideration is cast as convex optimisation over linear matrix inequalities which led to the derivation of necessary and sufficient conditions for closed-loop robust quadratic stability. Three system examples are provided to illustrate the theoretical developments.
Control Theory and Applications, IEE Proceedings - (Volume:152 , Issue: 4 )
Date of Publication: 8 July 2005 | <urn:uuid:b4584a83-f525-4fa1-bd03-84bac929afe7> | {
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