publicationDate stringlengths 10 10 | abstract stringlengths 0 37.3k | title stringlengths 1 5.74k | doi stringlengths 11 47 ⌀ |
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2011-10-01 | An effective countermeasure against vibration under limitation of volume and weight of small satellites is to insert thin polyimide tape between structural elements, especially for structural vibration of a small satellite during its launch. In this study, we deal with three types of aluminum elastic beams clamped on an aluminum rigid base. To explain dynamic damping properties of thin polyimide tapes inserted between structural elements based on our experimental data, we first develop a mathematical model, which can be applied to FEM analysis. Although this model generally depends on both the number of laminated tape layers and frequency, it shall be modified to a special model, which only depends on frequency but not depend on the number of layers. Finally, using a new test beam, the validity of the proposed mathematical model is demonstrated. | A New Approach to Vibration Reduction Analysis Using Thin Polyimide Tape Inserted between Structural Elements | 10.1007/s11340-010-9447-y |
2011-10-01 | This paper addresses the time history finite element analysis of rock-structure interaction. Modeled is not only the lateral energy dissipation, but also the interaction between the far field and the numerical model itself. This is accomplished by a preliminary analysis of the far field as a shear beam (for lateral excitation), and then velocities and displacements are transferred to the model as nodal forces through damping and stiffness matrices respectively. Details of the finite element implementation are given, along with an extensive series of simulations comparing this method, with the one of Lysmer for both 2D and 3D models. The model is derived from the principle of virtual work, and its implementation does not require any modification of existing finite element codes, only clever pre and postprocessing of results are needed. | A simplified 3D model for soil-structure interaction with radiation damping and free field input | 10.1007/s10518-011-9261-7 |
2011-10-01 | Across-wind loads and effects have become increasingly important factors in the structural design of super-tall buildings and structures with increasing height. Across-wind loads and effects of tall buildings and structures are believed to be excited by inflow turbulence, wake, and inflow-structure interaction, which are very complicated. Although researchers have been focusing on the problem for over 30 years, the database of across-wind loads and effects and the computation methods of equivalent static wind loads have not yet been developed, most countries having no related rules in the load codes. Research results on the across-wind effects of tall buildings and structures mainly involve the determination of across-wind aerodynamic forces and across-wind aerodynamic damping, development of their databases, theoretical methods of equivalent static wind loads, and so on. In this paper we first review the current research on across-wind loads and effects of super-tall buildings and structures both at home and abroad. Then we present the results of our study. Finally, we illustrate a case study in which our research results are applied to a typical super-tall structure. | Across-wind loads and effects of super-tall buildings and structures | 10.1007/s11431-011-4543-5 |
2011-10-01 | The direct displacement based seismic design procedure utilises equivalent viscous damping expressions to represent the effect of energy dissipation of a structural system. Various expressions for the equivalent viscous damping of different structural systems are available in the literature, but the structural systems examined in the past have not included concentrically braced frame structures. Thus, this study describes the development of an equivalent viscous damping equation for concentrically braced frame structures based on the hysteretic response of 15 different single storey models. Initially, equivalent viscous damping is calculated based on the area based approach and then corrected for the earthquake excitation. An iterative procedure is adopted to calibrate the equivalent viscous damping expression to the results of inelastic time history analyses using a number of spectrum-compatible real accelerograms. From the results of this research, a new damping expression is developed as a function of the ductility and the non dimensional slenderness ratio. | Equivalent viscous damping for steel concentrically braced frame structures | 10.1007/s10518-011-9272-4 |
2011-10-01 | The radial trends of vibrational properties, represented by the specific dynamic modulus ( E ′/ ρ ) and damping coefficient (tan δ ), were investigated for three tropical rainforest hardwood species ( Simarouba amara , Carapa procera , and Symphonia globulifera ) using free-free flexural vibration tests. The microfibril angle (MFA) was estimated using X-ray diffraction. Consistent patterns of radial variations were observed for all studied properties. E ′/ ρ was found to decrease from pith to bark, which was strongly related to the increasing pith-bark trend of MFA. The variation of tan δ along the radius could be partly explained by MFA and partly by the gradient of extractives due to heartwood formation. The coupling effect of MFA and extractives could be separated through analysis of the log(tan δ ) versus log( E ′/ ρ ) diagram. For the species studied, the extractive content putatively associated with heartwood formation generally tends to decrease the wood damping coefficient. However, this weakening effect of extractives was not observed for the inner part of the heartwood, suggesting that the mechanical action of extractives was reduced during their chemical ageing. | Radial variations of vibrational properties of three tropical woods | 10.1007/s10086-011-1189-7 |
2011-10-01 | The pathophysiology of l -dopa-induced dyskinesias (LIDs) in Parkinson’s disease (PD) remains poorly understood. The presence of superimposed LIDs clearly differentiates motor performance of dyskinetic from non-dyskinetic PD subjects when they are on medication, but here, we investigated whether their respective motor performance differs while subjects are off l -dopa medication and LIDs are not apparent. We assessed the motor performance of nine dyskinetic and ten non-dyskinetic PD subjects off l -dopa, and of ten age-matched control subjects, during a visually guided tracking task. As previous studies have suggested that linear dynamical system (LDS) models are useful to assess motor performance in PD in addition to overall tracking error, we used LDS models to assess the damping ratio parameter of motor behavior while controlling for disease severity. While overall tracking error did not significantly differ across groups, dyskinetic PD subjects demonstrated a significantly decreased mean damping ratio compared with control and non-dyskinetic PD subjects. For both groups, greater disease severity significantly predicted a lower damping ratio, but even after controlling for disease severity, the damping ratio for dyskinetic subjects was significantly lower. Our results demonstrate, somewhat counter-intuitively, that motor performance of dyskinetic and non-dyskinetic PD subjects differ, even off l -dopa when no dyskinesias are seen. A decreased damping ratio is indicative of a tendency to overshoot a target during motor performance, similar to the dysmetria found in cerebellar patients. We discuss the possibility of motor abnormalities in dyskinetic PD patients off medication in relation to altered functional cerebellar changes described in PD. | Dyskinetic Parkinson’s disease patients demonstrate motor abnormalities off medication | 10.1007/s00221-011-2845-2 |
2011-10-01 | Effects of soil pH on damping-off of sugar beet by R. solani (AG2-2) and soil suppressiveness against the disease were studied by comparing disease incidences in pasteurized versus non-pasteurized, infested soils. Soil pH was correlated neither to disease incidence in five soils ranging from pH 4.5 to 7.2 nor to indigenous disease suppressiveness, the difference in disease incidences between non-treated soil and its pasteurized counterpart. When an alkaline soil was acidified with H_2SO_4, disease suppression markedly declined, increasing disease incidence in the non-pasteurized soil. Inversely, disease suppression was enhanced when an acidic soil was neutralized by adding Ca(OH)_2. Soil amendment with dried peanut plant residue suppressed the disease in two pasteurized, near-neutral soils, lowering the incidence to the levels in the non-pasteurized soils, but was less effective in two pasteurized, acidic soils. In vitro mycelial growth of the pathogen and seedling growth was optimal at pH 4.5–5.5 and 6.0–6.5, respectively, and declined as the pH became higher or lower. (Conclusions) These results suggest that the seedlings were inhibited more than the pathogen at low pH, and that indigenous disease suppressiveness through the activity of antagonistic soil microorganisms operates effectively in near-alkaline soils, but is weakened or nullified in acidic soils. | Effects of soil pH on rhizoctonia damping-off of sugar beet and disease suppression induced by soil amendment with crop residues | 10.1007/s11104-011-0843-6 |
2011-10-01 | The active damping of the resonant vibrations of a hinged flexible viscoelastic rectangular plate with distributed piezoelectric sensors and actuators is considered. It is shown that it is possible to considerably decrease the amplitude of resonant vibrations by choosing the appropriate feedback factor. The collective effect of geometrical nonlinearity and dissipative properties of the material on the effectiveness of active damping of the resonance vibrations of rectangular plates with sensors and actuators is analyzed | Active damping of the resonant vibrations of a flexible viscoelastic rectangular plate | 10.1007/s10778-011-0472-z |
2011-10-01 | Possible interactions between seismic early warning systems and structural control are herein investigated. A SEWS can provide the knowledge of some parameters, ahead of time, of the seismic event that is going to occur in a certain site. Current research activities on SEWS include the estimate of the anticipated peak ground acceleration (PGA) and the acceleration response spectrum (S_a) of an incoming earthquake. This paper proposes the exploitation of this information in the framework of semi-active (SA) control strategies, by using magnetorheological dampers. The latter are time-varying properties devices able to achieve a wide range of physical behaviours using low-power electrical currents. The main idea of this work consists in changing the MR damper behaviour according to the forecasted intensity of an incoming earthquake provided by the SEWS, in order to obtain the optimal seismic response of the hosting structure. This is investigated assuming a case-study problem. It consists in the 91/5 highway bridge located in Orange County of southern California and proposed in literature as a benchmark structure for applications in the field of structural control. The effectiveness of the proposed control strategy is assessed and compared to more consolidated control techniques. | Semi-active control of the benchmark highway bridge based on seismic early warning systems | 10.1007/s10518-011-9259-1 |
2011-09-27 | A simple method for measuring amide hydrogen exchange rates is presented, which is based on the selective inversion of water magnetization with the use of radiation damping. Simulations show that accurate exchange rates can be measured despite the complications of radiation damping and cross relaxation to the exchange process between amide and water protons. This method cannot eliminate the contributions of the exchange-relayed NOE and direct NOE to the measured exchange rates, but minimize the direct NOE contribution. In addition, the amides with a significant amount of such indirect contributions are possible to be identified from the shape of the exchange peak intensity profiles or/and from the apparent relaxation rates of amide protons which are extracted from fitting the intensity profiles to an equation established here for our experiment. The method was tested on ubiquitin and also applied to an acyl carrier protein. The amide exchange rates for the acyl carrier protein at two pHs indicate that the entire protein is highly dynamic on the second timescale. Low protection factors for the residues in the regular secondary structural elements also suggest the presence of invisible unfolded species. The highly dynamic nature of the acyl carrier protein may be crucial for its interactions with its substrate and enzymes. | Measurement of amide hydrogen exchange rates with the use of radiation damping | 10.1007/s10858-011-9549-6 |
2011-09-01 | A DC hybrid power source composed of photovoltaic cells as the main power source, Li-ion battery storage as the secondary power source, and power electronic interface, is modeled based on port-controlled Hamiltonian systems and Euler-Lagrange framework. Subsequently, passivity-based controllers are synthesized. Local asymptotic stability is ensured as well. In addition, a power management system is designed to manage power flow between components. Modeling and simulation of the proposed hybrid power source is accomplished using MATLAB/Simulink. Our interest is focused on the comparison of the two passivity-based control methods and their use in hybrid power systems. | Interconnection and damping assignment and Euler-Lagrange passivity-based control of photovoltaic/battery hybrid power source for stand-alone applications | 10.1631/jzus.C1000368 |
2011-09-01 | Air-foil bearings (AFBs) are self acting hydrodynamic bearings made from sheet metal foils comprised of at least two layers. The innermost “top foil” layer traps a gas pressure film that supports a load while the layer or layers underneath provide an elastic foundation. AFBs are currently used in many commercial applications, both terrestrial and in aerospace. AFBs provide a means to eliminate the oil system leading to reduce weight and enhanced temperature capability. Regardless of the application of the AFBs, the identification of the structural characteristics is important for successful design practice. In the present work, structural characteristics (stiffness and damping) of axial AFBs are indentified in the light of experimental results. Due to the initial high torque requirement of the AFB, the experimental setup using a single AFB is proposed instead of standard two-foil bearing setups. Experiments are carried out at maximum speed of 60,000 rpm. Sub-structuring approach is used for identification of the structural (stiffness and damping) characteristics of the AFB. The results have shown that the developed experimental procedure is able to identify the stiffness and damping characteristics of axial AFBs accurately. | Identification of stiffness and damping characteristics of axial air-foil bearings | 10.1007/s10999-011-9161-7 |
2011-09-01 | Calculation formulas were obtained for determining the shape of an acoustic pulse radiated by a piezoelectric plate that has a mechanical damper and a correcting electric circuit and is excited by electric pulses with durations that are multiples of an integer number of half periods at the antiresonance frequency ω_0. Calculations were performed for particular cases when either an electric circuit or a damper is present. The optimal parameters of the electric circuit that provide the shortest duration of radiated signals were determined. The durations and amplitudes of radiated signals obtained using the damper or the electric circuit were compared. Conclusions concerning the degree of efficiency of applying an electric RL load were made. | Possibilities for reducing the duration of acoustic pulses generated by a piezoelectric plate using a damper or an electric RL circuit for a plate excited by electric pulses of different durations | 10.1134/S1061830911090063 |
2011-09-01 | The optimisation of earthquake resistance of high buildings by multi-tuned mass dampers was investigated using bionic algorithms. In bionic or evolutionary optimisation studies the properties of parents are crossed and mutated to produce a new generation with slightly different properties. The kids which best satisfy the object of the study, become the parents of the next generation. After a series of generations essential improvements of the object may be observed. Tuned mass dampers are widely used to reduce the impact of dynamic excitations on structures. A single mass system and multi-mass oscillators help to explain the mechanics of the dampers. To apply the bionic optimisation strategy to high buildings with passive tuned mass dampers subject to seismic loading a special beam element has been developed. In addition to the 6 degrees of freedom of a conventional beam element, it has 2 degrees of freedom for the displacements of the dampers. It allows for fast studies of many variants. As central result, efficient designs for damping systems along the height of an edifice are found. The impact on the structure may be reduced essentially by the use of such dampers designed to interact in an optimal way. | Bionic optimisation of the earthquake resistance of high buildings by tuned mass dampers | 10.1016/S1672-6529(11)60036-X |
2011-08-20 | In this paper, a small displacement-type magnetorheological grease (MRG) damper based on disk squeeze mode is proposed. The squeeze flow differential equation is obtained. The Navier slip condition is considered on the surfaces and the boundary compatible condition is established. The radial velocity profiles and the radial pressure distributions are derived respectively, and the mathematical stress expression is calculated. To verify rationality of analytical method, the MRG damper is designed and fabricated according to the technical requirements of an engine vibration isolation system. The experimental damping force from MTS870 Electrohydraulic Servo with sine wave excitation shows that the proposed analytical method is feasible and provides the reference value for designing MRG damper based on disk squeeze mode. | Analytical study on damping performances of magnetorheological grease damper based on disk squeeze mode and experimental test | 10.1007/s11465-011-0235-x |
2011-08-01 | The linear and nonlinear steady-state viscosities and elastic compliances were measured in shear and elongational flows for two low-density polyethylenes, a linear polypropylene, and two metallocene catalyzed polyethylenes (one linear and one long-chain branched) by Wolff et al. (Rheol Acta 49:95–103, 2010 ) and Resch (dissertation, 2010 ). Comprehensive data of this type are rarely found in the literature, and comprehensive modeling of both viscous and elastic effects is even rarer. In this contribution, the reliability of a modeling approach proposed by Laun (J Rheol 30(3):459–501, 1986 ) and based on the damping function concept is tested. The strain hardening seen for the long-chain branched polymers and its absence in the case of the linear polymer, the stronger decrease of the tensile compliance in comparison to the shear compliance with increasing stress, as well as the extended linear-viscoelastic regime of the shear viscosity in contrast to the shear compliance are correctly modeled. While the modeling of the nonlinear response in shear can be achieved with only one material parameter for most of the polymers considered here, the nonlinear modeling in elongation is achieved with two parameters. The same parameter values are shown to describe viscous as well as elastic properties of the melts, and thus the relations of Laun can be used to test the consistency of viscosity and compliance measurements. | Prediction of steady-state viscous and elastic properties of polyolefin melts in shear and elongation | 10.1007/s00397-011-0546-1 |
2011-08-01 | This paper investigates the dynamics of frictional-type winding mechanisms widely used in textile industry. The mechanism under study is used to wind various kinds of thread onto bobbins of cylindrical form. The system essentially consists of a motor-driven cylinder which is pressed to a cylindrical bobbin hence bringing the latter into rotation through friction between the two surfaces. A textile thread is supplied into the contact zone and winds around the bobbin. For the winding operation to proceed accurately, the winding mechanism must be free of vibrations to ensure a constant and reliable contact zone. Proposed in the paper is a comprehensive dynamic model that accounts for as many as six degrees of freedom of the mechanism. Six position variables therefore are selected for the generalized coordinates of the system and Lagrangian approach is employed to obtain six differential equations of motion of the system. The obtained equations are highly nonlinear and are solved numerically for typical values of the system’s design parameters. The proposed model and analysis allow the designer to account for all the main factors that affect mechanical and technological characteristics of the mechanism. | Lagrangian modeling and analysis of the dynamics of frictional winding mechanisms | 10.1007/s11044-011-9254-y |
2011-08-01 | The performance of surface damping treatments may vary once the surface is exposed to a wide range of temperatures, because the performance of viscoelastic damping material is highly dependent on operational temperature. In addition, experimental data for dynamic responses of viscoelastic material are inherently random, which makes it difficult to design a robust damping layout. In this paper a statistical modeling procedure with a statistical calibration method is suggested for the variability characterization of viscoelastic damping material in constrained-layer damping structures. First, the viscoelastic material property is decomposed into two sources: (i) a random complex modulus due to operational temperature variability, and (ii) experimental/model errors in the complex modulus. Next, the variability in the damping material property is obtained using the statistical calibration method by solving an unconstrained optimization problem with a likelihood function metric. Two case studies are considered to show the influence of the material variability on the acoustic performances in the structural-acoustic systems. It is shown that the variability of the damping material is propagated to that of the acoustic performances in the systems. Finally, robust and reliable damping layout designs of the two case studies are obtained through the reliability-based design optimization (RBDO) amidst severe variability in operational temperature and the damping material. | A statistical characterization method for damping material properties and its application to structural-acoustic system design | 10.1007/s12206-011-0517-6 |
2011-08-01 | The mechanical properties of elastomers can change significantly due to air temperature variations. In particular, prolonged exposure to subzero temperatures can result in rubber crystallization, with a considerable increase in the shear stiffness of the material. As a result, the seismic response of structures with elastomeric isolators can be strongly influenced by air temperature. Current seismic codes, indeed, require an upper and lower bound analysis, using suitable modification factors, to account for the changes in the cyclic behavior of elastomeric isolators due to air temperature variations. In this study, the sensitivity of the cyclic behavior of elastomeric isolators to air temperature variations is investigated based on the experimental results of an extensive test program on six different elastomeric compounds for seismic isolators, characterized by a shear modulus ranging from 0.5 to 1.2 MPa at 100% shear strain and 20°C. The cyclic tests have been performed on small-size specimens, subjected to shear strain amplitudes and frequency of loading typical for elastomeric seismic isolators, at seven different air temperatures, ranging from 40 to −20°C. The effects of rubber crystallization due to prolonged exposure to low-temperatures have been also investigated. A finite element model for the evaluation of the temperature contour map inside a full-size elastomeric isolator exposed to low air temperatures has been also developed. In the paper, the experimental outcomes are compared with the modification factors provided by the current seismic codes to account for the temperature effects on the mechanical properties of elastomeric isolators. | Effects of air temperature on the cyclic behavior of elastomeric seismic isolators | 10.1007/s10518-011-9244-8 |
2011-08-01 | This paper considers the main patterns of damping of stress waves in disperse and semi-rock soils. We determined two strain thresholds, beyond which the damping ratio qualitatively changes: in the region of relative deformations up to 10^−4 the damping ratio can be considered to be constant and is caused by non-ideal elasticity and viscous losses; beyond this strain threshold the damping monotonically increases due to initial plastic soil deformations; in the region of moderate-level shear deformations the increase of the damping ratio slows for relative shear deformations higher than 0.002, primarily because of the rapid decrease of the fraction of the damping due to non-ideal soil elasticity and heat losses in the course of degradation of structural bonds. | The nature and patterns of damping of stress waves in soils | 10.3103/S0145875211040120 |
2011-08-01 | An analytical approximate method for strongly nonlinear damped oscillators is proposed. By introducing phase and amplitude of oscillation as well as a bookkeeping parameter, we rewrite the governing equation into a partial differential equation with solution being a periodic function of the phase. Based on combination of the Newton’s method with the harmonic balance method, the partial differential equation is transformed into a set of linear ordinary differential equations in terms of harmonic coefficients, which can further be converted into systems of linear algebraic equations by using the bookkeeping parameter expansion. Only a few iterations can provide very accurate approximate analytical solutions even if the nonlinearity and damping are significant. The method can be applied to general oscillators with odd nonlinearities as well as even ones even without linear restoring force. Three examples are presented to illustrate the usefulness and effectiveness of the proposed method. | Construction of approximate analytical solutions to strongly nonlinear damped oscillators | 10.1007/s00419-010-0465-0 |
2011-08-01 | Anthracycline antibiotics are inducers of an immunogenic form of apoptosis that has immunostimulatory properties because of the release of damage-associated molecular patterns. To study the mechanisms used by the innate immune system to sense this immunogenic form of cell death, we established an in vivo model of cell death induced by intraperitoneal injection of doxorubicin, a prototype of anthracyclines. The acute sterile inflammation in this model is characterized by rapid influx of neutrophils and increased levels of IL-6 and monocyte chemotactic protein-1. We demonstrate that acute inflammation induced by doxorubicin is associated with apoptosis of monocytes/macrophages and that it is specific for doxorubicin, an immunogenic chemotherapeutic. Further, the inflammatory response is significantly reduced in mice deficient in myeloid differentiation primary response gene 88 (MyD88), TLR-2 or TLR-9. Importantly, a TLR-9 antagonist reduces the recruitment of neutrophils induced by doxorubicin. By contrast, the acute inflammatory response is not affected in TRIF^Lps2 mutant mice and in TLR-3, TLR-4 and caspase-1 knockout mice, which shows that the inflammasome does not have a major role in doxorubicin-induced acute inflammation. Our findings provide important new insights into how the innate immune system senses immunogenic apoptotic cells and clearly demonstrate that the TLR-2/TLR-9-MyD88 signaling pathways have a central role in initiating the acute inflammatory response to this immunogenic form of apoptosis. | TLR-2 and TLR-9 are sensors of apoptosis in a mouse model of doxorubicin-induced acute inflammation | 10.1038/cdd.2011.4 |
2011-07-01 | A mechanism for the excitation of piston rod vibrations in automotive damper modules is discussed by a simple model. An improved nonlinear model based on elasticity effects leads to good simulation results. It is shown theoretically and experimentally that the adaptation of the stiffness of the piston rod bushing to the “stiffness” of the damper force characteristic can eliminate the piston rod oscillations completely. | Damper modules with adapted stiffness ratio | 10.1007/s00419-010-0455-2 |
2011-07-01 | At high operational speeds, the train system becomes very sensitive to parameter variations of components. Therefore, it is imperative to incorporate more accurate component models in the vehicle dynamics studies. This study addresses a more subtle and comprehensive non-linear parametric model of a high-speed rail hydraulic yaw damper. A new concept of a hydraulic yaw damper model is suggested, in which the small mounting clearance, the series stiffness, and the viscous damping are built in. The series stiffness is the tandem result of the dynamic oil stiffness, the rubber attachment stiffness, and the mounting seat stiffness. A dynamic oil property model is established and coupled to the entire modelling process, in which the density, the dynamic viscosity, the volumetric elastic modulus, and the stiffness of the oil are all changeable in terms of the instantaneous working pressure, the oil temperature, and the entrapped air ratio of the oil. The dynamic flow loss and the valve system dynamics are also incorporated. Experiments validated that the established non-linear parametric model is accurate and robust in predicting the damping characteristics within an extremely wide speed range. The validated damper model was then successfully applied to a thorough parameter sensitivity analysis and damping nature prediction under practical, in-service conditions. The established damper model couples all the main influential factors that are not or are insufficiently considered in normal-speed problems; thus, it will be more accurate and appropriate for furthering high-speed problem studies. | Non-linear parametric modelling of a high-speed rail hydraulic yaw damper with series clearance and stiffness | 10.1007/s11071-010-9871-7 |
2011-07-01 | Under the assumptions of classical linearised water-wave theory, the time-harmonic two-dimensional motion of a rigid body floating in the surface of a fluid may be characterised by various coefficients which express components of the hydrodynamic forces acting on that body. For a single body in isolation, these are relatively simple to calculate. For bodies placed next to a vertical wall, the corresponding calculations are often much more complicated. In this paper the well-known wide-spacing approximation is used to develop approximations to the hydrodynamic coefficients for a body having a vertical plane of symmetry, but otherwise of arbitrary cross-section, next to a wall solely in terms of the results for an isolated body. Exact results are compared with the wide-spacing approximations for semi-immersed circular cylinders and cylinders of rectangular cross-section. They show that the approximation works remarkably well over all frequency ranges and even when the cylinders are very close to the wall. | Estimation of wall effects on floating cylinders | 10.1007/s10665-010-9420-x |
2011-07-01 | In this article, an advanced laminated composite is developed, combining the high damping properties of shape memory alloy (SMA) with mechanical properties and light weight of a glass-fiber reinforced polymer. The composite is formed by stacking a glass-fiber reinforced epoxy core between two thin patterned strips of SMA alloy, and two further layers of fiber-glass reinforced epoxy. The bars of the laminated composite were assembled and cured in autoclave. The patterning was designed to enhance the interface adhesion between matrix and SMA inserts and optimally exploit the damping capacity of the SMA thin ribbons. The patterned ribbons of the SMA alloy were cut by means of a pulsed fiber laser source. Damping properties at different amplitudes on full scale samples were investigated at room temperature with a universal testing machine through dynamic tension tests, while temperature dependence was investigated by dynamic mechanical analyses (DMA) on smaller samples. Experimental results were used in conjunction with FEM analysis to optimize the geometry of the inserts. Experimental decay tests on the laminated composite have been carried out to identify the adimensional damping value related to their first flexural mode. | Simulated and Experimental Damping Properties of a SMA/Fiber Glass Laminated Composite | 10.1007/s11665-011-9887-2 |
2011-07-01 | Nowadays, many manufacturing processes require the machining of complex forms with a high aspect ratio or cavities. Tools with a long overhang length are a common method to meet these requirements. Typical examples for this are boring bars for bore-turning and the milling with very long cutters. These tools tend to vibrate strongly due to their slender shape. The stress-induced transformation of austenite to martensite and the distinctive hysteresis loop allow the NiTi shape memory alloys (SMA) to absorb vibration energy. This article describes the innovative approach to dampen process vibrations by coating the tool shafts of cutting tools with long overhang with NiTi thin films. It explores how these thin films can be applied on polished tungsten carbide shafts and how their modal parameters are modified by these coatings. In a further step, this knowledge is used to calculate stability charts of corresponding machining processes. The study reported in this article identified the stabilizing effects of coatings with a thickness of 2-4 μm on milling processes. The minimum stability limit was increased by up to 200%. | Processing and Damping Properties of Sputtered NiTi Thin Films for Tools in Machining Processes | 10.1007/s11665-011-9847-x |
2011-07-01 | Dampness is a common condition in old buildings and, accordingly, many paint systems specific for this type of building allow for application on walls with nonnegligible moisture content. In spite of that, performance evaluation of these paints is normally carried out using dry substrates or even on free paint films. This article presents research performed on 16 commercial paint systems: seven silicate, three silicone, three hydro-pliolite and two lime-based systems, as well as one common vinyl emulsion paint that served as reference. Each paint was applied and cured both on dry and on damp mortar substrates. The test specimens were subjected to water vapor permeability tests and evaporative drying tests. The following conclusions could be drawn: (i) the way paint systems influence the drying of the substrate, to which they were applied and where they cured, may vary significantly depending on the moisture content of that substrate; (ii) vapor permeability, measured with specimens applied and cured on dry substrate, may be an acceptable way of predicting a paint’s influence on drying, provided that the paints are applied and cured on dry substrate or that their characteristics are not significantly affected by the moisture content of that substrate. | Coatings applied on damp building substrates: performance and influence on moisture transport | 10.1007/s11998-010-9319-5 |
2011-07-01 | A series of polyurethane (PU) samples based on poly(tetramethylene glycol)/epoxy resin (EP) graft interpenetrating polymer networks (IPNs) were prepared and their damping, thermal, and mechanical properties were systematically studied in terms of composition and the value of the PU isocyanate index ( R ). The damping properties and thermal stability measurements revealed that the formation of PU/EP IPN could improve not only the damping capacity but also the thermal stability. Meanwhile, mechanical tests showed that the tensile strengths of the IPNs decreased while their impact strengths increased with increasing PU content. The value of R also had significant impacts on the properties of the IPNs when the PU and EP ratio was fixed, which could be an effective means for manipulating the fabrication of PU/EP IPNs. The morphologies of the PU/EP IPNs were observed by SEM and AFM characterization and the relationship between the morphologies and properties is discussed. With the results in hand, the PU/EP IPNs hold promise for use in structural damping materials. | Damping, thermal, and mechanical properties of polyurethane based on poly(tetramethylene glycol)/epoxy interpenetrating polymer networks: effects of composition and isocyanate index | 10.1007/s00339-010-6153-7 |
2011-06-01 | The plasmonic spectra of solution phase ensembles of triangular silver nanoplates have been analysed in order to examine the fundamental properties underlying their size-dependent enhanced refractive index sensitivities. Linewidth studies highlight variations in the response of these solution phase nanostructures to those previously reported for single immobilized triangular nanostructures. The observation of insignificant broadening of the resonance linewidth for larger edge length nanoplates highlights minimal contribution of radiative damping processes at these dimensions. Comparative single nanoplate studies using discrete dipole approximations were performed to analyse the dephasing processes contributing to these reduced linewidths and to determine the key parameters defining the underlying plasmonic response. These single nanoplate approximations highlight the dominance of absorption processes over radiative processes and demonstrate that this dominance can be attributed to the platelet nature/geometry of the nanoplates. These calculations indicate that the higher aspect ratio allows for the maintenance of coherent plasmon oscillations as the edge length of the triangular platelet increases within the sols. Thickness studies verify that this reduction in radiation damping is due to high aspect ratio and can act to confine electromagnetic fields at the nanoplate surface, thereby increasing near-field enhancement and hence the resultant plasmonic refractive index sensitivity. | Scaling of Surface Plasmon Resonances in Triangular Silver Nanoplate Sols for Enhanced Refractive Index Sensing | 10.1007/s11468-011-9211-x |
2011-06-01 | Although all known materials have internal damping that leads to energy dissipation, most existing large deformation visco-elastic finite element formulations are based on linear constitutive models or on nonlinear constitutive models that can be used in the framework of an incremental co-rotational finite element solution procedure. In this investigation, a new nonlinear objective visco-elastic constitutive model that can be implemented in non-incremental large rotation and large deformation finite element formulations is developed. This new model is based on developing a simple linear relationship between the damping forces and the rates of deformation vector gradients. The deformation vector gradients can be defined using the decomposition of the matrix of position vector gradients. In this paper, the decomposition associated with the use of the tangent frame that is equivalent to the QR decomposition is employed to define the matrix of deformation gradients that enter into the formulation of the viso-elastic constitutive model developed in this investigation. Using the relationship between the deformation gradients and the components of the Green–Lagrange strain tensor, it is shown that the damping forces depend nonlinearly on the strains and linearly on the classical strain rates. The relationship between the damping forces and strains and their rates is used to develop a new visco-elastic model that satisfies the objectivity requirements and leads to zero strain rates under an arbitrary rigid body displacement. The linear visco-elastic Kelvin–Voigt model frequently used in the literature can be obtained as a special case of the proposed nonlinear model when only two visco-elastic coefficients are used. As demonstrated in this paper, the use of two visco-elastic coefficients only leads to viscous coupling between the deformation gradients. The model developed in this investigation can be used in the framework of large deformation and large rotation non-incremental solution procedure without the need for using existing co-rotational finite element formulations. The finite element absolute nodal coordinate formulation (ANCF) that allows for straightforward implementation of general constitutive material models is used in the validation of the proposed visco-elastic model. A comparison with the linear visco-elastic model is also made in this study. The results obtained in this investigation show that there is a good agreement between the solutions obtained using the proposed nonlinear model and the linear model in the case of small deformations. | A nonlinear visco-elastic constitutive model for large rotation finite element formulations | 10.1007/s11044-011-9244-0 |
2011-06-01 | Reduction of the vibration noise from submarine propellers is of interest in naval operations. Such an objective can be achieved via the use of materials with the ability to dissipate energy of vibration by means of heat, i.e. high damping materials. An additional problem is that the extreme hydrostatic pressure environment of a submarine requires the chosen material to exhibit considerably high stiffness. Most materials demonstrate a compromise between the two properties, i.e. stiffness and damping. This paper aims to discuss research into high stiffness and high damping materials conducted using a dynamic mechanical analyzer (DMA) under variations of testing temperature, frequency, and strain amplitude. Alloys of nickel aluminum bronze and indium tin are the subjects of this study. Defect damping represents a large portion of the overall damping properties of the nickel aluminum bronze while increasing indium content is shown to boost the damping properties of the indium tin alloy. The study then continues with the development of a new material that combines both indium alloying and defects introduction into the nickel aluminum bronze alloy. The new alloy is observed to have high damping, as measured in its high tan δ, with minimum reduction of the stiffness | E *|. | Improvement of viscoelastic damping in nickel aluminum bronze by indium-tin | 10.1007/s12540-011-0619-9 |
2011-06-01 | We report on a new design for an ILC 3.2 km damping ring, with 2 arcs based on the FODO cell and 2 straight sections that are nearly the same as the newest version of the 6.4 km ring DCO4. This new lattice requires fewer magnets and a lower RF voltage, and has a better dynamic aperture than DCO4 while maintaining flexibility in regard to the momentum compaction factor. So far, this design is the only one satisfying all the requirements for a 3.2 km ring. The work on the lattice design and the dynamic aperture study is presented in detail. | ILC 3.2 km damping ring design based on the FODO cell | 10.1007/s11434-011-4483-2 |
2011-06-01 | Based on the principles of electrical conduction and transformation, a model was put forward for the electrical conversion of piezoelectric damping composites, and a related formula was derived. The results show that the best effect of conversion can be achieved by reducing the imaginary part of the impedance and matching the frequency. The optimal damping effect at a certain frequency requires resistance of conductive phase ( R ) satisfying the condition of R =1/( ωC ), but this condition may cause the damping effect at other frequencies to deviate away from the optimum condition. It is suggested that in order to make the damping effect more efficient and objective, frequency matching should be considered during the design of piezoelectric damping composites. | Theoretical analysis of the conversion from electrical into thermal energy in piezoelectric-conductive damping composites | 10.1007/BF03325751 |
2011-06-01 | The paper presents a general approach to the paradox of Nicolai and related effects analyzed as a singularity of the stability boundary. We study potential systems with arbitrary degrees of freedom and two coincident eigenfrequencies disturbed by small non-conservative positional and damping forces. The instability region is obtained in the form of a cone having a finite discontinuous increase in the general case when arbitrarily small damping is introduced. This is a new destabilization phenomenon, which is similar to well-known Ziegler’s paradox or the effect of the discontinuous increase of the combination resonance region due to addition of infinitesimal damping. It is shown that only for specific ratios of damping coefficients, the system is stabilized due to presence of small damping. Then, we consider the paradox of Nicolai: the instability of a uniform axisymmetric elastic column loaded by axial force and a tangential torque of arbitrarily small magnitude. We extend the results of Nicolai showing that the column is stabilized by general small geometric imperfections and internal and external damping forces. It is shown that the paradox of Nicolai is related to the conical singularity of the stability boundary which transforms to a hyperboloid with the addition of small dissipation. As a specific example of imperfections, we study the case when cross-section of the column is changed from a circular to elliptic form. | Paradox of Nicolai and related effects | 10.1007/s00033-011-0127-2 |
2011-06-01 | The specific features of the influence of such factors as the damping of a longitudinal wave in a medium, its transformation into a transverse wave during transmission, and the radiation directivity of array elements on the characteristics of a signal of a normal linear phased-array transducer are considered. Very simple methods for taking these factors into account are presented. It is noted that increasing the dimensions of array elements may lead to a significant reduction of the amplitude of the total transmitted signal in the transducer near-field zone. | On the influence of certain factors on the characteristics of a signal from a normal linear phased-array transducer in the transmission mode | 10.1134/S1061830911060052 |
2011-06-01 | The efficiency of an acceleration-feedback controlled frictional electromagnetic damper is proved. An oscillator with a controlled damper is modeled by three ordinary differential equations of the first order with discontinuous right-hand side. An oscillator with acceleration-dependent energy dissipation is described by a simpler model: one equation of the second order with discontinuous coefficients. The exact solution of this equation is found. An approximate law of damping is established. It is shown that the damping parameter is in the base of the exponential function. Double nonstationaryphase–frequency resonance is examined | Modeling a vibrating mechanical system with an acceleration-feedback controlled frictional electromagnetic damper | 10.1007/s10778-011-0447-0 |
2011-05-01 | In this paper, the behaviour of a real geogrids reinforced embankment will be analysed based on the results of numeric modelling in seismic conditions. The reinforced slope is analysed using commercial software based on the finite differences method. After the program presentation, is described the methodology of analysis. In modelling, will be devoted special relevance to the behaviour of the structures in terms of deformations, using comparative analyses with different damping ratio values for soils and for reinforcements. Finally, will be drawn some conclusions concerning the behaviour of reinforced structures and in particular, the role of the structural reinforcement’s damping. | Role of the Damping Ratio of Reinforcement on the Behaviour of Geogrids-Reinforced Systems | 10.1007/s10706-010-9383-8 |
2011-05-01 | Oscillators with a non-negative real-power restoring force and quadratic damping are considered in this paper. The equation of motion is transformed into a linear first-order differential equation for the kinetic energy. The expressions for the energy-displacement function are derived as well as the closed form exact solutions for the relationship between subsequent amplitudes. They are expressed in terms of incomplete Gamma functions. On the basis of these results, expressions for the phase trajectories and the loci of maximal velocities are obtained. It is also demonstrated that the time difference between two consecutive relative maxima and minima of the displacement can both increase and decrease with time. | Study of oscillators with a non-negative real-power restoring force and quadratic damping | 10.1007/s11071-010-9861-9 |
2011-05-01 | It is known that the reduction in the finite element space discretization error for elastodynamics problems is related to the reduction in numerical dispersion of finite elements. In the paper, we extend the modified integration rule technique for the mass and stiffness matrices to the dispersion reduction of linear finite elements for linear elastodynamics. The analytical study of numerical dispersion for the modified integration rule technique and for the averaged mass matrix technique is carried out in the 1-D, 2-D and 3-D cases for harmonic plane waves. In the general case of loading, the numerical study of the effectiveness of the dispersion reduction techniques includes the filtering technique (developed in our previous papers) that identifies and removes spurious high-frequency oscillations. 1-D, 2-D and 3-D impact problems for which all frequencies of the semi-discrete system are excited are solved with the standard approach and with the new dispersion reduction technique. Numerical results show that compared with the standard mass and stiffness matrices, the simple dispersion reduction techniques lead to a considerable decrease in the number of degrees of freedom and computation time at the same accuracy, especially for multi-dimensional problems. A simple quantitative estimation of the effectiveness of the finite element formulations with reduced numerical dispersion compared with the formulation based on the standard mass and stiffness matrices is suggested. | Accurate finite element modeling of linear elastodynamics problems with the reduced dispersion error | 10.1007/s00466-010-0564-3 |
2011-05-01 | Here, we review the angular vestibulocollic reflex (VCR) focusing on its function during unexpected and voluntary head movements. Theoretically, the VCR could (1) stabilize the head in space during body movements and/or (2) dampen head oscillations that could occur as a result of the head’s underdamped mechanics. The reflex appears unaffected when the simplest, trisynaptic VCR pathways are severed. The VCR’s efficacy varies across species; in humans and monkeys, head stabilization is ineffective during low-frequency body movements in the yaw plan. While the appearance of head oscillations after the attenuation of semicircular canal function suggests a role in damping, this interpretation is complicated by defects in the vestibular input to other descending motor pathways such as gaze premotor circuits. Since the VCR should oppose head movements, it has been proposed that the reflex is suppressed during voluntary head motion. Consistent with this idea, vestibular-only (VO) neurons, which are possible vestibulocollic neurons, respond vigorously to passive, but not active, head rotations. Although VO neurons project to the spinal cord, their contribution to the VCR remains to be established. VCR cancelation during active head movements could be accomplished by an efference copy signal negating afferent activity related to active motion. Oscillations occurring during active motion could be eliminated by some combination of reflex actions and voluntary motor commands that take into account the head’s biomechanics. A direct demonstration of the status of the VCR during active head movements is required to clarify the function of the reflex. | Vestibular control of the head: possible functions of the vestibulocollic reflex | 10.1007/s00221-011-2611-5 |
2011-05-01 | Using a flexible support is an efficient approach to solving the subsynchronous problems in a turbopump. In this paper, nonlinear rotordynamic analysis of a liquid fuel turbopump with a flexible support is presented using a dynamic modeling including two key destabilizing factors, nonlinear hydrodynamic forces induced by seals and internal rotor damping. The methodology of the partitioned direct integration method (PDIM) is described for reducing the computational efforts efficiently. Combining the PDIM and the shooting method, a nonlinear stability analysis of the rotor system is performed effectively. The numerical results, which are in good agreement with test data, indicate that the effects of flexible support stiffness k on the dynamic characteristics and stability of the rotor system are significant. The first critical speed of the rotor system rises as a nonlinear function of k markedly. The second critical speed varies slightly and approximates a linear variation as k increases. The onset speed of instability of the rotor system rises initially and then reduces as k increases. The effect of seal nonlinearities at low k is contrary to that at high k and the effect of seal length on the system stability is more significant than that of seal radius. The results explain the nature of the subsynchronous motion of a turbopump rotor system with flexible support and can be used in the design and operation of a liquid fuel turbopump rotor system to eliminate its rotordynamic problem. | Effects of flexible support stiffness on the nonlinear dynamic characteristics and stability of a turbopump rotor system | 10.1007/s11071-010-9858-4 |
2011-05-01 | Kagome based high authority shape morphing structure is a kind of truss-cored sandwich metal plate with a planar Kagome truss as one of its face plane. The planar Kagome truss can achieve arbitrary in-plane nodal displacements with minimal internal resistance when its rods are deformed. Moreover, the in-plane deflection of the planar Kagome truss may induce the lateral deflection of the whole sandwich plate. In this paper, the feasibility to enhance the damping of the truss-cored sandwich plate through the replacement of a very small portion of rods in the planar Kagome truss by cylindrical viscoelastic dampers is exploited. The Biot model is chosen to simulate the behavior of the viscoelastic material in the dampers, and the fraction of axial modal strain energy of the rods in the planar Kagome truss is adopted as the index to decide the positions of the dampers. Through complex modal analysis and time-domain simulation, it is shown that the passive vibration control approach is very effective for the vibration reduction of this kind of truss-cored sandwich plates. | Passive vibration control of truss-cored sandwich plate with planar Kagome truss as one face plane | 10.1007/s11431-011-4354-8 |
2011-04-01 | Soluble vapor-gas bubbles performing small radial oscillations in a liquid are considered. The heat- and mass-transfer processes and temperature and concentration inhomogeneities in the vaporgas mixture are taken into account. Expressions for the damping rate of radial oscillations of soluble vapor-gas bubbles are obtained. In [1–3] the dynamics of vapor-gas bubble oscillations were considered for a gas insoluble in liquid. | Radial oscillations of soluble vapor-gas bubbles in a liquid | 10.1134/S0015462811020116 |
2011-04-01 | In the context of virtual development processes of mechatronic systems like machine tools, the preventive assessment of the effects of lightweight structural components on the characteristics of controlled feed systems and therefore on the power and energy requirement of machine tools is of great importance. The modeling of the damping is often limited in practical computation of real machine tools, because they are mostly limited to proportional damping characteristics. Yet the presence of discrete dampers, as for instance, in damping units in guides, or known diverse material damping in construction (components made of glass or carbon fiber-reinforced plastic), demands that the possibility of observance of non-proportional damping, in regard to later model updating, has to be given. The article demonstrates the theoretical state-space modeling of non-proportional damped mechanics using the example of a biaxial vertical lathe. | State space modeling of non-proportional passive damping in machine tools | 10.1007/s00170-010-2902-1 |
2011-04-01 | Full waveform inversion (FWI) directly minimizes errors between synthetic and observed data. For the surface acquisition geometry, reflections generated from deep reflectors are sensitive to overburden structure, so it is reasonable to update the macro velocity model in a top-to-bottom manner. For models dominated by horizontally layered structures, combination of offset/time weighting and constant update depth control (CUDC) is sufficient for layer-stripping FWI. CUDC requires ray tracing to determine reflection traveltimes at a constant depth. As model complexity increases, the multi-path effects will have to be considered. We developed a new layer-stripping FWI method utilizing damped seismic reflection data, which does not need CUDC and ray tracing. Numerical examples show that effective update depth (EUD) can be controlled by damping constants even in complex regions and the inversion result is more accurate than conventional methods. | Layer-stripping full waveform inversion with damped seismic reflection data | 10.1007/s12583-011-0177-6 |
2011-04-01 | Spacecrafts free of all but gravitational forces are important in precision navigation, gravity field measurement and basic scientific research. The Inner-formation Flying System, one kind of spacecrafts free of all but gravitational forces, is used for gravitational field measurement with high precision. Restraining the interfering factors on the inner-satellite is one of the keys to gravitational field measurement. Radiometer effect and residual gas damping are both interfering forces on the inner-satellite caused by gas molecules. By analyzing the mechanism of the two forces, a coupled model for radiometer effect and residual gas damping was established, which contained the coupling term and reflected the actual force of gas molecules on the innersatellite. The simulation results showed the coupling property of radiometer effect and residual gas damping: The actual force of gas molecules is directly proportional to the average pressure in the cavity and the largest cross-sectional area of the inner-satellite, but is inversely proportional to the square root of the average temperature in the cavity. | Coupled modeling and analysis of radiometer effect and residual gas damping on proof mass in purely gravitational orbit | 10.1007/s11431-011-4291-6 |
2011-04-01 | Free vibration characteristics of circular cylindrical shell with passive constrained layer damping (PCLD) are presented. Wave propagation approach rather than finite element method, transfer matrix method, and Rayleigh-Ritz method is used to solve the problem of vibration of PCLD circular cylindrical shell under a simply supported boundary condition at two ends. The governing equations of motion for the orthotropic cylindrical shell with PCLD are derived on the base of Sanders’ thin shell theory. Numerical results show that the present method is more effective in comparison with other methods. The effects of the thickness of viscoelastic core and constrained layer, the elastic modulus ratio of orthotropic constrained layer, the complex shear modulus of viscoelastic core on frequency parameter, and the loss factor are discussed. | Free vibration of circular cylindrical shell with constrained layer damping | 10.1007/s10483-011-1433-7 |
2011-04-01 | We consider three dimensional finite element computations of thermoelastic damping ratios of arbitrary bodies using Zener’s approach. In our small-damping formulation, unlike existing fully coupled formulations, the calculation is split into three smaller parts. Of these, the first sub-calculation involves routine undamped modal analysis using ANSYS. The second sub-calculation takes the mode shape, and solves on the same mesh a periodic heat conduction problem. Finally, the damping coefficient is a volume integral, evaluated elementwise. In the only other decoupled three dimensional computation of thermoelastic damping reported in the literature, the heat conduction problem is solved much less efficiently, using a modal expansion. We provide numerical examples using some beam-like geometries, for which Zener’s and similar formulas are valid. Among these we examine tapered beams, including the limiting case of a sharp tip. The latter’s higher-mode damping ratios dramatically exceed those of a comparable uniform beam. | Decoupled three-dimensional finite element computation of thermoelastic damping using Zener’s approximation | 10.1007/s11012-010-9318-8 |
2011-04-01 | In this study, we theoretically investigate the dynamic indentation for measuring the loss (damping) factor of a linear viscoelastic material from its indentation response. A rigid indenter with arbitrary tip profile is assumed to indent into a viscoelastic substrate with arbitrary shape. We perform a theoretical analysis and identify the conditions under which the loss factor of the material can be determined from the phase angle between the applied harmonic indentation load and the corresponding harmonic displacement, a directly measurable quantity in a dynamic indentation test. To validate the conclusion drawn from our theoretical analysis, a series of numerical experiments are performed, including the spherical indentation of a soft layer with irregular surface morphology bonded to a rigid substrate, a conical indenter with tip defects indenting into a half-spherical particle, and the indentation of porous materials. This study may facilitate the use of the dynamic indentation technique to evaluate the damping properties of linear viscoelastic materials, including some advanced polymers and biological soft tissues. | On determination of the damping factor of linear viscoelastic materials using dynamic indentation: a theoretical study | 10.1007/s11433-011-4279-z |
2011-04-01 | A neuron proportion integration (PI) control strategy for semi-active suspension system of tracked vehicle was proposed based on its unique structure and the multiple and complex environment of the driving traffic. An adaptive genetic algorithm is used to optimize the parameters of the neuron PI controller. The simulation result of the neuron PI control for semi-active suspension system of tracked vehicle indicates that the vertical amplitude, pitch angle and vertical acceleration of the vehicle are well controlled. The root mean square (RMS) of the vertical amplitude decreases by 37.2%, and 45.2% for the pitch angle, 38.6% for the vertical acceleration. The research of neuron PI control experiment for the semi-active suspension system of the tracked vehicle model mining in benthal indicates that the RMS of the weight acceleration vibrating along the vertical direction decreases by 29.5%, the power spectral density resonance peak of the acceleration of the car body decreases by 23.8%. | Neuron PI control for semi-active suspension system of tracked vehicle | 10.1007/s11771-011-0716-4 |
2011-04-01 | This paper presents a design theory and dynamic mechanical characterizations of the composite tape-spring hinge made by two parallel single tape springs. First, the theoretical models of moment-rotation angle on anisotropy tape springs with antisymmetric laminates are proposed. Second, the relationships of moment-rotation angle for tape-spring hinges with different sizes are simulated and analyzed by means of the finite element method (FEM), which is in good agreement with the results from theoretical predictions. Finally, the dynamic vibration analysis for deployable composite tube hinges with different dampings is done during the process of deployment. | Design theory and dynamic mechanical characterization of the deployable composite tube hinge | 10.1007/s11433-011-4286-0 |
2011-04-01 | The general algorithm of calculations for oscillating-cup viscometry of fluids with viscous, elastic and plastic components is developed for damped and forced modes. The working equations efficient for practical applications are presented and related problems of data processing are analyzed. The case of forced oscillations of viscometer filled with rheostable fluids is treated in detail. | Nonlinear oscillating-cup viscometry | 10.1007/s00397-010-0517-y |
2011-03-01 | Damping of the loose spring skirt (LSS) of a vibrating pipe under operating conditions was studied experimentally and numerically. Motion images made using a high speed charge-coupled device (CCD) camera as well as acceleration signals were analyzed in order to correlate the physical states of the LSS pipe system with the vibration transmissibility (TM) through the pipe. Experiments on the pipe undergoing harmonic excitation demonstrate that the damping of the LSS is caused by the same mechanism as with a conventional impact damper. Measurements of the acceleration TM as a function of excitation amplitude verified that the momentum exchange between the pipe and the auxiliary spring is the cause of the damping produced by the LSS pipe. Another finding of this research is that the experimental representation of the resonance shift phenomenon is related to two main operating conditions, namely: 1) the driving frequency and 2) the excitation amplitude. This research demonstrated the occurrence of the resonance shift phenomenon through experimental mapping of the system response at increasing excitation amplitudes using frequency sweep tests. Simulations of the LSS pipe system based on principal coordinate and impact damping analysis were performed in order to investigate and provide better explanations for LSS pipe system damping mechanisms. As a result of this research study, a new damping mechanism is proposed which is different from previous damping models. This research study has also addressed more practical boundary and excitation conditions for LSS pipe systems. | Study of the Damping Mechanisms of Loose Spring Skirts on Vibrating Pipes | 10.1007/s11340-010-9361-3 |
2011-03-01 | A general and comprehensive analysis on the continuous contact force models for soft materials in multibody dynamics is presented throughout this work. The force models are developed based on the foundation of the Hertz law together with a hysteresis damping parameter that accounts for the energy dissipation during the contact process. In a simple way, these contact force models are based on the analysis and development of three main issues: (i) the dissipated energy associated with the coefficient of restitution that includes the balance of kinetic energy and the conservation of the linear momentum between the initial and final instant of contact; (ii) the stored elastic energy, representing part of initial kinetic energy, which is evaluated as the work done by the contact force developed during the contact process; (iii) the dissipated energy due to internal damping, which is evaluated by modeling the contact process as a single degree-of- freedom system to obtain a hysteresis damping factor. This factor takes into account the geometrical and material properties, as well as the kinematic characteristics of the contacting bodies. This approach has the great merit that can be used for contact problems involving materials with low or moderate values of coefficient of restitution and, therefore, accommodate high amount of energy dissipation. In addition, the resulting contact force model is suitable to be included into the equations of motion of a multibody system and contributes to their stable numerical resolution. A demonstrative example of application is used to provide the results that support the analysis and discussion of procedures and methodologies described in this work. | On the continuous contact force models for soft materials in multibody dynamics | 10.1007/s11044-010-9237-4 |
2011-03-01 | In this paper, a decrease of turbulent pulsations of velocity in a boundary layer and the coefficient of friction drag for an accelerating flow on the perforated surface with blind damping cavities is experimentally found. We generalize the mathematical model of partial boundary layer laminarization [1], which is based on the experimental data [2, 3] obtained earlier on a decrease of the friction drag coefficient and deformation of average velocity profiles in the stabilized section of flow in the perforated tube with blind damping cavities. | Laminarization of a boundary layer on the perforated surface with blind damping cavities in an accelerating flow | 10.3103/S1068799811010107 |
2011-03-01 | The huge piles of overburden comprising of fragmented rocks and loose soil are dumped within the leasehold area causing serious environmental problems in view of occasional sliding and the risks of miner’s life. The continuum-based numerical approach ignores the discrete nature of the geo-materials found in external overburden dump, in terms of both composition and interactions. Engineering mechanics in the discontinuum regime has been utilized to overcome the mentioned limitations. The distinct element method is employed to characterize the overburden dump geometry and the associated physical behaviour of the dump mass for seismic loads. The study discussed about the earthquake vibration responses and assessed the internal dynamics of the dump mass system. | Earthquake response of external mine overburden dumps: a micromechanical approach | 10.1007/s11069-010-9602-x |
2011-03-01 | This paper addresses the analysis of active constrained layer damping (ACLD) of geometrically nonlinear transient vibrations of laminated thin composite cylindrical shallow shells using vertically reinforced 1-3 piezoelectric composite (PZC). The constraining layer of the ACLD treatment is considered to be made of this 1-3 PZC material. The Golla–Hughes–McTavish (GHM) method has been implemented to model the constrained viscoelastic layer of the ACLD treatment in time domain. The Von Kármán type non-linear strain displacement relations and the first-order shear deformation theory (FSDT) are used for deriving this electromechanical coupled problem. A three dimensional finite element (FE) model of smart composite shallow shells integrated with a patch of such ACLD treatment has been developed to demonstrate the performance of the patch on enhancing the damping characteristics of thin laminated cylindrical shells, in controlling the geometrically nonlinear transient vibrations. The numerical results indicate that the ACLD patch significantly improves the damping characteristics of the shells for suppressing the geometrically nonlinear transient vibrations of the shells. The effect of variation of fiber orientation in the PZC material on the control authority of the ACLD patch has also been investigated. | Active damping of geometrically nonlinear vibrations of laminated composite shallow shells using vertically/obliquely reinforced 1-3 piezoelectric composites | 10.1007/s10999-010-9147-x |
2011-03-01 | The coupled problem of the forced axisymmetric vibrations and self-heating of electrothermoviscoelastic cylindrical shells with piezoceramic actuators under monoharmonic electromechanical loading is solved. The temperature dependence of the complex characteristics of the passive and piezoactive materials is taken into account. The coupled nonlinear problem of electrothermoelasticity is solved by using a time-marching method with discrete orthogonalization at each time step (to integrate the equations of elasticity) and an explicit finite-difference method (to solve the heat-conduction equations). An analysis is made of the effect of the boundary conditions at the shell ends, the dimensions of the piezoactuator, and the self-heating temperature on the actuator voltage and the effectiveness of active damping of the forced vibrations of the shell under uniform transverse monoharmonic pressure | Forced axisymmetric vibrations and self-heating of thermoviscoelastic cylindrical shells with piezoelectric actuators | 10.1007/s10778-011-0405-x |
2011-03-01 | Eucommia ulmoides gum (EU gum), known as gutta percha in Southeast Asia, is a natural polymer with double characteristics of rubber and plastic. In present paper, tan δ - T curve and hysteresis loss (HL) were chosen to characterize its damping property. The results indicated that its tan δ value would increase with rising of temperature when T > 0°C and form another damping peak at 40–80°C besides T _g peak. This phenomenon resulted from meltage of crystals of EU gum could increase its damping property at ambient-high temperature. Its tan δ value even exceeded those of conventional damping rubbers, such as nitrile-butadiene rubber (NBR) and chlorinated isobutene-isoprene rubber (CIIR). | Damping performance of Eucommia ulmoides gum | 10.1007/s10118-010-1008-4 |
2011-02-01 | This paper describes the non-linear identification of a progressively damaged reinforced concrete beam-column node. The aims are the detection and identification of the different sources of damping and their dependence from the damage level. To this end a specially formulated non-linear identification method is proposed, based on a time-varying polynomial approximation of the system dynamics, suitable for use in the presence of excitations of any form. A minimum condition imposed to the identified dissipated energy leads to the distinction of the linear viscous component from the other damping mechanisms. The estimated values obtained from the experimental tests show a significant influence of the damage level on the linear viscous damping coefficient. This suggests that, in a non-linear dynamic time-history analysis, the use of Rayleigh damping model with proportionality to the initial stiffness is basically in contrast with experimental evidence and more refined viscous damping models are needed for prediction purposes. | Non-linear Damping and Frequency Identification in a Progressively Damaged R.C. Element | 10.1007/s11340-010-9360-4 |
2011-02-01 | Globally positive solutions for the third order differential equation with the damping term and delay, $$ x''' + q(t)x'(t) - r(t)f(x(\phi (t))) = 0, $$ are studied in the case where the corresponding second order differential equation $$ y'' + q(t)y = 0 $$ is oscillatory. Necessary and sufficient conditions for all nonoscillatory solutions of (*) to be unbounded are given. Furthermore, oscillation criteria ensuring that any solution is either oscillatory or unbounded together with its first and second derivatives are presented. The comparison of results with those in the case when (**) is nonoscillatory is given, as well. | Unbounded solutions of third order delayed differential equations with damping term | 10.2478/s11533-010-0088-2 |
2011-02-01 | A nonlinear mathematical model of a system of n rigid bodies undergoing translational vibrations under inertial loading is constructed. The system includes ball supports as a seismic-isolation mechanism and electromagnetic dampers controlled via an inertial feedback channel. A system of differential dynamic equations in normal form describing accelerative damping is derived. The frequencies of small undamped vibrations are calculated. A method for analyzing the dynamic coefficients of rigid bodies subject to accelerative damping is developed. The double phase–frequency resonance of a two-mass system is studied | Nonlinear dynamics of a system of rigid bodies with controlled electromagnetic dampers | 10.1007/s10778-011-0399-4 |
2011-02-01 | We consider two mathematical models that describe the vibrations of spring-mass-damper systems with contact and friction. In the first model, both the contact and frictional boundary conditions are described with subdifferentials of nonconvex functions. In the second model, the contact is modeled with a Lipschitz continuous function, and the restitution force is described by a differential equation involving a Volterra integral term. The two models lead to second-order differential inclusions with and without an integral term, in which the unknowns are the positions of the masses. For each model, we prove the existence of a solution by using an abstract result for first-order differential inclusions in finite dimensional spaces. For the second model, in addition, we prove the uniqueness of the solution by using a fixed point argument. Finally, we provide examples of systems with contact and friction conditions for which our results are valid. | Analysis of lumped models with contact and friction | 10.1007/s00033-010-0081-4 |
2011-02-01 | Friction-induced vibration is an important phenomenon with adverse effects on many dynamic systems involving friction. In this study, a very simple and well-known one-dimensional friction-induced dynamic system is considered in which the novel PZT stack impulse damper is incorporated into the system. It has been shown that by appropriately tuning the damping parameters, the chaotic behavior is removed quickly and efficiently. It has also been demonstrated that the system is sensitive to parameter change, and minimal modification of these parameters can revert the chaotic or periodic motion. | Application of impulse damper in control of a chaotic friction-induced vibration | 10.1007/s12206-010-1116-7 |
2011-01-01 | This work is concerned with ( n -component) hyperbolic systems of balance laws in m space dimensions. First, we consider linear systems with constant coefficients and analyze the possible behavior of solutions as t → ∞. Using the Fourier transform, we examine the role that control theoretical tools, such as the classical Kalman rank condition, play. We build Lyapunov functionals allowing us to establish explicit decay rates depending on the frequency variable. In this way we extend the previous analysis by Shizuta and Kawashima under the so-called algebraic condition (SK). In particular, we show the existence of systems exhibiting more complex behavior than the one that the (SK) condition allows. We also discuss links between this analysis and previous literature in the context of damped wave equations, hypoellipticity and hypocoercivity. To conclude, we analyze the existence of global solutions around constant equilibria for nonlinear systems of balance laws. Our analysis of the linear case allows proving existence results in situations that the previously existing theory does not cover. | Large Time Asymptotics for Partially Dissipative Hyperbolic Systems | 10.1007/s00205-010-0321-y |
2011-01-01 | In this chapter we return to our study of non-adiabatic effects on the forces in collision cascades. In this case we examine the behaviour of the non-adiabatic force on the moving ions. Various attempts have been made to capture the effects of such forces in classical MD simulations by adding a drag force to the ionic dynamics. Our time-dependent tight-binding simulations give us direct access to information about these forces and so we use a set of cascade simulations to assess the validity of simple drag models. By considering the origin of the non-adiabatic force within a tight-binding picture we are able to propose a new classical model for the non-adiabatic force; one which can be easily incorporated within a classical MD scheme at near zero computational cost. We evaluate the performance of our model using simulation data and find that it is a significant improvement over simple damping models. In particular, it is able to replicate the non-adiabatic energy loss from ions at the individual ion level and over times that are short on the time-scale of individual collision events, and able to capture the variation of the individual cartesian components of the non-adiabatic force. This should be contrasted with the simple damping models, which can only replicate the average energy loss at the level of a whole cascade and over much longer time-scales, and which are explicitly constrained to apply forces in opposition to the ionic velocities. | The Electronic Drag Force | 10.1007/978-3-642-15439-3_11 |
2011-01-01 | This chapter presents an assortment of material, covered in varying degrees of detail, which is needed as background material for the rest of this book. Students with a strong background in mathematics can probably skim some of the sections in this chapter. Section 1.1 discusses why differential equations are important to study in engineering. Section 1.2 discusses functions in mathematics, which is important not only because functions are solutions to differential equations but also because it helps define the types of variables that appear in differential equations. Implicit functions are also reviewed. The most important sections in this chapter are Sections 1.3 and 1.4 because they present new material that is used throughout the entire book related to the types of differential equations and their solutions. Section 1.5 reviews concepts from mechanical and electronic systems, including the properties of the common elements that make up simple electromechanical engineering systems. Finally, Section 1.6 presents the most basic method to use a computer to determine an approximate solution to an initial value problem for a given ordinary differential equation. More advanced numerical methods are considered in Chapter 12, but this introductory material is presented so that, even in the earliest chapters, students can check their work using a computer-solving method. | Introduction and Preliminaries | 10.1007/978-1-4419-7919-3_1 |
2011-01-01 | The paper deals with influence of dry friction damping on bladed disk vibration. Firstly the 3D FE solution and analysis of the imperfect blade disk dynamics is presented. Then the dry friction effect is studied analytically on linearized spring-dry-friction model consisting of equivalent linear stiffness and damping coefficients. An influence of nonlinearities and unproportional damping distribution on response curves is discussed as well. | Influence of Dry Friction Damping on Bladed Disk Vibration | 10.1007/978-94-007-2069-5_75 |
2011-01-01 | Many forms of actuators have been developed with the capability of braking. Most of these braking mechanisms involve numerous mechanical components, that wear with time and lose precision, furthermore the mechanism are difficult to scale down in size while maintaining relatively large holding torques. In this paper, we propose the use of an off-the-shelf economic material, Hot-Melt-Adhesive (HMA), as a brake mechanism. HMA exhibits visco-elastic characteristics and has interesting properties as it can change phases from solid to plastic to liquid and vice versa. Its advantage is that it is reusable and durable. Experiments were performed to display the holding strength as well as the HMAs visco-elasticity in its solid state as a brake mechanism. The HMA requires no constant application of power when solid, and acts as a brake and visco-elastic damper depending on temperature. Results show that HMA can add compliance and high torque braking of joints. | Design and Control of a Novel Visco-elastic Braking Mechanism Using HMA | 10.1007/978-3-642-25486-4_42 |
2011-01-01 | This chapter is devoted to studying the problems associated with second-order differential equations with an unbounded operator coefficient A in a Banach space. In Section 4.1, we consider these equations with an unbounded operator in either Banach or Hilbert spaces depending on the parameter t. We propose a discretization method with a high parallelism level and without accuracy saturation, i.e., the accuracy adapts automatically to the smoothness of the solution. For analytical solutions, the rate of convergence is exponential. These results can be viewed as a development of parallel approximations of the operator cosine function cos(At) which represents the solution operator of the initial value problem for the secondorder differential equation with a constant operator A coefficient. | The second-order equations | 10.1007/978-3-0348-0119-5_4 |
2011-01-01 | Due to the gyro random walk and other reasons, Schuler oscillation amplitude of undamped inertial navigation system will increase with time. The marine inertial navigation systems were often required to work continuously for hours to days or even longer, over divergent INS position error will cause loss of navigation function. Thus, the appropriate algorithm in the system must be added to damp the Schuler oscillations. The damping networks for INS level channels are designed. For the applications of marine INS, a new internal damping method which uses its own measurements as reference velocity rather than external inputs is presented. Marine test results show that the proposed internal damping method can suppress the Inertial Navigation System Schuler oscillation error and make it no longer divergent, thereby improving the navigation accuracy of INS in long-endurance applications, and has practical values in engineering. | Research on Internal Damping Algorithm of Marine Inertial Navigation System | 10.1007/978-3-642-18134-4_41 |
2011-01-01 | The article deals with measurement and evaluation of damping properties of polyurethane (PU) foam. This problem is considered from the point of view of vibroinsulation and dynamical comfort of person sitting in a moving car. The force response to dynamical compression of PU foam specimen by harmonical course of displacement is evaluated. Frequency of exciting signal and specimen temperature is varied in predefined range. Course of damping force is simulated by explicitly defined function and also its prediction is exemplified. | Modelling of Damping Force of Polyurethane Foam in Dependence on Its Temperature | 10.1007/978-94-007-2069-5_89 |
2011-01-01 | We define horizontal diffusion in C ^1 path space over a Riemannian manifold and prove its existence. If the metric on the manifold is developing under the forward Ricci flow, horizontal diffusion along Brownian motion turns out to be length preserving. As application, we prove contraction properties in the Monge–Kantorovich minimization problem for probability measures evolving along the heat flow. For constant rank diffusions, differentiating a family of coupled diffusions gives a derivative process with a covariant derivative of finite variation. This construction provides an alternative method to filtering out redundant noise. | Horizontal Diffusion in C
^1 Path Space | 10.1007/978-3-642-15217-7_2 |
2011-01-01 | A new semiactive coupling element working on the principle ofsqueezing two concentric films formed by classical and magnetorheological liquids has been proposed to achieve the optimum attenuation of the lateral vibration of rotors. The damping effect is controlled by changing the magnetic field induction. The steady state solution of the equations of motion is obtained by application of a collocation method and its stability is evaluated using the Floquet theory. The newly proposed controllable damping device enables to minimize amplitude of the rotor vibration by adapting the damping effect to the current operating conditions. | Stability Investigation of the Steady State Response of Flexibly Supported Rigid Rotors | 10.1007/978-94-007-2069-5_70 |
2011-01-01 | Uniform stability of Reissner-Mindlin-Timoshenko (RMT) plates is addressed. Similarly to waves, Kirchhoff plates, and elastodynamics, boundary stabilization of the RMT model relies on an observability inequality, which in turn necessitates the derivation of certain trace regularity estimates. The exponential stability of RMT plates has been quoted for many years, yet, to the best of our knowledge, a detailed analysis of a requisite trace regularity result does not appear to exist in the literature. The purpose of this note is to provide such details. | On Stability and Trace Regularity of Solutions to Reissner-Mindlin-Timoshenko Equations | 10.1007/978-3-0348-0069-3_5 |
2011-01-01 | Excessive vibration of machines and/or structures can be controlled passively (e.g. introducing resilient elements) and/or actively (e.g. using elements capable to adjust their properties for actual state of the vibration). An electromagnet, as a vibration control element, can be implemented in active (or semi-active) control strategy. This approach is analyzed in the present paper. The electromagnetic induction occurs in a magnetic circuit exposed to variable magnetic flux, which can be obtained e.g. by changing reluctance (magnetic resistance) of the system due to a variable air gap, as the result of armature vibration. The lumped parameter mathematical model of the coupled electro-magneto-mechanical system is formulated. The performance of the model is analyzed, assuming harmonic forced vibration. By the induction, mechanical energy of vibration is converted into electrical one and dissipated in the shunt resistance. Two concepts are investigated further – electromagnet behaves as (a) a spring element (reduction of equivalent system stiffness); (b) a damping element. | An Application of Electromagnetic Induction in Vibration Control | 10.1007/978-94-007-2069-5_61 |
2011-01-01 | This study investigates the effect of damping in an input device on performance in a target acquisition task. In an experiment with 21 participants, five levels of damping were tested in the range of 0 to 10 Ns/m. Contrary to our expectation, the time required to acquire a target decreased as the damping value increased. The reduction in completion time was not caused by an increase in velocity, but by a decrease in the overshoot rate. It is therefore concluded that, unlike previous beliefs, some amount of damping in an input device can be beneficial to user performance. | The Effect of Damping in an Input Device on Human Positioning Performance | 10.1007/978-3-642-22095-1_67 |
2011-01-01 | We have found an analytical expression describing the evolution of a two-level system in a strong resonant quantum field beyond the rotating wave approximation. The solution obtained has allowed us for the first time to identify the qualitative features of the behavior of the system in this case: suppression of the "collapse–revival" effect, and a change in the spectrum and shape of Rabi oscillations for an inverted population. The results are of interest for applied spectroscopy, quantum optics, and nanomechanics. | Transformation of a Rabi oscillation spectrum for a two-level system in a strong resonant field | 10.1007/s10812-011-9410-4 |
2011-01-01 | The topic of how a solution to a problem in continuum mechanics decays in space, including those equations which involve second sound, has been one of immense interest over the last few years. The first articles to deal with spatial decay in thermoelasticity would appear to be those of (Chirita, 1995a; Chirita, 1995b), (Chirita, 1997) and (Horgan and Payne, 1997). It would appear that the first articles dealing with spatial decay in second sound theories were those of (Quintanilla, 1996), who derived estimates for a solution to a damped wave equation, (Payne and Song, 1996), who established spatial decay bounds for a generalized Maxwell-Cattaneo theory (Guyer-Krumhansl model), and (Chirita and Quintanilla, 1996), who obtained spatial decay for a suitable functional measure of a solution to the Green-Lindsay equations of thermoelasticity. | Spatial decay | 10.1007/978-1-4614-0493-4_7 |
2011-01-01 | The dynamic mechanical properties of compacted samples of synthetic calcium silicate hydrate (C–S–H) were determined at variable stoichiometries (C/S ratio). The stiffness and damping properties of the C–S–H systems were monitored at various increments of mass loss from 11%RH following the removal of the adsorbed and interlayer water. The changes in the storage modulus ( E ′) and internal friction (tan δ ) were discussed in terms of the state of water present in the nanostructure of C–S–H, the evolution of the silicate structure and the interaction of calcium ions in the interlayer region. Results were compared to those for the hydrated Portland cement paste and porous glass. It was shown that the C–S–H in the hydrated Portland cement has a complex yet analogous dynamic mechanical behavior to that of the synthetic C–S–H. The response of these systems upon the removal of water was explained by a layered model for the C–S–H. A mechanistic model was proposed to describe the changes occurring at various stages in the dynamic mechanical response of C–S–H. | Mechanical properties of calcium silicate hydrates | 10.1617/s11527-010-9605-9 |
2024-03-01 | With low liquidus temperatures, low raw material costs, and non-toxicity, Sn-Bi low-temperature solders are promising candidates for the replacement of the currently widely-used lead-free solders in situations in which process temperatures have to be reduced. Electrical resistivity is one of the most important properties of solder alloys, as one of their primary functions is to conduct electrons between the connected components. The electrical resistivity of an alloy of a given composition at a specific temperature and pressure is affected by the microstructure and the crystal structure of the phases present. For Sn-Bi solders, the solubility of Bi in Sn is highly temperature-sensitive and increases from 3 wt.% at room temperature to 21 wt.% at 139°C, the eutectic temperature of the Sn-Bi system. As the temperature increases within that interval, Bi will dissolve in Sn, while it will precipitate as the temperature decreases. The resulting significant changes in the overall microstructure and the lattice parameters of the Sn phase can be expected to affect the electrical resistivity. In this study, the electrical resistivity of hypo-eutectic Sn-37wt.%Bi and near-eutectic Sn-57wt.%Bi alloys was measured as a function of temperature and the temperature coefficient of resistance (TCR) calculated. It was found that the electrical resistivity increases linearly with increasing temperature up to 70°C, while above 80°C, a deviation from the linear relationship was observed. This deviation is attributed to the rapid dissolution of Bi in Sn at 80°C and above. | The Effect of Temperature on the Electrical Resistivity of Sn-Bi Alloys | 10.1007/s11664-023-10849-1 |
2024-03-01 | Gasification is widely regarded as one of the most practical, economical, and environmentally friendly waste disposal technologies for municipal solid waste (MSW). The pyrolysis stage (300–500 °C) is crucial for weight loss during MSW gasification, as a considerable amount of organic matter breaks down, producing high-value synthesis gas. This study investigated the product distribution and pollutant emission characteristics within this temperature range and its influencing factors during MSW gasification using a self-designed MSW gasification device. Results indicated that MSW underwent approximately 70% weight loss within this temperature range, yielding low amounts of inorganic and short-chain organic products, with mainly long-chain organic compounds of C 16 –C 34 . The atmosphere variation had minimal effect on the elemental composition and content of solid phase products. X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS) analyses showed that Mn and Zn were the primary components of heavy metal leaching toxicity in solid phase products, with their contents increasing as temperature increased. Synthesis gas showed the highest content of heavy metal As element, reaching a peak at 400 °C. Higher gasification temperature and lower oxygen flow rate significantly reduced the dioxin content and I-TEQ values, with highly chlorinated isomers being the predominant dioxin isomers. Nonetheless, low-chlorinated dioxins accounted for more than 50% of the I-TEQ. This study improves our understanding of the gasification process of MSW. | Distribution of gasification products and emission of heavy metals and dioxins from municipal solid waste at the low temperature pyrolysis stage | 10.1007/s11356-024-32284-3 |
2024-03-01 | The potential of Sn-Bi alloys as low-temperature solders for electronics manufacturing has spurred significant research on their mechanical properties, both in the as-soldered condition and after aging. Previous studies have demonstrated that, because of the extreme temperature sensitivity of the solubility of Bi in Sn, the mechanical properties of Sn-Bi solder alloys are very sensitive to their thermal history. While the properties of the bulk solder alloy are a factor in its performance as a solder joint, the reliability in service is also affected by the joint geometry and the interaction of the solder alloy with the joint substrate. In the work reported in this paper the effect of thermal history on solder joints formed with representative Sn-Bi alloy solder balls was assessed by measuring the performance in a standard ball shear test of a solder ball reflowed to solder mask defined (SMD) copper pads with organic solderability preservative (OSP) or electroless nickel/immersion gold (ENIG) finishes. The solder ball/substrate combinations were tested within 10 min of reflow and after room-temperature storage for up to 10 days to determine the effect of aging on their response to the ball shear test. Our results show that the peak force and fracture mode of Sn-Bi solder joints is influenced by the Sn-Bi alloy composition, the substrate type, and the aging time. These observations provide new information on the capability of these alloys to deliver reliable service over a range of operating conditions. | Investigating the Effects of Rapid Precipitation of Bi in Sn on the Shear Strength of BGA Sn-Bi Alloys | 10.1007/s11664-023-10850-8 |
2024-03-01 | The change in the electrical resistance of a SnBi-based solder joint during current stressing has been measured. For early times, a distinct, non-linear signal was observed and correlated with the initial formation of a continuous Bi layer via a lateral growth mechanism. For later times, a linear increase in the electrical resistance of the solder joints with respect to time was observed. The change in electrical resistance was found to be linearly proportional to the thickness of a continuous Bi layer accumulating at the anode during current stressing. Thus, a linear relationship between the change in electrical resistance and the thickness of the Bi layer was observed; the proportionality coefficient was found to be very large, consistent with a Bi morphology with micron-sized grains. Measurements of the mean times to failure for particular values of current density and temperature were characterized using Black’s equation. This formalism provides acceleration factors for laboratory current stressing of such low-temperature solder joints. | Changes in the Microstructure and Electrical Resistance of SnBi-Based Solder Joints during Current Stressing | 10.1007/s11664-023-10875-z |
2024-03-01 | Hot-swaging yields a high ultimate tensile strength of 712 MPa but a limited tensile ductility with the total elongation of 3.6% at a testing temperature of 200 °C in a representative W-0.5wt.%ZrC alloy. In this work, the evolution of Vickers micro-hardness with annealing temperatures is investigated in detail, which contributes to a rough index chart to guide the search for an optimized post-annealing temperature. Through the post-annealing around 1300 °C, an outstanding tensile ductility at 200 °C, including a uniform elongation of 14% and a total elongation of ~ 25%, has been achieved without the sacrifice of its strength. The evolution of dislocations and grain structures with the annealing temperatures accessed through backscattered scanning electron microscope and transmission electron microscope analysis reveals that the improved low-temperature tensile ductility has resulted from the reduction of residual dislocations and dislocation tanglement via the static recovery, which provides more room to accommodate dislocations, and hence stronger strain hardening ability and tensile ductility. | Achieving a remarkable low-temperature tensile ductility in a high-strength tungsten alloy | 10.1007/s42864-023-00218-0 |
2024-03-01 | Strengthening low-chromium iron-based alloys with multiple alloy elements is a crucial strategy for developing “casing-friendly” hardbanding materials. In this paper, four kinds of low-chromium iron-based hardfacing alloys with different Ti contents were prepared by flux-cored arc welding technology, and the effect of Ti content on the microstructure, hardness, and wear performance under the abrasive wear and dry sliding wear was analyzed. The in situ TiC-reinforced iron-based hardfacing alloys exhibited microstructure comprising austenite, martensite, carbides, and in situ TiC particles. The in situ formation of TiC particles consumed the carbon in the alloy and thus raised the martensite start temperature, resulting in a reduction in the mass fraction of austenite and an increase in the martensite. Among the four hardfacing alloys, the alloy with 5 wt.% Ti exhibited the highest hardness (836.3 HV 0.2 ) and the best wear resistance due to its highest martensite mass fraction (69.97 wt.%). The matrix with in situ TiC particles and martensite effectively resisted the cutting of abrasive grains and the wear mechanism developed from the microplowing in 0Ti alloy to microcutting in in situ TiC-reinforced iron-based hardfacing alloys in abrasive wear tests. In dry sliding wear tests, TiC particles were released and slid on the surface of the alloys, resulting in the formation of grooves, while the formation of the tribochemical reaction layers contributed to a reduction in the friction coefficient and wear rate. This study provides a theoretical foundation for the development of “casing-friendly” hardbanding materials. Graphical Abstract | Microstructure and wear resistance of in situ TiC-reinforced low-chromium iron-based hardfacing alloys | 10.1007/s40194-023-01657-6 |
2024-03-01 | In this study, a high temperature in-situ route is reported for the synthesis of one dimensional carbon nitride supported bismuth sulfide nanoparticles. The x-ray diffraction study confirmed the formation of orthorhombic crystal structure of bismuth sulfide with the space group of Pnma (62). The synthesized product was used as an electrode material for supercapacitor application. Electrochemical performance of the three-electrode configuration demonstrated the specific capacitance value of 190 F.g −1 at the current density 1.5 A.g −1 . A symmetric supercapacitor device, fabricated using identical synthesized material, resulted a specific capacity of 101.7 mAh.g −1 at 0.02 A.g −1 , with energy and power density values of 24.35 mWh.kg −1 and 186.57 W.kg −1 , respectively. The symmetric device also exhibited excellent cycling stability that retained 99% of its initial capacity after 500 cycles at 0.12 A.g −1 . The coin cell based symmetric supercapacitor can generate the low frequency waveform and functioned as an oscillator. Graphical Abstract | Carbon Nitride Supported Ultra-fine Bismuth Sulfide Based Supercapacitor for Low Frequency Oscillator Application | 10.1007/s11664-023-10901-0 |
2024-03-01 | Titanium aluminide (TiAl) has been identified as a key material for achieving significant emission reductions in aircraft jet engines due to its high-temperature properties combined with its very low weight compared with conventional nickel-based alloys. Well-known engine manufacturers, therefore, introduced TiAl low-pressure turbine blades in their engines. To enter the market, all manufacturers initially relied on enormous machining allowances for safety reasons, thus accepting a poor buy-to-fly ratio: MTU Aero Engines AG used the casting/forging route with the alloy TNM [Ti–43.5Al–4Nb–1Mo–0.1B (at.-%)] for the highly stressed GTF (geared turbofan), Safran used machining of the alloy GE48-2-2 (Ti–33Al–2.6Cr–4.8Nb (wt.-%)) from the solid, and GE (General Electric) used ‘massive-overstock’ investment casting and 3D printing of GE48-2-2. More cost-effective and material-efficient processes are needed for titanium aluminide to establish itself sustainably in new aerospace applications in the long term. Access has, therefore, developed an economical TiAl investment casting process to industrial maturity, realizing a minimum machining allowance of 0.7 mm in a process-safe manner. In a study, it was evaluated that carbide cutters with AlTiN coating are excellently suited for machining TiAl. Extensive studies of the economic viability of TiAl investment casting have shown that it is competitive. | Resource-Efficient Manufacturing Technology for Titanium Aluminide Aerospace Components | 10.1007/s41403-023-00436-5 |
2024-03-01 | API 5L Grade X65 steel pipes, internally clad alloy 625, are commonly utilized in pipelines and risers for subsea oil and gas extraction. Gird welds in such pipes are conventionally made using alloy 625 filler metal. However, alloy 625 weld metal cannot meet the base metal yield strength overmatching requirement for subsea reel lay installation. This study explored materials selection and process development for low-alloy steel girth welds in API 5L Grade X65 steel pipes, internally clad with alloy 625. Welding with a higher melting point filler metal over a lower melting substrate, i.e., low-alloy steel over Ni-based alloy, is impractical due to increased susceptibility to solidification cracking and solidification shrinkage porosity. Pseudo-binary phase diagrams developed for various combinations of low alloy steel filler metals and Ni-based alloy substrates identified good compatibility between ER80S-G filler metal and alloy 686. The solidification temperature range and the tendency for partitioning of alloying elements were significantly lower throughout the entire ER80S-G/alloy 686 dilution range than in the low alloy steel filler metals/alloy 625 combinations. Extensive process optimization effort to reduce the dilution of alloy 686 root pass in the low-alloy steel weld metal and avoid incomplete fusion defects allowed for the production of defect-free girth welds. These welds met the yield strength and ductility requirements for subsea reel lay installation of pipelines. Process optimization for bead tempering significantly narrowed the high hardness region in the ER80S-G/alloy 686 partially mixed zone. | Low alloy steel girth welds in X65 steel pipes internally clad with alloy 625 | 10.1007/s40194-023-01661-w |
2024-03-01 | De-oiled rice bran is a good source of high-quality protein; however, the current practice of desolventization at high temperature (110–120 °C) denatures the protein, making its extraction difficult and uneconomical. The present study aims to investigate the effect of low temperature desolventization of de-oiled rice bran (LTDRB) on extraction, yield, and purity of protein and its comparison with protein obtained from high temperature desolventized de-oiled rice bran (HTDRB). The optimal conditions for preparation of protein from LTDRB were: extraction pH 11.00, extraction duration 52 min, and extraction temperature 58 °C resulting in an extraction efficiency, yield, and purity of 54.0, 7.23, and 78.70%, respectively. The LTDRB showed a positive impact on the color, solubility, foaming capacity and stability of protein whereas the absorption and emulsification properties were better for HTDRB protein. Significant decrease in enthalpy (ΔH) for denaturation was observed for LTDRB protein as compared to HTDRB protein. Scanning electron microscopy analysis revealed that HTDRB protein was more compact than LTDRB protein. LTDRB protein had smaller particle size distribution than HTDRB. Study suggested that low temperature desolventization can result in higher protein extraction with better physico-chemical, structural, and functional properties of protein obtained from DRB. | Low temperature desolventization: effect on physico-chemical, functional and structural properties of rice bran protein | 10.1007/s13197-023-05859-0 |
2024-03-01 | Low-melting-point Sn-Bi solder joints (melting point: 139°C) show remarkable resistance to damage accumulation during aggressive thermal cycling. In this study, we used isothermal aging at 85°C of near eutectic Sn-Bi solder joints to determine the effect of Sb in solid solution and Ag 3 Sn intermetallic on microstructural evolution and the resulting mechanical properties as a way to explain the thermal cycling behavior. Most importantly, the Sb in solid solution in these alloys resulted in higher strength and improved creep resistance when compared to eutectic Sn-Bi. In contrast to Sn-Pb and Sn-Ag-Cu Pb-free alloys, all the near-eutectic Sn-Bi alloys tested showed significant age hardening. In both the unaged and aged conditions, both Sb and Ag additions individually increased the saturation stress of the eutectic Sn-Bi solder joint, but Ag had a more significant effect. However, when both Sb and Ag were added to eutectic Sn-Bi, the saturation stress was lower than when 1 wt.% Ag alone was added. In terms of relative behavior, the Sb-free 42Sn-Bi-1Ag aged for 250 h had the highest saturation stress of all tested alloys, while as-reflowed eutectic Sn-Bi had the lowest saturation stress. These results suggest that the alloy design strategy for Sn-Ag-Cu alloys, i.e., assuming that the effects of individual alloying elements are additive and independent, is not valid when Sb is added to Sn-Bi low-temperature solder. Graphical Abstract | Effect of Sb and Ag Addition and Aging on the Microstructural Evolution, IMC Layer Growth, and Mechanical Properties of Near-Eutectic Sn-Bi Alloys | 10.1007/s11664-023-10866-0 |
2024-03-01 | Low nitrogen use efficiency (NUE) in corn production leads to reduced harvest and substantial nitrogen (N) losses, adversely impacting environment and agricultural sustainability goals. Controlled release of N fertilizers can improve NUE by controlling the release of N from fertilizer granules, extending N availability to crops, and reducing N loss to the environment. Biochar-based controlled-release N fertilizers (BCRNFs) are a new concept to address the N loss problem and increase yield. In this research, different BCRNFs were developed by impregnating ammonium sulphate (AS) into biochar (BC) and mixing with bentonite (Be), biosolid (BS), rice starch (RS), and bioasphalt (BA) in a different ratio to formulate three new BCRNFs— S1: 40% AS + 55% BC + 5% RS; S2: 50% AS + 15% BC + 15% BS + 20% RS; and S3: 15% AS + 30% BC + 10% Be + 45% BA. Dry pellets of S1 and S2 were coated with 5 wt% poly-lactic acid solution, while pellets of S3 were not coated. The release pattern of N from the BCRNFs was studied in water. The cumulative release of NH 4 + –N from S1, S2, and S3 was significantly slower than that from AS. The release time of 80% N from S3 was extended up to 30 h. The greenhouse evaluation of BCRNFs consisted of six treatments: control (no N), non-BC commercial controlled-release fertilizer (CCRF), AS, S1, S2, and S3. S1, S2, and S3 corn yields were 196.4%, 209.6%, and 135.7%, respectively, greater than the control treatment ( p ≤ 0.05, Tukey’s test). S2 yielded 13.5% and 28.8% more than the non-BC controlled-release fertilizer and AS, respectively. The study demonstrated that BCRNFs coated with poly-lactic acids extend N release duration, boost yield, and reduce N loss in leachate collected in the greenhouse trial of the BCRNFs. Biochar-based BCRNFs have a good prospect for corn production. | Greenhouse Evaluation of Biochar-Based Controlled-Release Nitrogen Fertilizer in Corn Production | 10.1007/s40003-023-00673-8 |
2024-03-01 | To investigate a highly active catalyst for CER and explore low concentrations of Cl − electrocatalytic product Cl 2 , Co 3 O 4 /GF catalysts were constructed by a methanesulfonic acid system plating and calcination process. SEM shows Co 3 O 4 /GF-0.1 has a uniform distribution of nanoparticles. TEM, XRD, and XPS results confirmed the formation of Co 3 O 4 . The catalytic activity in high concentrations of Cl − and low concentrations of Cl − are discussed. LSV suggests Co 3 O 4 /GF-0.1 with an initial potential of 1.06 V, The overpotential at a current density of 10 mA cm −2 is 232 m V, Tafel slope 109.26 mV dec −1 , the CER reaction order is 0.54 at 1, 2 and 3 M NaCl, and 0.18 at 4, 5 and 6 M NaCl, too high concentration of Cl − slow down control of speed. In low concentration solution, the CER reaction order is 0.99, which can achieve the degradation rate of 90.8% in 50 ppm ammonia nitrogen. The apparent constant and the concentration of Cl − conform to the equation K = 1.44 × 10 –3 C 0 0.95 . From low concentration to high concentration, energy consumption decreased, and Faraday efficiency increased. Electrode with j ECSA = 0.52 mA cm −2 , 3D structure GF has a large specific active area that promotes the diffusion of Cl − . This work provides analysis methods and ideas for the preparation of the high activity and stability CER catalyst at low Cl − concentrations in the actual water body. Graphical Abstract | 3D-Graphite Felt Self-loaded Rich Co3O4 Nanoparticle Electrodes for Chlorine Evolution Reaction at Low Concentration Chloride Ion | 10.1007/s10562-023-04338-7 |
2024-03-01 | Single-crystal silicon, a typical hard and brittle material, is widely used in various fields due to its exceptional material properties. However, grinding of silicon is facing great challenges such as surface and subsurface damages due to the hardness and brittleness of the material. To increase the grinding force ratio of tangential to normal force and enhance surface/subsurface quality during silicon grinding, a novel approach employing a newly developed body-armor-like abrasive tool (BAAT) with soft-hard combined substrate has been proposed to achieve high-shear and low-pressure grinding. The grinding principle of this new BAAT with its soft-hard combined substrate was interpreted in comparison to the previous BAAT. The influence of dimension parameters and material properties of the new BAAT on the contact region were analyzed using commercially available software, i.e., Abaqus. The optimal BAAT configuration with a soft-hard combined substrate was determined as elastomer hardness of 50 HA, wheel diameter of 120 mm, and elastomer thickness of 15 mm. Subsequent grinding tests were conducted to assess the performance in terms of surface roughness ( R a ), grinding force, and surface morphology using this newly developed BAAT under various conditions. With the new BAAT, the grinding force ratio, defined as the tangential force to the normal force, was calculated as 0.45. The optimum grinding conditions were identified as a feed rate of 500 mm/min, wheel velocity of 8 m/s, abrasive grain size of 0.5 μm, and abrasive mass fraction of 5%. Under the optimal conditions, the surface roughness ( R a ) of the workpiece decreased from 273.3 to 45.0 nm after 12 strokes with an improvement of 83.5%. It was observed that the deep pits and scratches of the initial workpiece surface were completely removed with relatively uniform grinding textures generated on the ground workpiece surface. The results demonstrated that high-shear and low-pressure grinding using the new BAAT was capable of attaining high-quality grinding for single-crystal silicon. | Study on high-shear and low-pressure grinding using a new BAAT with soft-hard combined substrate for single-crystal silicon | 10.1007/s00170-024-13141-6 |
2024-03-01 | The resource utilization of agricultural and forestry waste, especially the high-value transformation of low-grade phosphate rock and derivatives, is an important way to achieve sustainable development. This study focuses on the impregnation and co-pyrolysis of rice straw (RS) with fused calcium magnesium phosphate (FMP), FMP modified with citric acid (CA-FMP), and calcium dihydrogen phosphate (MCP) to produce three phosphorous-enriched biochars (PBC). The Cd(II) removal efficiency of biochars before and after phosphorus modification was investigated, along with the adsorption mechanism and contribution of biochars modified with different phosphorus sources to Cd(II) adsorption. The result indicated that CA-FMP and MCP could be more uniformly loaded onto biochar, effectively increasing the specific surface area (SSA) and total pore volume. The adsorption of Cd(II) onto PBC followed a mono-layer chemisorption process accompanied by intraparticle diffusion. The adsorption of Cd(II) by PBC involved ion exchange, mineral precipitation, complexation with oxygen-containing functional groups (OFGs), cation-π interaction, electrostatic interaction, and physical adsorption. Ion exchange was identified as the primary adsorption mechanism for Cd(II) by BC and FBC (51.53% and 53.15% respectively), while mineral precipitation played a major role in the adsorption of Cd(II) by CBC and MBC (51.10% and 47.98% respectively). Moreover, CBC and MBC significantly enhanced the adsorption capacity of Cd(II), with maximum adsorption amounts of 128.1 and 111.5 mg g −1 respectively. Graphical Abstract | Adsorption effect and mechanism of Cd(II) by different phosphorus-enriched biochars | 10.1007/s11356-024-32308-y |
2024-03-01 | Indoor air pollution is an environmental health challenge in Kenya, particularly in rural households, and low-income urban areas. This review aims to provide an overview of the sources, health effects and mitigation strategies for indoor air pollutants in Kenya. The main goal of our study was to review existing literature on indoor air pollution in Kenya with the aim of identifying research gaps for future research. Our methodology involved a critical examination of the existing literature review. This is because traditional fuel burning for cooking and heating, and kerosene lamps are major sources of indoor air pollution. Exposure to air pollutants can lead to respiratory and cardiovascular disease among women and children who are more vulnerable. Despite efforts to improve indoor air quality, significant challenges remain including access to clean fuels and technologies, inadequate infrastructure, and low awareness of health impact of indoor air pollution. Mitigation strategies include the transition to cleaner cooking sources, solar lamps for lighting and education campaigns on health impacts. The review concludes that a multifaceted approach involving various stakeholders is necessary to effectively address indoor air pollution in Kenya and improve public health. | Indoor Air Pollution in Kenya | 10.1007/s41810-023-00205-5 |
2024-03-01 | Environmental DNA (eDNA) surveys have gained popularity as a highly sensitive detection tool that generally outperform traditional detection techniques. eDNA surveys can provide a cost-effective means to identify species’ distributions and recent incursions, informing the control or containment of invasive species. The red-eared slider turtle, Trachemys scripta elegans , is one of the world’s most invasive species and is listed as a priority pest species for management in Australia. In this study, we validate two eDNA assays to detect this invasive turtle in Australia. We demonstrate high sensitivity in a laboratory setting and perfect detection rates in mesocosms for one of these eDNA assays but show that this does not translate to high detection rates in urban waterbodies at sites of known occupancy. In fact, our results suggest eDNA surveys provide sub-optimal performance compared to traditional detection methods for T.s. elegans . We suggest the capacity for eDNA surveys to provide a highly sensitive detection tool must be evaluated in natural environments on a species-by-species basis to understand any limitations and to avoid high error rates from eDNA surveys leading to wasted resources or inappropriate management decisions. For management of T.s. elegans in Australia, clearly defining the utility of certain eDNA based approaches to detect T.s. elegans and their incursions is vital for effective management of this pest species. | Does mesocosm validation of environmental DNA methods translate to natural environment monitoring applications? A case study detecting a high-profile invader; the red eared slider turtle, Trachemys scripta elegans, in Australia | 10.1007/s12686-023-01333-3 |
2024-03-01 | The theoretical modelling of electrostatic lower hybrid waves (LHWs) is investigated using a kinetic treatment involving an electron beam. This electron beam propagates through a magnetized dusty plasma cylinder that consists of dust grains, electrons, and positively charged potassium ions ( K +). The excitation of LHWs via Cerenkov interaction using an analytical model is driven to instability. In order to explain how a population of charged dust particles affects the LHWs growth rate in a plasma that has been stimulated by an electron beam, a dispersion relation has been developed. The dust grain particles impact has been discussed on the growth rate of LHWs, and it was discovered that with the rise in relative density of dust grains, the growth rate of LHWs augments. Also, the growth rate of the unstable mode decreases with the frequency of the lower hybrid wave. Furthermore, the critical drift velocity for excitation of the mode is derived, and it was observed that it decreases as the relative density of negatively charged dust grains augments. The current study's findings align with the existing experimental observations. | Kinetic treatment of lower hybrid waves excitation in a magnetized dusty plasma by electron beam | 10.1007/s12648-023-02865-y |
2024-03-01 | Hydrogen sulfide (H 2 S) is a significant physiologic inhibitory neurotransmitter. The main goal of this research was to examine the contribution of diverse potassium (K + ) channels and nitric oxide (NO) in mediating the H 2 S effect on electrical field stimulation (EFS)-induced neurogenic contractile responses in the lower esophageal sphincter (LES). EFS-induced contractile responses of rabbit isolated LES strips were recorded using force transducers in organ baths that contain Krebs–Henseleit solutions (20 ml). Cumulative doses of NaHS, L-cysteine, PAG, and AOAA were evaluated in NO-dependent and NO-independent groups. The experiments were conducted again in the presence of K + channel blockers. In both NO-dependent and NO-independent groups, NaHS, L-cysteine, PAG, and AOAA significantly reduced EFS-induced contractile responses. In the NO-dependent group, the effect of NaHS and L-cysteine decreased in the presence of 4-AP, and also the effect of NaHS decreased in the NO-dependent and independent group in the presence of TEA. In the NO-independent group, K + channel blockers didn’t change L-cysteine-induced relaxations. K + channel blockers had no impact on the effects of PAG and AOAA. In addition, NaHS significantly relaxed 80-mM KCl-induced contractions, whereas L-cysteine, PAG, and AOAA did not. In the present study, H 2 S decreased the amplitudes of EFS-induced contraction responses. These results suggest that Kv channels and NO significantly contribute to exogenous H 2 S and endogenous H 2 S precursor L-cysteine inhibitory effect on lower esophageal sphincter smooth muscle. | Effects of hydrogen sulfide on relaxation responses in the lower esophageal sphincter in rabbits: the potential role of potassium channels | 10.1007/s00210-023-02695-z |
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