Design of reinforced concrete walls casted in place for the maximum normal stress of compression
T. C. Braguim
Full Text Available It is important to evaluate which designing models are safe and appropriate to structural analysis of buildings constructed in Concrete Wall system. In this work it is evaluated, through comparison of maximum normal stress of compression, a simple numerical model, which represents the walls with frame elements, with another much more robust and refined, which represents the walls with shells elements. The designing of the normal stress of compression it is done for both cases, based on NBR 16055, to conclude if the wall thickness initially adopted, it is enough or not.
The maximum force in a column under constant speed compression
Kuzkin, Vitaly A
2015-01-01
Dynamic buckling of an elastic column under compression at constant speed is investigated assuming the first-mode buckling. Two cases are considered: (i) an imperfect column (Hoff's statement), and (ii) a perfect column having an initial lateral deflection. The range of parameters, where the maximum load supported by a column exceeds Euler static force is determined. In this range, the maximum load is represented as a function of the compression rate, slenderness ratio, and imperfection/initial deflection. Considering the results we answer the following question: "How slowly the column should be compressed in order to measure static load-bearing capacity?" This question is important for the proper setup of laboratory experiments and computer simulations of buckling. Additionally, it is shown that the behavior of a perfect column having an initial deflection differ significantlys form the behavior of an imperfect column. In particular, the dependence of the maximum force on the compression rate is non-monotoni...
49 CFR 230.24 - Maximum allowable stress.
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Maximum allowable stress. 230.24 Section 230.24... Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value. The maximum allowable stress value on any component of a steam locomotive boiler shall not exceed 1/4 of the ultimate...
High precision Hugoniot measurements of D2 near maximum compression
Benage, John; Knudson, Marcus; Desjarlais, Michael
2015-11-01
The Hugoniot response of liquid deuterium has been widely studied due to its general importance and to the significant discrepancy in the inferred shock response obtained from early experiments. With improvements in dynamic compression platforms and experimental standards these results have converged and show general agreement with several equation of state (EOS) models, including quantum molecular dynamics (QMD) calculations within the Generalized Gradient Approximation (GGA). This approach to modeling the EOS has also proven quite successful for other materials and is rapidly becoming a standard approach. However, small differences remain among predictions obtained using different local and semi-local density functionals; these small differences show up in the deuterium Hugoniot at ~ 30-40 GPa near the region of maximum compression. Here we present experimental results focusing on that region of the Hugoniot and take advantage of advancements in the platform and standards, resulting in data with significantly higher precision than that obtained in previous studies. These new data may prove to distinguish between the subtle differences predicted by the various density functionals. Results of these experiments will be presented along with comparison to various QMD calculations. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin company, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Maximum twin shear stress factor criterion for sliding mode fracture initiation
黎振兹; 李慧剑; 黎晓峰; 周洪彬; 郝圣旺
2002-01-01
Previous researches on the mixed mode fracture initiation criteria were mostly focused on opening mode fracture. In this study, the authors proposed a new criterion for mixed mode sliding fracture initiation, which is the maximum twin shear stress factor criterion. The authors studied a finite width plate with central slant crack, subject to a far-field uniform uniaxial tensile or compressive stress.
Compression Enhanced Shear Yield Stress of Electrorheological Fluid
ZHANG Min-Liang; TIAN Yu; JIANG Ji-Le; ZHU Xu-Li; MENG Yong-Gang; WEN Shi-Zhu
2009-01-01
@@ Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful [or developing high performance flexible ER or magnetorheological couplings.
On some method of the space elevator maximum stress reduction
Ambartsumian S. A.
2007-03-01
Full Text Available The possibility of the realization and exploitation of the space elevator project is connected with a number of complicated problems. One of them are large elastic stresses arising in the space elevator ribbon body, which are considerably bigger that the limit of strength of modern materials. This note is devoted to the solution of problem of maximum stress reduction in the ribbon by the modification of the ribbon cross-section area.
Foam behavior of solid glass spheres – Zn22Al2Cu composites under compression stresses
Aragon-Lezama, J.A., E-mail: alja@correo.azc.uam.mx [Departamento de Materiales, Universidad Autónoma Metropolitana-A, Avenida San Pablo 180, Colonia Reynosa Tamaulipas, 02200 México, D.F., México (Mexico); Garcia-Borquez, A., E-mail: a.garciaborquez@yahoo.com.mx [Ciencia de Materiales, ESFM – Instituto Politécnico Nacional, Edif. 9, Unid. Prof. A. Lopez Mateos, Colonia Lindavista, 07738 México, D.F., México (Mexico); Torres-Villaseñor, G., E-mail: gtorres@unam.mx [Departamento de Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apdo., P 70-360, México, D.F., México (Mexico)
2015-06-25
Solid glass spheres – Zn22Al2Cu composites, having different densities and microstructures, were elaborated and studied under compression. Their elaboration process involves alloy melting, spheres submersion into the liquid alloy and finally air cooling. The achieved composites with densities 2.6884, 2.7936 and 3.1219 g/cm{sup 3} were studied in casting and thermally induced, fine-grain matrix microstructures. Test samples of the composites were compressed at a 10{sup −3} s{sup −1} strain rate, and their microstructure characterized before and after compression by using optical and scanning electron microscopes. Although they exhibit different compression behavior depending on their density and microstructure, all of them show an elastic region at low strains, reach their maximum stress (σ{sub max}) at hundreds of MPa before the stress fall or collapse up to a lowest yield point (LYP), followed by an important plastic deformation at nearly constant stress (σ{sub p}): beyond this plateau, an extra deformation can be limitedly reached only by a significant stress increase. This behavior under compression stresses is similar to that reported for metal foams, being the composites with fine microstructure which nearest behave to metal foams under this pattern. Nevertheless, the relative values of the elastic modulus, and maximum and plateau stresses do not follow the Ashby equations by changing the relative density. Generally, the studied composites behave as foams under compression, except for their peculiar parameters values (σ{sub max}, LYP, and σ{sub p})
Cold compression residual stress reduction in aluminium alloy 7010
Tanner, D.A. [Limerick Univ. (Ireland). Materials Research Centre; Robinson, J.S. [Dept. of Materials Science and Technology, Univ. of Limerick (Ireland); Cudd, R.L. [HDA Forgings Ltd., Redditch, Worchestershire (United Kingdom)
2000-07-01
7010 is one of the high strength aluminium alloys used mainly as plate and forgings in the aerospace industry. Its high strength is achieved through a quenching operation where the material is rapidly cooled from the solution heat treatment temperature (475 C) to room temperature. As with all rapid quenching operations, residual stresses develop, leaving the material unsuitable for further machining operations and for service. Regular shaped forgings are generally cold compressed after quenching to relieve residual stresses. The effect of friction, increasing/decreasing the amount of cold compression and applying cold compression in 'bites' on residual stress magnitudes is unknown. This paper aims to study the effect that these variables have on final residual stress patterns through use of a finite element model. (orig.)
Maximum-Entropy Meshfree Method for Compressible and Near-Incompressible Elasticity
Ortiz, A; Puso, M A; Sukumar, N
2009-09-04
Numerical integration errors and volumetric locking in the near-incompressible limit are two outstanding issues in Galerkin-based meshfree computations. In this paper, we present a modified Gaussian integration scheme on background cells for meshfree methods that alleviates errors in numerical integration and ensures patch test satisfaction to machine precision. Secondly, a locking-free small-strain elasticity formulation for meshfree methods is proposed, which draws on developments in assumed strain methods and nodal integration techniques. In this study, maximum-entropy basis functions are used; however, the generality of our approach permits the use of any meshfree approximation. Various benchmark problems in two-dimensional compressible and near-incompressible small strain elasticity are presented to demonstrate the accuracy and optimal convergence in the energy norm of the maximum-entropy meshfree formulation.
Kaganovich, Igor D., E-mail: ikaganov@pppl.gov [Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Massidda, Scott; Startsev, Edward A.; Davidson, Ronald C. [Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Vay, Jean-Luc [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Friedman, Alex [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)
2012-06-21
Neutralized drift compression offers an effective means for particle beam pulse compression and current amplification. In neutralized drift compression, a linear longitudinal velocity tilt (head-to-tail gradient) is applied to the non-relativistic beam pulse, so that the beam pulse compresses as it drifts in the focusing section. The beam current can increase by more than a factor of 100 in the longitudinal direction. We have performed an analytical study of how errors in the velocity tilt acquired by the beam in the induction bunching module limit the maximum longitudinal compression. It is found that the compression ratio is determined by the relative errors in the velocity tilt. That is, one-percent errors may limit the compression to a factor of one hundred. However, a part of the beam pulse where the errors are small may compress to much higher values, which are determined by the initial thermal spread of the beam pulse. It is also shown that sharp jumps in the compressed current density profile can be produced due to overlaying of different parts of the pulse near the focal plane. Examples of slowly varying and rapidly varying errors compared to the beam pulse duration are studied. For beam velocity errors given by a cubic function, the compression ratio can be described analytically. In this limit, a significant portion of the beam pulse is located in the broad wings of the pulse and is poorly compressed. The central part of the compressed pulse is determined by the thermal spread. The scaling law for maximum compression ratio is derived. In addition to a smooth variation in the velocity tilt, fast-changing errors during the pulse may appear in the induction bunching module if the voltage pulse is formed by several pulsed elements. Different parts of the pulse compress nearly simultaneously at the target and the compressed profile may have many peaks. The maximum compression is a function of both thermal spread and the velocity errors. The effects of the
Ikumi, Noriharu; Suzawa, Tetsuo; Yoshimura, Kentaro; Kamijo, Ryutaro
2015-01-01
Mechanical imbalance caused by mechanical overload or poor bone quality around a dental implant can result in osseointegration failure. To avoid that, it is important to identify an appropriate safety stress margin (critical stress level). For this study, a novel device was developed to generate a quantitative amount of static compressive stress under an aseptic closed condition. The aim was to clarify the amount of critical stress produced on the cortical bone when static compression is applied to the osseointegrated bone-implant interface. Small parts for bone sustaining, load generation, and load transmittance were developed to generate quantitative static compressive stress at the bone-implant interface and implanted inside the tibial cortical bone in adult beagle dogs. Each tibia in two dogs received bone-sustaining parts, then after 2 months, the load-transmitting parts were placed into the bone-sustaining parts. After another 2 months, various magnitudes of static compressive stress (0-180 MPa) were generated by tightening the load-generating part to the osseointegrated bone-implant interface. After 7 days, the animals were euthanized, and dissected blocks were prepared for histomorphometric analyses. There were no obvious signs of bone resorption or loss of osseointegration in any of the dogs. The change in shape of osteon was not influenced by the amount of static compressive stress. However, periosteal reactions were observed under the cortical bone on the opposite side. These results indicate that osseointegrated bone-implant interfaces show minimal response based on the magnitude of static compressive stress, even when such stress is greater than 120 MPa.
Stress analysis of single joint rock mass under triaxial compression
LIU Xin-rong(刘新荣); JIANG Shu-ping(蒋树屏); LI Xiao-hong(李晓红); BAO Tai(包太)
2004-01-01
Based on the fundamental principle of rock mechanics, the stresses of single joint rock mass under three-dimensional compression were analyzed. The effect of the intermediate principle stress on the strength of single joint rock mass were discussed in particular. It is found that the strength of single joint rock are affected by the intermediate principal stress, which may be the main factor in some conditions.
Soil Compressibility Models for a Wide Stress Range
Chong, Song-Hun
2016-03-03
Soil compressibility models with physically correct asymptotic void ratios are required to analyze situations that involve a wide stress range. Previously suggested models and other functions are adapted to satisfy asymptotic void ratios at low and high stress levels; all updated models involve four parameters. Compiled consolidation data for remolded and natural clays are used to test the models and to develop correlations between model parameters and index properties. Models can adequately fit soil compression data for a wide range of stresses and soil types; in particular, models that involve the power of the stress σ\\'β display higher flexibility to capture the brittle response of some natural soils. The use of a single continuous function avoids numerical discontinuities or the need for ad hoc procedures to determine the yield stress. The tangent stiffness-readily computed for all models-should not be mistaken for the small-strain constant-fabric stiffness. © 2016 American Society of Civil Engineers.
Magnitude-dependent response of osteoblasts regulated by compressive stress
Shen, Xiao-qing; Geng, Yuan-ming; Liu, Ping; Huang, Xiang-yu; Li, Shu-yi; Liu, Chun-dong; Zhou, Zheng; Xu, Ping-ping
2017-01-01
The present study aimed to investigate the role of magnitude in adaptive response of osteoblasts exposed to compressive stress. Murine primary osteoblasts and MC3T3-E1 cells were exposed to compressive stress (0, 1, 2, 3, 4, and 5 g/cm2) in 3D culture. Cell viability was evaluated, and expression levels of Runx2, Alp, Ocn, Rankl, and Opg were examined. ALP activity in osteoblasts and TRAP activity in RAW264.7 cells co-cultured with MC3T3-E1 cells were assayed. Results showed that compressive stress within 5.0 g/cm2 did not influence cell viability. Both osteoblastic and osteoblast-regulated osteoclastic differentiation were enhanced at 2 g/cm2. An increase in stress above 2 g/cm2 did not enhance osteoblastic differentiation further but significantly inhibited osteoblast-regualted osteoclastic differentiation. This study suggested that compressive stress regulates osteoblastic and osteoclastic differentiation through osteoblasts in a magnitude-dependent manner. PMID:28317941
Compression or tension? The stress distribution in the proximal femur
Meakin JR
2006-02-01
Full Text Available Abstract Background Questions regarding the distribution of stress in the proximal human femur have never been adequately resolved. Traditionally, by considering the femur in isolation, it has been believed that the effect of body weight on the projecting neck and head places the superior aspect of the neck in tension. A minority view has proposed that this region is in compression because of muscular forces pulling the femur into the pelvis. Little has been done to study stress distributions in the proximal femur. We hypothesise that under physiological loading the majority of the proximal femur is in compression and that the internal trabecular structure functions as an arch, transferring compressive stresses to the femoral shaft. Methods To demonstrate the principle, we have developed a 2D finite element model of the femur in which body weight, a representation of the pelvis, and ligamentous forces were included. The regions of higher trabecular bone density in the proximal femur (the principal trabecular systems were assigned a higher modulus than the surrounding trabecular bone. Two-legged and one-legged stances, the latter including an abductor force, were investigated. Results The inclusion of ligamentous forces in two-legged stance generated compressive stresses in the proximal femur. The increased modulus in areas of greater structural density focuses the stresses through the arch-like internal structure. Including an abductor muscle force in simulated one-legged stance also produced compression, but with a different distribution. Conclusion This 2D model shows, in principle, that including ligamentous and muscular forces has the effect of generating compressive stresses across most of the proximal femur. The arch-like trabecular structure transmits the compressive loads to the shaft. The greater strength of bone in compression than in tension is then used to advantage. These results support the hypothesis presented. If correct, a
Determination of Mechanical Properties of Micromembranes with Compressive Residual Stress
无
2000-01-01
A novel model of a load-deflection method to determine the mechanical properties of micromembranes with compressive residual stress is described. Since thin film structures are frequently used in micro devices, characterisation of mechanical properties of thin films is desired by the design and fabrication of micromachines. In this paper, the mechanical properties of thin micromembranes under compressive stress are characterised, which are fabricated by bulk micromachining. The relation between the center deflection and the load pressure on a square membrane is deduced by modelling the membrane as an elastic plate having large deflection with clamped boundaries. According to the model, whether the membrane has initial deflection or not has no effect on the measurement result. The Young's modulus and residual stress are simultaneously determined. The mechanical properties of siliconoxide, silicon nitride membranes and composite membranes of polysilicon with silicon nitride are measured.
Shen, Hua
2016-10-19
A maximum-principle-satisfying space-time conservation element and solution element (CE/SE) scheme is constructed to solve a reduced five-equation model coupled with the stiffened equation of state for compressible multifluids. We first derive a sufficient condition for CE/SE schemes to satisfy maximum-principle when solving a general conservation law. And then we introduce a slope limiter to ensure the sufficient condition which is applicative for both central and upwind CE/SE schemes. Finally, we implement the upwind maximum-principle-satisfying CE/SE scheme to solve the volume-fraction-based five-equation model for compressible multifluids. Several numerical examples are carried out to carefully examine the accuracy, efficiency, conservativeness and maximum-principle-satisfying property of the proposed approach.
Massidda, Scott; Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.; Lidia, Steven M.; Seidl, Peter; Friedman, Alex
2012-06-01
Neutralized drift compression offers an effective means for particle beam focusing and current amplification with applications to heavy ion fusion. In the Neutralized Drift Compression eXperiment-I (NDCX-I), a non-relativistic ion beam pulse is passed through an inductive bunching module that produces a longitudinal velocity modulation. Due to the applied velocity tilt, the beam pulse compresses during neutralized drift. The ion beam pulse can be compressed by a factor of more than 100; however, errors in the velocity modulation affect the compression ratio in complex ways. We have performed a study of how the longitudinal compression of a typical NDCX-I ion beam pulse is affected by the initial errors in the acquired velocity modulation. Without any voltage errors, an ideal compression is limited only by the initial energy spread of the ion beam, ΔΕb. In the presence of large voltage errors, δU≫ΔEb, the maximum compression ratio is found to be inversely proportional to the geometric mean of the relative error in velocity modulation and the relative intrinsic energy spread of the beam ions. Although small parts of a beam pulse can achieve high local values of compression ratio, the acquired velocity errors cause these parts to compress at different times, limiting the overall compression of the ion beam pulse.
Massidda, Scott [Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kaganovich, Igor D., E-mail: ikaganov@pppl.gov [Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Startsev, Edward A.; Davidson, Ronald C. [Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Lidia, Steven M.; Seidl, Peter [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Friedman, Alex [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States)
2012-06-21
Neutralized drift compression offers an effective means for particle beam focusing and current amplification with applications to heavy ion fusion. In the Neutralized Drift Compression eXperiment-I (NDCX-I), a non-relativistic ion beam pulse is passed through an inductive bunching module that produces a longitudinal velocity modulation. Due to the applied velocity tilt, the beam pulse compresses during neutralized drift. The ion beam pulse can be compressed by a factor of more than 100; however, errors in the velocity modulation affect the compression ratio in complex ways. We have performed a study of how the longitudinal compression of a typical NDCX-I ion beam pulse is affected by the initial errors in the acquired velocity modulation. Without any voltage errors, an ideal compression is limited only by the initial energy spread of the ion beam, {Delta}{Epsilon}{sub b}. In the presence of large voltage errors, {delta}U Double-Nested-Greater-Than {Delta}E{sub b}, the maximum compression ratio is found to be inversely proportional to the geometric mean of the relative error in velocity modulation and the relative intrinsic energy spread of the beam ions. Although small parts of a beam pulse can achieve high local values of compression ratio, the acquired velocity errors cause these parts to compress at different times, limiting the overall compression of the ion beam pulse.
无
2001-01-01
The thermal residual stresses and the stress distributions of short fiber reinforced metal matrix composite under tensile and compressive loadings were studied using large strain axisymmetric elasto-plastic finite element method. It is demonstrated that the thermal residual stresses can result in asymmetrical stress distributions and matrix plasticity. The thermal residual stresses decrease the stress transfer in tension and enhance the stress transfer in compression. The fiber volume fraction has more important effects on the thermal residual stresses and the stress distributions under tensile and compressive loadings than the fiber aspect ratio and the fiber end distance.
Schümann Kerstin
2016-09-01
Full Text Available Thermoplastic polymers exhibit non-isochoric behaviour during tensile and compression testing as well as particular deformations like local necking (tension or buckling (compression. A method for the determination of Cauchy stresses from tensile and compression tests is presented, that considers the actual deformations of the test specimens. The exact geometry of the specimens in the respective present configuration is determined in photographs, which are taken continuously throughout the test. The engineering stresses at several time points are converted into Cauchy stresses using newly developed formulas in consideration of the actual specimen geometry. For validation finite element analyses of the tensile and compression tests are performed using the identified stress-strain curves. The numerical results show good agreement with the experiments for the tested polymers. Thus a method for conversion of engineering to Cauchy stresses in tensile and compression tests could be established considering the non-isochoric deformation in plasticity. With this method “true” stress-strain curves as input for finite element material models can be identified for arbitrary materials.
Resistance Responses of Carbon Fiber Cement to Cycled Compressive Stresses
SHUI Zhonghe; LI Chao; LIAO Weidong
2005-01-01
The stress-resistance relationship of carbon fiber cement was studicd. Attention has been paid to explore the improvement of the stress-resistance sensitivity under cycled stress restriction. The prismy carbon fiber cement sensors were pre-fabricated. The factors such as contents of carbon fibers, silica fume, dispersant and the w/ c were taken into account. The electrical resistance variations with the dynamic and static loads were simulated using a strain-controlled test machine. The test results show that there is an optimal fiber content, with which the compression-sensitivity achieves a high level. The addition of silica fume can improve the sensitivity. Urder the optimal test conditions, the measured resistances can greatly correspond with the changes of the load.
Discrete fracture in quasi-brittle materials under compressive and tensile stress states
Klerck, PA
2004-01-01
Full Text Available A method for modelling discrete fracture in geomaterials under tensile and compressive stress fields has been developed based on a Mohr-Coulomb failure surface in compression and three independent anisotropic rotating crack models in tension...
Alatawneh, Natheer; Rahman, Tanvir; Lowther, David A.; Chromik, Richard
2017-06-01
Electric machine cores are subjected to mechanical stresses due to manufacturing processes. These stresses include radial, circumferential and axial components that may have significant influences on the magnetic properties of the electrical steel and hence, on the output and efficiencies of electrical machines. Previously, most studies of iron losses due to mechanical stress have considered only radial and circumferential components. In this work, an improved toroidal tester has been designed and developed to measure the core losses and the magnetic properties of electrical steel under a compressive axial stress. The shape of the toroidal ring has been verified using 3D stress analysis. Also, 3D electromagnetic simulations show a uniform flux density distribution in the specimen with a variation of 0.03 T and a maximum average induction level of 1.5 T. The developed design has been prototyped, and measurements were carried out using a steel sample of grade 35WW300. Measurements show that applying small mechanical stresses normal to the sample thickness rises the delivered core losses, then the losses decrease continuously as the stress increases. However, the drop in core losses at high stresses does not go lower than the free-stress condition. Physical explanations for the observed trend of core losses as a function of stress are provided based on core loss separation to the hysteresis and eddy current loss components. The experimental results show that the effect of axial compressive stress on magnetic properties of electrical steel at high level of inductions becomes less pronounced.
Finite element stress analysis of a compression mold. Final report. [Using SASL and WILSON codes
Watterson, C.E.
1980-03-01
Thermally induced stresses occurring in a compression mold during production molding were evaluated using finite element analysis. A complementary experimental stress analysis, including strain gages and thermocouple arrays, verified the finite element model under typical loading conditions.
Yongxiang Xu
2014-01-01
Full Text Available Deep-sea permanent magnet motor equipped with fluid compensated pressure-tolerant system is compressed by the high pressure fluid both outside and inside. The induced stress distribution in stator core is significantly different from that in land type motor. Its effect on the magnetic properties of stator core is important for deep-sea motor designers but seldom reported. In this paper, the stress distribution in stator core, regarding the seawater compressive stress, is calculated by 2D finite element method (FEM. The effect of compressive stress on magnetic properties of electrical steel sheet, that is, permeability, BH curves, and BW curves, is also measured. Then, based on the measured magnetic properties and calculated stress distribution, the stator iron loss is estimated by stress-electromagnetics-coupling FEM. At last the estimation is verified by experiment. Both the calculated and measured results show that stator iron loss increases obviously with the seawater compressive stress.
Study of the stress-strain state of compressed concrete elements with composite reinforcement
Bondarenko Yurii
2017-01-01
Full Text Available The efficiency analysis of the application of glass composite reinforcement in compressed concrete elements as a load-carrying component has been performed. The results of experimental studies of the deformation-strength characteristics of this reinforcement on compression and compressed concrete cylinders reinforced by this reinforcement are presented. The results of tests and mechanisms of sample destruction have been analyzed. The numerical analysis of the stress-strain state has been performed for axial compression of concrete elements with glasscomposite reinforcement. The influence of the reinforcement percentage on the stressed state of a concrete compressed element with the noted reinforcement is estimated. On the basis of the obtained results, it is established that the glass-composite reinforcement has positive effect on the strength of the compressed concrete elements. That is, when calculating the load-bearing capacity of such structures, the function of composite reinforcement on compression should not be neglected.
Lemofouet, Sylvain; Rufer, Alfred
This paper presents a hybrid energy storage system mainly based on Compressed Air, where the storage and withdrawal of energy are done within maximum efficiency conditions. As these maximum efficiency conditions impose the level of converted power, an intermittent time-modulated operation mode is applied to the thermodynamic converter to obtain a variable converted power. A smoothly variable output power is achieved with the help of a supercapacitive auxiliary storage device used as a filter. The paper describes the concept of the system, the power-electronic interfaces and especially the Maximum Efficiency Point Tracking (MEPT) algorithm and the strategy used to vary the output power. In addition, the paper introduces more efficient hybrid storage systems where the volumetric air machine is replaced by an oil-hydraulics and pneumatics converter, used under isothermal conditions. Practical results are also presented, recorded from a low-power air motor coupled to a small DC generator, as well as from a first prototype of the hydro-pneumatic system. Some economical considerations are also made, through a comparative cost evaluation of the presented hydro-pneumatic systems and a lead acid batteries system, in the context of a stand alone photovoltaic home application. This evaluation confirms the cost effectiveness of the presented hybrid storage systems.
Incorporation of Mean/Maximum Stress Effects in the Multiaxial Racetrack Filter
Marco Antonio Meggiolaro
2016-10-01
Full Text Available This work extends the Multiaxial Racetrack Filter (MRF to incorporate mean or maximum stress effects, adopting a filter amplitude that depends on the current stress level along the stress or strain path. In this way, a small stress or strain amplitude event can be filtered out if associated with a non-damaging low mean or peak stress level, while another event with the very same amplitude can be preserved if happening under a more damaging high mean or peak stress level. The variable value of the filter amplitude must be calculated in real time, thus it cannot depend on the peak or mean stresses along a load event, because it would require cycle identification and as so information about future events. Instead, mean/maximum stress effects are modeled in the filter as a function of the current (instantaneous hydrostatic or normal stress along the multiaxial load path, respectively for invariantbased and critical-plane models. The MRF efficiency is evaluated from tension-torsion experiments in 316L stainless steel tubular specimens under non-proportional (NP load paths, showing it can robustly filter out nondamaging events even under multiaxial NP variable amplitude loading histories
Held, Louis F.; Pritchard, Ernest I.
1946-01-01
An investigation was conducted to evaluate the possibilities of utilizing the high-performance characteristics of triptane and xylidines blended with 28-R fuel in order to increase fuel economy by the use of high compression ratios and maximum-economy spark setting. Full-scale single-cylinder knock tests were run with 20 deg B.T.C. and maximum-economy spark settings at compression ratios of 6.9, 8.0, and 10.0, and with two inlet-air temperatures. The fuels tested consisted of triptane, four triptane and one xylidines blend with 28-R, and 28-R fuel alone. Indicated specific fuel consumption at lean mixtures was decreased approximately 17 percent at a compression ratio of 10.0 and maximum-economy spark setting, as compared to that obtained with a compression ratio of 6.9 and normal spark setting. When compression ratio was increased from 6.9 to 10.0 at an inlet-air temperature of 150 F, normal spark setting, and a fuel-air ratio of 0.065, 55-percent triptane was required with 28-R fuel to maintain the knock-limited brake power level obtained with 28-R fuel at a compression ratio of 6.9. Brake specific fuel consumption was decreased 17.5 percent at a compression ratio of 10.0 relative to that obtained at a compression ratio of 6.9. Approximately similar results were noted at an inlet-air temperature of 250 F. For concentrations up through at least 20 percent, triptane can be more efficiently used at normal than at maximum-economy spark setting to maintain a constant knock-limited power output over the range of compression ratios tested.
In-shoe plantar tri-axial stress profiles during maximum-effort cutting maneuvers.
Cong, Yan; Lam, Wing Kai; Cheung, Jason Tak-Man; Zhang, Ming
2014-12-18
Soft tissue injuries, such as anterior cruciate ligament rupture, ankle sprain and foot skin problems, frequently occur during cutting maneuvers. These injuries are often regarded as associated with abnormal joint torque and interfacial friction caused by excessive external and in-shoe shear forces. This study simultaneously investigated the dynamic in-shoe localized plantar pressure and shear stress during lateral shuffling and 45° sidestep cutting maneuvers. Tri-axial force transducers were affixed at the first and second metatarsal heads, lateral forefoot, and heel regions in the midsole of a basketball shoe. Seventeen basketball players executed both cutting maneuvers with maximum efforts. Lateral shuffling cutting had a larger mediolateral braking force than 45° sidestep cutting. This large braking force was concentrated at the first metatarsal head, as indicated by its maximum medial shear stress (312.2 ± 157.0 kPa). During propulsion phase, peak shear stress occurred at the second metatarsal head (271.3 ± 124.3 kPa). Compared with lateral shuffling cutting, 45° sidestep cutting produced larger peak propulsion shear stress (463.0 ± 272.6 kPa) but smaller peak braking shear stress (184.8 ± 181.7 kPa), of which both were found at the first metatarsal head. During both cutting maneuvers, maximum medial and posterior shear stress occurred at the first metatarsal head, whereas maximum pressure occurred at the second metatarsal head. The first and second metatarsal heads sustained relatively high pressure and shear stress and were expected to be susceptible to plantar tissue discomfort or injury. Due to different stress distribution, distinct pressure and shear cushioning mechanisms in basketball footwear might be considered over different foot regions.
Kim, K. M.; Smetana, P.
1990-03-01
Growth of large diameter Czochralski (CZ) silicon crystals require complete elimination of dislocations by means of Dash technique, where the seed diameter is reduced to a small size typically 3 mm in conjunction with increase in the pull rate. The maximum length of the large CZ silicon is estimated at the fracture stress limit of the seed neck diameter ( d). The maximum lengths for 200 and 300 mm CZ crystals amount to 197 and 87 cm, respectively, with d = 0.3 cm; the estimated maximum weight is 144 kg.
Lee, S. M. C.; Laurie, S. S.; Macias, B. R.; Willig, M.; Johnson, K.; Stenger, M. B.
2017-01-01
Astronauts and cosmonauts may experience symptoms of orthostatic intolerance during re-entry, landing, and for several days post-landing following short- and long-duration spaceflight. Presyncopal symptoms have been documented in approximately 20% of short-duration and greater than 60% of long-duration flyers on landing day specifically during 5-10 min of controlled (no countermeasures employed at the time of testing) stand tests or 80 deg head-up tilt tests. Current operational countermeasures to orthostatic intolerance include fluid loading prior to and whole body cooling during re-entry as well as compression garments that are worn during and for up to several days after landing. While both NASA and the Russian space program have utilized compression garments to protect astronauts and cosmonauts traveling on their respective vehicles, a "next-generation" gradient compression garment (GCG) has been developed and tested in collaboration with a commercial partner to support future space flight missions. Unlike previous compression garments used operationally by NASA that provide a single level of compression across only the calves, thighs, and lower abdomen, the GCG provides continuous coverage from the feet to below the pectoral muscles in a gradient fashion (from approximately 55 mm Hg at the feet to approximately 16 mmHg across the abdomen). The efficacy of the GCG has been demonstrated previously after a 14-d bed rest study without other countermeasures and after short-duration Space Shuttle missions. Currently the GCG is being tested during a stand test following long-duration missions (6 months) to the International Space Station. While results to date have been promising, interactions of the GCG with other space suit components have not been examined. Specifically, it is unknown whether wearing the GCG over NASA's Maximum Absorbency Garment (MAG; absorbent briefs worn for the collection of urine and feces while suited during re-entry and landing) will
Magnfält, D.; Fillon, A.; Boyd, R. D.; Helmersson, U.; Sarakinos, K.; Abadias, G.
2016-02-01
Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low.
Magnfält, D., E-mail: danma@ifm.liu.se; Sarakinos, K. [Nanoscale Engineering Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden); Fillon, A.; Abadias, G. [Institut P' , Département Physique et Mécanique des Matériaux, Université de Poitiers-CNRS-ENSMA, SP2MI, Téléport 2, Bd M. et P. Curie, F-86962 Chasseneuil-Futuroscope (France); Boyd, R. D.; Helmersson, U. [Plasma and Coatings Physics Division, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping (Sweden)
2016-02-07
Intrinsic stresses in vapor deposited thin films have been a topic of considerable scientific and technological interest owing to their importance for functionality and performance of thin film devices. The origin of compressive stresses typically observed during deposition of polycrystalline metal films at conditions that result in high atomic mobility has been under debate in the literature in the course of the past decades. In this study, we contribute towards resolving this debate by investigating the grain size dependence of compressive stress magnitude in dense polycrystalline Mo films grown by magnetron sputtering. Although Mo is a refractory metal and hence exhibits an intrinsically low mobility, low energy ion bombardment is used during growth to enhance atomic mobility and densify the grain boundaries. Concurrently, the lateral grain size is controlled by using appropriate seed layers on which Mo films are grown epitaxially. The combination of in situ stress monitoring with ex situ microstructural characterization reveals a strong, seemingly linear, increase of the compressive stress magnitude on the inverse grain size and thus provides evidence that compressive stress is generated in the grain boundaries of the film. These results are consistent with models suggesting that compressive stresses in metallic films deposited at high homologous temperatures are generated by atom incorporation into and densification of grain boundaries. However, the underlying mechanisms for grain boundary densification might be different from those in the present study where atomic mobility is intrinsically low.
Noise variation by compressive stress on the model core of power transformers
Mizokami, Masato, E-mail: mizokami.g76.masato@jp.nssmc.com; Kurosaki, Yousuke
2015-05-01
The reduction of audible noise generated by cores for power transformers has been required due to environmental concern. It is known that compressive stress in the rolling direction of electrical steel affects magnetostriction and it can result in an increase in noise level. In this research, the effect of compressive stress to noise was investigated on a 3-phase 3-limb model core. Compressive stress was applied in the rolling direction of the limbs from the outside of the core. It increased the sound pressure levels and the slope of the rise was about 2 dBA/MPa. Magnetostriction on single sheet samples was also measured under compressive stress and the harmonic components of the magnetostriction were compared with those of noise. It revealed that the variation in magnetostriction with compressive stress did not entirely correspond to that in noise. In one of the experiments, localized bending happened on one limb during compressing the core. While deformation of the core had not been intended, the noise was measured. The deformation increased the noise by more than 10 dBA and it occurred on most of the harmonic components. - Highlights: • Audible noise was measured on a model core to which compressive stress was applied. • The stress in the rolling direction of the steel causes a rise in noise level. • The slope of the rise in sound pressure level up to 2.5 MPa is about 2 dBA/MPa. • Variation in magnetostriction by stress does not entirely agree with that in noise. • Bend arisen in the core causes an extreme increase in noise.
Possibility of Inducing Compressive Residual Stresses in Welded Joints of SS400 Steels
无
2001-01-01
Since the welded constructions produce easily stress corrosion cracking (SCC) or fatigue disruption in corrosive medium or under ripple load, two methods inducing compressive stress on structural surfaces by anti-welding-heating treatment (AWHT) and explosion treatment (ET) are presented. The results show that they are good ways to resisting SCC on the welded SS400 steel or other components.
Van Loocke, M; Lyons, C G; Simms, C K
2008-01-01
The compressive properties of skeletal muscle are important in impact biomechanics, rehabilitation engineering and surgical simulation. However, the mechanical behaviour of muscle tissue in compression remains poorly characterised. In this paper, the time-dependent properties of passive skeletal muscle were investigated using a combined experimental and theoretical approach. Uniaxial ramp and hold compression tests were performed in vitro on fresh porcine skeletal muscle at various rates and orientations of the tissue fibres. Results show that above a very small compression rate, the viscoelastic component plays a significant role in muscle mechanical properties; it represents approximately 50% of the total stress reached at a compression rate of 0.5% s(-1). A stiffening effect with compression rate is observed especially in directions closer to the muscle fibres. Skeletal muscle viscoelastic behaviour is thus dependent on compression rate and fibre orientation. A model is proposed to represent the observed experimental behaviour, which is based on the quasi-linear viscoelasticity framework. A previously developed strain-dependent Young's Moduli formulation was extended with Prony series to account for the tissue viscoelastic properties. Parameters of the model were obtained by fitting to stress-relaxation data obtained in the muscle fibre, cross-fibre and 45 degrees directions. The model then successfully predicted stress-relaxation behaviour at 60 degrees from the fibre direction (errors muscle behaviour at rates of 0.05% s(-1) and 5% s(-1) (errors <25%).
Tensile stresses generated in pharmaceutical tablets by opposing compressive line loads.
Drake, K R; Newton, J M; Mokhtary-Saghafi, S; Davies, P N
2007-03-01
The distribution of tensile stress, across the splitting plane, has been investigated for the case when circular and square tablets are subjected to opposing compressive line loads acting in the through thickness direction. This type of loading is referred to in the paper as axial compression. Analytical solutions for the two-dimensional problem of a rectangular strip have been used to investigate the variation of stress in the through thickness direction and to consider the effects of load spreading. Three-dimensional finite element analysis has been used to investigate the variation in stress across the diameter, or breadth, of the tablets. It is shown that the magnitude of the tensile stress varies significantly throughout and that load spreading has an important influence on the stress distribution in the through thickness direction. Experiments have been carried out with microcrystalline cellulose (Avicel PH102) material for circular and square tablets to determine their breaking loads when subjected to axial compression and diametral compression. The experimental results show higher breaking loads for the case of axial compression. It is concluded that the platen contact width must be known in order to evaluate the exact value of the tensile strength of the tablet material when applying this test procedure.
Barbara Nasiłowska
2015-06-01
Full Text Available This article presents shot-peening effect on the structure, microhardness, and compressive stresses of the austenitic steel 1.4539. The research shows strengthening of the top layer and the formation of compressive stresses in the subsurface layers of the shot-peening elements.[b]Keyword[/b]: austenitic steel 1.4539, residual stresses, Waisman-Phillips’a method
Creep measurements confirm steady flow after stress maximum in extension of branched polymer melts
Javier Alvarez, Nicolas; Román Marín, José Manuel; Huang, Qian;
2013-01-01
We provide conclusive evidence of nonmonotonic mechanical behavior in the extension of long-chain branched polymer melts. While nonmonotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out...... the possibility of the overshoot being an experimental artifact by confirming the existence of steady flow after a maximum in the ratio of stress to strain rate versus strain under both constant stress and constant strain-rate kinematics. This observation indicates the omission of important physics from current...
Poulios, Konstantinos; Niordson, Christian Frithiof
2016-01-01
The compressive strength of unidirectionally or layer-wise reinforced composite materials in direction parallel to their reinforcement is limited by micro-buckling instabilities. Although the inherent compressive strength of a given material micro-structure can easily be determined by assessing its...... compressive stress but also on spatial stress or strain gradients, rendering failure initiation size scale dependent. The present work demonstrates and investigates the aforementioned effect through numerical simulations of periodically layered structures withnotches and holes under bending and compressive...... loads, respectively. The presented results emphasize the importance of the reinforcing layer thickness on the load carrying capacity of the investigated structures, at a constant volumetric fraction of the reinforcement. The observed strengthening at higher values of the relative layer thickness...
LIU Wei-qun; ZHU Li
2009-01-01
The relatively high stress probably leads to generation of a fractured or even instable area around a working coalface. Also, the generated weak area often evolves into an easy-infiltrating field of water/gas to greatly increase probability of accident occurrence. To reveal the distribution of high stress around working faces, we put forward the mode-I-crack compression model. In this model, the goaf following a working face is regarded as a mode-I crack in an infinite plate, and the self-gravity of overlaying strata is transformed into an uniform pressure applied normal to the upper edge of the model crack. Solving this problem is based on the Westergaard complex stress function. For comparison, the software RFPA-2D is also employed to simulate the same mining problem, and furthermore extendedly to calculate the stress interference induced by the simultaneous advances of two different working faces. The results show that, the area close to a working face or the goaf tail has the maximum stress, and the stress is distributed directly proportional to the square root of the advance and inversely proportional to the square root of the distance to the working face. The simultaneous advances of two neighboring working faces in different horizontals can lead to extremely high resultant stress in an interference area.
Burns, Brian; Wilson, Neil E; Furuyama, Jon K; Thomas, M Albert
2014-02-01
The four-dimensional (4D) echo-planar correlated spectroscopic imaging (EP-COSI) sequence allows for the simultaneous acquisition of two spatial (ky, kx) and two spectral (t2, t1) dimensions in vivo in a single recording. However, its scan time is directly proportional to the number of increments in the ky and t1 dimensions, and a single scan can take 20–40 min using typical parameters, which is too long to be used for a routine clinical protocol. The present work describes efforts to accelerate EP-COSI data acquisition by application of non-uniform under-sampling (NUS) to the ky–t1 plane of simulated and in vivo EP-COSI datasets then reconstructing missing samples using maximum entropy (MaxEnt) and compressed sensing (CS). Both reconstruction problems were solved using the Cambridge algorithm, which offers many workflow improvements over other l1-norm solvers. Reconstructions of retrospectively under-sampled simulated data demonstrate that the MaxEnt and CS reconstructions successfully restore data fidelity at signal-to-noise ratios (SNRs) from 4 to 20 and 5× to 1.25× NUS. Retrospectively and prospectively 4× under-sampled 4D EP-COSI in vivo datasets show that both reconstruction methods successfully remove NUS artifacts; however, MaxEnt provides reconstructions equal to or better than CS. Our results show that NUS combined with iterative reconstruction can reduce 4D EP-COSI scan times by 75% to a clinically viable 5 min in vivo, with MaxEnt being the preferred method. 2013 John Wiley & Sons, Ltd.
Research on flow stress of spray formed 70Si30Al ahoy under hot compression deformation
WEI Yanguang; XIONG Baiqing; ZHANG Yong'an; LIU Hongwei; ZHU Baohong; WANG feng
2006-01-01
The flow stress of spray formed 70Si30Al alloy was studied by hot compression on a Gleeble-1500 test machine.The experimental results indicated that the flow stress depends on the strain rate and the deformation temperature. The flow stress increases with an increase in strain rate at a given deformation temperature. The flow stress decreases with the deformation temperature increasing at a given strain rate. The relational expression among the flow stress, the strain rate, and the deformation temperature satisfies the Arrhenius equation. The deformation activation energy of 70Si30Al alloy during hot deformation is 866.27 kJ/mol from the Arrhenius equation.
Svenson, Mouritz N; Thirion, Lynn M; Youngman, Randall E; Mauro, John C; Rzoska, Sylwester J; Bockowski, Michal; Smedskjaer, Morten M
2014-07-09
Glass exhibits a significant change in properties when subjected to high pressure because the short- and intermediate-range atomic structures of glass are tunable through compression. Understanding the link between the atomic structure and macroscopic properties of glass under high pressure is an important scientific problem because the glass structures obtained via quenching from elevated pressure may give rise to properties unattainable under standard ambient pressure conditions. In particular, the chemical strengthening of glass through K(+)-for-Na(+) ion exchange is currently receiving significant interest due to the increasing demand for stronger and more damage-resistant glass. However, the interplay among isostatic compression, pressure-induced changes in alkali diffusivity, compressive stress generated through ion exchange, and the resulting mechanical properties are poorly understood. In this work, we employ a specially designed gas pressure chamber to compress bulk glass samples isostatically up to 1 GPa at elevated temperature before or after the ion exchange treatment of a commercial sodium-magnesium aluminosilicate glass. Compression of the samples prior to ion exchange leads to a decreased Na(+)-K(+) interdiffusivity, increased compressive stress, and slightly increased hardness. Compression after the ion exchange treatment changes the shape of the potassium-sodium diffusion profiles and significantly increases glass hardness. We discuss these results in terms of the underlying structural changes in network-modifier environments and overall network densification.
Optimal design of the gerotor (2-ellipses) for reducing maximum contact stress
Kwak, Hyo Seo; Li, Sheng Huan [Dept. of Mechanical Convergence Technology, Pusan National University, Busan (Korea, Republic of); Kim, Chul [School of Mechanical Design and Manufacturing, Busan Institute of Science and Technology, Busan (Korea, Republic of)
2016-12-15
The oil pump, which is used as lubricator of engines and auto transmission, supplies working oil to the rotating elements to prevent wear. The gerotor pump is used widely in the automobile industry. When wear occurs due to contact between an inner rotor and an outer rotor, the efficiency of the gerotor pump decreases rapidly, and elastic deformation from the contacts also causes vibration and noise. This paper reports the optimal design of a gerotor with a 2-ellipses combined lobe shape that reduces the maximum contact stress. An automatic program was developed to calculate Hertzian contact stress of the gerotor using the Matlab and the effect of the design parameter on the maximum contact stress was analyzed. In addition, the method of theoretical analysis for obtaining the contact stress was verified by performing the fluid-structural coupled analysis using the commercial software, Ansys, considering both the driving force of the inner rotor and the fluid pressure, which is generated by working oil.
Zou, Dujian; Liu, Tiejun; Yang, Antai; Zhao, Yanru; Du, Chengcheng
2017-10-01
The reliability of piezoceramic based smart aggregate (SA) used for damage detection of concrete structures has already been validated by laboratory tests. However, the in situ concrete members are generally under a big range of stress levels, and the performance of SA under various compressive stresses is still unclear. In this study, an electronic universal testing machine was employed to apply different stresses on the SAs. The received signals of SA sensor accompanying with different drive signals were recorded. The experimental results show that the amplitude of received signals increases firstly, and then tends to be stable with stress. This enhancement is mainly induced by the decrease in thickness of epoxy resin layer caused by compressive stress. It indicates that the change of load applied on monitored concrete members embedded with SAs may lead to a change in monitoring signal amplitude even in elastic range, but it does not stand for the change of health state of monitored concrete member.
Compressive Strength of Hydrostatic-Stress-Sensitive Materials at High Strain-Rates
LI Q M; LU Y B
2008-01-01
Many engineering materials demonstrate dynamic enhancement of their compressive strength with the increase of strain-rate.which have been included in material models to improve the reliability of numerical Simulations of the material and structural responses Under impact and biasl tcads,The strain-rate effects on the dynamic Compressive strength of a range of engineering materials which behave in hydrostatic-stress-sensitive manner were investigated.It is concluded that the dynamic enhancement of the compressive strength of a hydrostatic-stress-sensitive material may include inertia-induced lateral confinement effects,which,as a non-strain-rate factor,may greatly enhance the compressive strength of these materials.Some empirical formulae based on the dynamic stress-strain measurements over-predict the strain-rate effects on the compressive strength of these hydrostatic-stress-sensitive materials,and thus may over-estimate the structural resistance to impact and blast lgads.leading fo non-conservative design of protective structures.
A MIXED MODE FRACTURE CRITERION BASED ON THE MAXIMUM TANGENTIAL STRESS IN BRITTLE INCLUSION
Ji Changjiang; Li Zhonghua; Sun Jun
2005-01-01
A closed-form solution for predicting the tangential stress of an inclusion located in mixed mode Ⅰ and Ⅱ crack tip field was developed based on the Eshelby equivalent inclusion theory. Then a mixed mode fracture criterion, including the fracture direction and the critical load, was established based on the maximum tangential stress in the inclusion for brittle inclusioninduced fracture materials. The proposed fracture criterion is a function of the inclusion fracture stress, its size and volume fraction, as well as the elastic constants of the inclusion and the matrix material. The present criterion will reduce to the conventional one as the inclusion having the same elastic behavior as the matrix material. The proposed solutions are in good agreement with detailed finite element analysis and measurement.
Finite Element Analysis of the Maximum Stress at the Joints of the Transmission Tower
Itam, Zarina; Beddu, Salmia; Liyana Mohd Kamal, Nur; Bamashmos, Khaled H.
2016-03-01
Transmission towers are tall structures, usually a steel lattice tower, used to support an overhead power line. Usually, transmission towers are analyzed as frame-truss systems and the members are assumed to be pin-connected without explicitly considering the effects of joints on the tower behavior. In this research, an engineering example of joint will be analyzed with the consideration of the joint detailing to investigate how it will affect the tower analysis. A static analysis using STAAD Pro was conducted to indicate the joint with the maximum stress. This joint will then be explicitly analyzed in ANSYS using the Finite Element Method. Three approaches were used in the software which are the simple plate model, bonded contact with no bolts, and beam element bolts. Results from the joint analysis show that stress values increased with joint details consideration. This proves that joints and connections play an important role in the distribution of stress within the transmission tower.
A NOVEL METHOD FOR ESTIMATING SOIL PRECOMPRESSION STRESS FROM UNIAXIAL CONFINED COMPRESSION TESTS
Lamandé, Mathieu; Schjønning, Per; Labouriau, Rodrigo
2017-01-01
The concept of precompression stress is used for estimating soil strength of relevance to fieldtraffic. It represents the maximum stress experienced by the soil. The most recently developed fitting method to estimate precompression stress (Gompertz) is based on the assumption of an S-shape stress......-strain curve, which is not always fulfilled. A new simple numerical method was developed to estimate precompression stress from stress-strain curves, based solely on the sharp bend on the stress-strain curve partitioning the curve into an elastic and a plastic section. Our study had three objectives: (i......) Assessing the utility of the numerical method by comparison with the Gompertz method; (ii) Comparing the estimated precompression stress to the maximum preload of test samples; (iii) Determining the influence that soil type, bulk density and soil water potential have on the estimated precompression stress...
孙宗颀
2001-01-01
When a crack is subjected to shear force, crack branching usually occurs. Theoretical study shows that the crack branching under shear loading is caused by tensile stress, but not caused by shear fracture. The co-plane shear fracture could be obtained if compressive stress with given direction is applied to the specimen, subsequently, calculated shear fracture toughness, KⅡ C, is larger than KⅠ C. A prerequisite of possible occurrence of mode Ⅱ fracture was proposed. The study of shear fracture shows that the maximum circumferential stress theory considered its criterion as a parametric equation of a curve in KⅠ, KⅡ plane is incorrect; the predicted ratio KⅡ C/KⅠ C=0.866 is incorrect too.
Gopinath, Abhay; Lim, Andre; Nagarajan, Balasubramanian; Cher Wong, Chow; Maiti, Rajarshi; Castagne, Sylvie
2016-11-01
Mechanical surface treatments such as Shot Peening (SP) and Deep Cold Rolling (DCR) are being used to introduce Compressive Residual Stress (CRS) at the surface and subsurface layers of aerospace components, respectively. This paper investigates the feasibility of a combined introduction of both the surface and sub-surface compressive residual stress on Ti6Al4V material through a successive application of the two aforementioned processes, one after the other. CRS profiles between individual processes were compared to that of combination of processes to validate the feasibility. It was found out that shot peening introduces surface compressive residual stress into the already deep cold rolled sample, resulting in both surface and sub-surface compressive residual stresses in the material. However the drawback of such a combination would be the increased surface roughness after shot peening a deep cold rolled sample which can be critical especially in compressor components. Hence, a new technology, Vibro-Peening (VP) may be used as an alternative to SP to introduce surface stress at reduced roughness.
STUDY ON STRESS-STRAIN PROPERTIES OF REACTIVE POWDER CONCRETE UNDER UNIAXIAL COMPRESSION
M.V.SESHAGIRI RAO
2010-11-01
Full Text Available Reactive Powder Concrete(RPC which is a new type of improved high strength concrete, is a recent development in concrete technology. Because the material is intrinsically strong in compression, the stress-strain behaviour of RPC under compression is of considerable interest in the design of RPC members and accurate prediction of their structural behaviour. An attempt has been made in the present study to determine the complete stress-strain curves from uniaxial compression tests. The effect of material composition on the stressstrain behaviour and the compression toughness are presented in the paper. The highest cylinder compressive strength of 171.3 MPa and elastic modulus of 44.8 GPa were recorded for 2% 13 mm Fibres. The optimum Fibre content was found to be 3% of 6mm or 2% of 13 mm. A new measure of compression toughness known as MTI (modified toughness index is proposed and it is found to range from 2.64 to 4.65 for RPC mixes.
Compression Stress Effect on Dislocations Movement and Crack propagation in Cubic Crystal
Suprijadi,; Yusfi, Meiqorry
2012-01-01
Fracture material is seriously problem in daily life, and it has connection with mechanical properties itself. The mechanical properties is belief depend on dislocation movement and crack propagation in the crystal. Information about this is very important to characterize the material. In FCC crystal structure the competition between crack propagation and dislocation wake is very interesting, in a ductile material like copper (Cu) dislocation can be seen in room temperature, but in a brittle material like Si only cracks can be seen observed. Different techniques were applied to material to study the mechanical properties, in this study we did compression test in one direction. Combination of simulation and experimental on cubic material are reported in this paper. We found that the deflection of crack direction in Si caused by vacancy of lattice,while compression stress on Cu cause the atoms displacement in one direction. Some evidence of dislocation wake in Si crystal under compression stress at high tempera...
Computational turbulent stress closure for large-eddy simulation of compressible flow
van der Bos, F.; Geurts, Bernardus J.
2006-01-01
This paper studies the computation of stress tensors for turbulent compressible flow for purposes of subgrid modeling for LES (large eddy simulation) methods in an effort to provide a model closure. The method uses and compares a variety of filters and special decomposition methods on the velocity
Design Credit for Compressive Residual Stresses in Turbine Engine Components
2005-03-01
Laser shock processing (LSP) and low plasticity burnishing (LPB) provide impressive fatigue and damage tolerance improvement by introducing deep or...edges to mitigate FOD and fan blade dovetail surfaces to mitigate fretting damage. Keywords: design credit, fatigue, low plasticity burnishing ...As a simple example, consider a plate containing a central hole loaded in tension with some superimposed vibratory stresses, at R = 0.7. The
Damage and Plastic Deformation Modeling of Beishan Granite Under Compressive Stress Conditions
Chen, L.; Wang, C. P.; Liu, J. F.; Liu, J.; Wang, J.; Jia, Y.; Shao, J. F.
2015-07-01
Based on experimental investigations, we propose a coupled elastoplastic damage model to simulate the mechanical behavior of granite under compressive stress conditions. The granite is taken from the Beishan area, a preferable region for China's high-level radioactive waste repository. Using a 3D acoustic emission monitoring system in mechanical tests, we focus on the cracking process and its influence on the macroscopic mechanical behavior of the granite samples. It is verified that the crack propagation coupled with fractional sliding along the cracks is the principal mechanism controlling the failure process and nonlinear mechanical behavior of granite under compressive stress conditions. Based on this understanding, the coupled elastoplastic damage model is formulated in the framework of the thermodynamics theory. In the model, the coupling between damage and plastic deformation is simulated by introducing the independent damage variable in the plastic yield surface. As a preliminary validation of the model, a series of numerical simulations are performed for compressive tests conducted under different confining pressures. Comparisons between the numerical and simulated results show that the proposed model can reproduce the main features of the mechanical behavior of Beishan granite, particularly the damage evolution under compressive stress conditions.
Stress-Strain Compression of AA6082-T6 Aluminum Alloy at Room Temperature
Alexandre da Silva Scari
2014-01-01
Full Text Available Short cylindrical specimens made of AA6082-T6 aluminum alloy were studied experimentally (compression tests, analytically (normalized Cockcroft-Latham criteria—nCL, and numerically (finite element analysis—FEA. The mechanical properties were determined with the stress-strain curves by the Hollomon equation. The elastic modulus obtained experimentally differs from the real value, as expected, and it is also explained. Finite element (FE analysis was carried out with satisfactory correlation to the experimental results, as it differs about 1,5% from the damage analysis by the nCL concerning the experimental data obtained by compression tests.
Relationship between streaming potential and compressive stress in bovine intervertebral tissue.
Fujisaki, Kazuhiro; Tadano, Shigeru; Asano, Nozomu
2011-09-02
The intervertebral disc is formed by the nucleus pulposus (NP) and annulus fibrosus (AF), and intervertebral tissue contains a large amount of negatively charged proteoglycan. When this tissue becomes deformed, a streaming potential is induced by liquid flow with positive ions. The anisotropic property of the AF tissue is caused by the structural anisotropy of the solid phase and the liquid phase flowing into the tissue with the streaming potential. This study investigated the relationship between the streaming potential and applied stress in bovine intervertebral tissue while focusing on the anisotropy and loading location. Column-shaped specimens, 5.5 mm in diameter and 3 mm thick, were prepared from the tissue of the AF, NP and the annulus-nucleus transition region (AN). The loading direction of each specimen was oriented in the spinal axial direction, as well as in the circumferential and radial directions of the spine considering the anisotropic properties of the AF tissue. The streaming potential changed linearly with stress in all specimens. The linear coefficients k(e) of the relationship between stress and streaming potential depended on the extracted positions. These coefficients were not affected by the anisotropy of the AF tissue. In addition, these coefficients were lower in AF than in NP specimens. Except in the NP specimen, the k(e) values were higher under faster compression rate conditions. In cyclic compression loading the streaming potential changed linearly with compressive stress, regardless of differences in the tissue and load frequency.
Christopher Chukwutoo Ihueze
2017-01-01
Full Text Available This article employed the Hertz contact stress theory and the finite element method to evaluate the maximum contact pressure and the limit stresses of orange fruit under transportation and storage. The elastic properties of orange fruits subjected to axial and axial contact were measured such that elastic limit force, elastic modulus, Poisson’s ratio and bioyield stress were obtained as 18 N, 0.691 MPa, 0.367, 0.009 MPa for axial compression and for radial loading were 15.69 N, 0.645 MPa, 0.123, 0.010 MPa. The Hertz maximum contact pressure was estimated for axial and radial contacts as 0.036 MPa. The estimated limiting yield stress estimated as von Mises stresses for the induced surface stresses of the orange topologies varied from 0.005 MPa–0.03 MPa. Based on the distortion energy theory (DET the yield strength of orange fruit is recommended as 0.03 MPa while based on the maximum shear stress theory (MSST is 0.01 MPa for the design of orange transportation and storage system.
Mingxing Zhou
2016-05-01
Full Text Available In this study, thermal simulation experiments under different austenitization temperatures and different stress states were conducted. High-temperature laser scanning confocal microscopy (LSCM, thermal dilatometry, and scanning electron microscope (SEM were used to quantitatively investigate the effects of the uniaxial compressive stress on bainitic transformation at 330 °C following different austenitization temperatures. The transformation plasticity was also analyzed. It was found that the promotion degree of stress on bainitic transformation increases with the austenitization temperature due to larger prior austenite grain size as well as stronger promoting effect of mechanical driving force on selected variant growth at higher austenitization temperatures. The grain size and the yield strength of prior austenite are other important factors which influence the promotion degree of stress on bainitic transformation, besides the mechanical driving force provided by the stress. Moreover, the transformation plasticity increases with the austenitization temperature.
Hui Zhang
2014-05-01
Full Text Available In this paper, we have investigated the dependence of both the electromechanical effect and the electrostriction on the compressive stress in PMN-30%PT single crystal on the basis of single domain polarization rotation model. In the model, the electroelastic energy induced by the compressive stress is taken into account. The results have demonstrated that the compressive stress can lead to a significant change in the initial polarization state in the crystal. The reason lies in the stress induced anisotropy which is the coupling between the compressive stress and the electrostrictive coefficients. Thus, the initial polarization state in single crystal is determined by the combination of both electrocrystalline anisotropy and the stress induced anisotropy. The compressive stress along the [100] axis can make the polarization in the crystal be perpendicular to the stress direction, and make it difficult to be polarized to the saturation. This model is useful for better understanding both the polarization rotation and electromechanical effect in ferroelectric crystals with the compressive stress present.
Dielectric and Ferroelectric Properties of Complex Perovskite Ceramics Under Compressive Stress
无
2007-01-01
Dielectric and ferroelectric properties of complex perovskite PZT-PZN ceramic system were investigated under the influence of the compressive stress. The results showed that the dielectric properties, i.e. dielectric constant ( εr ) and dielectric loss ( tan δ), and the ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis loops, the saturation polarization ( P(sat) ), and the remnant polarization (Pr) changed significantly with increasing compressive stress. These changes depended strongly on the ceramic compositions. The experimental results on the dielectric properties could be explained by both intrinsic and extrinsic domain-related mechanisms involving domain wall motions, as well as the de-aging phenomenon. The stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes were responsible for the changes observed in the ferroelectric parameters. In addition,a significant decrease in those parameters after a cycle of stress was observed and attributed to the stress induced decrease in switchable part of spontaneous polarization. This study clearly show that the applied stress had significant influence on the electrical properties of complex perovskite ceramics.
Fatigue life prediction method for contact wire using maximum local stress
Kim, Yong Seok; Haochuang, Li; Seok, Chang Sung; Koo, Jae Mean [Sungkyunkwan University, Suwon (Korea, Republic of); Lee, Ki Won; Kwon, Sam Young; Cho, Yong Hyeon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)
2015-01-15
Railway contact wires supplying electricity to trains are exposed to repeated mechanical strain and stress caused by their own weight and discontinuous contact with a pantograph during train operation. Since the speed of railway transportation has increased continuously, railway industries have recently reported a number of contact wire failures caused by mechanical fatigue fractures instead of normal wear, which has been a more common failure mechanism. To secure the safety and durability of contact wires in environments with increased train speeds, a bending fatigue test on contact wire has been performed. The test equipment is too complicated to evaluate the fatigue characteristics of contact wire. Thus, the axial tension fatigue test was performed for a standard specimen, and the bending fatigue life for the contact wire structure was then predicted using the maximum local stress occurring at the top of the contact wire. Lastly, the tested bending fatigue life of the structure was compared with the fatigue life predicted by the axial tension fatigue test for verification.
Gonzalez, L.G. [Departamento de Electronica y Comunicaciones, Universidad de los Andes, nucleo la Hechicera, 5101 Merida (Venezuela); Figueres, E.; Garcera, G. [Grupo de Sistemas Electronicos Industriales, Universidad Politecnica de Valencia, Camino de vera s/n, 46022 Valencia (Spain); Carranza, O. [Escuela Superior de Computo, Instituto Politecnico Nacional, Av. Juan de Dios Batiz s/n, 07738 DF (Mexico)
2010-07-15
This paper presents an improved maximum-power-point tracking algorithm for wind-energy-conversion-systems. The proposed method significantly reduces the turbine mechanical stress with regard to conventional techniques, so that both the maintenance needs and the medium time between failures are expected to be improved. To achieve these objectives, a sensorless speed control loop receives its reference signal from a modified Perturb and Observe algorithm, in which the typical steps on the reference speed have been substituted by a fixed and well-defined slope ramp signal. As a result, it is achieved a soft dynamic response of both the torque and the speed of the wind turbine, so that the whole system suffers from a lower mechanical stress than with conventional P and O techniques. The proposed method has been applied to a wind turbine based on a permanent magnet synchronous generator operating at variable speed, which is connected to the distribution grid by means of a back to back converter. (author)
Li Xuejun; Qiu Weiliang; Yuan Yincai; Li Ping
2006-01-01
The relation between the maximum contact stress ratio and deflection angle is derived from Hertz contact theory when the deflection of rotary kiln supporting wheel happens. According to the analysis of practical example, the maximum contact stress ratio within the deflection range of rotary kiln supporting wheel is listed. The contact stress will increase largely when rotary kiln supporting wheel deflects with little angle,which probably will result in accidents correlating to safety. This will provide theory conference for the design,the operating condition analysis and adjusting of the rotary kiln.
CO2 laser scribe of chemically strengthened glass with high surface compressive stress
Li, Xinghua; Vaddi, Butchi R.
2011-03-01
Chemically strengthened glass is finding increasing use in handheld, IT and TV cover glass applications. Chemically strengthened glass, particularly with high (>600MPa) compressive stress (CS) and deeper depth of layer (DOL), enable to retain higher strength after damage than non-strengthened glass when its surface is abraded. Corning Gorilla® Glass has particularly proven to be advantageous over competition in this attribute. However, due to high compressive stress (CS) and Central Tension (CT) cutting ion-exchanged glass is extremely difficult and often unmanageable where ever the applications require dicing the chemically strengthened mother glass into smaller parts. We at Corning have developed a CO2 laser scribe and break method (LSB) to separate a single chemically strengthened glass sheet into plurality of devices. Furthermore, CO2 laser scribe and break method enables debris-free separation of glass with high edge strength due to its mirror-like edge finish. We have investigated laser scribe and break of chemically strengthened glass with surface compressive stress greater than 600 MPa. In this paper we present the results of CO2 scribe and break method and underlying laser scribing mechanisms. We demonstrated cross-scribe repetitively on GEN 2 size chemically strengthened glass substrates. Specimens for edge strength measurements of different thickness and CS/DOL glass were prepared using the laser scribe and break technique. The specimens were tested using the standard 4-point bend method and the results are presented.
Hong-Bao Zhao
2014-01-01
Full Text Available Taking the standard size coal block samples defined by ISRM as research objects, both properties of methane diffusion of coal block under triaxial compressive stress and characteristic influences caused by methane pressure were systematically studied with thermo-fluid-solid coupling with triaxial servocontrolled seepage equipment of methane-containing coal. The result shows the methane diffusion property of coal block under triaxial compressive stress was shown in four-stage as follow, first is sharply reduce stage, second is hyperbolic reduce stage, third is close to a fixed value stage, fourth stage is 0. There is a special point making the reduced rate of characteristic curve of methane diffusion speed become sharply small; the influences of shape of methane diffusion speed characteristic curve caused by methane pressure are not obvious, which only is shown in numerical size of methane diffusion speed. Test time was extended required by appear of the special point makes the reduce rate of methane diffusion speed become sharply small. The fitting four-phase relation of methane diffusion of coal block under triaxial compressive stress was obtained, and the idea is proposed that influences of the fitting four-phase relation caused by methane pressure were only shown in value of fitting parameters.
Reduction of the residual stresses in cold expanded thick-walled cylinders by plastic compression
V.F. SKVORTSOV; A.O. BOZNAK; A.B. KIM; A. Yu ARLYAPOV; A.I. DMITRIEV
2016-01-01
We suppose that in order to maintain high accuracy of holes and to lower residual stresses after cold expansion of thick-walled cylinders, which undergo cross-section plastic deformation, it is necessary to perform axial plastic compression and subsequent cold expansion with small interferences. To test this hypothesis, we studied hoop, radial and axial residual stresses in cylinders made of carbon steel AISI 1050 with hole diameter of 5 mm, outer diameter of 15 mm and length of 30 mm by Sachs method as well as accuracy of expanded holes. It is found that double cold expansion with total interference equal to 5.1%generates hoop residual stresses with largest absolute value equal to 284 MPa and ensures high holes accuracy (IT7). After plastic compression with strain equal to 0.5 and 1%the mentioned stresses reduced to 120 and 75 MPa respectively, and accuracy of the holes reduced as well. Subsequent cold expansion with small interference equal to 0.9%helps to restore holes accuracy (IT7) gained by double cold expansion and ensure that absolute value of hoop residual stresses (177 MPa) is lower compared to double cold expansion.
无
2006-01-01
Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stress- strain curves of quasibrittle geomaterial (such as rock and concrete) in uniaxial tension, direct shear and uniaxial compression were presented, respectively. The three derived stress- strain curves were generalized as a unified formula. Beyond the onset of strain localization, a linear strain-softening constitutive relation for localized band was assigned. The size of the band was controlled by internal or characteristic length according to gradient-dependent plasticity. Elastic strain within the entire specimen was assumed to be uniform and decreased with the increase of plastic strain in localized band. Total strain of the specimen was decomposed into elastic and plastic parts. Plastic strain of the specimen was the average value of plastic strains in localized band over the entire specimen. For different heights, the predicted softening branches of the relative stress - strain curves in uniaxial compression are consistent with the previously experimental results for normal concrete specimens. The present expressions for the post-peak stress - deformation curves in uniaxial tension and direct shear agree with the previously numerical results based on gradient-dependent plasticity.
Flow Stress Behavior and Processing Map of Al-Cu-Mg-Ag Alloy during Hot Compression
YANG Sheng; YI Danqing; ZHANG Hong; YAO Sujuan
2008-01-01
The hot deformation behavior of Al-Cu-Mg-Ag was studied by isothermal hot compression tests in the temperature range of 573-773 K and strain rate range of 0.001-1 s-1 on a Gleeble 1500 D thermal mechanical simulator. The results show the flow stress of Al-Cu-Mg-Ag alloy increases with strain rate and decreases after a peak value, indicating dynamic recovery and recrystallization. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate and temperature, the flow stress equation is estimated to illustrate the relation of strain rate and stress and temperature during high temperature deformation process. The processing maps exhibit two domains as optimum fields for hot deformation at different strains, including the high strain rate domain in 623-773 K and the low strain rate domain in 573-673 K.
Flow stress and tribology size effects in scaled down cylinder compression
GUO Bin; GONG Feng; WANG Chun-ju; SHAN De-bin
2009-01-01
Microforming is an effective method to manufacture small metal parts. However, macro forming can not be transferred to microforming directly because of size effects. Flow stress and tribology size effects were studied. Scaled down copper T2 cylinder compression was carried out with the lubrication of castor oil and without lubrication. The results show that the flow stress decreases with decreasing the initial specimen diameter in both lubrication conditions, and the flow stress decreases by 30 MPa with the initial specimen diameter decreasing from 8 mm to 1 mm. The friction factor increases obviously with decreasing the initial specimen diameter in the case of lubricating with castor oil, and the friction factor increases by 0.11 with the initial specimen diameter decreasing from 8mm to 1mm. However, the tribology size effect is not found in the case without lubrication. The reasons of the flow stress and tribology size effects were also discussed.
Sutor, A.K.; Huguet, P.; Le, T.S.; Deabate, S. [Institut Europeen des Membranes, UMR 5635, ENSCM, UM2, CNRS, Universite de Montpellier II, CC047, Montpellier (France); Morin, A. [Laboratoire des Composants pour Pile a Combustible, Electrolyseur et Modelisation, CEA Grenoble/DRT/Liten/DEHT/LCPEM, Grenoble (France); Gebel, G. [SPrAM, UMR 5819 CEA/CNRS/UJF-Grenoble 1, INAC, Grenoble (France)
2012-04-15
The effect of compressive stress on the local water content of Nafion NRE 212 and Aquivion E79 membranes is studied by confocal {mu}-Raman spectroscopy using a specific tightening device. This device aims to mimic the geometry of the bipolar plate flow field of actual fuel cells, i.e. the sequence of channels and ribs. The membrane water content decreases with increasing stress, under the ribs as well as in the channel. The higher the initial water content, the larger the water content decreases with mechanical stress. The extent of water loss depends on the position of the membrane in the device, the applied stress and the hydration history of the membrane. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Gabb, Timothy P.; Danetti, Andrew; Draper, Susan L.; Locci, Ivan E.; Telesman, Jack
2016-01-01
The fatigue lives of disk superalloys can be increased by shot peening their surfaces, to induce compressive residual stresses near the surface that impede cracking there. As disk application temperatures increase for improved efficiency, the persistence of these beneficial stresses could be impaired, especially with continued fatigue cycling. The objective of this work was to study the retention of residual stresses introduced by shot peening, when subjected to fatigue and high temperatures. Fatigue specimens of powder metallurgy processed nickel-base disk superalloy ME3 were prepared with consistent processing and heat treatment. They were then shot peened using varied conditions. Strain-controlled fatigue cycles were run at room temperature and 704 C, to allow re-assessment of residual stresses.
Effect of Compressive Stresses on Leakage Currents in Microchip Tantalum Capacitors
Teverovsky, Alexander
2012-01-01
Microchip tantalum capacitors are manufactured using new technologies that allow for production of small size capacitors (down to EIA case size 0402) with volumetric efficiency much greater than for regular chip capacitors. Due to a small size of the parts and leadless design they might be more sensitive to mechanical stresses that develop after soldering onto printed wiring boards (PWB) compared to standard chip capacitors. In this work, the effect of compressive stresses on leakage currents in capacitors has been investigated in the range of stresses up to 200 MPa. Significant, up to three orders of magnitude, variations of currents were observed after the stress exceeds a certain critical level that varied from 10 MPa to 180 MPa for capacitors used in this study. A stress-induced generation of electron traps in tantalum pentoxide dielectric is suggested to explain reversible variations of leakage currents in tantalum capacitors. Thermo-mechanical characteristics of microchip capacitors have been studied to estimate the level of stresses caused by assembly onto PWB and assess the risk of stress-related degradation and failures. Keywords: tantalum capacitors, leakage current, soldering, reliability, mechanical stress.
Sung Woo Park
2015-03-01
Full Text Available The safety of a multi-span waler beam subjected simultaneously to a distributed load and deflections at its supports can be secured by limiting the maximum stress of the beam to a specific value to prevent the beam from reaching a limit state for failure or collapse. Despite the fact that the vast majority of accidents on construction sites occur at waler beams in retaining wall systems, no safety monitoring model that can consider deflections at the supports of the beam is available. In this paper, a maximum stress estimation model for a waler beam based on average strains measured from vibrating wire strain gauges (VWSGs, the most frequently used sensors in construction field, is presented. The model is derived by defining the relationship between the maximum stress and the average strains measured from VWSGs. In addition to the maximum stress, support reactions, deflections at supports, and the magnitudes of distributed loads for the beam structure can be identified by the estimation model using the average strains. Using simulation tests on two multi-span beams, the performance of the model is evaluated by estimating maximum stress, deflections at supports, support reactions, and the magnitudes of distributed loads.
PEREIRA ADRIANA VARGAS
2000-01-01
Full Text Available The objective of this work was to study the fruit compression behavior aiming to develop new tomato packages. Deformations caused by compression forces were observed inside packages and in individual 'Santa Clara' tomato fruit. The forces applied by a transparent acrylic lever to the fruit surface caused pericarp deformation and the flattened area was proportional to the force magnitude. The deformation was associated to the reduction in the gas volume (Vg, caused by expulsion of the air from the loculus cavity and reduction in the intercellular air volume of the pericarp. As ripening advanced, smaller fractions of the Vg reduced by the compressive force were restored after the stress was relieved. The lack of complete Vg restoration was an indication of permanent plastic deformations of the stressed cells. Vg regeneration (elastic recovery was larger in green fruits than in the red ones. The ratio between the applied force and the flattened area (flattening pressure, which depends on cell turgidity, decreased during ripening. Fruit movements associated with its depth in the container were observed during storage in a transparent glass container (495 x 355 x 220 mm. The downward movement of the fruits was larger in the top layers because these movements seem to be driven by a summation of the deformation of many fruits in all layers.
The compression stress-strain behavior of Sn-Ag-Cu solder
Vianco, Paul T.; Rejent, Jerome A.; Martin, Joseph J.
2003-06-01
The yield-stress behavior was investigated for the 95.5Sn-4.3Ag-0.2Cu (wt.%), 95.5Sn-3.9Ag-0.6Cu, and 95.5Sn-3.8Ag-0.7Cu ternary lead-free solders using the compression stress-strain test technique. Cylindrical specimens were evaluated in the as-cast or aged (125°C, 24 h) condition. The tests were performed at -25°C, 25°C, 75°C, 125°C, and 160°C using strain rates of 4.2×10-5s-1 or 8.3×10-4s-1. Specially designed Sn-Ag-0.6Cu samples were fabricated to compare the yield stress of the dendritic microstructure versus that of the equiaxed microstructure that occurs in this alloy.
Suresh Mitthra
2017-01-01
Full Text Available Background: Understanding the mechanical properties is important in predicting the clinical behavior of composites. Finite element analysis (FEA evaluates properties of materials replicating clinical scenario. Aim: This study evaluated polymerization shrinkage and stress, wear resistance (WR, and compressive strength (CS of silorane in comparison with two methacrylate resins. Settings and Design: This study design was a numerical study using FEA. Materials and Methods: Three-dimensional (3D models of maxillary premolar with Class I cavities (2 mm depth, 4 mm length, and 2.5 mm width created and restored with silorane, nanohybrid, and microhybrid; Groups I, II, and III, respectively. Loads of 200–600 N were applied. Polymerization shrinkage was first determined by displacement produced in the X, Y, and Z planes. Maximum stress distribution due to shrinkage was calculated using AN SYS software. 3D cube models of composite resins were simulated with varying filler particle size. Similar loads were applied. WR and compressive stress were calculated: K W L/H and load/cross-sectional area, respectively. Statistical analysis done using one-way ANOVA, Kruskal–Wallis, and Tukey's honestly significant difference test (P < 0.05. Results: Polymerization shrinkage (0.99% and shrinkage stress (233.21 Mpa of silorane were less compared to microhybrid (2.14% and 472.43 Mpa and nanohybrid (2.32% and 464.88 Mpa. Silorane (7.92×/1011 μm/mm3 and nanohybrid (7.79×/1011 showed superior WR than microhybrid (1.113×/1017. There was no significant difference in compressive stress among the groups. Conclusion: Silorane exhibited less polymerization shrinkage and shrinkage stress compared to methacrylates. Silorane and nanohybrid showed greater WR compared to microhybrid. CS of all groups was similar.
Buckling of un—stiffened cylindrical shell under non—uniform axial compressive stress
宋昌永
2002-01-01
This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses.Only the more important and interesting aspects of the research,judged from a personal viewpoint,are discussed.They can be crudely classified into four categories:(1) shells subjected to non-uniform loads;(2) shells on discrete supports;(3) shells with intended cutouts/holes;and (4) shells with non-uniform settlements.
Huang Yifan
2016-12-01
Full Text Available Three-dimensional (3D finite element analyses (FEA are performed to simulate the local compression (LC technique on the clamped single-edge notched tension (SE(T specimens. The analysis includes three types of indenters, which are single pair of cylinder indenters (SPCI, double pairs of cylinder indenters (DPCI and single pair of ring indenters (SPRI. The distribution of the residual stress in the crack opening direction in the uncracked ligament of the specimen is evaluated. The outcome of this study can facilitate the use of LC technique on SE(T specimens.
Limonov, V.A.; Razin, A.F.; Mikel`sons, M.Ya. [Central Research Institute of Special Engineering, Moscow (Russian Federation)
1992-11-01
Under real operating conditions, assemblies and products made of composites are subjected to combined static and cyclic loads. At the planning stage, an important problem is the selection of the materials to be used and an estimate of the load-bearing capacity by complex investigation of their physicomechanical properties. In the present work, the authors studied experimentally the characteristics of strength under static uniaxial and combined loading and the effect of static shear stresses on the compressive fatigue limit of glass-fabric reinforced plastic. 7 refs., 7 figs., 2 tabs.
Strijker, G.; Beekman, F.; Bertotti, G.; Luthi, S.M.
2013-01-01
Stress distributions and deformation patterns in a medium with a pre-existing fracture set are analyzed as a function of the remote compressive stress orientation (σH) using finite element models with increasingly complex fracture configurations. Slip along the fractures causes deformation localizat
Strijker, G.; Beekman, F.; Bertotti, G.; Luthi, S.M.
2013-01-01
Stress distributions and deformation patterns in a medium with a pre-existing fracture set are analyzed as a function of the remote compressive stress orientation (σH) using finite element models with increasingly complex fracture configurations. Slip along the fractures causes deformation
Vasile Cojocaru
2016-12-01
Full Text Available Several methods can be used in the FEM studies to apply the loads on a plain bearing. The paper presents a comparative analysis of maximum stress obtained for three loading scenarios: resultant force applied on the shaft – bearing assembly, variable pressure with sinusoidal distribution applied on the bearing surface, variable pressure with parabolic distribution applied on the bearing surface.
Ma, Zhong-fei; Yu, Qi-xiang [Jiangsu University, Zhenjiang (China). Center of Safety Engineering
2007-01-15
Based on the conditions of coal and gas outburst, the action mechanism for preventing coal and gas compression disseminated values outburst with stress pre-released hydraulically was analyzed. The accuracy of this mechanism was validated by measuring the gas emission before and after pre-releasing stress hydraulically, measuring the rupture failure by the electromagnetic radiation technique and the correlative practical datum. The results show that the electromagnetic radiation intensity and pulse count are increscent when taking the measure of stress pre-released hydraulically, which is propitious to prevent the coal and gas outburst. The action mechanism consists of three aspects: 1) Pre-releasing gas and increasing tangential stress and disseminated values friction resistance; 2) Pre-releaseing the radial effective geostress on high-tension side and reducing the radial stress difference of disseminated values chop motion for enhancing coal displacement; 3) Making the disseminated values and adjacent coal and rock felting by flooding water and increasing the disseminated values' friction resistance coefficients. 9 refs., 2 figs.
Modeling of Flow Stress of High Titanium Content 6061 Aluminum Alloy Under Hot Compression
Chen, Wei; Guan, Yingping; Wang, Zhenhua
2016-09-01
Hot compression tests were performed on high titanium content 6061 aluminum alloy (AA 6061-Ti) using a Gleeble-3500 thermomechanical testing system at temperatures from 350 to 510 °C with a constant strain rate in the range of 0.001-10 s-1. Three types of flow stress models were established from the experimental stress-strain curves, the correlation coefficient ( R), mean absolute relative error ( MARE), and root mean square deviation ( RMSD) between the predicted data and the experimental data were also calculated. The results show that the Fields-Backofen model, which includes a softening factor, was the simplest mathematical expression with a level of precision appropriate for the numerical simulations. However, the Arrhenius and artificial neural network (ANN) models were also consistent with the experimental results but they are more limited in their application in terms of their accuracy and the mathematical expression of the models.
Ándonios D. Tsolakis
2011-01-01
Full Text Available Problem statement: Main purpose of this study was to investigation toothed gear loading problems using the Finite Element Method. Approach: We used Niemann's equations to compare maximum bending stress which was developed at critical gear-tooth flank point during gear meshing, applied for three distinct spur-gear sizes, each having different teeth number, module and power rating. Results: The results emerging after the application of Niemann's equations were compared to the results derived by application of the Finite Element Method (FEM for the same gear-loading input data. Results are quite satisfactory, since von Mises' equivalent stresses calculated with FEM are of the same order with the results of classical analytical method. Conclusion: Judging from the emerging results, deviation of the two methods, analytical (Niemann's equations and computational (FEM, referring to maximum bending stress is fairly slight, independently of the applied geometrical and loading data of each gear.
GAO Yuan; WU Jing
2008-01-01
The rocks in the crust are pervaded by stress-aligned fluid-saturated microcracks, and the complex fault tectonics and stress control the configuration of the microcracks, however shear-wave splitting could indicate this kind of characteristics. In this paper, Capital Area Seismograph Network (CASN), the widest scope and highest density of regional seismograph network presently in China, is adopted to deduce the principal compressive stress field distribution pattern from polarizations of fast shear-waves, based on shear-wave splitting analysis. The principal compressive stress in capital area of China is at NE85.7°±41.0° in this study. Compared with the results of principal compressive stress field in North China obtained from other methods, the results in this study are reliable in the principal com-pressive stress field distribution in capital area. The results show that it is an effective way, although it is the first time to directly obtain crustal stress field from seismic anisotropy. It is effectively applied to the zones with dense seismograph stations.
Blackwood, R.L.
1980-05-15
There are now available sufficient data from in-situ, pre-mining stress measurements to allow a first attempt at predicting the maximum stress magnitudes likely to occur in a given mining context. The sub-horizontal (lateral) stress generally dominates the stress field, becoming critical to stope stability in many cases. For cut-and-fill mining in particular, where developed fill pressures are influenced by lateral displacement of pillars or stope backs, extraction maximization planning by mathematical modelling techniques demands the best available estimate of pre-mining stresses. While field measurements are still essential for this purpose, in the present paper it is suggested that the worst stress case can be predicted for preliminary design or feasibility study purposes. In the Eurpoean continent the vertical component of pre-mining stress may be estimated by adding 2 MPa to the pressure due to overburden weight. The maximum lateral stress likely to be encountered is about 57 MPa at depths of some 800m to 1000m below the surface.
Bardella, Lorenzo; Belleri, Andrea
2011-08-01
We report the results of uniaxial compressive tests on a DGEBA epoxy resin at room temperature, well below its glass transition. We first focus on the strength, defined as the stress value corresponding to either a maximum or a flattening of the stress-strain curve, which, for this polymer, may be taken to be coincident with the yield stress, as often assumed for many thermosets. Within the strain rate range (1.E-6 s-1, 2.E-3 s-1) we confirm the linear trend relating the logarithm of the strain rate to the yield stress, as already been observed by other investigators even for the same epoxy resin; instead, at strain rates below dot{\\varepsilon} 0 ≈ 1.E{-}6 s^{-1}, we found a negligible rate-dependence, as our data indicate a lowest limit of the yield stress, of about 87 MPa. On the basis of these results, we propose how to extend to the viscoplastic regime of deformation a nonlinear viscoelastic model previously put forward. Secondarily, within the viscoelastic range, at a stress level significantly lower than the yield stress, our measurements show a mild volumetric instability, allowed by the free lateral expansion, not ascribable to any macroscopic structural effect; such a behaviour has never been reported in the literature, to the best of our knowledge.
Bux, Shamin; Madaree, Anil
2012-03-01
Keloids are benign tumours composed of fibrous tissue produced during excessive tissue repair triggered by minor injury, trauma or surgical incision. Although it is recognized that keloids have a propensity to form in the upper torso of the body, the predisposing factors responsible for this have not been investigated. It is crucial that the aetiopathoical factors implicated in keloid formation be established to provide guidelines for well-informed more successful treatment. We compared keloid-prone and keloid-protected skin, identified pertinent morphological differences and explored how inherent structural characteristics and intrinsic factors may promote keloid formation. It was determined that keloid prone areas were covered with high tension skin that had low stretch and a low elastic modulus when compared with skin in keloid protected areas where the skin was lax with a high elastic modulus and low pre-stress level. Factors contributing to elevated internal stress in keloid susceptible skin were the protrusion of hard connective tissue such as bony prominences or cartilage into the dermis of skin as well as inherent skin characteristics such as the bundled arrangement of collagen in the reticular dermis, the existent high tension, the low elastic modulus, low stretch ability, contractile forces exerted by wound healing fibroblastic cells and external forces. Stress promotes keloid formation by causing dermal distortion and compression which subsequently stimulate proliferation and enhanced protein synthesis in wound healing fibroblastic cells. The strain caused by stress also compresses and occludes microvessels causing ischaemic effects and reperfusion injury which stimulate growth when blood rich in growth factors returns to the tissue. The growth promoting effects of increased internal stress, primarily, and growth factors released by reperfusing blood, manifest in keloid formation. Other inherent skin characteristics promoting keloid growth during the
Residual compressive surface stress increases the bending strength of dental zirconia.
Inokoshi, Masanao; Zhang, Fei; Vanmeensel, Kim; De Munck, Jan; Minakuchi, Shunsuke; Naert, Ignace; Vleugels, Jozef; Van Meerbeek, Bart
2017-04-01
To assess the influence of surface treatment and thermal annealing on the four-point bending strength of two ground dental zirconia grades. Fully-sintered zirconia specimens (4.0×3.0×45.0mm(3)) of Y-TZP zirconia (LAVA Plus, 3M ESPE) and Y-TZP/Al2O3 zirconia (ZirTough, Kuraray Noritake) were subjected to four surface treatments: (1) 'GROUND': all surfaces were ground with a diamond-coated grinding wheel on a grinding machine; (2) 'GROUND+HEAT': (1) followed by annealing at 1100°C for 30min; (3) 'GROUND+Al2O3 SANDBLASTED': (1) followed by sandblasting using Al2O3; (4) 'GROUND+CoJet SANDBLASTED': (1) followed by tribochemical silica (CoJet) sandblasting. Micro-Raman spectroscopy was used to assess the zirconia-phase composition and potentially induced residual stress. The four-point bending strength was measured using a universal material-testing machine. Weibull analysis revealed a substantially higher Weibull modulus and slightly higher characteristic strength for ZirTough (Kuraray Noritake) than for LAVA Plus (3M ESPE). For both zirconia grades, the 'GROUND' zirconia had the lowest Weibull modulus in combination with a high characteristic strength. Sandblasting hardly changed the bending strength but substantially increased the Weibull modulus of the ground zirconia, whereas a thermal treatment increased the Weibull modulus of both zirconia grades but resulted in a significantly lower bending strength. Micro-Raman analysis revealed a higher residual compressive surface stress that correlated with an increased bending strength. Residual compressive surface stress increased the bending strength of dental zirconia. Thermal annealing substantially reduced the bending strength but increased the consistency (reliability) of 'GROUND' zirconia. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.
Mohamed N. Ghazzal; Chaoui, N.; Genet, Michel; Gaigneaux, Eric M.; Robert, D.
2011-01-01
TiO2 thin films grown on different kinds of substrates were obtained by sol–gel process. X-ray diffraction revealed that the TiO2 lattice parameter c decreased continuously, indicating a continuous variation in the compressive stress, a negligible compressive stress of the film grown onto Soda-Lime Glass (SLG), medium compressive stress of the film grown onto BoroSilicate Glass (BSG) and large compressive stress of the film deposited onto the Quartz Substrate (QS). UV–Vis absorbance spectra e...
Kallemeyn, Nicole A; Grosland, Nicole M; Pedersen, Doug R; Martin, James A; Brown, Thomas D
2006-01-01
Background: We developed a poroelastic finite element (FE) model of cartilage in dynamic triaxial compression to parametrically analyze the effects of loading and boundary conditions on a baseline model. Conventional mechanical tests on articular cartilage such as confined and unconfined compression, indentation, etc., do not fully allow for modulation of compression and shear at physiological levels whereas triaxial compression does. A Triaxial Compression Bioreactor, or TRIAX, has been developed to study chondrocyte responses to multi-axial stress conditions under cyclic loading. In the triaxial setting, however, a cartilage explant's physical testing environment departs from the ideal homogeneous stress state that would occur from strict linear superposition of the applied axial and transverse pressure. Method of Approach: An axisymmetric poroelastic FE model of a cartilage explant (4 mm diameter, 1.5 mm thick) in cyclic triaxial compression was created. Axial and transverse loads (2 MPa at 1 Hz.) were applied via a platen and containment sheath. Parameters of interest included the rise time and magnitude of the applied load, in addition to the containment sheath modulus and the friction coefficient at the cartilage/platen interfaces. Metrics of interest in addition to whole explant axial strain included axial (surface normal) stress, shear stress, pore pressure, and the fluid load carriage fraction within the explant. Results: Strain results were compared to experimental data from explants tested in the TRIAX under conditions similar to the baseline model. Explant biomechanics varied considerably over numbers of load cycles and parameter values. Cyclic loading caused an increase in accumulated strain for the various loading and boundary conditions. Conclusions: Unlike what would be expected from linear superposition of the homogeneous stresses from the applied axial and transverse pressure, we have shown that the stress state within the TRIAX is considerably
Huang, Jun; Niu, Mu Tong; Zhang, Ji Cai; Wang, Wei; wang, Jian Feng; Xu, Ke
2017-02-01
Crystalline qualities of three AlN films grown by cold-wall high temperature hydride vapor phase epitaxy (CW-HT-HVPE) on c-plane sapphire substrates, with different AlN buffer layers (BLs) deposited either by CW-HT-HVPE or by hot-wall low temperature hydride vapor phase epitaxy (HW-LT-HVPE), have been studied. The best film quality was obtained on a 500-nm-thick AlN BL grown by HW-LT-HVPE at 1000 ℃. In this case，the AlN epilayer has the lowest full-width at half-maximum (FWHM) values of the (0002) and (10-12) x-ray rocking curve peaks of 295 and 306 arcsec, respectively, corresponding to the screw and edge threading dislocation (TD) densities of 1.9×108 cm-2 and 5.2×108 cm-2. This improvement in crystal quality of the AlN film can be attributed to the high compressive-stress of BL grown by HW-LT-HVPE，which facilitate the inclination and annihilation of TDs.
Ravindranadh BOBBILI; B. RAMAKRISHNA; V. MADHU; A.K. GOGIA
2015-01-01
An artificial neural network (ANN) constitutive model and JohnsoneCook (JeC) model were developed for 7017 aluminium alloy based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments at various temperatures. A neural network configuration consists of both training and validation, which is effectively employed to predict flow stress. Temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook (JeC) model and neural network model was performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tem-peratures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB over a range of temperatures (25?e300 ?C), strains (0.05e0.3) and strain rates (1500e4500 s?1) were employed to formulate JeC model to predict the flow stress behaviour of 7017 aluminium alloy under high strain rate loading. The JeC model and the back-propagation ANN model were developed to predict the flow stress of 7017 aluminium alloy under high strain rates, and their predictability was evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the J-C model are found to be 0.8461 and 10.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. The predictions of ANN model are observed to be in consistent with the experimental data for all strain rates and temperatures.
Crack growth time dependence analysis of granite under compressive-shear stresses state
LI Jiang-teng; CAO Ping; Gu De-sheng; Wu Chao
2008-01-01
The curves of crack relative length //b and crack growth time t of granite were gained under compressive stresses state according to subcritical crack growth parameters and crack stability growth equation by double-torsion constant displacement load relaxa-tion method. The relations between crack relative length and the crack growth time were discussed under different stresses and different crack lengths. The results show that there is a turning point on curve of crack relative length //b and crack growth time of granite. The slope of curve is small when crack relative length is less than the vertical coordinate of the point, and crack grows stably in this case. Cracks grow, encounter and integrate catastro-phically when crack relative length is more than the vertical coordinate of the point, and there is not a gradual stage from crack stability growth to crack instability growth, i.e. rock mass instability is sudden. The curves of crack relative length //b and crack growth time t of granite move to right with decrease of stress σ1 or crack length a, which implies that limit time increases consequently. The results correspond to practicality.
G.S. Fu; W.Z. Chen; K.W. Qian
2005-01-01
The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treatment during plastic deformation at elevated temperature was studied by isothermal compression testusing Gleeble1500 dynamic hot-simulation testing machine. The results show that the A1 sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500℃ at strain rates within the range of 0.01-10.0s-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at elevated temperature for this material is thermally activated. Compared with the Al pieces prepared by no or conventional melt-treatment, hot deformation activation energy of Al sheets prepared by high-efficient melt-treatment is the smallest (Q = 168.0kJ/mol), which reveals that the hot working formability of this material is very better, and has directly to do with the effective improvement of its metallurgical quality.
Jiří Witzany
2016-04-01
Full Text Available The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cracks accompanied by an increase in horizontal masonry strain. During the appearance of micro and hairline cracks (10−3 to 10−1 mm, the effect of non-pre-stressed wrapping composite is very small. The favorable effect of passive wrapping is only intensively manifested after the appearance of cracks (10−1 mm and bigger at higher loading levels. In the case of “optimum” reinforcement of a masonry column, the experimental research showed an increase in vertical displacements δy (up to 247%, horizontal displacements δx (up to 742% and ultimate load-bearing capacity (up to 136% compared to the values reached in unreinforced masonry columns. In the case of masonry structures in which no intensive “bed joint filler–masonry unit” interaction occurs, e.g., in regular coursed masonry with little differences in the mechanical characteristics of masonry units and the binder, the reinforcing effect of the fabric applies only partially.
Shao, Y. F.; Song, F.; Jiang, C. P.; Xu, X. H.; Wei, J. C.; Zhou, Z. L.
2016-02-01
We study the difference in the maximum stress on a cylinder surface σmax using the measured surface heat transfer coefficient hm instead of its average value ha during quenching. In the quenching temperatures of 200, 300, 400, 500, 600 and 800°C, the maximum surface stress σmmax calculated by hm is always smaller than σamax calculated by ha, except in the case of 800°C; while the time to reach σmax calculated by hm (fmmax) is always earlier than that by ha (famax). It is inconsistent with the traditional view that σmax increases with increasing Biot number and the time to reach σmax decreases with increasing Biot number. Other temperature-dependent properties also have a small effect on the trend of their mutual ratios with quenching temperatures. Such a difference between the two maximum surface stresses is caused by the dramatic variation of hm with temperature, which needs to be considered in engineering analysis.
Influence of Al on the magnetostriction of Fe-Ga polycrystal alloys under compressive stress
Long-long Liao; Mei-ling Fang; Jie Zhu; Ji-heng Li; Jian Wang
2014-01-01
Fe80Ga20-xAlx (x=0, 6, 9, 14) ingots were prepared from high purity elements using a vacuum induction system. X-ray diffraction patterns show that the alloys are A2 disordered structures. The influence of the partial substitution of Ga in Fe-Ga alloys with Al on their magnetostrictive properties was investigated, and the effects of different heat treatment conditions on the magnetostriction and microstructure of the alloy rods were also examined. The saturation magnetostriction value of Fe80Ga20 can reach to 240 × 10-6 under a compressive stress of 20 MPa. The Fe80Ga11Al9 alloy has many good properties, such as low hysteresis, high linearity of the magnetostriction curve, and low saturated magnetic field, which make it a potential candidate for magnetostrictive actuator and transducer applications. It is found that sub-grains have little influence on the magnetostriction of Fe-Ga alloys.
Analysis of Maximum Shear Stress of Asphalt Pavement%沥青路面最大剪应力分析
陈光伟; 费国新; 陈荣生
2012-01-01
Factors and variation of the maximum shear stress of the typical semi-rigid asphalt pavement and bridge deck pavement in Jiangsu were calculated and analyzed using ABAQUS software. The maximum shear stress distribution was consistent with the semi-rigid asphalt pavement and bridge deck pavement and the maximum shear stress level was close under the level. The maximum shear stress showed a positive correlation with the verticaland horizontal vehicle loads and was significantly affected by the loads. The maximum shear stress decreased as the pavement thickness and modulus increase, and increased as the semi-rigid base thickness and modulus increase, but the increase value was small. Thereby these analysis above would provides an academic basis for solving the rutting problem.%采用ABAQUS软件对典型半刚性基层沥青路面及桥面铺装层中最大剪应力影响因素及变化规律进行了计算与分析。分析表明：半刚性基层沥青路面与水泥混凝土桥面铺装层最大剪应力分布与变化规律基本一致，在相同荷载条件作用下，最大剪应力水平亦接近；最大剪应力与车辆垂直荷载和水平荷载作用呈正比关系，最大剪应力受其影响显著；最大剪应力随着面层或铺装层厚度、模量的增加而相应地变小，随着半刚性基层厚度与模量的增加而变大。以上抗剪影响因素及变化规律的研究为解决车辙问题提供了一定的理论基础。
无
2002-01-01
Significant compressive stress may be induced in thin plate weldment by anti-welding heating treatment (AWHT)with a temperature difference above 350℃, and an interesting phenomenon of obvious residual stress reduction on non-treated surface was discovered. The method of AWHT has no great effect on the mechanical properties including hardness, strength and toughness of the metal material. The results in the paper prompt a possibility application in shipbuilding industry.
Sushil Kumar Addy; Nil Ratan Chakraborty
2005-02-01
This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the inﬂuence of initial compressive hydrostatic stress. When the temperature of the half-space is altered, gravity waves propagate through the liquid layer along with sub-oceanic Rayleigh waves in the system. A new frequency equation has been derived here for gravity waves and sub-oceanic Rayleigh waves. It has been shown graphically that the phase velocity of gravity waves is inﬂuenced signiﬁcantly by the initial compressive hydrostatic stress present in the solid half-space, for a particular value of the phase velocity of sub-oceanic Rayleigh waves and different coupling co-efﬁcients of the temperature.
Strength criterion for rocks under compressive-tensile stresses and its application
Mingqing You
2015-08-01
Full Text Available Estimating in-situ stress with hydraulic borehole fracturing involves tensile strength of rock. Several strength criteria with three parameters result in tensile strengths with great differences, although they may describe the relation between strength of rock and confining pressure with low misfits. The exponential criterion provides acceptable magnitudes of tensile strengths for granites and over-estimates that for other rocks, but the criterion with tension cut-off is applicable to all rocks. The breakdown pressure will be lower than the shut-in pressure during hydraulic borehole fracturing, when the maximum horizontal principal stress is 2 times larger than the minor one; and it is not the peak value in the first cycle, but the point where the slope of pressure-time curve begins to decline.
K Gellynck
2013-06-01
Full Text Available Static compressive stress can influence the matrix, which subsequently affects cell behaviour and the cell’s ability to further transform the matrix. This study aimed to assess response to static compressive stress at different stages of osteoblast differentiation and assess the cell cytoskeleton’s role as a conduit of matrix-derived stimuli. Mouse bone marrow mesenchymal stem cells (MSCs (D1 ORL UVA, osteoblastic cells (MC3T3-E1 and post-osteoblast/pre-osteocyte-like cells (MLO-A5 were seeded in hydrated and compressed collagen gels. Contraction was quantified macroscopically, and cell morphology, survival, differentiation and mineralisation assessed using confocal microscopy, alamarBlue® assay, real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR and histological stains, respectively. Confocal microscopy demonstrated cell shape changes and favourable microfilament organisation with static compressive stress of the collagen matrix; furthermore, cell survival was greater compared to the hydrated gels. The stage of osteoblast differentiation determined the degree of matrix contraction, with MSCs demonstrating the greatest amount. Introduction of microfilament disrupting inhibitors confirmed that pre-stress and tensegrity forces were under the influence of gel density, and there was increased survival and differentiation of the cells within the compressed collagen compared to the hydrated collagen. There was also relative stiffening and differentiation with time of the compressed cell-seeded collagen, allowing for greater manipulation. In conclusion, the combined collagen chemistry and increased density of the microenvironment can promote upregulation of osteogenic genes and mineralisation; MSCs can facilitate matrix contraction to form an engineered membrane with the potential to serve as a ‘pseudo-periosteum’ in the regeneration of bone defects.
High level compressive residual stresses produced in aluminum alloys by laser shock processing
Gomez-Rosas, G. [Centro de Ingenieria y Desarrollo Industrial, CIDESI, Av. Playa Pie de la Cuesta, 702 Desarrollo San Pablo, c.p. 76130 Santiago de Queretaro, Queretaro (Mexico)]. E-mail: ggomez@cidesi.mx; Rubio-Gonzalez, C. [Centro de Ingenieria y Desarrollo Industrial, CIDESI, Av. Playa Pie de la Cuesta, 702 Desarrollo San Pablo, c.p. 76130 Santiago de Queretaro, Queretaro (Mexico); Ocana, J.L [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Molpeceres, C. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Porro, J.A. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain); Chi-Moreno, W. [Instituto Tecnologico de Morelia (Mexico); Morales, M. [Departamento de Fisica Aplicada a la Ingenieria Industrial, ETSII, Universidad Politecnica de Madrid (Spain)
2005-11-15
Laser shock processing (LSP) has been proposed as a competitive alternative technology to classical treatments for improving fatigue and wear resistance of metals. We present a configuration and results for metal surface treatments in underwater laser irradiation at 1064 nm. A convergent lens is used to deliver 1.2 J/cm{sup 2} in a 8 ns laser FWHM pulse produced by 10 Hz Q-switched Nd:YAG, two laser spot diameters were used: 0.8 and 1.5 mm. Results using pulse densities of 2500 pulses/cm{sup 2} in 6061-T6 aluminum samples and 5000 pulses/cm{sup 2} in 2024 aluminum samples are presented. High level of compressive residual stresses are produced -1600 MPa for 6061-T6 Al alloy, and -1400 MPa for 2024 Al alloy. It has been shown that surface residual stress level is higher than that achieved by conventional shot peening and with greater depths. This method can be applied to surface treatment of final metal products.
ZHU Jin-song; GAO Chang-e; SONG Yu-pu
2005-01-01
The effects of different lateral confinement stress on the fatigue behavior and cumulative damage of plain concrete were investigated experimentally. Eighty 100mm × 100mm × 100mm specimens of ordinary strength concrete were tested with constant-or variable-amplitude cyclic compression and lateral confinement pressure in two orthogonal directions. A fatigue equation was gained by modifying the classical Aas-Jakobsen SN equation and used for taking into account the effect of the confined stress on fatigue strength of plain concrete. The present study indicates that the fatigue failure is greatly influenced by the sequence of applied variable-amplitude fatigue loading, and Miner's rule is inapplicable to predict the residual fatigue life, especially in the sequence of low to high. The present research also shows that the exponent d of the Corten-Dolan's damage formula is a constant depending on the materials and the levels of load spectrum, and d can be determined through the two-stage fatigue tests. The residual fatigue lives predicted by Corten-Dolan' s damage formula are found to be in good agreement with the results of the experiments.
Hossain, R.; Pahlevani, F.; Quadir, M. Z.; Sahajwalla, V.
2016-10-01
Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.
Hossain, R; Pahlevani, F; Quadir, M Z; Sahajwalla, V
2016-10-11
Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels' performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.
Svenson, Mouritz Nolsøe; Thirion, Lynn M.; Youngman, Randall E.;
chamber to compress bulk glass samples isostatically up to 1 GPa at elevated temperature before or after the ion exchange treatment of an industrial sodium-magnesium aluminosilicate glass. Compression of the samples prior to ion exchange leads to a decreased Na+-K+ inter-diffusivity, increased compressive...
Tessema, Genene [Faculty of Science, Department of Physics, Addis Ababa University, P.O. Box 1176, Addis Ababa (Ethiopia) and Helmholtz-Institut fuer Strahlen und Kernphysik, Nussalle 14-16, 53115 Bonn (Germany)]. E-mail: genene@gmx.net
2006-03-01
Stress induced quadrupole interaction at the probe nucleus ({sup 111}Cd) in silicon has been studied using the perturbed {gamma}-{gamma} angular correlation (PAC) method. The extra nuclear field, at the sites of the nuclei, is produced via the disturbances of the surrounding charges by the action of a uniaxial compressive stress on the samples. However, the probes situated at various lattice locations in the sample showed different responses for the same value of stress. The various lattice environments are mainly caused by the involvement of either tellurium or antimony donor atoms in the samples. As a result, the donor free substitutional probe atoms experience a finite nuclear quadrupole interaction due to the broken symmetry of the charge distribution upon uniaxial compression; those probe atoms, which form pairs with donors, exhibit a strong electric-field gradient (EFG) that appears to be pressure independent.
Wijesekara, Waruna; Rosendahl, Lasse; Wu, NingYu;
Oxide thermoelectric materials are promising candidates for energy harvesting from mid to high temperature heat sources. In this work, the oxide thermoelectric materials and the final design of the high temperature thermoelectric module were developed. Also, prototypes of oxide thermoelectric...... generator were built for high temperature applications. This paper specifically discusses the thermoelectric module design and the prototype validations of the design. Here p type calcium cobalt oxide and n type aluminum doped ZnO were developed as the oxide thermoelectric materials. Hot side and cold side...... temperatures were used as 1100 K and 400 K respectively. Using analytical methods, the optimum thermoelement length and the thermoelements area ratio were explored in order to provide the maximum power output by the uni-couple and it is compared to methods reported in literature. Based on operating conditions...
Sung Woo Park; Byung Kwan Oh; Hyo Seon Park
2015-01-01
The safety of a multi-span waler beam subjected simultaneously to a distributed load and deflections at its supports can be secured by limiting the maximum stress of the beam to a specific value to prevent the beam from reaching a limit state for failure or collapse. Despite the fact that the vast majority of accidents on construction sites occur at waler beams in retaining wall systems, no safety monitoring model that can consider deflections at the supports of the beam is available. In this...
Kenji Takemoto
Full Text Available Mechanical stress that arises due to deformation of the extracellular matrix (ECM either stretches or compresses cells. The cellular response to stretching has been actively studied. For example, stretching induces phosphorylation of the myosin regulatory light chain (MRLC via the RhoA/RhoA-associated protein kinase (ROCK pathway, resulting in increased cellular tension. In contrast, the effects of compressive stress on cellular functions are not fully resolved. The mechanisms for sensing and differentially responding to stretching and compressive stress are not known. To address these questions, we investigated whether phosphorylation levels of MRLC were affected by compressive stress. Contrary to the response in stretching cells, MRLC was dephosphorylated 5 min after cells were subjected to compressive stress. Compressive loading induced activation of myosin phosphatase mediated via the dephosphorylation of myosin phosphatase targeting subunit 1 (Thr853. Because myosin phosphatase targeting subunit 1 (Thr853 is phosphorylated only by ROCK, compressive loading may have induced inactivation of ROCK. However, GTP-bound RhoA (active form increased in response to compressive stress. The compression-induced activation of RhoA and inactivation of its effector ROCK are contradictory. This inconsistency was due to phosphorylation of RhoA (Ser188 that reduced affinity of RhoA to ROCK. Treatment with the inhibitor of protein kinase A that phosphorylates RhoA (Ser188 induced suppression of compression-stimulated MRLC dephosphorylation. Incidentally, stretching induced phosphorylation of MRLC, but did not affect phosphorylation levels of RhoA (Ser188. Together, our results suggest that RhoA phosphorylation is an important process for MRLC dephosphorylation by compressive loading, and for distinguishing between stretching and compressing cells.
Liu, Ting; Lin, Baiquan; Yang, Wei; Zou, Quanle; Kong, Jia; Yan, Fazhi
2016-08-01
Hydraulic slotting, an efficient technique for underground enhanced coal bed methane (ECBM) recovery, has been widely used in China. However, its pressure relief mechanism is unclear. Thus far, only limited research has been conducted on the relationships among the mechanical properties, flaw parameters, and crack propagation patterns of coal after hydraulic slotting. In addition, because of the limitations of test methods, an in-depth information is not available for this purpose. In this work, numerical models of specimens containing combined flaws are established based on particle flow code method. Our results provide insights into the effects of flaw inclination angle on the mechanical properties, crack propagation patterns, and temporal and spatial evolution rules of stress field in specimens containing combined flaws during the loading process. Besides, based on the initiation position and underlying mechanism, three types of crack initiation modes are identified from the failure processes of specimens. Finally, the crack propagation pattern is quantitatively described by the fractal dimension, which is found to be inversely proportional to the uniaxial compressive strength and elastic modulus of the specimen. To verify the rationality of the numerical simulation results, laboratory tests were conducted and their results match well with those obtained from the numerical simulation.
Arthur, Emmanuel; Schjønning, Per; Møldrup, Per
2013-01-01
Pa). Investigated indicators for compression resistance included compression index, precompression stress, and resistance and resilience indices based on measured soil physical properties (bulk density, air-filled porosity, air permeability, and void ratio). Soil resilience was assessed following exposure...... of compacted cores to freeze-thaw (FT) and wet-dry (WD) cycles. The OC content increased with increased fertilisation and resulted in decreased initial bulk density, higher air-filled and total porosities, and increased organisation of the pore space. Soil resistance decreased with increasing OC content...... but the correlation was not significant. However, initial bulk density (ρbi) and initial gravimetric water content (wi) were significantly positively correlated to the indices of soil compression resistance, with the effect of ρbi being significantly stronger. Significant recovery of airfilled porosity and air...
丁向东; 连建设; 江中浩; 孙军
2001-01-01
Using large strain two-dimension axisymmetric elasto-plastic finite element method and the modified law of mixture, the effects of thermal residual stresses on the yielding behavior of short fiber reinforced metal matrix composite and their dependencies on the material structure parameters (fiber volume fraction, fiber aspect ratio and fiber end distance) were studied. It is demonstrated that the stress-strain partition parameter can be used to describe the stress transfer from the matrix to the fiber. The variation of the second derivation of the stress-strain partition parameter can be used to determine the elastic modulus, the proportion limit, the initial and final yield strengths. In the presence of thermal residual stress, these yielding properties are asymmetric and are influenced differently by the material structure parameters under tensile and compressive loadings.
Wilson, L.; Head, J. W., III
2008-09-01
have assumed a series of permutations of crustal density, crustal thickness, mantle density, magma density, source depth in mantle of melt generation, and crustal compressive stress, and investigated which permutations will allow the transfer of magma from source to surface. With so many variables it is easiest to illustrate the results by choosing one set of densities and varying the depths and stresses. We begin with crustal density of 2700 kg m-3, a mantle density of 3400 kg m-3 and a melt density of 3000 kg m-3. Table 1 then shows, as a function of the thickness of the crust (Hc), the minimum depth below the surface (Hm) from which mantle melts must be derived if their positive buoyancy in the mantle is to just compensate for their negative buoyancy in the crust and so enable them to reach the surface and erupt. For the values of Hm in Table 1 to be valid, the stress conditions in the crust must be such that a dike can remain open at all depths. However, this may not be possible in the presence of a horizontal compressive stress. The third and fourth columns of the table show the maximum horizontal compressive stress allowed if a dike is to remain open when the compressive stress is either uniform, i.e. the same at all depths in the crust (Su), or variable, specifically decreasing from the value given (Sv) at the surface to zero at the base of the crust. We now increase the crustal density slightly to 2800 kg m-3 but keep the mantle and melt densities the same. The results in Table 2 show, as expected, that the reduced amount of negative buoyancy of magma in the crust means that mantle melt sources need not be quite as deep as before. However, if a pathway is to remain open at all depths, significantly smaller compressive stresses are needed than in the previous case. Implications: This comparison demonstrates the major trend that we find: as the crust becomes denser it is easier, in terms of magma buoyancy alone, to erupt magma from a given depth in the mantle
Ghazzal, Mohamed N., E-mail: mohamed.ghazzal@uclouvain.be [Laboratoire de Chimie et Methodologie pour l' Evironnement, Universite Paul Verlaine de Metz, rue Victor Demange, 57500 Saint-Avold (France); Institute of Condensed Matter and Nanoscience Molecules, Solids and reacTivity (IMCN/MOST), Universite catholique de Louvain, Croix du Sud 2/17, B-1348 Louvain-la-Neuve (Belgium); Chaoui, N. [Laboratoire de Spectrometrie de Masse et de Chimie Laser, Universite Paul Verlaine de Metz, Boulvard arago, F-57078 Metz Cedex 3 (France); Genet, M. [Institute of Condensed Matter and Nanoscience Molecules, Division of Bio and Soft Matter (IMCN/BSMA), Universite catholique de Louvain, Croix du Sud 2/17, B-1348 Louvain-la-Neuve (Belgium); Gaigneaux, Eric M. [Institute of Condensed Matter and Nanoscience Molecules, Solids and reacTivity (IMCN/MOST), Universite catholique de Louvain, Croix du Sud 2/17, B-1348 Louvain-la-Neuve (Belgium); Robert, D. [Laboratoire des Materiaux, Surface et Procedes pour la Catalyse (LMSPC) CNRS-UMR7515, Antenne de Saint-Avold, UPV-Metz, Rue Victor Demange 57500 Saint-Avold (France)
2011-11-30
TiO{sub 2} thin films grown on different kinds of substrates were obtained by sol-gel process. X-ray diffraction revealed that the TiO{sub 2} lattice parameter c decreased continuously, indicating a continuous variation in the compressive stress, a negligible compressive stress of the film grown onto Soda-Lime Glass (SLG), medium compressive stress of the film grown onto BoroSilicate Glass (BSG) and large compressive stress of the film deposited onto the Quartz Substrate (QS). UV-Vis absorbance spectra exhibited a red-shift of the absorbance edge of the TiO{sub 2} films suggesting a lowering of the band gap, which is a direct consequence of the increase of the compressive stress. X-ray photoelectron spectroscopy revealed that the surface composition of titania films was similar except for sodium-ion concentration. The rate observed during the photo-oxydation of the stearic acid on TiO{sub 2}/QS was twice as high as that of TiO{sub 2}/BSG and about 1000 times superior to that of TiO{sub 2}/SLG. The photoinduced wettability shows an identical dependence of the compressive stress. According to these results, the compressive stress could be used to tune the band gap of the titanium oxide in order to enhance the photoinduced properties.
Wang, Cheng-Long; Wang, Hui; Xiao, Fei; Wang, Chuan-Dong; Hu, Guo-Li; Zhu, Jun-Feng; Shen, Chao; Zuo, Bin; Cui, Yi-Min; Li, De; Yuan-Gao; Zhang, Xiao-Ling; Chen, Xiao-Dong
2017-02-14
Developmental dysplasia of the hip (DDH) is a common musculoskeletal disorder characterized by a mismatch between acetabulum and femoral head. Mechanical force plays an important role during the occurrence and development of abnormities in acetabulum and femoral head. In this study, we established a mechanical force model named cyclic compressive stress (Ccs). To analyze the effect of Ccs on DDH, we detected special genes in chondrocytes and osteoblasts. Results showed that Ccs downregulated chondrogenesis of ADTC5 in a concentration-dependent manner. Moreover, the mRNA level of Scinderin (Scin) considerably increased. We established lentivirus-SCIN(GV144-SCIN) to transfect hBMSCs, which were treated with different Ccs levels (0.25 Hz*5 cm, 0.5 Hz*5 cm, and 1 Hz*10 cm); the result showed that overexpression of Scin upregulated osteogenesis and osteoclastogenesis. By contrast, expression of chondrocyte-specific genes, including ACAN, COL-2A, and Sox9, decreased. Further molecular investigation demonstrated that Scin promoted osteogenesis and osteoclastogenesis through activation of the p-Smad1/5/8, NF-κB, and MAPK P38 signaling pathways, as well as stimulated the expression of key osteoclast transcriptional factors NFATc1 and c-Fos. Moreover, Scin-induced osteogenesis outweighed osteoclastogenesis in defective femur in vivo. The results of the analysis of Micro-CT confirmed these findings. Overall, Ccs influenced the development of DDH by promoting osteogenesis and cartilage degradation. In addition, Scin played a vital role in the development of DDH.
Mills, Dean E; Johnson, Michael A; McPhilimey, Martin J; Williams, Neil C; Gonzalez, Javier T; Barnett, Yvonne A; Sharpe, Graham R
2014-04-15
The influence of oxidative stress, diaphragm fatigue, and inspiratory muscle training (IMT) on the cytokine response to maximum sustainable voluntary ventilation (MSVV) is unknown. Twelve healthy males were divided equally into an IMT or placebo (PLA) group, and before and after a 6-wk intervention they undertook, on separate days, 1 h of (1) passive rest and (2) MSVV, whereby participants undertook volitional hyperpnea at rest that mimicked the breathing and respiratory muscle recruitment patterns commensurate with heavy cycling exercise. Plasma cytokines remained unchanged during passive rest. There was a main effect of time (P ventilation and increases in plasma IL-6 concentration. In conclusion, increases in plasma IL-1β and IL-6 concentrations during MSVV were not due to diaphragm fatigue or DNA damage in PBMC. Increases in plasma IL-6 concentration during MSVV are attenuated following IMT, and the plasma IL-6 response is dependent upon the level of respiratory muscle work and minute ventilation.
Jones, D.P.; Hoppe, R.G. [Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.; Hechmer, J.L. [Babcock and Wilcox Co., Barberton, OH (United States); James, B.A. [Colorado School of Mines, Golden, CO (United States). Dept. of Metallurgy
1993-12-01
A series of fatigue crack growth rate tests was conducted in order to study effects of negative stress ratio on fatigue crack growth rate of low-alloy steel in air. Four-point bend specimens were used to simulate linear stress distributions typical of pressure vessel applications. This type of testing adds to knowledge on negative stress ratio effects for low-alloy steels obtained in the past from uniform tension-compression tests. Applied bending stress range was varied over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. Crack geometries were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. Results are presented in terms of the stress intensity factor ratio R = K{sub MIN}/K{sub MAX}. The negative R-ratio test results were correlated to an equation of the form da/dN = C[{Delta}K/(A-R)]{sup n}, where A, C, and n are curve fitting parameters. It was found that effects of negative R-ratio on fatigue crack growth rates for even the high stress range tests could be bounded by correlating the above equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.
Abdel-Salam, Zainab; Allam, Lawra; Wadie, Bassem; Enany, Bassem; Nammas, Wail
2015-01-01
Pneumatic compression of the lower part of the body increases systemic vascular resistance and left ventricular afterload. We compared the diagnostic accuracy of dobutamine stress echocardiography (DSE) with pneumatic compression of the lower extremities, vs. standard DSE, for detection of angiographically significant coronary artery disease (CAD) in patients with normal baseline resting wall motion. We enrolled 70 consecutive patients with no resting wall motion abnormalities (WMA), who underwent DSE. DSE was repeated with pneumatic compression of the lower extremities three days after the initial standard DSE. A positive test was defined as the induction of WMA in at least two contiguous non-overlap segments at any stage of dobutamine infusion. Significant coronary stenosis was defined as ≥ 50% obstruction of ≥ 1 sizable artery by coronary angiography. The mean age of the study cohort was 54.7 ± 9.9 years; 55.7% were females. Thirty-eight (54.3%) patients had significant CAD. The mean test duration was 15.8 ± 5.1 min for standard DSE and 11.7 ± 4.1 min for DSE with pneumatic compression. Analysis of standard DSE revealed sensitivity, specificity, and positive and negative predictive values of 81.6%, 90.6%, 91.2%, and 80.6%, respectively; overall accuracy was 85.7%. Analysis of DSE with pneumatic compression revealed sensitivity, specificity, and positive and negative predictive values of 89.5%, 87.5%, 89.5%, and 87.5%, respectively; overall accuracy was 88.6%. In symptomatic patients with suspected CAD referred for evaluation by DSE, who have no resting wall motion abnormalities, pneumatic compression of the lower extremities during DSE improved the sensitivity but slightly reduced the specificity for detection of angiographically significant CAD, compared with standard DSE. Moreover, it reduced the test duration.
Richardson, R. M.; Solomon, S. C.; Sleep, N. H.
1979-01-01
In the present paper, the basic set of global intraplate stress orientation data is plotted and tabulated. Although the global intraplate stress field is complicated, several large-scale patterns can be seen. Much of stable North America is characterized by an E-W to NE-SW trend for the maximum compressive stress. South American lithosphere beneath the Andes, and perhaps farther east in the stable interior, has horizontal compressive stresses trending E-W to NW-SE. Western Europe north of the Alps is characterized by a NW-SE trending maximum horizontal compression, while Asia has the maximum horizontal compressive stress trending more nearly N-S, especially near the Himalayan front.
Richardson, R. M.; Solomon, S. C.; Sleep, N. H.
1979-01-01
In the present paper, the basic set of global intraplate stress orientation data is plotted and tabulated. Although the global intraplate stress field is complicated, several large-scale patterns can be seen. Much of stable North America is characterized by an E-W to NE-SW trend for the maximum compressive stress. South American lithosphere beneath the Andes, and perhaps farther east in the stable interior, has horizontal compressive stresses trending E-W to NW-SE. Western Europe north of the Alps is characterized by a NW-SE trending maximum horizontal compression, while Asia has the maximum horizontal compressive stress trending more nearly N-S, especially near the Himalayan front.
Greenbaum, A.; Baker, D. J.; Davis, J. G., Jr.
1974-01-01
A computer program for plotting stress-strain curves obtained from compression and tension tests on rectangular (flat) specimens and circular-cross-section specimens (rods and tubes) and both stress-strain and torque-twist curves obtained from torsion tests on tubes is presented in detail. The program is written in FORTRAN 4 language for the Control Data 6000 series digital computer with the SCOPE 3.0 operating system and requires approximately 110000 octal locations of core storage. The program has the capability of plotting individual strain-gage outputs and/or the average output of several strain gages and the capability of computing the slope of a straight line which provides a least-squares fit to a specified section of the plotted curve. In addition, the program can compute the slope of the stress-strain curve at any point along the curve. The computer program input and output for three sample problems are presented.
Jones, D.P.; Hoppe, R.G. (Westinghouse Electric Corp., West Mifflin, PA (United States). Bettis Atomic Power Lab.); Hechmer, J.L. (Babcock Wilcox Co., Barberton, OH (United States)); James, B.A. (Colorado School of Mines, Golden, CO (United States). Metallurgy Dept.)
1994-08-01
A series of fatigue crack growth rate tests was conducted in order to study the effects of negative stress ratio upon the fatigue crack growth rate of low-alloy steel in air environment. The tests used four-point bend specimens in order to simulate linear stress distributions typical of many pressure vessel applications. This type of testing adds to the knowledge on negative stress ratio effects for low-alloy steels that in the past have been obtained from uniform tension-compression tests. Additionally, the applied bending stress range was varied from low values of applied stress to high values of applied stress over twice the yield strength. Load control was used for tests for which the stress range was less than twice the yield strength and deflection control was used for the higher stress range tests. The crack geometries involved were both short and long fatigue cracks started at notches and tight fatigue cracks for which crack closure could occur over the full crack face. The results are presented in terms of the stress intensity factor ratio R = K[sub MIN]/K[sub MAX]. The negative R-ratio test results were correlated to an equation of the form da/dN = C[[delta]K/(A-R)][sup n] where A, C and n are curve-fitting parameters. It was found that the effects of negative R-ratio on the fatigue crack growth rates for even the high stress range tests could be bounded by correlating the foregoing equation to only positive R-ratio test results and extending the resulting equation into the negative R-ratio regime.
Pandu Ramavath
2016-12-01
Full Text Available Alumina- and cordierite-based honeycombs with varying relative densities were extruded and sintered at the respective sintering temperatures. Solid samples are also prepared under identical conditions and flexural strength (σf was estimated by three-point bend measurements. Buckling stress of honeycombs are predicted based on σf using standard equations and validated with quasi-static compression test along the channels of honeycombs with varying relative densities. The discrepancy observed on calculated and measured values is correlated with the pre-existing flaws indicating the criticality in close control of processing parameters.
Barrientos, Eva; Pelayo, Fernández; Tanaka, Eiji; Lamela-Rey, María Jesús; Fernández-Canteli, Alfonso
2016-04-01
In this study, the dynamic and static compressive properties of the whole porcine temporomandibular joint (TMJ) disc were investigated. The aim of the study was to develop a new simple method for the evaluation of joint viscoelasticity, enabling examination of the load-bearing capacity and joint flexibility of the entire disc. For the experiments, a novel testing fixture that reproduces the condylar and fossa surfaces of the TMJ was developed to replicate TMJ disc geometry. Ten porcine discs were used in the experiments. Each disc was dissected from the TMJ and sinusoidal compressive strain was applied to obtain the storage and loss moduli. Static strain control tests were carried out to obtain the relaxation modulus. The result of static and dynamic tests indicated that the whole disc presented viscoelastic behavior under compression. Storage and loss moduli increased with frequency and the relaxation modulus decreased over time. The loss tangent showed less frequency dependence, with values ranging from 0.2 to 0.3, suggesting that the viscous properties of the disc cannot be neglected. These results provide a better understanding of whole disc mechanical compression behavior under realistic TMJ working conditions.
Salces Judit
2011-08-01
Full Text Available Abstract Background Reference genes with stable expression are required to normalize expression differences of target genes in qPCR experiments. Several procedures and companion software have been proposed to find the most stable genes. Model based procedures are attractive because they provide a solid statistical framework. NormFinder, a widely used software, uses a model based method. The pairwise comparison procedure implemented in GeNorm is a simpler procedure but one of the most extensively used. In the present work a statistical approach based in Maximum Likelihood estimation under mixed models was tested and compared with NormFinder and geNorm softwares. Sixteen candidate genes were tested in whole blood samples from control and heat stressed sheep. Results A model including gene and treatment as fixed effects, sample (animal, gene by treatment, gene by sample and treatment by sample interactions as random effects with heteroskedastic residual variance in gene by treatment levels was selected using goodness of fit and predictive ability criteria among a variety of models. Mean Square Error obtained under the selected model was used as indicator of gene expression stability. Genes top and bottom ranked by the three approaches were similar; however, notable differences for the best pair of genes selected for each method and the remaining genes of the rankings were shown. Differences among the expression values of normalized targets for each statistical approach were also found. Conclusions Optimal statistical properties of Maximum Likelihood estimation joined to mixed model flexibility allow for more accurate estimation of expression stability of genes under many different situations. Accurate selection of reference genes has a direct impact over the normalized expression values of a given target gene. This may be critical when the aim of the study is to compare expression rate differences among samples under different environmental
Oh, S S [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Ha, D W [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Ha, H S [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Park, C [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Kwon, Y K [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Ryu, K S [Applied Superconductivity Research Group, Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Shin, H S [School of Mechanical Engineering, Andong National University, Andong 760-749 (Korea, Republic of)
2004-01-01
In order to investigate the degradation of critical current (I{sub c}) in the Ag alloy sheathed Bi-2223 tapes due to a transverse compressive stress introduced during manufacturing and operation of the HTS systems, a sample holder consisting of the upper block made of Ti alloy and the lower support plate made of glass fibre reinforced plastic was prepared. A shorter spacing of voltage taps caused large degradation of critical current with respect to compressive stress. It was found that the extent of the I{sub c} degradation is proportional to the initial critical current density of the tapes. Through the experiment optimizing the shape of voltage terminals and the pressing load for the continuous contact type 4-probe I{sub c} measurement system, it was found that the conical shape tip with large curvature radius was effective in suppressing the I{sub c} degradation in Bi-2223 tapes during the I{sub c} measurement. A hard alloy sheath of Ag-0.6wt%Mn was found to be quite tolerant to the I{sub c} degradation against the pressing load of voltage terminals.
刘汝宽; 许方雷; 肖志红; 李昌珠; 李辉; 曾凡涛; 叶红齐
2015-01-01
The relationships among compression ratio and stress, compression ratio and residual oil of cake in pressing process of castor beans were studied using the test equipment under different states of oilseeds and ways of pressing manners. The results show that variation of stress increases nonlinearly and residual oil rate decreases with the increase of compression ratio. Lower residual oil of cake was obtained by pressing gently and frequently. Curve fitting on both relationships had been built and parameters for the model were obtained by least square procedure and deepening research on pressing process of the castor beans for castor oil. By assuming that the value of oil production is equivalent to the value of energy consumption, the critical compression ratio of intact seeds is 6.2 while that of crushed seeds is 3.6.
Chen, L. Y.; Ge, Q.; Qu, S.; Jiang, Q. K.; Nie, X. P.; Jiang, J. Z.
2008-05-01
The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.
Jang, Hyun-jeong; Kim, Suhn-yeop; Oh, Duck-won
2015-04-01
The aim of the present study was to investigate the effects of augmented trunk stabilization with external compression support (ECS) on the electromyography (EMG) activity of shoulder and scapular muscles and shoulder abductor strength during isometric shoulder abduction. Twenty-six women volunteered for the study. Surface EMG was used to monitor the activity of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and middle deltoid (MD), and shoulder abductor strength was measured using a dynamometer during three experimental conditions: (1) no external support (condition-1), (2) pelvic support (condition-2), and (3) pelvic and thoracic supports (condition-3) in an active therapeutic movement device. EMG activities were significantly lower for UT and higher for MD during condition 3 than during condition 1 (p Shoulder abductor strength was significantly higher during condition 3 than during condition 1 (p muscle effort of the UT during isometric shoulder abduction and increasing shoulder abductor strength. Copyright © 2014 Elsevier Ltd. All rights reserved.
Neustroev, V.S.; Makarov, E.I.; Belozerov, S.V.; Ostrovsky, Z.E. [JSC ' SSC RIAR' (Russian Federation)
2011-07-01
At present, work in justification of the lifetime prolongation of the operated VVER-440 and VVER-1000 internals as well as of the operation of new VVER reactor internals up to 60 years is the most urgent. Fe-0.08C-18Cr-10Ni-Ti austenitic steel, being the material of operated and new VVER internals, was selected for the experiment. As the design of internals is very complicated and there are many holes for cooling, areas with compressive and tensile stresses may appear, so it is important to investigate the effect of stresses on the properties and structure of the material. Experiments to investigate the effect of tensile stress on the properties and structure of the material have been carried out both at 'SSC RIAR', Russia and abroad, but the effect of compressive stress has not been practically studied. Besides, we had to check if the known mechanisms and dependence of creep strain on stress type would remain. This paper presents the effect of compressive and tensile stresses on swelling, microstructure and creep strain of Fe-0.08C-18Cr-10Ni-Ti steel. It appears that: -) creep strain of the specimens is in the proportion to damage dose and tensile stress, and -) hardening induced by irradiation is the same for both stressed and non-stressed specimens
Pesin Alexander
2017-01-01
Full Text Available A three-roll rolling process is a significant technique in the production of wire rod, round bars and hexagonal profiles for structural applications. Better mechanical properties of wire rod, round bars and hexagonal profiles can be achieved due to large plastic deformation by the three-roll rolling process. Asymmetric rolling is a novel technique characterized by a kinematic asymmetry linked to the difference in peripheral speed of the rolls, able to introduce additional shear strains through the bar thickness. Physical simulation of shear strain, which is similar to that occurring in asymmetric three-roll rolling process, is very important for design of technology of producing ultrafine grain materials. Shear testing is complicated by the fact that a state of large shear is not easily achievable in most specimen geometries. Application of the shear-compression testing and specimen geometry to physical simulation of asymmetric three-roll rolling process is discussed in the paper. FEM simulation and comparison of the stress-strain state during shear-compression testing and asymmetric three-roll rolling process is presented. The results of investigation can be used to optimize the physical simulation of asymmetric three-roll rolling processes and for design of technology of producing ultrafine grain materials by severe plastic deformation.
Transformation toughening of Al2O3/ZrO2 laminated ceramics with residual compressive stress
无
2007-01-01
With the help of scanning electronic microscopy and X-ray diffraction, the relationships of microstmcture characteristics,phase assemblage, and fracture micrograph of Al2O3/ZrO2 laminated ceramics were studied. Compared with monolithic Al2O3/ZrO2 ceramics, the existence of surface compressive stresses greatly restrained the growth of ZrO2 and Al2O3 grains at high sinter temperature, fined the grain size, and increased the content of metastable t-ZrO2, which made the fracture transformation energy quantity 70% higher than that of the monolithic ceramics. The trans-granular and inter-granular fracture features were observed in the surface and center layers, which further verified that transformation toughening is the main mechanism, whereas, micro-crack toughening is helpful for enhancing fracture toughness.
Leahy, Lauren
During trauma resulting from impacts and blast waves, sinusoidal waves permeate the brain and cranial arterial tissue, both non-homogeneous biological tissues with high fluid contents. The experimental shear stress response to sinusoidal translational shear deformation at 1 Hz and 25% strain amplitude and either 0% or 33% compression is compared for rat brain tissue and bovine aortic tissue. Both tissues exhibit Mullins effect in shear. Harmonic wavelet decomposition, a novel application to the mechanical response of these tissues, shows significant 1 Hz and 3 Hz components. The 3 Hz component magnitude in brain tissue, which is much larger than in aortic tissue, may correlate to interstitial fluid induced drag forces that decrease on subsequent cycles perhaps because of damage resulting in easier fluid movement. The fluid may cause the quasiperiodic, viscoelastic behavior of brain tissue. The mechanical response differences under impact may cause shear damage between arterial and brain connections.
Liu, Wei; Lu, Jian; Leung, Lai-Yung R.; Xie, Shang-Ping; Liu, Zhengyu; Zhu, Jiang
2015-02-22
This paper investigates the changes of the Southern Westerly Winds (SWW) and Southern Ocean (SO) upwelling between the Last Glacial Maximum (LGM) and preindustrial (PI) in the PMIP3/CMIP5 simulations, highlighting the role of the Antarctic sea ice in modulating the wind stress effect on the ocean. Particularly, a discrepancy may occur between the changes in SWW and westerly wind stress, caused primarily by an equatorward expansion of winter Antarctic sea ice that undermines the wind stress in driving the liquid ocean. Such discrepancy may reflect the LGM condition in reality, in view of that the model simulates this condition has most credible simulation of modern SWW and Antarctic sea ice. The effect of wind stress on the SO upwelling is further explored via the wind-induced Ekman pumping, which is reduced under the LGM condition in all models, in part by the sea-ice “capping” effect present in the models.
Lager, J. R.
1975-01-01
A cylindrical shell structure 3.66 m (144 in.) high by 4.57 m (180 in.) diameter was designed using a wide variety of materials and structural concepts to withstand design ultimate combined loading 1225.8 N/cm (700 lb/in.) axial compression and 245.2 N/cm (140 lb/in.) torsion. The overall cylinder geometry and design loading are representative of that expected on a high performance space tug vehicle. The relatively low design load level results in designs that use thin gage metals and fibrous-composite laminates. Fabrication and structural tests of small panels and components representative of many of the candidate designs served to demonstrate proposed fabrication techniques and to verify design and analysis methods. Three of the designs evaluated, honeycomb sandwich with aluminum faceskins, honeycomb sandwich with graphite/epoxy faceskins, and aluminum truss with fiber-glass meteoroid protection layers, were selected for further evaluation.
周小平; 张永兴; 哈秋聆; 王建华
2004-01-01
A micromechanics-based model is established. The model takes the interaction among sliding cracks into account, and it is able to quantify the effect of various parameters on the localization condition of damage and deformation for brittle rock subjected to compressive loads. The closed-form explicit expression for the complete stress-strain relation of rock containing microcracks subjected to compressive loads was obtained. It is showed that the complete stress-strain relation includes linear elasticity,nonlinear hardening,rapid stress drop and strain softening.The behavior of rapid stress drop and strain softening is due to localization of deformation and damage. Theoretical predictions have shown to be consistent with the experimental results.
Modern tectonic stress field deeply in Xuzhou Coal Mine
Zhen-jie JING; Fu-ren XIE; Xiao-feng CUI; Jing-fei ZHANG
2013-01-01
By inverting fault slip data,the parameters of 12 tectonic stress tensors in the mine region can be determined.The following characteristics can be obtained for recent tectonic stress fields,which are found deep in the study region.The results show that the recent tectonic stress field mainly presents the characteristics of near NWW-SSE maximum compressional stress and near NE-SW minimum extensional stress,while the stress regimes are mainly of strike slip,part of the reverse-fault type.Recent tectonic stress field in the region is characterized by horizontal components.The maximum principal compression stress direction was from NEE to SEE,the average principal compression stress direction was near NWW-SSE maximum compressional stress and near NE-SW minimum extensional.The recent tectonic stress field of the studied area can be controlled by a large tectonic stress area.
N. A. Zolotukhina; I.P. Kharchenko
2005-01-01
We investigate the properties of interplanetary inhomogeneities generating long-lasting mid-latitude Pc1, 2 geomagnetic pulsations. The data from the Wind and IMP 8 spacecrafts, and from the Mondy and Borok midlatitude magnetic observatories are used in this study. The pulsations under investigation develop in the maximum and early recovery phase of magnetic storms. The pulsations have amplitudes from a few tens to several hundred pT andlast more than seven hours. A close association of the increase (decrease) in solar wind dynamic pressure (Psw) with the onset or enhancement (attenuation or decay) of these pulsations has been established. Contrary to high-latitude phenomena, there is a distinctive feature of the interplanetary inhomogeneities that are responsible for generation of long-lasting mid-latitude Pc1, 2. It is essential that the effect of the quasi-stationary negative Bz-component of the interplanetary magnetic field on the magnetosphere extends over 4 hours. Only then are the Psw pulses able to excite the above-mentioned type of mid-latitude geomagnetic pulsations. Model calculations show that in the cases under study the plasmapause can form in the vicinity of the magnetic observatory. This implies that the existence of an intense ring current resulting from the enhanced magnetospheric convection is necessary for the Pc1, 2 excitation. Further, the existence of the plasmapause above the observation point (as a waveguide) is necessary for long-lasting Pc1 waves to arrive at the ground.
Ravindranadh BOBBILI; V. MADHU; A.K. GOGIA
2014-01-01
An artificial neural network (ANN) constitutive model is developed for high strength armor steel tempered at 500 ?C, 600 ?C and 650 ?C based on high strain rate data generated from split Hopkinson pressure bar (SHPB) experiments. A new neural network configuration consisting of both training and validation is effectively employed to predict flow stress. Tempering temperature, strain rate and strain are considered as inputs, whereas flow stress is taken as output of the neural network. A comparative study on JohnsoneCook (JeC) model and neural network model is performed. It was observed that the developed neural network model could predict flow stress under various strain rates and tempering temperatures. The experimental stressestrain data obtained from high strain rate compression tests using SHPB, over a range of tempering temperatures (500e650 ?C), strains (0.05e0.2) and strain rates (1000e5500/s) are employed to formulate JeC model to predict the high strain rate deformation behavior of high strength armor steels. The J-C model and the back-propagation ANN model were developed to predict the high strain rate deformation behavior of high strength armor steel and their predictability is evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). R and AARE for the JeC model are found to be 0.7461 and 27.624%, respectively, while R and AARE for the ANN model are 0.9995 and 2.58%, respectively. It was observed that the predictions by ANN model are in consistence with the experimental data for all tempering temperatures.
Scalerandi, M; Johnson, P A
2003-01-01
Local interaction simulation approach simulations of the ultrasonic wave propagation in multi-grained materials have succeeded in reproducing most of the recently observed nonclassical nonlinear effects, such as stress-strain hysteresis and discrete memory in quasi-static experiments and a downwards shift of the resonance frequency and the generation of odd harmonics at specific amplitude rates in dynamics experiments. By including a simple mechanism of thermally activated random transitions, we can predict the occurrence of experimentally observed effects, such as the conditioning and relaxation of the specimen. Experiments are also suggested for a quantitative assessment of the validity of the model.
Horikawa K.
2012-08-01
Full Text Available In this study, at first, the effect of strain rate on the strength and the absorbed energy of polyimide foam was experimentally examined by carrying out a series of compression tests at various strain rates, from 10−3 to 103 s−1. This polyimide foam has open cell structure with small cell size of 0.3 ∼ 0.6 mm. In the measurement of impact load, a special load cell with a small part for sensing load was adopted. For the measurement of the displacement, a high-speed camera was used. It was found that the flow stress of polyimide foam and the absorbed energy up to a strain of 0.4 increased with the increase of the strain rates. Secondly, the effect of ambient temperature on the strength and absorbed energy of polyimide foam was also investigated by using a sprit Hopkinson pressure bar apparatus and testing at elevated temperatures of 100 and 200 ∘C. With the increase of temperature, the strength and absorbed energy decreased and the effect is smaller in dynamic tests than static tests.
Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben;
1999-01-01
An investigation of fatigue failure in wood subjected to load cycles in compression parallel to grain is presented. Small clear specimens of spruce are taken to failure in square wave formed fatigue loading at a stress excitation level corresponding to 80% of the short term strength. Four...... frequencies ranging from 0.01 Hz to 10 Hz are used. The number of cycles to failure is found to be a poor measure of the fatigue performance of wood. Creep, maximum strain, stiffness and work are monitored throughout the fatigue tests. Accumulated creep is suggested identified with damage and a correlation...... is observed between stiffness reduction and accumulated creep. A failure model based on the total work during the fatigue life is rejected, and a modified work model based on elastic, viscous and non-recovered viscoelastic work is experimentally supported, and an explanation at a microstructural level...
Xu, Xing-Wang; Peters, Stephen; Liang, Guang-He; Zhang, Bao-Lin
2016-01-01
We report on a new mechanical principle, which suggests that a confined liquid in the elastic lithosphere has the potential to transmit a maximum applied compressive stress. This stress can be transmitted to the internal contacts between rock and liquid and would then be transformed into a normal compressive stress with tangential tensile stress components. During this process, both effective compressive normal stress and tensile tangential stresses arise along the liquid–rock contact. The minimum effective tensile tangential stress causes the surrounding rock to rupture. Liquid-driven fracture initiates at the point along the rock–liquid boundary where the maximum compressive stress is applied and propagates along a plane that is perpendicular to the minimum effective tensile tangential stress and also is perpendicular to the minimum principal stress.
Mataya, M.C.; Sackschewsky, V.E.
1993-05-01
Temperature change from conversion of deformation to internal heat, and its effect on stress-strain behavior of alloy 304L was investigated by initially isothermal (temperature of specimen, compression dies, environment equilibrated at initiation of test) uniaxial compression. Strain rate was varied 0.01 s{sup {minus}1} to 1 s{sup {minus}1} (thermal state of specimen varied from nearly isothermal to nearly adiabatic). Specimens were deformed at 750 to 1150 to a strain of 1. Change in temperature with strain was calculated via finite element analysis from measured stress-strain data and predictions were confirmed with thermocouples to verify the model. Temperature increased nearly linearly at the highest strain rate, consistent with temperature rise being a linear function of strain (adiabatic). As strain rate was lowered, heat transfer from superheated specimen to cooler dies caused sample temperature to increase and then decrease with strain as the sample thinned and specimen-die contact area increased. As-measured stress was corrected. Resulting isothermal flow curves were compared to predictions of a simplified method suggested by Thomas and Shrinivasan and differences are discussed. Strain rate sensitivity, activation energy for deformation, and flow curve peak associated with onset of dynamic recrystallization were determined from both as-measured and isothermal stress-strain data and found to vary widely. The impact of utilizing as-measured stress-strain data, not corrected for internal heating, on results of a number of published investigations is discussed.
Lee, H.; Haimson, B.
2007-12-01
drillhole wall conditions is drastically different from that conventionally expected, but is compatible with breakout formation mechanism in granite (Haimson, Int. J. Rock Mech., 2007). All the 'unjacketed' true triaxial strength data can be fitted by a simple function in the octahedral shear stress versus octahedral normal stress domain, yielding a Nadai-type true triaxial strength criterion. The criterion can be used in conjunction with breakouts that have been located within the cored zone to yield the maximum horizontal in situ stress σH when the other two principal stress are known. Assuming that the state of stress at breakout-drillhole intersections (located for example by BHTV logging) is sufficient to bring about brittle failure (Vernik and Zoback, 1992), one can substitute the known principal stresses there (obtained from the Kirsch solution) for the corresponding values in the criterion. The in situ σv is given by the overburden density, σh is typically obtained from hydrofrac shut-in pressures, breakout width is extracted from BHTV logs, borehole fluid pressure is a function of its density, and the Poisson's ratio is obtained from mechanical lab testing. The only unknown, σH, is thus readily computed. An actual computation was not carried out because data on hydrofrac pressures and breakout dimensions were not available at the time of this submission.
Kinkhabwala, Ali
2013-01-01
The most fundamental problem in statistics is the inference of an unknown probability distribution from a finite number of samples. For a specific observed data set, answers to the following questions would be desirable: (1) Estimation: Which candidate distribution provides the best fit to the observed data?, (2) Goodness-of-fit: How concordant is this distribution with the observed data?, and (3) Uncertainty: How concordant are other candidate distributions with the observed data? A simple unified approach for univariate data that addresses these traditionally distinct statistical notions is presented called "maximum fidelity". Maximum fidelity is a strict frequentist approach that is fundamentally based on model concordance with the observed data. The fidelity statistic is a general information measure based on the coordinate-independent cumulative distribution and critical yet previously neglected symmetry considerations. An approximation for the null distribution of the fidelity allows its direct conversi...
Crenshaw, K
2012-06-01
"Time-space compression" means "processes that … revolutionize the objective qualities of space and time." (David Harvey, The Condition of Postmodernity.)Modern workflows suffer from negative time-space compression: computers, internet, email, smartphones, texting and chat all promise productivity, yet they can encroach on our time and clutter our minds without eliminating those lurking piles of paper. Physicists in medicine face additional technology-related challenges on top of all that. However, the laws governing our time, workspaces, and teams are universal. Understand those laws, and you understand how to control the forces that derail personal and team workflow. Then, by drawing on a few practical techniques, you can create positive time-space compression: revolutionizing your workspace and systems to get more done, with noticeably less stress, balancing work and fun in all your life areas, keeping your desk so clean your associates will think you're going on vacation. An approach called Total, Relaxed Organization (TRO) makes this possible. TRO was developed by Priacta, Inc. (Kevin Crenshaw's company) using best practices from many popular time management systems. TRO has measurable Results: an average net gain of 581 productive hrs/yr, and average stress reduction of 59.6% from all sources combined. While these numbers are subjective and self-reported, they indicate a consistent improvement in the quality of life for TRO adherents. This working presentation compresses a (normally paid) 7-hour TRO personal coaching session into a 75-minute interactive, entertaining, and highly-practical workshop for each participant. 1. Understand the key principles/laws that govern your use of time and (work)space. 2. Identify your personal barriers that currently work against those principles. 3. Create a personal action plan (based on those time/workspace principles and practical techniques) to re-engineer your personal and team workflow for optimal results. © 2012
Mortar constituent of concrete under cyclic compression
Maher, A.; Darwin, D.
1980-10-01
The behavior of the mortar constituent of concrete under cyclic compression was studied and a simple analytic model was developed to represent its cyclic behavior. Experimental work consisted of monotonic and cyclic compressive loading of mortar. Two mixes were used, with proportions corresponding to concretes having water cement ratios of 0.5 and 0.6. Forty-four groups of specimens were tested at ages ranging from 5 to 70 days. complete monotonic and cyclic stress strain envelopes were obtained. A number of loading regimes were investigated, including cycles to a constant maximum strain. Major emphasis was placed on tests using relatively high stress cycles. Degradation was shown to be a continuous process and a function of both total strain and load history. No stability or fatigue limit was apparent.
李继兰; 李国芬; 陈耀章
2012-01-01
The decking on the top of bridge pier of the continuous steel-concrete composite beam is easily cracked by the action of non-load factors. The support forced displacement method is one of the effective methods to control or slow down the crack. To discuss the pre-compressed stress effect of the forced displacement method in the negative bending moment area of the decking of the composite beam bridge, taken the 6 x90 m continuous steel-concrete composite beam bridge at Hankou side of Erqi Changjiang River Bridge as research object, the improvement on traditional support forced displacement method was conducted. Besides, a local simulation analysis was accomplished on the basis of a hybrid finite element model of large "beam-shell-solid" which was established through APDL of ANSYS. A conclusion drawn from the theoretical and measured values shows that enough pre-compressed stress reserves, the maximum compressive stress of which was 18. 5 MPa, was produced in the decking of the negative moment area by the improved support forced displacement method. On this basis, the pre-compressed stress reserves by the improved method gained more than 0. 41 - 0. 46 times in the negative moment area on bridge decks. This study provided a reference for design and construction of super long-span continuous steel-concrete composite beam bridge.%针对连续钢-混叠合梁桥墩项区桥面板,在非荷载因素作用下受拉易产生裂缝,采用支座强迫位移法解决上述问题.为研究支座强迫位移法对叠合梁桥负弯矩区桥面板产生的预压应力效应,以武汉二七长江大桥汉口侧6×90m连续钢-混叠合梁桥为研究对象,对传统的支座强迫位移法进行了改进,同时利用ANSYS的APDL语言建立大型“梁-壳-实”有限元混合模型,并对其进行局部仿真分析和实测.理论和实测值均表明,改进的支座强迫位移在负弯矩区桥面板中产生了足够的预压应力储备,最大压应力大小为18.5 MPa.在
Cieślik Jerzy
2015-03-01
Full Text Available Rock samples can behave brittle, transitional or ductile depending on test pressure, rate of loading and temperature. Axial stiffness and its changes, relative and absolute dilatancy, yield, and fracture thresholds, residual strength are strongly pressure dependent. In this paper the stress drop as an effect of rock sample strength loss due to failure was analyzed. Uniaxial and triaxial experiments on three types of rock were performed to investigate the stress drop phenomenon. The paper first introduces short background on rock behavior and parameters defining a failure process under uniaxial and triaxial loading conditions. Stress drop data collected with experiments are analyzed and its pressure dependence phenomenon is described. Two methods for evaluation of stress drop value are presented.
Baek-Il Bae
2016-01-01
Full Text Available Although mechanical properties of concrete under uniaxial compression are important to design concrete structure, current design codes or other empirical equations have clear limitation on the prediction of mechanical properties. Various types of fiber-reinforced reactive powder concrete matrix were tested for making more usable and accurate estimation equations for mechanical properties for ultra high strength concrete. Investigated matrix has compressive strength ranged from 30 MPa to 200 MPa. Ultra high strength concrete was made by means of reactive powder concrete. Preventing brittle failure of this type of matrix, steel fibers were used. The volume fraction of steel fiber ranged from 0 to 2%. From the test results, steel fibers significantly increase the ductility, strength and stiffness of ultra high strength matrix. They are quantified with previously conducted researches about material properties of concrete under uniaxial loading. Applicability of estimation equations for mechanical properties of concrete was evaluated with test results of this study. From the evaluation, regression analysis was carried out, and new estimation equations were proposed. And these proposed equations were applied into stress-strain relation which was developed by previous research. Ascending part, which was affected by proposed equations of this study directly, well fitted into experimental results.
Anisotropy of Dynamic Compressive Properties of Non-Heat-Treating Cold-Heading-Quality Steel Bars
Kim, Hyunmin; Kang, Minju; Bae, Chul Min; Kim, Hyoung Seop; Lee, Sunghak
2014-01-01
In the current study, a non-heat-treating cold-heading-quality steel bar was fabricated by cold drawing of a rolled bar, and anisotropic mechanical properties of the as-rolled and cold-drawn bars were investigated by quasistatic and dynamic compressive tests of 0 deg (longitudinal)-, 45 deg-, and 90 deg (transverse)-orientation specimens. Under the dynamic compressive loading, the trend of strength variation was similar to that of the quasistatic compressive loading, while the strength level was considerably increased by the strain rate hardening effect. Stress-strain curves of the cold-drawn bar specimens showed the nearly same strain hardening behavior, irrespective of specimen orientation and strain rate, but the yield stress and compressive flow stress increased in the order of the 0 deg-, 90 deg-, and 45 deg-orientation specimens. In the 45 deg- and 90 deg-orientation specimens, the pearlite bands had the stronger resistance to the stress acting on the maximum shear stress plane than in the 0 deg-orientation specimens, thereby resulting in the higher strengths. In some dynamically compressed specimens, pearlite bands were dissolved to form bainitic microstructures. Locations of these bainitic microstructures were well matched with hemispherical-shaped heat-trap zones, which confirmed that bainitic microstructures were formed by the temperature rise occurring during the dynamic compressive loading.
Albertini, G.; Bruno, G.; Fiori, F.; Girardin, E.; Giuliani, A.; Quadrini, E.; Romani, F.
2000-03-01
Thermal austenitizing and tempering treatments are being developed in automotive industry to prevent crack initiation and propagation, especially in components where stress intensity factors influence the stress field and ultimately the fatigue life of the component. This is the case of crown gears, where the tooth root typically undergoes impulsive and very high loads which frequently cause cracking if tensile residual stresses are present at the surface. The sign reversal of these stresses is the aim of austenitizing and tempering treatments. In this work neutron diffraction measurements of residual stress (RS) on a UNI55Cr3 steel crown gear, carried out at HMI-BENSC , are presented. The sample was submitted to a new multi-frequency induction technique whose effectiveness was checked. Comparisons with X-ray measurements are shown, and RS measured by X-rays on a similar shot-peened sample are also mentioned. Experiments at HMI-BENSC have received financial support by the European Commission under the TMR/LSF Access Programme (contract no. ERBFMGE CT950060).
"Compressed" Compressed Sensing
Reeves, Galen
2010-01-01
The field of compressed sensing has shown that a sparse but otherwise arbitrary vector can be recovered exactly from a small number of randomly constructed linear projections (or samples). The question addressed in this paper is whether an even smaller number of samples is sufficient when there exists prior knowledge about the distribution of the unknown vector, or when only partial recovery is needed. An information-theoretic lower bound with connections to free probability theory and an upper bound corresponding to a computationally simple thresholding estimator are derived. It is shown that in certain cases (e.g. discrete valued vectors or large distortions) the number of samples can be decreased. Interestingly though, it is also shown that in many cases no reduction is possible.
2013-01-01
Background The aneurysm clip impact-compression model of spinal cord injury (SCI) is a standard injury model in animals that closely mimics the primary mechanism of most human injuries: acute impact and persisting compression. Its histo-pathological and behavioural outcomes are extensively similar to human SCI. To understand the distinct molecular events underlying this injury model we analyzed global mRNA abundance changes during the acute, subacute and chronic stages of a moderate to severe injury to the rat spinal cord. Results Time-series expression analyses resulted in clustering of the majority of deregulated transcripts into eight statistically significant expression profiles. Systematic application of Gene Ontology (GO) enrichment pathway analysis allowed inference of biological processes participating in SCI pathology. Temporal analysis identified events specific to and common between acute, subacute and chronic time-points. Processes common to all phases of injury include blood coagulation, cellular extravasation, leukocyte cell-cell adhesion, the integrin-mediated signaling pathway, cytokine production and secretion, neutrophil chemotaxis, phagocytosis, response to hypoxia and reactive oxygen species, angiogenesis, apoptosis, inflammatory processes and ossification. Importantly, various elements of adaptive and induced innate immune responses span, not only the acute and subacute phases, but also persist throughout the chronic phase of SCI. Induced innate responses, such as Toll-like receptor signaling, are more active during the acute phase but persist throughout the chronic phase. However, adaptive immune response processes such as B and T cell activation, proliferation, and migration, T cell differentiation, B and T cell receptor-mediated signaling, and B cell- and immunoglobulin-mediated immune response become more significant during the chronic phase. Conclusions This analysis showed that, surprisingly, the diverse series of molecular events that
Konstandinos G. Raptis
2012-01-01
Full Text Available Purpose of this study is the consideration of loading and contact problems encountered at rotating machine elements and especially at toothed gears. The later are some of the most commonly used mechanical components for rotary motion and power transmission. This fact proves the necessity for improved reliability and enhanced service life, which require precise and clear knowledge of the stress field at gear tooth. This study investigates the maximum allowable stresses occurring during spur gear tooth meshing computed using Niemannâs formulas at Highest Point of Single Tooth Contact (HPSTC. Gear material, module, power rating and number of teeth are considered as variable parameters. Furthermore, the maximum allowable stresses for maximum power transmission conditions are considered keeping the other parameters constant. After the application of Niemannâs formulas to both loading cases, the derived results are compared to the respective estimations of Finite Element Method (FEM using ANSYS software. Comparison of the results derived from Niemannâs formulas and FEM show that deviations between the two methods are kept at low level for both loading cases independently of the applied power (either random or maximum and the respective tangential load.
Nichols, Thomas C.
1983-01-01
Two modified and calibrated U.S. Geological Survey 3-D borehole probes were successfully tested in the field at a site on South Table Mountain, near Golden, Colo. The probes were installed in separate core holes at depths of 84 and 99 cm in the latite cap rock and subsequently stress relieved with overcoring techniques. The determined stresses from both probes are very low and contain both tensile and compressive components. Magnitudes range from 1196 KPa in tension to 832 KPa in compression. The principal stress orientations are in fair agreement whereas the horizontal secondary principal stress directions are in good agreement; the maximum horizontal compressive stress is oriented N. 76? W.-S. 76? E. for one probe and N. 63? W.-S. 63? E. for the second probe. The greatest determined Young's modulus of the rock is in the N. 89? E. direction, only 15? from the maximum horizontal compressive stress direction.
Ultrasound beamforming using compressed data.
Li, Yen-Feng; Li, Pai-Chi
2012-05-01
The rapid advancements in electronics technologies have made software-based beamformers for ultrasound array imaging feasible, thus facilitating the rapid development of high-performance and potentially low-cost systems. However, one challenge to realizing a fully software-based system is transferring data from the analog front end to the software back end at rates of up to a few gigabits per second. This study investigated the use of data compression to reduce the data transfer requirements and optimize the associated trade-off with beamforming quality. JPEG and JPEG2000 compression techniques were adopted. The acoustic data of a line phantom were acquired with a 128-channel array transducer at a center frequency of 3.5 MHz, and the acoustic data of a cyst phantom were acquired with a 64-channel array transducer at a center frequency of 3.33 MHz. The receive-channel data associated with each transmit event are separated into 8 × 8 blocks and several tiles before JPEG and JPEG2000 data compression is applied, respectively. In one scheme, the compression was applied to raw RF data, while in another only the amplitude of baseband data was compressed. The maximum compression ratio of RF data compression to produce an average error of lower than 5 dB was 15 with JPEG compression and 20 with JPEG2000 compression. The image quality is higher with baseband amplitude data compression than with RF data compression; although the maximum overall compression ratio (compared with the original RF data size), which was limited by the data size of uncompressed phase data, was lower than 12, the average error in this case was lower than 1 dB when the compression ratio was lower than 8.
Zaretsky, E. B.; Kanel, G. I.
2016-09-01
The evolution of elastic-plastic shock waves has been studied in pure molybdenum and niobium at normal and elevated temperatures over propagation distances ranging from 0.03 to 5 mm. The experiments revealed that annealing of the metals substantially increases their Hugoniot elastic limits and, to a lesser degree, their spall strengths. Variations in the resistance of both the metals to fracture in tension with the test temperature can be described as modest. Measuring the decay of the elastic precursor waves with a propagation distance in the two metals has allowed a determining of the relationships between a flow stress τ and an initial plastic strain rate γ˙ p . It was found that, at the plastic strain rates greater than 3 ÷4 ×104s-1 , the temperature sensitivity of the transient values of τ is much lower than that at the strain rates below this range. The τ(γ˙ p ) data normalized on shear moduli of the metals have been approximated by simple functions that, despite substantial differences between the moduli and yield stresses, were found to be virtually identical for the two metals.
Dynamic compressive properties of bovine knee layered tissue
Nishida, Masahiro; Hino, Yuki; Todo, Mitsugu
2015-09-01
In Japan, the most common articular disease is knee osteoarthritis. Among many treatment methodologies, tissue engineering and regenerative medicine have recently received a lot of attention. In this field, cells and scaffolds are important, both ex vivo and in vivo. From the viewpoint of effective treatment, in addition to histological features, the compatibility of mechanical properties is also important. In this study, the dynamic and static compressive properties of bovine articular cartilage-cancellous bone layered tissue were measured using a universal testing machine and a split Hopkinson pressure bar method. The compressive behaviors of bovine articular cartilage-cancellous bone layered tissue were examined. The effects of strain rate on the maximum stress and the slope of stress-strain curves of the bovine articular cartilage-cancellous bone layered tissue were discussed.
Stress engineering for the design of morphotropic phase boundary in piezoelectric material
Ohno, Tomoya, E-mail: ohno@mail.kitami-it.ac.jp [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Yanagida, Hiroshi; Maekawa, Kentaroh [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan); Arai, Takashi; Sakamoto, Naonori; Wakiya, Naoki; Suzuki, Hisao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johoku, Hamamatsu, Shizuoka 432-8561 (Japan); Satoh, Shigeo [Graduate School of Science and Engineering, Ibaragi University, 4-12-1 Nakanarusawa-cho, Hitachi, Ibaragi 316-0033 (Japan); Matsuda, Takeshi [Department of Materials Science, Kitami Institute of Technology, 165 Kouen-cho, Kitami 090-8507 (Japan)
2015-06-30
Alkoxide-derived lead zirconate titanate thin films having Zr/Ti = 50/50 to 60/40 compositions with different residual stress conditions were deposited on a Si wafer to clarify the effects of the residual stress on the morphotropic phase boundary shift. The residual stress condition was controlled to − 0.1 to − 0.9 GPa by the design of the buffer layer structure on the Si wafer. Results show that the maximum effective piezoelectric constant d{sub 33} was obtained at 58/42 composition under − 0.9 GPa compressive residual stress condition. Moreover, the MPB composition shifted linearly to Zr-rich phase with increasing compressive residual stress. - Highlights: • The residual stress in lead zirconate titanate film on silicon was controlled. • The maximum residual stress in lead zirconate titanate film was − 0.9 GPa. • The morphotropic phase boundary shifted to zirconium rich phase by the strain.
Stress perturbation associated with the Amazonas and other ancient continental rifts
Zoback, Mary Lou; Richardson, Randall M.
1996-03-01
The state of stress in the vicinity of old continental rifts is examined to investigate the possibility that crustal structure associated with ancient rifts (specifically a dense rift pillow in the lower crust) may modify substantially the regional stress field. Both shallow (2.0-2.6 km depth) breakout data and deep (20-45 km depth) crustal earthquake focal mechanisms indicate a N to NNE maximum horizontal compression in the vicinity of the Paleozoic Amazonas rift in central Brazil. This compressive stress direction is nearly perpendicular to the rift structure and represents a ˜75° rotation relative to a regional E-W compressive stress direction in the South American plate. Elastic two-dimensional finite element models of the density structure associated with the Amazonas rift (as inferred from independent gravity modeling) indicate that elastic support of this dense feature would generate horizontal rift-normal compressional stresses between 60 and 120 MPa, with values of 80-100 MPa probably most representative of the overall structure. The observed ˜75° stress rotation constrains the ratio of the regional horizontal stress difference to the rift-normal compressive stress to be between 0.25 and 1.0, suggesting that this rift-normal stress may be from 1 to 4 times larger than the regional horizontal stress difference. A general expression for the modification of the normalized local horizontal shear stress (relative to the regional horizontal shear stress) shows that the same ratio of the rift-normal compression relative to the regional horizontal stress difference, which controls the amount of stress rotation, also determines whether the superposed stress increases or decreases the local maximum horizontal shear stress. The potential for fault reactivation of ancient continental rifts in general is analyzed considering both the local stress rotation and modification of horizontal shear stress for both thrust and strike-slip stress regimes. In the Amazonas
Jiang-Jun Zhou
2017-01-01
Full Text Available In this study, we developed and validated a refined three-dimensional finite element model of middle femoral comminuted fracture to compare the biomechanical stability after two kinds of plate fixation: a newly designed assembly locking compression plate (NALCP and a locking compression plate (LCP. CT data of a male volunteer was converted to middle femoral comminuted fracture finite element analysis model. The fracture was fixated by NALCP and LCP. Stress distributions were observed. Under slow walking load and torsion load, the stress distribution tendency of the two plates was roughly uniform. The anterolateral femur was the tension stress area, and the bone block shifted toward the anterolateral femur. Maximum stress was found on the lateral border of the number 5 countersink of the plate. Under a slow walking load, the NALCP maximum stress was 2.160e+03 MPa and the LCP was 8.561e+02 MPa. Under torsion load, the NALCP maximum stress was 2.260e+03 MPa and the LCP was 6.813e+02 MPa. Based on those results of finite element analysis, the NALCP can provide adequate mechanical stability for comminuted fractures, which would help fixate the bone block and promote bone healing.
Harrington, Joe [Sertco Industries, Inc., Okemah, OK (United States); Vazquez, Daniel [Hoerbiger Service Latin America Inc., Deerfield Beach, FL (United States); Jacobs, Denis Richard [Hoerbiger do Brasil Industria de Equipamentos, Cajamar, SP (Brazil)
2012-07-01
Over time, all wells experience a natural decline in oil and gas production. In gas wells, the major problems are liquid loading and low downhole differential pressures which negatively impact total gas production. As a form of artificial lift, wellhead compressors help reduce the tubing pressure resulting in gas velocities above the critical velocity needed to surface water, oil and condensate regaining lost production and increasing recoverable reserves. Best results come from reservoirs with high porosity, high permeability, high initial flow rates, low decline rates and high total cumulative production. In oil wells, excessive annulus gas pressure tends to inhibit both oil and gas production. Wellhead compression packages can provide a cost effective solution to these problems by reducing the system pressure in the tubing or annulus, allowing for an immediate increase in production rates. Wells furthest from the gathering compressor typically benefit the most from wellhead compression due to system pressure drops. Downstream compressors also benefit from higher suction pressures reducing overall compression horsepower requirements. Special care must be taken in selecting the best equipment for these applications. The successful implementation of wellhead compression from an economical standpoint hinges on the testing, installation and operation of the equipment. Key challenges and suggested equipment features designed to combat those challenges and successful case histories throughout Latin America are discussed below.(author)
Xenaki, Angeliki; Mosegaard, Klaus
2014-01-01
Sound source localization with sensor arrays involves the estimation of the direction-of-arrival (DOA) from a limited number of observations. Compressive sensing (CS) solves such underdetermined problems achieving sparsity, thus improved resolution, and can be solved efficiently with convex...
STUDY ON THE UNIAXIAL COMPRESSION STRESS-STRAIN CURVE OF ADOBE MASONRY%土坯砌体单轴受压应力-应变曲线试验研究
曹耿; 阿肯江.托呼提
2011-01-01
Compressive strength and stress-strain curve were investigated and probed by test of basic mechanical properties of adobe masonry. Based on experimental study and theoretical analysis, the fraction equation are put forward to simulate uniaxial compression stress-strain curve of adobe masonry, the uniaxial compression constitutive equation is established, the fitted value and specific physical meaning of parameters in constitutive equation is assigned. These works can also provide parameters in order to analyse the seismic performance of adobe masonry houses.%通过对土坯砌体试件进行基本力学性能试验,就其抗压强度及应力-应变关系进行了研究和探讨,在试验研究与理论分析的基础上采用分式方程拟合了土坯砌体单轴受压应力-应变曲线,建立其单轴受压本构方程,给出了本构方程中参数的拟合值和明确的物理意义,研究成果可为土坯砌体房屋抗震性能分析提供参考.
Baek-Il Bae; Hyun-Ki Choi; Bong-Seop Lee; Chang-Hoon Bang
2016-01-01
Although mechanical properties of concrete under uniaxial compression are important to design concrete structure, current design codes or other empirical equations have clear limitation on the prediction of mechanical properties. Various types of fiber-reinforced reactive powder concrete matrix were tested for making more usable and accurate estimation equations for mechanical properties for ultra high strength concrete. Investigated matrix has compressive strength ranged from 30 MPa to 200 M...
Baek-Il Bae; Hyun-Ki Choi; Bong-Seop Lee; Chang-Hoon Bang
2016-01-01
Although mechanical properties of concrete under uniaxial compression are important to design concrete structure, current design codes or other empirical equations have clear limitation on the prediction of mechanical properties. Various types of fiber-reinforced reactive powder concrete matrix were tested for making more usable and accurate estimation equations for mechanical properties for ultra high strength concrete. Investigated matrix has compressive strength ranged from 30 MPa to 200 M...
Dong, Haini; He, Duanwei; Duffy, Thomas S.; Zhao, Yusheng
2009-01-01
The stress behavior of nanocrystalline cubic boron carbon nitride (c-BC2N) was investigated using radial and axial x-ray diffractions in the diamond-anvil cell under nonhydrostatic compression up to ~100 GPa. The radial x-ray diffraction (RXRD) data yield a bulk modulus K0=276±20GPa with a fixed pressure derivative K0'=3.4 at ψ=54.7° , which corresponds to the hydrostatic compression curve. The bulk modulus obtained from axial x-ray diffraction (AXRD) gives a value of 420±11GPa . A comparative study of the observed compression curves from radial and axial diffractions shows that the ruby-fluorescence pressure scale may reflect the maximum stress under nonhydrostatic compression. It was found that nanocrystalline c-BC2N sample could support a maximum differential stress of ~38 GPa when it started to yield at ~66 GPa under uniaxial compression. Moreover, the aggregate elastic moduli of the nanocrystalline c-BC2N have been determined from the RXRD data at high pressures.
... diabetes. Shopdiabetes.org: Your Stress-Free System for Family Dinners! - 2017-03-book-oclock-scramble.html Shopdiabetes.org Your Stress-Free System for Family Dinners! A year of delicious meals to help prevent ...
... sudden negative change, such as losing a job, divorce, or illness Traumatic stress, which happens when you ... stress, so you can avoid more serious health effects. NIH: National Institute of Mental Health
Changes in internal stress distributions during yielding of square prismatic gold nano-specimens
Batra, R.C., E-mail: rbatra@vt.edu [Department of Engineering Science and Mechanics, M/C 0219, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Pacheco, A.A. [Universidad del Norte, Department of Mechanical Engineering, Barranquilla (Colombia)
2010-05-15
We use molecular statics simulations with the tight-binding potential to analyze stress evolution in nanosize square prismatic gold specimens of different aspect ratios (length/width) deformed in either simple tension/compression or tension/compression. In the former case atoms on end faces are displaced axially but are free to move laterally, and in the latter case atoms on end faces are restrained from moving laterally during their axial displacement. It is found that the stress distribution in the unloaded reference configuration is non-uniform, and it satisfies the local and the global equilibrium equations. Large values of the von Mises stress and the maximum shear stress occur on atoms located at the third layer beneath the traction free surfaces forming different patterns for specimens loaded in tension and compression. The specimen is assumed to yield when its total strain energy drops noticeably. Maximum values of the von Mises stress and the maximum shear stress at yielding are essentially independent of specimen's length for specimens deformed in tension. For specimens deformed in compression, wave-like patterns of stresses along the axial centroidal axis are observed when the specimen yields.
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from...
Establishment of Maximum Voluntary Compressive Neck Tolerance Levels
2011-07-01
Bridges Casey Pirnstill Chris Burneka John Plaga Grant Roush Biosciences and Performance Division Vulnerability Analysis Branch July 2011...S) Michael Cote, John Buhrman, Nathaniel Bridges, Casey Pirnstill, Chris Burneka, John Plaga , Grant Roush 5d. PROJECT NUMBER OSMS 5e. TASK
Advances in compressible turbulent mixing
Dannevik, W.P.; Buckingham, A.C.; Leith, C.E. [eds.
1992-01-01
This volume includes some recent additions to original material prepared for the Princeton International Workshop on the Physics of Compressible Turbulent Mixing, held in 1988. Workshop participants were asked to emphasize the physics of the compressible mixing process rather than measurement techniques or computational methods. Actual experimental results and their meaning were given precedence over discussions of new diagnostic developments. Theoretical interpretations and understanding were stressed rather than the exposition of new analytical model developments or advances in numerical procedures. By design, compressibility influences on turbulent mixing were discussed--almost exclusively--from the perspective of supersonic flow field studies. The papers are arranged in three topical categories: Foundations, Vortical Domination, and Strongly Coupled Compressibility. The Foundations category is a collection of seminal studies that connect current study in compressible turbulent mixing with compressible, high-speed turbulent flow research that almost vanished about two decades ago. A number of contributions are included on flow instability initiation, evolution, and transition between the states of unstable flow onset through those descriptive of fully developed turbulence. The Vortical Domination category includes theoretical and experimental studies of coherent structures, vortex pairing, vortex-dynamics-influenced pressure focusing. In the Strongly Coupled Compressibility category the organizers included the high-speed turbulent flow investigations in which the interaction of shock waves could be considered an important source for production of new turbulence or for the enhancement of pre-existing turbulence. Individual papers are processed separately.
Maximum stellar iron core mass
F W Giacobbe
2003-03-01
An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is signiﬁcantly different from a more typical Chandrasekhar mass limit approach. This technique produced a maximum stellar iron core mass value of 2.69 × 1030 kg (1.35 solar masses). This mass value is very near to the typical mass values found for neutron stars in a recent survey of actual neutron star masses. Although slightly lower and higher neutron star masses may also be found, lower mass neutron stars are believed to be formed as a result of enhanced iron core compression due to the weight of non-ferrous matter overlying the iron cores within large stars. And, higher mass neutron stars are likely to be formed as a result of fallback or accretion of additional matter after an initial collapse event involving an iron core having a mass no greater than 2.69 × 1030 kg.
Compressive behavior of fine sand.
Martin, Bradley E. (Air Force Research Laboratory, Eglin, FL); Kabir, Md. E. (Purdue University, West Lafayette, IN); Song, Bo; Chen, Wayne (Purdue University, West Lafayette, IN)
2010-04-01
The compressive mechanical response of fine sand is experimentally investigated. The strain rate, initial density, stress state, and moisture level are systematically varied. A Kolsky bar was modified to obtain uniaxial and triaxial compressive response at high strain rates. A controlled loading pulse allows the specimen to acquire stress equilibrium and constant strain-rates. The results show that the compressive response of the fine sand is not sensitive to strain rate under the loading conditions in this study, but significantly dependent on the moisture content, initial density and lateral confinement. Partially saturated sand is more compliant than dry sand. Similar trends were reported in the quasi-static regime for experiments conducted at comparable specimen conditions. The sand becomes stiffer as initial density and/or confinement pressure increases. The sand particle size become smaller after hydrostatic pressure and further smaller after dynamic axial loading.
Axial residual stresses in boron fibers
Behrendt, D. R.
1978-01-01
A method of measuring axial residual stresses in boron fibers is presented. With this method, the axial residual stress distribution as a function of radius is determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diam fibers are similar, being compressive at the surface and changing monotonically to a region of tensile stress within the boron. At approximately 25% of the original radius, the stress reaches a maximum tensile stress of about 860 MN sq m and then decreases to a compressive stress near the tungsten boride core. Data are presented for 203-micron diam B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102-micron diam B/W and boron on carbon (B/C) show that the residual stresses are similar in the outer regions of the fibers, but that large differences near and in the core are observed. Fracture of boron fibers is discussed.
Relation Between Residual and Hoop Stresses and Rolling Bearing Fatigue Life
Oswald, Fred B.; Zaretsky, Erwin V.; Poplawski, Joseph V.
2015-01-01
Rolling-element bearings operated at high speed or high vibration may require a tight interference fit between the bore of the bearing and shaft to prevent rotation of the bearing bore around the shaft and fretting damage at the interfaces. Previous work showed that the hoop stresses resulting from tight interference fits can reduce bearing lives by as much as 65 percent. Where tight interference fits are required, case-carburized steel such as AISI 9310 or M50 NiL is often used because the compressive residual stresses inhibit subsurface crack formation and the ductile core inhibits inner-ring fracture. The presence of compressive residual stress and its combination with hoop stress also modifies the Hertz stress-life relation. This paper analyzes the beneficial effect of residual stresses on rolling-element bearing fatigue life in the presence of high hoop stresses for three bearing steels. These additional stresses were superimposed on Hertzian principal stresses to calculate the inner-race maximum shearing stress and the resulting fatigue life of the bearing. The load-life exponent p and Hertz stress-life exponent n increase in the presence of compressive residual stress, which yields increased life, particularly at lower stress levels. The Zaretsky life equation is described and is shown to predict longer bearing lives and greater load- and stress-life exponents, which better predicts observed life of bearings made from vacuum-processed steel.
Deformation Curve Characteristics of Rapeseeds and Sunflower Seeds Under Compression Loading
Divišová M.
2014-09-01
Full Text Available The deformation curve characteristics of rapeseeds and sunflower seeds compressed using the equipment ZDM 50-2313/56/18 and varying vessel diameters (40, 60, 80, and 100 mm were investigated. Maximum compressive force of 100 kN was applied on bulk oilseeds of rape and sunflower of measured height 20-80 mm and deformed at a speed of 60 mm∙min-1. The compression test using the vessel diameters of 40 and 60 mm showed a serration effect while the vessel diameters of 80 and 100 mm indicated an increasing function effect on the force-deformation characteristic curves. Clearly, the increasing function effect described the region with oil flow and that of serration effect described the region without any oil flow. However, it was observed that the serration effect could be due to the higher compressive stress inside the smaller vessel diameters (40 and 60 mm compared to those with bigger vessel diameters (80 and 100 mm. Parameters such as deformation, deformation energy, and energy density were determined from the force-deformation curves dependency showing both increasing function and serration effect. The findings of the study provide useful information for the determination of specific compressive force and energy requirements for extracting maximum oil from oilseed crops such as rape and sunflower.
加劲肋对轴心受压圆管柱脚应力的影响%The Influence of Stiffening Rib on Axial Compression Round String Stress
张向红
2014-01-01
Exposed column base is applied most frequently in al forms of column foot, and the calculation of column foot motherboard has become a critical problem. According to the different forms of stif ening rib, this paper compares the stress of axial compression string round feet, analyzes the effect of stif eners on the heel stress.%外露式柱脚是在所有柱脚形式中应用得最多的一种，柱脚底板的计算就成为一个至关重要的问题。本文针对不同的加劲肋形式，对轴心受压圆管柱脚的应力进行对比，分析加劲肋对柱脚应力的影响。
Dual compression is not an uncommon type of iliac vein compression syndrome.
Shi, Wan-Yin; Gu, Jian-Ping; Liu, Chang-Jian; Lou, Wen-Sheng; He, Xu
2017-03-13
Typical iliac vein compression syndrome (IVCS) is characterized by compression of left common iliac vein (LCIV) by the overlying right common iliac artery (RCIA). We described an underestimated type of IVCS with dual compression by right and left common iliac arteries (LCIA) simultaneously. Thirty-one patients with IVCS were retrospectively included. All patients received trans-catheter venography and computed tomography (CT) examinations for diagnosing and evaluating IVCS. Late venography and reconstructed CT were used for evaluating the anatomical relationship among LCIV, RCIA and LCIA. Imaging manifestations as well as demographic data were collected and evaluated by two experienced radiologists. Sole and dual compression were found in 32.3% (n = 10) and 67.7% (n = 21) of 31 patients respectively. No statistical differences existed between them in terms of age, gender, LCIV diameter at the maximum compression point, pressure gradient across stenosis, and the percentage of compression level. On CT and venography, sole compression was commonly presented with a longitudinal compression at the orifice of LCIV while dual compression was usually presented as two types: one had a lengthy stenosis along the upper side of LCIV and the other was manifested by a longitudinal compression near to the orifice of external iliac vein. The presence of dual compression seemed significantly correlated with the tortuous LCIA (p = 0.006). Left common iliac vein can be presented by dual compression. This type of compression has typical manifestations on late venography and CT.
杨平; 赵玉涛; 王安东; 缪栋; 陈刚; 何毅
2012-01-01
The flow stress behavior of the delta-processed Inconel 718 superalloy was investigated by the hot compression on Gleeble-3500 test machine. The results of the thermal simulation compression tests show that the flow stress is positively sensitive to the strain rate and the deformation temperature. The peak stress decreases with the decreasing strain rate and increasing deformation temperature. The dynamic recrystallization is the main softening mechanism of the hot deformation of the delta-processed Inconel 718 superalloy. The activation energy (0 of the delta-processed S phase aged Inconel 718 superalloy is 497.407 kJ/mol. The relationships among the flow stress, the deformation temperature and the strain rate for the delta-processed Inconel 718 can be described by the hyperbolic sine-type function.%在Gleeble-3500热模拟实验机上对Delta工艺Inconel 718合金进行高温压缩实验,研究其高温压缩变形的流变应力行为.结果表明:δ相时效态Inconel 718合金在本实验条件下具有正的应变速率敏感性,流变应力随着应变速率的降低和变形温度的升高而减小,动态再结晶是合金重要的软化机制.δ相时效态Inconel 718合金的热变形激活能为497.407kJ/mol,高温压缩峰值流变应力与变形温度和应变速率的关系可用双曲正弦函数表示.
Poblano-Salas, C.A., E-mail: carlos.poblano@ciateq.m [CIATEQ A.C., Centro de Tecnologia Avanzada, Av. Manantiales 23 A, Parque Industrial Bernardo Quintana, El Marques, Queretaro, C.P. 76246 (Mexico); Barceinas-Sanchez, J.D.O., E-mail: obarceinas@ipn.m [CICATA-IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Cerro Blanco 141, Colinas del Cimatario, Santiago de Queretaro, Queretaro, C.P. 76090 (Mexico)
2009-10-19
Stress relaxation testing in compression at high temperature was performed on Cu-Cr-Zr alloys produced by consolidation of water atomized powders. Precipitation and recrystallization were monitored during stress relaxation experiments carried out at an ageing temperature of 723 K. Pre-straining imposed to the Cu-Cr-Zr samples prior to stress relaxation testing resulted in reduced hardness compared to that reported for conventionally-aged alloys; it also resulted in shorter times for achieving maximum strengthening on ageing.
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Keller, Hanne Dauer
2015-01-01
Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb.......Kapitlet handler om stress som følelse, og det trækker primært på de få kvalitative undersøgelser, der er lavet af stressforløb....
Two-way Shape Memory Effect of NiTi under Compressive Loading Cycles
Yoo, Young Ik; Lee, Jung Ju
In this study, the two-way shape memory effect (TWSME) of a Ni-54.5 at.% Ti alloy was investigated experimentally to develop a NiTi linear actuator. The two-way shape memory effect was induced through a compressive shape memory cycle composed of four steps: (1) loading to maximum deformation; (2) unloading; (3) heating; (4) and cooling. Six types of specimens (one solid cylindrical and five tubular) were used to obtain the twoway shape memory strain and two-way recovery stress and to evaluate the actuating capacity. The two-way actuating strain showed a convergent tendency after several training cycles for the same maximum deformation. A maximum value of the two-way strain was obtained for 7% of maximum deformation, independently of the geometry of the tubular specimens. The two-way strains obtained by the shape memory cycles and two-way recovery stress linearly increase as a function of the maximum deformation and the two-way strain, respectively, and the geometry of specimen affects the two-way recovery stress. Although the results show that sufficient recovery stress can be generated by either the two-way shape memory process or by the one-way shape memory process, the two-way shape memory process can be applied more conveniently to actuating applications.
Stress wave emission from plasmonic nanobubbles
Brujan, Emil-Alexandru
2017-01-01
Stress wave emission from the collapse of cavitation nanobubbles, generated after irradiation of single-spherical gold nanoparticles with laser pulses, was investigated numerically. The significant parameters of this study are the nanoparticle radius, laser pulse duration, and laser fluence. For conditions comparable to those existing during plasmonic photothermal therapy, a purely compressive pressure wave is emitted during nanobubble collapse, not a shock. In the initial stage of its propagation, the stress wave amplitude is proportional to the inverse of the stress wave radius. The maximum amplitude and the duration of the stress wave decreases with the laser fluence, laser pulse duration, and gold nanoparticle radius. The full width at half maximum duration of the stress wave is almost constant up to a distance of 50 µm from the emission center. The stress wave amplitude is smaller than 5 MPa, while the stress wave duration is smaller than 35 ns. The stress wave propagation results in minor mechanical effects on biological tissue that are restricted to very small dimensions on a cellular or sub-cellular level. The stress wave is, however, able to produce breaching of the human cell membrane and bacterial wall even at distances as large as 50 µm from the emission centre. The experimentally observed melting of gold nanoparticles comes from the large temperature reached inside the nanoparticles during laser irradiation and not from the propagation of the stress wave into the surrounding liquid during nanobubble rebound.
Compressive Sensing Over Networks
Feizi, Soheil; Effros, Michelle
2010-01-01
In this paper, we demonstrate some applications of compressive sensing over networks. We make a connection between compressive sensing and traditional information theoretic techniques in source coding and channel coding. Our results provide an explicit trade-off between the rate and the decoding complexity. The key difference of compressive sensing and traditional information theoretic approaches is at their decoding side. Although optimal decoders to recover the original signal, compressed by source coding have high complexity, the compressive sensing decoder is a linear or convex optimization. First, we investigate applications of compressive sensing on distributed compression of correlated sources. Here, by using compressive sensing, we propose a compression scheme for a family of correlated sources with a modularized decoder, providing a trade-off between the compression rate and the decoding complexity. We call this scheme Sparse Distributed Compression. We use this compression scheme for a general multi...
Compression limits in cascaded quadratic soliton compression
Bache, Morten; Bang, Ole; Krolikowski, Wieslaw;
2008-01-01
Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency.......Cascaded quadratic soliton compressors generate under optimal conditions few-cycle pulses. Using theory and numerical simulations in a nonlinear crystal suitable for high-energy pulse compression, we address the limits to the compression quality and efficiency....
Huang, Bormin
2011-01-01
Satellite Data Compression covers recent progress in compression techniques for multispectral, hyperspectral and ultra spectral data. A survey of recent advances in the fields of satellite communications, remote sensing and geographical information systems is included. Satellite Data Compression, contributed by leaders in this field, is the first book available on satellite data compression. It covers onboard compression methodology and hardware developments in several space agencies. Case studies are presented on recent advances in satellite data compression techniques via various prediction-
Characteristics of recent tectonic stress field in Jiashi, Xinjiang and adjacent regions
CUI Xiao-feng
2006-01-01
In this paper, we analyze the general directional features of regional tectonic stress field in Jiashi, Xinjiang and adjacent regions from the data of focal mechanism solutions, borehole breakouts and fault slip. The direction of maximum horizontal principal stress given by these three sorts of stress data differs slightly, which indicates there is a NS-trending horizontal compression in the tectonic stress field in the region of interest. We also invert and analyze the temporal and spatial changes of recent tectonic stress field in the research region by using 137 focal mechanism solutions. The inverted results show that the maximum principal stress σ1 in Jiashi and adjacent regions is NNW-SSE with an azimuth of 162°. In the period from 1997 to 2003 before the occurrence of Jiashi-Bachu earthquake, the directions of the maximum principal stress σ1 and the minimum principal stress σ3 in Jiashi seismic source zone changed clockwise with respect to the tectonic stress field in the regions around. The maximum principal stress σ1 adjusted to the direction of NNE-SSW with an azimuth of 25°. Under the control of this tectonic stress field, a series of earthquakes happened, including the Jiashi strong earthquake swarm in 1997.Then, the tectonic stress field in the Jiashi seismic source zone might adjust again. And the tectonic stress field controlling the Jiashi-Bachu earthquake in 2003 was in accordance with the regions around.
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.; Steenfelt, Agnete
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from an ordinary non-spatial factor analysis, and they are interpreted in a geological context. It is demonstrated that MAF analysis contrary to ordinary non-spatial factor analysis gives an objective discrimina...
Jensen, Line Skov; Lova, Lotte; Hansen, Zandra Kulikovsky; Schønemann, Emilie; Larsen, Line Lyngby; Colberg Olsen, Maria Sophia; Juhl, Nadja; Magnussen, Bogi Roin
2012-01-01
Stress er en tilstand som er meget omdiskuteret i samfundet, og dette besværliggør i en vis grad konkretiseringen af mulige løsningsforslag i bestræbelsen på at forebygge den såkaldte folkesygdom. Hovedkonklusionen er, at selv om der bliver gjort meget for at forebygge, er der ikke meget der aktivt kan sættes i værk for at reducere antallet af stressramte, før en fælles forståelse af stressårsager og effektiv stresshåndtering er fremlagt. Problemformuleringen er besvaret gennem en undersø...
Source mechanism of small-moderate earthquakes and tectonic stress field in Yunnan Province
吴建平; 明跃红; 王椿镛
2004-01-01
In the paper, source mechanisms of 33 small-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the Chuandian rhombic block have strike-slip mechanism. The orientations of maximum compressive stresses obtained from source mechanism are changed from NNW-SSN to NS in the areas from north to south of the block, and tensile stresses are mainly in ENE-WSW or NE-SE. In the eastern Tibetan Plateau, the orientations of maximum compressive stress radiate toward outside from the plateau, and the tensile stress orientations mostly parallel to arc structures. Near 28°N the orientations of both maximum compressive stress and tensile stress changed greatly, and the boundary seems to correspond to the southwestern extended line of Longmenshan fault. Outside of the Chuandian rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-moderate events presented in the paper is consistence with that of moderate-strong earthquakes determined by Harvard University, which means the source mechanism of small-moderate events can be used to study the tectonic stress field in this region.
STRESS ANALYSIS AND BURST PRESSURE DETERMINATION OF TWO LAYER COMPOUND PRESSURE VESSEL
HARERAM LOHAR
2013-02-01
Full Text Available Multilayer pressure vessel is designed to work under high-pressure condition. This paper introduces the stress analysis and the burst pressure calculation of a two-layer shrink fitted pressure vessel. In the shrink-fitting problems, considering long hollow cylinders, the plane strain hypothesis can be regarded as more natural. Generally hoops stress distribution is non-linear and sharply reduced toward the outer surface. By shrink fitting concentric shells towards the inner shells are placed in residual compression so that the initial compressive hoop stress must be relieved by internal pressure before hoop tensile stress are developed. Therefore the maximum hoop stress will be reduced, resulting more burst pressure. The analytical results of stress distribution and burst pressure is calculated and validated by ANSYS Workbench results.
E.J. Mammarella
2002-12-01
Full Text Available The stress-strain of samples deformed until failure and the relaxation response after 50% deformation of the initial height under constant stress were obtained. Uniaxial compression and stress-relaxation tests enabled satisfactory differentiation of the mechanical resistance of gels with different alginate and carrageenan concentrations. Higher values for initial force at the beginning of the relaxation test were associated with higher calcium uptake by the gels. An increment of failure stress during the uniaxial compression tests for higher concentration of calcium in the gel structure was also observed. The maximum amount of cation uptake was higher than the theoretical value for saturation of all the carboxylic groups available in alginate molecules due to structural rearrangements. Stress-relaxation tests indicated that the residual stress of the gel increased with kappa-carrageenan concentration.
Compressive Failure of Fibre Reinforced Materials
Jensen, Henrik Myhre
2003-01-01
Compressive failure of uni-directional fibre composites by the kink band mechanism is analysed taking into account effects of residual stresses. Two criteria for determining the strength of the composite material have been investigated: Kink band formation at a bifurcation stress in a composite...
Efficient compression of molecular dynamics trajectory files.
Marais, Patrick; Kenwood, Julian; Smith, Keegan Carruthers; Kuttel, Michelle M; Gain, James
2012-10-15
We investigate whether specific properties of molecular dynamics trajectory files can be exploited to achieve effective file compression. We explore two classes of lossy, quantized compression scheme: "interframe" predictors, which exploit temporal coherence between successive frames in a simulation, and more complex "intraframe" schemes, which compress each frame independently. Our interframe predictors are fast, memory-efficient and well suited to on-the-fly compression of massive simulation data sets, and significantly outperform the benchmark BZip2 application. Our schemes are configurable: atomic positional accuracy can be sacrificed to achieve greater compression. For high fidelity compression, our linear interframe predictor gives the best results at very little computational cost: at moderate levels of approximation (12-bit quantization, maximum error ≈ 10(-2) Å), we can compress a 1-2 fs trajectory file to 5-8% of its original size. For 200 fs time steps-typically used in fine grained water diffusion experiments-we can compress files to ~25% of their input size, still substantially better than BZip2. While compression performance degrades with high levels of quantization, the simulation error is typically much greater than the associated approximation error in such cases.
ZENG; Lianbo; TAN; Chengxuan; ZHANG; Mingli
2004-01-01
Through rock acoustic emission experiments and structural deformation analysis, the tectonic stages in Meso-Cenozoic in the Kuqa depression of the Tarim basin are firstly divided. Then, combining with rock magnetic fabric analysis and memory information, the distribution characteristics of tectonic stress field of every tectonic stage are quantificationally resumed. At the same time, according to the distribution relation of tectonic stress field of hydrocarbon formation stage by the finite element numerical simulation method and the known hydrocarbon reservoirs, the effects of tectonic stress field on hydrocarbon migration and accumulation are further analyzed. The Kuqa depression has mainly experienced six tectonic movements since Mesozoic. Except that the tectonic stress field of the Early Yanshan stage (208-135 Ma) showed northeast-southwest extensional stress field where the orientation of the maximum principal compressive stress (σ1) was northwest-southeast, the others were compressive stress field where the orientations of the maximum principal compressive stress (σ1) were near north-south. Along with the closure of the paleo-Tethys ocean, the Kuqa depression in the Indosinian stage (250-208 Ma) was in strong compressive circumstance with apparently big maximum principal stress (σ1) magnitude. Due to the equilibrium adjustment of interior Eurasia, the Kuqa depression in the Early Yanshan stage (208-135 Ma) was in weak extensional circumstance with apparently small maximum principal stress (σ1) magnitude. From the Late Yanshan stage (135-65 Ma) on, with a series of collision events occurring at the south edge of Eurasia, the Kuqa depression was in compressive circumstance again in which the maximum principal stress (σ1) magnitude was from small to big in turn. The Late Himalayan stage (2.6-0.7 Ma) was the main tectonic deformation stage with the biggest principal compressive stress (σ1) magnitude. Tectonic stress field plays a dominant role in
Fatigue Properties of Plain Concrete Under Triaxial Compressive Cyclic Loading
曹伟; 宋玉普; 刘海成
2004-01-01
Experiments were made on plain concrete subjected to triaxial static loading and constant-amplitude compressive fatigue loading with a constant lateral pressure in two directions. The initial confining pressure was O, 0. 1fc, 0.25fc andO. 4fc, respectively, for the static test, and 0. 1fc and 0.25fc for the fatigue test. Based on the triaxial compressive constitutive behavior of concrete, the inflexion of confining pressure evolution was chosen to be the fatigue damage criterion during the test. The rule of evolution of longitudinal maximum and minimum strains, longitudinal cyclic modulus and damage were recorded and analyzed. According to the Fardis-Chen criterion model and the concept of equivalent fatigue life and equivalent stress level, a unified S-N curve for multi-axial compressive fatigue loading was proposed. Thus, the fatigue strength factors for different fatigue loading cases can be obtained. The present investigation provides information for the fatigue design of concrete structures.
Rutqvist, J.; Kim, H. -M.; Ryu, D. -W.; Synn, J. -H.; Song, W. -K.
2012-02-01
We applied coupled nonisothermal, multiphase fluid flow and geomechanical numerical modeling to study the coupled thermodynamic and geomechanical performance of underground compressed air energy storage (CAES) in concrete-lined rock caverns. The paper focuses on CAES in lined caverns at relatively shallow depth (e.g., 100 m depth) in which a typical CAES operational pressure of 5 to 8 MPa is significantly higher than both ambient fluid pressure and in situ stress. We simulated a storage operation that included cyclic compression and decompression of air in the cavern, and investigated how pressure, temperature and stress evolve over several months of operation. We analyzed two different lining options, both with a 50 cm thick low permeability concrete lining, but in one case with an internal synthetic seal such as steel or rubber. For our simulated CAES system, the thermodynamic analysis showed that 96.7% of the energy injected during compression could be recovered during subsequent decompression, while 3.3% of the energy was lost by heat conduction to the surrounding media. Our geomechanical analysis showed that tensile effective stresses as high as 8 MPa could develop in the lining as a result of the air pressure exerted on the inner surface of the lining, whereas thermal stresses were relatively smaller and compressive. With the option of an internal synthetic seal, the maximum effective tensile stress was reduced from 8 to 5 MPa, but was still in substantial tension. We performed one simulation in which the tensile tangential stresses resulted in radial cracks and air leakage though the lining. This air leakage, however, was minor (about 0.16% of the air mass loss from one daily compression) in terms of CAES operational efficiency, and did not significantly impact the overall energy balance of the system. However, despite being minor in terms of energy balance, the air leakage resulted in a distinct pressure increase in the surrounding rock that could be
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and/or ...
Plastic Mechanisms for Thin-Walled Cold-Formed Steel Members in Eccentric Compression
Ungureanu Viorel
2016-03-01
Full Text Available The Eurocode 3 concerning thin-walled steel members divides members subjected to compression into four classes, considering their ductility. The representatives of the class C4 are short bars, for which the load-capacity corresponds to the maximum compression stresses less than the yield stress. There are bars prone to local buckling in the elastic range and they do not have a real post-elastic capacity. The failure at ultimate stage of such members, either in compression or bending, always occurs by forming a local plastic mechanism. This fact suggests the possibility to use the local plastic mechanism to characterise the ultimate strength of such members. The present paper is based on previous studies and some latest investigations of the authors, as well as the literature collected data. It represents an attempt to study the plastic mechanisms for members in eccentric compression about minor axis and the evolution of plastic mechanisms, considering several types of lipped channel sections.
Fabrication and compressive performance of plain carbon steel honeycomb sandwich panels
Yu'an Jing; Shiju Guo; Jingtao Han; Yufei Zhang; Weijuan Li
2008-01-01
Plain carbon steel Q215 honeycomb sandwich panels were manufactured by brazing in a vacuum furnace. Their characteristic parameters, including equivalent density, equivalent elastic modulus, and equivalent compressive strength along out-of-plane (z-direction) and in-plane (x- and y-directions), were derived theoretically and then determined experimentally by an 810 material test system. On the basis of the experimental data, the compressive stress-strain curves were given. The results indicate that the measurements of equivalent Young's modulus and initial compressive strength are in good agreement with calculations, and that the maximum compressive strain near to solid can be up to 0.5-0.6 along out-of-plane, 0.6-0.7 along in-plane. The strength-to-density ratio of plain carbon steel honeycomb panels is near to those of Al alloy hexagonal-honeycomb and 304L stainless steel square-honeycomb, but the compressive peak strength is greater than that of Al alloy hexagonal-honeycomb.
Compression of a bundle of light rays.
Marcuse, D
1971-03-01
The performance of ray compression devices is discussed on the basis of a phase space treatment using Liouville's theorem. It is concluded that the area in phase space of the input bundle of rays is determined solely by the required compression ratio and possible limitations on the maximum ray angle at the output of the device. The efficiency of tapers and lenses as ray compressors is approximately equal. For linear tapers and lenses the input angle of the useful rays must not exceed the compression ratio. The performance of linear tapers and lenses is compared to a particular ray compressor using a graded refractive index distribution.
Higgins, J.D.; Burger, P.A. [Colorado School of Mines, Golden, CO (United States); Yang, L.C. [Geological Survey, Denver, CO (United States)
1997-12-31
Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test.
Stress perturbation associated with the Amazonas and other ancient continental rifts
Zoback, M.L.; Richardson, R.M.
1996-01-01
The state of stress in the vicinity of old continental rifts is examined to investigate the possibility that crustal structure associated with ancient rifts (specifically a dense rift pillow in the lower crust) may modify substantially the regional stress field. Both shallow (2.0-2.6 km depth) breakout data and deep (20-45 km depth) crustal earthquake focal mechanisms indicate a N to NNE maximum horizontal compression in the vicinity of the Paleozoic Amazonas rift in central Brazil. This compressive stress direction is nearly perpendicular to the rift structure and represents a ???75?? rotation relative to a regional E-W compressive stress direction in the South American plate. Elastic two-dimensional finite element models of the density structure associated with the Amazonas rift (as inferred from independent gravity modeling) indicate that elastic support of this dense feature would generate horizontal rift-normal compressional stresses between 60 and 120 MPa, with values of 80-100 MPa probably most representative of the overall structure. The observed ???75?? stress rotation constrains the ratio of the regional horizontal stress difference to the rift-normal compressive stress to be between 0.25 and 1.0, suggesting that this rift-normal stress may be from 1 to 4 times larger than the regional horizontal stress difference. A general expression for the modification of the normalized local horizontal shear stress (relative to the regional horizontal shear stress) shows that the same ratio of the rift-normal compression relative to the regional horizontal stress difference, which controls the amount of stress rotation, also determines whether the superposed stress increases or decreases the local maximum horizontal shear stress. The potential for fault reactivation of ancient continental rifts in general is analyzed considering both the local stress rotation and modification of horizontal shear stress for both thrust and strike-slip stress regimes. In the Amazonas
Maximum information photoelectron metrology
Hockett, P; Wollenhaupt, M; Baumert, T
2015-01-01
Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are a high-information, coherent observable. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, 3D, photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyse the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral features, but also indicate unexpected symmetry-breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum information measurements of th...
Xie, Jun; Ihara, Maki; Jung, Youngmee; Kwon, Il Keun; Kim, Soo Hyun; Kim, Young Ha; Matsuda, Takehisa
2006-03-01
An essential component of functional articular cartilage tissue engineering is a mechano-active scaffold, which responds to applied compression stress and causes little permanent deformation. As the first paper of a series on mechano-active scaffold-based cartilage tissue engineering, this study focused on mechanical responses to various modes of loading of compression forces and subsequent selection of mechano-active scaffolds from the biomechanical viewpoint. Scaffolds made of elastomeric microporous poly(L-lactide-co-epsilon-caprolactone) (PLCL) with open-cell structured pores (300 approximately 500 microm) and with different porosities ranging from 71 to 86% were used. The PLCL sponges and rabbit articular cartilage tissue were subjected to compression/unloading tests (0.1 and 0.005 Hz) at 5 kPa, and stress relaxation tests at 10, 30, and 50% strain. The measurements of the maximum strain under loading and residual strain under unloading for compression tests and the maximum stress and equilibrium stress in the stress relaxation test showed that the lower the porosity, the closer the mechanical properties are to those of native cartilage tissue. Among the PLCL sponges, the sponge with 71% porosity appears to be a suitable cartilage scaffold.
Tectonic stress within the New Madrid seismic zone
Grana, Jeffrey P.; Richardson, Randall M.
1996-03-01
Refraction data indicate a significant high-density rift pillow beneath the New Madrid seismic zone. We present results of linear and nonlinear viscoelastic finite element modeling to determine whether support of the rift pillow may contribute significantly to the total present-day stress field, and we consider the implications for intraplate seismicity. These models were run for a loading time of 100 m.y. to account for relaxation and transfer of stress since the last reactivation of the rift in the mid-Mesozoic. Results indicate that the nonlinear viscoelastic model with rheological stratification based on composition and temperature agrees well with the observed deformation within the seismic zone and with estimates of regional stress magnitudes. The model predicts a maximum compression of 30-40 MPa above the rift pillow in the center of the rift axis. If the magnitude of local compression predicted by the nonlinear model produces the inferred clockwise rotation of the order of 10°-30° in the direction of SHmax (maximum horizontal compression) near the rift axis, the magnitude of regional compression is a factor of 1 to 2 times the magnitude of local compression and consistent with an origin due to ridge push forces. The addition of the local stress associated with the rift pillow, however, results in an approximately 30% reduction in the resolved maximum horizontal shear stress. Thus, while the stress associated with the rift pillow can rotate the stress field into an orientation favorable for failure, reduction in the resolved shear stress requires a separate mechanism for strength reduction. Results of the modeling indicate that stresses from the load of the rift pillow may still be present in the upper crust even after 100 m.y. and may still play a role in present-day deformation and seismicity of the New Madrid seismic zone. Local stress fields of significant tectonic magnitudes may also occur around other ancient rift pillows and help explain the
Compressive Deformation Induced Nanocrystallization of a Supercooled Zr-Based Bulk Metallic Glass
GUO Xiao-Lin; SHAN De-Bin; MA Ming-Zhen; GUO Bin
2008-01-01
The nanocrystallization behaviour of a bulk Zr-based metallic glass subjected to compressive stress is investigated in the supercooled liquid region. Compared with annealing treatments without compressive stress, compressive deformation promotes the development of nucleation and suppresses the coarsening of nanocrystallites at high ternperatures.
Simulation of Compressive Failure in Fiber Composites
Veluri, Badrinath; Jensen, Henrik Myhre
Kinkband formation is a non-linear phenomenon involving interacting effects of non-linear material behavior of the matrix materials and fiber buckling including fiber misalignment in fiber composites under compressive loading. Taking into account the non-linearties of the constituents...... understanding of the influence of the macro-geometry and micro-geometry. In addition studying the mechanics of kinkband formation, focus is also directed in computing the critical compressive stress for steady state kinkband broadening under compression in the fiber direction. The present theory demonstrates...
王波; 陈东林; 周留成; 何卫锋
2014-01-01
纳秒脉冲、千兆瓦级激光辐照金属材料产生高压等离子体冲击波，作用于金属材料表面并向内传播，产生残余压应力场。但在单次冲击加载时，残余压应力场中心出现的残余压应力值小于加载边缘，应用理论分析和实验测试的方法解释了这一过程，并结合激光诱导冲击波Fabbro方程和TC4钛合金动态响应模型，建立了不同形式冲击波加载TC4钛合金的数值仿真模型，分析了冲击波压力、作用时间和加载形式对中心压应力缺失的影响。%The high pressure plasma shock wave induced by nanosecond pulse and 1 000 MW laser irradiation on the metal materials will propagate into the materials and impart residual compressive stresses. But when shock wave was singly loaded, the lower residual stress at the center of the loading zone compared to those away from the center will be induced. This process is proved by theorems and experiments. Moreover, the Fabbro equation of plasma shock wave and dynamic response of TC4 titanium alloy was calculated in the numerical model of different shock wave loading, the influence of the shock wave pressure, the actuation duration and the loading shape on residual stress drop at the center was discussed.
Compression Deformation Behavior of AZ81 Magnesium Alloy at Elevated Temperatures
Xiaoping Luo
2014-01-01
Full Text Available The hot deformation behavior of an AZ81 magnesium alloy was investigated by hot compressive testing on a Gleeble-1500 thermal mechanical simulator in the temperature range from 200 to 400°C and in the strain rate range of 0.001–5 s−1. The relationships among flow stress, strain rate, and deformation temperature were analyzed, and the deformation activation energy and stress exponent were calculated. The microstructure evolution of the AZ81 magnesium alloy under high deformation was examined. The results indicated that the maximum value of the flow stress increased with the decrease of deformation temperature and the increase of strain rate. When the deformation temperature is constant, the flow stress of the AZ81 magnesium alloy increases with the increase of strain rate, which can be demonstrated by a Zener-Hollomon parameter in a hyperbolic-sine-type equation with a hot compression deformation activation energy of 176.01 KJ/mol and basic hot deformation material factors A, n, and a in the analytical expression of the AZ81 magnesium alloy flow stress of 3.21227×1014 s−1, 7.85, and 0.00866 MPa, respectively.
Jikai Zhou; Xudong Chen; Longqiang Wu; Xiaowei Kan
2011-06-01
The effect of free water content upon the compressive mechanical behaviour of cement mortar under high loading rate was studied. The uniaxial rapid compressive loading testing of a total of 30 specimens, nominally 37 mm in diameter and 18.5 mm in height, with ﬁve different saturations (0%, 25%, 50%, 75% and 100%, respectively) were executed in this paper. The technique ‘Split Hopkinson pressure bar’ (SHPB) was used. The impact velocity was 10 m/s with the corresponding strain rate as 102/s. Water-cement ratio of 0.5 was used. The compressive behaviour of the materials was measured in terms of the maximum stress, Young’s modulus, critical strain at maximum stress and ultimate strain at failure. The data obtained from test indicates that the similarity exists in the shape of strain–stress curves of cement mortars with different water content, the upward section of the stress–strain curve shows bilinear characteristics, while the descending stage (softening state) is almost linear. The dynamic compressive strength of cement mortar increased with the decreasing of water content, the dynamic compressive strength of the saturated specimens was 23% lower than that of the totally dry specimens. With an increase in water content, the Young’s modulus ﬁrst increases and then decreases, the Young’s modulus of the saturated specimens was 23% lower than that of the totally dry specimens. No signiﬁcant changes occurred in the critical and ultimate strain value as the water content is changed.
Abbas, Musharaf; Hasham, Hasan Junaid; Baig, Yasir
2016-02-01
Numerical-based finite element investigation has been conducted to explain the effect of bond coat thickness on stress distribution in traditional and nanostructured yttria-stabilized zirconia (YSZ)-based thermal barrier coatings (TBC). Stress components have been determined to quantitatively analyze the mechanical response of both kinds of coatings under the thermal shock effect. It has been found that maximum radial tensile and compressive stresses that exist at thermally grown oxide (TGO)/bond coat interface and within TGO respectively decrease with an increase in bond coat thickness. Effect of bond coat thickness on axial tensile stresses is not significant. However, axial compressive stresses that exist at the edge of the specimen near bond coat/substrate interface decrease appreciably with the increase in bond coat thickness. Residual stress profile as a function of bond coat thickness is further explained for comparative analysis of both coatings to draw some useful conclusions helpful in failure studies of TBCs.
Maximum Likelihood Associative Memories
Gripon, Vincent; Rabbat, Michael
2013-01-01
Associative memories are structures that store data in such a way that it can later be retrieved given only a part of its content -- a sort-of error/erasure-resilience property. They are used in applications ranging from caches and memory management in CPUs to database engines. In this work we study associative memories built on the maximum likelihood principle. We derive minimum residual error rates when the data stored comes from a uniform binary source. Second, we determine the minimum amo...
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and....../or having different derivative orders. Although the principle is applicable to a wide variety of image models, the main focus here is on the Brownian model and its use for scale selection in natural images. Furthermore, in the examples provided, the simplifying assumption is made that the behavior...... of the measurements is completely characterized by all moments up to second order....
Hartl Christoph
2015-01-01
Full Text Available Feasible product geometries manufactured with micro-hydroforming, as well as process stability are crucially influenced by the microstructure of the used tube material. The higher ratio of grain size to tube wall thickness dk/t0 in micro-hydroforming, compared to conventional tube hydroforming, leads to an increase of scattering of process parameters and instabilities. This paper presents experimental and theoretical results for the micro-hydroforming of tubes made from stainless steel and from platinum with a focus on the correlations between the microstructure of the workpiece material, the stress state during forming and the resulting stability of the forming process. Investigated tube dimensions were 800 µm outer diameter and 40 µm wall thickness of the steel tubes, respectively 1650 µm and 76 µm of the platinum tubes. The average ratio dk/t0 was about 0.3 for the steel material and about 0.9 for the platinum alloy. It has been shown that superimposed axial stresses are suitable to reduce the restricting influence of an increased ratio dk/t0 and to improve the forming result as well as the process stability.
Focus on Compression Stockings
... the stocking every other day with a mild soap. Do not use Woolite™ detergent. Use warm water ... compression clothing will lose its elasticity and its effectiveness. Compression stockings last for about 4-6 months ...
A Compressive Superresolution Display
Heide, Felix
2014-06-22
In this paper, we introduce a new compressive display architecture for superresolution image presentation that exploits co-design of the optical device configuration and compressive computation. Our display allows for superresolution, HDR, or glasses-free 3D presentation.
Chloride permeability of concrete under static and repeated compressive loading
Saito, Mitsuru; Ishimori, Hiroshi [Kanazawa Inst. of Technology, Ishikawa (Japan)
1995-05-01
The chloride permeability of normal weight concrete subjected to static and repeated compressive loading was evaluated by using the AASHTO T277 test method. The results of concrete under static loading showed that the application of loads up to 90% of the ultimate strength had little effect on the chloride permeability. It was found from the results of concrete under repeated loading that load repetitions at the maximum stress levels of 60% or more caused the chloride permeability to increase significantly. The test results also indicated that the chloride permeability of concrete subjected to static and repeated loading increased at an increasing rate with its residual strain. The relation between the chloride permeability obtained and the cracking behavior of concrete previously reported was discussed.
Directional amorphization of boron carbide subjected to laser shock compression
Zhao, Shiteng; Kad, Bimal; Remington, Bruce A.; LaSalvia, Jerry C.; Wehrenberg, Christopher E.; Behler, Kristopher D.; Meyers, Marc A.
2016-10-01
Solid-state shock-wave propagation is strongly nonequilibrium in nature and hence rate dependent. Using high-power pulsed-laser-driven shock compression, unprecedented high strain rates can be achieved; here we report the directional amorphization in boron carbide polycrystals. At a shock pressure of 45˜50 GPa, multiple planar faults, slightly deviated from maximum shear direction, occur a few hundred nanometers below the shock surface. High-resolution transmission electron microscopy reveals that these planar faults are precursors of directional amorphization. It is proposed that the shear stresses cause the amorphization and that pressure assists the process by ensuring the integrity of the specimen. Thermal energy conversion calculations including heat transfer suggest that amorphization is a solid-state process. Such a phenomenon has significant effect on the ballistic performance of B4C.
Hot compression deformation behavior of the Mg-AI-Y-Zn magnesium alloy
FANG Xiya; YI Danqing; WANG Bin; WU Chunping; ZHANG Hong
2008-01-01
The hot deformation behavior of a Mg-Al-Y-Zn magnesium alloy was investigated by hot compressive testing on a Gleeble-1500 thermal simulator at the temperanging from 523 to 673 K with the swain rate varying from 0.001 to 1s-1.The relationships among flow stress,swain rate,and deformation temperature were analyzed,and the deformation activation energy and stress exponent were calculated.Microstructure evolution of the alloy under different conditions was examined.The results indicated that the maximum value of the flow stress increased with the decrease of deformation temperature or the increase of swain rate.Under the present deformation conditions,dynamic recrystallization (DRX) oeettrred in the alloy,which was the main softening mechanism during deformation at elevated temperature.The deformation temperature and strain had significant effects on the microstructure of the alloy.
Microbunching and RF Compression
Venturini, M.; Migliorati, M.; Ronsivalle, C.; Ferrario, M.; Vaccarezza, C.
2010-05-23
Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.
F. TopsÃƒÂ¸e
2001-09-01
Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over
Hyperspectral data compression
Motta, Giovanni; Storer, James A
2006-01-01
Provides a survey of results in the field of compression of remote sensed 3D data, with a particular interest in hyperspectral imagery. This work covers topics such as compression architecture, lossless compression, lossy techniques, and more. It also describes a lossless algorithm based on vector quantization.
Hildebrand, Richard J.; Wozniak, John J.
2001-01-01
A compressed gas storage cell interconnecting manifold including a thermally activated pressure relief device, a manual safety shut-off valve, and a port for connecting the compressed gas storage cells to a motor vehicle power source and to a refueling adapter. The manifold is mechanically and pneumatically connected to a compressed gas storage cell by a bolt including a gas passage therein.
Compressing Binary Decision Diagrams
Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter
2008-01-01
The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...
Compressing Binary Decision Diagrams
Rune Hansen, Esben; Srinivasa Rao, S.; Tiedemann, Peter
The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...
Compressing Binary Decision Diagrams
Hansen, Esben Rune; Satti, Srinivasa Rao; Tiedemann, Peter
2008-01-01
The paper introduces a new technique for compressing Binary Decision Diagrams in those cases where random access is not required. Using this technique, compression and decompression can be done in linear time in the size of the BDD and compression will in many cases reduce the size of the BDD to 1...
Regularized maximum correntropy machine
Wang, Jim Jing-Yan
2015-02-12
In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.
Luttrell, K. M.; Tong, X.; Sandwell, D. T.; Brooks, B. A.
2010-12-01
The great February 27, 2010 Mw 8.8 earthquake off the coast of southern Chile ruptured a 606 km length of subduction zone. In this study we make two independent estimates of shear stress in the crust in the region of the Chile earthquake. First, we use a coseismic slip model constrained by geodetic observations from InSAR and GPS to derive a spatially variable estimate of the change in static shear stress along the ruptured fault. Second, we use a static force balance model to constrain the crustal shear stress required to support observed accretionary wedge topography and the stress orientation indicated by the earthquake focal mechanism. This includes the derivation of a semi-analytic solution for the stress field exerted by surface and Moho topography loading the crust. We find that the deviatoric stress exerted by topography is minimized in the limit when the crust is considered an incompressible elastic solid, with a Poisson’s ratio of 0.5. This places a lower bound on the critical stress state maintained by the crust supporting plastically deformed accretionary wedge topography. We estimate the shear stress change from the Maule event ranged from -6 MPa (stress increase) to 14 MPa (stress drop), with a maximum depth-averaged shear stress drop of 4 MPa. We separately estimate that the plate driving forces acting in the region, regardless of their exact mechanism, must contribute at least 15 MPa trench-parallel compression, and trench-perpendicular compression must exceed trench-parallel compression by at least 12 MPa. This corresponds to a depth-averaged shear stress of at least 7 MPa. The comparable magnitude of these two independent shear stress estimates is consistent with the interpretation that the section of the megathrust fault ruptured in the Maule earthquake is weak, with the seismic cycle relieving much of the total sustained shear stress in the crust, and an equal portion of plate-driving stress being transmitted through the mantle.
Omeltchenko, Andrey; Bachlechner, Martina E.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya; Ebbsjö, Ingvar; Madhukar, Anupam; Messina, Paul
2000-01-01
Parallel molecular dynamics simulations are performed to determine atomic-level stresses in Si\\(111\\)/Si3N4\\(0001\\) and Si\\(111\\)/a-Si3N4 nanopixels. Compared to the crystalline case, the stresses in amorphous Si3N4 are highly inhomogeneous in the plane of the interface. In silicon below the interface, for a 25 nm square mesa stress domains with triangular symmetry are observed, whereas for a rectangular, 54 nm×33 nm, mesa tensile stress domains \\(~300 Å\\) are separated by Y-shaped compressive domain wall. Maximum stresses in the domains and domain walls are -2 GPa and +2 GPa, respectively.
Omeltchenko; Bachlechner; Nakano; Kalia; Vashishta; Ebbsjo; Madhukar; Messina
2000-01-10
Parallel molecular dynamics simulations are performed to determine atomic-level stresses in Si(111)/Si(3)N4(0001) and Si(111)/a-Si3N4 nanopixels. Compared to the crystalline case, the stresses in amorphous Si3N4 are highly inhomogeneous in the plane of the interface. In silicon below the interface, for a 25 nm square mesa stress domains with triangular symmetry are observed, whereas for a rectangular, 54 nmx33 nm, mesa tensile stress domains ( approximately 300 A) are separated by Y-shaped compressive domain wall. Maximum stresses in the domains and domain walls are -2 GPa and +2 GPa, respectively.
Equalized near maximum likelihood detector
2012-01-01
This paper presents new detector that is used to mitigate intersymbol interference introduced by bandlimited channels. This detector is named equalized near maximum likelihood detector which combines nonlinear equalizer and near maximum likelihood detector. Simulation results show that the performance of equalized near maximum likelihood detector is better than the performance of nonlinear equalizer but worse than near maximum likelihood detector.
Sun, Rujian; Li, Liuhe; Zhu, Ying; Zhang, Lixin; Guo, Wei; Peng, Peng; Li, Bo; Guo, Chao; Liu, Lei; Che, Zhigang; Li, Weidong; Sun, Jianfei; Qiao, Hongchao
2017-09-01
Laser shock peening (LSP), an innovative surface treatment technique, generates compressive residual stress on the surface of metallic components to improve their fatigue performance, wear resistance and corrosion resistance. To illustrate the dynamic response during LSP and residual stress fields after LSP, this study conducted FEM simulations of LSP in a Ti6Al4V alloy. Results showed that when power density was 7 GW cm-2, a plastic deformation occurred at 10 ns during LSP and increased until the shock pressure decayed below the dynamic yield strength of Ti6Al4V after 60 ns. A maximum tensile region appeared beneath the surface at around 240 ns, forming a compressive-tensile-compressive stress sandwich structure with a thickness of 98, 1020 and 606 μm for each layer. After the model became stabilized, the value of the surface residual compressive stress was 564 MPa at the laser spot center. Higher value of residual stress across the surface and thicker compressive residual stress layers were achieved by increasing laser power density, impact times and spot sizes during LSP. A ‘Residual stress hole’ occurred with a high laser power density of 9 GW cm-2 when laser pulse duration was 10 ns, or with a long laser pulse duration of 20 ns when laser power density was 7 GW cm-2 for Ti6Al4V. This phenomenon occurred because of the permanent reverse plastic deformation generated at laser spot center.
Cheeseman, Peter; Stutz, John
2005-01-01
A long standing mystery in using Maximum Entropy (MaxEnt) is how to deal with constraints whose values are uncertain. This situation arises when constraint values are estimated from data, because of finite sample sizes. One approach to this problem, advocated by E.T. Jaynes [1], is to ignore this uncertainty, and treat the empirically observed values as exact. We refer to this as the classic MaxEnt approach. Classic MaxEnt gives point probabilities (subject to the given constraints), rather than probability densities. We develop an alternative approach that assumes that the uncertain constraint values are represented by a probability density {e.g: a Gaussian), and this uncertainty yields a MaxEnt posterior probability density. That is, the classic MaxEnt point probabilities are regarded as a multidimensional function of the given constraint values, and uncertainty on these values is transmitted through the MaxEnt function to give uncertainty over the MaXEnt probabilities. We illustrate this approach by explicitly calculating the generalized MaxEnt density for a simple but common case, then show how this can be extended numerically to the general case. This paper expands the generalized MaxEnt concept introduced in a previous paper [3].
赵晓峰; 赵斌; 赵轶波; 陈祺; 王玲
2014-01-01
degeneration and cervical abnormal hgamentum flavum.Methods Specimens of 10 intact fresh cervical spine (C1-T1) from adult cadavers were collected in order to simulate cervical disc degeneration and abnormal ligamentumflavum by placing two hemispherical steel ball into the anterior and postierior side of the cervical spinal cordthrough the bone window of the C4-C5.The maximum depth of compression was 60％ of the spine canal anteroposterior diameter.Results (1) Under the anterior depth of a certain pressure with the increase of posterior pressure depth,the stress on the anterior of the CCMC had no significant change,and the stress on the posterior of the CCMC increased greatly with the increase of the degree of canal occlusion.The stress on the posterior of the CCMC varied insignificantly between neighboring depth of canal occlusion from 10％ to 20％ (P ＞ 0.05),while there was remarkably significant difference between 30％ and 60％ (P ＜0.05).(2) Under the posterior depth of a certain pressure with the increase of anterior pressure depth,the stress on the anterior of the CCMC was increased greatly with the increase of the degree of canal occlusion,and the stress on the anterior of the CCMC varied insignificantly between neighboring depth of canal occlusion from 10％ to 20％ (P ＞ 0.05),while there was remarkably significant difference between 30％ and 60％ (P ＜ 0.05).The stress on the posterior of the CCMC had no significant change.ConclusionThe stress on the anterior and the posterior of the CCMC has a close relationship with the depth of canal occlusion,but presents nonlinear relationship.With the increase of the depth of canal occlusion,the stress is increased,especially running over the 30％ depression of canal occlusion.
The Diagonal Compression Field Method using Circular Fans
Hansen, Thomas
2005-01-01
This paper presents a new design method, which is a modification of the diagonal compression field method, the modification consisting of the introduction of circular fan stress fields. The traditional method does not allow changes of the concrete compression direction throughout a given beam...... fields may be used whenever changes in the concrete compression direction are desired. To illustrate the new design method, a specific example of a prestressed concrete beam is calculated....
On the compressibility effects in mixing layers
Khlifi Hechmi
2016-01-01
Full Text Available Previous studies of compressible flows carried out in the past few years have shown that the pressure-strain is the main indicator of the structural compressibility effects. Undoubtedly, this terms plays a key role toward strongly changing magnitude of the turbulent Reynolds stress anisotropy. On the other hand, the incompressible models of the pressure-strain correlation have not correctly predicted compressible turbulence at high speed shear flow. Consequently, a correction of these models is needed for precise prediction of compressibility effects. In the present work, a compressibility correction of the widely used incompressible Launder Reece and Rodi model making their standard coefficients dependent on the turbulent and convective Mach numbers is proposed. The ability of the model to predict the developed mixing layers in different cases from experiments of Goebel and Dutton is examined. The predicted results with the proposed model are compared with DNS and experimental data and those obtained by the compressible model of Adumitroiae et al. and the original LRR model. The results show that the essential compressibility effects on mixing layers are well captured by the proposed model.
Steady compression characteristics of laminated MRE isolator
Wahab, N. A. A.; Mazlan, S. A.; Ubaidillah; Sharif, A. H. R.; Kamaruddin, S.
2016-11-01
This paper focused on an experimental setup on laminated magnetorheological elastomer (MRE) isolator under steady state compression test. An isotropic type natural rubber (NR) based MRE were fabricated and layered with a steel plate to form a multilayer sandwich structure adopted from the conventional laminated rubber bearing design. A set of static compression test was conducted to explore the potential of semi-active laminated MRE isolator in field-dependent stiffness properties. Stress versus strain relationship was assessed under different magnetic fields application. Based on the examination, the stress altered as the application of magnetic fields. Consequently, the effective stiffness of isolator also influenced by the magnetic fields induction. The experimental results show that the proposed laminated MRE isolator can effectively alter the compression stiffness up to the 14.56%. The preliminary results have confirmed the tunability of the semi-active laminated MRE isolator in which it would be beneficial for improving building isolator in general.
HUANG Zi-qian; HE Yue-hui; CAI Hai-tao; XIAO Yi-feng; HUANG Bai-yun
2008-01-01
The aim of this study is to apply the concept of functionally graded materials (FGMs) to cemented carbides and to develop high-performance rock drill buttons.Cobalt-gradient structure was introduced to the surface zone of the buttons by carburizing process.Finite element method and XRD measurement were used to decide the distribution of thermal residual stress.Constitutive parameters were determined by constraint factor.Numerical results show that residual stresses of gradient buttons mainly concentrate in cobalt-gradient zone.There is compressive stress in the surface zone and tensile stress in the cobalt-rich zone.The maximum value of surface compressive stress is 180 MPa for WC-6Co cemented carbides.And the numerical results agree with the results of XRD measurement.
Luttrell, Karen M.; Tong, Xiaopeng; Sandwell, David T.; Brooks, Benjamin A.; Bevis, Michael G.
2011-11-01
The great 27 February 2010 Mw 8.8 earthquake off the coast of southern Chile ruptured a ˜600 km length of subduction zone. In this paper, we make two independent estimates of shear stress in the crust in the region of the Chile earthquake. First, we use a coseismic slip model constrained by geodetic observations from interferometric synthetic aperture radar (InSAR) and GPS to derive a spatially variable estimate of the change in static shear stress along the ruptured fault. Second, we use a static force balance model to constrain the crustal shear stress required to simultaneously support observed fore-arc topography and the stress orientation indicated by the earthquake focal mechanism. This includes the derivation of a semianalytic solution for the stress field exerted by surface and Moho topography loading the crust. We find that the deviatoric stress exerted by topography is minimized in the limit when the crust is considered an incompressible elastic solid, with a Poisson ratio of 0.5, and is independent of Young's modulus. This places a strict lower bound on the critical stress state maintained by the crust supporting plastically deformed accretionary wedge topography. We estimate the coseismic shear stress change from the Maule event ranged from -6 MPa (stress increase) to 17 MPa (stress drop), with a maximum depth-averaged crustal shear-stress drop of 4 MPa. We separately estimate that the plate-driving forces acting in the region, regardless of their exact mechanism, must contribute at least 27 MPa trench-perpendicular compression and 15 MPa trench-parallel compression. This corresponds to a depth-averaged shear stress of at least 7 MPa. The comparable magnitude of these two independent shear stress estimates is consistent with the interpretation that the section of the megathrust fault ruptured in the Maule earthquake is weak, with the seismic cycle relieving much of the total sustained shear stress in the crust.
Plain bearing stresses due to forming and oil film pressure
Burke-Veliz, A.; Wang, D.; Wahdy, N.; Reed, P. A. S.; Merritt, D.; Syngellakis, S.
2009-08-01
This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.
Plain bearing stresses due to forming and oil film pressure
Burke-Veliz, A; Reed, P A S; Syngellakis, S [University of Southampton, School of Engineering Sciences, Southampton SO17 1BJ (United Kingdom); Wang, D; Wahdy, N; Merritt, D, E-mail: allan.burke@itesm.m [MAHLE Engine Systems UK Ltd, 2 Central park Drive, Rugby CV23 0WE (United Kingdom)
2009-08-01
This paper describes a methodology for assessing critical stress ranges arising in automotive plain bearings during engine operations. An industry-produced and run simulation program provides information on oil film pressure and overall bearing deformation during accelerated performance tests. This code performs an elasto-hydrodynamic lubrication analysis accounting for the compliance of the housing and journal. Finite element analyses of a multilayer bearing are performed to assess the conditions responsible for possible fatigue damage over the bearing lining. The residual stresses arising from the forming and fitting process are first assessed. The stress analyses over the engine cycle show the intensity and distribution of cyclic tensile and compressive stresses in the bearing. The location of maximum stress range is found to be consistent with the damage observed in accelerated fatigue tests. Critical zones are identified in the lining for possible fatigue crack initiation and growth studies.
Effects of LSP on micro-structures and residual stresses in a 4 mm CLAM steel weld joints
Chen, Xizhang, E-mail: chenxizhang@wzu.edu.cn [School of Mechanical and Electrical Engineering, Wenzhou University., Wenzhou 325035 (China); School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu (China); Fang, Yuanyuan [School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu (China); Zhang, Shuyan; Kelleher, Joe F. [ISIS, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom); Zhou, Jianzhong [School of Mechanical Engineering, Jiangsu University, Zhenjiang 212013, Jiangsu (China)
2015-05-15
The effects of laser shock processing (LSP) on the distribution of residual stress and micro-structure of China Low Activation Martensitic (CLAM) steel weldment were investigated via neutron diffraction and optical microscope (OM). A pair of 4 mm CLAM steel plates joined by GTA welding. Special attention is paid to the generation of high level compressive residual stresses introduced by LSP. Residual stress in longitudinal, normal and transversal direction at weldment surface and longitudinal stress through thickness are evaluated via neutron diffraction. Compressive residual stress after LSP occurred at more than 90% areas within the weld joint, it is almost double the areas of compressive stress compare to weldment surface before LSP. The maximum compressive normal residual stress becomes to −183 MPa after LSP from −63 MPa before LSP. The Modification of surface micro-structures including weld zone (WZ), heat affected zone (HAZ) and base metal (BM) are also discussed. Results to date demonstrate that laser shock processing has been a great potential method for the improvement of mechanical performance of components.
Lossless Medical Image Compression
Nagashree G
2014-06-01
Full Text Available Image compression has become an important process in today‟s world of information exchange. Image compression helps in effective utilization of high speed network resources. Medical Image Compression is very important in the present world for efficient archiving and transmission of images. In this paper two different approaches for lossless image compression is proposed. One uses the combination of 2D-DWT & FELICS algorithm for lossy to lossless Image Compression and another uses combination of prediction algorithm and Integer wavelet Transform (IWT. To show the effectiveness of the methodology used, different image quality parameters are measured and shown the comparison of both the approaches. We observed the increased compression ratio and higher PSNR values.
Evolution of residual stresses in micro-arc oxidation ceramic coatings on 6061 Al alloy
Shen, Dejiu; Cai, Jingrui; Guo, Changhong; Liu, Peiyu
2013-11-01
Most researches on micro-arc oxidation mainly focus on the application rather than discovering the evolution of residual stresses. However, residual stresses in the surface coatings of structural components have adverse effects on their properties, such as fatigue life, dimensional stability and corrosion resistance, etc. The micro-arc oxidation ceramic coatings are produced on the surfaces of 6061 aluminum alloy by a homemade asymmetric AC type of micro-arc oxidation equipment of 20 kW. A constant current density of 4.4±0.1 A/dm2 and a self-regulated composite electrolyte are used. The micro-arc oxidation treatment period ranges from 10 min to 40 min, and the thickness of the ceramic coatings is more than 20 μm. Residual stresses attributed to γ-Al2O3 constituent in the coatings at different micro-arc oxidation periods are analyzed by an X-ray diffractometer using the sin2 ψ method. The analysis results show that the residual stress in the ceramic coatings is compressive in nature, and it increases first and then decreases with micro-arc oxidation time increase. The maximum stress value is 1 667±20 MPa for period of 20 min. Through analyzing the coating thickness, surface morphology and phase composition, it is found that the residual stress in the ceramic coatings is linked closely with the coating growth, the phase composition and the micro cracks formed. It is also found that both the heat treatment and the ultrasonic action release remarkably the residual compressive stress. The heat treatment makes the residual compressive stress value decrease 1 378 MPa. The ultrasonic action even alters the nature of the residual stress, making the residual compressive stress change into a residual tensile stress.
Celiac Artery Compression Syndrome
Mohammed Muqeetadnan
2013-01-01
Full Text Available Celiac artery compression syndrome is a rare disorder characterized by episodic abdominal pain and weight loss. It is the result of external compression of celiac artery by the median arcuate ligament. We present a case of celiac artery compression syndrome in a 57-year-old male with severe postprandial abdominal pain and 30-pound weight loss. The patient eventually responded well to surgical division of the median arcuate ligament by laparoscopy.
Electromechanical Apparatus Measures Residual Stress
Chern, Engmin J.; Flom, Yury
1993-01-01
Nondestructive test exploits relationship between stress and eddy-current-probe resistance. Yields data on residual stress or strain in metal tension/compression specimen (stress or strain remaining in specimen when no stress applied from without). Apparatus is assembly of commercial equipment: tension-or-compression testing machine, eddy-current probe, impedance gain-and-phase analyzer measuring impedance of probe coil, and desktop computer, which controls other equipment and processes data received from impedance gain-and-phase analyzer.
Compressed sensing & sparse filtering
Carmi, Avishy Y; Godsill, Simon J
2013-01-01
This book is aimed at presenting concepts, methods and algorithms ableto cope with undersampled and limited data. One such trend that recently gained popularity and to some extent revolutionised signal processing is compressed sensing. Compressed sensing builds upon the observation that many signals in nature are nearly sparse (or compressible, as they are normally referred to) in some domain, and consequently they can be reconstructed to within high accuracy from far fewer observations than traditionally held to be necessary.Â Apart from compressed sensing this book contains other related app
Pearlman, William A
2013-01-01
This book explains the stages necessary to create a wavelet compression system for images and describes state-of-the-art systems used in image compression standards and current research. It starts with a high level discussion of the properties of the wavelet transform, especially the decomposition into multi-resolution subbands. It continues with an exposition of the null-zone, uniform quantization used in most subband coding systems and the optimal allocation of bitrate to the different subbands. Then the image compression systems of the FBI Fingerprint Compression Standard and the JPEG2000 S
Stiffness of compression devices
Giovanni Mosti
2013-03-01
Full Text Available This issue of Veins and Lymphatics collects papers coming from the International Compression Club (ICC Meeting on Stiffness of Compression Devices, which took place in Vienna on May 2012. Several studies have demonstrated that the stiffness of compression products plays a major role for their hemodynamic efficacy. According to the European Committee for Standardization (CEN, stiffness is defined as the pressure increase produced by medical compression hosiery (MCH per 1 cm of increase in leg circumference.1 In other words stiffness could be defined as the ability of the bandage/stockings to oppose the muscle expansion during contraction.
DOU Xiu-Ming; SUN Bao-Quan; WANG Bao-Rui; MA Shan-Shan; ZHOU Rong; HUANG She-Song; NI Hai-Qiao; NIU Zhi-Chuan
2008-01-01
@@ We report a photoluminescence (PL) energy red-shift of single quantum dots(QDs)by applying an in-plane compressive uniaxial stress along the[110]direction at a liquid nitrogen temperature.Uniaxial stress has an effect not only on the confinement potential in the growth direction which results in the PL shift,but also on the cylindrical symmetry of QDs which can be reflected by the change of the full width at half maximum of PL peak.This implies that uniaxial stress has an important role in tuning PL energy and fine structure splitting of QDs.
M. Sticchi
2015-07-01
Full Text Available Laser Shock Peening is a fatigue enhancement treatment using laser energy to induce compressive Residual Stresses (RS in the outer layers of metallic components. This work describes the variations of introduced RS-field with peen size and coverage for thin metal samples treated with under-water-LSP. The specimens under investigation were of aluminium alloy AA2024-T351, AA2139-T3, AA7050-T76 and AA7075-T6, with thickness 1.9 mm. The RS were measured by using Hole Drilling with Electronic Speckle Pattern Interferometry and X-ray Diffraction. Of particular interest are the effects of the above mentioned parameters on the zero-depth value, which gives indication of the amount of RS through the thickness, and on the value of the surface compressive stresses, which indicates the magnitude of induced stresses. A 2D-axisymmetrical Finite Element model was created for a preliminary estimation of the stress field trend. From experimental results, correlated with numerical and analytical analysis, the following conclusions can be drawn: increasing the spot size the zero-depth value increases with no significant change of the maximum compressive stress; the increase of coverage leads to significant increase of the compressive stress; thin samples of Al-alloy with low Hugoniot Elastic Limit (HEL reveal deeper compression field than alloy with higher HEL value.
Tension-Compression Fatigue of a Nextel™720/alumina Composite at 1200 °C in Air and in Steam
Lanser, R. L.; Ruggles-Wrenn, M. B.
2016-08-01
Tension-compression fatigue behavior of an oxide-oxide ceramic-matrix composite was investigated at 1200 °C in air and in steam. The composite is comprised of an alumina matrix reinforced with Nextel™720 alumina-mullite fibers woven in an eight harness satin weave (8HSW). The composite has no interface between the fiber and matrix, and relies on the porous matrix for flaw tolerance. Tension-compression fatigue behavior was studied for cyclical stresses ranging from 60 to 120 MPa at a frequency of 1.0 Hz. The R ratio (minimum stress to maximum stress) was -1.0. Fatigue run-out was defined as 105 cycles and was achieved at 80 MPa in air and at 70 MPa in steam. Steam reduced cyclic lives by an order of magnitude. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Specimens subjected to prior cyclic loading in air retained 100 % of their tensile strength. The steam environment severely degraded tensile properties. Tension-compression cyclic loading was considerably more damaging than tension-tension cyclic loading. Composite microstructure, as well as damage and failure mechanisms were investigated.
严少华; 钱七虎; 孙伟; 尹放林
2001-01-01
在实际工程中推广应用钢纤维高强混凝土,要了解其基本力学性能.采用MTS815.03型液压伺服刚性压力试验机,对钢纤维含量为0～6%、抗压强度在65～120MPa范围的4种钢纤维高强混凝土,进行单轴压缩荷载作用下的应力应变全过程试验.结合试验给出全曲线的方程,并分析钢纤维对抗压强度、弹性模量、韧度、泊松比等的影响.试验表明,当钢纤维长度大于或接近于最大集料尺寸时,钢纤维高强混凝土具有较高的抗压强度和韧度,是一种优良的新型建筑材料.%It is necessary to research the basic mechanical performance inorder to use high-strength steel fiber reinforced concrete (HSFC) in practical engineering. Tests are conducted to characterize the stress-strain relationship of HSFC in compression by MTS815.03 rock testing machine. The concrete strength investigated ranges from 65 to 120 MPa and the volume fraction of steel fiber ranges from 0 to 6%. Based on the test data, an analytical model is proposed to generate the complete stress-strain curve for HSFC. The elastic modulus and toughness and Poisson’s ration of HSFC are also calculated in this paper. It is also proved by tests that HSFC is a good building material with high strength and high toughness when steel fibers are longer than the size of aggregate in concrete.
An Enhanced Static Data Compression Scheme Of Bengali Short Message
Arif, Abu Shamim Mohammod; Islam, Rashedul
2009-01-01
This paper concerns a modified approach of compressing Short Bengali Text Message for small devices. The prime objective of this research technique is to establish a low complexity compression scheme suitable for small devices having small memory and relatively lower processing speed. The basic aim is not to compress text of any size up to its maximum level without having any constraint on space and time, rather than the main target is to compress short messages up to an optimal level which needs minimum space, consume less time and the processor requirement is lower. We have implemented Character Masking, Dictionary Matching, Associative rule of data mining and Hyphenation algorithm for syllable based compression in hierarchical steps to achieve low complexity lossless compression of text message for any mobile devices. The scheme to choose the diagrams are performed on the basis of extensive statistical model and the static Huffman coding is done through the same context.
Performance Analysis of Multi Spectral Band Image Compression using Discrete Wavelet Transform
S. S. Ramakrishnan
2012-01-01
Full Text Available Problem statement: Efficient and effective utilization of transmission bandwidth and storage capacity have been a core area of research for remote sensing images. Hence image compression is required for multi-band satellite imagery. In addition, image quality is also an important factor after compression and reconstruction. Approach: In this investigation, the discrete wavelet transform is used to compress the Landsat5 agriculture and forestry image using various wavelets and the spectral signature graph is drawn. Results: The compressed image performance is analyzed using Compression Ratio (CR, Peak Signal to Noise Ratio (PSNR. The compressed image using dmey wavelet is selected based on its Digital Number Minimum (DNmin and Digital Number Maximum (DNmax. Then it is classified using maximum likelihood classification and the accuracy is determined using error matrix, kappa statistics and over all accuracy. Conclusion: Hence the proposed compression technique is well suited to compress the agriculture and forestry multi-band image.
Roman, D.C.; Moran, S.C.; Power, J.A.; Cashman, K.V.
2004-01-01
We searched for changes in local stress-field orientation at Mount Spurr volcano, Alaska, between August 1991 and December 2001. This study focuses on the stress-field orientation beneath Crater Peak vent, the site of three eruptions in 1992, and beneath the summit of Mount Spurr. Local stress tensors were calculated by inverting subsets of 140 fault-plane solutions for earthquakes beneath Crater Peak and 96 fault-plane solutions for earthquakes beneath Mount Spurr. We also calculated an upper-crustal regional stress tensor by inverting fault-plane solutions for 66 intraplate earthquakes located near Mount Spurr during 1991-2001. Prior to the 1992 eruptions, and for 11 months beginning with a posteruption seismic swarm, the axis of maximum compressive stress beneath Crater Peak was subhorizontal and oriented N67-76??E, approximately perpendicular to the regional axis of maximum compressive stress (N43??W). The strong temporal correlation between this horizontal stress-field rotation (change in position of the ??1/ ??3 axes relative to regional stress) and magmatic activity indicates that the rotation was related to magmatic activity, and we suggest that the Crater Peak stress-field rotation resulted from pressurization of a network of dikes. During the entire study period, the stress field beneath the summit of Mount Spurr also differed from the regional stress tensor and was characterized by a vertical axis of maximum compressive stress. We suggest that slip beneath Mount Spurr's summit occurs primarily on a major normal fault in response to a combination of gravitational loading, hydrothermal circulation, and magmatic processes beneath Crater Peak. Online material: Regional and local fault-plane solutions.
Akkerman, J. W.
1982-01-01
New mechanism alters compression ratio of internal-combustion engine according to load so that engine operates at top fuel efficiency. Ordinary gasoline, diesel and gas engines with their fixed compression ratios are inefficient at partial load and at low-speed full load. Mechanism ensures engines operate as efficiently under these conditions as they do at highload and high speed.
Neotectonic stresses in Fennoscandia: field observations and modelling
Pascal, Christophe
2013-04-01
present-day stress magnitudes are far to be uniform in Scandinavia. For example the modelling predicts that the topography of the southern Norwegian Mountains creates Gravitational Potential Energy (GPE) levels higher than the ones characterising the surrounding regions. This results in significant buoyancy forces competing locally with the regional ridge-push. GPE decreases almost gradually towards the Gulf of Bothnia where strong compressive stresses are predicted. A local departure from the regional NW-SE trend for the maximum horizontal stress axes is simulated in Trøndelag, Norway. This local stress deviation is supported by stress-relief observations and in situ stress measurements. Our modelling suggests that it results from the combined effects of the weak rheology of the Møre-Trøndelag Fault Complex and topographic stresses associated with the southern Norwegian Scandes mountains.
Equation-of-state model for shock compression of hot dense matter
Pain, J C
2007-01-01
A quantum equation-of-state model is presented and applied to the calculation of high-pressure shock Hugoniot curves beyond the asymptotic fourfold density, close to the maximum compression where quantum effects play a role. An analytical estimate for the maximum attainable compression is proposed. It gives a good agreement with the equation-of-state model.
Spectral Animation Compression
Chao Wang; Yang Liu; Xiaohu Guo; Zichun Zhong; Binh Le; Zhigang Deng
2015-01-01
This paper presents a spectral approach to compress dynamic animation consisting of a sequence of homeomor-phic manifold meshes. Our new approach directly compresses the field of deformation gradient defined on the surface mesh, by decomposing it into rigid-body motion (rotation) and non-rigid-body deformation (stretching) through polar decompo-sition. It is known that the rotation group has the algebraic topology of 3D ring, which is different from other operations like stretching. Thus we compress these two groups separately, by using Manifold Harmonics Transform to drop out their high-frequency details. Our experimental result shows that the proposed method achieves a good balance between the reconstruction quality and the compression ratio. We compare our results quantitatively with other existing approaches on animation compression, using standard measurement criteria.
Uniaxial Compressive Properties of Ultra High Toughness Cementitious Composite
CAI Xiangrong; XU Shilang
2011-01-01
Uniaxial compression tests were conducted to characterize the main compressive performance of ultra high toughness cementitious composite(UHTCC)in terms of strength and toughness and to obtain its stress-strain relationships.The compressive strength investigated ranges from 30 MPa to 60 MPa.Complete stress-strain curves were directly obtained,and the strength indexes,including uniaxial compressive strength,compressive strain at peak stress,elastic modulus and Poisson's ratio,were calculated.The comparisons between UHTCC and matrix were also carried out to understand the fiber effect on the compressive strength indexes.Three dimensionless toughness indexes were calculated,which either represent its relative improvement in energy absorption capacity because of fiber addition or provide an indication of its behavior relative to a rigid-plastic material.Moreover,two new toughness indexes,which were named as post-crack deformation energy and equivalent compressive strength,were proposed and calculated with the aim at linking up the compressive toughness of UHTCC with the existing design concept of concrete.The failure mode was also given.The study production provides material characteristics for the practical engineering application of UHTCC.
Compressive Tectonics around Tibetan Plateau Edges
Zhao Zhixin; Xu Jiren
2009-01-01
Various earthquake fault types, mechanism solutions, stress field, and other geophysical data were analyzed for study on the crust movement in the Tibetan plateau and its tectonic implications. The results show that numbers of thrust fault and strike-slip fault type earthquakes with strong compressive stress near NNE-SSW direction occurred in the edges around the plateau except the eastern boundary. Some normal faulting type earthquakes concentrate in the Central Tibetan plateau. The strikes of fault planes of thrust and strike-slip faulting earthquakes are almost in the E-W direction based on the analyses of the Wulff stereonet diagrams of fault plane solutions. This implies that the dislocation slip vectors of the thrust and strike-slip faulting type events have quite great components in the N-S direction. The compression motion mainly probably plays the tectonic active regime around the plateau edges. The compressive stress in N-S or NE-SW directions predominates earthquake occurrence in the thrust and strike-slip faulting event region around the plateau. The compressive motion around the Tibetan plateau edge is attributable to the northward motion of the Indian subcontinent plate. The northward motion of the Tibetan plateau shortened in the N-S direction encounters probably strong obstructions at the western and northern margins.
Hemanth, M; Deoli, Shilpi; Raghuveer, H P; Rani, M S; Hegde, Chatura; Vedavathi, B
2015-08-01
Orthodontic tooth movement is a complex procedure that occurs due to various biomechanical changes in the periodontium. Optimal orthodontic forces yield maximum tooth movement whereas if the forces fall beyond the optimal threshold it can cause deleterious effects. Among various types of tooth movements intrusion and lingual root torque are associated with causing root resoprtion, especially with the incisors. Therefore in this study, the stress patterns in the periodontal ligament (PDL) were evaluated with intrusion and lingual root torque using finite element method (FEM). A three-dimensional (3D) FEM model of the maxillary incisors was generated using SOLIDWORKS modeling software. Stresses in the PDL were evaluated with intrusive and lingual root torque movements by a 3D FEM using ANSYS software using linear stress analysis. It was observed that with the application of intrusive load compressive stresses were distributed at the apex whereas tensile stress was seen at the cervical margin. With the application of lingual root torque maximum compressive stress was distributed at the apex and tensile stress was distributed throughout the PDL. For intrusive and lingual root torque movements stress values over the PDL was within the range of optimal stress value as proposed by Lee, with a given force system by Proffit as optimum forces for orthodontic tooth movement using linear properties.
Study on in-situ stress measurement around coastal marginal land in Fujian
LI Hong; AN Qi-mei; XIE Fu-ren
2005-01-01
The in-situ hydraulic fracturing stress measurements have been carried out around the coastal marginal land in Fujian Province. And the characteristics of magnitude, direction and distribution of tectonic stress have been obtained.Based on the observed stress data, the characteristics and activities of fault zones are analyzed and studied in the paper according to the Coulomb friction criteria. ① The maximum horizontal principal compressive stress is in the NW-WNW direction from the north to the south along the coastline verge, which is parallel to the strike of the NW-trending fault zone, consistent with the direction of principal compressive stress obtained from geological structure and across-fault deformation data, and different from that reflected by focal mechanism solution by about 20°. ② The horizontal principal stress increases with depth, the relation among three stresses is SH＞Sv＞Sh or SH≈Sv＞Sh, and the stress state is liable to normal fault and strike-slip fault activities. ③ According to Coulomb friction criteria and taking the friction strength μ as 0.6～1.0 for analysis, the stress state reaching or exceeding the threshold for normal-fault frictional sliding near the fault implies that the current tectonic activity in the measuring area is mainly normal faulting. ④ The force source of current tectonic stress field comes mainly from the westward and northwestward horizontal extrusions from the Pacific and Philippine Plates respectively to the Eurasian Plate.
Transversely Compressed- and Restrained Shear Joints
Schmidt, Jacob Wittrup; Hansen, Christian Skodborg
2013-01-01
. This paper presents theoretical model which can predict the response of transversely compressed and restrained single- and double lap shear joints. The interface material model is based on a cohesive law in the shear-slip plane with a descending branch and a uniform frictional stress added due...... to the friction in the crack, emanating from the transverse pressure or restraint. The theoretical model is compared with experimental results from transversely compressed single- and double shear joints. Also theoretical predictions of a mechanical integrated sleeve-wedge anchorage load capacity are carried out...
Controls on radon emission from granite as evidenced by compression testing to failure
Koike, Katsuaki; Yoshinaga, Tohru; Suetsugu, Kenta; Kashiwaya, Koki; Asaue, Hisafumi
2015-10-01
A set of uniaxial compression tests of granite specimens taken from five localities across Japan was conducted to identify the factors controlling the quantity of radon (Rn) emission (sum of 222Rn and 220Rn) during compression and failure. An α-scintillation detector and a gas flow unit were installed with a testing machine to enable continuous measurement of Rn emissions. Common to all specimens, Rn emissions remained at or slightly declined from the background level after the start of loading; this is similar to the natural phenomenon of decline in groundwater-dissolved Rn before an earthquake. Closure of original microcracks is the most likely cause of the initial Rn decline. Then, Rn emissions begin to increase at 46-57 per cent stress level to the uniaxial compressive strength, and continue to increase even after the failure of specimen. This commencement stress level is close to the general stress level at outbreak of acoustic emissions caused by the development and connection of microcracks. The Rn increase after failure is similar to a phenomenon observed in aftershocks, which may originate from the enhancement of Rn emanations from grains due to the large increase in total surface area and stress release. In addition to the initial radioelement content in rock, the failure pattern (conjugate shear versus longitudinal tensile type), compressive strength, and grain size are possible control factors of the maximum quantity of Rn emissions induced by failure. This maximum may also be affected by the development velocity of the emanation area, which is related to the Rn emanation fraction, associated with the fragmentation. In addition to the magnitude of an earthquake and its hypocentre distance to Rn detectors, the magnitude of increase in Rn concentration in soil gas and groundwater before, during, and after an earthquake in crystalline rocks depends on the intrinsic radioelement content, the mineral texture, and the mechanical properties of rocks. Rock
Janssen, G.C.A.M.; Kamminga, J.D.
2004-01-01
In the absence of thermal stress, tensile stress in hard metal films is caused by grain boundary shrinkage and compressive stress is caused by ion peening. It is shown that the two contributions are additive. Moreover tensile stress generated at the grain boundaries does not relax by ion bombardment
Overall bolt stress optimization
Pedersen, Niels Leergaard
2013-01-01
The state of stress in bolts and nuts with International Organization for Standardization metric thread design is examined and optimized. The assumed failure mode is fatigue, so the applied preload and the load amplitude together with the stress concentrations define the connection strength....... Maximum stress in the bolt is found at the fillet under the head, at the thread start, or at the thread root. To minimize the stress concentration, shape optimization is applied. Nut shape optimization also has a positive effect on the maximum stress. The optimization results show that designing a nut......, which results in a more evenly distribution of load along the engaged thread, has a limited influence on the maximum stress due to the stress concentration at the first thread root. To further reduce the maximum stress, the transition from bolt shank to the thread must be optimized. Stress reduction...
The Diagonal Compression Field Method using Circular Fans
Hansen, Thomas
2006-01-01
In a concrete beam with transverse stirrups the shear forces are carried by inclined compression in the concrete. Along the tensile zone and the compression zone of the beam the transverse components of the inclined compressions are transferred to the stirrups, which are thus subjected to tension....... Since the eighties the diagonal compression field method has been used to design transverse shear reinforcement in concrete beams. The method is based on the lower-bound theorem of the theory of plasticity, and it has been adopted in Eurocode 2. The paper presents a new design method, which...... with low shear stresses. The larger inclination (the smaller -value) of the uniaxial concrete stress the more transverse shear reinforcement is needed; hence it would be optimal if the -value for a given beam could be set to a low value in regions with high shear stresses and thereafter increased...
Vascular compression syndromes.
Czihal, Michael; Banafsche, Ramin; Hoffmann, Ulrich; Koeppel, Thomas
2015-11-01
Dealing with vascular compression syndromes is one of the most challenging tasks in Vascular Medicine practice. This heterogeneous group of disorders is characterised by external compression of primarily healthy arteries and/or veins as well as accompanying nerval structures, carrying the risk of subsequent structural vessel wall and nerve damage. Vascular compression syndromes may severely impair health-related quality of life in affected individuals who are typically young and otherwise healthy. The diagnostic approach has not been standardised for any of the vascular compression syndromes. Moreover, some degree of positional external compression of blood vessels such as the subclavian and popliteal vessels or the celiac trunk can be found in a significant proportion of healthy individuals. This implies important difficulties in differentiating physiological from pathological findings of clinical examination and diagnostic imaging with provocative manoeuvres. The level of evidence on which treatment decisions regarding surgical decompression with or without revascularisation can be relied on is generally poor, mostly coming from retrospective single centre studies. Proper patient selection is critical in order to avoid overtreatment in patients without a clear association between vascular compression and clinical symptoms. With a focus on the thoracic outlet-syndrome, the median arcuate ligament syndrome and the popliteal entrapment syndrome, the present article gives a selective literature review on compression syndromes from an interdisciplinary vascular point of view.
Scoville, John
2011-01-01
A new approach to data compression is developed and applied to multimedia content. This method separates messages into components suitable for both lossless coding and 'lossy' or statistical coding techniques, compressing complex objects by separately encoding signals and noise. This is demonstrated by compressing the most significant bits of data exactly, since they are typically redundant and compressible, and either fitting a maximally likely noise function to the residual bits or compressing them using lossy methods. Upon decompression, the significant bits are decoded and added to a noise function, whether sampled from a noise model or decompressed from a lossy code. This results in compressed data similar to the original. For many test images, a two-part image code using JPEG2000 for lossy coding and PAQ8l for lossless coding produces less mean-squared error than an equal length of JPEG2000. Computer-generated images typically compress better using this method than through direct lossy coding, as do man...
Bayat, Hossein; Sedaghat, Azadeh; Safari Sinegani, Ali Akbar; Gregory, Andrew S.
2015-03-01
This study was conducted to estimate the soil unsaturated hydraulic conductivity through the van Genuchten model using easy to measure soil properties by regression and artificial neural networks methods. In this study, 148 soil samples were taken from five provinces of Iran. Basic soil properties (clay, silt/sand and bulk density) and other soil properties were measured. Soil water retention curve was measured to obtain the unsaturated hydraulic conductivity curve using the van Genuchten-Mualem model. Confined compression curve was measured and the modified model of van Genuchten was fitted on its data. Two-thirds and one-third of the data were used for the training and testing steps, respectively. Confined compression curve parameters and other soil properties were used as predictors to estimate unsaturated hydraulic conductivity curve. Pedotransfer functions (PTFs) were developed in two separate parts: in 5 and 6 PTFs basic soil properties were or were not used as predictors, respectively. The artificial neural networks (ANNs) performed better than the regression methods. Among the ANN-developed PTFs which have not used basic soil properties as predictors, PTFa3, with the inputs of the parameters of confined compression curve (n∗, α∗ and e0), performed better than the others. Also, among the ANN-developed PTFs that used basic soil properties as predictors along with the other input variables, PTFb5 that used the σmc (stress at the maximum curvature) and σi (stress at the inflection point) as inputs along with basic soil properties, performed better than the other PTFs. The results showed a successful prediction of the hydraulic conductivity curve using confined compression curve.
H. Xiao
2003-01-01
Full Text Available The self-consistent Eulerian rate-type elastoplastic model based on the logarithmic rate is used to study finite bending of a compressible elastic-perfectly plastic rectangular block. It is found that an explicit closed-form solution for this typical inhomogeneous finite deformation , mode may be available in a general case of compressible deformation with a stretch normal to the bending plane, where the maximum circumferential stretch at the outer surface serves as an Independent parameter. Expressions are given for the bending angle, the bending moment, the the outer and the inner radii, and the radii of the two moving elastic-plastic interfaces, etc. The exact stress distribution on any circumferential cross-section of the deformed block is accordingly determined.
砌体局部受压有限元分析%Finite-element analysis of masonry under local compressive load
杨卫忠; 王博
2011-01-01
采用有限元方法,分析了典型砌体局部受压时主应力和Mises应力分别沿截面宽度和深度的变化规律.结果表明,最大主拉应力位置与已有试验结果大致吻合；应力云图可清晰地反映砌体局压时的应力扩散作用,主要应力扩散范围约为一倍的局压范围的边长；最大Mises应力值可反映不同局压位置对局压强度的影响,研究成果有助于进一步了解砌体局压的受力机理,为下一步修订规范提供参考.%Finite-element analysis can reveal the complex mechanism of structural element. The principal stress and Mises stress of masonry under local compressive load are analyzed by FEA, and the main variability is the position of local compression. The result shows that the position of the maximum principle tensile stress has a good agree with the experimental result. The stress dispersion can be validated by comparing the stress cloud atlas of various sections,and the dispersion range is about specimen length around the local bearing area. The maximum Mises stress has a strong affect on the increased strength of masonry. It is very helpful for the further study the mechanism of masonry under local compression,and it can also provide a reference for revising the masonry code.
Artificial Neural Network Model for Predicting Compressive
Salim T. Yousif
2013-05-01
Full Text Available Compressive strength of concrete is a commonly used criterion in evaluating concrete. Although testing of the compressive strength of concrete specimens is done routinely, it is performed on the 28th day after concrete placement. Therefore, strength estimation of concrete at early time is highly desirable. This study presents the effort in applying neural network-based system identification techniques to predict the compressive strength of concrete based on concrete mix proportions, maximum aggregate size (MAS, and slump of fresh concrete. Back-propagation neural networks model is successively developed, trained, and tested using actual data sets of concrete mix proportions gathered from literature. The test of the model by un-used data within the range of input parameters shows that the maximum absolute error for model is about 20% and 88% of the output results has absolute errors less than 10%. The parametric study shows that water/cement ratio (w/c is the most significant factor affecting the output of the model. The results showed that neural networks has strong potential as a feasible tool for predicting compressive strength of concrete.
Shot Peening and Thermal Stress Relaxation in 17-4 PH Stainless Steel
Qin, Enwei; Chen, Guoxing; Tan, Ziming; Wu, Shuhui
2015-11-01
Shot peening is an effective process to enhance the fatigue performance of turbine blades. In this study, the effect of peening pressures was discussed in terms of the residual stress distribution and the surface morphology. Shot peening processes were designed at varying pressures on a 17-4 PH martensitic stainless steel. The profiles of hardness and residual stress were characterized in the cross section. The thermal stress relaxation was further carried out to evaluate the stability of the compressive residual stress under service temperatures of turbine blades. Results show that a maximum stress depth is obtained with peening pressure of 0.40 MPa, and the residual stress can be maintained up to 400 °C, which ensures the service in low-pressure turbine blades.
Hu, Shengsun; Guo, Chaobo; Wang, Dongpo; Wang, Zhijiang
2016-09-01
The nonuniform distributions of the residual stress were simulated by a 3D finite element model to analyze the elastic-plastic dynamic ultrasonic impact treatment (UIT) process of multiple impacts on the 2024 aluminum alloy. The evolution of the stress during the impact process was discussed. The successive impacts during the UIT process improve the uniformity of the plastic deformation and decrease the maximum compressive residual stress beneath the former impact indentations. The influences of different controlled parameters, including the initial impact velocity, pin diameter, pin tip, device moving, and offset distances, on the residual stress distributions were analyzed. The influences of the controlled parameters on the residual stress distributions are apparent in the offset direction due to the different surface coverage in different directions. The influences can be used to understand the UIT process and to obtain the desired residual stress by optimizing the controlled parameters.
End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin
Wei Ju
2012-09-01
Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.
Pozzo, L; Cavallarin, L; Antoniazzi, S; Guerre, P; Biasibetti, E; Capucchio, M T; Schiavone, A
2013-05-01
The European Commission Recommendation 2006/576/EC indicates that the maximum tolerable level of ochratoxin A (OTA) in poultry feeds is 0.1 mg OTA/kg. Thirty-six 1-day-old male broiler chicks were divided into two groups, a control (basal diet) and an OTA (basal diet + 0.1 mg OTA/kg) group. The OTA concentration was quantified in serum, liver, kidney, breast and thigh samples. The thiobarbituric acid reactive substances (TBARS) content were evaluated in the liver, kidney, breast and thigh samples. The glutathione (GSH) content, and catalase (CAT) and superoxide dismutase (SOD) activity were measured in the liver and kidney samples. Histopathological traits were evaluated for the spleen, bursa of Fabricius and liver samples. Moreover, the chemical composition of the meat was analysed in breast and thigh samples. In the OTA diet-fed animals, a serum OTA concentration of 1.15 ± 0.35 ng/ml was found, and OTA was also detected in kidney and liver at 3.58 ± 0.85 ng OTA/g f.w. and 1.92 ± 0.21 ng OTA/g f.w., respectively. The TBARS content was higher in the kidney of the ochratoxin A group (1.53 ± 0.18 nmol/mg protein vs. 0.91 ± 0.25 nmol/mg protein). Feeding OTA at 0.1 mg OTA/kg also resulted in degenerative lesions in the spleen, bursa of Fabricius and liver. The maximum tolerable level of 0.1 mg OTA/kg, established for poultry feeds by the EU, represents a safe limit for the final consumer, because no OTA residues were found in breast and thigh meat. Even though no clinical signs were noticed in the birds fed the OTA-contaminated diet, moderate histological lesions were observed in the liver, spleen and bursa of Fabricius.
Sandia computerized shock compression bibliographical database
Wilbeck, J.S.; Anderson, C.E.; Hokanson, J.C.; Asay, J.R.; Grady, D.E.; Graham, R.A.; Kipp, M.E.
1985-01-01
A searchable and updateable bibliographical database is being developed which will be designed, controlled, and evaluated by working technical experts in the field of shock-compression science. It will emphasize shock-compression properties in the stress region of a few tens of GPa and provide a broad and complete base of bibliographical information on the shock-compression behavior of materials. Through the operation of technical advisors, the database provides authoritative blbliographical and keyword data for use by both the inexperienced and expert user. In its current form, it consists of: (1) a library of journal articles, reports, books, and symposia papers in the areas of shock physics and shock mechanics; and (2) a computerized database system containing complete bibliographical information, exhaustive keyword descriptions, and author abstracts for each of the documents in the database library.
Virtually Lossless Compression of Astrophysical Images
Alparone Luciano
2005-01-01
Full Text Available We describe an image compression strategy potentially capable of preserving the scientific quality of astrophysical data, simultaneously allowing a consistent bandwidth reduction to be achieved. Unlike strictly lossless techniques, by which moderate compression ratios are attainable, and conventional lossy techniques, in which the mean square error of the decoded data is globally controlled by users, near-lossless methods are capable of locally constraining the maximum absolute error, based on user's requirements. An advanced lossless/near-lossless differential pulse code modulation (DPCM scheme, recently introduced by the authors and relying on a causal spatial prediction, is adjusted to the specific characteristics of astrophysical image data (high radiometric resolution, generally low noise, etc.. The background noise is preliminarily estimated to drive the quantization stage for high quality, which is the primary concern in most of astrophysical applications. Extensive experimental results of lossless, near-lossless, and lossy compression of astrophysical images acquired by the Hubble space telescope show the advantages of the proposed method compared to standard techniques like JPEG-LS and JPEG2000. Eventually, the rationale of virtually lossless compression, that is, a noise-adjusted lossles/near-lossless compression, is highlighted and found to be in accordance with concepts well established for the astronomers' community.
Wave energy devices with compressible volumes.
Kurniawan, Adi; Greaves, Deborah; Chaplin, John
2014-12-08
We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power take-off (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000 m(3) and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s.
Compressed Adjacency Matrices: Untangling Gene Regulatory Networks.
Dinkla, K; Westenberg, M A; van Wijk, J J
2012-12-01
We present a novel technique-Compressed Adjacency Matrices-for visualizing gene regulatory networks. These directed networks have strong structural characteristics: out-degrees with a scale-free distribution, in-degrees bound by a low maximum, and few and small cycles. Standard visualization techniques, such as node-link diagrams and adjacency matrices, are impeded by these network characteristics. The scale-free distribution of out-degrees causes a high number of intersecting edges in node-link diagrams. Adjacency matrices become space-inefficient due to the low in-degrees and the resulting sparse network. Compressed adjacency matrices, however, exploit these structural characteristics. By cutting open and rearranging an adjacency matrix, we achieve a compact and neatly-arranged visualization. Compressed adjacency matrices allow for easy detection of subnetworks with a specific structure, so-called motifs, which provide important knowledge about gene regulatory networks to domain experts. We summarize motifs commonly referred to in the literature, and relate them to network analysis tasks common to the visualization domain. We show that a user can easily find the important motifs in compressed adjacency matrices, and that this is hard in standard adjacency matrix and node-link diagrams. We also demonstrate that interaction techniques for standard adjacency matrices can be used for our compressed variant. These techniques include rearrangement clustering, highlighting, and filtering.
Nonrepetitive Colouring via Entropy Compression
Dujmović, Vida; Wood, David R
2011-01-01
A vertex colouring of a graph is \\emph{nonrepetitive} if there is no path whose first half receives the same sequence of colours as the second half. A graph is nonrepetitively $k$-choosable if given lists of at least $k$ colours at each vertex, there is a nonrepetitive colouring such that each vertex is coloured from its own list. It is known that every graph with maximum degree $\\Delta$ is $c\\Delta^2$-choosable, for some constant $c$. We prove this result with $c=4$. We then prove that every subdivision of a graph with sufficiently many division vertices per edge is nonrepetitively 6-choosable. The proofs of both these results are based on the Moser-Tardos entropy-compression method, and a recent extension by Grytczuk, Kozik and Micek for the nonrepetitive choosability of paths. Finally, we prove that every graph with pathwidth $k$ is nonrepetitively ($2k^2+6k+1$)-colourable.
LDPC Codes for Compressed Sensing
Dimakis, Alexandros G; Vontobel, Pascal O
2010-01-01
We present a mathematical connection between channel coding and compressed sensing. In particular, we link, on the one hand, \\emph{channel coding linear programming decoding (CC-LPD)}, which is a well-known relaxation of maximum-likelihood channel decoding for binary linear codes, and, on the other hand, \\emph{compressed sensing linear programming decoding (CS-LPD)}, also known as basis pursuit, which is a widely used linear programming relaxation for the problem of finding the sparsest solution of an under-determined system of linear equations. More specifically, we establish a tight connection between CS-LPD based on a zero-one measurement matrix over the reals and CC-LPD of the binary linear channel code that is obtained by viewing this measurement matrix as a binary parity-check matrix. This connection allows the translation of performance guarantees from one setup to the other. The main message of this paper is that parity-check matrices of "good" channel codes can be used as provably "good" measurement ...
Ratsaby, Joel
2010-01-01
It is well known that text compression can be achieved by predicting the next symbol in the stream of text data based on the history seen up to the current symbol. The better the prediction the more skewed the conditional probability distribution of the next symbol and the shorter the codeword that needs to be assigned to represent this next symbol. What about the opposite direction ? suppose we have a black box that can compress text stream. Can it be used to predict the next symbol in the stream ? We introduce a criterion based on the length of the compressed data and use it to predict the next symbol. We examine empirically the prediction error rate and its dependency on some compression parameters.
Dheemanth H N
2016-07-01
Full Text Available Lempel–Ziv–Welch (LZW is a universal lossless data compression algorithm created by Abraham Lempel, Jacob Ziv, and Terry Welch. LZW compression is one of the Adaptive Dictionary techniques. The dictionary is created while the data are being encoded. So encoding can be done on the fly. The dictionary need not be transmitted. Dictionary can be built up at receiving end on the fly. If the dictionary overflows then we have to reinitialize the dictionary and add a bit to each one of the code words. Choosing a large dictionary size avoids overflow, but spoils compressions. A codebook or dictionary containing the source symbols is constructed. For 8-bit monochrome images, the first 256 words of the dictionary are assigned to the gray levels 0-255. Remaining part of the dictionary is filled with sequences of the gray levels.LZW compression works best when applied on monochrome images and text files that contain repetitive text/patterns.
Shocklets in compressible flows
袁湘江; 男俊武; 沈清; 李筠
2013-01-01
The mechanism of shocklets is studied theoretically and numerically for the stationary fluid, uniform compressible flow, and boundary layer flow. The conditions that trigger shock waves for sound wave, weak discontinuity, and Tollmien-Schlichting (T-S) wave in compressible flows are investigated. The relations between the three types of waves and shocklets are further analyzed and discussed. Different stages of the shocklet formation process are simulated. The results show that the three waves in compressible flows will transfer to shocklets only when the initial disturbance amplitudes are greater than the certain threshold values. In compressible boundary layers, the shocklets evolved from T-S wave exist only in a finite region near the surface instead of the whole wavefront.
Reference Based Genome Compression
Chern, Bobbie; Manolakos, Alexandros; No, Albert; Venkat, Kartik; Weissman, Tsachy
2012-01-01
DNA sequencing technology has advanced to a point where storage is becoming the central bottleneck in the acquisition and mining of more data. Large amounts of data are vital for genomics research, and generic compression tools, while viable, cannot offer the same savings as approaches tuned to inherent biological properties. We propose an algorithm to compress a target genome given a known reference genome. The proposed algorithm first generates a mapping from the reference to the target genome, and then compresses this mapping with an entropy coder. As an illustration of the performance: applying our algorithm to James Watson's genome with hg18 as a reference, we are able to reduce the 2991 megabyte (MB) genome down to 6.99 MB, while Gzip compresses it to 834.8 MB.
Singh, Shikha; Singhal, Vanika; Majumdar, Angshul
2016-01-01
This work addresses the problem of extracting deeply learned features directly from compressive measurements. There has been no work in this area. Existing deep learning tools only give good results when applied on the full signal, that too usually after preprocessing. These techniques require the signal to be reconstructed first. In this work we show that by learning directly from the compressed domain, considerably better results can be obtained. This work extends the recently proposed fram...
Reference Based Genome Compression
Chern, Bobbie; Ochoa, Idoia; Manolakos, Alexandros; No, Albert; Venkat, Kartik; Weissman, Tsachy
2012-01-01
DNA sequencing technology has advanced to a point where storage is becoming the central bottleneck in the acquisition and mining of more data. Large amounts of data are vital for genomics research, and generic compression tools, while viable, cannot offer the same savings as approaches tuned to inherent biological properties. We propose an algorithm to compress a target genome given a known reference genome. The proposed algorithm first generates a mapping from the reference to the target gen...
Geyer, A.; Martí, J.; Villaseñor, A.
2016-06-01
In volcanic areas, the existing stress field is a key parameter controlling magma generation, location and geometry of the magmatic plumbing systems and the distribution of the resulting volcanism at surface. Therefore, knowing the stress configuration in the lithosphere at any scale (i.e. local, regional and plate-scale) is fundamental to understand the distribution of volcanism and, subsequently, to interpret volcanic unrest and potential tectonic controls of future eruptions. The objective of the present work is to provide a first-order estimate of the plate-scale tectonic stresses acting on the Canary Islands, one of the largest active intraplate volcanic regions of the World. In order to obtain the orientation of the minimum and maximum horizontal compressive stresses, we perform a series of 2D finite element models of plate scale kinematics assuming plane stress approximation. Results obtained are used to develop a regional model, which takes into account recognized archipelago-scale structural discontinuities. Maximum horizontal compressive stress directions obtained are compared with available stress, geological and geodynamic data. The methodology used may be easily applied to other active volcanic regions, where a first order approach of their plate/regional stresses can be essential information to be used as input data for volcanic hazard assessment models.
Alternative Compression Garments
Stenger, M. B.; Lee, S. M. C.; Ribeiro, L. C.; Brown, A. K.; Westby, C. M.; Platts, S. H.
2011-01-01
Orthostatic intolerance after spaceflight is still an issue for astronauts as no in-flight countermeasure has been 100% effective. Future anti-gravity suits (AGS) may be similar to the Shuttle era inflatable AGS or may be a mechanical compression device like the Russian Kentavr. We have evaluated the above garments as well as elastic, gradient compression garments of varying magnitude and determined that breast-high elastic compression garments may be a suitable replacement to the current AGS. This new garment should be more comfortable than the AGS, easy to don and doff, and as effective a countermeasure to orthostatic intolerance. Furthermore, these new compression garments could be worn for several days after space flight as necessary if symptoms persisted. We conducted two studies to evaluate elastic, gradient compression garments. The purpose of these studies was to evaluate the comfort and efficacy of an alternative compression garment (ACG) immediately after actual space flight and 6 degree head-down tilt bed rest as a model of space flight, and to determine if they would impact recovery if worn for up to three days after bed rest.
郑文杰; 贺鸿志; 黄峙; 杨芳; 郭宝江
2003-01-01
研究了硒(Na 2SeO3)和碲(Na 2TeO 3)胁迫对钝顶螺旋藻(Spirulina platensis)和极大螺旋藻(Spirulina maximum)生长的影响.结果表明,两种藻对硒、碲表现出不同的耐性.对于S.platenis,CSe≤200mg/L促进生长,CTe＜100mg/L影响不大,CTe≥100mg/L抑制生长,CSa≥800mg/L或CTe=400mg/L藻死亡;而对于S.maiximum,CSe=25 mg/L时促进生长,CTe≤25mg/L无影响,CTe≥50 mg/L明显抑制生长,Cse≥800mg/L或CTe≥600 mg/L则死亡.而在培养周期内分次添加硒、碲,当累计达到CSe(CTe)=800mg/L,两种藻仍能正常生长.表明硒、碲添加方式不同,产生明显不同的效应.
Crack buckling in soft gels under compression
Rong Long; Chung-Yuen Hui
2012-01-01
Recent interest in designing soft gels with high fracture toughness has called for simple and robust methods to test fracture behavior.The conventional method of applying tension to a gel sample suffers from a difficulty of sample gripping.In this paper,we study a possible fracture mechanism of soft gels under uni-axial compression.We show that the surfaces of a pre-existing crack,oriented parallel to the loading axis,can buckle at a critical compressive stress.This buckling instability can open the crack surfaces and create highly concentrated stress fields near the crack tip,which can lead to crack growth.We show that the onset of crack buckling can be deduced by a dimensional argument combined with an analysis to determine the critical compression needed to induce surface instabilities of an elastic half space.The critical compression for buckling was verified for a neoHookean material model using finite element simulations.
Dynamic compressive behavior of foamed polyethylene film
Tateyama Kohei
2015-01-01
Full Text Available The foamed film as the shock absorption material has attracted much attention because it is thin (100 μm ∼ 400 μm and has a closed cell structure. However, the dynamic mechanical properties have not been reported in the foamed film. The purpose of this study is to elucidate the compressive behavior of the foamed polyethylene film at the wide strain rate range. First, the new compressive test apparatus for the dynamic strain rate, the drop-weight testing machine with opposed load cell, was developed, which can be also evaluated the dynamic stress equilibrium of the specimen. It is confirmed that the compressive flow stress increased with increasing the strain rate, regardless of the film thickness. The foamed polyethylene film has the high strain rate sensitivity in the quasi-static deformation. On the other hand, there is almost no change of the strain rate sensitivity in the dynamic and the impact deformation. In order to investigate the mechanism of strain rate dependence, the foamed polyethylene film was observed by X-ray computed tomography scanner before and after compressive test. The fracture of the closed cell only occurred in the quasi-static deformation. It was clarified that the strain rate sensitivity of the foamed film depends strongly on that of the construction material, polyethylene.
Engelder, Terry; Peacock, David C. P.
2001-02-01
Alpine inversion in the Bristol Channel Basin includes reverse-reactivated normal faults with hanging wall buttress anticlines. At Lilstock Beach, joint sets in Lower Jurassic limestone beds cluster about the trend of the hinge of the Lilstock buttress anticline. In horizontal and gently north-dipping beds, J3 joints ( 295-285° strike) are rare, while other joint sets indicate an anticlockwise sequence of development. In the steeper south-dipping beds, J3 joints are the most frequent in the vicinity of the reverse-reactivated normal fault responsible for the anticline. The J3 joints strike parallel to the fold hinge, and their poles tilt to the south when bedding is restored to horizontal. This southward tilt aims at the direction of σ 1 for Alpine inversion. Finite-element analysis is used to explain the southward tilt of J3 joints that propagate under a local σ 3 in the direction of σ 1 for Alpine inversion. Tilted principal stresses are characteristic of limestone-shale sequences that are sheared during parallel (flexural-flow) folding. Shear tractions on the dipping beds generate a tensile stress in the stiffer limestone beds even when remote principal stresses are compressive. This situation favors the paradoxical opening of joints in the direction of the regional maximum horizontal stress. We conclude that J3 joints propagated during the Alpine compression caused the growth of the Lilstock buttress anticline.
Envera Variable Compression Ratio Engine
Charles Mendler
2011-03-15
the compression ratio can be raised (to as much as 18:1) providing high engine efficiency. It is important to recognize that for a well designed VCR engine cylinder pressure does not need to be higher than found in current production turbocharged engines. As such, there is no need for a stronger crankcase, bearings and other load bearing parts within the VCR engine. The Envera VCR mechanism uses an eccentric carrier approach to adjust engine compression ratio. The crankshaft main bearings are mounted in this eccentric carrier or 'crankshaft cradle' and pivoting the eccentric carrier 30 degrees adjusts compression ratio from 9:1 to 18:1. The eccentric carrier is made up of a casting that provides rigid support for the main bearings, and removable upper bearing caps. Oil feed to the main bearings transits through the bearing cap fastener sockets. The eccentric carrier design was chosen for its low cost and rigid support of the main bearings. A control shaft and connecting links are used to pivot the eccentric carrier. The control shaft mechanism features compression ratio lock-up at minimum and maximum compression ratio settings. The control shaft method of pivoting the eccentric carrier was selected due to its lock-up capability. The control shaft can be rotated by a hydraulic actuator or an electric motor. The engine shown in Figures 3 and 4 has a hydraulic actuator that was developed under the current program. In-line 4-cylinder engines are significantly less expensive than V engines because an entire cylinder head can be eliminated. The cost savings from eliminating cylinders and an entire cylinder head will notably offset the added cost of the VCR and supercharging. Replacing V6 and V8 engines with in-line VCR 4-cylinder engines will provide high fuel economy at low cost. Numerous enabling technologies exist which have the potential to increase engine efficiency. The greatest efficiency gains are realized when the right combination of advanced and new
Working Characteristics of Variable Intake Valve in Compressed Air Engine
Qihui Yu
2014-01-01
Full Text Available A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine.
Working characteristics of variable intake valve in compressed air engine.
Yu, Qihui; Shi, Yan; Cai, Maolin
2014-01-01
A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine.
Information preserving image compression for archiving NMR images.
Li, C C; Gokmen, M; Hirschman, A D; Wang, Y
1991-01-01
This paper presents a result on information preserving compression of NMR images for the archiving purpose. Both Lynch-Davisson coding and linear predictive coding have been studied. For NMR images of 256 x 256 x 12 resolution, the Lynch-Davisson coding with a block size of 64 as applied to prediction error sequences in the Gray code bit planes of each image gave an average compression ratio of 2.3:1 for 14 testing images. The predictive coding with a third order linear predictor and the Huffman encoding of the prediction error gave an average compression ratio of 3.1:1 for 54 images under test, while the maximum compression ratio achieved was 3.8:1. This result is one step further toward the improvement, albeit small, of the information preserving image compression for medical applications.
OECD Maximum Residue Limit Calculator
With the goal of harmonizing the calculation of maximum residue limits (MRLs) across the Organisation for Economic Cooperation and Development, the OECD has developed an MRL Calculator. View the calculator.
Compression-compression fatigue of selective electron beam melted cellular titanium (Ti-6Al-4V).
Hrabe, Nikolas W; Heinl, Peter; Flinn, Brian; Körner, Carolin; Bordia, Rajendra K
2011-11-01
Regular 3D periodic porous Ti-6Al-4V structures intended to reduce the effects of stress shielding in load-bearing bone replacement implants (e.g., hip stems) were fabricated over a range of relative densities (0.17-0.40) and pore sizes (approximately 500-1500 μm) using selective electron beam melting (EBM). Compression-compression fatigue testing (15 Hz, R = 0.1) resulted in normalized fatigue strengths at 10(6) cycles ranging from 0.15 to 0.25, which is lower than the expected value of 0.4 for solid material of the same acicular α microstructure. The three possible reasons for this reduced fatigue lifetime are stress concentrations from closed porosity observed within struts, stress concentrations from observed strut surface features (sintered particles and texture lines), and microstructure (either acicular α or martensite) with less than optimal high-cycle fatigue resistance. 2011 Wiley Periodicals, Inc.
Transverse Compression of Tendons.
Salisbury, S T Samuel; Buckley, C Paul; Zavatsky, Amy B
2016-04-01
A study was made of the deformation of tendons when compressed transverse to the fiber-aligned axis. Bovine digital extensor tendons were compression tested between flat rigid plates. The methods included: in situ image-based measurement of tendon cross-sectional shapes, after preconditioning but immediately prior to testing; multiple constant-load creep/recovery tests applied to each tendon at increasing loads; and measurements of the resulting tendon displacements in both transverse directions. In these tests, friction resisted axial stretch of the tendon during compression, giving approximately plane-strain conditions. This, together with the assumption of a form of anisotropic hyperelastic constitutive model proposed previously for tendon, justified modeling the isochronal response of tendon as that of an isotropic, slightly compressible, neo-Hookean solid. Inverse analysis, using finite-element (FE) simulations of the experiments and 10 s isochronal creep displacement data, gave values for Young's modulus and Poisson's ratio of this solid of 0.31 MPa and 0.49, respectively, for an idealized tendon shape and averaged data for all the tendons and E = 0.14 and 0.10 MPa for two specific tendons using their actual measured geometry. The compression load versus displacement curves, as measured and as simulated, showed varying degrees of stiffening with increasing load. This can be attributed mostly to geometrical changes in tendon cross section under load, varying according to the initial 3D shape of the tendon.
Klein, Fred W.
2016-04-01
Several lines of earthquake evidence indicate that the lithospheric plate is broken under the load of the island of Hawai`i, where the geometry of the lithosphere is circular with a central depression. The plate bends concave downward surrounding a stress-free hole, rather than bending concave upward as with past assumptions. Earthquake focal mechanisms show that the center of load stress and the weak hole is between the summits of Mauna Loa and Mauna Kea where the load is greatest. The earthquake gap at 21 km depth coincides with the predicted neutral plane of flexure where horizontal stress changes sign. Focal mechanism P axes below the neutral plane display a striking radial pattern pointing to the stress center. Earthquakes above the neutral plane in the north part of the island have opposite stress patterns; T axes tend to be radial. The M6.2 Honomu and M6.7 Kiholo main shocks (both at 39 km depth) are below the neutral plane and show radial compression, and the M6.0 Kiholo aftershock above the neutral plane has tangential compression. Earthquakes deeper than 20 km define a donut of seismicity around the stress center where flexural bending is a maximum. The hole is interpreted as the soft center where the lithospheric plate is broken. Kilauea's deep conduit is seismically active because it is in the ring of maximum bending. A simplified two-dimensional stress model for a bending slab with a load at one end yields stress orientations that agree with earthquake stress axes and radial P axes below the neutral plane. A previous inversion of deep Hawaiian focal mechanisms found a circular solution around the stress center that agrees with the model. For horizontal faults, the shear stress within the bending slab matches the slip in the deep Kilauea seismic zone and enhances outward slip of active flanks.
ANALYTICAL SOLUTION OF BENDING-COMPRESSION COLUMN USING DIFFERENT TENSION-COMPRESSION MODULUS
姚文娟; 叶志明
2004-01-01
Based on elastic theory of different tension-compression modulus, the analytical solution was deduced for bending-compression column subject to combined loadings by the flowing coordinate system and phased integration method. The formulations for the neutral axis, stress, strain and displacement were developed, the finite element program was compiled for calculation, and the comparison between the result of finite element and analytical solution were given too. Finally, compare and analyze the result of different modulus and the same modulus, obtain the difference of two theories in result, and propose the reasonable suggestion for the calculation of this structure.
Bei, H.; Lu, Z. P.; Shim, S.; Chen, G.; George, E. P.
2010-07-01
Specimen size effects on the mechanical behavior of Zr-based bulk metallic glasses (BMGs) were investigated by compression and nanoindentation tests. In compression, even at the 1- to 10-mm scale, stable shear band propagation and extensive plastic deformation can be achieved in small (2 mm) specimens, in contrast to large (6.5 mm) specimens, which fail catastrophically after limited plastic deformation. The yield strength is independent of specimen size in this range, and plastic deformation remains highly localized in a few shear bands even in those specimens that exhibit stable shear sliding. The fracture surfaces of small specimens are smooth, without the vein patterns normally observed as characteristic features on the fracture surfaces of BMGs. During spherical nanoindentation, it is found that the upper bound of the maximum shear stress to initiate plasticity (yielding) in a Zr-based BMG is almost constant for indenter radii smaller than ~90 µm. However, the lower bound of this maximum shear stress decreases with increasing indenter radius, probably due to the increased probability of finding defects underneath larger indenters.
SYMBOLIC VERSOR COMPRESSION ALGORITHM
Li Hongbo
2009-01-01
In an inner-product space, an invertible vector generates a reflection with re-spect to a hyperplane, and the Clifford product of several invertible vectors, called a versor in Clifford algebra, generates the composition of the corresponding reflections, which is an orthogonal transformation. Given a versor in a Clifford algebra, finding another sequence of invertible vectors of strictly shorter length but whose Clifford product still equals the input versor, is called versor compression. Geometrically, versor compression is equivalent to decomposing an orthogoual transformation into a shorter sequence of reflections. This paper proposes a simple algorithm of compressing versors of symbolic form in Clifford algebra. The algorithm is based on computing the intersections of lines with planes in the corresponding Grassmann-Cayley algebra, and is complete in the case of Euclidean or Minkowski inner-product space.
Image compression for dermatology
Cookson, John P.; Sneiderman, Charles; Colaianni, Joseph; Hood, Antoinette F.
1990-07-01
Color 35mm photographic slides are commonly used in dermatology for education, and patient records. An electronic storage and retrieval system for digitized slide images may offer some advantages such as preservation and random access. We have integrated a system based on a personal computer (PC) for digital imaging of 35mm slides that depict dermatologic conditions. Such systems require significant resources to accommodate the large image files involved. Methods to reduce storage requirements and access time through image compression are therefore of interest. This paper contains an evaluation of one such compression method that uses the Hadamard transform implemented on a PC-resident graphics processor. Image quality is assessed by determining the effect of compression on the performance of an image feature recognition task.
Determination of residual stresses within plasma spray coating using Moiré interferometry method
Yi, Jiang; Bin-shi, Xu; Hai-dou, Wang; Ming, Liu; Yao-hui, Lu
2011-01-01
In this paper, residual stresses of the Ni-Cr-B-Si coatings prepared by supersonic plasma spray processing were measured by moiré interferometry and X-ray diffraction method. Moiré interferometry method was used in measuring the distribution of residual stresses of the Ni-Cr-B-Si coatings alongside the specimen thickness direction, then the distribution of residual stresses both in the substrate and the coating was also analyzed. Experimental results showed that residual stresses in the coating and the substrate are tensile and compressive separately; residual stresses of the coating are diminished with the increase of the distance from the coating surface and almost zero at the coating-substrate interface; the maximum of compressive residual stresses of the substrate are present to the vicinity of the coating-substrate interface. It could be concluded that residual stresses in the specimen would result from the dismatch of thermophysical properties between the coating and substrate during the spray process, and the distribution of residual stresses of the substrate would be influenced by the sandblasting prior to spraying.
Maximum margin Bayesian network classifiers.
Pernkopf, Franz; Wohlmayr, Michael; Tschiatschek, Sebastian
2012-03-01
We present a maximum margin parameter learning algorithm for Bayesian network classifiers using a conjugate gradient (CG) method for optimization. In contrast to previous approaches, we maintain the normalization constraints on the parameters of the Bayesian network during optimization, i.e., the probabilistic interpretation of the model is not lost. This enables us to handle missing features in discriminatively optimized Bayesian networks. In experiments, we compare the classification performance of maximum margin parameter learning to conditional likelihood and maximum likelihood learning approaches. Discriminative parameter learning significantly outperforms generative maximum likelihood estimation for naive Bayes and tree augmented naive Bayes structures on all considered data sets. Furthermore, maximizing the margin dominates the conditional likelihood approach in terms of classification performance in most cases. We provide results for a recently proposed maximum margin optimization approach based on convex relaxation. While the classification results are highly similar, our CG-based optimization is computationally up to orders of magnitude faster. Margin-optimized Bayesian network classifiers achieve classification performance comparable to support vector machines (SVMs) using fewer parameters. Moreover, we show that unanticipated missing feature values during classification can be easily processed by discriminatively optimized Bayesian network classifiers, a case where discriminative classifiers usually require mechanisms to complete unknown feature values in the data first.
Maximum Entropy in Drug Discovery
Chih-Yuan Tseng
2014-07-01
Full Text Available Drug discovery applies multidisciplinary approaches either experimentally, computationally or both ways to identify lead compounds to treat various diseases. While conventional approaches have yielded many US Food and Drug Administration (FDA-approved drugs, researchers continue investigating and designing better approaches to increase the success rate in the discovery process. In this article, we provide an overview of the current strategies and point out where and how the method of maximum entropy has been introduced in this area. The maximum entropy principle has its root in thermodynamics, yet since Jaynes’ pioneering work in the 1950s, the maximum entropy principle has not only been used as a physics law, but also as a reasoning tool that allows us to process information in hand with the least bias. Its applicability in various disciplines has been abundantly demonstrated. We give several examples of applications of maximum entropy in different stages of drug discovery. Finally, we discuss a promising new direction in drug discovery that is likely to hinge on the ways of utilizing maximum entropy.
Ohlsson, Henrik; Eldar, Yonina C.; Yang, Allen Y.; Sastry, S. Shankar
2014-08-01
The classical shift retrieval problem considers two signals in vector form that are related by a shift. The problem is of great importance in many applications and is typically solved by maximizing the cross-correlation between the two signals. Inspired by compressive sensing, in this paper, we seek to estimate the shift directly from compressed signals. We show that under certain conditions, the shift can be recovered using fewer samples and less computation compared to the classical setup. Of particular interest is shift estimation from Fourier coefficients. We show that under rather mild conditions only one Fourier coefficient suffices to recover the true shift.
Alberto Apostolico
2009-08-01
Full Text Available The Web Graph is a large-scale graph that does not fit in main memory, so that lossless compression methods have been proposed for it. This paper introduces a compression scheme that combines efficient storage with fast retrieval for the information in a node. The scheme exploits the properties of the Web Graph without assuming an ordering of the URLs, so that it may be applied to more general graphs. Tests on some datasets of use achieve space savings of about 10% over existing methods.
Image data compression investigation
Myrie, Carlos
1989-01-01
NASA continuous communications systems growth has increased the demand for image transmission and storage. Research and analysis was conducted on various lossy and lossless advanced data compression techniques or approaches used to improve the efficiency of transmission and storage of high volume stellite image data such as pulse code modulation (PCM), differential PCM (DPCM), transform coding, hybrid coding, interframe coding, and adaptive technique. In this presentation, the fundamentals of image data compression utilizing two techniques which are pulse code modulation (PCM) and differential PCM (DPCM) are presented along with an application utilizing these two coding techniques.
苏佳灿; 王瑞官; 张春才; 薛召军; 吴建国; 丁祖泉
2005-01-01
背景:肱骨骨折治疗中经常遇到的主要问题在于应力加载的方向与应力加载的力值.目的:分析天鹅记忆加压接骨器固定肱骨时不同应力加载的选择,为今后肱骨骨折治疗时内固定器械的放置部位、载荷的施加方向及大小等提供力学依据.设计:进行不同应力加载的条件下,构建肱骨骨折的三维有限元模型.单位:解放军第二军医大学附属长海医院骨科和同济大学生命科学与生物工程学院.材料:实验于2001-01/2003-05在解放军第二军医大学长海医院骨科实验室和同济大学生命科学与生物工程学院实验室完成.选取湿成年尸体肱骨标本和与之相对应型号的天鹅型记忆接骨器.方法:选择湿肱骨标本行CT成像得到肱骨每层横截面图像,采用大型有限元分析软件ANSYS 5.6建立肱骨、天鹅型记忆接骨器以及天鹅型记忆接骨器固定肱骨的三维模型.主要观察指标:对比不同加载方式下肱骨的受力情况,寻求临床治疗的参考数值.结果:所构建天鹅型记忆接骨器固定肱骨三维模型,逼真反映真实解剖形态及生物力学行为,同时获得不同加载方式下肱骨的受力情况.结论:天鹅型记忆接骨器固定肱骨三维有限元模型的构建,可以为肱骨正常力学行为以及骨折后内固定的力学基础研究提供精确模型.%BACKGROUND: During the therapy of the fracture of humerus, the main problem is the loading direction and power of the stress.OBJECTIVE: To analyze the choice of the different loading manners using Swain Memory Compression Bone Reduction Apparatus so as to provide the clinical evidence for the set position of the internal fixation apparatus, the loading direction and power during the therapy of the fracture of humerus.DESIGN: To construct the three-dimensional finite element model of the fracture of humerus with different loading manners.SETTING: Department of Orthopaedics of Changhai Hospital of
Image compression in local helioseismology
Löptien, Björn; Gizon, Laurent; Schou, Jesper
2014-01-01
Context. Several upcoming helioseismology space missions are very limited in telemetry and will have to perform extensive data compression. This requires the development of new methods of data compression. Aims. We give an overview of the influence of lossy data compression on local helioseismology. We investigate the effects of several lossy compression methods (quantization, JPEG compression, and smoothing and subsampling) on power spectra and time-distance measurements of supergranulation flows at disk center. Methods. We applied different compression methods to tracked and remapped Dopplergrams obtained by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory. We determined the signal-to-noise ratio of the travel times computed from the compressed data as a function of the compression efficiency. Results. The basic helioseismic measurements that we consider are very robust to lossy data compression. Even if only the sign of the velocity is used, time-distance helioseismology is still...
Compressible Navier-Stokes Equations with Revised Maxwell's Law
Hu, Yuxi; Racke, Reinhard
2017-03-01
We investigate the compressible Navier-Stokes equations where the constitutive law for the stress tensor given by Maxwell's law is revised to a system of relaxation equations for two parts of the tensor. The global well-posedness is proved as well as the compatibility with the classical compressible Navier-Stokes system in the sense that, for vanishing relaxation parameters, the solutions to the Maxwell system are shown to converge to solutions of the classical system.
Biomechanics of turtle shells: how whole shells fail in compression.
Magwene, Paul M; Socha, John J
2013-02-01
Turtle shells are a form of armor that provides varying degrees of protection against predation. Although this function of the shell as armor is widely appreciated, the mechanical limits of protection and the modes of failure when subjected to breaking stresses have not been well explored. We studied the mechanical properties of whole shells and of isolated bony tissues and sutures in four species of turtles (Trachemys scripta, Malaclemys terrapin, Chrysemys picta, and Terrapene carolina) using a combination of structural and mechanical tests. Structural properties were evaluated by subjecting whole shells to compressive and point loads in order to quantify maximum load, work to failure, and relative shell deformations. The mechanical properties of bone and sutures from the plastral region of the shell were evaluated using three-point bending experiments. Analysis of whole shell structural properties suggests that small shells undergo relatively greater deformations before failure than do large shells and similar amounts of energy are required to induce failure under both point and compressive loads. Location of failures occurred far more often at sulci than at sutures (representing the margins of the epidermal scutes and the underlying bones, respectively), suggesting that the small grooves in the bone created by the sulci introduce zones of weakness in the shell. Values for bending strength, ultimate bending strain, Young's modulus, and energy absorption, calculated from the three-point bending data, indicate that sutures are relatively weaker than the surrounding bone, but are able to absorb similar amounts of energy due to higher ultimate strain values. Copyright © 2012 Wiley Periodicals, Inc.
The uniaxial compressive strength of the Arctic summer sea ice
HAN Hongwei; LI Zhijun; HUANG Wenfeng; LU Peng; LEI Ruibo
2015-01-01
The results on the uniaxial compressive strength of Arctic summer sea ice are presented based on the sam-ples collected during the fifth Chinese National Arctic Research Expedition in 2012 (CHINARE-2012). Exper-imental studies were carried out at different testing temperatures (−3, −6 and −9°C), and vertical samples were loaded at stress rates ranging from 0.001 to 1 MPa/s. The temperature, density, and salinity of the ice were measured to calculate the total porosity of the ice. In order to study the effects of the total porosity and the density on the uniaxial compressive strength, the measured strengths for a narrow range of stress rates from 0.01 to 0.03 MPa/s were analyzed. The results show that the uniaxial compressive strength decreases linearly with increasing total porosity, and when the density was lower than 0.86 g/cm3, the uniaxial com-pressive strength increases in a power-law manner with density. The uniaxial compressive behavior of the Arctic summer sea ice is sensitive to the loading rate, and the peak uniaxial compressive strength is reached in the brittle-ductile transition range. The dependence of the strength on the temperature shows that the calculated average strength in the brittle-ductile transition range, which was considered as the peak uniaxial compressive strength, increases steadily in the temperature range from −3 to −9°C.
Chronic nerve root entrapment: compression and degeneration
Vanhoestenberghe, A.
2013-02-01
Electrode mounts are being developed to improve electrical stimulation and recording. Some are tight-fitting, or even re-shape the nervous structure they interact with, for a more selective, fascicular, access. If these are to be successfully used chronically with human nerve roots, we need to know more about the possible damage caused by the long-term entrapment and possible compression of the roots following electrode implantation. As there are, to date, no such data published, this paper presents a review of the relevant literature on alternative causes of nerve root compression, and a discussion of the degeneration mechanisms observed. A chronic compression below 40 mmHg would not compromise the functionality of the root as far as electrical stimulation and recording applications are concerned. Additionally, any temporary increase in pressure, due for example to post-operative swelling, should be limited to 20 mmHg below the patient’s mean arterial pressure, with a maximum of 100 mmHg. Connective tissue growth may cause a slower, but sustained, pressure increase. Therefore, mounts large enough to accommodate the root initially without compressing it, or compliant, elastic, mounts, that may stretch to free a larger cross-sectional area in the weeks after implantation, are recommended.
Negative linear compressibility in common materials
Miller, W.; Evans, K. E.; Marmier, A., E-mail: A.S.H.Marmier@exeter.ac.uk [College of Engineering Mathematics and Physical Science, University of Exeter, Exeter EX4 4QF (United Kingdom)
2015-06-08
Negative linear compressibility (NLC) is still considered an exotic property, only observed in a few obscure crystals. The vast majority of materials compress axially in all directions when loaded in hydrostatic compression. However, a few materials have been observed which expand in one or two directions under hydrostatic compression. At present, the list of materials demonstrating this unusual behaviour is confined to a small number of relatively rare crystal phases, biological materials, and designed structures, and the lack of widespread availability hinders promising technological applications. Using improved representations of elastic properties, this study revisits existing databases of elastic constants and identifies several crystals missed by previous reviews. More importantly, several common materials-drawn polymers, certain types of paper and wood, and carbon fibre laminates-are found to display NLC. We show that NLC in these materials originates from the misalignment of polymers/fibres. Using a beam model, we propose that maximum NLC is obtained for misalignment of 26°. The existence of such widely available materials increases significantly the prospects for applications of NLC.
Finding maximum JPEG image block code size
Lakhani, Gopal
2012-07-01
We present a study of JPEG baseline coding. It aims to determine the minimum storage needed to buffer the JPEG Huffman code bits of 8-bit image blocks. Since DC is coded separately, and the encoder represents each AC coefficient by a pair of run-length/AC coefficient level, the net problem is to perform an efficient search for the optimal run-level pair sequence. We formulate it as a two-dimensional, nonlinear, integer programming problem and solve it using a branch-and-bound based search method. We derive two types of constraints to prune the search space. The first one is given as an upper-bound for the sum of squares of AC coefficients of a block, and it is used to discard sequences that cannot represent valid DCT blocks. The second type constraints are based on some interesting properties of the Huffman code table, and these are used to prune sequences that cannot be part of optimal solutions. Our main result is that if the default JPEG compression setting is used, space of minimum of 346 bits and maximum of 433 bits is sufficient to buffer the AC code bits of 8-bit image blocks. Our implementation also pruned the search space extremely well; the first constraint reduced the initial search space of 4 nodes down to less than 2 nodes, and the second set of constraints reduced it further by 97.8%.
Fingerprints in Compressed Strings
Bille, Philip; Cording, Patrick Hagge; Gørtz, Inge Li
2013-01-01
The Karp-Rabin fingerprint of a string is a type of hash value that due to its strong properties has been used in many string algorithms. In this paper we show how to construct a data structure for a string S of size N compressed by a context-free grammar of size n that answers fingerprint queries...
Multiple snapshot compressive beamforming
Gerstoft, Peter; Xenaki, Angeliki; Mecklenbrauker, Christoph F.
2015-01-01
For sound fields observed on an array, compressive sensing (CS) reconstructs the multiple source signals at unknown directions-of-arrival (DOAs) using a sparsity constraint. The DOA estimation is posed as an underdetermined problem expressing the field at each sensor as a phase-lagged superposition...
Compressive CFAR radar detection
Anitori, L.; Otten, M.P.G.; Rossum, W.L. van; Maleki, A.; Baraniuk, R.
2012-01-01
In this paper we develop the first Compressive Sensing (CS) adaptive radar detector. We propose three novel architectures and demonstrate how a classical Constant False Alarm Rate (CFAR) detector can be combined with ℓ1-norm minimization. Using asymptotic arguments and the Complex Approximate Messag
Compressive CFAR Radar Processing
Anitori, L.; Rossum, W.L. van; Otten, M.P.G.; Maleki, A.; Baraniuk, R.
2013-01-01
In this paper we investigate the performance of a combined Compressive Sensing (CS) Constant False Alarm Rate (CFAR) radar processor under different interference scenarios using both the Cell Averaging (CA) and Order Statistic (OS) CFAR detectors. Using the properties of the Complex Approximate Mess
Beamforming Using Compressive Sensing
2011-10-01
dB to align the peak at 7.3o. Comparing peaks to val- leys , compressive sensing provides a greater main to interference (and noise) ratio...elements. Acknowledgments This research was supported by the Office of Naval Research. The authors would like to especially thank of Roger Gauss and Joseph
Fejerskov, Morten
1996-12-31
In-situ rock stresses have proved to be important for exploration and production of hydrocarbons. This thesis uses various stress determination techniques to characterize the in-situ stress field on the Norwegian Continental Shelf. Leak off tests and borehole breakouts have been used to determine the in-situ stress in deep well bores. Overcoring and earthquake focal mechanisms data have also been compiled and evaluated together with stress information from petroleum wells. A new test procedure is suggested to improve the quality of leak off tests that emphasises the importance of accurate pressure determination, longer test periods and digital data sampling. Four-arm calliper logs are used to identify borehole breakouts on the Tampen Spur and Horda Platform. However, it proved difficult to distinguish borehole breakouts from other drilling processes since the elongations of the borehole consistently appeared in the direction of hole azimuth; drilling-induced key seats are here observed in vertical wells. This behaviour is discussed but not fully understood. This reduces the number of reliable stress data and their quality enormously and even casts some doubt about the quality of previous breakout studies from the North Sea. A highly compressive horizontal stress field seems to be present onshore and offshore Norway. Different stress determination techniques yield very consistent stress orientation, regional and internal variation. A 1. order stress direction is identified, where the maximum horizontal stress direction is rotating from N-S in the Barents Sea to NW-SE in the Norwegian Sea and WNW-ESE in the northern North Sea. At Tampen Spur, a dominant WNW-ESE maximum horizontal stress direction, normal to the major tectonic structures is identified as well as a minimum stress close to the vertical stress, the latter indicating high horizontal stresses. 250 refs., 91 figs., 14 tabs.
Huang, Kuo-Ting; Chen, Hsi-Chao; Cheng, Po-Wei; Chang, Jhe-Ming
2016-01-01
Transparent conductive Al-doped ZnO (AZO) thin films were deposited onto poly(ethylene terephthalate) (PET) substrate, using the radio frequency (RF) magnetron sputtering method. The residual stress of flexible electronics was investigated by a double beam shadow moiré interferometer with phase shifting interferometry (PSI). Moreover, the biaxial stress of AZO thin films can be graphically represented by using Mohr’s circle of stress. The residual stress of AZO thin films becomes more compressive with the increase in sputtering power. The maximum residual stress is -1115.74 MPa, and the shearing stress is 490.57 MPa at a sputtering power of 200 W. The trends of residual stress were evidenced by the X-ray diffraction (XRD) patterns and optical properties of AZO thin films. According to the evaluation results of the refractive index and the extinction coefficient, the AZO thin films have better quality when the sputtering power less than 100 W.
HE Zhen-jun; SONG Yu-pu
2008-01-01
Multiaxial compression tests were performed on 100 mm × 100 mm × 100 nun high-strength high-performance concrete (HSHPC) cubes and normal strength concrete (NSC) cubes. The failure modes of specimens were presented, the static compressive strengths in principal directions were measured, the influence of the stress ratios was analyzed. The experimental results show that the ultimate strengths for HSHPC and NSC under multiaxial compression are greater than the uniaxial compressive strengths at all stress ratios, and the multiaxial strength is dependent on the brittleness and stiffness of concrete, the stress state and the stress ratios. In addition, the Kupfer-Gerstle and Ottosen's failure criteria for plain HSHPC and NSC under multiaxial compressive loading were modified.
Mills, T.; Reece, J. S.
2016-12-01
Here we investigate the influence of microbial activity on the mechanical and transport properties of mudstones during early diagenesis. Despite the proven presence of microbial communities in marine sediments to depths of >500 meters below sea floor (mbsf), little is known about the interactions between microorganisms and sediments, especially during the early stages of burial and compression. To characterize and quantify the impact of microbial activity on mudstone properties, we compare natural mudstone samples treated with iron reducing bacteria Shewanella Oneidensis MR-1 and those without bacteria. Two bulk mudstones are experimentally prepared using sediments from Integrated Ocean Drilling Program Sites U1319 and U1324 in the Gulf of Mexico. The sediments originated from 4-13 mbsf in the Brazos-Trinity Basin and from three depth intervals (3-14 mbsf, 23-32 mbsf, and 493-502 mbsf) in the Ursa Basin. The sediments are dried and ground to clay- and silt-sized particles and homogenized into two natural mudstone powders. These powders are then used to make reproducible mudstone samples through a process called resedimentation, which replicates natural deposition and burial. Changes in microstructure, porosity, compressibility, and permeability are measured while the biotic (with bacteria) and abiotic (without bacteria) mudstones are being uniaxially compressed over several weeks to a maximum stress of 100 kPa. We anticipate that biofilm growth in pore spaces will decrease porosity, compressibility, and permeability, and the resultant microstructural changes created by microorganisms will be evident in high-resolution scanning electron microscope (SEM) images. Recognition of the micro-scale processes that take place during the early stages of mudstone diagenesis, especially those mediated by microbial activity, and their long-term effects on mudstone properties can lead to better identification and more effective production of unconventional hydrocarbon reservoirs.
Greenslade, Thomas B., Jr.
1985-01-01
Discusses a series of experiments performed by Thomas Hope in 1805 which show the temperature at which water has its maximum density. Early data cast into a modern form as well as guidelines and recent data collected from the author provide background for duplicating Hope's experiments in the classroom. (JN)
Abolishing the maximum tension principle
Dabrowski, Mariusz P
2015-01-01
We find the series of example theories for which the relativistic limit of maximum tension $F_{max} = c^2/4G$ represented by the entropic force can be abolished. Among them the varying constants theories, some generalized entropy models applied both for cosmological and black hole horizons as well as some generalized uncertainty principle models.
Abolishing the maximum tension principle
Mariusz P. Da̧browski
2015-09-01
Full Text Available We find the series of example theories for which the relativistic limit of maximum tension Fmax=c4/4G represented by the entropic force can be abolished. Among them the varying constants theories, some generalized entropy models applied both for cosmological and black hole horizons as well as some generalized uncertainty principle models.
EVALUATION OF REGISTRATION, COMPRESSION AND CLASSIFICATION ALGORITHMS
Jayroe, R. R.
1994-01-01
Several types of algorithms are generally used to process digital imagery such as Landsat data. The most commonly used algorithms perform the task of registration, compression, and classification. Because there are different techniques available for performing registration, compression, and classification, imagery data users need a rationale for selecting a particular approach to meet their particular needs. This collection of registration, compression, and classification algorithms was developed so that different approaches could be evaluated and the best approach for a particular application determined. Routines are included for six registration algorithms, six compression algorithms, and two classification algorithms. The package also includes routines for evaluating the effects of processing on the image data. This collection of routines should be useful to anyone using or developing image processing software. Registration of image data involves the geometrical alteration of the imagery. Registration routines available in the evaluation package include image magnification, mapping functions, partitioning, map overlay, and data interpolation. The compression of image data involves reducing the volume of data needed for a given image. Compression routines available in the package include adaptive differential pulse code modulation, two-dimensional transforms, clustering, vector reduction, and picture segmentation. Classification of image data involves analyzing the uncompressed or compressed image data to produce inventories and maps of areas of similar spectral properties within a scene. The classification routines available include a sequential linear technique and a maximum likelihood technique. The choice of the appropriate evaluation criteria is quite important in evaluating the image processing functions. The user is therefore given a choice of evaluation criteria with which to investigate the available image processing functions. All of the available
Comparative compressibility of hydrous wadsleyite
Chang, Y.; Jacobsen, S. D.; Thomas, S.; Bina, C. R.; Smyth, J. R.; Frost, D. J.; Hauri, E. H.; Meng, Y.; Dera, P. K.
2010-12-01
Determining the effects of hydration on the density and elastic properties of wadsleyite, β-Mg2SiO4, is critical to constraining Earth’s global geochemical water cycle. Whereas previous studies of the bulk modulus (KT) have studied either hydrous Mg-wadsleyite, or anhydrous Fe-bearing wadsleyite, the combined effects of hydration and iron are under investigation. Also, whereas KT from compressibility studies is relatively well constrained by equation of state fitting to P-V data, the pressure derivative of the bulk modulus (K’) is usually not well constrained either because of poor data resolution, uncertainty in pressure calibrations, or narrow pressure ranges of previous single-crystal studies. Here we report the comparative compressibility of dry versus hydrous wadsleyite with Fo90 composition containing 1.9(2) wt% H2O, nearly the maximum water storage capacity of this phase. The composition was characterized by EMPA and nanoSIMS. The experiments were carried out using high-pressure, single-crystal diffraction up to 30 GPa at HPCAT, Advanced Photon Source. By loading three crystals each of hydrous and anhydrous wadsleyite together in the same diamond-anvil cell, we achieve good hkl coverage and eliminate the pressure scale as a variable in comparing the relative value of K’ between the dry and hydrous samples. We used MgO as an internal diffraction standard, in addition to recording ruby fluorescence pressures. By using neon as a pressure medium and about 1 GPa pressure steps up to 30 GPa, we obtain high-quality diffraction data for constraining the effect of hydration on the density and K’ of hydrous wadsleyite. Due to hydration, the initial volume of hydrous Fo90 wadsleyite is larger than anhydrous Fo90 wadsleyite, however the higher compressibility of hydrous wadsleyite leads to a volume crossover at 6 GPa. Hydration to 2 wt% H2O reduces the bulk modulus of Fo90 wadsleyite from 170(2) to 157(2) GPa, or about 7.6% reduction. In contrast to previous
Xiao, Pan [LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); Kang, Zhitao; Summers, Christopher J. [Phosphor Technology Center of Excellence, Georgia Tech Research Institute, Georgia Institute of Technology, Atlanta, Georgia 30332-0826 (United States); Bansihev, Alexandr A.; Christensen, James M.; Dlott, Dana D. [School of Chemical Sciences and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Breidenich, Jennifer; Scripka, David A.; Thadhani, Naresh N. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States); Zhou, Min, E-mail: min.zhou@gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0405 (United States); School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245 (United States)
2016-01-04
Laser-driven shock compression experiments and corresponding finite element method simulations are carried out to investigate the blueshift in the optical emission spectra under continuous laser excitation of a dilute composite consisting of 0.15% CdTe quantum dots by weight embedded in polyvinyl alcohol polymer. This material is a potential candidate for use as internal stress sensors. The analyses focus on the time histories of the wavelength blue-shift for shock loading with pressures up to 7.3 GPa. The combined measurements and calculations allow a relation between the wavelength blueshift and pressure for the loading conditions to be extracted. It is found that the blueshift first increases with pressure to a maximum and subsequently decreases with pressure. This trend is different from the monotonic increase of blueshift with pressure observed under conditions of quasistatic hydrostatic compression. Additionally, the blueshift in the shock experiments is much smaller than that in hydrostatic experiments at the same pressure levels. The differences in responses are attributed to the different stress states achieved in the shock and hydrostatic experiments and the time dependence of the mechanical response of the polymer in the composite. The findings offer a potential guide for the design and development of materials for internal stress sensors for shock conditions.
The strength of ruby from X-ray diffraction under non-hydrostatic compression to 68 GPa
Dong, Haini; Dorfman, Susannah M.; Wang, Jianghua; He, Duanwei; Duffy, Thomas S.
2014-07-01
Polycrystalline ruby (α-Al2O3:Cr3+), a widely used pressure calibrant in high-pressure experiments, was compressed to 68.1 GPa at room temperature under non-hydrostatic conditions in a diamond anvil cell. Angle-dispersive X-ray diffraction experiments in a radial geometry were conducted at beamline X17C of the National Synchrotron Light Source. The stress state of ruby at high pressure and room temperature was analyzed based on the measured lattice strain. The differential stress of ruby increases with pressure from ~3.4 % of the shear modulus at 18.5 GPa to ~6.5 % at 68.1 GPa. The polycrystalline ruby sample can support a maximum differential stress of ~16 GPa at 68.1 GPa under non-hydrostatic compression. The results of this study provide a better understanding of the mechanical properties of this important material for high-pressure science. From a synthesis of existing data for strong ceramic materials, we find that the high-pressure yield strength correlates well with the ambient pressure Vickers hardness.
Seismicity and state of stress in the central and southern Peruvian flat slab
Kumar, Abhash; Wagner, Lara S.; Beck, Susan L.; Long, Maureen D.; Zandt, George; Young, Bissett; Tavera, Hernando; Minaya, Estella
2016-05-01
We have determined the Wadati-Benioff Zone seismicity and state of stress of the subducting Nazca slab beneath central and southern Peru using data from three recently deployed local seismic networks. Our relocated hypocenters are consistent with a flat slab geometry that is shallowest near the Nazca Ridge, and changes from steep to normal without tearing to the south. These locations also indicate numerous abrupt along-strike changes in seismicity, most notably an absence of seismicity along the projected location of subducting Nazca Ridge. This stands in stark contrast to the very high seismicity observed along the Juan Fernandez ridge beneath central Chile where, a similar flat slab geometry is observed. We interpret this as indicative of an absence of water in the mantle beneath the overthickened crust of the Nazca Ridge. This may provide important new constraints on the conditions required to produce intermediate depth seismicity. Our focal mechanisms and stress tensor inversions indicate dominantly down-dip extension, consistent with slab pull, with minor variations that are likely due to the variable slab geometry and stress from adjacent regions. We observe significantly greater variability in the P-axis orientations and maximum compressive stress directions. The along strike change in the orientation of maximum compressive stress is likely related to slab bending and unbending south of the Nazca Ridge.
A FLOW STRESS MODEL FOR AZ61 MAGNESIUM ALLOY
H.T.Zhou; X.Q.Zeng; Q.D Wang; W.J.Ding
2004-01-01
The flow stress behaviors of AZ61 alloy has been investigated at temperature range from 523 to 673K with the strain rates of 0.001-1s-1.It is found that the average activation energy,strain rate sensitive exponent and stress exponent are different at various deformation conditions changing from 1i3.6 to 176.3k J/mol,0.125 to 0.167 and 6 to 8 respectively.A flow stress model for AZ61 alloy is derived by analyzing the stress data based on hot compression test.It is demonstrated that the flow stress model including strain hardening exponent and strain softening exponent is suitable to predicate the flow stress.The prediction of the flow stress of AZ61 alloy has shown to be good agreement with the test data.The maximum differences of the peak stresses calculated by the model and obtained by experiment is less than 8%.
Tectonic stress - Models and magnitudes
Solomon, S. C.; Bergman, E. A.; Richardson, R. M.
1980-01-01
It is shown that global data on directions of principal stresses in plate interiors can serve as a test of possible plate tectonic force models. Such tests performed to date favor force models in which ridge pushing forces play a significant role. For such models the general magnitude of regional deviatoric stresses is comparable to the 200-300 bar compressive stress exerted by spreading ridges. An alternative approach to estimating magnitudes of regional deviatoric stresses from stress orientations is to seek regions of local stress either demonstrably smaller than or larger than the regional stresses. The regional stresses in oceanic intraplate regions are larger than the 100-bar compression exerted by the Ninetyeast Ridge and less than the bending stresses (not less than 1 kbar) beneath Hawaii.
Randomness Testing of Compressed Data
Chang, Weiling; Yun, Xiaochun; Wang, Shupeng; Yu, Xiangzhan
2010-01-01
Random Number Generators play a critical role in a number of important applications. In practice, statistical testing is employed to gather evidence that a generator indeed produces numbers that appear to be random. In this paper, we reports on the studies that were conducted on the compressed data using 8 compression algorithms or compressors. The test results suggest that the output of compression algorithms or compressors has bad randomness, the compression algorithms or compressors are not suitable as random number generator. We also found that, for the same compression algorithm, there exists positive correlation relationship between compression ratio and randomness, increasing the compression ratio increases randomness of compressed data. As time permits, additional randomness testing efforts will be conducted.
Shape memory and transformation behavior of high strength 60NiTi in compression
Kaya, I.
2016-12-01
This study investigates the transformation behavior of highly Ni-rich 60NiTi alloys after aging at 600 °C for 3 h. After 600 °C-3h aging, R-phase disappeared and alloy transformed in one step. The latent heats of austenite to martensite and martensite to austenite transformations were 13 Jg-1 and 16.4 Jg-1, respectively, for 600 °C-3h aged alloy. The elastic strain energy of 0.75 Jg-1 was obtained in aged alloy. The maximum recoverable transformation strain of 1.7% is obtained under 500 MPa in compression. The superelastic behavior was observed accompanied with a recoverable strain of 1.4%, even high stress level of 1000 MPa is applied.
Stevens, Andrew J.; Kovarik, Libor; Abellan, Patricia; Yuan, Xin; Carin, Lawrence; Browning, Nigel D.
2015-08-02
One of the main limitations of imaging at high spatial and temporal resolution during in-situ TEM experiments is the frame rate of the camera being used to image the dynamic process. While the recent development of direct detectors has provided the hardware to achieve frame rates approaching 0.1ms, the cameras are expensive and must replace existing detectors. In this paper, we examine the use of coded aperture compressive sensing methods [1, 2, 3, 4] to increase the framerate of any camera with simple, low-cost hardware modifications. The coded aperture approach allows multiple sub-frames to be coded and integrated into a single camera frame during the acquisition process, and then extracted upon readout using statistical compressive sensing inversion. Our simulations show that it should be possible to increase the speed of any camera by at least an order of magnitude. Compressive Sensing (CS) combines sensing and compression in one operation, and thus provides an approach that could further improve the temporal resolution while correspondingly reducing the electron dose rate. Because the signal is measured in a compressive manner, fewer total measurements are required. When applied to TEM video capture, compressive imaging couled improve acquisition speed and reduce the electron dose rate. CS is a recent concept, and has come to the forefront due the seminal work of Candès [5]. Since the publication of Candès, there has been enormous growth in the application of CS and development of CS variants. For electron microscopy applications, the concept of CS has also been recently applied to electron tomography [6], and reduction of electron dose in scanning transmission electron microscopy (STEM) imaging [7]. To demonstrate the applicability of coded aperture CS video reconstruction for atomic level imaging, we simulate compressive sensing on observations of Pd nanoparticles and Ag nanoparticles during exposure to high temperatures and other environmental
Effect of compressive loading on the risk of spalling
Carré H.
2013-09-01
Full Text Available Mechanical loading is an important parameter of spalling phenomenon likely to occur in concrete during heating. Several tests in laboratory have shown an increase of the risk of spalling in the compressed areas. In this study, a specific metallic frame has been developed to apply uniaxial and biaxial stresses on slabs during fire tests. Tests carried out on an ordinary concrete (fc28 = 37 MPa exposed to ISO 834-1 temperature curve with several levels of uniaxial loading are presented. No spalling was observed when samples were loaded at 0, 5 and 10 MPa. In the opposite, spalling was observed when the compressive stress was increased to 15 MPa.
Maximum Work of Free-Piston Stirling Engine Generators
Kojima, Shinji
2017-04-01
Using the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is negative even when the duration of heat addition is optimized to give the maximum amount of heat addition, which is the same situation for the Brayton cycle described in our previous paper. For the Stirling cycle, the net work done is positive, and the thermal efficiency is greater than that of the Otto cycle described in our previous paper by a factor of about 2.7-1.4 for compression ratios of 5-30. The Stirling cycle is much better than the Otto, Brayton, and Carnot cycles. We have found that the optimized piston trajectories of the isothermal, isobaric, and adiabatic processes are the same when the compression ratio and the maximum volume of the same working fluid of the three processes are the same, which has facilitated the present analysis because the optimized piston trajectories of the Carnot and Stirling cycles are the same as those of the Brayton and Otto cycles, respectively.
Tree compression with top trees
Bille, Philip; Gørtz, Inge Li; Landau, Gad M.;
2015-01-01
We introduce a new compression scheme for labeled trees based on top trees. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...
Tree compression with top trees
Bille, Philip; Gørtz, Inge Li; Landau, Gad M.
2013-01-01
We introduce a new compression scheme for labeled trees based on top trees [3]. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...
Tree compression with top trees
Bille, Philip; Gørtz, Inge Li; Landau, Gad M.
2015-01-01
We introduce a new compression scheme for labeled trees based on top trees. Our compression scheme is the first to simultaneously take advantage of internal repeats in the tree (as opposed to the classical DAG compression that only exploits rooted subtree repeats) while also supporting fast...
Reinterpreting Compression in Infinitary Rewriting
Ketema, J.; Tiwari, Ashish
2012-01-01
Departing from a computational interpretation of compression in infinitary rewriting, we view compression as a degenerate case of standardisation. The change in perspective comes about via two observations: (a) no compression property can be recovered for non-left-linear systems and (b) some standar
Lossless Compression of Broadcast Video
Martins, Bo; Eriksen, N.; Faber, E.
1998-01-01
We investigate several techniques for lossless and near-lossless compression of broadcast video.The emphasis is placed on the emerging international standard for compression of continous-tone still images, JPEG-LS, due to its excellent compression performance and moderatecomplexity. Except for one...
Maximum Genus of Strong Embeddings
Er-ling Wei; Yan-pei Liu; Han Ren
2003-01-01
The strong embedding conjecture states that any 2-connected graph has a strong embedding on some surface. It implies the circuit double cover conjecture: Any 2-connected graph has a circuit double cover.Conversely, it is not true. But for a 3-regular graph, the two conjectures are equivalent. In this paper, a characterization of graphs having a strong embedding with exactly 3 faces, which is the strong embedding of maximum genus, is given. In addition, some graphs with the property are provided. More generally, an upper bound of the maximum genus of strong embeddings of a graph is presented too. Lastly, it is shown that the interpolation theorem is true to planar Halin graph.
Remizov, Ivan D
2009-01-01
In this note, we represent a subdifferential of a maximum functional defined on the space of all real-valued continuous functions on a given metric compact set. For a given argument, $f$ it coincides with the set of all probability measures on the set of points maximizing $f$ on the initial compact set. This complete characterization lies in the heart of several important identities in microeconomics, such as Roy's identity, Sheppard's lemma, as well as duality theory in production and linear programming.
Li, Qihong; Ren, Shuang; Ge, Cheng; Sun, Haiyan; Lu, Hong; Duan, Yinzhong; Rong, Qiguo
2014-06-19
Excessive compressive and shear stresses are likely related to condylar resorption and disc perforation. Few studies have reported the disc displacement and deformation during jaw opening. The aim of this study was to analyze stress distribution in a normal articular disc during the jaw opening movement. Bilateral MRI images were obtained from the temporomandibular joint of a healthy subject for the jaw opening displacement from 6 to 24 mm with 1 mm increments. The disc contour for the jaw opening at 6 mm was defined as the reference state, and was used to establish a two dimensional finite element model of the disc. The contours of the disc at other degrees of jaw opening were used as the displacement loading. Hyperelastic material models were applied to the anterior, intermediate and posterior parts of the disc. Stress and strain trajectories were calculated to characterize the stress/strain patterns in the disc. Both the maximum and minimum principal stresses were negative in the intermediate zone, therefore, the intermediate zone withstood mainly compressive stress. On the contrary, the maximum and minimum principal stresses were most positive in the anterior and posterior zones, which meant that the anterior and posterior bands suffered higher tensile stresses. The different patterns of stress trajectories between the intermediate zone and the anterior and posterior bands might be attributed to the effect of fiber orientation. The compression of the intermediate zone and stretching of the anterior and posterior bands caused high shear deformation in the transition region, especially at the disc surfaces. The stress and strain remained at a reasonable level during jaw opening, indicating that the disc experiences no injury during functional opening movements in a healthy temporomandibular joint.
The Testability of Maximum Magnitude
Clements, R.; Schorlemmer, D.; Gonzalez, A.; Zoeller, G.; Schneider, M.
2012-12-01
Recent disasters caused by earthquakes of unexpectedly large magnitude (such as Tohoku) illustrate the need for reliable assessments of the seismic hazard. Estimates of the maximum possible magnitude M at a given fault or in a particular zone are essential parameters in probabilistic seismic hazard assessment (PSHA), but their accuracy remains untested. In this study, we discuss the testability of long-term and short-term M estimates and the limitations that arise from testing such rare events. Of considerable importance is whether or not those limitations imply a lack of testability of a useful maximum magnitude estimate, and whether this should have any influence on current PSHA methodology. We use a simple extreme value theory approach to derive a probability distribution for the expected maximum magnitude in a future time interval, and we perform a sensitivity analysis on this distribution to determine if there is a reasonable avenue available for testing M estimates as they are commonly reported today: devoid of an appropriate probability distribution of their own and estimated only for infinite time (or relatively large untestable periods). Our results imply that any attempt at testing such estimates is futile, and that the distribution is highly sensitive to M estimates only under certain optimal conditions that are rarely observed in practice. In the future we suggest that PSHA modelers be brutally honest about the uncertainty of M estimates, or must find a way to decrease its influence on the estimated hazard.
Alternative Multiview Maximum Entropy Discrimination.
Chao, Guoqing; Sun, Shiliang
2016-07-01
Maximum entropy discrimination (MED) is a general framework for discriminative estimation based on maximum entropy and maximum margin principles, and can produce hard-margin support vector machines under some assumptions. Recently, the multiview version of MED multiview MED (MVMED) was proposed. In this paper, we try to explore a more natural MVMED framework by assuming two separate distributions p1( Θ1) over the first-view classifier parameter Θ1 and p2( Θ2) over the second-view classifier parameter Θ2 . We name the new MVMED framework as alternative MVMED (AMVMED), which enforces the posteriors of two view margins to be equal. The proposed AMVMED is more flexible than the existing MVMED, because compared with MVMED, which optimizes one relative entropy, AMVMED assigns one relative entropy term to each of the two views, thus incorporating a tradeoff between the two views. We give the detailed solving procedure, which can be divided into two steps. The first step is solving our optimization problem without considering the equal margin posteriors from two views, and then, in the second step, we consider the equal posteriors. Experimental results on multiple real-world data sets verify the effectiveness of the AMVMED, and comparisons with MVMED are also reported.
Algorithm for Compressing Time-Series Data
Hawkins, S. Edward, III; Darlington, Edward Hugo
2012-01-01
An algorithm based on Chebyshev polynomials effects lossy compression of time-series data or other one-dimensional data streams (e.g., spectral data) that are arranged in blocks for sequential transmission. The algorithm was developed for use in transmitting data from spacecraft scientific instruments to Earth stations. In spite of its lossy nature, the algorithm preserves the information needed for scientific analysis. The algorithm is computationally simple, yet compresses data streams by factors much greater than two. The algorithm is not restricted to spacecraft or scientific uses: it is applicable to time-series data in general. The algorithm can also be applied to general multidimensional data that have been converted to time-series data, a typical example being image data acquired by raster scanning. However, unlike most prior image-data-compression algorithms, this algorithm neither depends on nor exploits the two-dimensional spatial correlations that are generally present in images. In order to understand the essence of this compression algorithm, it is necessary to understand that the net effect of this algorithm and the associated decompression algorithm is to approximate the original stream of data as a sequence of finite series of Chebyshev polynomials. For the purpose of this algorithm, a block of data or interval of time for which a Chebyshev polynomial series is fitted to the original data is denoted a fitting interval. Chebyshev approximation has two properties that make it particularly effective for compressing serial data streams with minimal loss of scientific information: The errors associated with a Chebyshev approximation are nearly uniformly distributed over the fitting interval (this is known in the art as the "equal error property"); and the maximum deviations of the fitted Chebyshev polynomial from the original data have the smallest possible values (this is known in the art as the "min-max property").
Building indifferentiable compression functions from the PGV compression functions
Gauravaram, P.; Bagheri, Nasour; Knudsen, Lars Ramkilde
2016-01-01
Preneel, Govaerts and Vandewalle (PGV) analysed the security of single-block-length block cipher based compression functions assuming that the underlying block cipher has no weaknesses. They showed that 12 out of 64 possible compression functions are collision and (second) preimage resistant. Black...... cipher is ideal. We address the problem of building indifferentiable compression functions from the PGV compression functions. We consider a general form of 64 PGV compression functions and replace the linear feed-forward operation in this generic PGV compression function with an ideal block cipher...... independent of the one used in the generic PGV construction. This modified construction is called a generic modified PGV (MPGV). We analyse indifferentiability of the generic MPGV construction in the ideal cipher model and show that 12 out of 64 MPGV compression functions in this framework...
Compressive Principal Component Pursuit
Wright, John; Min, Kerui; Ma, Yi
2012-01-01
We consider the problem of recovering a target matrix that is a superposition of low-rank and sparse components, from a small set of linear measurements. This problem arises in compressed sensing of structured high-dimensional signals such as videos and hyperspectral images, as well as in the analysis of transformation invariant low-rank recovery. We analyze the performance of the natural convex heuristic for solving this problem, under the assumption that measurements are chosen uniformly at random. We prove that this heuristic exactly recovers low-rank and sparse terms, provided the number of observations exceeds the number of intrinsic degrees of freedom of the component signals by a polylogarithmic factor. Our analysis introduces several ideas that may be of independent interest for the more general problem of compressed sensing and decomposing superpositions of multiple structured signals.
On Network Functional Compression
Feizi, Soheil
2010-01-01
In this paper, we consider different aspects of the network functional compression problem where computation of a function (or, some functions) of sources located at certain nodes in a network is desired at receiver(s). The rate region of this problem has been considered in the literature under certain restrictive assumptions, particularly in terms of the network topology, the functions and the characteristics of the sources. In this paper, we present results that significantly relax these assumptions. Firstly, we consider this problem for an arbitrary tree network and asymptotically lossless computation. We show that, for depth one trees with correlated sources, or for general trees with independent sources, a modularized coding scheme based on graph colorings and Slepian-Wolf compression performs arbitrarily closely to rate lower bounds. For a general tree network with independent sources, optimal computation to be performed at intermediate nodes is derived. We introduce a necessary and sufficient condition...
Zhou, Tianyi
2011-01-01
Compressed sensing (CS) and 1-bit CS cannot directly recover quantized signals and require time consuming recovery. In this paper, we introduce \\textit{Hamming compressed sensing} (HCS) that directly recovers a k-bit quantized signal of dimensional $n$ from its 1-bit measurements via invoking $n$ times of Kullback-Leibler divergence based nearest neighbor search. Compared with CS and 1-bit CS, HCS allows the signal to be dense, takes considerably less (linear) recovery time and requires substantially less measurements ($\\mathcal O(\\log n)$). Moreover, HCS recovery can accelerate the subsequent 1-bit CS dequantizer. We study a quantized recovery error bound of HCS for general signals and "HCS+dequantizer" recovery error bound for sparse signals. Extensive numerical simulations verify the appealing accuracy, robustness, efficiency and consistency of HCS.
Compressive Spectral Renormalization Method
Bayindir, Cihan
2016-01-01
In this paper a novel numerical scheme for finding the sparse self-localized states of a nonlinear system of equations with missing spectral data is introduced. As in the Petviashivili's and the spectral renormalization method, the governing equation is transformed into Fourier domain, but the iterations are performed for far fewer number of spectral components (M) than classical versions of the these methods with higher number of spectral components (N). After the converge criteria is achieved for M components, N component signal is reconstructed from M components by using the l1 minimization technique of the compressive sampling. This method can be named as compressive spectral renormalization (CSRM) method. The main advantage of the CSRM is that, it is capable of finding the sparse self-localized states of the evolution equation(s) with many spectral data missing.
Speech Compression and Synthesis
1980-10-01
phonological rules combined with diphone improved the algorithms used by the phonetic synthesis prog?Im for gain normalization and time... phonetic vocoder, spectral template. i0^Th^TreprtTörc"u’d1sTuV^ork for the past two years on speech compression’and synthesis. Since there was an...from Block 19: speech recognition, pnoneme recogmtion. initial design for a phonetic recognition program. We also recorded ana partially labeled a
Impact of Stress on Anomalous Transport in Fractured Rock
Kang, P. K.; Lei, Q.; Lee, S.; Dentz, M.; Juanes, R.
2016-12-01
rough fractures. Earth and Planetary Science Letters, to appear (2016). Figure (a) Map of maximum principal stress with a vertical normal compressive stress of 3 MPa at top and bottom boundaries, and 1MPa at left and right boundaries. (b) Normal compressive stress of 15 MPa at top and bottom boundaries, and 5MPa at left and right boundaries.
Quantifying porosity, compressibility and permeability in Shale
Mbia, Ernest Ncha; Fabricius, Ida Lykke; Frykman, Peter
(XRD) of shale samples show about 50% silt and high content of kaolinite in the clay fraction when compared with offshore samples from the Central Graben. Porosity measurements from helium porosimetry-mercury immersion (HPMI), mercury injection capillary pressure (MICP) and nuclear magnetic resonance...... (NMR) show that, the MICP porosity is 9-10% points lower than HPMI and NMR porosity. Compressibility result shows that deep shale is stiffer in situ than normally assumed in geotechnical modelling and that static compressibility corresponds with dynamic one only at the begining of unloading stress...... strain data. We found that Kozeny's modelled permeability fall in the same order of magnitude with measured permeability for shale rich in kaolinite but overestimates permeability by two to three orders of magnitudes for shale with high content of smectite. The empirical Yang and Aplin model gives good...
High reflection mirrors for pulse compression gratings.
Palmier, S; Neauport, J; Baclet, N; Lavastre, E; Dupuy, G
2009-10-26
We report an experimental investigation of high reflection mirrors used to fabricate gratings for pulse compression application at the wavelength of 1.053microm. Two kinds of mirrors are studied: the mixed Metal MultiLayer Dielectric (MMLD) mirrors which combine a gold metal layer with some e-beam evaporated dielectric bilayers on the top and the standard e-beam evaporated MultiLayer Dielectric (MLD) mirrors. Various samples were manufactured, damage tested at a pulse duration of 500fs. Damage sites were subsequently observed by means of Nomarski microscopy and white light interferometer microscopy. The comparison of the results evidences that if MMLD design can offer damage performances rather similar to MLD design, it also exhibits lower stresses; being thus an optimal mirror substrate for a pulse compression grating operating under vacuum.
Analysis of compressive fracture in rock using statistical techniques
Blair, S.C.
1994-12-01
Fracture of rock in compression is analyzed using a field-theory model, and the processes of crack coalescence and fracture formation and the effect of grain-scale heterogeneities on macroscopic behavior of rock are studied. The model is based on observations of fracture in laboratory compression tests, and incorporates assumptions developed using fracture mechanics analysis of rock fracture. The model represents grains as discrete sites, and uses superposition of continuum and crack-interaction stresses to create cracks at these sites. The sites are also used to introduce local heterogeneity. Clusters of cracked sites can be analyzed using percolation theory. Stress-strain curves for simulated uniaxial tests were analyzed by studying the location of cracked sites, and partitioning of strain energy for selected intervals. Results show that the model implicitly predicts both development of shear-type fracture surfaces and a strength-vs-size relation that are similar to those observed for real rocks. Results of a parameter-sensitivity analysis indicate that heterogeneity in the local stresses, attributed to the shape and loading of individual grains, has a first-order effect on strength, and that increasing local stress heterogeneity lowers compressive strength following an inverse power law. Peak strength decreased with increasing lattice size and decreasing mean site strength, and was independent of site-strength distribution. A model for rock fracture based on a nearest-neighbor algorithm for stress redistribution is also presented and used to simulate laboratory compression tests, with promising results.
Shock compression of nitrobenzene
Kozu, Naoshi; Arai, Mitsuru; Tamura, Masamitsu; Fujihisa, Hiroshi; Aoki, Katsutoshi; Yoshida, Masatake; Kondo, Ken-Ichi
1999-06-01
The Hugoniot (4 - 30 GPa) and the isotherm (1 - 7 GPa) of nitrobenzene have been investigated by shock and static compression experiments. Nitrobenzene has the most basic structure of nitro aromatic compounds, which are widely used as energetic materials, but nitrobenzene has been considered not to explode in spite of the fact its calculated heat of detonation is similar to TNT, about 1 kcal/g. Explosive plane-wave generators and diamond anvil cell were used for shock and static compression, respectively. The obtained Hugoniot consists of two linear lines, and the kink exists around 10 GPa. The upper line agrees well with the Hugoniot of detonation products calculated by KHT code, so it is expected that nitrobenzene detonates in that area. Nitrobenzene solidifies under 1 GPa of static compression, and the isotherm of solid nitrobenzene was obtained by X-ray diffraction technique. Comparing the Hugoniot and the isotherm, nitrobenzene is in liquid phase under experimented shock condition. From the expected phase diagram, shocked nitrobenzene seems to remain metastable liquid in solid phase region on that diagram.
Compressed sensing electron tomography
Leary, Rowan, E-mail: rkl26@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Saghi, Zineb; Midgley, Paul A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Holland, Daniel J. [Department of Chemical Engineering and Biotechnology, University of Cambridge, New Museums Site, Pembroke Street, Cambridge CB2 3RA (United Kingdom)
2013-08-15
The recent mathematical concept of compressed sensing (CS) asserts that a small number of well-chosen measurements can suffice to reconstruct signals that are amenable to sparse or compressible representation. In addition to powerful theoretical results, the principles of CS are being exploited increasingly across a range of experiments to yield substantial performance gains relative to conventional approaches. In this work we describe the application of CS to electron tomography (ET) reconstruction and demonstrate the efficacy of CS–ET with several example studies. Artefacts present in conventional ET reconstructions such as streaking, blurring of object boundaries and elongation are markedly reduced, and robust reconstruction is shown to be possible from far fewer projections than are normally used. The CS–ET approach enables more reliable quantitative analysis of the reconstructions as well as novel 3D studies from extremely limited data. - Highlights: • Compressed sensing (CS) theory and its application to electron tomography (ET) is described. • The practical implementation of CS–ET is outlined and its efficacy demonstrated with examples. • High fidelity tomographic reconstruction is possible from a small number of images. • The CS–ET reconstructions can be more reliably segmented and analysed quantitatively. • CS–ET is applicable to different image content by choice of an appropriate sparsifying transform.
Compression behavior of a ferritic-martensitic Cr-Mo steel
Zhang, Zhenbo; Mishin, Oleg; Pantleon, Wolfgang
2012-01-01
The compression behavior of a ferritic-martensitic Cr-Mo steel is characterized for strain rates ranging from 10-4 s-1 to 10-1 s-1 and engineering strains up to 40%. Adiabatic heating causes a reduction in flow stress during continuous compression at a strain rate of 10-1 s-1. No reduction...... in the flow stress is observed if interrupted compression tests are performed with loading and holding steps. Two work-hardening stages with work-hardening rates decreasing linearly with the flow stress are identified and interpreted in terms of the KocksMecking model. The microstructural evolution...
Electromechanical behaviour of REBCO tape lap splices under transverse compressive loading
Grether, A; Ballarino, A.; Bottura, L.
2016-01-01
We have studied the influence of transverse compressive stress on the resistance and critical current (Ic) of soldered REBCO tape lap splices. Internal contact resistances dominate the overall REBCO lap splice resistances. Application of transverse compressive stress up to 250 MPa during the resistance measurements does not alter the resistance and Ic of the soldered REBCO splices that were studied. The resistance of unsoldered REBCO tape lap splices depends strongly on the contact pressure. At a transverse compressive stress of 100 MPa to which Roebel cables are typically exposed in high field magnets, the crossover splice contact resistance is comparable to the internal tape resistances.
Ultraspectral sounder data compression review
Bormin HUANG; Hunglung HUANG
2008-01-01
Ultraspectral sounders provide an enormous amount of measurements to advance our knowledge of weather and climate applications. The use of robust data compression techniques will be beneficial for ultraspectral data transfer and archiving. This paper reviews the progress in lossless compression of ultra-spectral sounder data. Various transform-based, pre-diction-based, and clustering-based compression methods are covered. Also studied is a preprocessing scheme for data reordering to improve compression gains. All the coding experiments are performed on the ultraspectral compression benchmark dataset col-lected from the NASA Atmospheric Infrared Sounder (AIRS) observations.
Engineering Relative Compression of Genomes
Grabowski, Szymon
2011-01-01
Technology progress in DNA sequencing boosts the genomic database growth at faster and faster rate. Compression, accompanied with random access capabilities, is the key to maintain those huge amounts of data. In this paper we present an LZ77-style compression scheme for relative compression of multiple genomes of the same species. While the solution bears similarity to known algorithms, it offers significantly higher compression ratios at compression speed over a order of magnitude greater. One of the new successful ideas is augmenting the reference sequence with phrases from the other sequences, making more LZ-matches available.
Determination of Optimum Compression Ratio: A Tribological Aspect
L. Yüksek
2013-12-01
Full Text Available Internal combustion engines are the primary energy conversion machines both in industry and transportation. Modern technologies are being implemented to engines to fulfill today's low fuel consumption demand. Friction energy consumed by the rubbing parts of the engines are becoming an important parameter for higher fuel efficiency. Rate of friction loss is primarily affected by sliding speed and the load acting upon rubbing surfaces. Compression ratio is the main parameter that increases the peak cylinder pressure and hence normal load on components. Aim of this study is to investigate the effect of compression ratio on total friction loss of a diesel engine. A variable compression ratio diesel engine was operated at four different compression ratios which were "12.96", "15:59", "18:03", "20:17". Brake power and speed was kept constant at predefined value while measuring the in- cylinder pressure. Friction mean effective pressure ( FMEP data were obtained from the in cylinder pressure curves for each compression ratio. Ratio of friction power to indicated power of the engine was increased from 22.83% to 37.06% with varying compression ratio from 12.96 to 20:17. Considering the thermal efficiency , FMEP and maximum in- cylinder pressure optimum compression ratio interval of the test engine was determined as 18.8 ÷ 19.6.
Adaptation of existing facilities to isentropic compression experiments
Tasker, Douglas G [Los Alamos National Laboratory; Mielke, Charles H [Los Alamos National Laboratory; Rodriguez, George [Los Alamos National Laboratory; Rickel, Dwight G [Los Alamos National Laboratory
2011-01-07
We demonstrate that the established pulsed power infrastructure at the National High Magnetic Field Laboratory - Pulsed Field Facility (NHMFL-PFF) at the Los Alamos National Laboratory can be adapted to obtain high quality isentropic compression experiment (ICE) data on materials in extreme conditions of dynamic high pressure. Experiments utilized a single-turn magnet pulsed power system at the NHMFL-PFF that was originally designed to measure actinide samples in extremes of high magnetic field (to 300 Tesla). A simple modification to the single-turn magnet has converted it to a fast turnaround dynamic high pressure measurement system. This paper details the work done including important background details that indicate that much more can be accomplished with optimization of the load characteristics in terms of ultimate peak pressures. To match the rise time of the NHMFL capacitor bank ({approx}2 {mu}s versus {approx}0.5 {mu}s for the Sandia Z-machine) the sample dimensions can be relatively large, i.e., up to 5 mm thickness. The maximum stresses are {approx}50GPa (0.5 Mbar) at the maximum bank voltage (60 kV) and higher pressures may be possible if the sample is tamped. For the design and predictions of performance of the NHMFL-ICE experiment it is important to have good predictive models. A SPICE code simulation was chosen to model all aspects of the experiment, electrical and physical. To this end, accurate dynamic load models were developed to simulate the compression and expansion of the dynamic load at high pressures using shock physics principles. A series experiments have been performed which demonstrated the feasibility of the NHMFL-ICE technique. The results will be shown and discussed. The NHMFL-ICE technique is an excellent method for measuring equations of state (EOS) at megabar pressures. Because a complete EOS can be obtained in one experiment from zero to the peak pressure, and because many shots can be fired in one day, the technique promises to
Stress-magnetization properties of a silicon iron single crystal under stress
Saito, Akihiko; Hashimoto, Masaaki; Kawaguchi, Eiji; Murashige, Shinichi
1996-07-01
The effects of tensile and compressive stress on magnetization changes in a Si-Fe single crystal with a (110) surface and longitudinal directions declined from the [001] direction were investigated. We found a peculiar magnetization change, namely a reversible magnetization change due to stress consisting of two peak values in a constant magnetic field. The double peak characteristic appears in samples with angle smaller than 55° for compressive stress and with angle larger than 60° for tensile stress.
Compressive strength of fiber reinforced composite materials. [composed of boron and epoxy
Davis, J. G., Jr.
1974-01-01
Results of an experimental and analytical investigation of the compressive strength of unidirectional boron-epoxy composite material are presented. Observation of fiber coordinates in a boron-epoxy composite indicates that the fibers contain initial curvature. Combined axial compression and torsion tests were conducted on boron-epoxy tubes, and it was shown that the shear modulus is a function of axial compressive stress. An analytical model which includes initial curvature in the fibers and permits an estimate of the effect of curvature on compressive strength is proposed. Two modes of failure which may result from the application of axial compressive stress are analyzed, delamination and shear instability. Based on tests and analysis, failure of boron-epoxy under axial compressive load is due to shear instability.
Stress gradients in CrN coatings
Janssen, G.C.A.M.; Tichelaar, F.D.; Visser, C.C.G.
2006-01-01
Stress in hard films is the net sum of tensile stress generated at the grain boundaries, compressive stress due to ion peening, and thermal stress due to the difference in thermal expansion of the coating and substrate. The tensile part due to grain boundaries is thickness dependent. The other two c
T.R. Neelakantan; S. Ramasundaram; Shanmugavel, R.; R. Vinoth
2013-01-01
Predicting 28-day compressive strength of concrete is an important research task for many years. In this study, concrete specimens were cured in two phases, initially at room temperature for a maximum of 30 h and later at a higher temperature for accelerated curing for a maximum of 3 h. Using the early strength obtained after the two-phase curing and the curing parameters, regression equations were developed to predict the 28-day compressive strength. For the accelerated curing (higher temper...
Cacti with maximum Kirchhoff index
Wang, Wen-Rui; Pan, Xiang-Feng
2015-01-01
The concept of resistance distance was first proposed by Klein and Randi\\'c. The Kirchhoff index $Kf(G)$ of a graph $G$ is the sum of resistance distance between all pairs of vertices in $G$. A connected graph $G$ is called a cactus if each block of $G$ is either an edge or a cycle. Let $Cat(n;t)$ be the set of connected cacti possessing $n$ vertices and $t$ cycles, where $0\\leq t \\leq \\lfloor\\frac{n-1}{2}\\rfloor$. In this paper, the maximum kirchhoff index of cacti are characterized, as well...
Generic maximum likely scale selection
Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo
2007-01-01
The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...... on second order moments of multiple measurements outputs at a fixed location. These measurements, which reflect local image structure, consist in the cases considered here of Gaussian derivatives taken at several scales and/or having different derivative orders....
Near-wall modelling of compressible turbulent flows
So, Ronald M. C.
1990-01-01
Work was carried out to formulate near-wall models for the equations governing the transport of the temperature-variance and its dissipation rate. With these equations properly modeled, a foundation is laid for their extension together with the heat-flux equations to compressible flows. This extension is carried out in a manner similar to that used to extend the incompressible near-wall Reynolds-stress models to compressible flows. The methodology used to accomplish the extension of the near-wall Reynolds-stress models is examined and the actual extension of the models for the Reynolds-stress equations and the near-wall dissipation-rate equation to compressible flows is given. Then the formulation of the near-wall models for the equations governing the transport of the temperature variance and its dissipation rate is discussed. Finally, a sample calculation of a flat plate compressible turbulent boundary-layer flow with adiabatic wall boundary condition and a free-stream Mach number of 2.5 using a two-equation near-wall closure is presented. The results show that the near-wall two-equation closure formulated for compressible flows is quite valid and the calculated properties are in good agreement with measurements. Furthermore, the near-wall behavior of the turbulence statistics and structure parameters is consistent with that found in incompressible flows.
HU Mei-juan; LIU Jin-he
2009-01-01
Zonal heat treatment(ZHT) was conducted in situ to 14.5 mm-thick TC4 alloy plates by means of defocused electron beam after welding. The effects of ZHT on residual stresses, microstructures and mechanical properties of electron beam welded joints were investigated. Experimental results show residual stresses after welding are mostly relieved through ZHT, and the maximum values of longitudinal tensile stress and transverse compressive stress reduce by 76% and 65%, respectively. The tensile strength and ductility of welded joint after ZHT at slow scanning velocity are improved because of the reduction of residual stress and the microstructural changes of the base and weld metal. ZHT at fast scanning velocity is detrimental to the ductility of welded joint, which is resulted from insufficiently coarsened alpha phase in the fusion zone and the appearance of martensite in the base metal.
Economics and Maximum Entropy Production
Lorenz, R. D.
2003-04-01
Price differentials, sales volume and profit can be seen as analogues of temperature difference, heat flow and work or entropy production in the climate system. One aspect in which economic systems exhibit more clarity than the climate is that the empirical and/or statistical mechanical tendency for systems to seek a maximum in production is very evident in economics, in that the profit motive is very clear. Noting the common link between 1/f noise, power laws and Self-Organized Criticality with Maximum Entropy Production, the power law fluctuations in security and commodity prices is not inconsistent with the analogy. There is an additional thermodynamic analogy, in that scarcity is valued. A commodity concentrated among a few traders is valued highly by the many who do not have it. The market therefore encourages via prices the spreading of those goods among a wider group, just as heat tends to diffuse, increasing entropy. I explore some empirical price-volume relationships of metals and meteorites in this context.
WU Hao; FANG Qin; ZHANG Ya-dong; GONG Zi-ming
2009-01-01
The zonal disintegration phenomenon (ZDP) is a typical phenomenon in deep block rock masses. In order to investigate the mechanism of ZDP, an improved non-linear Hock-Brown strength criterion and a bi-linear constitutive model of rock mass were used to analyze the elasto-plastic stress field of the enclosing rock mass around a deep round tunnel. The radius of the plastic region and stress of the enclosing rock mass were obtained by introducing dimensionless parameters of radial distance. The results show that tunneling in deep rock mass causes a maximum stress zone to appear in the vicinity of the boundary of the elastic and the plas-tic zone in the surrounding rock mass. Under the compression of a large tangential force and a small radial force, the rock mass in the maximum stress zone was in an approximate uniaxial loading state, which could lead to a split failure in the rock mass.
Subramani Sockalingam
2017-02-01
Full Text Available High-velocity transverse impact of ballistic fabrics and yarns by projectiles subject individual fibers to multi-axial dynamic loading. Single-fiber transverse impact experiments with the current state-of-the-art experimental capabilities are challenging due to the associated micron length-scale. Kevlar® KM2 fibers exhibit a nonlinear inelastic behavior in transverse compression with an elastic limit less than 1.5% strain. The effect of this transverse behavior on a single KM2 fiber subjected to a cylindrical and a fragment-simulating projectile (FSP transverse impact is studied with a 3D finite element model. The inelastic behavior results in a significant reduction of fiber bounce velocity and projectile-fiber contact forces up to 38% compared to an elastic impact response. The multiaxial stress states during impact including transverse compression, axial tension, axial compression and interlaminar shear are presented at the location of failure. In addition, the models show a strain concentration over a small length in the fiber under the projectile-fiber contact. A failure criterion, based on maximum axial tensile strain accounting for the gage length, strain rate and multiaxial loading degradation effects are applied to predict the single-fiber breaking speed. Results are compared to the elastic response to assess the importance of inelastic material behavior on failure during a transverse impact.
Pankaj Thakur
2014-01-01
Full Text Available Thermal stress and strain rates in a thick walled rotating cylinder under steady state temperature has been derived by using Seth’s transition theory. For elastic-plastic stage, it is seen that with the increase of temperature, the cylinder having smaller radii ratios requires lesser angular velocity to become fully plastic as compared to cylinder having higher radii ratios The circumferential stress becomes larger and larger with the increase in temperature. With increase in thickness ratio stresses must be decrease. For the creep stage, it is seen that circumferential stresses for incompressible materials maximum at the internal surface as compared to compressible material, which increase with the increase in temperature and measure n.
Dynamic compressive behavior and constitutive relations of lanthanum metal
WANG Huanran; CAI Canyua; CHEN Danian; MA Dongfang; DENG Gaotao
2012-01-01
The dynamic compressive behavior and constitutive relations of Lanthanum (La) metal was determined by using the first compression in split Hopkinson pressure bar (SHPB) tests at different strain rates and temperatures.The constitutive relation of La metal determined in a certain range of strains was employed and adjusted in numerically simulating large deformations of La metal spEcimens generated by multi-compression in SHPB tests and recorded by a high-speed camera.The dynamic compressive behavior and constitutive relations of La metal under multiple SHPB tests loading was also revealed.The results of scanning electron microscope (SEM) investigation of the recovered La metal specimens for typical tests showed that there was a variety of deformation microstructures depending on strain rate,temperature and stress state.
COMPRESSIVE AND SHEAR ANALYSIS OF RUBBER BLOCK UNDER LARGE STRAIN
K. Sridharan
2013-01-01
Full Text Available The Elastomeric materials have found use in a wide range of applications, including hoses, tires, gaskets, seals, vibration isolators, bearings and dock fenders. The analysis of rubber blocks for its compression and shear behavior has been carried out using the imaging techniques. The dynamic stressing and its associated change in shape of the rubber blocks during large compression are very limited as their measurements were difficult. A newly developed Machine Vision based image processing test has been effectively used to study the deformation characteristics of the rubber blocks under large strains. An extended analysis on the rubber blocks has been carried out to understand the compression and deformation behavior in static and dynamic condition and the nonlinear behavior were also characterized. The rubber blocks of distinguished geometries have shown diverse change in shape and nonlinear deformation behavior under compression/shear loading.
Property of Corroded Concrete under Compressive Uniaxial Loads
FAN Yingfang; HU Zhiqiang; ZHOU Jing; LI Xin
2008-01-01
In order to study the compressive property of corroded concrete, accelerated corrosion test were performed on concrete C30.6 corrosive solutions, including hydraulic acid solution (pH=2), hydraulic acid solution (pH=3) were applied as the corrosive medium. 6 series of corrosion tests, including 111 specimens,were carried out. Mechanical properties of all the corroded specimens were tested respectively. Compressive properties of the corroded specimens (e.g. compressive strength, stress-strain relation, elastic modulus etc.) were achieved. Taking the strength degradation ratio and strain energy loss as damage index, effects of the corrosion solution on the compressive property of corroded concrete were discussed in detail. Relationship between the damage index and corrosion state of specimens were achieved.
Experimental Study on the Compressive Behavior of CFRP/ECCs
SUN Wen-bin
2010-01-01
In this study, nine square concrete columns, including six CFRP/ECCs and three plain concrete control specimen columns, were prepared. The CFRP tubes with fibers oriented in the hoop direction were manufactured with 10, 20, or 40 mm rounded corner radii at vertical edges. A 100 mm overlap in the direction of fibers was provided to ensure a proper bond. Uniaxial compression tests were conducted to investigate the compressive behaviors including the axial strength, stress-strain response, and ductility. It is evident that the CFRP tube confinement can improve the compressive behavior of concrete core, in terms of axial compressive strength or axial deformability. Based on the experimental results and some existing test database attained by other researchers, a design-oriented model is developed. The predictions of the model for CFRP/ECCs show good agreement with test results.
Whalley, E.
The compression of liquids can be measured either directly by applying a pressure and noting the volume change, or indirectly, by measuring the magnitude of the fluctuations of the local volume. The methods used in Ottawa for the direct measurement of the compression are reviewed. The mean-square deviation of the volume from the mean at constant temperature can be measured by X-ray and neutron scattering at low angles, and the meansquare deviation at constant entropy can be measured by measuring the speed of sound. The speed of sound can be measured either acoustically, using an acoustic transducer, or by Brillouin spectroscopy. Brillouin spectroscopy can also be used to study the shear waves in liquids if the shear relaxation time is > ∼ 10 ps. The relaxation time of water is too short for the shear waves to be studied in this way, but they do occur in the low-frequency Raman and infrared spectra. The response of the structure of liquids to pressure can be studied by neutron scattering, and recently experiments have been done at Atomic Energy of Canada Ltd, Chalk River, on liquid D 2O up to 15.6 kbar. They show that the near-neighbor intermolecular O-D and D-D distances are less spread out and at shorter distances at high pressure. Raman spectroscopy can also provide information on the structural response. It seems that the O-O distance in water decreases much less with pressure than it does in ice. Presumably, the bending of O-O-O angles tends to increase the O-O distance, and so to largely compensate the compression due to the direct effect of pressure.
Sun, Qilin
2017-04-01
High resolution transient/3D imaging technology is of high interest in both scientific research and commercial application. Nowadays, all of the transient imaging methods suffer from low resolution or time consuming mechanical scanning. We proposed a new method based on TCSPC and Compressive Sensing to achieve a high resolution transient imaging with a several seconds capturing process. Picosecond laser sends a serious of equal interval pulse while synchronized SPAD camera\\'s detecting gate window has a precise phase delay at each cycle. After capturing enough points, we are able to make up a whole signal. By inserting a DMD device into the system, we are able to modulate all the frames of data using binary random patterns to reconstruct a super resolution transient/3D image later. Because the low fill factor of SPAD sensor will make a compressive sensing scenario ill-conditioned, We designed and fabricated a diffractive microlens array. We proposed a new CS reconstruction algorithm which is able to denoise at the same time for the measurements suffering from Poisson noise. Instead of a single SPAD senor, we chose a SPAD array because it can drastically reduce the requirement for the number of measurements and its reconstruction time. Further more, it not easy to reconstruct a high resolution image with only one single sensor while for an array, it just needs to reconstruct small patches and a few measurements. In this thesis, we evaluated the reconstruction methods using both clean measurements and the version corrupted by Poisson noise. The results show how the integration over the layers influence the image quality and our algorithm works well while the measurements suffer from non-trival Poisson noise. It\\'s a breakthrough in the areas of both transient imaging and compressive sensing.
Compressive and tensile mechanical properties of the porcine nasal septum.
Al Dayeh, Ayman A; Herring, Susan W
2014-01-03
The expanding nasal septal cartilage is believed to create a force that powers midfacial growth. In addition, the nasal septum is postulated to act as a mechanical strut that prevents the structural collapse of the face under masticatory loads. Both roles imply that the septum is subject to complex biomechanical loads during growth and mastication. The purpose of this study was to measure the mechanical properties of the nasal septum to determine (1) whether the cartilage is mechanically capable of playing an active role in midfacial growth and in maintaining facial structural integrity and (2) if regional variation in mechanical properties is present that could support any of the postulated loading regimens. Porcine septal samples were loaded along the horizontal or vertical axes in compression and tension, using different loading rates that approximate the in vivo situation. Samples were loaded in random order to predefined strain points (2-10%) and strain was held for 30 or 120 seconds while relaxation stress was measured. Subsequently, samples were loaded until failure. Stiffness, relaxation stress and ultimate stress and strain were recorded. Results showed that the septum was stiffer, stronger and displayed a greater drop in relaxation stress in compression compared to tension. Under compression, the septum displayed non-linear behavior with greater stiffness and stress relaxation under faster loading rates and higher strain levels. Under tension, stiffness was not affected by strain level. Although regional variation was present, it did not strongly support any of the suggested loading patterns. Overall, results suggest that the septum might be mechanically capable of playing an active role in midfacial growth as evidenced by increased compressive residual stress with decreased loading rates. However, the low stiffness of the septum compared to surrounding bone does not support a strut role. The relatively low stiffness combined with high stress relaxation
Statistical Mechanical Analysis of Compressed Sensing Utilizing Correlated Compression Matrix
Takeda, Koujin
2010-01-01
We investigate a reconstruction limit of compressed sensing for a reconstruction scheme based on the L1-norm minimization utilizing a correlated compression matrix with a statistical mechanics method. We focus on the compression matrix modeled as the Kronecker-type random matrix studied in research on multi-input multi-output wireless communication systems. We found that strong one-dimensional correlations between expansion bases of original information slightly degrade reconstruction performance.
Risk of shear failure and extensional failure around over-stressed excavations in brittle rock
Nick Barton
2017-04-01
Full Text Available The authors investigate the failure modes surrounding over-stressed tunnels in rock. Three lines of investigation are employed: failure in over-stressed three-dimensional (3D models of tunnels bored under 3D stress, failure modes in two-dimensional (2D numerical simulations of 1000 m and 2000 m deep tunnels using FRACOD, both in intact rock and in rock masses with one or two joint sets, and finally, observations in TBM (tunnel boring machine tunnels in hard and medium hard massive rocks. The reason for ‘stress-induced’ failure to initiate, when the assumed maximum tangential stress is approximately (0.4–0.5σc (UCS, uniaxial compressive strength in massive rock, is now known to be due to exceedance of a critical extensional strain which is generated by a Poisson's ratio effect. However, because similar ‘stress/strength’ failure limits are found in mining, nuclear waste research excavations, and deep road tunnels in Norway, one is easily misled into thinking of compressive stress induced failure. Because of this, the empirical SRF (stress reduction factor in the Q-system is set to accelerate as the estimated ratio σθmax/σc >> 0.4. In mining, similar ‘stress/strength’ ratios are used to suggest depth of break-out. The reality behind the fracture initiation stress/strength ratio of ‘0.4’ is actually because of combinations of familiar tensile and compressive strength ratios (such as 10 with Poisson's ratio (say 0.25. We exceed the extensional strain limits and start to see acoustic emission (AE when tangential stress σθ ≈ 0.4σc, due to simple arithmetic. The combination of 2D theoretical FRACOD models and actual tunnelling suggests frequent initiation of failure by ‘stable’ extensional strain fracturing, but propagation in ‘unstable’ and therefore dynamic shearing. In the case of very deep tunnels (and 3D physical simulations, compressive stresses may be too high for extensional strain fracturing, and
Osmotic compressibility of soft colloidal systems.
Tan, Beng H; Tam, Kam C; Lam, Yee C; Tan, Chee B
2005-05-10
A turbidimetric analysis of particle interaction of model pH-responsive microgel systems consisting of methacrylic acid-ethyl acrylate cross-linked with diallyl phthalate in colloidal suspensions is described. The structure factor at zero scattering angle, S(0), can be determined with good precision for wavelengths greater than 500 nm, and it measures the dispersion's resistance to particle compression. The structure factor of microgels at various cross-linked densities and ionic strengths falls onto a master curve when plotted against the effective volume fraction, phi(eff) = kc, which clearly suggests that particle interaction potential and osmotic compressibility is a function of effective volume fraction. In addition, the deviation of the structure factor, S(0), of our microgel systems with the structure factor of hard spheres, S(PY)(0), exhibits a maximum at phi(eff) approximately 0.2. Beyond this point the osmotic de-swelling force exceeds the osmotic pressure inside the soft particles resulting in particle shrinkage. Good agreement was obtained when the structural properties of our microgel systems obtained from turbidimetric analysis and rheology measurements were compared. Therefore, a simple turbidimetric analysis of these model pH-responsive microgel systems permits a quantitative evaluation of factors governing particle osmotic compressibility.
On the compressibility and temperature boundary of warm frozen soils
Qi, Jilin; Dang, Boxiang; Guo, Xueluan; Sun, Xiaoyu; Yan, Xu
2017-04-01
A silty-clay obtained along the Qinghai-Tibetan railway and a standard Chinese sand were taken as study objects. Saturated frozen soil samples were prepared for testing. Step-load was used and confined compression was carried out on the soils under different temperatures. Compression index and pseudo-preconsolidation pressure (PPC) were obtained. Unlike unfrozen soils, PPC is not associated with stress history. However, it is still the boundary of elastic and plastic deformations. Different compression indexes can be obtained from an individual compression curve under pressures before and after PPC. The parameters at different thermal and stress conditions were analyzed. It is found that temperature plays a critical role in mechanical behaviours of frozen soils. Efforts were then made on the silty-clay in order to suggest a convincing temperature boundary in defining warm frozen soil. Three groups of ice-rich samples with different ice contents were prepared and tested under confined compression. The samples were compressed under a constant load and with 5 stepped temperatures. Strain rates at different temperatures were examined. It was found that the strain rate at around -0.6°C increased abruptly. Analysis of compression index was performed on the data both from our own testing program and from the literature, which showed that at about -1°C was a turning point in the curves for compression index against temperature. Based on both our work and taking into account the unfrozen water content vs. temperature, the range of -1°C to -0.5°C seems to be the temperature where the mechanical properties change greatly. For convenience, -1.0°C can be defined as the boundary for warm frozen soils.
Compressive full waveform lidar
Yang, Weiyi; Ke, Jun
2017-05-01
To avoid high bandwidth detector, fast speed A/D converter, and large size memory disk, a compressive full waveform LIDAR system, which uses a temporally modulated laser instead of a pulsed laser, is studied in this paper. Full waveform data from NEON (National Ecological Observatory Network) are used. Random binary patterns are used to modulate the source. To achieve 0.15 m ranging resolution, a 100 MSPS A/D converter is assumed to make measurements. SPIRAL algorithm with canonical basis is employed when Poisson noise is considered in the low illuminated condition.
Johnson, Terry A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Bowman, Robert [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Smith, Barton [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Anovitz, Lawrence [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Jensen, Craig [Hawaii Hydrogen Carriers LLC, Honolulu, HI (United States)
2017-07-01
Conventional hydrogen compressors often contribute over half of the cost of hydrogen stations, have poor reliability, and have insufficient flow rates for a mature FCEV market. Fatigue associated with their moving parts including cracking of diaphragms and failure of seal leads to failure in conventional compressors, which is exacerbated by the repeated starts and stops expected at fueling stations. Furthermore, the conventional lubrication of these compressors with oil is generally unacceptable at fueling stations due to potential fuel contamination. Metal hydride (MH) technology offers a very good alternative to both conventional (mechanical) and newly developed (electrochemical, ionic liquid pistons) methods of hydrogen compression. Advantages of MH compression include simplicity in design and operation, absence of moving parts, compactness, safety and reliability, and the possibility to utilize waste industrial heat to power the compressor. Beyond conventional H2 supplies of pipelines or tanker trucks, another attractive scenario is the on-site generating, pressuring and delivering pure H_{2} at pressure (≥ 875 bar) for refueling vehicles at electrolysis, wind, or solar generating production facilities in distributed locations that are too remote or widely distributed for cost effective bulk transport. MH hydrogen compression utilizes a reversible heat-driven interaction of a hydride-forming metal alloy with hydrogen gas to form the MH phase and is a promising process for hydrogen energy applications [1,2]. To deliver hydrogen continuously, each stage of the compressor must consist of multiple MH beds with synchronized hydrogenation & dehydrogenation cycles. Multistage pressurization allows achievement of greater compression ratios using reduced temperature swings compared to single stage compressors. The objectives of this project are to investigate and demonstrate on a laboratory scale a two-stage MH hydrogen (H_{2}) gas compressor with a
Beamforming using compressive sensing.
Edelmann, Geoffrey F; Gaumond, Charles F
2011-10-01
Compressive sensing (CS) is compared with conventional beamforming using horizontal beamforming of at-sea, towed-array data. They are compared qualitatively using bearing time records and quantitatively using signal-to-interference ratio. Qualitatively, CS exhibits lower levels of background interference than conventional beamforming. Furthermore, bearing time records show increasing, but tolerable, levels of background interference when the number of elements is decreased. For the full array, CS generates signal-to-interference ratio of 12 dB, but conventional beamforming only 8 dB. The superiority of CS over conventional beamforming is much more pronounced with undersampling.
Influence of the Saturation Ratio on Concrete Behavior under Triaxial Compressive Loading
Xuan-Dung Vu
2015-01-01
Full Text Available When a concrete structure is subjected to an impact, the material is subjected to high triaxial compressive stresses. Furthermore, the water saturation ratio in massive concrete structures may reach nearly 100% at the core, whereas the material dries quickly on the skin. The impact response of a massive concrete wall may thus depend on the state of water saturation in the material. This paper presents some triaxial tests performed at a maximum confining pressure of 600 MPa on concrete representative of a nuclear power plant containment building. Experimental results show the concrete constitutive behavior and its dependence on the water saturation ratio. It is observed that as the degree of saturation increases, a decrease in the volumetric strains as well as in the shear strength is observed. The coupled PRM constitutive model does not accurately reproduce the response of concrete specimens observed during the test. The differences between experimental and numerical results can be explained by both the influence of the saturation state of concrete and the effect of deviatoric stresses, which are not accurately taken into account. The PRM model was modified in order to improve the numerical prediction of concrete behavior under high stresses at various saturation states.
Objects of maximum electromagnetic chirality
Fernandez-Corbaton, Ivan
2015-01-01
We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. The upper bound is attained if and only if the object is transparent for fields of one handedness (helicity). Additionally, electromagnetic duality symmetry, i.e. helicity preservation upon scattering, turns out to be a necessary condition for reciprocal scatterers to attain the upper bound. We use these results to provide requirements for the design of such extremal scatterers. The requirements can be formulated as constraints on the polarizability tensors for dipolar scatterers or as material constitutive relations. We also outline two applications for objects of maximum electromagnetic chirality: A twofold resonantly enhanced and background free circular dichroism measurement setup, and angle independent helicity filtering glasses.
Maximum mutual information regularized classification
Wang, Jim Jing-Yan
2014-09-07
In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.
The strong maximum principle revisited
Pucci, Patrizia; Serrin, James
In this paper we first present the classical maximum principle due to E. Hopf, together with an extended commentary and discussion of Hopf's paper. We emphasize the comparison technique invented by Hopf to prove this principle, which has since become a main mathematical tool for the study of second order elliptic partial differential equations and has generated an enormous number of important applications. While Hopf's principle is generally understood to apply to linear equations, it is in fact also crucial in nonlinear theories, such as those under consideration here. In particular, we shall treat and discuss recent generalizations of the strong maximum principle, and also the compact support principle, for the case of singular quasilinear elliptic differential inequalities, under generally weak assumptions on the quasilinear operators and the nonlinearities involved. Our principal interest is in necessary and sufficient conditions for the validity of both principles; in exposing and simplifying earlier proofs of corresponding results; and in extending the conclusions to wider classes of singular operators than previously considered. The results have unexpected ramifications for other problems, as will develop from the exposition, e.g. two point boundary value problems for singular quasilinear ordinary differential equations (Sections 3 and 4); the exterior Dirichlet boundary value problem (Section 5); the existence of dead cores and compact support solutions, i.e. dead cores at infinity (Section 7); Euler-Lagrange inequalities on a Riemannian manifold (Section 9); comparison and uniqueness theorems for solutions of singular quasilinear differential inequalities (Section 10). The case of p-regular elliptic inequalities is briefly considered in Section 11.
Application of a continuum constitutive model to metallic foam DEN-specimens in compression
Onck, P.R.
2001-01-01
The behavior of double-edge notched specimens of metallic foams in compression is studied numerically. To model the constitutive behavior of the metallic foam, a recently developed phenomenological, pressure-sensitive yield surface is used. Compressive yielding in response to hydrostatic stress is i
Fatigue of concrete under compression: Database and proposal for high strength concrete
Lantsoght, E.O.L.
2014-01-01
The compressive strength of concrete decreases as an element is subjected to cycles of loading. In a typical fatigue test for the concrete compressive strength, a concrete specimen (typically a cylinder) is loaded between a lower and upper stress limit. These limits are expressed as a fraction of th
Fatigue of concrete under compression: Database and proposal for high strength concrete
Lantsoght, E.O.L.
2014-01-01
The compressive strength of concrete decreases as an element is subjected to cycles of loading. In a typical fatigue test for the concrete compressive strength, a concrete specimen (typically a cylinder) is loaded between a lower and upper stress limit. These limits are expressed as a fraction of
Reevaluation of the diametral compression test for tablets using the flattened disc geometry.
Mazel, V; Guerard, S; Croquelois, B; Kopp, J B; Girardot, J; Diarra, H; Busignies, V; Tchoreloff, P
2016-11-20
Mechanical strength is an important critical quality attribute for tablets. It is classically measured, in the pharmaceutical field, using the diametral compression test. Nevertheless, due to small contact area between the tablet and the platens, some authors suggested that during the test, the failure could occur in tension away from the center which would invalidate the test and the calculation of the tensile strength. In this study, the flattened disc geometry was used as an alternative to avoid contact problems. The diametral compression on both flattened and standard geometries was first studied using finite element method (FEM) simulation. It was found that, for the flattened geometry, both maximum tensile strain and stress were located at the center of the tablet, which was not the case for the standard geometry. Experimental observations using digital image correlation (DIC) confirmed the numerical results. The experimental tensile strength obtained using both geometries were compared and it was found that the standard geometry always gave lower tensile strength than the flattened geometry. Finally, high-speed video capture of the test made it possible to detect that for the standard geometry the crack initiation was always away from the center of the tablet. Copyright © 2016 Elsevier B.V. All rights reserved.
Compressive sensing in medical imaging.
Graff, Christian G; Sidky, Emil Y
2015-03-10
The promise of compressive sensing, exploitation of compressibility to achieve high quality image reconstructions with less data, has attracted a great deal of attention in the medical imaging community. At the Compressed Sensing Incubator meeting held in April 2014 at OSA Headquarters in Washington, DC, presentations were given summarizing some of the research efforts ongoing in compressive sensing for x-ray computed tomography and magnetic resonance imaging systems. This article provides an expanded version of these presentations. Sparsity-exploiting reconstruction algorithms that have gained popularity in the medical imaging community are studied, and examples of clinical applications that could benefit from compressive sensing ideas are provided. The current and potential future impact of compressive sensing on the medical imaging field is discussed.
Speech Compression Using Multecirculerletet Transform
Sulaiman Murtadha
2012-01-01
Full Text Available Compressing the speech reduces the data storage requirements, leading to reducing the time of transmitting the digitized speech over long-haul links like internet. To obtain best performance in speech compression, wavelet transforms require filters that combine a number of desirable properties, such as orthogonality and symmetry.The MCT bases functions are derived from GHM bases function using 2D linear convolution .The fast computation algorithm methods introduced here added desirable features to the current transform. We further assess the performance of the MCT in speech compression application. This paper discusses the effect of using DWT and MCT (one and two dimension on speech compression. DWT and MCT performances in terms of compression ratio (CR, mean square error (MSE and peak signal to noise ratio (PSNR are assessed. Computer simulation results indicate that the two dimensions MCT offer a better compression ratio, MSE and PSNR than DWT.
libpolycomp: Compression/decompression library
Tomasi, Maurizio
2016-04-01
Libpolycomp compresses and decompresses one-dimensional streams of numbers by means of several algorithms. It is well-suited for time-ordered data acquired by astronomical instruments or simulations. One of the algorithms, called "polynomial compression", combines two widely-used ideas (namely, polynomial approximation and filtering of Fourier series) to achieve substantial compression ratios for datasets characterized by smoothness and lack of noise. Notable examples are the ephemerides of astronomical objects and the pointing information of astronomical telescopes. Other algorithms implemented in this C library are well known and already widely used, e.g., RLE, quantization, deflate (via libz) and Burrows-Wheeler transform (via libbzip2). Libpolycomp can compress the timelines acquired by the Planck/LFI instrument with an overall compression ratio of ~9, while other widely known programs (gzip, bzip2) reach compression ratios less than 1.5.
Image Compression using GSOM Algorithm
SHABBIR AHMAD
2015-10-01
Full Text Available
Data compression on the sphere
McEwen, J D; Eyers, D M; 10.1051/0004-6361/201015728
2011-01-01
Large data-sets defined on the sphere arise in many fields. In particular, recent and forthcoming observations of the anisotropies of the cosmic microwave background (CMB) made on the celestial sphere contain approximately three and fifty mega-pixels respectively. The compression of such data is therefore becoming increasingly important. We develop algorithms to compress data defined on the sphere. A Haar wavelet transform on the sphere is used as an energy compression stage to reduce the entropy of the data, followed by Huffman and run-length encoding stages. Lossless and lossy compression algorithms are developed. We evaluate compression performance on simulated CMB data, Earth topography data and environmental illumination maps used in computer graphics. The CMB data can be compressed to approximately 40% of its original size for essentially no loss to the cosmological information content of the data, and to approximately 20% if a small cosmological information loss is tolerated. For the topographic and il...
Energy transfer in compressible turbulence
Bataille, Francoise; Zhou, YE; Bertoglio, Jean-Pierre
1995-01-01
This letter investigates the compressible energy transfer process. We extend a methodology developed originally for incompressible turbulence and use databases from numerical simulations of a weak compressible turbulence based on Eddy-Damped-Quasi-Normal-Markovian (EDQNM) closure. In order to analyze the compressible mode directly, the well known Helmholtz decomposition is used. While the compressible component has very little influence on the solenoidal part, we found that almost all of the compressible turbulence energy is received from its solenoidal counterpart. We focus on the most fundamental building block of the energy transfer process, the triadic interactions. This analysis leads us to conclude that, at low turbulent Mach number, the compressible energy transfer process is dominated by a local radiative transfer (absorption) in both inertial and energy containing ranges.
Perceptually Lossless Wavelet Compression
Watson, Andrew B.; Yang, Gloria Y.; Solomon, Joshua A.; Villasenor, John
1996-01-01
The Discrete Wavelet Transform (DWT) decomposes an image into bands that vary in spatial frequency and orientation. It is widely used for image compression. Measures of the visibility of DWT quantization errors are required to achieve optimal compression. Uniform quantization of a single band of coefficients results in an artifact that is the sum of a lattice of random amplitude basis functions of the corresponding DWT synthesis filter, which we call DWT uniform quantization noise. We measured visual detection thresholds for samples of DWT uniform quantization noise in Y, Cb, and Cr color channels. The spatial frequency of a wavelet is r 2(exp -1), where r is display visual resolution in pixels/degree, and L is the wavelet level. Amplitude thresholds increase rapidly with spatial frequency. Thresholds also increase from Y to Cr to Cb, and with orientation from low-pass to horizontal/vertical to diagonal. We propose a mathematical model for DWT noise detection thresholds that is a function of level, orientation, and display visual resolution. This allows calculation of a 'perceptually lossless' quantization matrix for which all errors are in theory below the visual threshold. The model may also be used as the basis for adaptive quantization schemes.
Compressive Sensing DNA Microarrays
Richard G. Baraniuk
2009-01-01
Full Text Available Compressive sensing microarrays (CSMs are DNA-based sensors that operate using group testing and compressive sensing (CS principles. In contrast to conventional DNA microarrays, in which each genetic sensor is designed to respond to a single target, in a CSM, each sensor responds to a set of targets. We study the problem of designing CSMs that simultaneously account for both the constraints from CS theory and the biochemistry of probe-target DNA hybridization. An appropriate cross-hybridization model is proposed for CSMs, and several methods are developed for probe design and CS signal recovery based on the new model. Lab experiments suggest that in order to achieve accurate hybridization profiling, consensus probe sequences are required to have sequence homology of at least 80% with all targets to be detected. Furthermore, out-of-equilibrium datasets are usually as accurate as those obtained from equilibrium conditions. Consequently, one can use CSMs in applications in which only short hybridization times are allowed.
Compressive light field sensing.
Babacan, S Derin; Ansorge, Reto; Luessi, Martin; Matarán, Pablo Ruiz; Molina, Rafael; Katsaggelos, Aggelos K
2012-12-01
We propose a novel design for light field image acquisition based on compressive sensing principles. By placing a randomly coded mask at the aperture of a camera, incoherent measurements of the light passing through different parts of the lens are encoded in the captured images. Each captured image is a random linear combination of different angular views of a scene. The encoded images are then used to recover the original light field image via a novel Bayesian reconstruction algorithm. Using the principles of compressive sensing, we show that light field images with a large number of angular views can be recovered from only a few acquisitions. Moreover, the proposed acquisition and recovery method provides light field images with high spatial resolution and signal-to-noise-ratio, and therefore is not affected by limitations common to existing light field camera designs. We present a prototype camera design based on the proposed framework by modifying a regular digital camera. Finally, we demonstrate the effectiveness of the proposed system using experimental results with both synthetic and real images.
S. Abhishek
2016-07-01
Full Text Available It is well understood that in any data acquisition system reduction in the amount of data reduces the time and energy, but the major trade-off here is the quality of outcome normally, lesser the amount of data sensed, lower the quality. Compressed Sensing (CS allows a solution, for sampling below the Nyquist rate. The challenging problem of increasing the reconstruction quality with less number of samples from an unprocessed data set is addressed here by the use of representative coordinate selected from different orders of splines. We have made a detailed comparison with 10 orthogonal and 6 biorthogonal wavelets with two sets of data from MIT Arrhythmia database and our results prove that the Spline coordinates work better than the wavelets. The generation of two new types of splines such as exponential and double exponential are also briefed here .We believe that this is one of the very first attempts made in Compressed Sensing based ECG reconstruction problems using raw data.
Characteristics and Causes of the Preconsolidation Stress of Soils in the Yellow River Delta
YANG Xiujuan; JIA Yonggang; LIU Hongjun; SHAN Hongxian
2009-01-01
Preconsolidation stress ( σ'P ) is the maximum effective stress that a soil has suffered throughout its life. From a geotechnical point of view, pre-consolidation stress has great importance because it separates elastic and reversible deformations from inelastic and only partially irreversible deformations and marks the starting point of high compressibility. In this study we calculated the preconsolidation stress for 72 undisturbed soil samples from the Yellow River Delta, using the oedometer test and applying the method proposed by Casagrande. The results showed that the over-consolidation ratio (OCR-the ratio of pre-consolidation stress to current natural overburden stress) values of the soil from soil surface to 6m depth varied from 1.72 to 15.34 and the maximum preconsolidation stress was above 200kPa. In consequence, the soils of the Yellow River Delta are highly over-consolidated within the upper 6m, the OCR decreasing gradually with depth from 6 to 12m. For samples from deeper than 12m the soils were found to be under-consolidated, which was proved by standard penetration tests (SPTs). The main causes of this type of consolidation are the mineral composition and the designability of the soil body.
CHEN Qing-fa; ZHOU Ke-ping; WANG Li-li
2010-01-01
For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1)the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2)the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually; however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3)the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m)in the scope of all filling height.
Mroueh, Youssef; Rosasco, Lorenzo
2013-01-01
We introduce q-ary compressive sensing, an extension of 1-bit compressive sensing. We propose a novel sensing mechanism and a corresponding recovery procedure. The recovery properties of the proposed approach are analyzed both theoretically and empirically. Results in 1-bit compressive sensing are recovered as a special case. Our theoretical results suggest a tradeoff between the quantization parameter q, and the number of measurements m in the control of the error of the resulting recovery a...
Introduction to compressible fluid flow
Oosthuizen, Patrick H
2013-01-01
IntroductionThe Equations of Steady One-Dimensional Compressible FlowSome Fundamental Aspects of Compressible FlowOne-Dimensional Isentropic FlowNormal Shock WavesOblique Shock WavesExpansion Waves - Prandtl-Meyer FlowVariable Area FlowsAdiabatic Flow with FrictionFlow with Heat TransferLinearized Analysis of Two-Dimensional Compressible FlowsHypersonic and High-Temperature FlowsHigh-Temperature Gas EffectsLow-Density FlowsBibliographyAppendices
PHYSICAL MODELING OF ODOMETRIC COMPRESSION OF SAND
Lyashenko P. A.
2016-10-01
Full Text Available The odometric compression of sand with constant rate of loading (CRL or constant rate of deformation (CRD and continuous registration of the corresponding reaction allows to identify the effect of stepwise changes of deformation (at the CRL and the power reaction (at the CRD. Physical modeling of compression on the sandy model showed the same effect. The physical model was made of fine sand with marks, mimicking large inclusions. Compression of the soil at the CRD was uneven, stepwise, and the strain rate of the upper boundary of the sandy model changed cyclically. Maximum amplitudes of cycles passed through a maximum. Inside of the sand model, the uneven strain resulted in the mutual displacement of the adjacent parts located at the same depth. The growth of external pressure, the marks showed an increase or decrease in displacement and even move opposite to the direction of movement (settlement the upper boundary of the model ‒ "floating" of marks. Marks, at different depths, got at the same time different movements, including mutually contradictory. The mark settlements sudden growth when the sufficiently large pressure. These increments in settlements remained until the end of loading decreasing with depth. They were a confirmation of the hypothesis about the total destruction of the soil sample at a pressure of "structural strength". The hypothesis of the "floating" reason based on the obvious assumption that the marks are moved together with the surrounding sand. The explanation of the effect of "floating" is supported by the fact that the value of "floating" the more, the greater the depth
Pedersen, Niels Leergaard
2013-01-01
The state of stress in bolts and nuts with ISO metric thread design is examined and optimized. The assumed failure mode is fatigue so the applied preload and the load amplitude together with the stress concentrations define the connection strength. Maximum stress in the bolt is found at, the fillet...... under the head, at the thread start or at the thread root. To minimize the stress concentration shape optimization is applied....
Pedersen, Niels Leergaard
2013-01-01
The state of stress in bolts and nuts with ISO metric thread design is examined and optimized. The assumed failure mode is fatigue so the applied preload and the load amplitude together with the stress concentrations define the connection strength. Maximum stress in the bolt is found at, the fillet...... under the head, at the thread start or at the thread root. To minimize the stress concentration shape optimization is applied....
Swan-like Memory Compressive Connector
Xu, Shuo-Gui; Zhang, Chun-Cai; Wu, Ya-Le; Fu, Qing-Ge
2011-02-01
Nonunion is a common complication after fractures of the diaphysis of the upper extremity. Conventional internal fixation cannot provide compressive stress at the fracture site, which is critical for fracture repair in nonweight-bearing bones. In order to overcome this problem, we developed a novel nitinol device that provides initial and continuous compression and three dimensional fixation, the swan-like memory compressive connector (SMC). A total of 188 cases (243 bones) of fractures and nonunions were treated by SMC over the course of 16 years. At follow-up, the nonunion sites were bridged by plate-like bone in 92 cases (106 bones) at an average of 3.8 months after surgery. In the fracture group, the fracture sites were bridged by plate-like bone in 93 cases (134 bones) at an average of 2.6 months after surgery. No infection or re-fracture occurred after removal of the SMC. There was no persistent joint dysfunction caused by the SMC.
Compressive sensing of sparse tensors.
Friedland, Shmuel; Li, Qun; Schonfeld, Dan
2014-10-01
Compressive sensing (CS) has triggered an enormous research activity since its first appearance. CS exploits the signal's sparsity or compressibility in a particular domain and integrates data compression and acquisition, thus allowing exact reconstruction through relatively few nonadaptive linear measurements. While conventional CS theory relies on data representation in the form of vectors, many data types in various applications, such as color imaging, video sequences, and multisensor networks, are intrinsically represented by higher order tensors. Application of CS to higher order data representation is typically performed by conversion of the data to very long vectors that must be measured using very large sampling matrices, thus imposing a huge computational and memory burden. In this paper, we propose generalized tensor compressive sensing (GTCS)-a unified framework for CS of higher order tensors, which preserves the intrinsic structure of tensor data with reduced computational complexity at reconstruction. GTCS offers an efficient means for representation of multidimensional data by providing simultaneous acquisition and compression from all tensor modes. In addition, we propound two reconstruction procedures, a serial method and a parallelizable method. We then compare the performance of the proposed method with Kronecker compressive sensing (KCS) and multiway compressive sensing (MWCS). We demonstrate experimentally that GTCS outperforms KCS and MWCS in terms of both reconstruction accuracy (within a range of compression ratios) and processing speed. The major disadvantage of our methods (and of MWCS as well) is that the compression ratios may be worse than that offered by KCS.
Uncommon upper extremity compression neuropathies.
Knutsen, Elisa J; Calfee, Ryan P
2013-08-01
Hand surgeons routinely treat carpal and cubital tunnel syndromes, which are the most common upper extremity nerve compression syndromes. However, more infrequent nerve compression syndromes of the upper extremity may be encountered. Because they are unusual, the diagnosis of these nerve compression syndromes is often missed or delayed. This article reviews the causes, proposed treatments, and surgical outcomes for syndromes involving compression of the posterior interosseous nerve, the superficial branch of the radial nerve, the ulnar nerve at the wrist, and the median nerve proximal to the wrist. Copyright © 2013 Elsevier Inc. All rights reserved.
Image Compression Algorithms Using Dct
Er. Abhishek Kaushik
2014-04-01
Full Text Available Image compression is the application of Data compression on digital images. The discrete cosine transform (DCT is a technique for converting a signal into elementary frequency components. It is widely used in image compression. Here we develop some simple functions to compute the DCT and to compress images. An image compression algorithm was comprehended using Matlab code, and modified to perform better when implemented in hardware description language. The IMAP block and IMAQ block of MATLAB was used to analyse and study the results of Image Compression using DCT and varying co-efficients for compression were developed to show the resulting image and error image from the original images. Image Compression is studied using 2-D discrete Cosine Transform. The original image is transformed in 8-by-8 blocks and then inverse transformed in 8-by-8 blocks to create the reconstructed image. The inverse DCT would be performed using the subset of DCT coefficients. The error image (the difference between the original and reconstructed image would be displayed. Error value for every image would be calculated over various values of DCT co-efficients as selected by the user and would be displayed in the end to detect the accuracy and compression in the resulting image and resulting performance parameter would be indicated in terms of MSE , i.e. Mean Square Error.
Maximum-entropy probability distributions under Lp-norm constraints
Dolinar, S.
1991-01-01
Continuous probability density functions and discrete probability mass functions are tabulated which maximize the differential entropy or absolute entropy, respectively, among all probability distributions with a given L sub p norm (i.e., a given pth absolute moment when p is a finite integer) and unconstrained or constrained value set. Expressions for the maximum entropy are evaluated as functions of the L sub p norm. The most interesting results are obtained and plotted for unconstrained (real valued) continuous random variables and for integer valued discrete random variables. The maximum entropy expressions are obtained in closed form for unconstrained continuous random variables, and in this case there is a simple straight line relationship between the maximum differential entropy and the logarithm of the L sub p norm. Corresponding expressions for arbitrary discrete and constrained continuous random variables are given parametrically; closed form expressions are available only for special cases. However, simpler alternative bounds on the maximum entropy of integer valued discrete random variables are obtained by applying the differential entropy results to continuous random variables which approximate the integer valued random variables in a natural manner. All the results are presented in an integrated framework that includes continuous and discrete random variables, constraints on the permissible value set, and all possible values of p. Understanding such as this is useful in evaluating the performance of data compression schemes.
Gray, G.T. III; Idar, D.J.; Blumenthal, W.R.; Cady, C.M.; Peterson, P.D.
1998-12-31
High- and low-strain rate compression data were obtained on several different energetic composites: PBX 9501, X0242-92-4-4, PBXN-9, as well as the polymeric binder used in PBX 9501 and X0242-92-4-4 composites. The effects of energetic-to-binder ratios, different binder systems, and different energetic formulations were investigated. All the energetic composites exhibit increasing elastic modulus, E, maximum flow stresses, {sigma}{sub m}, and strain-at-maximum stress, {var_epsilon}{sub m}, with increasing strain rate at ambient temperature. PBX 9501 displays marginally higher ultimate flow strength than X0242-92-4-4, and significantly higher ultimate compressive strength than PBXN-9 at quasi-static and dynamic strain rates. The failure mode of PBX 9501 and X0242-92-4-4 under high-rate loading changes from a mixture of ductile binder tearing and transgranular cleavage and cracking of the HMX when tested at 20 C to transgranular brittle HMX cleavage and glassy fracture of the binder at {minus}40 C.
Compression and texture in socks enhance football kicking performance.
Hasan, Hosni; Davids, Keith; Chow, Jia Yi; Kerr, Graham
2016-08-01
The purpose of this study was to observe effects of wearing textured insoles and clinical compression socks on organisation of lower limb interceptive actions in developing athletes of different skill levels in association football. Six advanced learners and six completely novice football players (15.4±0.9years) performed 20 instep kicks with maximum velocity, in four randomly organised insoles and socks conditions, (a) Smooth Socks with Smooth Insoles (SSSI); (b) Smooth Socks with Textured Insoles (SSTI); (c) Compression Socks with Smooth Insoles (CSSI) and (d), Compression Socks with Textured Insoles (CSTI). Reflective markers were placed on key anatomical locations and the ball to facilitate three-dimensional (3D) movement recording and analysis. Data on 3D kinematic variables and initial ball velocity were analysed using one-way mixed model ANOVAs. Results revealed that wearing textured and compression materials enhanced performance in key variables, such as the maximum velocity of the instep kick and increased initial ball velocity, among advanced learners compared to the use of non-textured and compression materials. Adding texture to football boot insoles appeared to interact with compression materials to improve kicking performance, captured by these important measures. This improvement in kicking performance is likely to have occurred through enhanced somatosensory system feedback utilised for foot placement and movement organisation of the lower limbs. Data suggested that advanced learners were better at harnessing the augmented feedback information from compression and texture to regulate emerging movement patterns compared to novices. Copyright © 2016. Published by Elsevier B.V.
Luo, Ying; Wang, Yancheng; Tai, Bruce L; Chen, Roland K; Shih, Albert J
2015-02-01
This research presents the finite element modeling (FEM) of human-specific computed tomography (CT) data to study the effect of bone prominences on contact stress in the shoulder for prevention of pressure ulcers. The 3D geometry of scapula, skin, and surrounding soft tissues in the shoulder was reconstructed based on the anonymous CT data of a human subject in a prone posture (without loading on the shoulder) for FEM analysis of the contact stress. FEM analysis results show that the maximum stress is located at the prominence of the scapula with sharp bone geometry. This demonstrates that stress concentration at the bone prominence is a significant factor to cause the high contact stress, which is a source for pressure ulcers. For experimental validation, a physical shoulder model manufactured by 3D printing of the bone geometry and the mold for molding of tissue-mimicking silicone was developed. Compression tests of the mattress foam and silicone were conducted to find the nonlinear stress-strain relations as inputs for FEM. Experiments of compressing the shoulder model against the foam were carried out. Three flexible force sensors were embedded inside the model to measure the contact forces and compared to the FEM predictions. Results show that the FEM predicted forces match well with the experimental measurements and demonstrate that FEM can accurately predict the stress distributions in the shoulder to study the effect of bone geometry on the inception of pressure ulcers.
Maximum entropy production in daisyworld
Maunu, Haley A.; Knuth, Kevin H.
2012-05-01
Daisyworld was first introduced in 1983 by Watson and Lovelock as a model that illustrates how life can influence a planet's climate. These models typically involve modeling a planetary surface on which black and white daisies can grow thus influencing the local surface albedo and therefore also the temperature distribution. Since then, variations of daisyworld have been applied to study problems ranging from ecological systems to global climate. Much of the interest in daisyworld models is due to the fact that they enable one to study self-regulating systems. These models are nonlinear, and as such they exhibit sensitive dependence on initial conditions, and depending on the specifics of the model they can also exhibit feedback loops, oscillations, and chaotic behavior. Many daisyworld models are thermodynamic in nature in that they rely on heat flux and temperature gradients. However, what is not well-known is whether, or even why, a daisyworld model might settle into a maximum entropy production (MEP) state. With the aim to better understand these systems, this paper will discuss what is known about the role of MEP in daisyworld models.
Maximum Matchings via Glauber Dynamics
Jindal, Anant; Pal, Manjish
2011-01-01
In this paper we study the classic problem of computing a maximum cardinality matching in general graphs $G = (V, E)$. The best known algorithm for this problem till date runs in $O(m \\sqrt{n})$ time due to Micali and Vazirani \\cite{MV80}. Even for general bipartite graphs this is the best known running time (the algorithm of Karp and Hopcroft \\cite{HK73} also achieves this bound). For regular bipartite graphs one can achieve an $O(m)$ time algorithm which, following a series of papers, has been recently improved to $O(n \\log n)$ by Goel, Kapralov and Khanna (STOC 2010) \\cite{GKK10}. In this paper we present a randomized algorithm based on the Markov Chain Monte Carlo paradigm which runs in $O(m \\log^2 n)$ time, thereby obtaining a significant improvement over \\cite{MV80}. We use a Markov chain similar to the \\emph{hard-core model} for Glauber Dynamics with \\emph{fugacity} parameter $\\lambda$, which is used to sample independent sets in a graph from the Gibbs Distribution \\cite{V99}, to design a faster algori...
Shock wave compression behavior of aluminum foam
程和法; 黄笑梅; 薛国宪; 韩福生
2003-01-01
The shock wave compression behavior of the open cell aluminum foam with relative density of 0. 396 was studied through planar impact experiments. Using polyvinylidene fluoride(PVDF) piezoelectric gauge technique, the stress histories and propagation velocities of shock wave in the aluminum foam were measured and analyzed. The results show that the amplitude of shock wave attenuates rapidly with increasing the propagation distance in the aluminum foam, and an exponential equation of the normalized peak stress vs propagation distance of shock wave is established, the attenuation factor in the equation is 0. 286. Furthermore, the Hugoniot relation, νs = 516.85+ 1.27νp,for the aluminum foam is determined by empirical fit to the experimental Hugoniot data.
2011-01-10
...: Establishing Maximum Allowable Operating Pressure or Maximum Operating Pressure Using Record Evidence, and... facilities of their responsibilities, under Federal integrity management (IM) regulations, to perform... system, especially when calculating Maximum Allowable Operating Pressure (MAOP) or Maximum Operating...
Axial Compressive Strength of Foamcrete with Different Profiles and Dimensions
Othuman Mydin M.A.
2014-01-01
Full Text Available Lightweight foamcrete is a versatile material; primarily consist of a cement based mortar mixed with at least 20% volume of air. High flow ability, lower self-weight, minimal requirement of aggregate, controlled low strength and good thermal insulation properties are a few characteristics of foamcrete. Its dry densities, typically, is below 1600kg/m3 with compressive strengths maximum of 15MPa. The ASTM standard provision specifies a correction factor for concrete strengths of between 14 and 42MPa to compensate for the reduced strength when the aspect height-to-diameter ratio of specimen is less than 2.0, while the CEB-FIP provision specifically mentions the ratio of 150 x 300mm cylinder strength to 150 mm cube strength. However, both provisions requirements do not specifically clarify the applicability and/or modification of the correction factors for the compressive strength of foamcrete. This proposed laboratory work is intended to study the effect of different dimensions and profiles on the axial compressive strength of concrete. Specimens of various dimensions and profiles are cast with square and circular cross-sections i.e., cubes, prisms and cylinders, and to investigate their behavior in compression strength at 7 and 28 days. Hypothetically, compressive strength will decrease with the increase of concrete specimen dimension and concrete specimen with cube profile would yield comparable compressive strength to cylinder (100 x 100 x 100mm cube to 100dia x 200mm cylinder.
Compressive sensing by learning a Gaussian mixture model from measurements.
Yang, Jianbo; Liao, Xuejun; Yuan, Xin; Llull, Patrick; Brady, David J; Sapiro, Guillermo; Carin, Lawrence
2015-01-01
Compressive sensing of signals drawn from a Gaussian mixture model (GMM) admits closed-form minimum mean squared error reconstruction from incomplete linear measurements. An accurate GMM signal model is usually not available a priori, because it is difficult to obtain training signals that match the statistics of the signals being sensed. We propose to solve that problem by learning the signal model in situ, based directly on the compressive measurements of the signals, without resorting to other signals to train a model. A key feature of our method is that the signals being sensed are treated as random variables and are integrated out in the likelihood. We derive a maximum marginal likelihood estimator (MMLE) that maximizes the likelihood of the GMM of the underlying signals given only their linear compressive measurements. We extend the MMLE to a GMM with dominantly low-rank covariance matrices, to gain computational speedup. We report extensive experimental results on image inpainting, compressive sensing of high-speed video, and compressive hyperspectral imaging (the latter two based on real compressive cameras). The results demonstrate that the proposed methods outperform state-of-the-art methods by significant margins.
Conceptual design of heavy ion beam compression using a wedge
Jonathan C. Wong
2015-10-01
Full Text Available Heavy ion beams are a useful tool for conducting high energy density physics (HEDP experiments. Target heating can be enhanced by beam compression, because a shorter pulse diminishes hydrodynamic expansion during irradiation. A conceptual design is introduced to compress ∼100 MeV/u to ∼GeV/u heavy ion beams using a wedge. By deflecting the beam with a time-varying field and placing a tailor-made wedge amid its path downstream, each transverse slice passes through matter of different thickness. The resulting energy loss creates a head-to-tail velocity gradient, and the wedge shape can be designed by using stopping power models to give maximum compression at the target. The compression ratio at the target was found to vary linearly with (head-to-tail centroid offset/spot radius at the wedge. The latter should be approximately 10 to attain tenfold compression. The decline in beam quality due to projectile ionization, energy straggling, fragmentation, and scattering is shown to be acceptable for well-chosen wedge materials. A test experiment is proposed to verify the compression scheme and to study the beam-wedge interaction and its associated beam dynamics, which will facilitate further efforts towards a HEDP facility.
Kim, M. C.; Cho, H.; Son, M.
2014-12-01
To determine current regional stress field and to characterize the resultant crustal deformation in SE Korea, Quaternary fault, focal mechanism, and geotechnical in-situ stress data were synthetically analyzed. The Quaternary faults are extensively observed along major inherited fault zones and show compatible orientations with general trends of the inherited faults. Most of the Quaternary faults have a top-to-the-west thrust geometry and kinematics and show a tendency of upward-decreasing dip angle and upward-narrowing gouge zone. Slip-sense indicators and paleo-stress field reconstructions indicate that the faults resulted from reverse or transpressional faulting under an E-W compression. All the magnetic fabrics (AMS) of the fault gouges also indicate the prevailing reverse-slip faulting under an ENE-WNW compression. The dominant oblate magnetic fabrics parallel to fault plane and the degrees of anisotropy increasing in proportion to their oblatenesses indicate that the fabrics have formed by a progressive deformation due to continuous simple shear during the last reactivation stage as reverse faulting. The focal mechanism study in and around the Korean Peninsula show the horizontally clustered P-axes in ENE-WSW direction and the girdle-distributed T-axes in NNW trend. The geotechnical in-situ stress data in south Korea also show NE- or ENE-trending maximum horizontal stress. The current crustal deformation in Korea thus can be characterized by contractional structures produced under a regional E-W or ENE-WSW compression stress field, and most of the Quaternary faults resulted from the local re-activation of appropriately oriented inherited major faults. Considering the tectonic setting and structural features in Asia during the Neogene, the current stress regime is interpreted to have been caused by the cooperation of westward shallow subduction of Pacific Plate and collision of Indian and Eurasian continents since about 5-3.5 Ma.
A maximum in the strength of nanocrystalline copper
Schiøtz, Jakob; Jacobsen, Karsten Wedel
2003-01-01
We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15...... nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-mediated plasticity in the coarse-grained material to grain boundary sliding in the nanocrystalline region. The simulations allow us to observe the mechanisms behind the grain-size dependence...
CASMI—A visualization tool for the World Stress Map database
Heidbach, Oliver; Höhne, Jens
2008-07-01
The World Stress Map (WSM) project has compiled a global database of quality-ranked data records on the contemporary tectonic stresses in the Earth's crust. The WSM 2005 database release contains approximately 16 000 data records from different types of stress indicators such as earthquake focal mechanisms solutions, well bore breakouts, hydraulic fracturing and overcoring measurements, as well as quaternary fault-slip data and volcanic alignments. To provide a software tool for database visualization, analysis and interpretation of stress data as well its integration with other data records, we developed the program CASMI. This public domain software tool for Unix-like operating systems enables the selection of stress data records from the WSM database according to location, data quality, type of stress indicator, and depth. Each selected data record is visualized by a symbol that represents the type of stress indicator and the orientation of the maximum horizontal compressive stress. Symbol size is proportional to the quality of the data record, and the colour indicates different tectonic regimes. Stress maps can be produced in different geographical projections and high-quality output formats. CASMI also allows the integration of user-defined stress data sets and a wide range of other data such as topography, Harvard centroid moment tensors, polygons, text data, and plate motion trajectories. CASMI, including the WSM 2005 database release, can be requested free of charge from the project's website at http://www.world-stress-map.org/casmi. We present two stress map examples generated with CASMI ranging from plate-wide to regional scale: (1) A stress map of central Europe, that reveals the correlation of stress field orientation and relative plate motion. (2) The fan-shape stress pattern in North Germany.
An underwater acoustic data compression method based on compressed sensing
郭晓乐; 杨坤德; 史阳; 段睿
2016-01-01
The use of underwater acoustic data has rapidly expanded with the application of multichannel, large-aperture underwater detection arrays. This study presents an underwater acoustic data compression method that is based on compressed sensing. Underwater acoustic signals are transformed into the sparse domain for data storage at a receiving terminal, and the improved orthogonal matching pursuit (IOMP) algorithm is used to reconstruct the original underwater acoustic signals at a data processing terminal. When an increase in sidelobe level occasionally causes a direction of arrival estimation error, the proposed compression method can achieve a 10 times stronger compression for narrowband signals and a 5 times stronger compression for wideband signals than the orthogonal matching pursuit (OMP) algorithm. The IOMP algorithm also reduces the computing time by about 20% more than the original OMP algorithm. The simulation and experimental results are discussed.
Berger, Jens; Frankenfeld, Ulrich; Lindenstruth, Volker; Plamper, Patrick; Roehrich, Dieter; Schaefer, Erich; W. Schulz, Markus; M. Steinbeck, Timm; Stock, Reinhard; Sulimma, Kolja; Vestboe, Anders; Wiebalck, Arne E-mail: wiebalck@kip.uni-heidelberg.de
2002-08-21
In the collisions of ultra-relativistic heavy ions in fixed-target and collider experiments, multiplicities of several ten thousand charged particles are generated. The main devices for tracking and particle identification are large-volume tracking detectors (TPCs) producing raw event sizes in excess of 100 Mbytes per event. With increasing data rates, storage becomes the main limiting factor in such experiments and, therefore, it is essential to represent the data in a way that is as concise as possible. In this paper, we present several compression schemes, such as entropy encoding, modified vector quantization, and data modeling techniques applied on real data from the CERN SPS experiment NA49 and on simulated data from the future CERN LHC experiment ALICE.
Berger, Jens; Lindenstruth, Volker; Plamper, Patrick; Röhrich, Dieter; Schafer, Erich; Schulz, M W; Steinbeck, T M; Stock, Reinhard; Sulimma, Kolja; Vestbo, Anders S; Wiebalck, Arne
2002-01-01
In the collisions of ultra-relativistic heavy ions in fixed-target and collider experiments, multiplicities of several ten thousand charged particles are generated. The main devices for tracking and particle identification are large-volume tracking detectors (TPCs) producing raw event sizes in excess of 100 Mbytes per event. With increasing data rates, storage becomes the main limiting factor in such experiments and, therefore, it is essential to represent the data in a way that is as concise as possible. In this paper, we present several compression schemes, such as entropy encoding, modified vector quantization, and data modeling techniques applied on real data from the CERN SPS experiment NA49 and on simulated data from the future CERN LHC experiment ALICE.
Berger, Jens; Frankenfeld, Ulrich; Lindenstruth, Volker; Plamper, Patrick; Röhrich, Dieter; Schäfer, Erich; Schulz, Markus W.; Steinbeck, Timm M.; Stock, Reinhard; Sulimma, Kolja; Vestbø, Anders; Wiebalck, Arne
2002-08-01
In the collisions of ultra-relativistic heavy ions in fixed-target and collider experiments, multiplicities of several ten thousand charged particles are generated. The main devices for tracking and particle identification are large-volume tracking detectors (TPCs) producing raw event sizes in excess of 100 Mbytes per event. With increasing data rates, storage becomes the main limiting factor in such experiments and, therefore, it is essential to represent the data in a way that is as concise as possible. In this paper, we present several compression schemes, such as entropy encoding, modified vector quantization, and data modeling techniques applied on real data from the CERN SPS experiment NA49 and on simulated data from the future CERN LHC experiment ALICE.
Ockendon, Hilary
2016-01-01
Now in its second edition, this book continues to give readers a broad mathematical basis for modelling and understanding the wide range of wave phenomena encountered in modern applications. New and expanded material includes topics such as elastoplastic waves and waves in plasmas, as well as new exercises. Comprehensive collections of models are used to illustrate the underpinning mathematical methodologies, which include the basic ideas of the relevant partial differential equations, characteristics, ray theory, asymptotic analysis, dispersion, shock waves, and weak solutions. Although the main focus is on compressible fluid flow, the authors show how intimately gasdynamic waves are related to wave phenomena in many other areas of physical science. Special emphasis is placed on the development of physical intuition to supplement and reinforce analytical thinking. Each chapter includes a complete set of carefully prepared exercises, making this a suitable textbook for students in applied mathematics, ...
Central cooling: compressive chillers
Christian, J.E.
1978-03-01
Representative cost and performance data are provided in a concise, useable form for three types of compressive liquid packaged chillers: reciprocating, centrifugal, and screw. The data are represented in graphical form as well as in empirical equations. Reciprocating chillers are available from 2.5 to 240 tons with full-load COPs ranging from 2.85 to 3.87. Centrifugal chillers are available from 80 to 2,000 tons with full load COPs ranging from 4.1 to 4.9. Field-assemblied centrifugal chillers have been installed with capacities up to 10,000 tons. Screw-type chillers are available from 100 to 750 tons with full load COPs ranging from 3.3 to 4.5.
Vitanyi, Paul M B
2011-01-01
First we consider pair-wise distances for literal objects consisting of finite binary files. These files are taken to contain all of their meaning, like genomes or books. The distances are based on compression of the objects concerned, normalized, and can be viewed as similarity distances. Second, we consider pair-wise distances between names of objects, like "red" or "christianity." In this case the distances are based on searches of the Internet. Such a search can be performed by any search engine that returns aggregate page counts. We can extract a code length from the numbers returned, use the same formula as before, and derive a similarity or relative semantics between names for objects. The theory is based on Kolmogorov complexity. We test both similarities extensively experimentally.
Adaptively Compressed Exchange Operator
Lin, Lin
2016-01-01
The Fock exchange operator plays a central role in modern quantum chemistry. The large computational cost associated with the Fock exchange operator hinders Hartree-Fock calculations and Kohn-Sham density functional theory calculations with hybrid exchange-correlation functionals, even for systems consisting of hundreds of atoms. We develop the adaptively compressed exchange operator (ACE) formulation, which greatly reduces the computational cost associated with the Fock exchange operator without loss of accuracy. The ACE formulation does not depend on the size of the band gap, and thus can be applied to insulating, semiconducting as well as metallic systems. In an iterative framework for solving Hartree-Fock-like systems, the ACE formulation only requires moderate modification of the code, and can be potentially beneficial for all electronic structure software packages involving exchange calculations. Numerical results indicate that the ACE formulation can become advantageous even for small systems with tens...
Stress corrosion cracking of brass in ammonia solution
无
2001-01-01
Brass foil with a protective layer formed on one side was deflected during corrosion in an ammonia solution under various applied potentials, and then corrosion-induced stress generated at brass/dezincification layer under different potentials could be measured. At the same time, susceptibility to stress corrosion cracking(SCC) of brass in the ammonia solution under various applied potentials was measured using a single-edge notched specimen. At open-circuit potential, both corrosion-induced tensile stress and susceptibility to SCC(Iσ) had a maximum value. Both tensile stress σp and susceptibility Iσ decreased slightly under anodic polarization, but reduced steeply with the decrease in potential of cathodic polarization. At the cathodic potential of -500 mV(vs SCE), corrosion-induced stress became compressive because of copper-plating layer, correspondingly, susceptibility to SCC was zero. Therefore, the variation of SCC susceptibility with potential is consistent with that of the corrosion-induced additive stress.
The Sherpa Maximum Likelihood Estimator
Nguyen, D.; Doe, S.; Evans, I.; Hain, R.; Primini, F.
2011-07-01
A primary goal for the second release of the Chandra Source Catalog (CSC) is to include X-ray sources with as few as 5 photon counts detected in stacked observations of the same field, while maintaining acceptable detection efficiency and false source rates. Aggressive source detection methods will result in detection of many false positive source candidates. Candidate detections will then be sent to a new tool, the Maximum Likelihood Estimator (MLE), to evaluate the likelihood that a detection is a real source. MLE uses the Sherpa modeling and fitting engine to fit a model of a background and source to multiple overlapping candidate source regions. A background model is calculated by simultaneously fitting the observed photon flux in multiple background regions. This model is used to determine the quality of the fit statistic for a background-only hypothesis in the potential source region. The statistic for a background-plus-source hypothesis is calculated by adding a Gaussian source model convolved with the appropriate Chandra point spread function (PSF) and simultaneously fitting the observed photon flux in each observation in the stack. Since a candidate source may be located anywhere in the field of view of each stacked observation, a different PSF must be used for each observation because of the strong spatial dependence of the Chandra PSF. The likelihood of a valid source being detected is a function of the two statistics (for background alone, and for background-plus-source). The MLE tool is an extensible Python module with potential for use by the general Chandra user.
Vestige: Maximum likelihood phylogenetic footprinting
Maxwell Peter
2005-05-01
Full Text Available Abstract Background Phylogenetic footprinting is the identification of functional regions of DNA by their evolutionary conservation. This is achieved by comparing orthologous regions from multiple species and identifying the DNA regions that have diverged less than neutral DNA. Vestige is a phylogenetic footprinting package built on the PyEvolve toolkit that uses probabilistic molecular evolutionary modelling to represent aspects of sequence evolution, including the conventional divergence measure employed by other footprinting approaches. In addition to measuring the divergence, Vestige allows the expansion of the definition of a phylogenetic footprint to include variation in the distribution of any molecular evolutionary processes. This is achieved by displaying the distribution of model parameters that represent partitions of molecular evolutionary substitutions. Examination of the spatial incidence of these effects across regions of the genome can identify DNA segments that differ in the nature of the evolutionary process. Results Vestige was applied to a reference dataset of the SCL locus from four species and provided clear identification of the known conserved regions in this dataset. To demonstrate the flexibility to use diverse models of molecular evolution and dissect the nature of the evolutionary process Vestige was used to footprint the Ka/Ks ratio in primate BRCA1 with a codon model of evolution. Two regions of putative adaptive evolution were identified illustrating the ability of Vestige to represent the spatial distribution of distinct molecular evolutionary processes. Conclusion Vestige provides a flexible, open platform for phylogenetic footprinting. Underpinned by the PyEvolve toolkit, Vestige provides a framework for visualising the signatures of evolutionary processes across the genome of numerous organisms simultaneously. By exploiting the maximum-likelihood statistical framework, the complex interplay between mutational
Adaptive compressive sensing camera
Hsu, Charles; Hsu, Ming K.; Cha, Jae; Iwamura, Tomo; Landa, Joseph; Nguyen, Charles; Szu, Harold
2013-05-01
We have embedded Adaptive Compressive Sensing (ACS) algorithm on Charge-Coupled-Device (CCD) camera based on the simplest concept that each pixel is a charge bucket, and the charges comes from Einstein photoelectric conversion effect. Applying the manufactory design principle, we only allow altering each working component at a minimum one step. We then simulated what would be such a camera can do for real world persistent surveillance taking into account of diurnal, all weather, and seasonal variations. The data storage has saved immensely, and the order of magnitude of saving is inversely proportional to target angular speed. We did design two new components of CCD camera. Due to the matured CMOS (Complementary metal-oxide-semiconductor) technology, the on-chip Sample and Hold (SAH) circuitry can be designed for a dual Photon Detector (PD) analog circuitry for changedetection that predicts skipping or going forward at a sufficient sampling frame rate. For an admitted frame, there is a purely random sparse matrix [Φ] which is implemented at each bucket pixel level the charge transport bias voltage toward its neighborhood buckets or not, and if not, it goes to the ground drainage. Since the snapshot image is not a video, we could not apply the usual MPEG video compression and Hoffman entropy codec as well as powerful WaveNet Wrapper on sensor level. We shall compare (i) Pre-Processing FFT and a threshold of significant Fourier mode components and inverse FFT to check PSNR; (ii) Post-Processing image recovery will be selectively done by CDT&D adaptive version of linear programming at L1 minimization and L2 similarity. For (ii) we need to determine in new frames selection by SAH circuitry (i) the degree of information (d.o.i) K(t) dictates the purely random linear sparse combination of measurement data a la [Φ]M,N M(t) = K(t) Log N(t).
Phase Diagrams of Instabilities in Compressed Film-Substrate Systems.
Wang, Qiming; Zhao, Xuanhe
2014-05-01
Subject to a compressive membrane stress, an elastic film bonded on a substrate can become unstable, forming wrinkles, creases or delaminated buckles. Further increasing the compressive stress can induce advanced modes of instabilities including period-doubles, folds, localized ridges, delamination, and coexistent instabilities. While various instabilities in film-substrate systems under compression have been analyzed separately, a systematic and quantitative understanding of these instabilities is still elusive. Here we present a joint experimental and theoretical study to systematically explore the instabilities in elastic film-substrate systems under uniaxial compression. We use the Maxwell stability criterion to analyze the occurrence and evolution of instabilities analogous to phase transitions in thermodynamic systems. We show that the moduli of the film and the substrate, the film-substrate adhesion strength, the film thickness, and the prestretch in the substrate determine various modes of instabilities. Defects in the film-substrate system can facilitate it to overcome energy barriers during occurrence and evolution of instabilities. We provide a set of phase diagrams to predict both initial and advanced modes of instabilities in compressed film-substrate systems. The phase diagrams can be used to guide the design of film-substrate systems to achieve desired modes of instabilities.
Kong, Biao; Wang, Enyuan; Li, Zenghua; Wang, Xiaoran; Niu, Yue; Kong, Xiangguo
2017-01-01
Thermally treated sandstone deformation and fracture produced abundant acoustic emission (AE) signals. The AE signals waveform contained plentiful precursor information of sandstone deformation and fracture behavior. In this paper, uniaxial compression tests of sandstone after different temperature treatments were conducted, the frequency-amplitude characteristics of AE signals were studied, and the main frequency distribution at different stress level was analyzed. The AE signals frequency-amplitude characteristics had great difference after different high temperature treatment. Significant differences existed of the main frequency distribution of AE signals during thermal treated sandstone deformation and fracture. The main frequency band of the largest waveforms proportion was not unchanged after different high temperature treatments. High temperature caused thermal damage to the sandstone, and sandstone deformation and fracture was obvious than the room temperature. The number of AE signals was larger than the room temperature during the initial loading stage. The low frequency AE signals had bigger proportion when the stress was 0.1, and the maximum value of the low frequency amplitude was larger than high frequency signals. With the increase of stress, the low and high frequency AE signals were gradually increase, which indicated that different scales ruptures were broken in sandstone. After high temperature treatment, the number of high frequency AE signals was significantly bigger than the low frequency AE signals during the latter loading stage, this indicates that the small scale rupture rate of recurrence and frequency were more than large scale rupture. The AE ratio reached the maximum during the sandstone instability failure period, and large scale rupture was dominated in the failure process. AE amplitude increase as the loading increases, the deformation and fracture of sandstone was increased gradually. By comparison, the value of the low frequency
Yu. L. Rebetsky
2015-09-01
Full Text Available The article presents results of tectonophysical methods applied to reconstruct tectonic stress field of the north-western flank of the Pacific Ocean seismic focal zone in the region wherein the 2011 Tohoku earthquake was prepared. The reconstructions are based on earthquake foci data for the time period before the catastrophic seismic event. The field of stresses, wherein the Tohoku earthquake focus was formed, had a high gradient along the dip of the seismic focal zone. It is revealed that the focus developed in the junction area of the crust segments with high and low levels of effective pressure. A wide area of lower effective pressure was located at depths close to 30 km, and it was the most susceptible to brittle fracture. In our opinion, the area impacted by the Tohoku earthquake is large due to a large length of the crustal segments with the high gradient of stresses, which are located along the eastern part of the crust of the Honshu Island.The stress reconstruction also shows that the axis of the Japan oceanic trough divides the seismic focal zone into areas of horizontal compression (westward and horizontal extension (eastwards. According to our calculations, lateral compression is the highest at the crustal depths up to 20 km westward of the trough’s axis, where maximum lateral compression axes are oriented orthogonally to the trough’s strike. Eastward of the trough’s axis, minimum horizontal compression axes are oriented orthogonally to the trough’s strike. At the crossing point of the Japan trough, a sharp changing of stress is by a factor of 5 to 8 of internal cohesion of rocks, τf. This sharp changing of stress is lower for the Izu-Bonin trough and varies from 3 to 5 τf.
Application specific compression : final report.
Melgaard, David Kennett; Byrne, Raymond Harry; Myers, Daniel S.; Harrison, Carol D.; Lee, David S.; Lewis, Phillip J.; Carlson, Jeffrey J.
2008-12-01
With the continuing development of more capable data gathering sensors, comes an increased demand on the bandwidth for transmitting larger quantities of data. To help counteract that trend, a study was undertaken to determine appropriate lossy data compression strategies for minimizing their impact on target detection and characterization. The survey of current compression techniques led us to the conclusion that wavelet compression was well suited for this purpose. Wavelet analysis essentially applies a low-pass and high-pass filter to the data, converting the data into the related coefficients that maintain spatial information as well as frequency information. Wavelet compression is achieved by zeroing the coefficients that pertain to the noise in the signal, i.e. the high frequency, low amplitude portion. This approach is well suited for our goal because it reduces the noise in the signal with only minimal impact on the larger, lower frequency target signatures. The resulting coefficients can then be encoded using lossless techniques with higher compression levels because of the lower entropy and significant number of zeros. No significant signal degradation or difficulties in target characterization or detection were observed or measured when wavelet compression was applied to simulated and real data, even when over 80% of the coefficients were zeroed. While the exact level of compression will be data set dependent, for the data sets we studied, compression factors over 10 were found to be satisfactory where conventional lossless techniques achieved levels of less than 3.
Streaming Compression of Hexahedral Meshes
Isenburg, M; Courbet, C
2010-02-03
We describe a method for streaming compression of hexahedral meshes. Given an interleaved stream of vertices and hexahedral our coder incrementally compresses the mesh in the presented order. Our coder is extremely memory efficient when the input stream documents when vertices are referenced for the last time (i.e. when it contains topological finalization tags). Our coder then continuously releases and reuses data structures that no longer contribute to compressing the remainder of the stream. This means in practice that our coder has only a small fraction of the whole mesh in memory at any time. We can therefore compress very large meshes - even meshes that do not file in memory. Compared to traditional, non-streaming approaches that load the entire mesh and globally reorder it during compression, our algorithm trades a less compact compressed representation for significant gains in speed, memory, and I/O efficiency. For example, on the 456k hexahedra 'blade' mesh, our coder is twice as fast and uses 88 times less memory (only 3.1 MB) with the compressed file increasing about 3% in size. We also present the first scheme for predictive compression of properties associated with hexahedral cells.
Data Compression with Linear Algebra
Etler, David
2015-01-01
A presentation on the applications of linear algebra to image compression. Covers entropy, the discrete cosine transform, thresholding, quantization, and examples of images compressed with DCT. Given in Spring 2015 at Ocean County College as part of the honors program.
Compressed sensing for body MRI.
Feng, Li; Benkert, Thomas; Block, Kai Tobias; Sodickson, Daniel K; Otazo, Ricardo; Chandarana, Hersh
2017-04-01
The introduction of compressed sensing for increasing imaging speed in magnetic resonance imaging (MRI) has raised significant interest among researchers and clinicians, and has initiated a large body of research across multiple clinical applications over the last decade. Compressed sensing aims to reconstruct unaliased images from fewer measurements than are traditionally required in MRI by exploiting image compressibility or sparsity. Moreover, appropriate combinations of compressed sensing with previously introduced fast imaging approaches, such as parallel imaging, have demonstrated further improved performance. The advent of compressed sensing marks the prelude to a new era of rapid MRI, where the focus of data acquisition has changed from sampling based on the nominal number of voxels and/or frames to sampling based on the desired information content. This article presents a brief overview of the application of compressed sensing techniques in body MRI, where imaging speed is crucial due to the presence of respiratory motion along with stringent constraints on spatial and temporal resolution. The first section provides an overview of the basic compressed sensing methodology, including the notion of sparsity, incoherence, and nonlinear reconstruction. The second section reviews state-of-the-art compressed sensing techniques that have been demonstrated for various clinical body MRI applications. In the final section, the article discusses current challenges and future opportunities. 5 J. Magn. Reson. Imaging 2017;45:966-987. © 2016 International Society for Magnetic Resonance in Medicine.
Isentropic compression studies using the NHMFL single turn
Tasker, Douglas G [Los Alamos National Laboratory; Mielke, Charles [Los Alamos National Laboratory; Rodriguez, George [Los Alamos National Laboratory; Rickel, Dwight [Los Alamos National Laboratory
2010-10-19
Magnetic isentropic compression experiments (ICE) provide the most accurate shock free compression data for materials at megabar stresses. Recent ICE experiments performed on the Sandia Z-machine (Asay, 1999) and at the Los Alamos High Explosive Pulsed Power facility (Tasker, 2006) are providing our nation with data on material properties in extreme dynamic high stress environments. The LANL National High Magnetic Field Laboratory (NHMFL) can offer a less complex ICE experiment at high stresses (up to {approx}1Mbar) with a high sample throughput and relatively low cost. This is not to say that the NHMFL technique will replace the other methods but rather complement them. For example, NHMFL-ICE is ideal for the development of advanced diagnostics, e.g., to detect phase changes. We will discuss the physics of the NHMFL-ICE experiments and present data from the first proof-of-principle experiments that were performed in September 2010.
RESULTS OF COMPRESSION TESTING ON PSEUDO-COHESIVE SOIL
Ofrikhter Vadim Grigor’evich
2015-09-01
Full Text Available Natural non-treated sand reinforced with randomly oriented short polypropylene fibers of 12 mm in length was tested to determine creep characteristics. This study is a part of the research aimed at encouraging fibrosand (FRS application in subsoils, embankments and retaining wall constructions. Fiber content was accounted for 0.93 %. Twin specimens were put to creep tests (1-D compression using the two curve method. The test results were analyzed and checked with the use of ageing, hardening and hereditary creep theories. On the basis of approximation of the test results the creep deformation equation at constant stress for tested fibrosand was obtained. The assessment of fibrosand secondary compression was carried out by the FORE method. As a result, the value of the void ratio by the end of the secondary compression had been eu=0.7041. For determination of the beginning of the secondary compression the rate equation was superimposed on the empirical curve. The point of the graph divergence is the beginning of the secondary compression process. The secondary compression had begun by the time moment being equal to 9360 min. The void ratio by the beginning of the secondary compression had amounted to 0.70574. Fibrosand is a specific type of improved soil relating to so-called pseudo-cohesive soil. This type of soil is characterized by cohesion like cohesive soils, but, at the same time, by the filtration coefficient of about 1 m per day like non-cohesive soils. Pseudo-cohesive soil testing helps to understand the distinctive features of the stress-strain state of this kind of materials. Municipal solid waste also relates to them.
High Temperature Behavior of Isothermally Compressed M50 Steel
Li-xing SUN; Miao-quan LI
2015-01-01
The isothermal compression of M50 steel is carried out on a Gleeble-3500 thermo-mechanical simulator in temperature range of 1 223—1 423 K and strain rates range of 10—70 s—1. The results show that the carbides play a signiifcant role in the lfow be-havior and microstructure evolution during isothermal compression of M50 steel. The average apparent activation energy for defor-mation in isothermal compression of M50 steel is (281.1±42.6) kJ∙mol—1 at the strains of 0.4—0.8. The dynamic recrystallization of austenite grains occurs in isothermal compression of M50 steel at 1 363 K and 1 393 K, enhancing with the increase of strain rate and/or strain. The volume fraction of the carbides decreases with the increase of deformation temperature during isothermal com-pression of M50 steel and the ifne carbides inhibit the dynamic recrystallization of austenite grain. With the occurrence of dynamic recrystallization, the austenite grains are reifned, leading to a minor increase in the lfow stress and apparent activation energy for deformation in isothermal compression of M50 steel. The austenite grains begin to coarsen at 1 423 K and dynamic recrystalliza-tion is limited. Hot working of M50 steel should not be performed above 1 393 K in order to achieve good workability.
Compression Maps and Stable Relations
Price, Kenneth L
2011-01-01
Balanced relations were defined by G. Abrams to extend the convolution product used in the construction of incidence rings. We define stable relations,which form a class between balanced relations and preorders. We also define a compression map to be a surjective function between two sets which preserves order, preserves off-diagonal relations, and has the additional property every transitive triple is the image of a transitive triple. We show a compression map preserves the balanced and stable properties but the compression of a preorder may be stable and not transitive. We also cover an example of a stable relation which is not the compression of a preorder. In our main theorem we provide necessary and sufficient conditions for a finite stable relation to be the compression of a preorder.
Material Compressing Test of the High Polymer Part Used in Draft Gear of Heavy Load Locomotive
Wei Yangang
2016-01-01
Full Text Available According to the actual load cases of heavy load locomotive, the material compressing tests of the high polymer parts used in the locomotive are researched. The relationship between stress and strain during the material compressing are acquired by means of comparing the many results of the material compressing tests under different test condition. The relationship between stress and strain during the material compressing is nonlinear in large range of strain, but the relationship is approximately linear in small range of strain. The material of the high polymer made in China and the material of the high polymer imported are compared through the tests. The results show that the compressing property of the material of the high polymer made in China and the material of the high polymer imported are almost same. The research offers the foundation to study the structure elasticity of the draft gear.
Compressive properties of open-cell ceramic foams
ZHANG Jun-yan; FU Yi-ming; ZENG Xiao-ming
2006-01-01
The compressive experiments of two kinds of ceramic foams were completed. The results show that the behavior of ceramic foams made by organic filling method is anisotropic. The stress-strain responses of ceramic foams made by sponge-replication show isotropy and strain rate dependence. The struts brittle breaking of net structure of this ceramic foam arises at the weakest defects of framework or at the part of framework,which causes the initiation and expanding of cracks. The compressive strength of ceramic foam is dependent on the strut size and relative density of foams.
Solov'ev, A. A.; Sochugov, N. S.; Oskomov, K. V.
2010-02-01
Methods of X-ray diffraction analysis, mass-spectrometry, and atomic force microscopy have been used to perform a comparative analysis of factors that cause the appearance of residual stresses in TiN coatings deposited by reactive magnetron sputtering and to study their effect on specific magnetic losses in electrical-sheet steel. Physical and mechanical parameters of coatings, such as hardness, elastic modulus, residual stress, microstructure, and surface morphology, have been studied. It has been shown that the level of internal stresses in a coating depends on its thickness and increases with increasing quantity and energy of ions in the deposited beam. The maximum magnitudes of compressive stresses in coatings (13 GPa) were obtained when using an unbalanced working regime of the magnetron and a negative bias at the substrate. The hardness of coatings produced under such conditions reaches 29 GPa. There has been demonstrated a possibility of reducing losses in electrical-sheet steels by about 15% by depositing surface coatings with high compressive stresses.
Zeng Lianbo; Qi Jiafu; Li Yuegang
2007-01-01
The formation and distribution of fractures are controlled by paleotectonic stress field, and their preservative status and effects on development are dominated by the modern stress field. Since Triassic, it has experienced four tectonic movements and developed four sets of tectonic fractures in the extra low-permeability sandstone reservoir at the south of western Sichuan depression. The strikes of fractures are in the S-N, NE-SW, E-W, and NW-SE directions respectively. At the end of Triassic, under the horizontal compression tectonic stress field, for which the maximum principal stress direction was NW-SE,the fractures were well developed near the S-N faults and at the end of NE-SW faults, because of their stress concentration. At the end of Cretaceous, in the horizontal compression stress fields of the NE-SW direction,the stress was obviously lower near the NE-SW faults, thus, fractures mainly developed near the S-N faults.At the end of Neogene-Early Pleistocene, under the horizontal compression tectonic stress fields of E-W direction, stress concentrated near the NE-SW faults and fractures developed at these places, especially at the end of the NE-SE faults, the cross positions of NE-SW, and S-N faults. Therefore, fractures developed mostly near S-N faults and NE-SW faults. At the cross positions of the above two sets of faults, the degree of development of the fractures was the highest. Under the modern stress field of the NW-SE direction, the NW-SE fractures were mainly the seepage ones with tensional state, the best connectivity, the widest aperture, the highest permeability, and the minimum opening pressure.
Deng, Xingli; Yang, Zhiyong; Liu, Ruen; Yi, Meiying; Lei, Deqiang; Wang, Zhi; Zhao, Hongyang
2013-01-01
The safety of gamma knife radiosurgery should be considered when treating pituitary adenomas. To determine the maximum tolerated dose of radiation delivered by gamma knife radiosurgery to optic nerves. An animal model designed to establish prolonged balloon compression of the optic chiasm and parasellar region was developed to mimic the optic nerve compression caused by pituitary adenomas. Twenty cats underwent surgery to place a balloon for compression effect and 20 cats in a sham operation group received microsurgery without any treatment. The effects of gamma knife irradiation at 10-13 Gy on normal (sham operation group) and compressed (optic nerve compression group) optic nerves were investigated by pattern visual evoked potential examination and histopathology. Gamma knife radiosurgery at 10 Gy had almost no effect. At 11 Gy, P100 latency was significantly prolonged and P100 amplitude was significantly decreased in compressed optic nerves, but there was little change in the normal optic nerves. Doses of 11 Gy and higher induced significant electrophysiological variations and degeneration of the myelin sheath and axons in both normal and compressed optic nerves. Compressed optic nerves are more sensitive to gamma knife radiosurgery than normal optic nerves. The minimum dose of gamma knife radiosurgery that causes radiation injury in normal optic nerves is 12 Gy; however, the minimum dose is 11 Gy in compressed optic nerves. Copyright © 2013 S. Karger AG, Basel.
Omeltchenko, Andrey; Bachlechner, Martina E.; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya; Ebbsjoe, Ingvar; Madhukar, Anupam; Messina, Paul
2000-01-10
Parallel molecular dynamics simulations are performed to determine atomic-level stresses in Si(111)/Si {sub 3}N{sub 4}(0001) and Si(111)/a-Si {sub 3}N{sub 4} nanopixels. Compared to the crystalline case, the stresses in amorphous Si{sub 3}N {sub 4} are highly inhomogeneous in the plane of the interface. In silicon below the interface, for a 25 nm square mesa stress domains with triangular symmetry are observed, whereas for a rectangular, 54 nmx33 nm , mesa tensile stress domains ({approx}300 Angstrom) are separated by Y-shaped compressive domain wall. Maximum stresses in the domains and domain walls are -2 GPa and +2 GPa , respectively. (c) 2000 The American Physical Society.
Compressive Sensing for Quantum Imaging
Howland, Gregory A.
This thesis describes the application of compressive sensing to several challenging problems in quantum imaging with practical and fundamental implications. Compressive sensing is a measurement technique that compresses a signal during measurement such that it can be dramatically undersampled. Compressive sensing has been shown to be an extremely efficient measurement technique for imaging, particularly when detector arrays are not available. The thesis first reviews compressive sensing through the lens of quantum imaging and quantum measurement. Four important applications and their corresponding experiments are then described in detail. The first application is a compressive sensing, photon-counting lidar system. A novel depth mapping technique that uses standard, linear compressive sensing is described. Depth maps up to 256 x 256 pixel transverse resolution are recovered with depth resolution less than 2.54 cm. The first three-dimensional, photon counting video is recorded at 32 x 32 pixel resolution and 14 frames-per-second. The second application is the use of compressive sensing for complementary imaging---simultaneously imaging the transverse-position and transverse-momentum distributions of optical photons. This is accomplished by taking random, partial projections of position followed by imaging the momentum distribution on a cooled CCD camera. The projections are shown to not significantly perturb the photons' momenta while allowing high resolution position images to be reconstructed using compressive sensing. A variety of objects and their diffraction patterns are imaged including the double slit, triple slit, alphanumeric characters, and the University of Rochester logo. The third application is the use of compressive sensing to characterize spatial entanglement of photon pairs produced by spontaneous parametric downconversion. The technique gives a theoretical speedup N2/log N for N-dimensional entanglement over the standard raster scanning technique
Azoumah, Y. [Laboratoire Biomasse Energie Biocarburant (LBEB), Institut International d' Ingenierie de l' Eau et de l' Environnement (2iE), Rue de la Science, 01BP 594, Ouagadougou 01 (Burkina Faso); Blin, J. [Laboratoire Biomasse Energie Biocarburant (LBEB), Institut International d' Ingenierie de l' Eau et de l' Environnement (2iE), Rue de la Science, 01BP 594, Ouagadougou 01 (Burkina Faso)]|[Unite Propre de Recherche Biomasse Energie, CIRAD-PERSYST, TA B-42/16t, 73 Avenue J.-F. Breton, 34398 Montpellier Cedex 5 (France); Daho, T. [Laboratoire de Physique et de Chimie de l' Environnement (LPCE), Departement de Physique, UFR-SEA, Universite de Ouagadougou, 03 BP 7021, Ouagadougou 03 (Burkina Faso)
2009-06-15
The need to decrease the consumption of materials and energy and to promote the use of renewable resources, such as biofuels, stress the importance of evaluating the performance of engines based on the second law of thermodynamics. This paper suggests the use of exergy analysis (as an environmental assessment tool to account wastes and determine the exergy efficiency) combined with gas emissions analysis to optimize the performance of a compression ignition (CI) engine using biofuels such as cottonseed and palm oils, pure or blended with diesel for different engine loads. The results show that the combination of exergy and gas emissions analyses is a very effective tool for evaluating the optimal loads that can be supplied by CI engines. Taking into account technical constraints of engines, a tradeoff zone of engine loads (60% and 70% of the maximum load) was established between the gas emissions (NO and CO{sub 2}) and the exergy efficiency for optimal performance of the CI engine. (author)
TURBULENT RECONNECTION IN RELATIVISTIC PLASMAS AND EFFECTS OF COMPRESSIBILITY
Takamoto, Makoto [Max-Planck-Institut für Kernphysik, Heidelberg (Germany); Inoue, Tsuyoshi [Division of Theoretical Astronomy, National Astronomical Observatory of Japan (Japan); Lazarian, Alexandre, E-mail: mtakamoto@eps.s.u-tokyo.ac.jp, E-mail: tsuyoshi.inoue@nao.ac.jp, E-mail: alazarian@facstaff.wisc.edu [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)
2015-12-10
We report on the turbulence effects on magnetic reconnection in relativistic plasmas using three-dimensional relativistic resistive magnetohydrodynamics simulations. We found that the reconnection rate became independent of the plasma resistivity due to turbulence effects similarly to non-relativistic cases. We also found that compressible turbulence effects modified the turbulent reconnection rate predicted in non-relativistic incompressible plasmas; the reconnection rate saturates, and even decays, as the injected velocity approaches to the Alfvén velocity. Our results indicate that compressibility cannot be neglected when a compressible component becomes about half of the incompressible mode, occurring when the Alfvén Mach number reaches about 0.3. The obtained maximum reconnection rate is around 0.05–0.1, which will be able to reach around 0.1–0.2 if injection scales are comparable to the sheet length.
Prediction of Concrete Compressive Strength by Evolutionary Artificial Neural Networks
Mehdi Nikoo
2015-01-01
Full Text Available Compressive strength of concrete has been predicted using evolutionary artificial neural networks (EANNs as a combination of artificial neural network (ANN and evolutionary search procedures, such as genetic algorithms (GA. In this paper for purpose of constructing models samples of cylindrical concrete parts with different characteristics have been used with 173 experimental data patterns. Water-cement ratio, maximum sand size, amount of gravel, cement, 3/4 sand, 3/8 sand, and coefficient of soft sand parameters were considered as inputs; and using the ANN models, the compressive strength of concrete is calculated. Moreover, using GA, the number of layers and nodes and weights are optimized in ANN models. In order to evaluate the accuracy of the model, the optimized ANN model is compared with the multiple linear regression (MLR model. The results of simulation verify that the recommended ANN model enjoys more flexibility, capability, and accuracy in predicting the compressive strength of concrete.
Test Method for Compression Resilience Evaluation of Textiles
Shui-yuan Hong
2013-02-01
Full Text Available A test method was proposed and a measurement system was developed to characterize the compression resilience properties of textiles based on the mechanical device, microelectronics, sensors and control system. Derived from the typical pressure-displacement curve and test data, four indices were defined to characterize the compression performance of textiles. The test principle and the evaluation method for compression resilience of textiles were introduced. Twelve types of textile fabrics with different structural features and made from different textile materials were tested. The one-way ANOVA analysis was carried out to identify the significance of the differences of the evaluation indices among the fabrics. The results show that each index is significantly different among different fabrics. The denim has the maximum compressional resilience and the polar fleece has the minimum compressional resilience.
EFFECTIVE STRESS AND STRAIN IN FINITE DEFORMATION
周喆; 秦伶俐; 黄文彬; 王红卫
2004-01-01
Whether the concept of effective stress and strain in elastic-plastic theory is still valid under the condition of finite deformation was mainly discussed. The uni-axial compression experiments in plane stress and plane strain states were chosen for study. In the two kinds of stress states, the stress- strain curve described by logarithm strain and rotated Kirchhoff stress matches the experiments data better than the curves defined by other stressstrain description.
Zhang, Yubin; Andriollo, Tito; Fæster, Søren
2016-01-01
A synchrotron technique, differential aperture X-ray microscopy (DAXM), has been applied to characterize the microstructure and analyze the local mesoscale residual elastic strain fields around graphite nodules embedded in ferrite matrix grains in ductile cast iron. Compressive residual elastic...... but with a significant overprediction of the maximum strain. This is discussed in terms of stress relaxation during cooling or during storage by plastic deformation of the nodule, the matrix or both. Relaxation by plastic deformation of the ferrite is demonstrated by the formation of low energy dislocation cell...... structure also quantified by the DAXM technique....
Application of Image Processing to Predict Compressive Behavior of Aluminum Foam
Kim Sanghoon
2016-06-01
Full Text Available An image processing technique was used to model the internal structure of aluminum foam in finite element analysis in order to predict the compressive behavior of the material. Finite element analysis and experimental tests were performed on aluminum foam with densities of 0.2, 0.25, and 0.3 g/cm3. It was found that although the compressive strength predicted from the finite element analysis was higher than that determined experimentally, the predicted compressive stress-strain curves exhibited a tendency similar to those determined from experiments for both densities. However, the behavior of the predicted compressive stress-strain curves was different from the experimental one as the applied strain increased. The difference between predicted and experimental stress-strain curves in a high strain range was due to contact between broken aluminum foam walls by the large deformation.
Karaarslan, Ahmet Adnan; Karakaşli, Ahmet; Karci, Tolga; Aycan, Hakan; Yildirim, Serhat; Sesli, Erhan
2015-06-01
The aim is to present our new method of compression, a compression tube instead of conventional compression screw and to investigate the difference of proximal locking screw bending resistance between compression screw application (6 mm wide contact) and compression tube (two contact points with 13 mm gap) application. We formed six groups each consisting of 10 proximal locking screws. On metal cylinder representing lesser trochanter level, we performed 3-point bending tests with compression screw and with compression tube. We determined the yield points of the screws in 3-point bending tests using an axial compression testing machine. We determined the yield point of 5 mm screws as 1963±53 N (mean±SD) with compression screw, and as 2929±140 N with compression tubes. We found 51% more locking screw bending resistance with compression tube than with compression screw (p=0,000). Therefore compression tubes instead of compression screw must be preferred at femur compression nails.
Compressed Submanifold Multifactor Analysis.
Luu, Khoa; Savvides, Marios; Bui, Tien; Suen, Ching
2016-04-14
Although widely used, Multilinear PCA (MPCA), one of the leading multilinear analysis methods, still suffers from four major drawbacks. First, it is very sensitive to outliers and noise. Second, it is unable to cope with missing values. Third, it is computationally expensive since MPCA deals with large multi-dimensional datasets. Finally, it is unable to maintain the local geometrical structures due to the averaging process. This paper proposes a novel approach named Compressed Submanifold Multifactor Analysis (CSMA) to solve the four problems mentioned above. Our approach can deal with the problem of missing values and outliers via SVD-L1. The Random Projection method is used to obtain the fast low-rank approximation of a given multifactor dataset. In addition, it is able to preserve the geometry of the original data. Our CSMA method can be used efficiently for multiple purposes, e.g. noise and outlier removal, estimation of missing values, biometric applications. We show that CSMA method can achieve good results and is very efficient in the inpainting problem as compared to [1], [2]. Our method also achieves higher face recognition rates compared to LRTC, SPMA, MPCA and some other methods, i.e. PCA, LDA and LPP, on three challenging face databases, i.e. CMU-MPIE, CMU-PIE and Extended YALE-B.