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2010-04-01
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The paper deals with stress analysis, cyclic and creep life prediction of a cryogenic rocket engine thrust chamber, being used in one of the satellite launch vehicles of ISRO. The thrust chamber is of double walled construction wherein high conductivity copper alloy is used for the inner wall and stainless steel for the outer. Regenerative cooling of the chamber is achieved by passing the fuel through rectangular coolant passages milled on outer surface of the inner wall. The inner and outer walls are bonded together by brazing at high temperature. Failure of a double walled chamber occurs due to thinning of the inner wall and bulging into the chamber due to three mechanisms viz. (i) low cycle fatigue (ii) thermal ratchetting and (iii) creep. To capture the structural behaviour of the chamber in a complete sequence of operation of the engine, axisymmetric modeling and cyclic stress analysis is carried out using the ANSYS finite element analysis software package. High temperature mechanical properties, low cycle fatigue and creep properties of copper are characterised. Results of creep tests conducted at various temperatures are utilized for evaluating creep constants of Norton secondary creep model available in ANSYS. Analysis is performed in a seven load step sequence simulating one complete hot test of the engine. Life prediction is done using the cumulative damage accumulation methodology, considering the above three damage mechanisms. Allowable number of hot runs permissible is then arrived at after assigning suitable factors of safety for each damage mode.
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Stress analysis & life prediction of a cryogenic rocket engine thrust chamber considering low cycle fatigue, creep and thermal ratchetting
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10.1007/s12666-010-0089-7
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2010-03-01
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The design of a facility for studying luminescence of cryogenic liquids (nitrogen and helium) is described. Luminescence is excited by ∼0.573-MeV β particles and 0.656-MeV positrons emitted by a radioactive source based on ^64Cu radionuclide, which is immersed in a liquid.
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A facility for studying luminescence of cryogenic liquids excited by β particles and positrons from ^64Cu radionuclide
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10.1134/S0020441210020302
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2010-03-01
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A procedure for the prediction of the load-carrying ability of unidirectional-fiber reinforced composite laminates is presented, which is based on a structural-phenomenological model developed of the degradation of layer elastic constants during deformation and takes into account the presence of heat stresses and temperature dependences of the thermomechanical characteristics of layer. The efficiency of the procedure has been confirmed by the results of tests of carbon laminates with different reinforcement schemes both at room temperature and at cryogenic temperature.
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Determination of the load-carrying ability of reinforced plastic laminates with allowance for the degradation of mechanical parameters of individual layers
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10.1007/s11223-010-9209-1
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2010-03-01
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Cryogenics is an exciting, important and inexpensive technique that already has led to main discoveries and holds much future assurance. Cryogenic processing is the treatment of the materials at very low temperature around 77 K. This technique has been proven to be efficient in improving the physical and mechanical properties of the materials such as metals, alloys, plastics and composites. It improves the wear, abrasion, erosion and corrosion resistivity, durability and stabilizes the strength characteristics of various materials. Cryogenic refines and stabilizes the crystal lattice structure and distribute carbon particles throughout the material resulting a stronger and hence more durable material. In present paper, we have reviewed the effect of cryogenic treatment on some metals, alloys, plastics and composites.
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Cryogenic Processing: A Study of Materials at Low Temperatures
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10.1007/s10909-009-0058-x
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2010-03-01
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We present the measurements and the analysis of nonlinearity of Ge- and InGaAs-photodiodes responsivity measured at high irradiance levels (up to ∼ 90 mW / mm^2) in the near infrared. The nonlinearity was measured using a fiber-optics-based setup which employs the Differential Spectral Responsivity (DSR) technique. The measurements of the nonlinearity were carried out at different laser beam diameters with fiber optic attachment as well as open-beam. All photodiodes investigated present a nonlinarity of the saturation type, which depends on the beam diameter of the radiation source.
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Measurement of the nonlinearity of Ge-and InGaAs-photodiodes at high irradiance levels
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10.1007/s12647-010-0008-8
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2010-02-01
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This experimental study investigates the wear resistance improvement in En 52 and 21-4N valve steels through shallow and deep cryogenic treatment using a reciprocatory friction and wear monitor as per the ASTM standard G-133. It has been observed that the wear resistance of En 52 and 21-4N has improved by 81.15% & 13.49% respectively, due to shallow cryogenic treatment, 86.54% & 22.08% respectively, due to deep cryogenic treatment, when compared to the conventional heat treatment. The microstructural study suggests that the improvement in wear resistance and hardness is attributed to the conversion of retained austenite into martensite, along with precipitation and distribution of the carbides brought in by the cryogenic treatment.
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Wear resistance enhancement in cryotreated En 52 and 21-4N valve steels
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10.1007/s12541-010-0012-5
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2010-02-01
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The method of automated analysis of electron backscatter diffraction (EBSD) patterns has been employed for the characterization of the structure of copper obtained using severe plastic deformation by shear under high pressure under cryogenic conditions. It has been established that severe cryogenic deformation leads to a considerable refinement of the structure to a grain size of 0.2 μm. Based on an analysis of the texture data and misorientation spectrum, it has been concluded that it is the 111<110> dislocation slip that was the main mechanism of plastic flow and that the contribution from twinning was very small. It has been shown that the evolution of the grain structure was mainly determined by elongation of initial grains in the direction of macroscopic shear and their subsequent fragmentation.
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Severe cryogenic deformation of copper
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10.1134/S0031918X10020092
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2010-02-01
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Control of cryogenic propellant tank pressure during tank refueling and expulsion in low gravity is an important technical challenge to overcome for future long duration missions in space. One method proposed to control tank pressurization involves the use of jet-induced geysers. Two-dimensional computational models have been developed and used with limited success in previous efforts to predict geyser heights in microgravity. A three-dimensional flow simulation is used to model jet-induced geysers in reduced gravity. Geyser flows are commonly characterized by the presence of turbulent jets, transient flow, deforming free surfaces, and surface tension effects. As is the case for many turbulent flow applications, accuracy in simulating complex turbulent flows is critically dependent on the selection of a suitable turbulence model. The sensitivity of the simulation geyser predictions to a suite of popular turbulence models is assessed. Simulation results are compared to available experiment results. By expanding upon the work already completed, the model is used to simulate a broad range of cases within the experiment test matrix. Simulation results suggest the two dimensional simulation using the k- ε turbulence model provides the most accurate results for jet-induced geysers in reduced gravity when compared to available experiment data.
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Simulation of Jet-Induced Geysers in Reduced Gravity
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10.1007/s12217-008-9095-3
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2010-01-01
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In this paper, a novel ice bonded abrasive polishing process proposed for producing ultrafine surfaces on metallic surfaces is presented. Ice bonded abrasive polishing setup was developed for conducting the experiments under cryogenic conditions. The novelty of the process lies in the method of preparing a cryogenic polishing tool by freezing a mixture of distilled water and ultrafine abrasive particles with suitable cryogenic fluids. Characterization of the tool, by mass balance method, ensured uniform distribution of abrasives throughout the ice matrix. Experiments were conducted on 304L stainless steel in order to examine the improvements in surface finish on work surfaces. Experimental studies have revealed the generation of ultrafine surfaces, yielding roughness values in nanometric range, with the adhesive action of ice and the abrasive action of material by fine abrasive particles.
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Ultra-fine Finishing of Metallic surfaces with Ice Bonded Abrasive Polishing Process
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10.1007/978-1-84996-432-6_24
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2010-01-01
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A wind–tunnel experiment on laminar-turbulent transition has been performed in ETW (the European Transonic Wind Tunnel in Koln) at high Reynolds number and cryogenic conditions. The studied geometry is a sting mounted full model in swept–wing configuration. The transition location was determined by means of Temperature Sensitive Paint (CryoTSP). The experimental observations were further analysed using different transition prediction tools, based on linear stability theory.
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High Reynolds Number Transition Experiments in ETW (TELFONA project)
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10.1007/978-90-481-3723-7_98
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2010-01-01
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The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures of 10–50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the IBR-2M reactor and to obtain the cold neutron yield as a function of the moderator temperature. Satisfactory agreement between the experimental and calculated neutron spectra at a mesitylene temperature of 20 K has been obtained; the ratio of cold neutron intensities at 10 and 50 K is ∼1.8.
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Measurement of cold neutron spectra using a model cryogenic moderator of the IBR-2M reactor
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10.1134/S1547477110010127
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2010-01-01
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The ultimate detection performance of HgCdTe, quantum well (QW) and extrinsic Si detectors under low temperatures is analyzed. The theoretical limits of the internal photon response for the three detectors are compared. The materials of space-based detectors in space tracking and surveillance system (STSS) are discussed. The results show that among three detectors, the best performance can be obtained from HgCdTe detectors under 40 K in the mid-long wave infrared (MLWIR) and long wave infrared (LWIR) spectral regions. Its ultimate detectivity in the MLWIR spectral region, with a cutoff wavelength of 8 μm, is on the order of 1×10^18 cm·Hz^1/2/W. And that in the LWIR spectral region, with cutoff wavelengths of 12 μm, 16 μm and 20 μm, is on the order of 1×10^15 cm·Hz^1/2/W, 1×10^14 cm·Hz^1/2/W and 1×10^13 cm·Hz^1/2/W, respectively.
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Detector material and sensitivity analysis for space-based infrared sensors
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10.1007/s11801-010-9008-8
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2010-01-01
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The fast ignition scheme is one of the most fascinating and feasible ignition schemes for the inertial fusion energy. At ILE Osaka University, FIREX (Fast Ignition Realization Experiment) project is in progress. Implosion experiments of the cryogenic target are scheduled in near future. There are two key issues for the fast ignition. One is controlling the implosion dynamics to form high density core plasma in non-spherical implosion, and the other is heating the core plasma efficiently by the short pulse high intense laser. The time and space scale in the fast ignition scheme vary widely from initial laser irradiation to solid target, to relativistic laser plasma interaction and final fusion burning. The numerical simulation plays an important role in demonstrating the performance of the fast ignition, designing the targets, and optimizing laser pulse shapes for the scheme. These all the physics are desired to be self-consistently described. In order to study these physics of FI, we have developed “Fast Ignition Integrated Interconnecting code” (FI3), which consists of collective Particle-in-Cell (PIC) code (FISCOF1D/2D), Relativistic Fokker-Planck with hydro code (FIBMET), and two-dimensional Arbitrary-Lagrangian-Eulerian (ALE) radiation hydrodynamics code (PINOCO). Those codes are sophisticated in each suitable plasma parameters, and boundaries conditions and initial conditions for them are imported/exported to each other by way of DCCP, a simple and compact communication tool which enable these codes to communicate each other under executing different machines. The feature of the FI3 code, and a numerical result of integrated simulation are shown. This simulation system can be applied for particle acceleration and other applications.
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Multi-scale Simulations for Laser Plasma Physics
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10.1007/978-3-642-03913-3_19
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2010-01-01
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Traditional polymer forming methods have concentrated on moulding technology. CNC Machining of a low-density material, such as an elastomer even at significantly reduced temperatures presents a number of challenges, with one being the generation of a machining phenomenon termed adiabatic shear band formation. As a result of this, tool degradation and increased part surface roughness can occur. The adiabatic shear band formation is a region on a chip where the ductile properties of the material being machined have been exceeded and the heat generated does not have sufficient time to dissipate. This leads in some cases to permanent material damage resulting in reduced fatigue resistance. With the machining of elastomers, the adiabatic shear formation has the potential to be even more evident, leading to rapid material degradation and poor surface finish characterisitics. In this paper, cyrogenic manufacturing is reviewed, ethylene vinyl acetate (EVA) and Neoprene materials are machined illustrating and the resulting adiabatic shear band formations are ilustrated.
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The Formation of Adiabatic Shear Bands as a result of Cryogenic CNC Machining of Elastomers
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10.1007/978-1-84996-432-6_54
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2010-01-01
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The redox-active tyrosine residue (Y_Z) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced Y_Z· in magnetic interaction with the CaMn_4-cluster in the particular S -state, Y_Z·S_X intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient Y_Z· and to probe the S -states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) Y_Z in the lower S -states was oxidized by P680^+ formed via charge separation, while (ii) Y_Z in the higher S -states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the Y_Z·S_X intermediates in the different S -states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S -state characteristic changes in the split signals’ formation which reflect changes in the magnetic coupling within the CaMn_4-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the Y_Z oxidation. The apparent p K _as found for decreased split signal induction were interpreted in the fate of the phenol proton.
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Metalloradical EPR Signals from the Y_Z·S-State Intermediates in Photosystem II
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10.1007/s00723-009-0045-z
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2010-01-01
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A detailed protocol for quantitative single cell mass spectrometry imaging (MSI) analysis is described in this chapter with examples of the treatment of cells with anticancer drug, cisplatin. Cisplatin, cis -diamminedichloridoplatinum ii (CDDP), is widely used for the treatment of many malignancies, including testicular, ovarian, bladder, cervical, head and neck, and small cell and non-small cell lung cancers. The possibility of renal injury by cisplatin treatment is a major dose-limiting factor in this cancer therapy. At present, the mechanisms of cisplatin-induced renal cytotoxicity are poorly understood. In this work, secondary ion mass spectrometry (SIMS) was used for investigating cisplatin-induced alterations in intracellular chemical composition in a well-established model (LLC-PK_1 cell line) for studying renal injury. The cells were cryogenically prepared by the sandwich freeze-fracture method for subcellular imaging analysis of chemical composition (total concentrations of K^+, Na^+, and Ca^2+) in individual cells. The single cell analysis of these diffusible ions necessitates the use of reliable cryogenic sample preparations for SIMS. The sandwich freeze-fracture method offers a simple approach for cryogenically preserving diffusible ions and molecules inside the cells for SIMS analysis. A CAMECA IMS-3f SIMS ion microscope instrument capable of producing chemical images of single cells with 500-nm spatial resolution was used in the study. In cisplatin-treated cells, SIMS imaging showed the presence of detectable amount of platinum at mass 195, as ^195Pt^+ secondary ions in individual cells. SIMS observations also revealed that individual cells differed in their response to cisplatin. While the chemical composition of some cells was unaffected by cisplatin, others showed a reduction in cytoplasmic calcium stores that was not associated with changes in their intracellular K or Na concentrations. Another population of cells displayed an increase in cytoplasmic calcium concentration that was associated with higher levels of intracellular Na and a reduction in K concentration of the same cells. Since the loss of intracellular K and the gain of Na and Ca are typical symptoms of cell injury, it is plausible that the initial response of the cell to cisplatin treatment is the reduction in cytoplasmic calcium pool in stores. If, somehow, the calcium stores are compromised with cisplatin, then maintenance of free Ca^2+ homeostasis would become uncontrollable in the cell. These observations open new avenues of research for understanding of the mode of action of cisplatin in cell injury. This study also demonstrates the need and vast potential of single cell imaging mass spectrometry techniques in cell biology and medicine.
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Quantitative Imaging of Chemical Composition in Single Cells by Secondary Ion Mass Spectrometry: Cisplatin Affects Calcium Stores in Renal Epithelial Cells
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10.1007/978-1-60761-746-4_6
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2009-12-01
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Effects of various heat treatment processes, including Q/L-T, Q/H-T, Q/L-T + Ti-nitriding, Q/H-T + Ti-nitriding, and Q/CT/H-T on the S-N fatigue behavior of SKD11 steel were investigated. Ti-nitriding is a modified nitriding process that entails a small addition of approximately 2 g to 20 g of electrolyzed fine, metallic titanium in a salt bath. In the present work, depending on the applied stress and surface conditions, different crack initiators were operative, resulting in three types of crack initiation. Multi-site crack initiation around the specimen surface, observed only for the Ti-nitrided specimens at a high stress range, decreased the resistance to S-N fatigue by reducing the crack initiation cycles, Ni. At low and intermediate stress ranges, the cracked carbide particles located near the surface or internally served as crack initiators for all the specimens, regardless of whether Ti-nitriding was applied, resulting in similar resistances to S-N fatigue. Different heat treatment parameters, such as tempering temperature and cryogenic treatment, did not affect the fatigue behavior of SKD11 steel to any considerable degree. The fatigue behavior of SKD11 specimens with different heat and surface treatment conditions is discussed based on micrographic and fractographic observations.
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Effect of various heat and surface treatment conditions on the fatigue behavior of SKD11 steel
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10.1007/s12540-009-0917-7
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2009-07-01
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We describe the design and development of a cryogenic tilt table that will be used to test the flight hardware for NASA’s Satellite Test of the Equivalence Principle (STEP). Our table can tilt the hardware around two axes and is part of a test bed that has 6-degree-of-freedom controllability. The goal was to build a tilt table with a resolution better than ∼5 μrad (1 arcsec). Our table consists of three aluminum plates. The outermost plate is attached to the cryogenic probe and is fixed. The middle and inner plates rest on the outer and middle plates, respectively, using knife edges and knife edge holders made of silicon nitride that are glued to the aluminum plates. A cryogenic tilt sensor was also developed and integrated with the table. The sensor consists of an electrically grounded copper cube hanging from a support, and is placed between two pairs of capacitive electrodes. Any motion of the cube caused by tilting is measured differentially using a Wheatstone bridge circuit. The table is connected to the bottom of a cryogenic probe. A voice coil actuator, located on top of the probe at room temperature, is used to create the necessary tilt. A thin fiber is used to connect the actuator and the table. The system is controlled using a dSPACE control card. A test of the table at cryogenic temperatures (4.5 K) and low pressure (1 μTorr) showed a noise level of ∼0.7 μrad (150 marcsec), which is nearly an order of magnitude better than the required resolution.
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Cryogenic tilt table
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10.1007/s12541-009-0045-9
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2009-06-01
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The effects of the prior austenite grain size in deep cryogenic treatment on the hardness, the structural change and the wear resistance of D6 tool steel were investigated. The wear resistance of the cryogenically treated samples was determined using the pin-on-disk wear machine. The microstructural characteristics and phases present in heat treated samples were determined using SEM and XRD techniques. The results showed that the retained austenite is completely transformed to martensite during the cryogenic treatment. Besides, there is an optimum grain size of which the maximum wear resistance and hardness are obtained.
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Effects of austenizing time on wear behavior of D6 tool steel after deep cryogenic treatment
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10.1016/S1006-706X(10)60023-4
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2009-06-01
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This review covers various aspects of the single-electron tunneling pumps based on Al junctions studied at NIST over the past 15 years. The operation of a pump is described, and some important error mechanisms are summarized, which allows for a sketch of the basic pump parameters required for metrological accuracy. Fabrication of pumps, filtering of leads in the cryostat, and the electronics used to drive the pump are described next. The shuttle error technique that allows measurement of very rare errors is then described, and some outstanding questions about limitations of pumps based on Al junctions are mentioned. A detailed algorithm for cancelling the cross capacitance in a pump is described in an appendix.
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Practical aspects of counting electrons with a single-electron tunneling pump
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10.1140/epjst/e2009-01055-1
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2009-06-01
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An austenite-martensite class of stainless steel having 6Ni-16Cr (wt%) has been developed with a view to have fully austenite structure at the austenitizing temperature and a transformation structure containing austenite and martensite upon quenching. The steel has been processed through two different melting routes, vacuum melting route and air melting route. Results of both the routes were found to be similar. Nearly 50% metastable austenite is retained after quenching, which transforms further during cold deformation and sub-zero treatment. Tensile strength of 1370 MPa with 18% elongation and 1015 MPa with 11% elongation were achieved at room temperature and at 773 K respectively. Excellent tensile strength of the order of 1800 MPa and 21% elongation at 77K have been attributed to transformation induced plasticity (TRIP) occurring during processing and testing.
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Processing and characterization of a high strength austenite-martensite stainless steel
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10.1007/s12666-009-0029-6
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2009-05-01
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Numerical simulation of cavitation in cryogenic fluids is important in improving the stable operation of the propulsion system in liquid-fuel rocket. It also represents a broader class of problems where the fluid is operating close to its critical point and the thermal effects of cavitation are pronounced. The present article focuses on simulating cryogenic cavitation by implementing the “full cavitation model”, coupled with energy equation, in conjunction with iterative update of the real fluid properties at local temperatures. Steady state computations are then conducted on hydrofoil and ogive in liquid nitrogen and hydrogen respectively, based on which we explore the mechanism of cavitation with thermal effects. Comprehensive comparisons between the simulation results and experimental data as well as previous computations by other researchers validate the full cavitation model in cryogenic fluids. The sensitivity of cavity length to cavitation number is also examined.
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Validation of full cavitation model in cryogenic fluids
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10.1007/s11434-009-0253-9
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2009-05-01
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Cryogenic treatment has been acknowledged in several researches as a means of extending the tool life of many cutting tools. Studies on cryogenically treated (CT) cutting tools show microstructural changes in the material that can influence the life of the tools significantly. Tungsten carbide cutting tools are now commonly used in the industry. So far, only a few detailed studies were carried out pertaining to the cryogenic treatment of carbides. This paper primarily reports and analyses the various performances of CT coated carbide inserts and untreated (UT) coated carbide inserts in turning of nodular cast iron. From the results, it can be seen that CT coated carbide inserts exhibit better performance based on the surface roughness of the work specimen, power consumption, and flank wear than the UT ones. The scanning electron microscope analysis is carried out for the worn out CT and UT coated carbide inserts to predict the wear resistance.
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Performance analysis of cryogenically treated coated carbide inserts
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10.1007/s00170-008-1597-z
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2009-04-23
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In this study, cooling effect of copper electrode on the die-sinking of electrical discharge machining of titanium alloy (Ti-6Al-4V) has been carried out. Investigation on the effect of cooling on electrode wear and surface roughness of the workpiece has been carried out. Design of experiment plan for rotatable central composite design of second order with four variables at five levels each has been employed to carry out the investigation. Current intensity ( I ), pulse on-time ( t _on), pulse off-time ( t _off), and gap voltage ( v ) were considered as the machining parameters, while electrode wear and surface roughness are the responses. Analysis of the influence of cooling on the responses has been carried out and presented in this study. It was possible to reduce electrode wear ratio up to 27% by electrode cooling. Surface roughness was also reduced while machining with electrode cooling.
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Reducing electrode wear ratio using cryogenic cooling during electrical discharge machining
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10.1007/s00170-009-2060-5
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2009-03-01
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(Trappist-type) 3 20 °C 4.8%, 3.8%) L’influence d’un refroidissement cryogénique du caillé sur la qualité et les rendements de fromages à pâte pressée non cuite a été étudiée. Au cours de trois fabrications successives, le caillé au moulage était réparti en deux lots homogènes, l’un directement pressé, l’autre préalablement refroidi rapidement à 20 °C en cellule cryogénique. Le refroidissement anticipé du caillé a conduit à un léger retard d’acidification et à une réduction significative de l’égouttage. L’augmentation des rendements fromagers (+4.8 % au saumurage, +3.8 % fin affinage) était uniquement liée à une rétention accrue d’humidité. Les caractéristiques sensorielles des fromages affinés étaient peu différentes de celles des fromages témoins. Les légères dérives de saveur acide et de texture fondante semblent directement liées à un phénomène de post acidification, facilement corrigeable par ailleurs. À l’exception d’une légère augmentation des propriétés filantes, les fonctionnalités à chaud des fromages affinés étaient similaires à celles des fromages témoins. La comparaison de deux essais se distinguant par leurs cinétiques de refroidissement laisse, par ailleurs, supposer que l’optimisation des paramètres cryogéniques pourrait conduire à des gains de rendement plus conséquents, liés à la fois à une humidité accrue et à une meilleure récupération des constituants du lait. The influence of cryogenic cooling of cheese curd on the yield and the quality of semi-hard cheese (Trappist type) was studied. During three successive cheese manufacturing processes, the curd at moulding was separated into two aliquots: the first being directly pressed (control cheese) and the second being quickly cooled previously at 20 °C in a cryogenic cabinet (trial cheese). The cryogenic cooling of the curd slightly delayed the acidification and significantly reduced the syneresis. The increase in the cheese yield (+4.8% at brining and +3.8% at the end of ripening) was only due to the increase in the moisture retention. The sensory characteristics of the ripened cheeses were similar for both control and trial cheeses. The slight modifications in the melting texture and the acid taste were due to a post-acidification phenomenon that could be easily corrected by the classical operating parameters. Although stretchability was slightly increased in trial cheeses, the other functionalities were similar to those of control cheeses. Moreover, the comparison of the two experiments that were conducted with different kinetics of cooling suggests that optimisation of the cryogenic parameters could lead to a more marked increase in the cheese yield, due to higher moisture retention, and also lead to a better recovery of milk components.
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Influence of cryogenic cooling of cheese curd on yield and quality of semi-hard cheeses
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10.1051/dst/2008038
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2009-03-01
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Flow instability in LRE (liquid rocket engine) occurs due to various reasons such as flow interactions with valve, orifice and venturi, etc. The inception of cavitation, especially in the propellant feeding system, is the primary cause of mass and pressure oscillations because of the cyclic formation and depletion of cavitation. Meanwhile, the main propellant in a liquid rocket engine is the cryogenic fluid, which properties are very sensitive to temperature variation. And the change of propellant properties to temperature variation by thermodynamic effect needs to be properly taken into account in the flow analysis in order to understand basic mechanisms for cryogenic cavitation. The present study focuses on the formation of cryogenic cavitation by using the IDM model suggested by Shyy and coworkers. The flow instability was also numerically investigated in the downstream of orifice with a developed numerical code. Calculation results show that cryogenic cavitation can be a primary source of flow instability, leading to mass fluctuations accompanied by pressure oscillations. The prediction of cavitation in cryogenic fluid is of vital importance in designing a feeding system of an LRE.
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Flow instability due to cryogenic cavitation in the downstream of orifice
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10.1007/s12206-008-1221-z
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2009-03-01
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The possibility of improving the efficiency of cryogenic forcing on the parameters of the hanging shock determining the length of the region of minimization of the sonic boom (middle zone) generated by a modified power-law body is studied. The effect of distributed injection of the coolant from the body surface on the formation of a perturbed flow near the body and at large distances from the body is considered. The scheme of distributed injection and the regime of coolant exhaustion are demonstrated to exert a significant effect on the length of the middle zone of the sonic boom. A scheme of cryogenic forcing is determined, which ensures reduction of bow shock wave intensity by more than 40% at distances corresponding to 7000 body diameters. The mechanism of cryogenic forcing on the flow structure near the body is discussed.
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Controlling the level of the sonic boom generated by a flying vehicle by means of cryogenic forcing. 2. Distributed injection of a supercooled gas from the vehicle surface
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10.1007/s10808-009-0038-6
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2009-02-01
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Modified Angstrom method is applied to study the variation of thermal diffusivity of plain woven fabric composite in closed cycle cryo-refrigerator (CCR) based set up in the temperature range 5–300 K. The set up used is plug in type and its small size offers portability. The set up works without use of any liquid cryogen. The temperature versus thermal diffusivity curve shows three distinct regions viz. 5–30 K, 30–120 K and 120–300 K. In the first region thermal diffusivity varies exponentially and rapidly. In the second region thermal diffusivity changes exponentially but relatively slowly than that in the first region. In the last region the change in thermal diffusivity with temperature is exponential in nature but very slow.
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Study of variation of thermal diffusivity of advanced composite materials of E-glass fibre reinforced plastic (GFRP) in temperature range 5–300 K
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10.1007/s12034-009-0013-0
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2009-02-01
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Behavior of the hydrogen isotope in recombination reactions, H+H→H_2 H+T→HT and T+T→T_2 under pressurized conditions at 1.6 K were investigated using liquid helium as cryogenic reaction media by radiochemical methods. Pressure effects were observed in changes of isotope ratio HT/T_2. It became clearer that the balance of changes in bubble energy effective mass associated with energy and chemical potential contributed to the recombination reactions through bubble states. It was suggested that bubble radius was decreased significantly at higher pressure.
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Pressure effect to chemical reaction, hydrogen isotope recombination reactions in liquid helium at cryogenic temperature — Part II
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10.1007/s10967-007-7280-x
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2009-02-01
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Purpose To study the ultrastructure of biorelevant media and digestion products of self-nanoemulsifying drug delivery system (SNEDDS) at high level BS/PL conditions. Methods Cryogenic transmission electron microscopy (Cryo-TEM) was employed to visualize the colloid structures in the biorelevant media and lipolytic products generated during hydrolysis of a SNEDDS formulation. Their electrical properties were investigated by measuring their ζ -potential values. Results In the biorelevant media, vesicles (either unilamellar or multilamellar) and bilayer fragments are visualized. Occasionally, vesicles with an internal deformed structure are recognized, suggesting surface tension or uneven lateral stress. Visualization studies of the intermediate colloidal phases produced during digestion of a SNEDDS using the in vitro lipolysis model revealed the formation of similar structures as previously reported. The ζ -potential of the media was negatively charged and decreased from −23 to −35 mV with increasing surfactant/lipid load. Lower ζ -potential values (−16 mV) obtained for the structures formed during the lipid hydrolysis of the SNEDDS were probably due to the presence of calcium, which shields the surface, thereby reducing the charge. Conclusions The diversity of these vesicles in terms of size, lamellarity, and internal organization advocate their important role during lipid digestion in the gastrointestinal milieu.
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Colloidal Structures in Media Simulating Intestinal Fed State Conditions with and Without Lipolysis Products
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10.1007/s11095-008-9750-9
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2009-02-01
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This paper presents an investigation of a new method of purifying cryogenic liquid using sintered metallic wire-mesh filter, which has the advantages of high purifying efficiency and preferred strength at absolutely low temperature. Experiments are conducted to purify solid CO_2 particles from liquid nitrogen. Temperature and pressure in the upstream and downstream of the filter, and the flow rate of carbon dioxide (CO_2) gas and liquid nitrogen are measured, with the gas content of filtrate analyzed using a CO_2 concentration detector. It is illustrated that after filtration, the purity of liquid nitrogen (volume fraction) is higher than 99.99%, which means that the volume fraction of CO_2 is less than 0.01%. Effects of operation parameters on the performance of the filter, such as pressure drop Δ p and filtration efficiency E are analyzed quantitatively. The present conclusions will provide a guideline to the optimumal design and operation of sintered metallic wire-mesh filter in cryogenic application.
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Experimental investigation of a cryogenic filter for separating solid carbon dioxide particles from liquid nitrogen
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10.1007/s12204-009-0025-3
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2009-01-01
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The results of updating series-made model of two-stage Gifford−MacMahon microcryogenic system for lowering the temperature level and raising the refrigeration output are reported. Design solutions have been obtained that helped substantially improve, with minimal modification of the series-made two-stage Gifford–MacMahon microcryogenic system, the characteristics of the system: the refrigeration output at the helium temperature level exceeded 0.7 W and the minimum temperature was 1.66 K, which is a unique outcome for microcryogenic systems.
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Two-stage Gifford–Macmahon microcryogenic system for operation at subhelium temperature
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10.1007/s10556-009-9147-6
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2009-01-01
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A computational code for simulating flows of an arbitrary substance at an arbitrary condition is being developed by our research group. In this code, the preconditioned flux-vector splitting(PFVS) scheme fully coupled with the database of thermal properties, PROPATH [1], is implemented. The PFVS scheme was presented in the 2nd ICCFD conference at Sydney [2] for simulating condensate flows. This method is based on the preconditioning method developed by Weiss and Smith [3].Also in the last ICCFD at Toronto [4] , we applied our method to near-critical fluids introducing the Peng-Robinson(P-R) equation of state(EOS) [5]. Then, near-critical carbon-dioxide(CO2) flows in a micro-channel were calculated and some anomalous properties never found in fluids at atmospheric temperature and pressure could be captured.
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Numerical Method for Near-critical Fluids of Arbitrary Material
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10.1007/978-3-540-92779-2_125
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2009-01-01
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As we move towards the era of ELTs, it is timely to think about the future role of the 8-m class telescopes. Under the OPTICON program novel technologies have been developed that are intended for use in multi-object and integral-field spectrographs. To date, these have been targeted at instrument concepts for the European ELT, but there are also significant possibilities for their inclusion in new VLT instruments, ensuring the continued success and productivity of these unique telescopes.
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Smart Focal Plane Technologies for VLT Instruments
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10.1007/978-1-4020-9190-2_62
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2009-01-01
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A scheme is proposed for preparing powder materials with introduction into their composition of viscoelastic components by embrittlement with subsequent cryogenic reduction. Analysis results are provided for the mechanism of structure formation of powder mixtures based on polymers by cryogenic methods. A calculation model is developed for determining the required energy consumption for polymer reduction at low temperature. Future areas are determined for improving preparation of mixtures containing polymer binders.
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Cryogenic processing of polymer binders in the production of mixed powder products
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10.1007/s10556-009-9136-9
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2009-01-01
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The nucleation of the vapor phase in superheated nitrogen-helium liquid solutions was studied by lifetime measurements. The temperature dependences of the mean lifetime of metastable solutions were obtained at p = 0.5 and 1.0 MPa and several concentrations. The nucleation rate J was found to vary from 10^4 to 10^8 s^−1 m^−3. The adsorption of the high-volatility component on the metastable liquid-critical bubble boundary was shown to play a determining role in decreasing the temperature of the attainable solution super-heating as the solution concentration increased. The experimental data were compared with homogeneous nucleation theory. Systematic discrepancies were obtained; these discrepancies were related to the influence of the size effect on the surface tension of a nucleus and the work of its formation
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The attainable superheating of nitrogen-helium solutions
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10.1134/S0036024409100227
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2009-01-01
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High-resolution fluorescence spectroscopies are useful for studying excited-state intramolecular proton transfer (ESIPT) processes, as well as excited-state double proton transfer (ESDPT) in the case of dimeric species. Recent results are shown for four classes of compounds, i.e., hydroxychromones, aza-indoles, pyrazoloquinolines, and amino-substituted pyridine- N -oxides in liquid solutions, polycrystalline matrices, and/or a supersonic jet. These species can exist as monomers, dimers, complexes with polar solvent molecules, or mixtures of these. Proton/deuteron exchange, which strongly slows down those transfer reactions that take place through tunneling, is an important tool for elucidating the reaction mechanisms. In this chapter, emphasis is on spectral information in the wavelength domain, but time-resolved femtosecond studies (for example, on the ESDPT in dimers of 7-azaindole) are also included. Cryogenic high-resolution (Shpol’skii) spectroscopy – not only in the fluorescence but also in the absorbance mode – receives special attention. It can be used to characterize the various chemical species involved in the photochemistry/physics of the above compounds, but in favorable cases (as demonstrated for hydroxychromones) it can also detailed kinetic information on excited-state proton transfer processes that can be extracted from the homogeneous spectral linewidths.
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High-Resolution Fluorescence Studies on Excited-State Intra- and Intermolecular Proton Transfer
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10.1007/978-0-387-88722-7_12
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2009-01-01
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Superconducting magnet technology deals with the design, manufacture, and operation of superconducting magnets. A superconducting magnet is a highly stressed device: it requires the best that engineering has to offer to ensure that it operates successfully, is reliable, and at the same time is economically viable. A typical 10-tesla magnet is subjected to an equivalent magnetic pressure of 40MPa (nearly 400 atm), whether it operates superconductively at 4.2K (liquid helium) or 77K (liquid nitrogen), or resistively at room temperature. Superconducting magnet technology is interdisciplinary in that it requires knowledge and training in many fields of engineering mechanical, electrical, cryogenic, and materials Table 1.1 lists “first” events relevant to superconducting magnet technology. Particularly noteworthy events since the discovery of superconductivity in 1911 by Kamerlingh Onnes, who was also first to liquefy helium in 1908, are as follows: 1. Water-cooled 10-T electromagnets: Francis Bitter, the 1930s; 2. Large-scale helium liquefiers: Collins, the late 1940s; 3. Magnet-grade superconductors: Kunzler, et al., the early 1960s; 4. Cryostability of magnets: Stekly, the mid 1960s; 5. High-temperature superconductivity (HTS): Müller and Bednorz, 1986. Although “Bitter” electromagnets, resistive and water-cooled, operate at room temperature, we may safely state that Bitter initiated modern magnet technology. Soon after the availability of Collins liquefiers, liquid helium-until then a highly prized research commodity available only in a few research centers-became widely available and helped to propel the rapidly growing field of low temperature physics. Many important superconductors were discovered in the 1950s, leading to the development in the 1960s of magnet-grade superconductors that continues today. The formulation of design principles for cryostable magnets by Stekly and others by the mid 1960s was perhaps the single most important step in the early stage of superconducting magnet technology. It definitely helped transform superconductivity from a scientific curiosity to a realistic engineering option. Advances in superconducting magnet technology since then have succeeded in developing “highperformance” (“adiabatic,” i.e., non-cryostable) magnets that now dominate most “marketplace” superconducting magnets.
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SUPERCONDUCTING MAGNET TECHNOLOGY
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10.1007/b112047_1
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2009-01-01
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The main area of interest of our project is to provide solution which can be used in different areas of health care and which will be available through PDAs (Personal Digital Assistants), web browsers or desktop clients. The realized system deals with an ECG sensor connected to mobile equipment, such as PDA/Embedded, based on Microsoft Windows Mobile operating system. The whole system is based on the architecture of .NET Compact Framework, and Microsoft SQL Server. Visualization possibilities of web interface and ECG data are also discussed and final suggestion is made to Microsoft Silverlight solution along with current screenshot representation of implemented solution. The project was successfully tested in real environment in cryogenic room (-136^OC).
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Mobile Monitoring Stations and Web Visualization of Biotelemetric System - Guardian II
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10.1007/978-3-642-11284-3_29
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2008-12-01
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The temperature dependence of dielectric constant and loss were investigated for poled and unpoled [001]-oriented 0.68PMN–0.32PT single crystal and ceramics at cryogenic temperature. Two abnormal loss peaks, which are frequency dependent, are presented for all the samples. One of abnormal loss peaks locates in the range from 50 to 80 K and the other was observed in the range from 200 to 300 K. The difference of the abnormal loss between the single crystal and ceramics were compared. It is assumed that the dielectric loss anomalies at cryogenic temperature are related to the change of domain structure and phase structure parameter induced by temperature.
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Dielectric loss anomalies of 0.68PMN–0.32PT single crystal and ceramics at cryogenic temperature
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10.1007/s10832-007-9150-2
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2008-12-01
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Ten billion cubic meters of hydrogen are dissipated to the environment along with the emission of coke-oven gas every year in China. A novel cryogenic separation of hydrogen from coke oven gas is proposed to separate the hydrogen and liquefy it simultaneously, and the cooling capacity is supplied by two refrigeration cycles. The performance of the ideal vapor refrigeration cycle is analyzed with methane and nitrogen as refrigerant respectively. The results show that the coefficient of performance (COP) of methane refrigeration cycle is 2.7 times that of nitrogen refrigeration cycle, and the figure of merit (FOM) of methane refrigeration cycle is 1.6 times that of nitrogen refrigeration cycle. The performance of ideal gas refrigeration cycle is also analyzed with neon, hydrogen and helium as refrigerant respectively. The results show that both the coefficient of performance and figure of merit of neon refrigeration cycle is the highest. It is thermodynamically possible to arrange the refrigeration cycle with methane and neon as refrigerant, respectively.
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Refrigeration cycle for cryogenic separation of hydrogen from coke oven gas
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10.1007/s11708-008-0096-0
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2008-11-01
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We analyze changes in the structural characteristics and mechanical properties of composite materials with a polyamide matrix depending on the type of heat treatment. It is shown that thermocyclic treatment with a decrease of temperature to cryogenic temperatures leads to partial cold recrystallization in nanofilled materials and to an increase in the adhesive strength of glass-filled specimens.
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Influence of heat treatment regimes on the structure and mechanical properties of polyamide composites
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10.1007/s11003-009-9142-2
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2008-11-01
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The possibility of controlling the sonic boom level by means of cooling the surface of a flying vehicle is discussed. The effect of surface cooling on the formation of the perturbed flow structure at large distances from the vehicle is demonstrated by an example of a modified power-law body of revolution. The intensity of the intermediate shock wave and the perturbed pressure pulse near the body are seen to decrease, which expands the altitude range of the region where the sonic boom is reduced (down to 50%). At larger distances from the body, cryogenic forcing ensures a 12% decrease in the bow shock wave intensity. The possibility of controlling the process of formation of wave structures near the surface, such as barrel shock waves, is demonstrated. An explanation of the cryogenic forcing mechanism is offered.
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Controlling the level of the sonic boom generated by a flying vehicle by means of cryogenic forcing. 1. Cooling of the vehicle surface
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10.1007/s10808-008-0119-y
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2008-11-01
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A strong lightweight material (X-VOx) was formulated by nanocasting a conformal 4 nm thin layer of an isocyanate-derived polymer on the entangled worm-like skeletal framework of typical vanadia aerogels. The mechanical properties were characterized under both quasi-static loading conditions (dynamic mechanical analysis, compression and flexural bending testing) as well as high strain rate loading conditions using a split Hopkinson pressure bar (SHPB). The effects of mass density, moisture concentration and low temperature on the mechanical properties were determined and evaluated. Digital image correlation was used to measure the surface strains through analysis of images acquired by ultra-high speed photography, indicating nearly uniform compression at all stages of deformation during compression. The energy absorption of X-VOx was plotted as a function of the density, strain rate and temperature, and compared with that of plastic foams. X-VOx remains ductile even at −180 °C, a characteristic not found in most materials. This unusual ductility is derived from interlocking and sintering-like fusion of nanoworms during compression. X-VOx emerges as an ideal material for force protection under impact.
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Synthesis and characterization of the physical, chemical and mechanical properties of isocyanate-crosslinked vanadia aerogels
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10.1007/s10971-008-1788-y
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2008-10-01
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Measurements of microwave attenuation at room temperature and 4.2 K have been performed on some conductors commonly used in receiver input circuits. The reduction in loss on cooling is substantial, particularly for copper and plated gold, both of which showed a factor of 3 loss reduction. Copper passivated with benzotriazole shows the same loss as without passivation. The residual resistivity ratio between room temperature and 4.2 K, deduced from the measurements using the classical skin effect formula, was smaller than the measured DC value to a degree consistent with conduction in the extreme anomalous skin effect regime at cryogenic temperatures. The measurements were made in the 5–10 GHz range. The materials tested were: aluminum alloys 1100-T6 and 6061-O, C101 copper, benzotriazole treated C101 copper, and brass plated with electroformed copper, Pur-A-Gold 125-Au soft gold, and BDT200 bright gold.
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Microwave Loss Reduction in Cryogenically Cooled Conductors
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10.1007/s10762-008-9394-1
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2008-09-01
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The reliability of buildings and structures erected in the cryolithozone has been exacerbated in the past decade. Basic principles of the development of deformations associated with both a change in properties of the frost, and also with the operating mode of the entities are analyzed, using the Noril'sk industrial region as an example.
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Decreasing geotechnical reliability with worsening frozen-bed conditions
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10.1007/s11204-008-9023-y
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2008-09-01
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Capillary pressure force and direct surface tension force are known to be sufficient though probably not necessary to drive the compaction stage of latex film formation. There is abundant evidence that van der Waals force can draw particles together progressively more around the perimeters of interparticle contacts, but their role in compaction remains unanswered. With the powerful technique of high-resolution cryogenic scanning electron microscopy (cryo-SEM), together with fast-freezing and freeze-drying followed by controlled annealing at temperatures below and around the nominal glass transition temperature, we have documented the role of van der Waals force in film formation in the water-free condition, i.e., with capillary pressure and surface tension forces absent. Results of imaging the freeze-dried and annealed coatings are fully consistent with the hypothesis that van der Waals force alone can compact a latex coating. The rate at which particles flatten and thus the coating compacts by annealing increases, as expected, with temperature and time. The results of rewetting tests of coatings annealed at various temperatures demonstrate that compacted coating is not necessarily coalesced, and that even full compaction of solid particles can be elastic, hence reversible, rather than viscoelastic or viscoplastic. Some of the results suggest that soluble ionic surfactant and oligomeric and grafted polymeric stabilizers at particle surfaces, collapse to undetectable dimensions during freeze-drying, yet reswell to detectable size during rewetting, if they have not dissolved into polymer particles during annealing.
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Role of van der Waals force in latex film formation
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10.1007/s11998-008-9095-7
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2008-09-01
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The results of mathematical modeling of thermal and mechanical responses of fuel materials in the process of direct drive target delivery into the reaction chamber are presented. Special attention is paid to the influence of fuel-layer anisotropy on the layer degradation that is of critical importance for the optimization of the delivery process.
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Thermal and mechanical responses of cryogenic targets with different fuel-layer anisotropy during the delivery process
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10.1007/s10946-008-9037-y
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2008-08-01
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Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h. Hardness tester, OM, XRD, SEM were used to investigate the mechanical properties and microstructures of the alloy. The results show that the hardness increases by 1–2 (HRC) and the compressive strength decreases slightly after cryogenic treatment. The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbide η-Fe_2C. The decrease in compressive strength is caused by residual stress. The great amount of carbides, such as Cr_7C_3 and Fe_2MoC, in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress. The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite. The cryogenic martensite is long and fine; while the non-cryogenic martensite is short and coarse. There is obvious surface relief of the cryogenic martensite transformation. It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly. The surface relief in the non-cryogenic martensite is wide and arranged in parallel, and the boundary of surface relief is not smooth. These characteristics may imply different growth ways of the two kinds of martensite.
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Effects of cryogenic treatment on mechanical properties and microstructure of Fe-Cr-Mo-Ni-C-Co alloy
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10.1007/s11771-008-0085-9
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2008-08-01
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Recent measurements have shown a record-breaking low thermal conductivity λ_total of less than 0.25 × 10^−3 W·m^−1·K^−1 at temperatures of 120 K for an evacuated sample consisting of polyimide fibers with a trilobal fiber cross section. Existing models for the heat transport in fiber insulations cannot sufficiently describe fiber insulations consisting of fibers with non-cylindrical cross sections. In this article, a modification for the model for cylindrical fibers will be presented. The modifications for the trilobal cross section of the fiber will be explained and compared to the original cylindrical model. The results of the theoretical calculations will be discussed in comparison to experimental results of measurements performed with a guarded hot-plate apparatus at temperatures in the range from 120 K to 420 K.
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Trilobal Polyimide Fiber Insulation for Cryogenic Applications
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10.1007/s10765-008-0471-4
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2008-07-01
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Characterization is a first step to site cleanup or decommissioning of a disused nuclear facility. Good knowledge of the inventory of nuclides present, both type and location, is important in the design of an effective plan of remediation. Several systems based on HPGe detectors have been developed, both commercially and at laboratories, and are already in use for this purpose. Their use is somewhat complicated by the need for cryogenic cooling of the HPGe detector. Handling of liquid nitrogen in field situations is always difficult. Recent developments in low-power electromechanical cooling for HPGe detectors have made possible the construction of low weight, portable HPGe spectrometers with sufficient efficiency to perform the needed measurements in reasonable count times, without the need for liquid nitrogen. A mobile system was modified to use a battery-powered, Sterling-engine cooler on a nominal 40% relative efficiency detector. This system was characterized for efficiency and uniformity of response. The baseline spectra were analyzed using the DOE EML 1-meter methods to obtain representative MDA values for several nuclides of interest and typical counting times.
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Performance of a portable, electromechanically-cooled HPGe detector for site characterization
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10.1007/s10967-008-0723-6
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2008-07-01
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A previously constructed semi-rotating cryogenic modulator was modified for comprehensive two-dimensional gas chromatography (GC×GC). The retention time repeatability was improved by replacing the modulator control program unit with a new system. Peak widths obtained with the modified modulator were comparable with those obtained with the previous modulator and other modulator types. The modulator was easy to construct and it can be installed in any commercial GC system. The constructed GC×GC–FID system and data obtained by gas chromatography–mass spectrometry (GC–MS) were used for identification of unknowns in forest aerosol samples. Figure A semi-rotating cryogenic modulator in which modulation is based on two-step cryogenic trapping with continuously flowing carbon dioxide has been developed for comprehensive two-dimensional gas chromatography
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Modified semi-rotating cryogenic modulator for comprehensive two-dimensional gas chromatography
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10.1007/s00216-008-2122-9
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2008-06-01
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We present a comprehensive investigation of the volume transition in thermosensitive core-shell particles. The particles consist of a solid core of poly (styrene) (radius: 52 nm) onto which a network of crosslinked poly( N -isopropylacrylamide) (PNIPAM) is affixed. The degree of crosslinking of the PNIPAM shell effected by the crosslinker N , N ^′-methylenebisacrylamide was varied between 1.25 and 5 mol%. Immersed in water, the shell of these particles is swollen at low temperatures. Raising the temperature above 32°C leads to a volume transition within the shell. Cryogenic transmission electron microscopy (Cryo-TEM) and dynamic light scattering (DLS) have been used to investigate the structure and swelling of the particles. The Cryo-TEM micrographs directly show inhomogeneities of the network. Moreover, a buckling of the shell from the core particle is evident. This buckling increases with decreasing degree of crosslinking. A comparison of the overall size of the particles determined by DLS and Cryo-TEM demonstrates that the hydrodynamic radius provides a valid measure for the size of the particles. The phase transition within the network measured by DLS can be described by the Flory–Rehner theory. It is shown that this model captures the main features of the volume transition within the core-shell particles including the dependence of the phase transition on the degree of crosslinking. All dispersions crystallize at volume fractions above 0.5. The resulting phase diagram is identical to the phase behavior of hard spheres within the limits of error. This demonstrates that the core-shell microgels can be treated as hard spheres up to volume fractions of at least 0.55.
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Direct imaging of temperature-sensitive core-shell latexes by cryogenic transmission electron microscopy
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10.1007/s00396-008-1873-3
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2008-06-01
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Polycrystalline diamond is widely used as a economic cutting material for machining non-ferrous materials such as aluminum. It is perceived that diamond cannot be used for cutting ferrous materials due to the high affinity of carbon to iron. Nevertheless, under certain conditions it is possible to use diamond materials for cutting ferrous metals. In order to avoid graphitization of the diamond matrix, it is necessary to keep the cutting temperature below the critical level of diamond graphitization. This paper presents the influence of a cryogenic CO_2 coolant strategy on the cutting process using PCD tools for cutting high strength compacted graphite iron (CGI). Investigations show, that tool wear behavior strongly correlates with the cutting speed, the cutting forces, cutting temperatures, and surface roughness of the workpiece. The test results show, that the tool life of PCD for cutting cast iron is dependent on the diamond grain size, the binder material, and the cutting parameters.
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Using PCD for machining CGI with a CO_2 coolant system
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10.1007/s11740-008-0104-6
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2008-06-01
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The assembled form of thick-wall glass fiber reinforced plastics (GFRP) tube and 0Cr18Ni9 austenitic stainless steel pipes was designed as the radius thermal-insulating and load-supporting structure in cryogenic vessels. In order to study the thermal leakage and gap changes on the support structure, as well as radius temperature and stress distribution on GFRP tube, an experimental investigation has been taken. The results indicate that the support structure is proved to fit well as thermal-insulating and load-supporting part in cryogenic vessels, furthermore has high security during cryogenic applications.
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Thermal structure of glass fiber reinforce plastic support structure
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10.1007/s12204-008-0370-7
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2008-05-01
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Procedures and equipment permitting realization of processes involving utilization of casinghead gas (CHG) directly in the fields are enumerated. A schematic diagram is presented for the processing of CHG using low-temperature condensation and subsequent deethanization with the acquisition of dry naphtha-free gas and a wide-cut of light hydrocarbons. An example of the selection of a gas-processing plant for a specific field is analyzed.
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Processing procedures for casinghead gas
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10.1007/s10556-008-9046-2
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2008-05-01
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In Coherent Neutrino Nucleus Scattering (CNNS) the neutrinos interact coherently with all nucleons leading to a cross section which is much larger than for all other neutrino interactions. Because of the small momentum transfer as well as the small recoil energy in CNNS, and the relatively low count rate, a low energy threshold and a large target mass (several hundred grams) are required to observe CNNS. Our aim is to build a cryodetector for that purpose. Such a cryodetector, installed in the vicinity of a nuclear power plant, could probe new physics like non-standard neutral current interactions or a neutrino magnetic moment. We describe the results of three detectors, with Ge absorbers of 0.8 and 3.2 g and with a CaWO_4 absorber of 10 g. For Ge (0.8 g) an energy threshold of 0.43 keV and an energy resolution of 0.27 keV at ∼6 keV could be reached. We demonstrate that surface roughness effects deteriorate both threshold and resolution. For the 10 g CaWO_4 absorber we obtained 0.27 keV and 0.35 keV for threshold and energy resolution at ∼6 keV respectively.
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Development of a Cryogenic Detector for Coherent Neutrino Nucleus Scattering
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10.1007/s10909-008-9720-y
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2008-05-01
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Near-surface-events are a major limitation to the performance of cryogenic massive germanium heat and ionisation detectors for dark matter search, due to their incomplete charge collection. We present here a powerful method of surface event identification based on the transient heat signal of a Ge bolometer, equipped with two NbSi high impedance thin film sensors. Calibration runs using electrons and low energy gamma particles from a ^109Cd source show highly effective surface event rejection down to the heat threshold energy. Neutron and gamma source calibrations were realised to get information on the fiducial volume of the Ge absorber. First results from low background data taking are discussed.
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Surface Event Rejection of the EDELWEISS Cryogenic Germanium Detectors Based on NbSi Thin Film Sensors
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10.1007/s10909-008-9753-2
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2008-05-01
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Astroparticle bolometric detectors often rely on the use of dilution refrigerators providing a large cooling power at millikelvin temperatures. Conventional machines, however, need a systematic supply of cryogenic fluids, complicating and making more expensive their operation, particularly in underground laboratories. We describe here novel cryogen-free dilution units, able to cool down large detectors to millikelvin temperatures, and where cooling and warming times have been optimised.
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Pulse-Tube Dilution Refrigeration below 10 mK for Astrophysics
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10.1007/s10909-008-9725-6
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2008-05-01
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Detectors fitted with interleaved collection electrodes offer a promising solution to the problem of surface event rejection in cryogenic Ge detectors for dark matter search. Detector design and modeling are discussed, based on computer simulations of the collection field and on pulse-shape analysis of the ionization signals. Test experiments with a prototype detector are presented in a companion paper by X. Defay et al. in this conference.
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Cryogenic Ge Detectors with Interleaved Electrodes: Design and Modeling
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10.1007/s10909-008-9754-1
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2008-05-01
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The CUORE detector, to be installed in 2010 at LNGS, is made of 988 TeO_2 crystals to be cooled to 10 mK. It consists of a large cryogen-free cryostat cooled by five pulse tubes and one high-power specially designed dilution refrigerator (R. Ardito et al. in http://arxiv.org/abs/hep-ex/0501010 , [ 2005 ]). The cryostat is ∼ 3 m high and has a diameter of ∼ 1.6 m. About 5 tons of lead shielding are to be cooled to below 1 K and a mass of 1.5 ton must be cooled to 10 mK. Some tie-rods sustain the different parts of the experiment. One end of each rod is at low temperature (10 mK for the detector frame, 50 mK for the coldest radiation shield, 700 mK for the shield linked to the still) with the other end usually at room temperature. A thermalization of the rods at the temperature of the first stage of the pulse tubes will be realized. Hence the value of the thermal conductivity of the material up to room temperature is important. At the lowest temperatures, the thermal conductivity has great influence in establishing the thermal load on the dilution refrigerator. The thermal conductivity of the structural material candidates for such tie-rods is usually known down to 4.2 K. Here we present data of thermal conductivity for the Ti6Al4V alloy below its superconductive transition temperature (4.38 K). A comparison over the full temperature range of operation is also done with other materials, such as 316 stainless steel and Torlon, candidates for the realization of the tie-rods.
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Low Temperature Thermal Conductivity of Ti6Al4V Alloy
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10.1007/s10909-008-9726-5
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2008-05-01
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A new design of an ionization-heat germanium detector for dark matter search is presented, based on the use of interleaved electrodes for charge collection. This device allows active rejection of surface events by performing the appropriate cuts in the charge measurement data. Test experiments were performed with a prototype device, fitted with annular collection electrodes and with a neutron transmutation-doped Ge thermometer. Calibration runs with gamma and neutron sources demonstrate the remarkable possibilities offered by this type of detector in terms of surface event discrimination.
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Cryogenic Ge Detectors for Dark Matter Search: Surface Event Rejection with Ionization Signals
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10.1007/s10909-008-9762-1
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2008-05-01
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LMSAL and NIST are developing position-sensitive X-ray strip detectors based on TES microcalorimeter arrays for solar physics. An important application of these devices will be the study of high temperature (>10 MK) X-ray lines, e.g. Fe XXV, at high spectral ( E /Δ E ≥1000) and temporal (sub-ms) resolution. Diagnostics from these lines will provide significant new insights into the physics of microflares and the early stages of flares. In this paper, we will describe the current status of our laboratory test program and applicability of our research to future space missions
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X-ray Microcalorimeter Research for Solar Physics at LMSAL and NIST: An Update
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10.1007/s10909-008-9735-4
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2008-05-01
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A 16-SQUID array has been designed and fabricated, which shows 0.12 μ Φ _0 Hz^−1/2 flux noise at 4.2 K. The readout amplifier based on a cryogenic silicon-germanium bipolar transistor employs short-delay negative flux feedback and reaches 7 MHz bandwith for a 1 Φ _0 p - p signal. The −1 dB compression is reached approximately at 4.2 Φ _0 p - p amplitude when the signal frequency is 1 MHz. In the feedback mode the flux noise is anomalously increased to 0.35 μ Φ _0 Hz^−1/2.
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High Dynamic Range SQUID Readout for Frequency-Domain Multiplexers
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10.1007/s10909-008-9765-y
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2008-05-01
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We have developed a multiplexed read-out for transition-edge sensors (TES) based on a hybrid time- and frequency-domain basis set, similar to that used in time-division multiple-access (TDMA) mobile phones. The hybrid basis set uses bandwidth more efficiently than microwave frequency-division SQUID multiplexing, making it possible to multiplex more detectors in each output line. The high open-loop bandwidth provided by our SQUID TDMA system also makes it possible to multiplex large arrays of fast, high dynamic range detectors such as fast x-ray calorimeters. In this approach, we embed the second-stage SQUID amplifier of our standard time-division multiplexer in an impedance matching circuit coupled to a broadband cryogenic high electron mobility transistor (HEMT) in a microwave reflectometer configuration. The input signals are flux coupled into the first-stage SQUID amplifiers whose signals are time-division multiplexed into the second-stage SQUID. At room temperature, the signal from the HEMT is mixed down to dc for analysis and further signal processing.
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A TDMA Hybrid SQUID Multiplexer
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10.1007/s10909-008-9769-7
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2008-05-01
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The expected final reach of the Weakly Interacting Massive Particle (WIMP) search experiment CDMS-II by the end of 2007 is a WIMP-nucleon cross-section sensitivity of 2.1×10^−44 cm^2. To proceed further in our search, we have proposed the SuperCDMS Phase A project that would deploy 42 1-inch thick Ge detectors, at a site deeper than the location of CDMS II, and reach a desired sensitivity goal of 1.3×10^−45 cm^2. These cross-sections are of interest and are complementary to Supersymmetry searches at the Large Hadron Collider (LHC) and future linear colliders.
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Present Status of the SuperCDMS program
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10.1007/s10909-008-9740-7
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2008-05-01
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It is now well established and accepted that the universe has a total density equal to the critical density (Ω=1) and that roughly 25% of that amount is accounted for by non-relativistic particles. That these particles, referred to as Dark Matter, have remained a mystery has served to motivate physicists to design more ingenious and far reaching experiments in an attempt to identify and understand them. This paper will review various ongoing and proposed Dark Matter searches which employ cryogenic techniques to both detect the rare Dark Matter interactions as well as reject the vast number of background events from cosmic ray and radioactive backgrounds. Such experiments are already sensitive to and are able to reject certain models of supersymmetry, and with the increases in sensitivity projected over the next few years may even be able to detect these elusive particles.
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Hot on the Tail of the Elusive WIMP: Cryogenic Dark Matter Searches in the 21st Century
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10.1007/s10909-008-9744-3
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2008-05-01
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Low temperature photon detectors are increasingly attractive tools for materials analysis. Their range of applications has broadened from early work on x-ray fluorescence and now spans the electromagnetic spectrum from terahertz to gamma-ray energies. In addition, low temperature detectors (LTD’s) show promise for measuring the energy of neutrons, alpha particles, simple ions, and complex biomolecules. LTD’s are emerging from low temperature laboratories and can now be found at a growing range of analytical facilities including electron microscopes, mass spectrometers, ion traps, and synchrotrons. Here, we review these uses of LTD’s. Despite the remarkable capabilities of LTD’s, they are still at the stage of demonstration measurements for some applications. We discuss obstacles to the more widespread use of LTD’s and some emerging solutions to these obstacles.
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Materials Analysis with Cryogenic Sensors
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10.1007/s10909-008-9749-y
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2008-05-01
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A microwave single-photon detector was developed with highly-excited alkaline Rydberg-atoms in a cooled resonant cavity to search for dark matter axions. This detector belongs to a microwave single-photon counter, thus being free from the standard quantum limit (SQL). High sensitivity of the present detector system was demonstrated by measuring the thermal blackbody radiations in the cavity at temperatures as low as 70 mK where the sensitivity is below the SQL. The detection sensitivity of the present system is mainly limited by stray electric fields present in the detection region. Practical design of a new experimental scheme with a guiding electric field through the atomic-beam trajectory is here presented and discussed to avoid the effect of stray electric field and thus to improve the detection sensitivity.
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Practical Design for Improving the Sensitivity to Search for Dark Matter Axions with Rydberg Atoms
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10.1007/s10909-008-9786-6
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2008-05-01
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The EBIT Calorimeter Spectrometer (ECS) is currently being completed and will be installed at the EBIT facility at the Lawrence Livermore National Laboratory in October 2007. The ECS will replace the smaller XRS/EBIT microcalorimeter spectrometer that has been in almost continuous operation since 2000. The XRS/EBIT was based on a spare laboratory cryostat and an engineering model detector system from the Suzaku/XRS observatory program. The new ECS spectrometer was built to be a low maintenance, high performance implanted silicon microcalorimeter spectrometer with 4 eV resolution at 6 keV, 32 detector channels, 10 μs event timing, and capable of uninterrupted acquisition sessions of over 60 hours at 50 mK. The XRS/EBIT program has been very successful, producing many results on topics such as laboratory astrophysics, atomic physics, nuclear physics, and calibration of the spectrometers for the National Ignition Facility. The ECS spectrometer will continue this work into the future with improved spectral resolution, integration times, and ease-of-use. We designed the ECS instrument with TES detectors in mind by using the same highly successful magnetic shielding as our laboratory TES cryostats. This design will lead to a future TES instrument at the LLNL EBIT. Here we discuss the legacy of the XRS/EBIT program, the performance of the new ECS spectrometer, and plans for a future TES instrument.
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The EBIT Calorimeter Spectrometer: A New, Permanent User Facility at the LLNL EBIT
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10.1007/s10909-008-9788-4
|
2008-05-01
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An irreversible model of an Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas is established, which is composed of two isothermal and two isobaric processes. The influence of both the quantum degeneracy and the finite-rate heat transfer between the working fluid and the heat reservoirs on the performance of the cycle is investigated, based on the theory of statistical mechanics and thermodynamic properties of an ideal Fermi gas. The inherent regeneration losses of the cycle are analyzed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Especially, the optimal performance of the cycle in the strong and weak gas degeneracy cases and the high temperature limit is discussed in detail. The analytic expressions of some optimized parameters are derived. Some optimum criteria are given. The distinctions and connections between the Ericsson refrigeration cycles working with the Fermi and classical gases are revealed.
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Parametric optimum analysis of an irreversible Ericsson cryogenic refrigeration cycle working with an ideal Fermi gas
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10.1007/s12043-008-0089-x
|
2008-04-01
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For the phonon-light technique employed in the CRESST experiment very sensitive light detectors are needed as only a small fraction of the energy of incident particles is detected as light. Following Neganov and Luke, the sensitivity can be improved by drifting the generated charge carriers in a semiconductor absorber by an applied electric field. For an efficient charge collection substrates with low trap densities are required. For this purpose and for electrical decoupling the TES is glued onto the drift device. Results from measurements with Neganov-Luke amplification using glued TES will be presented.
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Application of the Neganov-Luke Effect for Scintillation Light Detection
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10.1007/s10909-007-9672-7
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2008-04-01
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Macroporous viscoelastic poly(vinyl alcohol) (PVA) cryogels are prepared from aqueous concentrated (80–120 g/l) PVA solutions subjected to 1–5 cycles of cryogenic treatment (freezing at −20°C for 19 h and subsequent thawing at a rate of 0.3°C/min). Shear moduli and fusion temperatures of corresponding samples are determined and the structure of thin sections is studied by optical microscopy with subsequent processing and analysis of images obtained. The previously described effect of a substantial increase in the rigidity and thermal stability of PVA cryogels resulted from the repeated freezing-thawing cycles is confirmed. The largest (jumpwise) changes in the physicochemical characteristics of such gels and their macroporous morphology take place after the second cycle of cryogenic treatment. Moreover, depending on the PVA concentration in the initial solution, the mean cross section of micropores increases by a factor of 2–3 and the total porosity of cryogel rises by a factor of 1.5–2; i.e., the imperfection of material increases. Nevertheless, this negative (from view-point of the integral properties of cryogel) effect is completely overpowered by processes of additional structuring, which result in the strengthening of polymer phase proceeding during the repeated freezing-thawing cycles.
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Study of cryostructuring of polymer systems: 28. Physicochemical properties and morphology of poly(vinyl alcohol) cryogels formed by multiple freezing-thawing
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10.1134/S1061933X08020117
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2008-04-01
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For the purpose of building very sensitive light and phonon detectors, as e.g. applied in the Dark Matter (DM) experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers), transition edge sensors (TESs) in combination with a massive absorber crystal are used. To ensure high sensitivity of the detectors, low heat capacities, i.e. low working temperatures of about 10 mK are aimed at. Therefore, TESs made of tungsten thin films exhibiting the alpha-tungsten ( α -W) phase with transition temperatures of T _ c =10–15 mK are required. We have produced tungsten thin films with T _ c in the range of 25–55 mK by rf-sputtering. To decouple the thermometer production from the choice of the target material and to avoid heating cycles of the absorber crystal, a composite design for detector production is applied. The composite design includes fabrication of the TES on a separate substrate and then attaching of this separate TES to a massive absorber crystal by gluing. For this purpose small sapphire substrates are used for the deposition of the TES. Properties of tungsten thin films grown with the rf-sputtering technique as well as first results of composite detectors built with these films acting as TESs will be presented.
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Properties of Tungsten Thin Films Produced with the RF-Sputtering Technique
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10.1007/s10909-007-9642-0
|
2008-03-01
|
The procedures of bearing strength prediction for composite laminates reinforced with high-strength unidirectional fibers at room and cryogenic temperatures are discussed. The best agreement between the calculated and experimental data is observed when the temperature dependence of effective mechanical parameters of plies is allowed for within the framework of the elastic theory of laminated heterogeneous bodies.
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Bearing strength prediction for reinforced composite laminates for cryogenic and aerospace applications
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10.1007/s11223-008-9003-5
|
2008-02-01
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Given the practical impossibility of obtaining new precision Rh-0.5at%Fe resistance thermometers in recent years, the possible re-starting of the production of such thermometers in Yunnan (China) was explored by Istituto Nazionale di Ricerca Metrologica (INRIM). Ten prototypes of the new production were made available in early 2006. The paper reports the preliminary data from the testing performed to date on these prototypes at National Institute of Metrology (NIM) and Instytut Niskich Temperatur i Badan Strukturalnych (INTiBS). Although a problem with the alloy composition was detected, the reproducibility results on thermal cycling are very encouraging. Resistance-temperature ( R - T ) characteristics below 30 K, though not identical with those of similar thermometers formerly available from Tinsley and VNIIFTRI, are still suitable for accurate metrology.
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Preliminary Results on New Prototypes of Precision Rh-0.5at%Fe Resistance Thermometers of Chinese Production
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10.1007/s10765-007-0335-3
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2008-02-01
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As a basis for evaluating the results of an international star comparison of sealed fixed-point cells, dedicated investigations have been directed to the dependence of the melting temperature on different conditions concerning the preparation of the solid phase, i.e., fast and slow freezing, refreezing without supercooling, or annealing at a temperature of only a few mK below the melting temperature. Differences in the typical thermophysical behavior of the four fixed-point substances hydrogen, neon, oxygen, and argon have been found. In the case of hydrogen and oxygen, the quality of the crystal lattice has little influence on the melting temperature. This enables temperature widths of the melting curves of only a few tens of μK, if there are no additional influences. On the contrary, argon samples frozen after supercooling with different velocities of freezing typically melt within a range of 0.3 mK. The melting-curve width can be reduced only by refreezing. A broader melting range of a few tenths of mK has been typically observed for neon cells. Unlike argon, an improvement of the crystal quality by a slow refreezing does not decrease the width of the melting-curve.
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Influence of the Freezing and Annealing Conditions on the Realization of Cryogenic Triple Points
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10.1007/s10765-007-0301-0
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2008-02-01
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The behavior of recombinations of H+H→H_2, H+T→HT and T+T→T_2 in liquid helium at cryogenic temperature of 1.6 K was investigated under pressurized condition using radiochemical methods. It was found that the isotope ratios of H_2, HT and T_2 were changed with the pressure. The changes will contribute to the bubble formation, chemical potential and the effective masses of H and T. This work is a preliminary information to carry out chemical reactions in liquid helium.
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Pressure effect in hydrogen isotope recombination reactions in liquid helium at cryogenic temperature
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10.1007/s10967-007-7017-2
|
2008-02-01
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A high-sensitivity microwave-single-photon detector was developed in Kyoto, in which microwave photons in a resonant cavity cooled at very low temperatures are absorbed by highly excited Rydberg atoms and the Rydberg atoms thereby promoted to a higher excited state are then selectively field-ionized and detected. This scheme allows us to count microwave photons one by one, thus provide a single-photon counting without the limit of standard quantum limit (SQL). The apparatus “CARRACK” for the single-photon detector was constructed based on this scheme, where the cavity was cooled down to 10 mK range to reduce the background of thermal blackbody photons from the cavity wall. The apparatus has served for years to search for dark matter axions in the 10 μeV (∼2.4 GHz) mass region. Thermal blackbody photons in a microwave resonant cavity at temperatures as low as 70 mK have been measured, the sensitivity being below the SQL limit. A number of improvements in the detection efficiency and sensitivity have been planned and will be reported. Applications of the detector to fundamental physics are also discussed shortly.
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A High-Sensitivity Microwave-Single-Photon Detector with Rydberg Atoms at Low Temperature
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10.1007/s10909-007-9586-4
|
2008-01-01
|
Only microalgae (algae with cell/filament/thallus size <2 mm) are considered in this chapter. However, the methods described are applicable to a wide variety of prokaryotic cyanobacteria and eukaryotic microalgae. Most culturable cyanobacteria and soil microalgae that have been examined can be cryopreserved with relatively high viability. Furthermore, many freshwater and marine eukaryotic algae can also be cryopreserved, but usually with lower viability. Marine diatoms can be cryopreserved, and often have high viability (Day and Brand 2005), although there has been limited success preserving freshwater diatoms (McLellan 1989). It has been observed that chlorarachniophytes, eustigmatophytes, pelagophytes, phaeothamniophytes and ulvophytes often have very high success rates, comparable to the other green algae and cyanobacteria (Day and Brand 2005). However, to date, most morphologically complex taxa including members of the dinoflagellates, cryptophytes, synurophytes and raphidophytes cannot be successfully cryopreserved. It is anticipated that further research on the basic mechanisms of freezing damage and the empirical development of improved protocols will continue to expand the number and diversity of algal taxa responsive to cryopreservation techniques.
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Cryopreservation of Algae
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10.1007/978-0-387-72276-4_6
|
2008-01-01
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Elucidating the dynamics of proteins remains a central and daunting challenge of molecular biology. In our contribution we discuss the relevance of lowtemperature observations not only to structure, but also to dynamics, and thereby to the function of proteins. We first review investigations on light-harvesting complexes to illustrate how increased photostability at low temperatures and spectral selection provide a deeper insight into the excitonic interactions of the chromophores and the dynamics of the protein scaffold. Furthermore, we introduce a novel technique that achieves controlled, reproducible temperature cycles of a microscopic sample on microsecond timescales. We discuss the potential of this technique as a tool to achieve repeatable single-molecule freeze-trapping and to overcome some of the limitations of single-molecule experiments at room temperature.
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Single Biomolecules at Cryogenic Temperatures: From Structure to Dynamics
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10.1007/978-3-540-73924-1_2
|
2008-01-01
|
Associations of galaxies range from pairs and small groups, through the giant clusters containing over a thousand galaxies, to the vast structures on scales much greater than clusters such as the vast ‘walls’ seen in Figs. 2.7 and 2.8. Clustering occurs on all scales, as is demonstrated by the two-point correlation function for galaxies (Figs. 2.5 and 2.6). Few galaxies can be considered truly isolated. Rich clusters of galaxies are of particular interest because they are the largest gravitationally bound systems we know of in the Universe. They possess correspondingly deep gravitational potential wells which can be observed through the bremsstrahlung Xray emission of hot gas which forms an atmosphere within the cluster. The hot gas can also be detected through the decrements which it causes in the Cosmic Microwave Background Radiation as a result of the Sunyaev–Zeldovich effect.
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Clusters of Galaxies
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10.1007/978-3-540-73478-9_4
|
2008-01-01
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Icelandic Andosols form in climatic and geological conditions that are different from those common for Andosol formation, namely a frigid oceanic climate and the steady aeolian addition of fresh and reworked tephra material. Three representative profiles were sampled in different ecological zones of Iceland for -micromorphological studies. They are classified as Orthidystri-Vitric Andosol, -Dystri-Vitric Andosol and Thaptohistic-Vitric Andosol. The parent material consists entirely of relatively young volcanic ashes, and organic layers. Multiple lithological discontinuities are recognised. Microstratification is observed in thin sections, both in organic and inorganic horizons. The coarse mineral fraction is characterised by variable proportions of pumice, different types of glass, hypo- and holocrystalline pyroclasts and euhedral and subhedral crystals of feldspar and augite. Locally, green-grey volcanic glass shows pellicular alteration to an orange component, considered as palagonite. Some more clayey horizons (described as B horizons in the field) consist of soil aggregates or nodules of various compositions, mixed with pyroclasts covered by a coating of micromass. They may represent locally transported material of older, more evolved soils. The microstratification of both organic and mineral material and the (sub)-horizontal orientation of organ and tissue residues points to a gradual deposition of material, with short interruptions, not disturbed by pedoturbation, especially bioturbation. It means that every sub-layer corresponds to a former soil surface in a temporarily relatively stable environment. A weakly developed lenticular or isoband microstructure, pointing to freeze-thawing phenomena, is observed in several -horizons. Capping, often with reverse sorting, observed between 100–230 cm depth on organ residues in one of the profiles are signs of former frost activity. It is perhaps the first time that such cappings are reported on organic components. The relative pureness of most mineral layers, the freshness of the volcanic components and their sorting indicate in many cases direct deposition during eruptions, rather than a water or air transport over land.
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A Micromorphological Study of Andosol Genesis in Iceland
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10.1007/978-3-540-79134-8_5
|
2008-01-01
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We discuss the mechanical, thermal, and electromagnetic properties of a castable microwave absorber consisting of a mixture of stainless steel powder suspended in a commercially available epoxy. The resulting mixture is well suited for cryogenic applications. Its coefficient of thermal expansion closely matches most metals to reduce mechanical strain during cool down. The absorption can be tuned by varying the volume filling fraction of the stainless steel powder in the mixture and exhibits little change from room temperature to 4 K. We provide simple expressions for the real and imaginary parts of the dielectric permittivity as a function of frequency and the stainless steel filling fraction.
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Electromagnetic and Thermal Properties of a Conductively Loaded Epoxy
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10.1007/s10762-007-9299-4
|
2008-01-01
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Pyrene-1-carboxy acid has a p K of 4 in the ground state, and a p K of 8 in the excited state. Fluorescence spectra of the acid and base forms are presented as a function of solvent and temperature. Ab initio quantum calculations indicate that the bond between the ring system and the carboxyl group has aromatic character that becomes stronger upon excitation. This stabilization helps to account for the increase in p K upon excitation.
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Pyrene-1-Carboxylate in Water and Glycerol Solutions: Origin of the Change of pK Upon Excitation
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10.1007/s10895-007-0233-x
|
2008-01-01
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Physical And Engineering Perspectives Of In Vitro Plant Cryopreservation
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10.1007/978-1-4020-3694-1_24
|
|
2007-12-01
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Based on aqueous poly(vinyl alcohol) (PVA) solutions with different content of polymer having different molecular masses and chain tacticity, macroporous viscoelastic gels (PVA cryogels) are prepared in various regimes of freezing-storage in a frozen state-thawing. Shear modulus and fusion temperature of corresponding samples are measured; the structure of thin sections is studied by optical microscopy and the images are processed and analyzed. It is shown that the rigidity and heat endurance of cryogels rise with an increase in the concentration of initial PVA solution and a decrease in the rate of thawing. The influence of the temperature of cryogenic treatment and the PVA molecular mass has an extreme character. At the same time, the effect of the main parameters of cryotropic gelation on the macroporous morphology of PVA cryogels is manifested in the form of more complex dependences because of its multiple-factor character. Therefore, distinct structure-property correlations are not observed in many cases. Cluster analysis of the morphometric characteristics of cryogels in comparison with data on their rigidity makes it possible to classify these systems.
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Study of cryostructuring of polymer systems: 27. Physicochemical properties of poly(vinyl alcohol) cryogels and specific features of their macroporous morphology
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10.1134/S1061933X07060117
|
2007-11-01
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Roles of temperature and hydrostatic stress forces in severe plastic deformation of metal objects are considered. Methods and devices are described that allow the structural states of metal with high mechanical characteristics to be obtained upon plastic deformation at low temperatures under conditions of hydrostatic stress.
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Nanostructurization of metals cryodeformed at hydrostatic stress
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10.1007/s11182-007-0158-5
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2007-11-01
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Development of a cryogenic system and tools for surgery and therapy
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10.1007/s10527-007-0068-4
|
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2007-11-01
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A numerical experiment for description of the critical phenomena in the case of intense heat exchange in flowing-down wave films of a cryogenic liquid on heat-releasing surfaces bounded in length has been carried out. Numerical modeling of the thermal stability of dry spots with heat-transfer conditions determined experimentally yields a satisfactory agreement with the values of the critical heat-flux density obtained in the experiments. This confirms the hypothesis that, in certain regimes of film flow, the development of a crisis is related to the upstream propagation of a temperature disturbance, when the threshold of thermal stability of the dry spots is attained. The value of the critical heat flux is much lower than that calculated from the existing hydrodynamic models.
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Features of the dynamics of development and the thermal stability of dry spots in flowing-down liquid films
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10.1007/s10891-007-0156-z
|
2007-11-01
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A new two-phase cryogenic neutrino detector using electron bubble (e-bubble) specifically in liquid helium is proposed and being developed for real time, high rate measurements of low-energy p-p reaction neutrinos from the sun. The e-bubble detector is a time projection chamber-like (TPC) tracking detector. The task of such a neutrino detector is to detect the ionization of the elastically scattered target electrons by incident neutrinos, and then to characterize their energy and direction and to distinguish them from radioactive backgrounds. The ionization signals are expected to be small and hence undergo avalanche amplification in the saturated vapor above the liquid phase by gas electron multipliers (GEMs) at high gain. Higher granularity and intrinsically suppressed ion feedback give a good spatial resolution and are the major advantages of this technology. It should be possible to construct such a detector to track charged particles down to 100–200 keV in a massive liquid helium target with fractional millimeter spatial resolution in three-dimensional space, using the GEM-based TPC with a high-resolution CCD camera, for both the electronic and light readout.
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Detection of low energy solar neutrinos by a two-phase cryogenic e-bubble detector
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10.1007/s11434-007-0431-6
|
2007-10-01
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Three-dimensional micro-XRF is a recently developed microprobe which facilitates three-dimensional resolved chemical analyses with a resolution of around 20 μm. Arbitrary sites or sections of samples can be investigated without the need to section specimens physically. In this paper we demonstrate the use of the microprobe in combination with a cold nitrogen gas stream for the cryogenic fixation of specimens. A 3D micro-XRF setup at the new microfocus beamline at BESSY II was equipped with a nitrogen cryogenic stream. The distribution of Ca, Fe, Zn and Cu across virtual cross sections of a water-rich sample, the root of common duckweed, could be investigated without further sample preparation. This paper demonstrates the capabilities of 3D micro-XRF under cryogenic conditions for investigations of biological specimens.
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Three-dimensional micro-XRF under cryogenic conditions: a pilot experiment for spatially resolved trace analysis in biological specimens
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10.1007/s00216-007-1494-6
|
2007-10-01
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We develop a high-sensitivity matrix radiometer which will be used on the large altazimuth telescope BTA of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences (Fig. 1) for performing astronomical observations in atmospheric transparency windows in the poorly explored frequency range from 0.13 to 0.38 THz (wavelengths from 2.3 to 0.8 mm). Mounting of the radiometer at the focal point of the 6-m BTA telescope will enhance the capability of the SAO in the transparency windows of the Earth’s atmosphere from the UV range (wavelengths about 3000 Å) up to the ultimate wavelength of the RATAN-600 telescope (about 0.5 m). This will make it possible to perform unique comprehensive multifrequency studies in one observatory. The radiometer is presumed to be used with other radio and optical telescopes, both in the above-mentioned and higher-frequency intervals of the terahertz range.
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High-sensitivity 0.13–0.38-THz matrix radiometer based on superconducting bolometers for the BTA telescope
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10.1007/s11141-007-0077-x
|
2007-10-01
|
Printed circuit board (PCB) recycling is an important challenge for today’s industry. This paper presents results from a study of cryogenic decomposition as a potential alternative recycling method for obsolete printed circuit board scraps. In this method liquid nitrogen is employed as a cryogen to form an environment as low as 77 K for PCB treatment. In order to test the effect of thermal stress set-up during the rapid cryogenic treatment, impact tests were used to simulate the current shredding process. The treated PCB scraps were investigated under a monocular microscope with a 200X magnitude for micro-crack effect observation. Fatigue behavior of the boards was also examined by repeating the cryogenic treatment. The experimental results, as analyzed, demonstrated no obvious support to this alternative PCB recycling method. The energy absorbed during the impact tests for the cryogenically treated boards is insignificantly different from those without the treatment.
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Experimental studies on cryogenic recycling of printed circuit board
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10.1007/s00170-006-0634-z
|
2007-09-01
|
Improving cutters
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10.3103/S1068798X07090146
|
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2007-09-01
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Under macroscopic pin-on-disk testing the sliding friction coefficient of Polytetrafluoroethylene (PTFE) was investigated over a temperature range of approximately 200–400 K. This study examines the nature of the temperature dependence by testing PTFE pins at varying temperature and humidity on a linear reciprocating pin-on-disk tribometer. The friction coefficient increased monotonically with decreasing temperature from μ = 0.075to μ = 0.210 in a manner consistent with thermal activation; it deviated from this trend only during phase and glass transitions in the PTFE and temperatures below the frost-points for the respective environments.
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Macroscopic Evidence of Thermally Activated Friction with Polytetrafluoroethylene
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10.1007/s11249-007-9237-6
|
2007-07-01
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Production processes of electrically active defects in degenerate silicon subjected to 2.5 MeV electron irradiation at T = 4.2 K and T = 300 K have been studied. The production rates of primary and secondary defects in irradiated samples are analyzed on the basis of the known properties of radiation-produced defects in Si. It has been demonstrated that a striking difference in the production rates of electrically active defects in n- and p-Si under irradiation at cryogenic temperatures may be related to the different fate of Frenkel pairs in both materials. The production rate of primary defects in degenerate Si was found to be between 1.5 cm^−1 and 2 cm^−1.
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Comparative studies of defect production in heavily doped silicon under fast electron irradiation at different temperatures
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10.1007/s10854-006-9103-6
|
2007-07-01
|
The dynamic state of helium can be realized employing a centrifugal compressor driven by a turboexpander. An energy-generating cryogenic stage (ECS) has been created that helps produce work for driving a cold turboexpander and simultaneously generating cold for removal of the heat of compression. Optimization calculations of helium cascade akin in heat and power to ECS have been performed. The referred approach can be used as well for creating hydrogen liquefiers with an ECS.
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Optimization of helium refrigerator with an energy-generating cryogenic stage
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10.1007/s10556-007-0083-z
|
2007-07-01
|
An experimental campaign consisting of tensile and fracture tests at cryogenic and room temperatures has been conducted on a Ti–5Al–2.5Sn extra-low-interstitial (ELI) alloy. It has been assessed that, at decreasing testing temperature: Young’s modulus slightly increases; yield and failure strengths increase significantly; fracture toughness decreases. Since a ductile void growth to coalescence micromechanism always governs failure in the spanned temperature interval, crack growth is simulated by allowing for material nonlinearities in the process zone, where ductile tearing takes place. Numerical results have been obtained by modeling the response of the process zone through either a cohesive model or Gurson’s constitutive law for porous-ductile media. It is shown that the latter approach can accurately describe the failure mechanism at any test temperature and for any specimen geometry, whereas the former one is not able to account for stress triaxiality at the crack tip and therefore requires a new calibration anytime the specimen geometry is varied.
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Mechanical characterization of Ti–5Al–2.5Sn ELI alloy at cryogenic and room temperatures
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10.1007/s10704-007-9140-z
|
2007-07-01
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The possibility to assess cold hardening of steels in the presence of stress concentration by means of structural-strength factors used in the engineering practice is considered. A modified system of structural-strength factors is proposed, which allows one to take into account the effect of individual factors (cryogenic temperature, stress concentration, action of electric current pulses) or their combination on the efficiency of steels in the case of inhomogeneous stress.
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Cold hardening of steels under conditions of inhomogeneous stress and action of electric current pulses
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10.1007/s11223-007-0041-1
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