Directory of Open Access Journals (Sweden)
A. Tata
2009-01-01
Full Text Available This paper presents a nonlinear finite element modeling and analysis of rectangular normal-strength reinforced concrete columns confined with transverse steel under axial compressive loading. In this study, the columns were modeled as discrete elements using ANSYS nonlinear finite element software. Concrete was modeled with 8-noded SOLID65 elements that can translate either in the x-, y-, or z-axis directions from ANSYS element library. Longitudinal and transverse steels were modeled as discrete elements using 3D-LINK8 bar elements available in the ANSYS element library. The nonlinear constitutive law of each material was also implemented in the model. The results indicate that the stress-strain relationships obtained from the analytical model using ANSYS are in good agreement with the experimental data. This has been confirmed with the insignificant difference between the analytical and experimental, i.e. 5.65 and 2.80 percent for the peak stress and the strain at the peak stress, respectively. The comparison shows that the ANSYS nonlinear finite element program is capable of modeling and predicting the actual nonlinear behavior of confined concrete column under axial loading. The actual stress-strain relationship, the strength gain and ductility improvement have also been confirmed to be satisfactorily.
Directory of Open Access Journals (Sweden)
M. Boudjema
2003-01-01
Full Text Available The elastic response of many rocks to quasistatic stress changes is highly nonlinear and hysteretic, displaying discrete memory. Rocks also display unusual nonlinear response to dynamic stress changes. A model to describe the elastic behavior of rocks and other consolidated materials is called the Preisach-Mayergoyz (PM space model. In contrast to the traditional analytic approach to stress-strain, the PM space picture establishes a relationship between the quasistatic data and a number density of hysteretic mesoscopic elastic elements in the rock. The number density allows us to make quantitative predictions of dynamic elastic properties. Using the PM space model, we analyze a complex suite of quasistatic stress-strain data taken on Berea sandstone. We predict a dynamic bulk modulus and a dynamic shear modulus surface as a function of mean stress and shear stress. Our predictions for the dynamic moduli compare favorably to moduli derived from time of flight measurements. We derive a set of nonlinear elastic constants and a set of constants that describe the hysteretic behavior of the sandstone.
Weatheritt, Jack; Sandberg, Richard
2016-11-01
This paper presents a novel and promising approach to turbulence model formulation, rather than putting forward a particular new model. Evolutionary computation has brought symbolic regression of scalar fields into the domain of algorithms and this paper describes a novel expansion of Gene Expression Programming for the purpose of tensor modeling. By utilizing high-fidelity data and uncertainty measures, mathematical models for tensors are created. The philosophy behind the framework is to give freedom to the algorithm to produce a constraint-free model; its own functional form that was not previously imposed. Turbulence modeling is the target application, specifically the improvement of separated flow prediction. Models are created by considering the anisotropy of the turbulent stress tensor and formulating non-linear constitutive stress-strain relationships. A previously unseen flow field is computed and compared to the baseline linear model and an established non-linear model of comparable complexity. The results are highly encouraging.
Stress-Strain Relationship and Failure Criterion for Concrete after Freezing and Thawing Cycles
Institute of Scientific and Technical Information of China (English)
Luo Xin; Wei Jun
2006-01-01
The research of the failure criterion and one-dimensional stress-strain relationship of deteriorated concrete were carried out.Based on the damage mechanics theory, the damage which reflects the alternation of internal state of material were introduced into the formula presented by Desayi and Krishman and the weighted twin-shear strength theory. As a nondestructive examination method in common use, the ultrasonic technique was adopted in the study, and the ultrasonic velocity was used to establish the damage variable. After that, the failure criterion and one-dimensional stress-strain relationship for deteriorated concrete were obtained.Eventually, tests were carried out to study the evolution laws on the damage. The results show that the more freezing and thawing cycles are, the more apparently the failure surface shrinks. Meanwhile, the comparison between theoretical data and experimental data verifies the rationality of the damage-based one-dimensional stress-strain relationship proposed.
Effect of Engineering Character on Stress-Strain Relationship in Post-Peak Area
Institute of Scientific and Technical Information of China (English)
TANG Lei; KE Min-yong; YAN Jian-hua
2003-01-01
Constitutive experiments are the base of all rock mechanics works. The effect of engineering character on constitutive law is a new problem of rock mechanics. The results of series specimens based on the uniaxial and plane strain compression experiments were presented and discussed. It is found that engineering or experiment character has obvious effects on stress-strain relationship and especially on mechanic parameters in post-peak area. And the law of size effect of softening materials was also discussed.
Theoretical and experimental study on relationship between stress-strain and temperature variation
Institute of Scientific and Technical Information of China (English)
2009-01-01
Principle on temperature response to the stress-strain variation is fundamental to the relationship between thermal radiation variation and stress-strain field. Current research indicates that temperature has a sensitive response to rock deformation under the condition of normal temperature background. However, the basic physical relationship between deformation and temperature variation is not clear and need to be investigated further. In this paper, principle on temperature response to stress-strain variation is studied in detail, based on thermodynamics, elastic strain theory, and experiments on both ideal material and rock. In the stage of elastic deformation, results indicate that: 1) temperature increment is positively correlated with volume strain variation. Temperature rises with hydrostatic pressure increase. In other words, temperature rises when the specimen is under the compressive state whereas temperature drops under the tensile state. 2) Pure shear deformation does not contribute to tempera- ture variation. Namely, shape change of specimen does not produce temperature variation. However, there exist the relative tensile area and the compressive one in the specimen under the state of pure shear. Temperature drops within the relative tensile area while temperature rises within the compressive areas during the process of loading.
Theoretical and experimental study on relationship between stress-strain and temperature variation
Institute of Scientific and Technical Information of China (English)
CHEN ShunYun; LIU LiQiang; LIU PeiXun; MA Jin; CHEN GuoQiang
2009-01-01
Principle on temperature response to the stress-strain variation is fundamental to the relationship between thermal radiation variation and stress-strain field.Current research indicates that temperature has a sensitive response to rock deformation under the condition of normal temperature background.However,the basic physical relationship between deformation and temperature variation is not clear and need to be investigated further.In this paper,principle on temperature response to stress-strain variation is studied in detail,based on thermodynamics,elastic strain theory,and experiments on both ideal material and rock.In the stage of elastic deformation,results indicate that:1) temperature increment is positively correlated with volume strain variation.Temperature rises with hydrostatic pressure increase.In other words,temperature rises when the specimen is under the compressive state whereas temperature drops under the tensile state.2) Pure shear deformation does not contribute to temperature variation.Namely,shape change of specimen does not produce temperature variation.However,there exist the relative tensile area and the compressive one in the specimen under the state of pure shear.Temperature drops within the relative tensile area while temperature rises within the compressive areas during the process of loading.
Energy Technology Data Exchange (ETDEWEB)
Duffy, Stephen [Cleveland State Univ., Cleveland, OH (United States)
2013-09-09
This project will implement inelastic constitutive models that will yield the requisite stress-strain information necessary for graphite component design. Accurate knowledge of stress states (both elastic and inelastic) is required to assess how close a nuclear core component is to failure. Strain states are needed to assess deformations in order to ascertain serviceability issues relating to failure, e.g., whether too much shrinkage has taken place for the core to function properly. Failure probabilities, as opposed to safety factors, are required in order to capture the bariability in failure strength in tensile regimes. The current stress state is used to predict the probability of failure. Stochastic failure models will be developed that can accommodate possible material anisotropy. This work will also model material damage (i.e., degradation of mechanical properties) due to radiation exposure. The team will design tools for components fabricated from nuclear graphite. These tools must readily interact with finite element software--in particular, COMSOL, the software algorithm currently being utilized by the Idaho National Laboratory. For the eleastic response of graphite, the team will adopt anisotropic stress-strain relationships available in COMSO. Data from the literature will be utilized to characterize the appropriate elastic material constants.
Stress-strain relationship with soil structural parameters of collapse loess
Institute of Scientific and Technical Information of China (English)
2008-01-01
Through the tri-axial shearing tests of unsaturated intact loess and based on the concept of comprehensive soil structural potential,this paper reveals the changing laws of soil structural property under the triaxial stress conditions and establishes a mathematical expression equation of structural parameters,whereby reflecting the effects of unsaturated loess water content,stress and strain states,which is introduced into the shearing stress and shearing strain relation to obtain the structural stress-strain relation.The tests reveal that the loess dilatancy is of shearing contraction and shearing expansion,whereby indicating that there is a good linear relation between the stress ratio and shearing expansion strain ratio.The larger consolidation confining pressure is,the larger the stress of shearing contraction and expansion critical point is;and the larger water content is,the smaller the strain ratio of shearing contraction and expansion critical point is.Finally,the constitutive model is established to reflect the variation in loess structure,stressstrain softening and hardening,and shearing contraction and shearing expansion features.Through the comparative analysis,the stress-strain curves described by the constitutive relationship are found to be in good conformity with test results,whereby testing the rationality of the model in this paper.
Modelling of Stress-Strain Relationship of Toyoura Sand in Large Cyclic Torsional Loading
Hong Nam, Nguyen; Koseki, Junichi
The relationships between normalized shear stress and plastic shear strain of air-dried, dense Toyoura sand measured during large amplitude cyclic torsional loading with using local strain measurement could be well simulated numerically by the proportional rule combined with the drag rule. The proportional rule is an extended version of the Masing's second rule and can account for unsymmetrical stress strain behavior about neutral axis. The drag rule can account for strain hardening in cyclic loadings. Use of the newly proposed hypoelastic model for the quasi-elastic properties, the backbone curve using general hyperbolic equation or newly proposed lognormal equation for monotonic loading behavior, and the combination of the proportional rule and the drag rule for cyclic loading behavior would enable more precise simulation of deformation properties than before.
Longitudinal residual strain and stress-strain relationship in rat small intestine
Directory of Open Access Journals (Sweden)
Fan Yanhua
2006-06-01
Full Text Available Abstract Background To obtain a more detailed description of the stress-free state of the intestinal wall, longitudinal residual strain measurements are needed. Furthermore, data on longitudinal stress-strain relations in visceral organs are scarce. The present study aims to investigate the longitudinal residual strain and the longitudinal stress-strain relationship in the rat small intestine. Methods The longitudinal zero-stress state was obtained by cutting tissue strips parallel to the longitudinal axis of the intestine. The longitudinal residual stress was characterized by a bending angle (unit: degrees per unit length and positive when bending outwards. Residual strain was computed from the change in dimensions between the zero-stress state and the no-load state. Longitudinal stresses and strains were computed from stretch experiments in the distal ileum at luminal pressures ranging from 0–4 cmH2O. Results Large morphometric variations were found between the duodenum and ileum with the largest wall thickness and wall area in the duodenum and the largest inner circumference and luminal area in the distal ileum (p 0.5. The longitudinal residual strain was tensile at the serosal surface and compressive at the mucosal surface. Hence, the neutral axis was approximately in the mid-wall. The longitudinal residual strain and the bending angle was not uniform around the intestinal circumference and had the highest values on the mesenteric sides (p α constant increased with the pressure, indicating the intestinal wall became stiffer in longitudinal direction when pressurized. Conclusion Large longitudinal residual strains reside in the small intestine and showed circumferential variation. This indicates that the tissue is not uniform and cannot be treated as a homogenous material. The longitudinal stiffness of the intestinal wall increased with luminal pressure. Longitudinal residual strains must be taken into account in studies of
Relationship between fatigue life in the creep-fatigue region and stress-strain response
Berkovits, A.; Nadiv, S.
1988-01-01
On the basis of mechanical tests and metallographic studies, strainrange partitioned lives were predicted by introducing stress-strain materials parameters into the Universal Slopes Equation. This was the result of correlating fatigue damage mechanisms and deformation mechanisms operating at elevated temperatures on the basis of observed mechanical and microstructural behavior. Correlation between high temperature fatigue and stress strain properties for nickel base superalloys and stainless steel substantiated the method. Parameters which must be evaluated for PP- and CC- life are the maximum stress achievable under entirely plastic and creep conditions respectively and corresponding inelastic strains, and the two more pairs of stress strain parameters must be ascertained.
Liang, Liang; Liu, Minliang; Sun, Wei
2017-09-20
Biological collagenous tissues comprised of networks of collagen fibers are suitable for a broad spectrum of medical applications owing to their attractive mechanical properties. In this study, we developed a noninvasive approach to estimate collagenous tissue elastic properties directly from microscopy images using Machine Learning (ML) techniques. Glutaraldehyde-treated bovine pericardium (GLBP) tissue, widely used in the fabrication of bioprosthetic heart valves and vascular patches, was chosen to develop a representative application. A Deep Learning model was designed and trained to process second harmonic generation (SHG) images of collagen networks in GLBP tissue samples, and directly predict the tissue elastic mechanical properties. The trained model is capable of identifying the overall tissue stiffness with a classification accuracy of 84%, and predicting the nonlinear anisotropic stress-strain curves with average regression errors of 0.021 and 0.031. Thus, this study demonstrates the feasibility and great potential of using the Deep Learning approach for fast and noninvasive assessment of collagenous tissue elastic properties from microstructural images. In this study, we developed, to our best knowledge, the first Deep Learning-based approach to estimate the elastic properties of collagenous tissues directly from noninvasive second harmonic generation images. The success of this study holds promise for the use of Machine Learning techniques to noninvasively and efficiently estimate the mechanical properties of many structure-based biological materials, and it also enables many potential applications such as serving as a quality control tool to select tissue for the manufacturing of medical devices (e.g. bioprosthetic heart valves). Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Neff, K. L.; Farr, T.
2016-12-01
Aquifer subsidence due to groundwater abstraction poses a significant threat to aquifer sustainability and infrastructure. The need to prevent permanent compaction to preserve aquifer storage capacity and protect infrastructure begs a better understanding of how compaction is related to groundwater abstraction and aquifer hydrogeology. The stress-strain relationship between hydraulic head changes and aquifer compaction has previously been observed to be hysteretic in both empirical and modeling studies. Here, subsidence data for central California's San Joaquin Valley derived from interferometric synthetic aperture radar (InSAR) for the period 2007-2016 is examined relative to hydraulic head levels in monitoring and production wells collected by the California Department of Water Resources. Such a large and long-term data set is available for empirical analysis for the first time thanks to advances in InSAR data collection and geospatial data management. The California Department of Water Resources (DWR) funded this work to provide the background and an update on subsidence in the Central Valley to support future policy. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.
Amann, C. P.; Siebenbürger, M.; Ballauff, M.; Fuchs, M.
2015-05-01
Transient stress-strain relations close to the colloidal glass transition are obtained within the integration through transients framework generalizing mode coupling theory to flow driven systems. Results from large-scale numerical calculations are quantitatively compared to experiments on thermosensitive microgels, which reveals that theory captures the magnitudes of stresses semi-quantitatively even in the nonlinear regime, but overestimates the characteristic strain where plastic events set in. The former conclusion can also be drawn from flow curves, while the latter conclusion is supported by a comparison to single particle motion measured by confocal microscopy. The qualitative picture, as previously obtained from simplifications of the theory in schematic models, is recovered by the quantitative solutions of the theory for Brownian hard spheres.
Amann, C M; Siebenbürger, M; Ballauff, M; Fuchs, M
2015-05-20
Transient stress-strain relations close to the colloidal glass transition are obtained within the integration through transients framework generalizing mode coupling theory to flow driven systems. Results from large-scale numerical calculations are quantitatively compared to experiments on thermosensitive microgels, which reveals that theory captures the magnitudes of stresses semi-quantitatively even in the nonlinear regime, but overestimates the characteristic strain where plastic events set in. The former conclusion can also be drawn from flow curves, while the latter conclusion is supported by a comparison to single particle motion measured by confocal microscopy. The qualitative picture, as previously obtained from simplifications of the theory in schematic models, is recovered by the quantitative solutions of the theory for Brownian hard spheres.
Carbone, Daniele; Aloisi, Marco; Vinciguerra, Sergio; Puglisi, Giuseppe
2014-05-01
During the time interval between the 1991-93 and 2001 main flank eruptions of Mt. Etna, volcanic activity was confined to the summit vents. Ground deformation and tomography studies suggest that this activity was fed by a magma body located beneath the north-west flank of the volcano, at a depth of around 7 km b.s.l.. Conversely, gravity studies indicate that the most important mass redistributions during the same period took place within an elongated volume centered below the southeastern sector of the volcano, at depths of 2-4 km b.s.l.. The phases of gravity decrease during the 1994-2001 period coincide with phases of higher strain release rate. The coupling between gravity and seismic data could reflect changes in the rate of micro-fracturing along the NNW-SSE weakness zone that cuts the SE slope of the volcano. This interpretation allows to explain why the main pressure and mass sources active at Etna during the 1994-2001 period do not coincide. The extensional dynamics of the southeastern flank of Etna may represent a second-order effect, triggered by the pressure source below the western flank and accommodated along the NNW-SSE weakness zone. In order to gain quantitative insight into the relationship between stress, strain and mass changes at Etna during the 1994-2001 period, we use a finite element modeling approach. Relying on recent studies involving stress- and temperature-induced degradation of the mechanical properties of rocks, we hypothesize that the inferred NNW-SSE weakness zone is characterized by an anomalously low Young's modulus (E). Results of our analysis are summarized in the following two points. (i) The presence of the weakness zone creates a distortion of the displacements field induced by the deeper pressure source, locally resulting in a weak extensional regime. This finding supports the hypothesis of a cause-effect relation between deeper pressurization beneath the western flank and shallower extension across the fracture zone beneath
Adaptive regression for modeling nonlinear relationships
Knafl, George J
2016-01-01
This book presents methods for investigating whether relationships are linear or nonlinear and for adaptively fitting appropriate models when they are nonlinear. Data analysts will learn how to incorporate nonlinearity in one or more predictor variables into regression models for different types of outcome variables. Such nonlinear dependence is often not considered in applied research, yet nonlinear relationships are common and so need to be addressed. A standard linear analysis can produce misleading conclusions, while a nonlinear analysis can provide novel insights into data, not otherwise possible. A variety of examples of the benefits of modeling nonlinear relationships are presented throughout the book. Methods are covered using what are called fractional polynomials based on real-valued power transformations of primary predictor variables combined with model selection based on likelihood cross-validation. The book covers how to formulate and conduct such adaptive fractional polynomial modeling in the s...
An experimental study on stress-strain behavior and constitutive model of hardfill material
Wu, Mengxi; Du, Bin; Yao, Yuancheng; He, Xianfeng
2011-11-01
Hardfill is a new type of artificially cemented material for dam construction works, with a wide application prospect. Its mechanical behavior lies between concrete and rockfill materials. A series of large-scale triaxial tests are performed on hardfill specimens at different ages, and the stress-strain behavior of hardfill is further discussed. The strength and stress-strain relationship of hardfill materials show both frictional mechanism and cohesive mechanism. An age-related constitutive model of hardfill is developed, which is a parallel model consisting of two components, rockfill component and cementation component. Moreover, a comparison is made between the simulated and the experimental results, which shows that the parallel model can reflect the mechanical characteristics of both rockfill-like nonlinearity and concrete-like age relativity. In addition, a simplified method for the determination of parameters is proposed.
Incremental stress-strain law for graphite under multiaxial loadings
Energy Technology Data Exchange (ETDEWEB)
Tzung, F.
1979-11-01
An incremental stress-strain law for describing the nonlinear, compressible and asymmetric behavior of graphite under tension and compression as well as complex loadings is derived based on a dry friction model in the theory of plasticity. Stress-strain relations are defined by longitudinal-lateral strain measurements for specimens under uniaxial tension-compression. Agreements with experimentally determined curves from biaxial loading experiments are shown. Agreements in finite element computations using the present model with strain measurements for diametral compression and 4-point bend tests of graphite are also obtained.
Tensile stress-strain behavior of hybrid composite laminates
Kennedy, J. M.
1983-01-01
A study was made of the stress-strain response of several hybrid laminates, and the damage was correlated with nonlinear stress-strain response and ultimate strength. The fibers used in the laminates were graphite, S-glass, and Kevlar. Some laminates with graphite fibers had perforated Mylar film between plies, which lowered the interlaminar bond strength. The laminate configurations were chosen to be like those of buffer strips in large panels and fracture coupons. Longitudinal and transverse specimens were loaded in tension to failure. Some specimens were radiographed to reveal damage due to edge effects. Stress-strain response is discussed in terms of damage shown by the radiographs. Ultimate strengths are compared with simple failure criteria, one of which account for damage.
Directory of Open Access Journals (Sweden)
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.
NONLINEAR ELASTICITY OF BLOOD ARTERIAL DUCT
Institute of Scientific and Technical Information of China (English)
黄孟才; 顾忠; 沈俊; 唐复勇
1991-01-01
The paper deals with nonlinear elasticity of blood arterial duct, in which the artery is modeled to bea locally triclinic, transverse isotropic, incorapressible, axisymmetric and thickwalled tube with large deformations, The nonlinear coustitutive relationship of arterial tissues is based on the theorv of Green and Adkins. A nonlinear strain energy density function is introduced for nonlinear stress-strain relationship of second order, in which the coefficient of each term is expressed by means of a Lame’s constant, The elasticity constants are nqcessary to describe such a uonlinear finite strain etastieity of the second order, These constants are determined by means of the stress-strain increment theory.
Characterization and Stress-Strain Relationship of Leached Concrete%溶蚀混凝土的表征及应力-应变关系
Institute of Scientific and Technical Information of China (English)
黄蓓; 钱春香
2011-01-01
溶蚀作用导致水泥基材料的孔隙率增加从而影响材料的传输及力学性能.对于结构中的既有混凝土,采用非破损和局部破损方法测量和评估溶蚀混凝士的承载力是非常重要的.采用酚酞指示剂法、孔隙溶液pH测量法、超声波无损检测法,对溶蚀混凝土进行了溶蚀损伤程度表征;试验测试了溶蚀混凝七的单轴应力一应变关系:采用XRD和压汞分析研究了混凝土溶蚀机理.研究表明:酚酞指示剂法可以较为直观的表征溶蚀损伤深度,测量的溶蚀程度与强度衰减较为接近:Ca(OH)2和C-S-H凝胶在溶蚀过程中同时溶出,Ca(OH)2是造成早期溶蚀质量损伤的主要原因:混凝土溶蚀后有害孔的数量增加,对混凝土的耐久性产生不利影响;溶蚀混凝土的应力-应变关系曲线形状与普通混凝土相似,但表现出良好的延性及韧性.%Leaching of cementitious materials leads to an increase in porosity, which has important consequences on transport and mechanical properties. It is thus important to investigate the methods that can be used in unleached concrete to evaluate the residual bearing capacity of leached concrete. In this paper, the degradation degree of leached concrete was characterized by three methods (i.e., spraying phenolphthalein, pH value of pore solution, velocity of supersonic). The stress-strain curve of leached concrete under unaxial loads was examined by a material test system. The kinetics of degradation was analyzed by X-ray diffraction and mercury intrusion test. The results show that spraying phenolphthalein is an effective way to characterize the leaching degradation related to attenuation of compressive strength. The dissolution happened both in portlandite and C-S-H gel during the leaching duration and the dissolution of portlandite is a main cause of mass loss at the early stages of leaching. A number of harmful pores with the size above 200 nm increased in the leaching of
Stress-strain relationship of granular materials based on two cell systems%基于双胞元的颗粒材料应力-应变关系研究
Institute of Scientific and Technical Information of China (English)
董启朋; 姚海林; 卢正; 詹永祥
2014-01-01
基于细观力学，建立颗粒材料的宏观应力-应变与接触力、接触位移、枝矢量等细观量之间的关系。用改进的Voronoi-Delaunay法对颗粒材料进行几何和物理上划分，得到改进Bagi双胞元体系；以固体胞元为基础，运用牛顿第二定律和Gauss定理提出含有旋转矢量和重力的颗粒材料平均等效应力，避免了颗粒材料的准静态假设；在孔隙胞元区域内利用变形协调条件推导出含有孔隙面矢量等几何变量的颗粒材料平均等效应变。结合文献的二维颗粒材料宏观试验结果验证了双胞元平均等效应力-应变的正确性；在三维情形下，对比双胞元等效应变和最优拟合应变结果，同样验证了基于双胞元的颗粒材料应力-应变关系，因此，该颗粒材料应力-应变关系可以为数值模拟颗粒材料力学行为提供依据。%Based on granular mesomechanics, this paper sets up the relationship between the macro stress-strain and the mesoscopic quantities including the contact force, contact displacement and branch vector in granular materials. The method of improved Voronoi-Delaunay tessellation for granular materials in geometry and physics is further modified into two cell systems of Bagi. Taking solid cell systems as the basic elements, the average stress tensor that includes particle rotation vector and acceleration of gravity is derived based on Newton’s second law of motion and Gauss theorem. It avoids a static hypothesis. The average strain tensor expression including the void surface vector is derived based on the void cell with compatibility requirement. Two cell systems average equivalent stress-strain is correct combined with the literature of experimental resulting in two dimensions. Compared with two cell systems average equivalent strain and best fitting stress results under three dimensions, granular material stress-strain relationship based on the two cell systems is also
Institute of Scientific and Technical Information of China (English)
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.
2002-01-01
The Atlas of Stress-Strain Curves, Second Edition is substantially bigger in page dimensions, number of pages, and total number of curves than the previous edition. It contains over 1,400 curves, almost three times as many as in the 1987 edition. The curves are normalized in appearance to aid making comparisons among materials. All diagrams include metric (SI) units, and many also include U.S. customary units. All curves are captioned in a consistent format with valuable information including (as available) standard designation, the primary source of the curve, mechanical properties (including hardening exponent and strength coefficient), condition of sample, strain rate, test temperature, and alloy composition. Curve types include monotonic and cyclic stress-strain, isochronous stress-strain, and tangent modulus. Curves are logically arranged and indexed for fast retrieval of information. The book also includes an introduction that provides background information on methods of stress-strain determination, on...
BILAM: a composite laminate failure-analysis code using bilinear stress-strain approximations
Energy Technology Data Exchange (ETDEWEB)
McLaughlin, P.V. Jr.; Dasgupta, A.; Chun, Y.W.
1980-10-01
The BILAM code which uses constant strain laminate analysis to generate in-plane load/deformation or stress/strain history of composite laminates to the point of laminate failure is described. The program uses bilinear stress-strain curves to model layer stress-strain behavior. Composite laminates are used for flywheels. The use of this computer code will help to develop data on the behavior of fiber composite materials which can be used by flywheel designers. In this program the stress-strain curves are modelled by assuming linear response in axial tension while using bilinear approximations (2 linear segments) for stress-strain response to axial compressive, transverse tensile, transverse compressive and axial shear loadings. It should be noted that the program attempts to empirically simulate the effects of the phenomena which cause nonlinear stress-strain behavior, instead of mathematically modelling the micromechanics involved. This code, therefore, performs a bilinear laminate analysis, and, in conjunction with several user-defined failure interaction criteria, is designed to provide sequential information on all layer failures up to and including the first fiber failure. The modus operandi is described. Code BILAM can be used to: predict the load-deformation/stress-strain behavior of a composite laminate subjected to a given combination of in-plane loads, and make analytical predictions of laminate strength.
Parameter Optimisation of Stress-strain Constitutive Equations Using Genetic Algorithms
Institute of Scientific and Technical Information of China (English)
Y. Y. Yang; M. Mahfouf; D.A.Linkens
2003-01-01
The accuracy of numerical simulations and many other material design calculations, such as the rolling force, rollingtorque, etc., depends on the description of stress-strain relationship of the deformed materials. One common methodof describing the stres
Measurement of stress-strain behaviour of human hair fibres using optical techniques.
Lee, J; Kwon, H J
2013-06-01
Many studies have presented stress-strain relationship of human hair, but most of them have been based on an engineering stress-strain curve, which is not a true representation of stress-strain behaviour. In this study, a more accurate 'true' stress-strain curve of human hair was determined by applying optical techniques to the images of the hair deformed under tension. This was achieved by applying digital image cross-correlation (DIC) to 10× magnified images of hair fibres taken under increasing tension to estimate the strain increments. True strain was calculated by summation of the strain increments according to the theoretical definition of 'true' strain. The variation in diameter with the increase in longitudinal elongation was also measured from the 40× magnified images to estimate the Poisson's ratio and true stress. By combining the true strain and the true stress, a true stress-strain curve could be determined, which demonstrated much higher stress values than the conventional engineering stress-strain curve at the same degree of deformation. Four regions were identified in the true stress-strain relationship and empirical constitutive equations were proposed for each region. Theoretical analysis on the necking condition using the constitutive equations provided the insight into the failure mechanism of human hair. This analysis indicated that local thinning caused by necking does not occur in the hair fibres, but, rather, relatively uniform deformation takes place until final failure (fracture) eventually occurs.
Mital, Subodh K.; Murthy, Pappu L. N.; Chamis, Christos C.
1994-01-01
A computational simulation procedure is presented for nonlinear analyses which incorporates microstress redistribution due to progressive fracture in ceramic matrix composites. This procedure facilitates an accurate simulation of the stress-strain behavior of ceramic matrix composites up to failure. The nonlinearity in the material behavior is accounted for at the constituent (fiber/matrix/interphase) level. This computational procedure is a part of recent upgrades to CEMCAN (Ceramic Matrix Composite Analyzer) computer code. The fiber substructuring technique in CEMCAN is used to monitor the damage initiation and progression as the load increases. The room-temperature tensile stress-strain curves for SiC fiber reinforced reaction-bonded silicon nitride (RBSN) matrix unidirectional and angle-ply laminates are simulated and compared with experimentally observed stress-strain behavior. Comparison between the predicted stress/strain behavior and experimental stress/strain curves is good. Collectively the results demonstrate that CEMCAN computer code provides the user with an effective computational tool to simulate the behavior of ceramic matrix composites.
Calculation of the stress-strain stiffness matrix for given strains in an inelastic material
Energy Technology Data Exchange (ETDEWEB)
Friedrich, C.M.
1978-01-01
In the implicit method of non-linear analysis of stiffness matrices of finite elements, deflection fields and hence strains are assumed known at one stage of the calculations. A procedure is developed to calculate the stress-strain stiffness matrix from the strains without iteration of the stress components when the material is inelastic.
Stress/strain Modelling of Casting Processes in the Framework of the Control-Volume Method
DEFF Research Database (Denmark)
Hattel, Jesper Henri; Thorborg, Jesper; Andersen, Søren
1998-01-01
Realistic computer simulations of casting processes call for the solution of both thermal, fluid-flow and stress/strain related problems. The multitude of the influencing parameters, and their non-linear, transient and temperature dependent nature, make the calculations complex. Therefore the need......, the present model is based on the mainly decoupled representation of the thermal, mechanical and microstructural processes. Examples of industrial applications, such as predicting residual deformations in castings and stress levels in die casting dies, are presented...
Relationship between the magnitude of singular value and nonlinear stability
Institute of Scientific and Technical Information of China (English)
穆穆; 郭欢; 王佳峰; 李勇
2001-01-01
The relationship between the magnitude of singular value and nonlinear stability or instability of the basic flow is investigated. The results show that there is a good corresponding relationship between them. The magnitude of singular value decreases as the stability (or instability) of the basic flow increases (or decreases). In the stable case, the magnitude of the maximum singular value is much smaller than in the unstable case.
Karimi, Alireza; Navidbakhsh, Mahdi; Alizadeh, Mansour; Razaghi, Reza
2014-10-01
There have been different stress-strain definitions to measure the elastic modulus of spongy materials, especially polyvinyl alcohol (PVA) sponge. However, there is no agreement as to which stress-strain definition should be implemented. This study was aimed to show how different results are given by the various definitions of stress-strain used, and to recommend a specific definition when testing spongy materials. A fabricated PVA sponge was subjected to a series of tensile tests in order to measure its mechanical properties. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were used to determine the elastic modulus. The results revealed that the Almansi-Hamel strain definition exhibited the highest non-linear stress-strain relation and, as a result, may overestimate the elastic modulus at different stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress). The Green-St. Venant strain definition failed to address the non-linear stress-strain relation using different definitions of stress and invoked an underestimation of the elastic modulus values. Engineering stress and strain definitions were only valid for small strains and displacements, which make them impractical when analyzing spongy materials. The results showed that the effect of varying the stress definition on the maximum stress measurements was significant but not when calculating the elastic modulus. It is important to consider which stress-strain definition is employed when characterizing the mechanical properties of spongy materials. Although the true stress-true strain definition exhibits a non-linear relation, we favor it in spongy materials mechanics as it gives more accurate measurements of the material's response using the instantaneous values.
Prediction of stress-strain behavior of ceramic matrix composites using unit cell model
Directory of Open Access Journals (Sweden)
Suzuki Takuya
2015-01-01
Full Text Available In this study, the elastic modulus and the stress-strain curve of ceramic matrix composites (CMCs were predicted by using the unit cell model that consists of fiber bundles and matrix. The unit cell model was developed based on the observation of cross sections of CMCs. The elastic modulus of CMCs was calculated from the results of finite element analysis using the developed model. The non-linear behavior of stress-strain curve of CMCs was also predicted by taking the degradation of the elastic modulus into consideration, where the degradation was related to the experimentally measured crack density in CMCs. The approach using the unit cell model was applied to two kinds of CMCs, and good agreement was obtained between the experimental and the calculated results.
Regional variability among nonlinear chlorophyll-phosphorus relationships in lakes
Filstrup, Christopher T.; Wagner, Tyler; Soranno, Patricia A.; Stanley, Emily H.; Stow, Craig A.; Webster, Katherine E.; Downing, John A.
2014-01-01
The relationship between chlorophyll a (Chl a) and total phosphorus (TP) is a fundamental relationship in lakes that reflects multiple aspects of ecosystem function and is also used in the regulation and management of inland waters. The exact form of this relationship has substantial implications on its meaning and its use. We assembled a spatially extensive data set to examine whether nonlinear models are a better fit for Chl a—TP relationships than traditional log-linear models, whether there were regional differences in the form of the relationships, and, if so, which regional factors were related to these differences. We analyzed a data set from 2105 temperate lakes across 35 ecoregions by fitting and comparing two different nonlinear models and one log-linear model. The two nonlinear models fit the data better than the log-linear model. In addition, the parameters for the best-fitting model varied among regions: the maximum and lower Chl aasymptotes were positively and negatively related to percent regional pasture land use, respectively, and the rate at which chlorophyll increased with TP was negatively related to percent regional wetland cover. Lakes in regions with more pasture fields had higher maximum chlorophyll concentrations at high TP concentrations but lower minimum chlorophyll concentrations at low TP concentrations. Lakes in regions with less wetland cover showed a steeper Chl a—TP relationship than wetland-rich regions. Interpretation of Chl a—TP relationships depends on regional differences, and theory and management based on a monolithic relationship may be inaccurate.
Karimi, Alireza; Navidbakhsh, Mahdi
2014-07-01
There are different stress-strain definitions to measure the mechanical properties of the brain tissue. However, there is no agreement as to which stress-strain definition should be employed to measure the mechanical properties of the brain tissue at both the longitudinal and circumferential directions. It is worth knowing that an optimize stress-strain definition of the brain tissue at different loading directions may have implications for neuronavigation and surgery simulation through haptic devices. This study is aimed to conduct a comparative study on different results are given by the various definitions of stress-strain and to recommend a specific definition when testing brain tissues. Prepared cylindrical samples are excised from the parietal lobes of rats' brains and experimentally tested by applying load on both the longitudinal and circumferential directions. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) are used to determine the elastic modulus, maximum stress and strain. The highest non-linear stress-strain relation is observed for the Almansi-Hamel strain definition and it may overestimate the elastic modulus at different stress definitions at both the longitudinal and circumferential directions. The Green-St. Venant strain definition fails to address the non-linear stress-strain relation using different definitions of stress and triggers an underestimation of the elastic modulus. The results suggest the application of the true stress-true strain definition for characterization of the brain tissues mechanics since it gives more accurate measurements of the tissue's response using the instantaneous values.
The stress-strain behavior of coronary stent struts is size dependent.
Murphy, B P; Savage, P; McHugh, P E; Quinn, D F
2003-06-01
Coronary stents are used to re-establish the vascular lumen and flow conditions within the coronary arteries; the typical thickness of a stent strut is 100 microm, and average grain sizes of approximately 25 microm exist in stainless steel stents. The purpose of this study is to investigate the effect of strut size on the stress strain behavior of 316 L stainless steel. Other materials have shown a size dependence at the micron size scale; however, at present there are no studies that show a material property size dependence in coronary stents. Electropolished stainless steel stent struts within the size range of 60-500 microm were tensile tested. The results showed that within the size range of coronary stent struts a size dependent stress-strain relationship is required to describe the material. Finite element models of the final phase of fracture, i.e., void growth models, explained partially the reason for this size effect. This study demonstrated that a size based stress-strain relationship must be used to describe the tensile behavior material of 316 L stainless steel at the size scale of coronary stent struts.
Structure/property relationships in non-linear optical materials
Energy Technology Data Exchange (ETDEWEB)
Cole, J.M. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)]|[Durham Univ. (United Kingdom); Howard, J.A.K. [Durham Univ. (United Kingdom); McIntyre, G.J. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)
1997-04-01
The application of neutrons to the study of structure/property relationships in organic non-linear optical materials (NLOs) is described. In particular, charge-transfer effects and intermolecular interactions are investigated. Charge-transfer effects are studied by charge-density analysis and an example of one such investigation is given. The study of intermolecular interactions concentrates on the effects of hydrogen-bonding and an example is given of two structurally similar molecules with very disparate NLO properties, as a result of different types of hydrogen-bonding. (author). 3 refs.
Evaluation of the stress-strain state of a one-dimensional heterogeneous porous structure
Gerasimov, O.; Shigapova, F.; Konoplev, Yu; Sachenkov, O.
2016-11-01
The paper deals with the problem of determining the stress-strain state of the distal part of the pelvic girdle bones. The area was modeled using a rod loaded by a compressive force and was described by physical relations linking the stress-strain tensor through the elastic constants, the fabric tensor, and the solid volume fraction of the material. Taking into account the law of porosity variation, we considered the problem of evaluating the stress-strain state depending on the nature of the porous structure, and the relationship of the structure with mechanical macroparameters. In this work, we present the results of calculations for a single load, construct the diagrams for the components of the strain tensor, and carry out an assessment of deformations for various system parameters. To evaluate the macroparameters, we built the dependence of the Poisson ratio of the material on the rotation angle a and the pore ellipticity parameter λ. The sensitivity of the deformations to the elastic constants was also estimated.
Confidence bounds for nonlinear dose-response relationships.
Baayen, C; Hougaard, P
2015-11-30
An important aim of drug trials is to characterize the dose-response relationship of a new compound. Such a relationship can often be described by a parametric (nonlinear) function that is monotone in dose. If such a model is fitted, it is useful to know the uncertainty of the fitted curve. It is well known that Wald confidence intervals are based on linear approximations and are often unsatisfactory in nonlinear models. Apart from incorrect coverage rates, they can be unreasonable in the sense that the lower confidence limit of the difference to placebo can be negative, even when an overall test shows a significant positive effect. Bootstrap confidence intervals solve many of the problems of the Wald confidence intervals but are computationally intensive and prone to undercoverage for small sample sizes. In this work, we propose a profile likelihood approach to compute confidence intervals for the dose-response curve. These confidence bounds have better coverage than Wald intervals and are more precise and generally faster than bootstrap methods. Moreover, if monotonicity is assumed, the profile likelihood approach takes this automatically into account. The approach is illustrated using a public dataset and simulations based on the Emax and sigmoid Emax models. Copyright © 2015 John Wiley & Sons, Ltd.
Towards modelling of human relationships:nonlinear dynamical systems in relationships
Safarov, I. (Ildar)
2009-01-01
Abstract This study fills an urgent need for qualitative analyses of relationships resulting in human change. It is a result of sixteen years of independent study by the author. It combines postgraduate study of nonlinear methodology, applied research of children’s pretend play, experience in educational psychology and Gestalt-counselling, as well as the practical training of graduate students at the Karelian State Pedagogical University (Petrozavodsk, Russia), and the Kajaani Department ...
Progress Report on Alloy 617 Isochronous Stress-Strain Curves
Energy Technology Data Exchange (ETDEWEB)
Jill K. Wright; Richard N. Wright; Nancy J. Lybeck
2014-03-01
Isochronous stress-strain curves for Alloy 617 up to a temperature of 1000°C will be required to qualify the material for elevated temperature design in Section III, Division 1, Subsection NH of the ASME Boiler and Pressure Vessel Code. Several potential methods for developing these curves are reviewed in this report. It is shown that in general power-law creep is the rate controlling deformation mechanism for a wide range of alloy heats, test temperatures and stresses. Measurement of the strain rate sensitivity of Alloy 617 indicates that the material is highly strain rate sensitive in the tensile deformation range above about 750°C. This suggests that the concept of a hot tensile curve as a bounding case on the isochronous stress-strain diagrams is problematic. The impact of strain rate on the hot tensile curves is examined and it is concluded that incorporating such a curve is only meaningful if a single tensile strain rate (typically the ASTM standard rate of 0.5%/min) is arbitrarily defined. Current experimentally determined creep data are compared to isochronous stress-strain curves proposed previously by the German programs in the 1980s and by the 1990 draft ASME Code Case. Variability in how well the experimental data are represented by the proposed design curves that suggests further analysis is necessary prior to completing a new draft Code Case.
Spherical nanoindentation stress-strain analysis, Version 1
Energy Technology Data Exchange (ETDEWEB)
2016-11-07
Nanoindentation is a tool that allows the mechanical response of a variety of materials at the nano to micron length scale to be measured. Recent advances in spherical nanoindentation techniques have allowed for a more reliable and meaningful characterization of the mechanical response from nanoindentation experiments in the form on an indentation stress-strain curve. This code base, Spin, is written in MATLAB (The Mathworks, Inc.) and based on the analysis protocols developed by S.R. Kalidindi and S. Pathak [1, 2]. The inputs include the displacement, load, harmonic contact stiffness, harmonic displacement, and harmonic load from spherical nanoindentation tests in the form of an Excel (Microsoft) spreadsheet. The outputs include indentation stress-strain curves and indentation properties as well their variance due to the uncertainty of the zero-point correction in the form of MATLAB data (.mat) and figures (.png). [1] S. Pathak, S.R. Kalidindi. Spherical nanoindentation stress–strain curves, Mater. Sci. Eng R-Rep 91 (2015). [2] S.R. Kalidindi, S. Pathak. Determination of the effective zero-point and the extraction of spherical nanoindentation stress-strain curves, Acta Materialia 56 (2008) 3523-3532.
Correlation between ultrasonic nonlinearity and elastic nonlinearity in heat-treated aluminum alloy
Energy Technology Data Exchange (ETDEWEB)
Kim, Jong Beom; Jhang, Kyung Young [Hanyang University, Seoul (Korea, Republic of)
2017-04-15
The nonlinear ultrasonic technique is a potential nondestructive method to evaluate material degradation, in which the ultrasonic nonlinearity parameter is usually measured. The ultrasonic nonlinearity parameter is defined by the elastic nonlinearity coefficients of the nonlinear Hooke’s equation. Therefore, even though the ultrasonic nonlinearity parameter is not equal to the elastic nonlinearity parameter, they have a close relationship. However, there has been no experimental verification of the relationship between the ultrasonic and elastic nonlinearity parameters. In this study, the relationship is experimentally verified for a heat-treated aluminum alloy. Specimens of the aluminum alloy were heat-treated at 300°C for different periods of time (0, 1, 2, 5, 10, 20, and 50 h). The relative ultrasonic nonlinearity parameter of each specimen was then measured, and the elastic nonlinearity parameter was determined by fitting the stress-strain curve obtained from a tensile test to the 5th-order-polynomial nonlinear Hooke’s equation. The results showed that the variations in these parameters were in good agreement with each other.
Experimental stress-strain analysis of tapered silica optical fibers with nanofiber waist
Holleis, Sigrid; Wuttke, Christian; Schneeweiss, Philipp; Rauschenbeutel, Arno
2014-01-01
We experimentally determine tensile force-elongation diagrams of tapered optical fibers with a nanofiber waist. The tapered optical fibers are produced from standard silica optical fibers using a heat and pull process. Both, the force-elongation data and scanning electron microscope images of the rupture points indicate a brittle material. Despite the small waist radii of only a few hundred nanometers, our experimental data can be fully explained by a nonlinear stress-strain model that relies on material properties of macroscopic silica optical fibers. This is an important asset when it comes to designing miniaturized optical elements as one can rely on the well-founded material characteristics of standard optical fibers. Based on this understanding, we demonstrate a simple and non-destructive technique that allows us to determine the waist radius of the tapered optical fiber. We find excellent agreement with independent scanning electron microscope measurements of the waist radius.
Pastor-Abia, L.; Caturla, M. J.; Sanfabián, E.; Chiappe, G.; Louis, E.
2008-10-01
The engineering stress-strain curves of aluminum nanowires have been investigated by means of molecular dynamics. Nanowires were stretched at constant strain rate and at a temperature of 4.2 K. Atoms at fixed positions with velocities randomly distributed according to Maxwell distribution were taken as initial conditions. Averaging over at least 1500 realizations allows the conclusion that, beyond the yield point, the system does not harden, in line with experimental results for larger nanowires of gold measured at room temperature. Fluctuations of the heat exchanged in the nonlinear regime have been investigated by analyzing around 1.5 million data. The results indicate the presence of non-Gaussian tails in the heat probability distribution.
Undirected learning styles and academic risk: Analysis of the impact of stress, strain and coping.
Kimatian, Stephen; Lloyd, Sara; Berger, Jeffrey; Steiner, Lorraine; McKay, Robert; Schwengal, Deborah
2017-01-01
Learning style inventories used in conjunction with a measure of academic achievement consistently show an association of meaning directed learning patterns with academic success, but have failed to show a clear association of undirected learning styles with academic failure. Using survey methods with anesthesia residents, this study questioned whether additional assessment of factors related to stress, strain, and coping help to better define the association between undirected learning styles and academic risk. Pearson chi squared tests. 296 subjects were enrolled from eight institutions with 142 (48%) completing the study. American Board of Anesthesiologists In Training Examinations (ITE) percentiles (ITE%) were used as a measure of academic achievement. The Vermunt Inventory of Learning Styles (ILS) was used to identify four learning patterns and 20 strategies, and the Osipow Stress Inventory-Revised (OSI-R) was used as a measure of six scales of occupational stress, four of personal strain, and four coping resources. Two learning patterns had significant relationship with ITE scores. As seen in previous studies, Meaning Directed Learning was beneficial for academic achievement while Undirected Learning was the least beneficial. Higher scores on Meaning Directed Learning correlated positively with higher ITE scores while higher Undirected and lower Meaning Directed patterns related negatively to ITE%. OSI-R measures of stress, strain and coping indicated that residents with Undirected learning patterns had higher scores on three scales related to stress, and 4 related to strain, while displaying lower scores on two scales related to coping. Residents with higher Meaning Directed patterns scored lower on two scales of stress and two scales of strain, with higher scores on two scales for coping resources. Low Meaning Directed and high Undirected learning patterns correlated with lower ITE percentiles, higher scores for stress and strain, and lower coping resources
Relationships between nonlinear normal modes and response to random inputs
Schoneman, Joseph D.; Allen, Matthew S.; Kuether, Robert J.
2017-02-01
The ability to model nonlinear structures subject to random excitation is of key importance in designing hypersonic aircraft and other advanced aerospace vehicles. When a structure is linear, superposition can be used to construct its response to a known spectrum in terms of its linear modes. Superposition does not hold for a nonlinear system, but several works have shown that a system's dynamics can still be understood qualitatively in terms of its nonlinear normal modes (NNMs). This work investigates the connection between a structure's undamped nonlinear normal modes and the spectrum of its response to high amplitude random forcing. Two examples are investigated: a spring-mass system and a clamped-clamped beam modeled within a geometrically nonlinear finite element package. In both cases, an intimate connection is observed between the smeared peaks in the response spectrum and the frequency-energy dependence of the nonlinear normal modes. In order to understand the role of coupling between the underlying linear modes, reduced order models with and without modal coupling terms are used to separate the effect of each NNM's backbone from the nonlinear couplings that give rise to internal resonances. In the cases shown here, uncoupled, single-degree-of-freedom nonlinear models are found to predict major features in the response with reasonable accuracy; a highly inexpensive approximation such as this could be useful in design and optimization studies. More importantly, the results show that a reduced order model can be expected to give accurate results only if it is also capable of accurately predicting the frequency-energy dependence of the nonlinear modes that are excited.
Stress-strain analysis of pipelines laid in permafrost
Burkov, P.; Yan‘nan', Van; Burkova, S.
2016-09-01
Increasing reliability of pipelines becomes a real challenge at all stages: design, construction and operation of pipeline systems. It is very important to determine the behaviour of the constructed pipeline under the operational and environmental loads using the design model in accordance with that one adopted in the rules and regulations. This article presents the simulation of pipeline in permafrost. The evaluation of the stress-strain state is given herein and the areas of the stress concentration are detected with the account for different loads occurred during the pipeline operation. Information obtained from the assessment of the stress-strain state of the pipeline allows determining sections in pre-emergency state (even before damages) and take all the necessary measures for eliminating them, thus increasing the pipeline system reliability. It is shown that the most critical pipeline cross-section is observed at the point of transition from one environment to another. The maximum strains decrease the level of the pipeline reliability. The finite element model is presented to determine the pipeline sections in pre-emergency state.
Structure property relationships for the nonlinear optical response of fullerenes
Rustagi, Kailash C.; Ramaniah, Lavanya M.; Nair, Selvakumar V.
1994-11-01
We present a phenomenological theory of nonlinear optical response of fullerenes. An empirical tight-binding model is used in conjunction with a classical electromagnetic picture for the screening. Since in bulk media such a picture of screening corresponds to the self- consistent field approach, the only additional approximation involved in our approach is the neglect of nonlocality. We obtain reliable estimates for the linear and nonlinear susceptibilities of C60, C70, C76 and other pure carbon fullerenes and also substituted fullerenes. The relatively large values of (beta) that we obtain for C76 and substituted fullerenes appear promising for the development of fullerene-based nonlinear optical materials. Our phenomenological picture of screening provides a good understanding of the linear absorption spectra of higher fullerenes and predicts that a comparison of the one-photon and multi-photon spectra will provide an insight into screening effects in these systems.
Stress-strain behavior of cementitious materials with different sizes.
Zhou, Jikai; Qian, Pingping; Chen, Xudong
2014-01-01
The size dependence of flexural properties of cement mortar and concrete beams is investigated. Bazant's size effect law and modified size effect law by Kim and Eo give a very good fit to the flexural strength of both cement mortar and concrete. As observed in the test results, a strong size effect in flexural strength is found in cement mortar than in concrete. A modification has been suggested to Li's equation for describing the stress-strain curve of cement mortar and concrete by incorporating two different correction factors, the factors contained in the modified equation being established empirically as a function of specimen size. A comparison of the predictions of this equation with test data generated in this study shows good agreement.
Materials property testing using a stress-strain microprobe
Energy Technology Data Exchange (ETDEWEB)
Panayotou, N.F.; Baldrey, D.G. [Lockheed Martin Corp., Schenectady, NY (United States); Haggag, F.M. [Advanced Technology Corp., Oak Ridge, TN (United States)
1998-09-01
The Stress-Strain Microprobe (SSM) uses an automated ball indentation technique to obtain flow data from a localized region of a test specimen or component. This technique is used to rapidly determine the yield strength and microstructural condition of a variety of materials including pressure vessel steels, stainless steels, and nickel-base alloys. The SSM provides an essentially non-destructive technique for the measurement of yield strength data. This technique is especially suitable for the study of complex or highly variable microstructures such as weldments and weld heat affected zones. In this study 119 distinct SSM determinations of the yield strength of eight engineering alloys are discussed and compared to data obtained by conventional tensile tests. The sensitivity of the SSM to the presence of residual stresses is also discussed.
Origins of asymmetric stress-strain response in phase transformations
Energy Technology Data Exchange (ETDEWEB)
Sehitoglu, H.; Gall, K. [Univ. of Illinois, Urbana, IL (United States)
1997-12-31
It has been determined that the transformation stress-strain behavior of CuZnAl and NiTi shape memory alloys is dependent on the applied stress state. The uniaxial compressive stress necessary to macroscopically trigger the transformation is approximately 34% (CuZnAl) and 26% (NiTi) larger than the required uniaxial tensile stress. For three dimensional stress states, the response of either alloy system is dependent on the directions of the dominant principal stresses along with the hydrostatic stress component of the stress state. The stress state effects are dominated by the favored growth and nucleation of more martensite plates in tension versus compression. The effect of different hydrostatic pressure levels between stress states on martensite plates volume change is considered small.
Modeling the Stress Strain Behavior of Woven Ceramic Matrix Composites
Morscher, Gregory N.
2006-01-01
Woven SiC fiber reinforced SiC matrix composites represent one of the most mature composite systems to date. Future components fabricated out of these woven ceramic matrix composites are expected to vary in shape, curvature, architecture, and thickness. The design of future components using woven ceramic matrix composites necessitates a modeling approach that can account for these variations which are physically controlled by local constituent contents and architecture. Research over the years supported primarily by NASA Glenn Research Center has led to the development of simple mechanistic-based models that can describe the entire stress-strain curve for composite systems fabricated with chemical vapor infiltrated matrices and melt-infiltrated matrices for a wide range of constituent content and architecture. Several examples will be presented that demonstrate the approach to modeling which incorporates a thorough understanding of the stress-dependent matrix cracking properties of the composite system.
Stress-strain response of plastic waste mixed soil.
Babu, G L Sivakumar; Chouksey, Sandeep Kumar
2011-03-01
Recycling plastic waste from water bottles has become one of the major challenges worldwide. The present study provides an approach for the use plastic waste as reinforcement material in soil. The experimental results in the form of stress-strain-pore water pressure response are presented. Based on experimental test results, it is observed that the strength of soil is improved and compressibility reduced significantly with addition of a small percentage of plastic waste to the soil. The use of the improvement in strength and compressibility response due to inclusion of plastic waste can be advantageously used in bearing capacity improvement and settlement reduction in the design of shallow foundations. Copyright © 2010 Elsevier Ltd. All rights reserved.
Soil Stress-Strain Behavior: Measurement, Modeling and Analysis
Ling, Hoe I; Leshchinsky, Dov; Koseki, Junichi; A Collection of Papers of the Geotechnical Symposium in Rome
2007-01-01
This book is an outgrowth of the proceedings for the Geotechnical Symposium in Roma, which was held on March 16 and 17, 2006 in Rome, Italy. The Symposium was organized to celebrate the 60th birthday of Prof. Tatsuoka as well as honoring his research achievement. The publications are focused on the recent developments in the stress-strain behavior of geomaterials, with an emphasis on laboratory measurements, soil constitutive modeling and behavior of soil structures (such as reinforced soils, piles and slopes). The latest advancement in the field, such as the rate effect and dynamic behavior of both clay and sand, behavior of modified soils and soil mixtures, and soil liquefaction are addressed. A special keynote paper by Prof. Tatsuoka is included with three other keynote papers (presented by Prof. Lo Presti, Prof. Di Benedetto, and Prof. Shibuya).
Morphology and stress-strain properties along the small intestine in the rat.
Dou, Yanling; Zhao, Jingbo; Gregersen, Hans
2003-04-01
The stress-strain relationship is determined by the inherent mechanical properties of the intestinal wall, the geometric configurations, the loading conditions and the zero-stress state of the segment. The purpose of this project was to provide morphometric and biomechanical data for rat duodenum, jejunum and ileum. The circumferential strains were referenced to the zero-stress state. Large morphometric variations were found along the small intestine with an increase in the outer circumferential length and luminal area and a decrease in wall thickness in distal direction. The serosal residual strain was tensile and decreased in distal direction (P small intestine. The zero-stress state must be considered in future biomechanical studies in the gastrointestinal tract.
Nonlinear elastic behavior of phantom materials for elastography
Energy Technology Data Exchange (ETDEWEB)
Pavan, Theo Z; Madsen, Ernest L; Frank, Gary R; Hall, Timothy J [Medical Physics Department, University of Wisconsin, Room 1005, Wisconsin Institutes for Medical Research, 1111 Highland Avenue, Madison, WI 53705 (United States); Adilton O Carneiro, Antonio, E-mail: tjhall@wisc.ed [Departamento de Fisica e Matematica, FFCLRP, Universidade de Sao Paulo, Av. Bandeirantes, 3900, Monte Alegre, Ribeirao Preto, Sao Paulo (Brazil)
2010-05-07
The development of phantom materials for elasticity imaging is reported in this paper. These materials were specifically designed to provide nonlinear stress/strain relationship that can be controlled independently of the small strain shear modulus of the material. The materials are mixtures of agar and gelatin gels. Oil droplet dispersions in these materials provide further control of the small strain shear modulus and the nonlinear parameter of the material. Since these materials are mostly water, they are assumed to be incompressible under typical experimental conditions in elasticity imaging. The Veronda-Westman model for strain energy density provided a good fit to all materials used in this study. Materials with a constant gelatin concentration (3.0% dry weight) but varying agar concentration (0.6-2.8% dry weight) demonstrated the same power law relationship between elastic modulus and agar concentration found for pure agar (1.89 {+-} 0.02), consistent with percolation theory, and provided a consistent nonlinearity parameter of 4.5 {+-} 0.3. The insights provided by this study will form the basis for stable elastography phantoms with stiffness and nonlinear stress/strain relationships in the background that differ from those in the target.
Stress-strain relations for swelling anhydritic clay rocks – A review
Breuer, Simon; Blum, Philipp; Butscher, Christoph
2015-04-01
The swelling of clay-sulfate rocks is a major threat in tunnel engineering, causing serious damage to tunnels and producing high additional costs during tunnel construction and operation. The swelling leads to geomechanical processes that may result in heave of the tunnel invert, destruction of the lining or uplift of the entire tunnel section. Heave-pressure-time relations are needed when predictions should be made about the mechanical behavior of swelling rock. For pure clay rocks, there is a linear relation between the swelling heave (strain) and the logarithm of pressure (Grob 1972). A generally accepted relation for clay-sulfate rocks, however, is still lacking to date. Therefore, finding appropriate and sustainable counter measures for an actual tunneling project affected by swelling remains extremely difficult. Grob (1972) proposed the linear relation between heave and the logarithm of pressure ("semi-logarithmic swelling law") not only for clay rocks, but also for clay-sulfate rocks. Pimentel (2007), however, presented laboratory experiments indicating that the semi-logarithmic swelling law may be inadequate for describing the swelling of clay-sulfate rocks. The laboratory tests revealed three different stages in the swelling process, including minimal deformation and prevented gypsum crystallization at high pressures (> 6 MPa); large deformation and gypsum crystallization at medium pressures; and only small deformation, possibly along with gypsum dissolution, at low pressures (water inflow into the rock, which cannot be reflected by general strain-stress relations. The present study critically reviews stress-strain relations for swelling anhydritic clay rocks proposed by various authors. Subsequently, published laboratory data from oedometric swelling tests are presented that may confirm the proposed stress-strain relationships. Finally, these data are re-examined by comparing each of the proposed relations with the same data set. Based on these results, a
Energy Technology Data Exchange (ETDEWEB)
Bekiros, Stelios D.; Diks, Cees G.H. [Center for Nonlinear Dynamics in Economics and Finance (CeNDEF), Department of Quantitative Economics, University of Amsterdam, Roetersstraat 11, 1018 WB Amsterdam (Netherlands)
2008-09-15
The present study investigates the linear and nonlinear causal linkages between daily spot and futures prices for maturities of one, two, three and four months of West Texas Intermediate (WTI) crude oil. The data cover two periods October 1991-October 1999 and November 1999-October 2007, with the latter being significantly more turbulent. Apart from the conventional linear Granger test we apply a new nonparametric test for nonlinear causality by Diks and Panchenko after controlling for cointegration. In addition to the traditional pairwise analysis, we test for causality while correcting for the effects of the other variables. To check if any of the observed causality is strictly nonlinear in nature, we also examine the nonlinear causal relationships of VECM filtered residuals. Finally, we investigate the hypothesis of nonlinear non-causality after controlling for conditional heteroskedasticity in the data using a GARCH-BEKK model. Whilst the linear causal relationships disappear after VECM cointegration filtering, nonlinear causal linkages in some cases persist even after GARCH filtering in both periods. This indicates that spot and futures returns may exhibit asymmetric GARCH effects and/or statistically significant higher order conditional moments. Moreover, the results imply that if nonlinear effects are accounted for, neither market leads or lags the other consistently, videlicet the pattern of leads and lags changes over time. (author)
Analysis of Mechanical Stresses/Strains in Superconducting Wire
Barry, Matthew; Chen, Jingping; Zhai, Yuhu
2016-10-01
The optimization of superconducting magnet performance and development of high-field superconducting magnets will greatly impact the next generation of fusion devices. A successful magnet development, however, relies deeply on the understanding of superconducting materials. Among the numerous factors that impact a superconductor's performance, mechanical stress is the most important because of the extreme operation temperature and large electromagnetic forces. In this study, mechanical theory is used to calculate the stresses/strains in typical superconducting strands, which consist of a stabilizer, a barrier, a matrix and superconducting filaments. Both thermal loads and mechanical loads are included in the analysis to simulate operation conditions. Because this model simulates the typical architecture of major superconducting materials, such as Nb3Sn, MgB2, Bi-2212 etc., it provides a good overall picture for us to understand the behavior of these superconductors in terms of thermal and mechanical loads. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.
Confidence bounds for nonlinear dose-response relationships
DEFF Research Database (Denmark)
Baayen, C; Hougaard, P
2015-01-01
. It is well known that Wald confidence intervals are based on linear approximations and are often unsatisfactory in nonlinear models. Apart from incorrect coverage rates, they can be unreasonable in the sense that the lower confidence limit of the difference to placebo can be negative, even when an overall...... test shows a significant positive effect. Bootstrap confidence intervals solve many of the problems of the Wald confidence intervals but are computationally intensive and prone to undercoverage for small sample sizes. In this work, we propose a profile likelihood approach to compute confidence...... intervals for the dose-response curve. These confidence bounds have better coverage than Wald intervals and are more precise and generally faster than bootstrap methods. Moreover, if monotonicity is assumed, the profile likelihood approach takes this automatically into account. The approach is illustrated...
Ikeshita, Kazuki; Hasegawa, Hideyuki; Kanai, Hiroshi
2008-05-01
The endothelial dysfunction is considered to be an initial step of atherosclerosis. Additionally, it was reported that the smooth muscle, which constructs the media of the artery, changes its characteristics owing to atherosclerosis. Therefore, it is essential to develop a method for assessing the regional endothelial function and mechanical property of the arterial wall. There is a conventional technique of measuring the transient change in the diameter of the brachial artery caused by flow-mediated dilation (FMD) after the release of avascularization. For more sensitive and regional evaluation, we developed a method of measuring the change in the elasticity of the radial artery due to FMD. In this study, the transient change in the mechanical property of the arterial wall was further revealed by measuring the stress-strain relationship during each heartbeat. The minute change in the thickness (strain) of the radial arterial wall during a cardiac cycle was measured by the phased tracking method, together with the waveform of blood pressure which was continuously measured with a sphygmometer at the radial artery. The transient change in stress-strain relationship during a cardiac cycle was obtained from the measured changes in wall thickness and blood pressure to show the transient change in instantaneous viscoelasticity. From the in vivo experimental results, the stress-strain relationship shows the hysteresis loop. The slope of the loop decreased owing to FMD, which shows that the elastic modulus decreased, and the increasing area of the loop depends on the ratio of the loss modulus (depends on viscosity) to the elastic modulus when the Voigt model is assumed. These results show a potential of the proposed method for the thorough analysis of the transient change in viscoelasticity due to FMD.
Mulder, Herman A; Hill, William G; Knol, Egbert F
2015-04-01
There is recent evidence from laboratory experiments and analysis of livestock populations that not only the phenotype itself, but also its environmental variance, is under genetic control. Little is known about the relationships between the environmental variance of one trait and mean levels of other traits, however. A genetic covariance between these is expected to lead to nonlinearity between them, for example between birth weight and survival of piglets, where animals of extreme weights have lower survival. The objectives were to derive this nonlinear relationship analytically using multiple regression and apply it to data on piglet birth weight and survival. This study provides a framework to study such nonlinear relationships caused by genetic covariance of environmental variance of one trait and the mean of the other. It is shown that positions of phenotypic and genetic optima may differ and that genetic relationships are likely to be more curvilinear than phenotypic relationships, dependent mainly on the environmental correlation between these traits. Genetic correlations may change if the population means change relative to the optimal phenotypes. Data of piglet birth weight and survival show that the presence of nonlinearity can be partly explained by the genetic covariance between environmental variance of birth weight and survival. The framework developed can be used to assess effects of artificial and natural selection on means and variances of traits and the statistical method presented can be used to estimate trade-offs between environmental variance of one trait and mean levels of others. Copyright © 2015 by the Genetics Society of America.
Nonlinear relationships between individual IEQ factors and overall workspace satisfaction
Kim, Jungsoo; Dear,Richard de
2011-01-01
Despite a paucity of rigorous scientific evidence causally linking Indoor Environmental Quality (IEQ) issues to office occupants’ productivity, there is a widespread belief that such causality exists; excellent or poor IEQ translate into productivity gains or losses respectively. The aim of this study is to better understand relationship between perceived building performance on specific IEQ factors and occupants’ overall satisfaction with their workspace. Kano’s satisfaction model, developed...
On the relationship between nonlinear and linear differential systems
Directory of Open Access Journals (Sweden)
ZHOU Zhengxin
2015-06-01
Full Text Available In this article, we establish the relationship between the quadratic time-varying differential systems and the linear systems, giving the sufficient conditions for the quadratic systems to have the reflecting function in the form of fractional function. We use the obtained results to discuss the qualitative behavior of the solutions of the quadratic differential systems and the time-varying Kolmogrov equations.
Institute of Scientific and Technical Information of China (English)
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.
QUANTITATIVE CHARACTERIZATION OF STRESS-STRAIN HYSTERESIS LOOPS OF Cu-Zn-Al SHAPE MEMORY ALLOY
Institute of Scientific and Technical Information of China (English)
Y.F. Guo; Y.Z. Huo; G.T. Zeng; X.T. Zu
2001-01-01
A six-parameter mathematical model was introduced to simulate the stress-strain hysteresis and the inner hysteresis of polycrystalline shape memory alloys (SMAs). By comparing with experiments of Cu-Zn-Al SMA, it was shown that the model could be used to calculate the stress-strain relations with rather good accuracy. Moreover,it was found that the six parameters introduced in this paper represented the characteristics of the stress-strain hysteresis of polycrystalline SMA and can be used to characterize the hysteresis quantitatively.
Remarks on the relationship between ℒp stability and internal stability of nonlinear systems
Wang, Xu; Grip, H°avard Fjær; Saberi, Ali A.; Stoorvogel, Anton A.; Saberi, Ingmar
2013-01-01
In this paper, we investigate the relationship between ℒp stability and internal stability of nonlinear systems. It is shown that under certain conditions, ℒp stability without finite gain implies attractivity of the equilibrium, and that local ℒp stability with finite gain implies local asymptotic
Remarks on the relationship between ℒp stability and internal stability of nonlinear systems
Wang, Xu; Grip, H°avard Fjær; Saberi, Ali; Stoorvogel, Anton A.; Saberi, Ingmar
2011-01-01
In this paper, we investigate the relationship between ℒp stability and internal stability of nonlinear systems. It is shown that under certain conditions, ℒp stability without finite gain implies attractivity of the equilibrium, and that local ℒp stability with finite gain implies local asymptotic
Is the investment-uncertainty relationship nonlinear? An empirical analysis for the Netherlands
Bo, H; Lensin, R
We examine the investment-uncertainty relationship for a panel of Dutch non-financial firms. The system generalized method of moments (GMM) estimates suggest that the effect of uncertainty on investment is nonlinear: for low levels of uncertainty an increase in uncertainty has a positive effect on
Correction of the post -- necking true stress -- strain data using instrumented nanoindentation
Romero Fonseca, Ivan Dario
The study of large plastic deformations has been the focus of numerous studies particularly in the metal forming processes and fracture mechanics fields. A good understanding of the plastic flow properties of metallic alloys and the true stresses and true strains induced during plastic deformation is crucial to optimize the aforementioned processes, and to predict ductile failure in fracture mechanics analyzes. Knowledge of stresses and strains is extracted from the true stress-strain curve of the material from the uniaxial tensile test. In addition, stress triaxiality is manifested by the neck developed during the last stage of a tensile test performed on a ductile material. This necking phenomenon is the factor responsible for deviating from uniaxial state into a triaxial one, then, providing an inaccurate description of the material's behavior after the onset of necking. The research of this dissertation is aimed at the development of a correction method for the nonuniform plastic deformation (post-necking) portion of the true stress-strain curve. The correction proposed is based on the well-known relationship between hardness and flow (yield) stress, except that instrumented nanoindentation hardness is utilized rather than conventional macro or micro hardness. Three metals with different combinations of strain hardening behavior and crystal structure were subjected to quasi-static tensile tests: power-law strain hardening low carbon G10180 steel (BCC) and electrolytic tough pitch copper C11000 (FCC), and linear strain hardening austenitic stainless steel S30400 (FCC). Nanoindentation hardness values, measured on the broken tensile specimen, were converted into flow stress values by means of the constraint factor C from Tabor's, the representative plastic strainepsilonr and the post-test true plastic strains measured. Micro Vickers hardness testing was carried out on the sample as well. The constraint factors were 5.5, 4.5 and 4.5 and the representative plastic
Fractal approximation of the stress-strain curve of frozen soil
Institute of Scientific and Technical Information of China (English)
令锋; 吴紫汪; 朱元林; 何春雄; 朱林楠
1999-01-01
A method to approach the stress-strain curve of frozen soil is presented based on the fact that the stressstrain curve of frozen soil has fractal property. First, a linear hyperbolic iterated function system (LHIFS) in which the perpendicular contraction factors are regarded as parameters is established using fractal geometry theories. Secondly, a method to calculate the best point which makes the attractor of the LHIFS an optimal approximation of the stress-strain curve of frozen soil is presented. Then, a method for calculating the fractal dimension of the stress-strain curve of frozen soil is obtained. Finally, a simple example is provided. The method presented in this paper provides a new method for simulating the stress-strain curve and calculating its fractal dimension of geomaterials that have the fractal feature by using computer.
Rate dependent rheological stress-strain behavior of porous nanocrystalline materials
Institute of Scientific and Technical Information of China (English)
李慧; 周剑秋
2008-01-01
To completely understand the rate-dependent stress-strain behavior of the porous nanocrystalline materials,it is necessary to formulate a constitutive model that can reflect the complicated experimentally observed stress-strain relations of nanocrystalline materials.The nanocrystalline materials consisting grain interior and grain boundary are considered as viscoplastic and porous materials for the reasons that their mechanical deformation is commonly governed by both dislocation glide and diffusion,and pores commonly exist in the nanocrystalline materials.A constitutive law of the unified theory reflecting the stress-strain relations was established and verified by experimental data of bulk nanocrystalline Ni prepared by hydrogen direct current arc plasma evaporation method and hot compression.The effect of the evolution of porosity on stress-strain relations was taken into account to make that the predicted results can keep good agreements with the corresponding experimental results.
The Non-Linear Relationship Between Fiscal Deficits And Inflation: Evidence From Africa
Directory of Open Access Journals (Sweden)
Abu Nurudeen
2015-12-01
Full Text Available Although, there is abundant research on the fiscal deficit-inflation relationship, little has been done to investigate the non-linear association between them, particularly in Africa. This study employs fixed-effects and GMM estimators to examine the non-linear relationship between deficits and inflation from 1999 to 2011 in 51 African economies, which are further grouped into high-inflation/low-income countries and moderate-inflation/middle-income countries. The results indicate that the deficit-inflation relationship is non-linear for the whole sample and sub-groups. For the whole sample, a percentage point increase in deficit results in a 0.25 percentage point increase in inflation rate, while the relationship becomes quantitatively greater once deficits reach 23% of GDP. The subsamples report different relationships. Although our results cannot be used as the base for generalization, we identify importance of grouping African countries according to their levels of inflation and/or income, rather than treating them as a homogeneous entity.
MODELLING FOR THE STRESS-STRAIN BEHAVIOR OF ANISOTROPICALLY LIGHTLY OVERCONSOLIDATED CLAY
木幡, 行宏; 三田地, 利之
1989-01-01
A series of drained stress probe test on saturated remoulded clay specimens consolidated and rebounded under anisotropic stress condition was performed to investigate the influence of anisotropic stress history and stress path on the stress-strain behavior of clay. Based on the test results, a new constitutive model was proposed which could successfully describe the stress-strain behavior of anisotropically lightly overconsolidated clay.
A COMPUTER PROGRAMME FOR THE NON-LINEAR ANALYSIS OF COMPLETE STRUCTURES
Directory of Open Access Journals (Sweden)
Turgay ÇOŞGUN
2003-02-01
Full Text Available The progress made on the analysis of the structures by using non-linear theory and the significant findings on both theorical and empirical works, enable better understanding of the behaviours of structures under external loads. Determination of the failure load and designing the structures accordingly requires developments of analysis methods, which take both the non-linear behaviour of structural elements and the non-linear effects of geometric changes into consideration. Therefore, in this study, a FORTRAN code, which analyses structures and calculates the failure loads by considering the non-linear behaviour of materials under increasing loads (due to the non-linear relationship of stress-strain and moment-curvature and second-order theory of structural systems is developed.
True stress-strain curves of cold worked stainless steel over a large range of strains
Kamaya, Masayuki; Kawakubo, Masahiro
2014-08-01
True stress-strain curves for cold worked stainless steel were obtained over a range of strains that included a large strain exceeding the strain for the tensile strength (post-necking strain). A specified testing method was used to obtain the stress-strain curves in air at room temperature. The testing method employed the digital image correlation (DIC) technique and iterative finite element analyses (FEA) and was referred to as IFD (Iteration FEA procedure based on DIC measurement) method. Although hourglass type specimens have been previously used for the IFD method, in this study, plate specimens with a parallel gage section were used to obtain accurate yield and tensile strengths together with the stress-strain curves. The stress-strain curves including the post-necking strain were successfully obtained by the IFD method, and it was shown that the stress-strain curves for different degrees of cold work collapsed onto a single curve when the offset strain was considered. It was also shown that the Swift type constitutive equation gave good regression for the true stress-strain curves including the post-necking strain regardless of the degree of cold work, although the Ramberg-Osgood type constitutive equation showed poor fit. In the regression for the Swift type constitutive equation, the constant for power law could be assumed to be nS = 0.5.
Seepage laws of two kinds of disastrous gas in complete stress-strain process of coal
Institute of Scientific and Technical Information of China (English)
Cao Shugang; Guo Ping; Zhang Zunguo; Li Yi; Wang Yong
2011-01-01
The similarities and differences in seepage flow evolution laws of CH4 and CO2 during complete stressstrain process of samples were comparatively analyzed.The results show that the seepage flow evolution laws of CH4 and CO2 are extremely similar during the stress-strain process,showing that the characteristic first decreased and then increased.A mathematical model was also established according to the relationship of seepage velocity and axial strain.However,due to the strong adsorption ability of CO2,the coal samples generated a more serious “Klinkenberg effect” under the condition of CO2.Owing to this,the CO2 seepage flow resulted into occurrence of “stagnation” phenomenon during the late linear elastic stage Ⅱ.In the strain consolidation stage Ⅲ,the increment rate of CH4 seepage velocity was significantly greater than that of CO2.In the stress descent stage Ⅳ,when the axial load reached the peak pressure of coal,the increment rates of CH4 seepage velocity presented a turning point.But the changing rate of CO2 seepage velocity still remained slow and a turning point was presented at one time after the peak of the strain pressure,which showed an obvious feature of hysteresis.
Gencoglu, Muharrem Tuncay; Baskonus, Haci Mehmet; Bulut, Hasan
2017-01-01
The main aim of this manuscript is to obtain numerical solutions for the nonlinear model of interpersonal relationships with time fractional derivative. The variational iteration method is theoretically implemented and numerically conducted only to yield the desired solutions. Numerical simulations of desired solutions are plotted by using Wolfram Mathematica 9. The authors would like to thank the reviewers for their comments that help improve the manuscript.
Analysis of the stress-strain state of New Exchequer combined damat static loads
Directory of Open Access Journals (Sweden)
Sainov Mikhail Petrovich
Full Text Available In the article the authors analyze numerical modeling results of the stress-strain state of a combined dam created by construction of a higher rockfill dam with a reinforced concrete face behind the downstream face of the concrete dam. The analysis was conducted on the example of the design of 150 meter high New Exchequer dam (USA. Numerical modeling was conducted with consideration of non-linearity of soils deformation as well as non-linear behavior of the interaction “concrete - soil”, “concrete - concrete”. The analysis showed that though in a combined dam the concrete part gets additional displacements and settlements, its stress state remains favorable without appearance of tensile stresses and opening of the contact “concrete - rock”. This is explained by the fact that on the top the concrete dam is weightened by the reservoir hydrostatic pressure. The role of rockfill lateral pressure on the concrete dam stress state is small. There may be expected sliding of soil in relation to the concrete dam downstream face due to the loss of its shear strength. Besides, decompaction of the contact "soil - concrete" may occur, as earthfill will have considerable displacements in the direction from the concrete dam. Due to this fact the loads from the earthfill weight do not actually transfer to the concrete dam. The most critical zone in the combined dam is the interface of the reinforced concrete face with the concrete dam. Under the action of the hydrostatic pressure the earth-fill under the face will have considerable settlements and displacements, because soil slides in relation to the concrete dam downstream face. This results in considerable openings (10 cm and shear displacements (50 сm in the perimeter joint. The results of the numerical modeling are confirmed by the presence of seepage in New Exchequer dam, which led to the necessity of its repair. Large displacements do not allow using traditional sealing like copper water stops
Osamura, Kozo; Kuratani, Fumiyasu; Koide, Toshio; Ogawa, Wataru; Taniguchi, Hiroyasu; Monju, Yoshiyuki; Mizuta, Taiji; Shobu, Takahisa
2016-12-01
The artistic sound of a cymbal is produced by employing a special copper alloy as well as incorporating complicated and heterogeneous residual stress/strain distributions. In order to establish a modern engineering process that achieves high-quality control for the cymbals, it is necessary to investigate the distribution of the residual stresses/strains in the cymbal and their quantitative relation with the frequency characteristics of the sound generated from the cymbal. In the present study, we have successfully used synchrotron radiation to measure the distribution of residual strain in two kinds of cymbals—after spinforming as well as after hammering. The microstructure and the mechanical properties of the cymbals were measured as well their acoustic response. Based on our experimental data, the inhomogeneous residual stress/strain distributions in the cymbals were deduced in detail and their influence on the frequency characteristics of the sound produced by the cymbals was identified.
Directory of Open Access Journals (Sweden)
Jagdev Singh
2017-07-01
Full Text Available In this paper, we propose a new numerical algorithm, namely q-homotopy analysis Sumudu transform method (q-HASTM, to obtain the approximate solution for the nonlinear fractional dynamical model of interpersonal and romantic relationships. The suggested algorithm examines the dynamics of love affairs between couples. The q-HASTM is a creative combination of Sumudu transform technique, q-homotopy analysis method and homotopy polynomials that makes the calculation very easy. To compare the results obtained by using q-HASTM, we solve the same nonlinear problem by Adomian’s decomposition method (ADM. The convergence of the q-HASTM series solution for the model is adapted and controlled by auxiliary parameter ℏ and asymptotic parameter n. The numerical results are demonstrated graphically and in tabular form. The result obtained by employing the proposed scheme reveals that the approach is very accurate, effective, flexible, simple to apply and computationally very nice.
Energy Technology Data Exchange (ETDEWEB)
Hakala, M.; Heikkilae, E. [Helsinki Univ. of Technology, Espoo (Finland). Lab. of Rock Engineering
1997-05-01
This work summarizes the project aimed at developing and qualifying a suitable combination of laboratory tests to establish a statistically reliable stress-strain behaviour of the main rock types at Posiva Oy`s detailed investigation sites for disposal of spent nuclear fuel. The work includes literature study of stress-strain behaviour of brittle rock, development and qualification of laboratory tests, suggested test procedures and interpretation methods and finally testing of Olkiluoto mica gneiss. The Olkiluoto study includes over 130 loading tests. Besides the commonly used laboratory tests, direct tensile tests, damage controlled tests and acoustic emission measurements were also carried out. (orig.) (54 refs.).
Estimation of cyclic stress-strain curves for low-alloy steel from hardness
Directory of Open Access Journals (Sweden)
R. Basan
2010-04-01
Full Text Available This article describes investigations into the existence of correlation between experimentally determined cyclic parameters and hardness of quenched and tempered representative low-alloy steel 42CrMo4. A good correlation was found to exist between cyclic strength coefficient K’ and Brinell hardness HB, but not between cyclic strain hardening exponent n‘ and hardness HB. Nevertheless, good agreement between calculated and experimental cyclic stress-strain curves shows that cyclic parameters i.e. cyclic stress-strain curves of the investigated steel can be successfully estimated from its hardness.
Stress-strain distribution at the boundary area of coal seams containing nonuniformities
Energy Technology Data Exchange (ETDEWEB)
Khaimova-Mal' kova, R.I.
1986-01-01
Discusses results of investigations carried out with the help of the finite element method in a 2 m thick coal seam at 400 m level, having varying properties and nonuniformities. Shows that considerable areas with horizontal deformation appear in soft coal which may result in vertical fissuring parallel to headings. States that presence of soft and hard inclusions in coal seams affect stress-strain state and stability of boundary areas and lead to spasmodic changes in stress-strain intensity which result in dynamic phenomena particularly in coal seams which are prone to sudden gas and coal outbursts. 3 refs.
Cyclic Stress-Strain Studies of Metals in Torsion
1940-12-01
give a uniform stress distribution for th,at part of the specimen .on which the twist uas measured. IQ the cyclic” torsion tests data for a shearing...In the tensile and the, com- pressive tests, strains, were measured, over 2-i.~h g-e leugths usiag the I.larteLnsmirror .= tensometer - ~?hree-iach gage...considered. thus far.., Except foy the ~irst part of the firs”t cz?cle, a li~e~~ relati-onship between shearing stress aad strain was not obtained”. What
Energy Technology Data Exchange (ETDEWEB)
Fahmy M. Haggag
1999-10-29
The results presented in this report demonstrate the capabilities of Advanced Technology Corporation's patented Portable/In Situ Stress-Strain Microprobe (TM) (SSM) System and its Automated Ball Indentation (ABI) test techniques to nondestructively measure the yield strength, the stress-strain curve, and the fracture toughness of ferritic steel samples and components in a reliable and accurate manner.
Stress-strain characteristics of materials at high strain rates. Part II. Experimental results
Energy Technology Data Exchange (ETDEWEB)
Ripperger, E. A. [Texas. Univ., Austin, TX (US). Structural Mechanics Research Lab.
1958-08-29
These two reports were issued separately, but are cataloged as a unit. A photoelectric method for measuring displacements during high-velocity impacts is described. The theory of the system is discussed in detail, and a prototype system which was built and tested is described. The performance of the prototype system is evaluated by comparing the results which it gives with results obtained by other methods of measurement. The system was found capable of a resolution of at least 0.01 inches. static and dynamic stress-strain characteristics of seven high polymers, polyethylene, teflon, nylon, tenite M, tenite H, polystyrene, and saran, plus three metals, lead, copper, and aluminum, are described and compared by means of stress-strain curves and photographs. Data are also presented which show qualitatively the effects produced on stress-strain characteristics by specimen configuration, temperature, and impact velocity. It is shown that there is a definite strain-rate effect for all these materials except polystyrene. The effect is one of an apparent stiffening of the material with increasing strain rate, which is similar to the effect produced by lowering the temperature. The stress-strain measurements are examined critically, inconsistencies are pointed out, and possible sources of error suggested. Values of yield stress, modulus of elasticity and energy absorption for all materials (except copper and aluminum), specimen configurations, temperatures, and impact velocities included in the investigation are tabulated.
Influence of discontinuities on the rock mass stress-strain state around excavation
Directory of Open Access Journals (Sweden)
V.N. Bukhartsev
2013-06-01
Full Text Available Adequate mathematical modeling of selvage zone and natural fracturing as well as assessment of its impact on stress-strain state – urgent problems in calculation of hydraulic tunnels. Modern Russian regulations in fact give dependences only to solve the problems in plane deformation conditions. The specificity of work of the tunnel that crosses the discontinuity, as a space frame are not taken into account. This article presents influence of discontinuities and fracture characteristics on the rock mass stress-strain state around excavation. Fractured rock mass model was analyzed. Formula of modulus of elasticity for fractured rock mass at distance from the fault was deduced. Influence of discontinuities on the stress distribution was estimated with using experiment design method. On the basis of the conducted research it was established, that assessing rock stress-strain state around the fracture is necessary to consider rock mass fracture characteristics; and using principal stresses distribution in combination with Lode parameter we can clearly estimate the type of stress-strain state in each point, therefore, we can use different strength theories for different sections of the tunnel.
Stress-strain-sorption behaviour of coal matrix material exposed to CO2
Hol, S.
2011-01-01
Coal swells when it adsorbs carbon dioxide (CO2). The stress-strain behaviour associated with adsorption is of key importance in determining the feasibility of extracting methane (CH4) from coal via Enhanced Coalbed Methane production. ECBM involves injection of preferentially sorbing CO2 into the t
STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A cyclic plasticity model is used into finite element (FE) method to obtain the details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteria in multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue lives are in favorable agreement with the experimental results for machined bolts.
Influence of the Geometry of Beveled Edges on the Stress-Strain State of Hydraulic Cylinders
Buyalich, G. B.; Anuchin, A. V.; Serikov, K. P.
2016-04-01
The studies were carried out to determine the influence of forms obtained when preparing edges for welding a cylinder for hydraulic legs; the maximum stresses were defined at the location of weld roots, depending on variable parameters. The stress-strain states were calculated using finite element method.
Institute of Scientific and Technical Information of China (English)
ZHAO Li; GAO Pan
2006-01-01
In order to evaluate cycling characters of zeotropic refrigerants in air-conditioning operation, and to reveal distribution rules of temperature difference between refrigerants and heat transfer fluids in condenser and evaporator, theoretical researches were carried out based on nonlinear relationship between temperature and enthalpy in period of refrigerants' phase change. Firstly, a phase changing model of refrigerants was built, and refrigerants state parameters were decided in the air-conditioning operation.Secondly, the state equation of refrigerants was applied for computing relationship between temperature and enthalpy, else based on some suppositions, temperature differences between 15 sorts of refrigerants and heat-transfer fluids were gotten too. Through concluding those temperature differences changing in condenser and evaporator, some rules were found. Lastly, after calculating and comparing the additive exergy loss among15 sorts of refrigerants, which resulted from the changing of temperature difference, their cycling characters evaluation were presented.
Non-linear relationship between combustion kinetic parameters and coal quality
Institute of Scientific and Technical Information of China (English)
Jian-guo YANG; Xiao-long ZHANG; Hong ZHAO; Li SHEN
2012-01-01
Combustion kinetic parameters (i.e.,activation energy and frequency factor) of coal have been proven to relate closely to coal properties; however,the quantitative relationship between them still requires further study.This paper adopts a support vector regression machine (SVR) to generate the models of the non-linear relationship between combustion kinetic parameters and coal quality.Kinetic analyses on the thermo-gravimetry (TG) data of 80 coal samples were performed to prepare training data and testing data for the SVR.The models developed were used in the estimation of the combustion kinetic parameters of ten testing samples.The predicted results showed that the root mean square errors (RMSEs) were 2.571 for the activation energy and 0.565for the frequency factor in logarithmic form,respectively.TG curves defined by predicted kinetic parameters were fitted to the experimental data with a high degree of precision.
Abrams, Peter A; Rueffler, Claus; Dinnage, Russell
2008-10-01
Much previous ecological and evolutionary theory about exploitative competition for a continuous spectrum of resources has used the Lotka-Volterra model with competition coefficients given by a Gaussian function of niche separation. Using explicit consumer-resource models, we show that the Lotka-Volterra model and the assumption of a Gaussian competition-similarity relationship both fail to reflect the impact of strong resource depletion, which typically reduces the influence of the most heavily used resources on the competitive interaction. Taking proper account of resource depletion reveals that strong exploitative competition between efficient consumers is usually a highly nonlinear interaction, implying that a single measure is no longer sufficient to characterize the process. The nonlinearity usually entails weak coupling of competing species when their abundances are high and equal. Rare invaders are likely to have effects on abundant residents much larger than those of the resident on the invader. Asymmetrical utilization curves often produce asymmetrical competition coefficients. Competition coefficients are typically non-Gaussian and are often nonmonotonic functions of niche separation. Utilization curve shape and resource growth functions can have major effects on competition-similarity relationships. A variety of previous theoretical findings need to be reassessed in light of these results.
Wen, Yang; He, Jia; Liu, Xian; Li, Jinjie; Zhao, Yuanhui
2012-09-01
A non-linear relationship (e.g. Gaussian-type) between measured bioconcentration factor (BCF) and octanol/water partition coefficient (K(OW)) was noted many years ago. Many studies have focused on the cause of the breakdown in the log BCF/log K(OW) curve for highly hydrophobic chemicals with log K(OW)>6. However, there has been little investigation on the theoretical background of this feature for highly hydrophilic chemicals. In this paper, the cause of linear and non-linear relationships between log BCF and log K(OW) has been investigated on the basis of the partitioning-based mechanism for classified non-ionic and ionisable compounds. For highly hydrophilic compounds, lipid tissue in fish is not the major storage site of chemicals. Uptake from other tissues/organs plays a much more important role than the lipid content, leading to a variation of measured log BCF around 0.5. For hydrophobic chemicals with 0.56. The main reason for this is attributed to the reduced bioavailability of chemicals in water. A linear solvation energy relationship shows that the bioconcentration increases with increasing molecular size by increasing the dispersion interactions between the chemical and lipid content. Bioconcentration decreases with increasing the basicity of hydrophobic compounds by increasing the H-bonding of chemicals with water. Principal component analysis shows that the octanol/water system is the closest system, but not an ideal surrogate, to describe the bioconcentration for hydrophobic compounds as compared with other solvent/water partition systems.
Escuder Bueno, Ignacio
This Thesis studies the stress-strain behavior of floodable rockfills, using data obtained from quality control of materials, control of construction and instrumentation records. As a case of study, a rockfill part of the final works for a new Madrid-Valencia motorway, located at Contreras Reservoir is used. Data were collected during construction (December 1997--August 1998) and are extended to July of 2000. After reviewing the state of art on properties of usual materials, models of behaviour, numerical tools and experiences dealing with studies based in combined analysis and field measurements, several works have been developed. Namely the synthesis of all available data, study of construction procedures, implementation of an analysis methodology and its application to the study of the stress-strain behavior during and after construction. FLAC 2D (Itasca, 1994), an explicit finite difference code, has been selected as numerical tool to perform the analysis, and results have been compared with measurements registered by total pressure and settlement cells. In order to improve the quality of analysis and to make use of all collected records to calibrate the models (taken on a weekly basis), the real constructive sequency has been simulated. Numerical calculation based in linear elastic, non linear elastic, elastoplastic and viscoelastic models have been performed. Newly developed routines have permitted to accomplish the upgrading of tangent parameters involved in non-linear hyperbolic formulation, calculation of creep deformation and settlements due to reservoir filling. As a result of the works, the stress-strain behavior of the structure has been characterized, the importance of creep deformation from first stages of construction has been identified, and capability of usually assumed models in reproducing observed behavior has been evaluated.
Sadovskii, V. M.; Sadovskaya, O. V.
2016-10-01
The Tarasov fan-shaped mechanism, simulating the formation of shear ruptures in a brittle rock at stress conditions corresponding to seismogenic depths, is analyzed. For computation of the stress-strain state of a rock near the equilibrium fan-structure the original method is constructed. The fault is modeled as a narrow elongated layer, filled with the domino-blocks, between two elastic half-spaces. Displacements and stresses around the fan are represented in the integral form as a superposition of edge dislocations with an unknown function of distribution of the Burgers vector. To take into account the stresses of lateral thrust, the solution of plane problem of the elasticity is used for a tensile crack, on the surfaces of which the previously unknown normal stresses are distributed. The exact formulation of the problem leads to a system of two nonlinear singular integral equations, which is solved numerically by the method of successive approximations. The obtained solution is used, when setting the initial data in computations of the dynamics of the Tarasov fan-shaped mechanism. With the help of this solution the discontinuous nature of shear ruptures, observed in natural and laboratory experiments, is explained.
Directory of Open Access Journals (Sweden)
Jian Yang
2017-09-01
Full Text Available Net primary productivity (NPP is an important component of the terrestrial carbon cycle. In this study, NPP was estimated based on two models and Moderate Resolution Imaging Spaectroradiometer (MODIS data. The spatiotemporal patterns of NPP and the correlations with climate factors and vegetation phenology were then analyzed. Our results showed that NPP derived from MODIS performed well in China. Spatially, NPP decreased from the southeast toward the northwest. Temporally, NPP showed a nonlinear increasing trend at a national scale, but the magnitude became slow after 2004. At a regional scale, NPP in Northern China and the Tibetan Plateau showed a nonlinear increasing trend, while the NPP decreased in most areas of Southern China. The decreases in NPP were more than offset by the increases. At the biome level, all vegetation types displayed an increasing trend, except for shrub and evergreen broad forests (EBF. Moreover, a turning point year occurred for all vegetation types, except for EBF. Generally, climatic factors and Length of Season were all positively correlated with the NPP, while the relationships were much more diverse at a regional level. The direct effect of solar radiation on the NPP was larger (0.31 than precipitation (0.25 and temperature (0.07. Our results indicated that China could mitigate climate warming at a regional and/or global scale to some extent during the time period of 2001–2014.
Schryver, Jack C; Brandt, Craig C; Pfiffner, Susan M; Palumbo, Anthony V; Peacock, Aaron D; White, David C; McKinley, James P; Long, Philip E
2006-02-01
The relationship between groundwater geochemistry and microbial community structure can be complex and difficult to assess. We applied nonlinear and generalized linear data analysis methods to relate microbial biomarkers (phospholipids fatty acids, PLFA) to groundwater geochemical characteristics at the Shiprock uranium mill tailings disposal site that is primarily contaminated by uranium, sulfate, and nitrate. First, predictive models were constructed using feedforward artificial neural networks (NN) to predict PLFA classes from geochemistry. To reduce the danger of overfitting, parsimonious NN architectures were selected based on pruning of hidden nodes and elimination of redundant predictor (geochemical) variables. The resulting NN models greatly outperformed the generalized linear models. Sensitivity analysis indicated that tritium, which was indicative of riverine influences, and uranium were important in predicting the distributions of the PLFA classes. In contrast, nitrate concentration and inorganic carbon were least important, and total ionic strength was of intermediate importance. Second, nonlinear principal components (NPC) were extracted from the PLFA data using a variant of the feedforward NN. The NPC grouped the samples according to similar geochemistry. PLFA indicators of Gram-negative bacteria and eukaryotes were associated with the groups of wells with lower levels of contamination. The more contaminated samples contained microbial communities that were predominated by terminally branched saturates and branched monounsaturates that are indicative of metal reducers, actinomycetes, and Gram-positive bacteria. These results indicate that the microbial community at the site is coupled to the geochemistry and knowledge of the geochemistry allows prediction of the community composition.
Energy Technology Data Exchange (ETDEWEB)
Schryver, Jack C.; Brandt, Craig C.; Pfiffner, Susan M.; Palumbo, A V.; Peacock, Aaron D.; White, David C.; McKinley, James P.; Long, Philip E.
2006-02-01
The relationship between groundwater geochemistry and microbial community structure can be complex and difficult to assess. We applied nonlinear and generalized linear data analysis methods to relate microbial biomarkers (phospholipids fatty acids, PLFA) to groundwater geochemical characteristics at the Shiprock uranium mill tailings disposal site that is primarily contaminated by uranium, sulfate, and nitrate. First, predictive models were constructed using feedforward artificial neural networks (NN) to predict PLFA classes from geochemistry. To reduce the danger of overfitting, parsimonious NN architectures were selected based on pruning of hidden nodes and elimination of redundant predictor (geochemical) variables. The resulting NN models greatly outperformed the generalized linear models. Sensitivity analysis indicated that tritium, which was indicative of riverine influences, and uranium were important in predicting the distributions of the PLFA classes. In contrast, nitrate concentration and inorganic carbon were least important, and total ionic strength was of intermediate importance. Second, nonlinear principal components (NPC) were extracted from the PLFA data using a variant of the feedforward NN. The NPC grouped the samples according to similar geochemistry. PLFA indicators of Gram-negative bacteria and eukaryotes were associated with the groups of wells with lower levels of contamination. The more contaminated samples contained microbial communities that were predominated by terminally branched saturates and branched monounsaturates that are indicative of metal reducers, actinomycetes, and Gram-positive bacteria. These results indicate that the microbial community at the site is coupled to the geochemistry and knowledge of the geochemistry allows prediction of the community composition.
Relationship between the temperature and the acoustic nonlinearity parameter in biological tissues
Institute of Scientific and Technical Information of China (English)
LU Ying; LIU Xiaozhou; GONG Xiufen; ZHANG Dong
2004-01-01
Recently with the rapid development of the high-intensity focused ultrasound (HIFU) in biomedical ultrasound, much attention has been paid to the noninvasive temperature estimation in biological tissue in order to determine the region and degree of the ultrasound-induced lesions. In ultrasound hyperthermal therapy it is highly desirable to study the real-time noninvasive monitoring of temperature distribution in biological tissue. In this paper, the relationship between the nonlinearity parameter B/A and the temperature in biological tissue is studied and compared with the theoretical model as well as the experimental results from the thermocouple. Results indicated that B/A could be used as an effective tool to monitor the temperature distribution in biological media.
Stress/strain distributions for weld metal solidification crack in stainless steels
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
This paper has simulated the driving force of solidification crack of stainless steels, that is, stress/strain field in the trail of molten pool. Firstly, the effect of the deformation in the molten pool was eliminated after the element rebirth method was adopted. Secondly, the influence of solidification shrinkage was taken into account by increasing thermal expansion coefficients of the steels at elevated temperatures. Finally, the stress/strain distributions of different conditions have been computed and analyzed. Furthermore, the driving force curves of the solidification crack of the steels have been obtained by converting strain-time curves into strain-temperature curves, which founds a basis for predicting welding solidification crack.
Dynamic tensile testing for determining the stress-strain curve at different strain rate
Mansilla, A; Regidor, A.; García, D.; Negro, A
2001-01-01
A detailed discussion of high strain-rate tensile testing is presented. A comparative analysis of different ways to measure stress and strain is made. The experimental stress-strain curves have been suitably interpreted to distinguish between the real behaviour of the material and the influence of the testing methodology itself. A special two sections flat specimen design was performed through FEA computer modelling. The mechanical properties as function of strain rate were experimentally obt...
FINITE ELEMENT METHOD AS A BASIS FOR THE MODELING OF ROAD SURFACE STRESS-STRAIN STATE
2011-01-01
Problem statement. Despite the fact that rigid roads with asphalt concrete pavement widespread,their design and calculation provide for approximate data with some number of hidden factors. Thepresent paper proposes to use finite element method to model stress-strain state of rigid roads withasphalt concrete pavement.Results. The use of the finite element method enables one to construct the precise model ofstress-strain state of road pavement. The calculations performed on the basis of the mod...
Yang, Bingen
2005-01-01
Stress, Strain, and Structural Dynamics is a comprehensive and definitive reference to statics and dynamics of solids and structures, including mechanics of materials, structural mechanics, elasticity, rigid-body dynamics, vibrations, structural dynamics, and structural controls. This text integrates the development of fundamental theories, formulas and mathematical models with user-friendly interactive computer programs, written in the powerful and popular MATLAB. This unique merger of technical referencing and interactive computing allows instant solution of a variety of engineering problems
In situ subsoil stress-strain behaviour in relation to soil precompression stress
DEFF Research Database (Denmark)
Keller, T; Arvidsson, J; Schjønning, Per;
2012-01-01
is assumed to be elastic and reversible as long as [sigma] laboratory. The data...... by stress-strain data measured in uniaxial compression tests, which likewise showed [Latin Small Letter Open E]res > 0 at [sigma] ... analyzed were from a large number of wheeling experiments carried out in Sweden and Denmark on soils with a wide range of texture. Contradicting the concept of precompression stress, we observed residual strain, [Latin Small Letter Open E]res, at [sigma
Computer modeling of the stress-strain state of a linear friction welded disk
Directory of Open Access Journals (Sweden)
V. Bychkov
2015-09-01
Full Text Available The paper is dedicated to design issues of tooling for linear friction welding (LFW machine. Computer model of a LFW machine was built. As a result of computer simulation, the stress-strain state of the machine and disk module for linear friction welding of aluminum alloy blisks also was obtained. On the basis of the results of computer simulation a module with a replaceable unit and a new variant fixing of disc in the module were designed.
Directory of Open Access Journals (Sweden)
Arbeiter Daniela
2017-09-01
Full Text Available Xenogenic leaflet material, bovine and porcine pericardium, is widely used for the fabrication of surgically implanted and transcatheter heart valve prostheses. As a biological material, long term durability of pericardium is limited due to calcification, degeneration and homogeneity. Therefore, polymeric materials represent a promising approach for a next generation of artificial heart valve leaflets with improved durability. Within the current study we analyzed the mechanical performance of polymeric structures based on elastomeric materials. Polymeric cast films were prepared and nonwovens were manufactured in an electrospinning process. Analysis of cyclic stress-strain behavior was performed, using a universal testing machine. The uniaxial cyclic tensile experiments of the elastomeric samples yielded a non-linear elastic response due to viscoelastic behavior with hysteresis. Equilibrium of stress-strain curves was found after a specific number of cycles, for cast films and nonwovens, respectively. In conclusion, preconditioning was found obligatory for the evaluation of the mechanical performance of polymeric materials for the use as artificial leaflet material for heart valve prostheses.
Institute of Scientific and Technical Information of China (English)
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.
Modeling of Stress- Strain Curves of Drained Triaxial Test on Sand
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Awad A. Karni
2006-01-01
Full Text Available This paper presents a hyperbolic mathematical model to predict the complete stress-strain curve of drained triaxial tests on uniform dense sand. The model was formed in one equation with many parameters. The main parameters that are needed to run the model are the confining pressure, angle of friction and the relative density. The other parameters, initial and final slopes of the stress strain curve, the reference stress and the curve-shape parameter are determined as functions of the confining pressure, angle of friction and the relative density using best fitting curve technique from the experimental tests results. Drained triaxial tests were run on clean white uniform sand to utilize and verify this model. These tests were carried out at four levels of confining pressure of 100, 200, 300 and 400 kPa. This model was used to predict the stress-strain curves for drained triaxial tests on quartz sand at different relative density using the data of Kouner[1]. The model predictions were compared with the experimental results and showed good agreements of the predicted results with the experimental results at all levels of applied confining pressures and relative densities.
Lokstein, Heiko; Betke, Alexander; Krikunova, Maria; Teuchner, Klaus; Voigt, Bernd
2012-03-01
Conventional linear and time-resolved spectroscopic techniques are often not appropriate to elucidate specific pigment-pigment interactions in light-harvesting pigment-protein complexes (LHCs). Nonlinear (laser-) spectroscopic techniques, including nonlinear polarization spectroscopy in the frequency domain (NLPF) as well as step-wise (resonant) and simultaneous (non-resonant) two-photon excitation spectroscopies may be advantageous in this regard. Nonlinear spectroscopies have been used to elucidate substructure(s) of very complex spectra, including analyses of strong excitonic couplings between chlorophylls and of interactions between (bacterio)chlorophylls and "optically dark" states of carotenoids in LHCs, including the major antenna complex of higher plants, LHC II. This article shortly reviews our previous study and outlines perspectives regarding the application of selected nonlinear laser-spectroscopic techniques to disentangle structure-function relationships in LHCs and other pigment-protein complexes.
Institute of Scientific and Technical Information of China (English)
周小平; 王建华; 张永兴; 哈秋聆
2004-01-01
The mechanical behavior of rock under uniaxial tensile loading is different from that of rock under compressive loads. A micromechanics-based model was proposed for mesoscopic heterogeneous brittle rock undergoing irreversible changes of their microscopic structures due to microcrack growth. The complete stress-strain relation including linear elasticity, nonlinear hardening,rapid stress drop and strain softening was obtained. The influence of all microcracks with different sizes and orientations were introduced into the constitutive relation by using the probability density function describing the distribution of orientations and the probability density function describing the distribution of sizes. The influence of Weibull distribution describing the distribution of orientations and Rayleigh function describing the distribution of sizes on the constitutive relation were researched. Theoretical predictions have shown to be consistent with the experimental results.
In Situ Characterization of Soils for Prediction of Stress Strain Relationship of Soft Clay.
1982-11-10
measurements (the electrical ones) and hence be able to perform analysis of earth structures on the basis of the calibrated bounding surface soil plasticity model...of Mechanics, 31, 5, pp. 723-739, Warszawa, 1979. 13. Dafalias, Y.F. and Herrmann, L.R., "A Bounding Surface Soil Plasticity Model," Int. Symp. on...Surface Formulation of Soil Plasticity ," Chapter 10 in Soil Mechanics-Transient and Cyclic Loads, G.N. Pande and O.C. Zienkicwicz eds, 3. Wiley and Sons
3-dimensional slope stability analyses using non-associative stress-strain relationships
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The research work presented in this paper refers to a new slope stability analysis method used for landslide risk evaluations. It is an extension of the 3-dimensional upper-bound slope stability analysis method proposed by Chen et al. in 2001,which employs the Mohr-Coulomb’s associative flow rule. It has been found that in a 3-dimensional area,a prism may not be able to move at friction angles to all its surrounding interfaces,as required by this associative rule,and convergence problems may occasionally arise. The new method establishes two velocity fields:(i) The plastic one that represents a non-associative and the best representative dilation behavior,and (ii) the virtual one that permits the solution for factor of safety in the work and energy balance equation. The new method can then allow any input value of dilation angle and thus solve the convergence problem. A practical application to a concrete dam foundation is illustrated.
3-dimensional slope stability analyses using non-associative stress-strain relationships
Institute of Scientific and Technical Information of China (English)
CHEN ZuYu; SUN Ping; WANG YuJie; ZHANG HongTao
2009-01-01
The research work presented in this paper refers to a new slope stability analysis method used for landslide risk evaluations. It is an extension of the 3-dimensional upper-bound slope stability analysis method proposed by Chen et sl. in 2001, which employs the Mohr-Coulomb's associative flow rule. It has been found that in a 3-dimensional area, a prism may not be able to move at friction angles to all its surrounding interfaces, as required by this associative rule, and convergence problems may occa-sionally arise. The new method establishes two velocity fields: (i) The plastic one that represents a non-associative and the best representative dilation behavior, and (ii) the virtual one that permits the solution for factor of safety in the work and energy balance equation. The new method can then allow any input value of dilation angle and thus solve the convergence problem. A practical application to a concrete dam foundation is illustrated.
Karimi, Alireza; Navidbakhsh, Mahdi
2014-12-01
The umbilical cord is part of the fetus and generally includes one umbilical vein (UV) and two umbilical arteries (UAs). As the saphenous vein and UV are the most commonly used veins for the coronary artery disease treatment as a coronary artery bypass graft (CABG), understating the mechanical properties of UV has a key asset in its performance for CABG. However, there is not only a lack of knowledge on the mechanical properties of UV and UA but there is no agreement as to which stress-strain definition should be implemented to measure their mechanical properties. In this study, the UV and UA samples were removed after caesarean from eight individuals and subjected to a series of tensile testing. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were employed to determine the linear mechanical properties of UVs and UAs. The nonlinear mechanical behavior of UV/UA was computationally investigated using hyperelastic material models, such as Ogden and Mooney-Rivlin. The results showed that the effect of varying the stress definition on the maximum stress measurements of the UV/UA is significant but not when calculating the elastic modulus. In the true stress-strain diagram, the maximum strain of UV was 92 % higher, while the elastic modulus and maximum stress were 162 and 42 % lower than that of UA. The Mooney-Rivlin material model was designated to represent the nonlinear mechanical behavior of the UV and UA under uniaxial loading.
Study on Rail Profile Optimization Based on the Nonlinear Relationship between Profile and Wear Rate
Directory of Open Access Journals (Sweden)
Jianxi Wang
2017-01-01
Full Text Available This paper proposes a rail profile optimization method that takes account of wear rate within design cycle so as to minimize rail wear at the curve in heavy haul railway and extend the service life of rail. Taking rail wear rate as the object function, the vertical coordinate of rail profile at range optimization as independent variable, and the geometric characteristics and grinding depth of rail profile as constraint conditions, the support vector machine regression theory was used to fit the nonlinear relationship between rail profile and its wear rate. Then, the profile optimization model was built. Based on the optimization principle of genetic algorithm, the profile optimization model was solved to achieve the optimal rail profile. A multibody dynamics model was used to check the dynamic performance of carriage running on optimal rail profile. The result showed that the average relative error of support vector machine regression model remained less than 10% after a number of training processes. The dynamic performance of carriage running on optimized rail profile met the requirements on safety index and stability. The wear rate of optimized profile was lower than that of standard profile by 5.8%; the allowable carrying gross weight increased by 12.7%.
Stress-Strain Compression of AA6082-T6 Aluminum Alloy at Room Temperature
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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.
Numerical Evaluation of Size Effect on the Stress-Strain Behaviour of Geotextile-Reinforced Sand
DEFF Research Database (Denmark)
Hosseinpour, I.; Mirmoradi, S.H.; Barari, Amin;
2010-01-01
This paper studies the effect of sample size on the stress-strain behavior and strength characteristics of geotextile reinforced sand using the finite element numerical analysis. The effect of sample size was investigated by studying the effects of varying the number of geotextile layers...... axial strain at failure in comparison with large-sized samples. The size effect on the behavior of samples became further apparent when the number of geotextile layers was increased or the confining pressure was decreased. In addition, the results indicated that the magnitude of the size effect...
Stress-strain state and durability of mechanically inhomogeneous welds under low-cycle loading
Brazenas, A.; Daunis, M.
2008-02-01
Relations are proposed for the determination of the stress-strain state, strength, and life of butt welds with mild and hard interlayers under cyclic elastoplastic tension-compression. The accumulation of cyclic and quasistatic damages is determined with allowance for the redistribution of the cyclic elastoplastic strains and hardness of the stress state due to changes in the cyclic properties of separate regions of welds. The theoretical distribution of cyclic strains and the durability of welds under cyclic elastoplastic loading are supported by experimental data
Determination of stress-strain state of the wooden church log walls with software package
Directory of Open Access Journals (Sweden)
Chulkova Anastasia
2016-01-01
Full Text Available The restoration of architectural monuments is going on all over the world today. The main aim of restoration is the renewal of stable functioning of building constructions in normal state. In this article, we have tried to figure out with special software the bearing capacity of log cabins of the Church of Transfiguration on Kizhi island. As shown in research results, determination of stress-strain stage with software package is necessary for the bearing capacity computation as well as field tests.
Generalized Phenomenological Cyclic Stress-Strain-Strength Characterization of Granular Media.
1984-09-02
following special form of the general hypoelastic equation to model the behavior of granular media: dij = [a0 dem + a3 "pq d pq] 6ij + 1 dcij + C 2 dem...Phenomitno ogical I C.yclic Stress-Strain-Strength Characterization f Granular M~dia !RSO%.hL APT’.OR(S) M._McVay,_D._Seereeram,_P.__Linton andD... Granular Medi a, Vollow Cylinder. Cyclic Triaxial Test, Plasticity, Prediction Expanding Cavity LClic CTC rests ISTAAC? fCoom w mz_’-. ,f_.V,,A6’V "d
Frequency Response of Synthetic Vocal Fold Models with Linear and Nonlinear Material Properties
Shaw, Stephanie M.; Thomson, Scott L.; Dromey, Christopher; Smith, Simeon
2012-01-01
Purpose: The purpose of this study was to create synthetic vocal fold models with nonlinear stress-strain properties and to investigate the effect of linear versus nonlinear material properties on fundamental frequency (F[subscript 0]) during anterior-posterior stretching. Method: Three materially linear and 3 materially nonlinear models were…
Fertility Differentials and Educational Attainment in Portugal: A Non-Linear Relationship
Directory of Open Access Journals (Sweden)
Tiago de Oliveira, Isabel
2009-01-01
Full Text Available AbstractThis analysis of the Portuguese case shows a non-linear relationship betweenthe number of children and education in recent years. Using the data from tenyears before this hypothesis was confirmed, and we can see that the generaldecline in Portuguese fertility within the last decade was due to the fertilitydecrease of the less educated people, although partly attenuated by the fertilityincrease of the upper social groups. The reasons for a non-linear relationshipare discussed within the context of female employment rates and salarydifferentials by educational attainment. The main hypothesis is that differencesin fertility are related to an ‘education-work’ effect amongst those in the lesseducated groups and to an ‘education-income’ effect amongst the moreeducated.RésuméL’analyse de cas de la situation au Portugal démontre une relation non linéaireentre le nombre d’enfants et le niveau de scolarité au cours des dernièresannées. Les données recueillies pendant les dix dernières années ont étéétudiées avant de confirmer cette hypothèse ; nous avons pu voir que le déclingénéral dans le taux de fécondité au Portugal pendant la dernière décade étaitcausé par un déclin de fécondité chez les personnes moins éduquées ; ceci a étépartiellement atténué par une hausse dans le taux de fécondité dans les classessupérieures. Les raisons de cette relation non linéaire sont discutées dans lecontexte des taux d’emploi des femmes et les différentiels de salaire selon lesniveaux de scolarité. L’hypothèse majeure est que les différences dans les tauxde fécondité sont reliés à un effet « scolarité-travail » parmi les groupes moinséduqués et à un effet « scolarité-salaire » parmi les classes mieux éduqués.
Cui, Xiao-Lei; Yang, Zhai-Ping; Wang, Xiao-Song
2017-01-01
To further explore the characterization of the multiaxial stress-strain responses of anisotropic tube metal from double-sided hydro-bulging tests, an analytical model for the equivalent stress and equivalent strain calculation was derived based on Hosford's 1979 yield criterion. Furthermore, thin-walled 5052-O aluminum alloy tubes were used to conduct the bulging experiment with an external pressure of 85 MPa. After the experimental data were substituted into the above analytical model, the Voce equation was used to fit the equivalent stress-strain relationship. It is concluded that the stress versus strain curves of the 5052-O tubes are strongly dependent on the loaded stress states, the adopted yield criteria, and the anisotropy coefficients. The external pressure of 85 MPa had little or no effect on the stress versus strain curves of the tubes, but the locations of the multiaxial stress versus strain curves were lower than that of the uniaxial stress versus strain curve. Moreover, the curve from Hosford's 1979 yield criterion not only had a higher saturation stress and material constant value than the curve from Mises and Hill's 1948 yield criteria but also had a dependence on the anisotropy coefficient.
Modelling long term rockslide displacements with non-linear time-dependent relationships
De Caro, Mattia; Volpi, Giorgio; Castellanza, Riccardo; Crosta, Giovanni; Agliardi, Federico
2015-04-01
Rockslides undergoing rapid changes in behaviour pose major risks in alpine areas, and require careful characterization and monitoring both for civil protection and mitigation activities. In particular, these instabilities can undergo very slow movement with occasional and intermittent acceleration/deceleration stages of motion potentially leading to collapse. Therefore, the analysis of such instabilities remains a challenging issue. Rockslide displacements are strongly conditioned by hydrologic factors as suggested by correlations with groundwater fluctuations, snowmelt, with a frequently observed delay between perturbation and system reaction. The aim of this work is the simulation of the complex time-dependent behaviour of two case studies for which also a 2D transient hydrogeological simulation has been performed: Vajont rockslide (1960 to 1963) and the recent Mt. de La Saxe rockslide (2009 to 2012). Non-linear time-dependent constitutive relationships have been used to describe long-term creep deformation. Analyses have been performed using a "rheological-mechanical" approach that fits idealized models (e.g. viscoelastic, viscoplastic, elasto-viscoplastic, Burgers, nonlinear visco-plastic) to the experimental behaviour of specific materials by means of numerical constants. Bidimensional simulations were carried out using the finite difference code FLAC. Displacements time-series, available for the two landslides, show two superimposed deformation mechanisms: a creep process, leading to movements under "steady state" conditions (e.g. constant groundwater level), and a "dynamic" process, leading to an increase in displacement rate due to changes of external loads (e.g. groundwater level). For both cases sliding mass is considered as an elasto-plastic body subject to its self-weight, inertial and seepage forces varying with time according to water table fluctuation (due to snowmelt or changing in reservoir level) and derived from the previous hydrogeological
STUDY ON STRESS-STRAIN PROPERTIES OF REACTIVE POWDER CONCRETE UNDER UNIAXIAL COMPRESSION
Directory of Open Access Journals (Sweden)
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.
Analysis of stress-strain state of the spherical shallow shell with inclusion
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O.B. Kozin
2016-05-01
Full Text Available Development of effective methods of determining the stress-strain state thin-walled structures with inclusions, reinforcements and other stress concentrators is an important task, both from a theoretical and practical point of view, by reason of their great practical application. Aim: The aim of the research is to analyze the elastic-deformed state of a spherical shallow shell. Materials and Methods: In this work, based on the generalized scheme of integral transformations, a constructive method of direct numerical-analytical solutions of boundary value problem of calculating the stress-strain state of a spherical shallow shell with the inclusion in bending is proposed. Results: The results of numerical calculations are presented. Calculations allow predicting the value of deformation of the cylindrical shells structure with reinforcements and determining the optimum parameters for the design or manufacture. The obtained results can be used in determining the strength characteristics of structural elements that consist of composite materials. The article contains comparative analysis of the results and demonstrates the effectiveness of the method for solving this class of problems.
Stress-strain analysis of porous scaffolds made from titanium alloys synthesized via SLS method
Shishkovsky, I.
2009-09-01
A layer-by-layer selective laser sintering (SLS) technology seems to be greatly promising for solving the plastic surgery problems, particularly those pertaining to the facial reconstruction. Made from titanium-based alloys (titanium or nitinol, i.e. NiTi-intermetallic phase), the porous scaffolds for cranioplasty are an efficient tool for rectifying the face defects and for the dental orthopedic surgery. The progress in the oral surgery and teeth implantation is caused by the problem of an osteointegration on the one hand, and by achievements of the implant synthesis techniques, on the other hand. An important problem thereby is a profound study of the stress-strain behavior of porous implants under the masticatory load or pressure. In the present study the ways for the optimization of the porous implant structural and strength properties as the function of the laser synthesis parameters are described. The finite element approach (ANSYS) was used here for a complex dowel description and numerical simulations. In order to evaluate the processes in the porous implant under the external loading, a CAD 3D model was built for different internal and external configurations of the implant and/or initial shape of powdered particles. The stress-strain dependences were calculated that displayed the irregularity of the stress distribution by the implant volume in the bone tissue. Most of the values are concentrated in places of object contact.
Relations of complete creep processes and triaxial stress-strain curves of rock
Institute of Scientific and Technical Information of China (English)
李云鹏; 王芝银; 唐明明; 王怡
2008-01-01
Based on the results of triaxial compressive creep tests for five kinds of rock under the different stress loading,unloading and cycle-loading-unloading conditions,the creep deformation is not only a function of stress and time,but also it has the corresponding relations to the triaxial stress-strain curves of rock.The deformation properties of soften-strain,harden-strain and ideal plasticity presented by conventional triaxial compressive test curves under the different stress states were utilized,and the creep characteristics,the creep starting stress and the different entire creep process curves of rock were studied systematically according to creep experiment results,and the relations of the triaxial stress-strain curves to the creeping starting stress,the terminating curve,the different creep processes,and the different creep fracture properties were established.The relations presented in this paper were verified partially by the creep experiment results of five types of rock.
STRESS - STRAIN CURVE ANALYSIS OF WOVEN FABRICS MAD E FROM COMBED YARNS TYPE WOOL
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VÎLCU Adrian
2014-05-01
Full Text Available The paper analyses the tensile behavior of woven fabrics made from 45%Wool + 55% PES used for garments. Analysis of fabric behavior during wearing has shown that these are submitted to simple and repeated uni-axial or bi-axial tensile strains. The level of these strains is often within the elastic limit, rarely going over yielding. Therefore the designer must be able to evaluate the mechanical behavior of such fabrics in order to control the fabric behavior in the garment. This evaluation is carried out based on the tensile testing, using certain indexes specific to the stress-strain curve. The paper considers an experimental matrix based on woven fabrics of different yarn counts, different or equal yarn count for warp and weft systems and different structures. The fabrics were tested using a testing machine and the results were then compared in order to determine the fabrics’ tensile behavior and the factors of influence that affect it.From the point of view of tensile testing, the woven materials having twill weave are preferable because this type of structure is characterized by higher durability and better yarn stability in the fabric. In practice, the woven material must exhibit an optimum behavior to repeated strains, flexions and abrasions during wearing process. The analysis of fabrics tensile properties studied by investigation of stress-strain diagrams reveals that the main factors influencing the tensile strength are: yarns fineness, technological density of those two systems of yarns and the weaving type.
Stress-strain curves for different loading paths and yield loci of aluminum alloy sheets
Institute of Scientific and Technical Information of China (English)
WU Xiang-dong; WAN Min; HAN Fei; WANG Hai-bo
2006-01-01
To carry out biaxial tensile test in sheet metal, the biaxial tensile testing system was established. True stress-true strain curves of three kinds of aluminum alloy sheets for loading ratios of 4:1, 4:2, 4:3, 4:4, 3:4, 2:4 and 1:4 were obtained by conducting biaxial tensile test in the established testing systems. It shows that the loading path has a significant influence on the stress-strain curves and as the loading ratio increases from 4:1 to 4:4, the stress-strain curve becomes higher and n-value becomes larger.Experimental yield points for three aluminum alloy sheets from 0.2% to 2% plastic strain were determined based on the equivalent plastic work. And the geometry of the experimental yield loci were compared with the yield loci calculated from several existing yield criteria. The analytical result shows that the Barlat89 and Hosford yield criterion describe the general trends of the experimental yield loci of aluminum alloy sheets well, whereas the Mises yield criterion overestimates the yield stress in all the contours.
Directory of Open Access Journals (Sweden)
A. Mustapha
2012-01-01
Full Text Available The effect of microstructure on the stress-strain behaviour of pipeline steels was studied. Slow strain rate (2×10-6 s-1 tests were conducted on grade X65 and X100 steels in silicone oil and hydrogen carbonate/carbonate solution. The as-received grade X100 steel at 75°C showed serrated stress-strain curves. The magnitude of the serrations depended upon the strain rate and test temperature. Annealing at 600°C or above removes the serrations, but this increased the susceptibility to transgranular cracking in hydrogen carbonate/carbonate solution at potentials below −800 mV (sce. The removal and reformation of banding in pipeline steels were also studied. Ferrite/pearlite becomes aligned during the hot rolling stage of pipe manufacture and causes directionality in crack propagation and mechanical properties. Heat treatments were carried out which show that banding in grade X65 and X100 can be removed above 900°C. This depends on homogenisation of carbon which also depends on temperature, time, and cooling rate.
Hieber, Simone E.; Koumoutsakos, Petros
2008-11-01
We present a novel Lagrangian particle method for the simulation of linear and nonlinear elastic models of soft tissue. Linear solids are represented by the Lagrangian formulation of the stress-strain relationship that is extended to nonlinear solids by using the Lagrangian evolution of the deformation gradient described in a moving framework. The present method introduces a level set description, along with the particles, to capture the body deformations and to enforce the boundary conditions. Furthermore, the accuracy of the method in cases of large deformations is ensured by implementing a particle remeshing procedure. The method is validated in several benchmark problems, in two and three dimensions and the results compare well with the results of respective finite elements simulations. In simulations of large solid deformation under plane strain compression, the finite element solver exhibits spurious structures that are not present in the Lagrangian particle simulations. The particle simulations are compared with experimental results in an aspiration test of liver tissue.
Institute of Scientific and Technical Information of China (English)
LIU Chun-Ping; LING Zhi
2005-01-01
By using the generally projective Riccati equation method, a series of doubly periodic solutions (Jacobi elliptic function solution) for a class of nonlinear partial differential equations are obtained in a unified way. When the module m → 1, these solutions exactly degenerate to the soliton solutions of the equations. Then we reveal the relationship between the soliton-like solutions obtained by other authors and these soliton solutions of the equations.
Wu, Jiefeng; Chen, Xingwei; Yao, Huaxia; Gao, Lu; Chen, Ying; Liu, Meibing
2017-08-01
Exploring the relationship between hydrological and meteorological droughts under influence of large reservoirs is crucial for early warning of hydrological drought. This study took Jinjiang River basin in the southeast coastal region of China as an example, where the Shilong hydrometric station is influenced by a large reservoir (Shanmei), and the Anxi hydrological station is not. Based on monthly data of streamflow with precipitation and historical drought records from 1960 to 2010, the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) series (representing meteorological drought and hydrological drought, respectively) were each calculated with a 3-month timescale. Run theory was then used to identify the characteristics of meteorological and hydrological drought, including duration and magnitude. The relationship with which hydrological drought responds to meteorological drought was established by a non-linear function model at the Anxi station and Shilong station which reflected the periods of natural condition without reservoir and reservoir-influence condition, respectively. The results indicate that (1) there was a clear non-linear relationship of hydrological drought and meteorological drought, and the threshold within which hydrological drought started to respond to meteorological drought was obtained according to the non-linear function model; (2) the operational activities of the Shanmei reservoir during 1983-2010 have significantly reduced the duration and magnitude of hydrological drought at the Shilong station compared to the natural-influence period of 1960-1982, which, in turn, altered the relationship between the hydrological drought and meteorological drought. The propagation process from meteorological to hydrological droughts was shortened because of the changed relationship.
Research on nonlinear constitutive relationship of permanent deformation in asphalt pavements
Institute of Scientific and Technical Information of China (English)
PENG; Miaojuan; XU; Zhihong
2006-01-01
To predict correctly the rut depths in asphalt pavements,a new nonlinear viscoelastic-elastoplastic constitutive model of permanent deformation in asphalt pavements is presented.The model combines a generalized Maxwell model with an elastoplastic one.Then from the creep theory,the linear and nonlinear constitutive equations of the generalized Maxwell model are obtained.From the nonlinear finite element method for the rutting of the asphalt pavement,the rut depths of 4 asphalt-aggregate mixtures are obtained.And the results are compared with the ones from the finite element method by SHRP and the experiments by SWK/UN.The results in this paper are better than the ones by SHRP,and agree with the ones of the experiment by SWK/UN.This shows that the nonlinear viscoelastic-elastoplastic constitutive model,which is presented in this paper for the rutting of the asphalt pavement,is effective.The properties,such as nonlinear elasticity,plasticity,viscoelasticity and nonlinear viscoelasticity,which affect the rutting of an asphalt pavement,can be shown in the model.And the characteristics of the permanent deformation of the asphalt pavement can be presented entirely in the model.
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.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Ultra-high performance cementitious composites (UHPCC) were prepared by replacing 60% of cement with ultra-fine industrial waste powders.The dynamic damage and compressive stress-strain relations of UHPCC were studied using split Hopkinson pressure bar (SHPB).The damage of UHPCC subjected to repeated impact was measured by the ultrasonic pulse velocity method.Results show that the dynamic damage of UHPCC increases linearly with impact times and the abilities of repeated impact resistance of UHPCC are improved with increasing fiber volume fraction.The stress waves on impact were recorded and the average stress,strain and strain rate of UHPCC were calculated based on the wave propagation theory.The effects of strain rate,fibers volume fraction and impact times on the stress-strain relations of UHPCC were studied.Results show that the peak stress and elastic modulus decrease while the strain rate and peak strain increase gradually with increasing impact times.
Spline Nonparametric Regression Analysis of Stress-Strain Curve of Confined Concrete
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Tavio Tavio
2008-01-01
Full Text Available Due to enormous uncertainties in confinement models associated with the maximum compressive strength and ductility of concrete confined by rectilinear ties, the implementation of spline nonparametric regression analysis is proposed herein as an alternative approach. The statistical evaluation is carried out based on 128 large-scale column specimens of either normal-or high-strength concrete tested under uniaxial compression. The main advantage of this kind of analysis is that it can be applied when the trend of relation between predictor and response variables are not obvious. The error in the analysis can, therefore, be minimized so that it does not depend on the assumption of a particular shape of the curve. This provides higher flexibility in the application. The results of the statistical analysis indicates that the stress-strain curves of confined concrete obtained from the spline nonparametric regression analysis proves to be in good agreement with the experimental curves available in literatures
Superelastic stress-strain behavior in ferrogels of different types of magneto-elastic coupling
Cremer, Peet; Menzel, Andreas M
2016-01-01
Colloidal magnetic particles embedded in an elastic polymer matrix constitute a smart material called ferrogel. It responds to an applied external magnetic field by changes in elastic properties, which can be exploited for various applications like dampers, vibration absorbers, or actuators. Under appropriate conditions, the stress-strain behavior of a ferrogel can display a fascinating feature: superelasticity, the capability to reversibly deform by a huge amount while barely altering the applied load. In a previous work, using numerical simulations, we investigated this behavior assuming that the magnetic moments carried by the embedded particles can freely reorient to minimize their magnetic interaction energy. Here, we extend the analysis to ferrogels where restoring torques by the surrounding matrix hinder rotations towards a magnetically favored configuration. For example, the particles can be chemically cross-linked into the polymer matrix and the magnetic moments can be fixed to the particle axes. We ...
DEFF Research Database (Denmark)
Bellini, Anna; Thorborg, Jesper; Hattel, Jesper
2004-01-01
In order to satisfy the growing need in high quality aluminum cast parts of the automobile industries, in the last decades the foundries have been showing an increasing interest in the implementation of numerical simulations as part of their process design. As a consequence, it is possible to find...... the analysis of the next phases, such as heat treatment and life prediction of the cast parts. Because of the lack of numerical program tools capable of predicting the stress-strain behavior of aluminum parts subjected to high temperature, it is indeed normally assumed that at the end of the thermal treatment...... in literature several programs capable of simulating the entire casting process, i.e. filling, solidification, as well as developed thermomechanical stresses. However, it is common practice in the foundry industry that the results obtained by the simulation of the cast process are "forgotten" during...
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.
Study of the stress-strain state of compressed concrete elements with composite reinforcement
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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.
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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.
STRESS-STRAIN STATE IN EMBEDMENT OF REINFORCEMENT IN CASE OF REPEATED LOADINGS
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Mirsayapov Ilshat Talgatovich
2016-05-01
Full Text Available The author offer transforming the diagram of ideal elastic-plastic deformations for the description of the stress-strain state of embedment of reinforcement behind a critical inclined crack at repeatedly repeating loadings. The endurance limit of the adhesion between concrete and reinforcement and its corresponding displacements in case of repeated loadings are accepted as the main indicators. This adhesion law is the most appropriate for the description of physical and mechanical phenomena in the contact zone in case of cyclic loading, because it simply and reliably describes the adhesion mechanism and the nature of the deformation, and greatly simplifies the endurance calculations compared to the standard adhesion law. On the basis of this diagram the author obtained the equations for the description of the distribution of pressures and displacements after cyclic loading with account for the development of deformations of cyclic creep of the concrete under the studs of reinforcement.
Magnuski, Mikołaj; Gola, Mateusz
2013-09-01
We have investigated the interplay between face orientation, eye presence, and N170 amplitude by recording Event Related Potentials. To clarify previous reports of nonlinearity in N170 amplitude changes along rotation angle changes, we adopted Itier et al.'s model (Itier et al., 2007) which links N170 face inversion effects with the presence of eyes. Comparison of N170 amplitude and latency for five stimulus categories (Faces-with-eyes, Faces-without-eyes, Eyes, Cars-with-lights, Cars-without-lights) in five different rotations (0, 45, 90, 135, 180) resulted in mixed conclusions. The main findings of this study are as follows: (1) a strong nonlinear relationship between N170 and angle of rotation that is specific to faces, distinguishing face from car category even when no significant differences were observed between these categories for upright and inverted orientations; and (2) the nonlinear relationship between N170 and angle of rotation does not depend on eye presence. We also propose an alternative model according to which N170 amplitude consists of two related aspects of face processing: (A) incompatibility (relative distance of the stimulus pattern from experience-based hypothetical prototype) and (B) integration (degree to which stimulus is integrated into holistic representation), with the former affecting the latter. Moreover, we suggest two possible neural events underlying these two aspects of face processing: neural population size activated by the stimulus, and synchronization within this population.
Energy Technology Data Exchange (ETDEWEB)
López-Téllez, J. M., E-mail: jmlopez@comunidad.unam.mx; Bruce, N. C. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, Apdo. Postal 70-186, México D.F., 04510 (Mexico)
2014-03-15
We present a method for using liquid-crystal variable retarders (LCVR’s) with continually varying voltage to measure the Stokes vector of a light beam. The LCVR's are usually employed with fixed retardance values due to the nonlinear voltage-retardance behavior that they show. The nonlinear voltage-retardance relationship is first measured and then a linear fit of the known retardance terms to the detected signal is performed. We use known waveplates (half-wave and quarter-wave) as devices to provide controlled polarization states to the Stokes polarimeter and we use the measured Stokes parameters as functions of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. Results are compared to a Fourier analysis method that does not take into account the nonlinear voltage-retardance relationship and also to a Fourier analysis method that uses experimental voltage values to give a linear retardance function with time. Also, we present results of simulations for comparison.
López-Téllez, J M; Bruce, N C
2014-03-01
We present a method for using liquid-crystal variable retarders (LCVR's) with continually varying voltage to measure the Stokes vector of a light beam. The LCVR's are usually employed with fixed retardance values due to the nonlinear voltage-retardance behavior that they show. The nonlinear voltage-retardance relationship is first measured and then a linear fit of the known retardance terms to the detected signal is performed. We use known waveplates (half-wave and quarter-wave) as devices to provide controlled polarization states to the Stokes polarimeter and we use the measured Stokes parameters as functions of the orientation of the axes of the waveplates as an indication of the quality of the polarimeter. Results are compared to a Fourier analysis method that does not take into account the nonlinear voltage-retardance relationship and also to a Fourier analysis method that uses experimental voltage values to give a linear retardance function with time. Also, we present results of simulations for comparison.
Wang, Da-ming; Zhu, Bin; Ding, Liang-cai; Liu, Ning; Zhang, Jin-song
2010-06-01
To study the relationship between the resuscitation therapy and intensive insulin therapy on stress-induced hyperglycemia in severe sepsis and septic shock patients, and to evaluate the value on nonlinear viewpoint in the treatment of patients with sepsis. The data of 129 hospitalized patients with severe sepsis and septic shock were analyzed and they were divided into eight groups every 6 hours in ascending order for full recovery. The resuscitation therapy time of each group was compared with insulin dosage in each unit time with nonlinear least square method. The relationship of the exponential function fit very well between the resuscitation therapy time of each group and the insulin dosage in each unit time. The exponential curve equation was y=e0.739 3-0.015 2x2 (a=0.739 3, b=0.015 2) and the curve fit very well (R2=0.976 943 6). It conforms to the nonlinear viewpoint that the resuscitation therapy time is closely correlated with recovery of dysfunction of endocrine system during the treatment for patients with severe sepsis and septic shock. Therefore, the essence of successful treatment is to concentrate on helping the body rebuild the disorganized network and the recovery of physiological harmony rather than to support and repair the damaged organs.
Experimental determination of the micro-scale strength and stress-strain relation of an epoxy resin
DEFF Research Database (Denmark)
Zike, Sanita; Sørensen, Bent F.; Mikkelsen, Lars Pilgaard
2016-01-01
An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments in an en......An approach is developed for determining the stress-strain law and a failure stress appropriate for micro-mechanical models of polymer materials. Double cantilever beam test specimens, made of an epoxy polymer with notches having finite root radius, were subjected to pure bending moments...
Directory of Open Access Journals (Sweden)
Світлана Михайлівна Талах
2017-01-01
Full Text Available The problem of improving the scientific basis to determine the stress-strain state of non-rigid pavements, renovated by cold recycling technology, is considered. The results of numerical calculation of stress-strain state of non-rigid pavements in the section of road Kyv-Kovel (297 + 700 km - 302 + 400 km are given using automated calculation software complex of thin-walled spatial structures (KARTPK. The real state of the road section through 8.5 years after the renovation is analyzed
DEFF Research Database (Denmark)
Palleti, Hara Naga Krishna Teja; Thomsen, Ole Thybo; Taher, Siavash Talebi;
In this paper, polymer foam cored sandwich structures with fibre reinforced composite face sheets subjected to combined mechanical and thermal loads will be analysed using the commercial FE code ABAQUS® incorporating both material and geometrical nonlinearity. Large displacements and rotations ar...... are included in the analysis. The full nonlinear stress-strain curves up to failure will be considered for the polymer foams at different temperatures to study the effect of material nonlinearity in detail....
Institute of Scientific and Technical Information of China (English)
Chen Hongxia; Chen Yunxia; Yang Zhou
2014-01-01
Fatigue induced products generally bear fatigue loads accompanied by impact processes, which reduces their reliable life rapidly. This paper introduces a reliability assessment model based on a local stress-strain approach considering both low-cycle fatigue and high energy impact loads. Two coupling relationships between fatigue and impact are given with effects of an impact process on fatigue damage and effects of fatigue damage on impact performance. The analysis of the former modifies the fatigue parameters and the Manson-Coffin equation for fatigue life based on material theories. On the other hand, the latter proposes the coupling variables and the difference of fracture toughness caused by accumulative fatigue damage. To form an overall reliability model including both fatigue failure and impact failure, a competing risk model is developed. A case study of an actuator cylinder is given to validate this method.
The Nonlinear Dynamic Relationship of Exchange Rates: Parametric and Nonparametric Causality testing
Bekiros, S.D.; Diks, C.
2007-01-01
The present study investigates the long-term linear and nonlinear causal linkages among six currencies, namely EUR/USD, GBP/USD, USD/JPY, USD/CHF, AUD/USD and USD/CAD. The prime motivation for choosing these exchange rates comes from the fact that they are the most liquid and widely traded, covering
Bekiros, S.D.; Diks, C.G.H.
2007-01-01
The present study investigates the linear and nonlinear causal linkages between daily spot and futures prices for maturities of one, two, three and four months of West Texas Intermediate (WTI) crude oil. The data cover two periods October 1991-October 1999 and November 1999-October 2007, with the la
Bekiros, S.D.; Diks, C.G.H.
2008-01-01
The present study investigates the linear and nonlinear causal linkages between daily spot and futures prices for maturities of one, two, three and four months of West Texas Intermediate (WTI) crude oil. The data cover two periods October 1991-October 1999 and November 1999-October 2007, with the la
Bekiros, S.D.; Diks, C.G.H.
2007-01-01
The present study investigates the linear and nonlinear causal linkages between daily spot and futures prices for maturities of one, two, three and four months of West Texas Intermediate (WTI) crude oil. The data cover two periods October 1991-October 1999 and November 1999-October 2007, with the
Bekiros, S.D.; Diks, C.G.H.
2008-01-01
The present study investigates the linear and nonlinear causal linkages between daily spot and futures prices for maturities of one, two, three and four months of West Texas Intermediate (WTI) crude oil. The data cover two periods October 1991-October 1999 and November 1999-October 2007, with the
Baranowski, Z.; Lugovoi, P. Z.
2008-04-01
The ray-path method is used to analyze the stress-strain state near mine workings acted upon by discontinuous waves. A dynamic failure criterion is proposed for analyzing the stability of mine workings. The efficiency of the approach is demonstrated with a specific example
Yu, Hongbing; Yao, Zhongwen; Daymond, Mark R.
2017-09-01
In this paper, a dual phase Zr-Sn-Nb-Mb alloy was studied with TEM after thermal treatment and high-temperature tensile deformation. Plate and pressure tube material, manufactured through different processing routes, were used in this study. The overall average concentrations of Mo and Nb in the β phase are higher in the pressure tube than in the plate. It was revealed that these concentrations have significant effects on the subsequent stability of the β and ω phases as well as on the precipitation behavior of the α phase from the β phase. That is, the higher the concentrations, the more stable the β and ω phases are, and hence there is a reduced tendency for precipitation of α phase. Aging treatments cause the transformation of athermal ω to isothermal ω, as expected. The most striking finding is the product of the decomposition of the isothermal ω particles during aging treatment is determined as not being α phase, even though the structure of it is, as-yet, not fully determined. The non-uniform morphology of the β grains in the plate material provides us a unique opportunity to investigate the effects of morphology on the aging response of the β phase. It was found that thin β filaments suppress the precipitation of isothermal ω particles but enhance the precipitation of α phase at α/β interfaces. The effect of the Burgers orientation relationship between α and β grains on the precipitation of the α phase at the α/β interface is discussed. Applied high-temperature stress/strain has been found to enhance the decomposition of isothermal ω phase but suppress α precipitation inside the β grains. The suppression of α precipitation by applied stress/strain is discussed in terms of the ω assisted α precipitation. Implications of these findings for the in-service application of the alloy are discussed.
Non-linear magnetorheological behaviour of an inverse ferrofluid
de Gans, B.J.; Hoekstra, Hans; Mellema, J.
1999-01-01
The non-linear magnetorheological behaviour is studied of a model system consisting of monodisperse silica particles suspended in a ferrofluid. The stress/strain curve as well as the flow curve was measured as a function of volume fraction silica particles and field strength, using a home-made
Analysis of stress-strain state on top of a rectangular wedge
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Frishter Lyudmila Yur'evna
2014-05-01
Full Text Available Modeling singular solutions of the elasticity theory problems, which are determined by geometric factor - bird's mouth of the edge, make it necessary to analyze the solutions with some peculiarity, which are obtained experimentally with the help of photoelasticity method. In this article the peculiar stress-strain state is analyzed on the example of the known experimental solutions for a wedge under a concentrated force obtained by M. Frocht. Solution analysis for a wedge with a power-type peculiarity obtained experimentally by photoelasticity method, helps to detach a singular solution field, where fringe contour is not visible. Due to idealization of the boundary shape and loading technique, infinitely large stresses arise, which are obtained as a singular solution of the boundary problem in a planar domain. Comparison of theoretical and experimental solutions obtained for a wedge shows areas of overlap and areas of significant and insignificant differences as a result of the inability to experimentally apply the force to a single point.
Problematics of stress-strain state research in units of metal structures
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Morozova Dina Vol'demarovna
2014-05-01
Full Text Available The article describes the experimental methods of determining stress-strain state of elements and structures with a brief description of the essence of each method. The authors focus mostly on polarization-optical method for determining stresses in the translucent optical sensing models made of epoxy resins. Physical component of the method is described in the article and a simple diagram of a circular polariscope is presented, as well as an example of the resulting interference pattern in illuminated monochromatic light. A polariscope, in its most general definition, consists of two polarizers. The polarizers sandwich a material or object of interest, and allows one to view the changes of the polarity of light passing through the material or object. Since we are unable to perceive the polarity of light with the naked eye, we are forced to use polariscopes to view the changes in polarity caused by the temporary birefringence of our photoelastic materials. A polariscope is constructed of two polarizers, each set perpendicular to the path of light transmitted through the setup. The first polarizer is called the "polarizer", and the second polarizer is called the "analyzer". The method how the polarizer works is quite simple: unpolarized light enters the polariscope through the polarizer, which allows through only the light of its orientation. This light then passes through the material under observation, and experiences some change in polarity. Finally, this light reaches the analyzer, which, like the polarizer, only lets the light of its orientation through.
To Honor Fechner and Obey Stevens: Relationships between Psychophysical and Neural Nonlinearities
Billock, Vincent A.; Tsou, Brian H.
2011-01-01
G. T. Fechner (1860/1966) famously described two kinds of psychophysics: "Outer psychophysics" captures the black box relationship between sensory inputs and perceptual magnitudes, whereas "inner psychophysics" contains the neural transformations that Fechner's outer psychophysics elided. The relationship between the two has never been clear.…
Return-Volatility Relationship: Insights from Linear and Non-Linear Quantile Regression
D.E. Allen (David); A.K. Singh (Abhay); R.J. Powell (Robert); M.J. McAleer (Michael); J. Taylor (James); L. Thomas (Lyn)
2013-01-01
textabstractThe purpose of this paper is to examine the asymmetric relationship between price and implied volatility and the associated extreme quantile dependence using linear and non linear quantile regression approach. Our goal in this paper is to demonstrate that the relationship between the
Wear, Keith A
2015-03-01
Through-transmission measurements were performed on 30 human calcaneus samples in vitro. Nonlinear attenuation and dispersion measurements were investigated by estimating 95% confidence intervals of coefficients of polynomial expansions of log magnitude and phase of transmission coefficients. Bone mineral density (BMD) was measured with dual x-ray absorptiometry. Microarchitecture was measured with microcomputed tomography. Statistically significant nonlinear attenuation and nonzero dispersion were confirmed for a clinical bandwidth of 300-750 kHz in 40%-43% of bone samples. The mean linear coefficient for attenuation was 10.3 dB/cm MHz [95% confidence interval (CI): 9.0-11.6 dB/cm MHz]. The mean quadratic coefficient for attenuation was 1.6 dB/cm MHz(2) (95% CI: 0.4-2.8 dB/cm MHz(2)). Nonlinear attenuation provided little information regarding BMD or microarchitecture. The quadratic coefficient for phase (which is related to dispersion) showed moderate correlations with BMD (r = -0.65; 95% CI: -0.82 to -0.36), bone surface-to-volume ratio (r = 0.47; 95% CI: 0.12-0.72) and trabecular thickness (r = -0.40; 95% CI: -0.67 to -0.03). Dispersion was proportional to bone volume fraction raised to an exponent of 2.1 ± 0.2, which is similar to the value for parallel nylon-wire phantoms (2.4 ± 0.2) and supports a multiple-scattering model for dispersion.
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Dimitrios Kourkoutas
2009-04-01
Full Text Available Dimitrios Kourkoutas1,2, Gerasimos Georgopoulos1, Antonios Maragos1, et al1Department of Ophthalmology, Medical School, Athens University, Athens, Greece; 2Department of Ophthalmology, 417 Hellenic Army Shared Fund Hospital, Athens, GreecePurpose: In this paper a new nonlinear multivariable regression method is presented in order to investigate the relationship between the central corneal thickness (CCT and the Heidelberg Retina Tomograph (HRTII optic nerve head (ONH topographic measurements, in patients with established glaucoma.Methods: Forty nine eyes of 49 patients with glaucoma were included in this study. Inclusion criteria were patients with (a HRT II ONH imaging of good quality (SD 30 < μm, (b reliable Humphrey visual field tests (30-2 program, and (c bilateral CCT measurements with ultrasonic contact pachymetry. Patients were classified as glaucomatous based on visual field and/or ONH damage. The relationship between CCT and topographic parameters was analyzed by using the new nonlinear multivariable regression model.Results: In the entire group, CCT was 549.78 ± 33.08 μm (range: 484–636 μm; intraocular pressure (IOP was 16.4 ± 2.67 mmHg (range: 11–23 mmHg; MD was −3.80 ± 4.97 dB (range: 4.04 – [−20.4] dB; refraction was −0.78 ± 2.46 D (range: −6.0 D to +3.0 D. The new nonlinear multivariable regression model we used indicated that CCT was significantly related (R2 = 0.227, p < 0.01 with rim volume nasally and type of diagnosis.Conclusions: By using the new nonlinear multivariable regression model, in patients with established glaucoma, our data showed that there is a statistically significant correlation between CCT and HRTII ONH structural measurements, in glaucoma patients.Keywords: central corneal thickness, glaucoma, optic nerve head, HRT
The Relationship between Tsallis Statistics, the Fourier Transform, and Nonlinear Coupling
Nelson, Kenric P
2008-01-01
Tsallis statistics (or q-statistics) in nonextensive statistical mechanics is a one-parameter description of correlated states. In this paper we use a translated entropic index: $1 - q \\to q$ . The essence of this translation is to improve the mathematical symmetry of the q-algebra and make q directly proportional to the nonlinear coupling. A conjugate transformation is defined $\\hat q \\equiv \\frac{{- 2q}}{{2 + q}}$ which provides a dual mapping between the heavy-tail q-Gaussian distributions, whose translated q parameter is between $ - 2 < q < 0$, and the compact-support q-Gaussians, between $0 < q < \\infty $ . This conjugate transformation is used to extend the definition of the q-Fourier transform to the domain of compact support. A conjugate q-Fourier transform is proposed which transforms a q-Gaussian into a conjugate $\\hat q$ -Gaussian, which has the same exponential decay as the Fourier transform of a power-law function. The nonlinear statistical coupling is defined such that the conjugate ...
Impact of rockfill deformation on stress-strain state on dam reinforced concrete face
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Sainov Mikhail Petrovich
2015-03-01
Full Text Available The author considered the results of the numerical studies of stress-strain state of a 100 m high rockfill dam with a reinforced concrete face. In the analysis, the dam construction sequence and loads applied to it were considered; it was assumed that the reinforced concrete face was constructed after filling the dam. The calculations were carried out in the elastic formulation at various moduli of deformation and Poisson’s ratio. It was revealed that at rockfill settlement under the action of hydrostatic pressure the reinforced concrete face not only bends but also is subject to longitudinal force. The development of these forces is connected not only with rockfill shear deformation in horizontal direction. Depending on the value of rockfill Poisson’s ratio these longitudinal forces may be both compressive and tensile. At the Poisson’s ratio exceeding 0.25 the longitudinal forces are tensile, and when it is equal to 0.2 - they are compressive. Evidently these particular longitudinal forces are the course of crack formation in reinforced concrete faces of a number of constructed dams. The indirect confirmation of the development of tensile forces on the face is the fact that actually in all the dams with reinforced concrete face opening of perimeter joint was observed. Thus, in order to provide the strength of reinforced concrete it is important to increase rockfill shear modulus. Only the decrease of stone compressibility (i.e. increase of linear deformation modulus E will slightly improve the stress state of the face, as the value of E has less effect on settlements and shear of the dam than Poisson’s ratio. High rockfill dams with reinforced concrete face may have a favorable stress state only at narrow site when the face horizontal displacements are inconsiderable and due to the settlements of rockfill in the face the forces are compressive but not tensile longitudinal forces.
Studies on Stress-Strain Curves of Aged Composite Solid Rocket Propellants
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Himanshu Shekhar
2012-03-01
Full Text Available Mechanical property evaluation of composite solid rocket propellants is used as a quick quality control tool for propellant development and production. However, stress-strain curves from uni-axial tensile testing can be utilised to assess the shelf-life of propellants also. Composite propellants (CP of two varieties cartridge-loaded (CLCP and case-bonded (CBCP are utilized in rocket and missile applications. Both classes of propellants were evaluated for mechanical properties namely tensile strength, modulus and percentage elongation using specimens conforming to ASTM D638 type IV at different ageing time. Both classes of propellants show almost identical variation in various mechanical properties with time. Tensile strength increases with time for both classes of propellants and percentage elongation reduces. Initial modulus is also found to decrease with time. Tensile strength is taken as degradation criteria and it is observed that CLCP has slower degradation rate than CBCP. This is because of two facts–(i higher initial tensile strength of CLCP (1.39 MPa compared to CBCP (0.665 MPa and (ii lower degradation rate of CLCP (0.0014 MPa/day with respect to CBCP (0.0025 MPa/day. For the studied composite propellants, a degradation criterion in the form of percentage change in tensile strength is evaluated and shelf life for different degradation criteria is tabulated for quick reference.Defence Science Journal, 2012, 62(2, pp.90-94, DOI:http://dx.doi.org/10.14429/dsj.62.773
METHOD FOR CALCULATION OF STRESS-STRAIN STATE DUE TO SINGLE TWIN IN GRAIN OF VARIOUS FORMS
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T. V. Drabysheuskaya
2016-01-01
Full Text Available The paper investigates a stress-strain state in a polycrystalline grain due to presence in its body of a single micro- twin in case of various grain boundary forms. A methodology for calculation of displacement and stress fields for the specified stress-strain state of a polygon-shaped grain has been developed in the paper. Nodal points in a polycrystalline grain that have a maximum stresses contributing to initiation of destruction have been revealed in the paper. The aim of this work has been to study the stress-strain state due to a single micro-twin in the polycrystalline grain and form of grain boundaries. The paper describes polycrystalline grains having a regular polygon shape and containing a single wedge twin in their body. Polycrystalline grain boundaries are presented as walls with complete dislocation. The investigated grains are located far from the surface of twinning material. The developed methodology for calculation of displacement and stresses created by wedge twin is based on the principle of superposition. Calculations on stress tensor components have been carried out for iron (Fe. The presented results of calculations for stress fields have indicated to validity of the used dislocation model. Twin and grain boundaries being stress concentrators are clearly visible on the obtained distributions of stress fields. Maximum normal stresses are observed on the twin boundaries; σxy maximum shear stresses are located at nodal points of the twin; σzy and σxz shear stresses are maximum on the grain boundaries. The conducted investigations have resulted in study of the stress-strain state due to a single wedge-shaped micro-twin in the polycrystalline grain and form of the grain boundaries. Zones of stress concentration in the polycrystalline grain have been identified in the presence of residual mechanical wedge twin. A method for evaluation of the given state has been developed in the paper.
Influence of Loading System Stiffness on Post-peak Stress-Strain Curve of Stable Rock Failures
Xu, Y. H.; Cai, M.
2017-09-01
It is well known from laboratory testing that the rock failure process becomes unstable in a soft test machine due to excessive energy released from the machine. Great efforts had been devoted to increasing the loading system stiffness (LSS) of laboratory test machines to ensure that the post-peak stress-strain curve of rock can be obtained for underground rock engineering design. A comprehensive literature review on the development of stiff test machines reveals that because of the differences in the manufacturing arrangement of the test machines, LSS values of the test machines used for rock property testing are always finite and vary in a large range, and the influence of LSS on stable rock failure is less understood. A FEM-based numerical experiment is carried out to study the influence of LSS on the stress-strain curves of stable rock failure in uniaxial compression, with a focus on the post-peak deformation stage. Three test machine loadings including idealized rigid loading, platen loading, and frame-platen loading with finite LSS are considered, and the simulation results are analyzed and compared. The modeling results obtained from the simulations indicate that even if the LSS value is large enough to inhibit unstable rock failure, as long as LSS is finite, it has an influence on the post-peak stress-strain curve of rock. It is revealed that because the input energy supplied by the external energy source to drive the stable rock failure process is affected by the finite LSS of a test machine, the post-peak descending slopes of the stress-strain curves are all steeper than the post-peak descending slope obtained under an ideal loading condition of infinite LSS. An insight from this numerical experiment is that it might be more feasible to develop laboratory test machines with variable LSS that can match the local mine stiffness in the field for rock property testing.
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I. S. Kulikov
2010-01-01
Full Text Available The paper considers peculiar features of stress-strain condition of nuclear reactor active zone elements which are under an influence of high temperature and neutron irradiation with due account of thermal and radiation creepage taking jackets of heat releasing elements in the form of hollow thick-walled cylinder as an example. The numerical results of stresses and deformations which have been obtained with the account of creep strain and without it are presented in the paper.
Energy Technology Data Exchange (ETDEWEB)
Williams, Paul T.
2004-12-01
The cross-sectional relationships of weekly walking distance to BMI, body circumferences, and bra cup sizes are reported for 27,596 women. The percent reductions between walking 40-50 km/wk and < 10km/wk were greatest for BMI, substantial for waist circumference and cupsize, and least for hip and chest circumferences. The relationships between distance and adiposity were nonlinear with respect to both the independent (quadratic function of distance) and dependent variables(slope and curvilinearity depending upon the percentile of BMI, circumference, or cup size). The slope relating adiposity to km/wk were greatest (most negative) in overweight sedentary women and least in lean active women. For example, compared to women averaging 10 km/wk, the slope of BMI versus km/wk was 43 percent less at 25 km/wk and 87 percent less at 40 km/wk in overweight women (95th BMI percentile), but negligible at all distances in lean women (5th BMI percentile). The greater estimated decrease in BMI per km/wk in walkers than runners was largely accounted for (over 75 percent) by the walkers greater adiposity. Thus classical representations of the relationship between adiposity and moderate physical activity are inadequate for either statistical analyses or descriptive purposes. The clinical implications of these results and their statistical ramifications are discussed.
Huan, Huiting; Mandelis, Andreas; Lashkari, Bahman; Liu, Lixian
2017-04-01
The evaluation of the stress-strain state of metallic materials is an important problem in the field of non-destructive testing (NDT). Prolonged cyclic loading or overloading will lead to permanent changes of material strength in an inconspicuous manner that poses threat to the safety of structures, components and products. This research focuses on gauging the mechanical strength of metallic alloys through the application of frequency-domain laser ultrasound (FDLU) based on a continuous-wave diode laser source. The goal is to develop industrial NDT procedures for fatigue monitoring in metallic substrates and coatings so that the technique can be used for mechanical strength assessment. A small-scale, non-commercial rig was fabricated to hold the sample and conduct tensile FDLU testing in parallel with an adhesive strain gauge affixed on the tested sample for independent measurement of the applied stress. Harmonic modulation and lock-in detection were used to investigate the LU signal sensitivity to the stress-strain state of ordinary aluminum alloy samples. A 1 MHz focused piezoelectric transducer was used to detect the LU signal. During the tensile procedure, both amplitude and phase signals exhibited good repeatability and sensitivity to the increasing stress-strain within the elastic regime. Signals beyond the elastic limit also revealed significant change patterns.
Institute of Scientific and Technical Information of China (English)
ZHAO Xiqing; ZANG Xinliang; WANG Qingfeng; Park Joongkeun; YANG Qingxiang
2008-01-01
The stress-strain curve of an a-β Ti-8Mn alloy was measured and then it was calculated with finite element method (FEM) based on the stress-strain curves of the single α and β phase alloys.By comparing the calculated stress-strain curve with the measured one,it can be seen that they fit each other very well.Thus,the FE model built in this work is effective.According to the above mentioned model,the distributions of stress and strain in the α and β phases were simulated.The results show that the stress gradients exist in both α and β phases,and the distributions of stress are inhomogeneons.The stress inside the phase is generally higher than that near the interface.Meanwhile,the stress in the α phase is lower than that in the β phase,whereas the strain in the a phase is higher than that in the β phase.
Du, Yi-Chun; Chen, Yung-Fu; Li, Chien-Ming; Lin, Chia-Hung; Yang, Chia-En; Wu, Jian-Xing; Chen, Tainsong
2013-12-01
The Achilles tendon is one of the most commonly observed tendons injured with a variety of causes, such as trauma, overuse and degeneration, in the human body. Rupture and tendinosis are relatively common for this strong tendon. Stress-strain properties and shape change are important biomechanical properties of the tendon to assess surgical repair or healing progress. Currently, there are rather limited non-invasive methods available for precisely quantifying the in vivo biomechanical properties of the tendons. The aim of this study was to apply quantitative ultrasound (QUS) methods, including ultrasonic attenuation and speed of sound (SOS), to investigate porcine tendons in different stress-strain conditions. In order to find a reliable method to evaluate the change of tendon shape, ultrasound measurement was also utilized for measuring tendon thickness and compared with the change in tendon cross-sectional area under different stress. A total of 15 porcine tendons of hind trotters were examined. The test results show that the attenuation and broadband ultrasound attenuation decreased and the SOS increased by a smaller magnitude as the uniaxial loading of the stress-strain upon tendons increased. Furthermore, the tendon thickness measured with the ultrasound method was significantly correlated with tendon cross-sectional area (Pearson coefficient = 0.86). These results also indicate that attenuation of QUS and ultrasonic thickness measurement are reliable and potential parameters for assessing biomechanical properties of tendons. Further investigations are needed to warrant the application of the proposed method in a clinical setting.
Energy Technology Data Exchange (ETDEWEB)
Christ, H J [Institut fuer Werkstofftechnik, Universitaet Siegen, D-57068 Siegen (Germany); Bauer, V, E-mail: hans-juergen.christ@uni-siegen.d [Wieland Werke AG, Graf-Arco Str. 36, D-89072 Ulm (Germany)
2010-07-01
The cyclic stress-strain behaviour of metals and alloys in cyclic saturation can reasonably be described by means of simple multi-component models, such as the model based on a parallel arrangement of elastic-perfectly plastic elements, which was originally proposed by Masing already in 1923. This model concept was applied to thermomechanical fatigue loading of two metallic engineering materials which were found to be rather oppositional with respect to cyclic plastic deformation. One material is an austenitic stainless steel of type AISI304L which shows dynamic strain aging (DSA) and serves as an example for a rather ductile alloy. A dislocation arrangement was found after TMF testing deviating characteristically from the corresponding isothermal microstructures. The second material is a third-generation near-gamma TiAl alloy which is characterized by a very pronounced ductile-to-brittle transition (DBT) within the temperature range of TMF cycling. Isothermal fatigue testing at temperatures below the DBT temperature leads to cyclic hardening, while cyclic softening was found to occur above DBT. The combined effect under TMF leads to a continuously developing mean stress. The experimental observations regarding isothermal and non-isothermal stress-strain behaviour and the correlation to the underlying microstructural processes was used to further develop the TMF multi-composite model in order to accurately predict the TMF stress-strain response by taking the alloy-specific features into account.
Noorizadeh, Hadi; Sajjadifar, Sami; Farmany, Abbas
2013-01-01
We performed studies on extended series of 79 HEPT ligands (1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine), inhibitors of HIV reverse-transcriptase with anti-HIV biological activity, using quantitative structure-activity relationship (QSAR) methods that imply analysis of correlations and representation of models. A suitable set of molecular descriptors was calculated, and the genetic algorithm was employed to select those descriptors which resulted in the best-fit models. The kernel partial least square and Levenberg-Marquardt artificial neural network were utilized to construct the nonlinear QSAR models. The proposed methods will be of great significance in this research, and would be expected to apply to other similar research fields.
Energy Technology Data Exchange (ETDEWEB)
Bellendir, E. N.; Gordon, L. A., E-mail: lev-gordon@mail.ru; Khrapkov, A. A.; Skvortsova, A. E., E-mail: SkvortsovaAE@vniig.ru [B. E. Vedeneev All-Russia Research Institute of Hydraulic Engineering (VNIIG) (Russian Federation)
2017-01-15
Current studies of the stress-strain state of the dam at the Sayano-Shushenskaya Hydroelectric Power Plant at VNIIG based on mathematical modeling including full scale and experimental data are described. Applications and programs intended for automatic operational evaluation of the stress-strain state of the dam for optimizing control of the upper race level in the course of the annual filling-drawdown cycle and during seismic events are examined. Improvements in systems for monitoring the stress-strain state of concrete dams are proposed.
Mulder, H.A.; Hill, W.G.; Knol, E.F.
2015-01-01
There is recent evidence from laboratory experiments and analysis of livestock populations that not only the phenotype itself, but also its environmental variance, is under genetic control. Little is known about the relationships between the environmental variance of one trait and mean levels of oth
Mulder, H.A.; Hill, W.G.; Knol, E.F.
2015-01-01
There is recent evidence from laboratory experiments and analysis of livestock populations that not only the phenotype itself, but also its environmental variance, is under genetic control. Little is known about the relationships between the environmental variance of one trait and mean levels of
Estimation of land surface evaporation using a generalized nonlinear complementary relationship
Zhang, Lu; Cheng, Lei; Brutsaert, Wilfried
2017-02-01
Evaporation is a key component of the hydrological cycle and affects regional water resources. Although the physics of evaporation is well understood, its estimation in practice remains a challenge. Among available methods for estimating it, the complementary principle of Bouchet has the potential to provide a practical tool for regional water resources assessment. In this study, the generalized nonlinear formulation of this principle by Brutsaert (2015) was tested against evaporation measurements from four flux stations in Australia under different climatic and vegetation conditions. The method was implemented using meteorological data and Class A pan evaporation measurements. After calibration the estimated daily evaporation values were in good agreement with flux station measurements with a mean correlation coefficient of 0.83 and a bias of 4% on average. More accurate estimates of daily evaporation were obtained when the evaporative demand or apparent potential evaporation was determined from the Penman equation instead of from pan evaporation. The obtained parameter values were found to lie well within the ranges of reported values in the literature. Advantages of the method are that only routine meteorological data are required and that it can be used to estimate long-term evaporation trends.
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Ranjit Shrestha
2015-02-01
Full Text Available In the present paper, 3 Dimensional welding simulation was carried out in the FE software ANSYS in order to predict temperature, stress, strain and deformation in the joining of similar and dissimilar materials. The numerical simulation shows that temperature exceeds well above the melting temperature of the substrate material in the welding region. It is found that, higher residual stress is distributed in the weld bead area and surrounding heat affected zone. The stress and strain distribution patterns in the specimen showed that both tended to concentrate at or near points of application of thermal load, and were generally not uniform in these areas. It is also found that Stress and strain were concentrated at corners, edges, and other areas of abrupt change in the shape of the specimen and was also not uniform where the cross-section of the structure changed suddenly, and had large gradients at localized points. The deformation was found maximum at the beginning and the end of welding direction (Y-axis and minimum at the ends of X-axis as they are simply supported in both ends. In addition, among the six different cases of similar and dissimilar materials (S40C+S40C, STS304+STS304, STS316L+STS316L, S40C+STS304, S40C+STS316L, STS304+STS316L, the minimum temperature was found in S40C+STS304 whereas the maximum temperature was S40C+STS316L; the minimum stress was found in case of S40C+STS304 and maximum stress was found in 40C+STS316L; the minimum strain was found in case of S40C+STS304 and maximum strain was found in STS304+STS304; the minimum deformation was found in S40C+S40C and maximum in S40C+STS316L.The prediction show qualitative good agreement with the experimental results found in the literature and hence it was confirmed that the method of finite elements has proved to be successful for proper design analysis.
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Likhacheva Svetlana Yur'evna
2012-12-01
The findings of the prototype testing include identification of the two areas of deformations: areas of elastic deformations and areas of intensive development of deformations. The first area of partial elastic deformations is characterized by the linear stress function, while the second area demonstrates that this relationship is nonlinear. Permanent deformations appear as of the startup of the loading process and disproportionate stress is demonstrated throughout the deformation process. However, in the first area (partial elastic deformations residual deformations are so small that this area is considered as the area of "the area of incomplete elasticity".
Institute of Scientific and Technical Information of China (English)
张勃阳; 白海波; 张凯
2016-01-01
-seepage relationship of fillings is divided into pressure elastic segment, damage and creep stage, and the permeability presents the change rule of decrease-increase-decrease in complete stress-strain process; 2) The peak value of permeability decreases with the increasing confining pressure, and the ratio of the permeability in the complete stress-strain process has a exponential function relation with the confining pressure difference in complete stress-strain process; 3) The initial permeability and porosity of fillings decreases with the increase of initial moisture content, and the ratio of permeability and porosity have a power function relationship. The difference between peak and initial permeability decreases with the increasing initial moisture content in complete stress-strain process.
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Evgenij Kalentev
2017-06-01
Full Text Available The paper presents the results of a numerical analysis of the stress-strain state of a rope strand with linear contact under tension and torsion loading conditions. Calculations are done using the ANSYS software package. Different approaches to calculation of the stress-strain state of ropes are reviewed, and their advantages and deficiencies are considered. The analysis of the obtained results leads us to the conclusion that the proposed method can be used in engineering calculations.
2015-06-18
OF FOUR NON-OXIDE CERAMIC MATRIX COMPOSITES THESIS JUNE 2015 Sarah M. Wallentine, Captain, USAF AFIT-ENY-MS-15-J-048 DEPARTMENT OF THE...TEMPERATURES ON TENSILE PROPERTIES AND STRESS-STRAIN BEHAVIOR OF FOUR NON-OXIDE CERAMIC MATRIX COMPOSITES THESIS Presented to the Faculty...PRIOR EXPOSURE AT ELEVATED TEMPERATURES ON TENSILE PROPERTIES AND STRESS-STRAIN BEHAVIOR OF FOUR NON-OXIDE CERAMIC MATRIX COMPOSITES Sarah M
Kar, Swayamsiddha; Adithya, K. S.; Shankar, Pruthvik; Jagadeesh Babu, N.; Srivastava, Sailesh; Nageswara Rao, G.
2017-07-01
Nine chalcones were prepared via Claisen-Schmidt condensation, and characterized by UV-vis, IR, 1H NMR, 13C NMR and mass spectrometry. One of the representative member 4-NDM-TC has been studied via single crystal XRD and the TGA/DTA technique. SHG efficiency and NLO susceptibilities of the chalcones have been evaluated by the Kurtz and Perry method and Degenerate Four Wave Mixing techniques respectively. 3-Cl-4‧-HC was noted to possess SHG efficiency 1.37 times that of urea while 4-NDM-TC returned the highest third order NLO susceptibilities with respect to CS2. In silico studies help evaluate various physical parameters, in correlating the observed activities. In conclusion, the structure-activity relationship was derived based on the in silico and experimental results for the third order NLO susceptibilities.
The Nonlinear Relationship between Bank Credits and Agricultural Employment in Mazandaran Province
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Alireza Keikha
2014-12-01
Full Text Available Mazandaran province is one of the most important agricultural areas in Iran. Researches findings show that the role of bank credits is really important due to the lack of available funds in agricultural sector. In this study, the relationship between allocation of Agricultural Bank credits of Iran as professional bank section and agricultural employment was studied in the Mazandaran province based on a threshold error correction model during 1981-2011. The results show that the impact of credits on agricultural employment has been significantly different in upper and lower level of estimated threshold. The estimated threshold is about 44 percent for bank credits. The impact of bank credits on agricultural employment will be significantly negative when they exceeds from the threshold point. The results confirm transfer of capital from agriculture to other sections, resulting in a lack of integrated management for credit allocation system.
Food addiction and body-mass-index: a non-linear relationship.
Meule, Adrian
2012-10-01
Excessive food consumption has been recognized to show similarities with substance dependence. Subsequently, it has been proposed that food addiction might contribute to the obesity epidemic. Recent studies using questionnaires for the assessment of food addiction have found statistically significant, but negligible positive correlations with body-mass-index (BMI). Moreover, group comparisons between food-addicted and non-addicted individuals in normal-weight or obese samples did not show differences in BMI. However, the prevalence of food addiction diagnoses is remarkably increased in obese individuals. In the current article, it is suggested that there might be a cubic relationship between food addiction and BMI. Food addiction symptomatology may remain stable in the under- and normal-weight range, increase in the overweight- and obese range, and level off at severe obesity. Empirical data in support of this view are presented.
EVALUATION OF STRESS-STRAIN STATE OF CONSTRUCTION STRUCTURES UNDER SEISMIC LOADS EXPOSURE
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Maryenkov M.G.
2015-12-01
Full Text Available The results of spatial interaction evaluation of the elements in the "basis - foundation - structure" system under seismic loads exposure were presented in this paper. The oscillation damping processes in the ground and engineering constructions were taken into account. Calculations of the structure on pile foundation and comparison of the results from the first form of natural vibrations were conducted. The comparison of the oscillation amplitudes of the construction under elastic and non-linear deformations was made.
Wölfle, Stephanie E; Chaston, Daniel J; Goto, Kenichi; Sandow, Shaun L; Edwards, Frank R; Hill, Caryl E
2011-05-15
Blood flow is adjusted to tissue demand through rapidly ascending vasodilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site,while dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of dilatation found in larger arteries.We conclude that long distance spread of locally initiated dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
Nonlinear Relationship of Near-Bed Velocity and Growth of Riverbed Periphyton
Directory of Open Access Journals (Sweden)
Mohamed Ateia
2016-10-01
Full Text Available Artificial streams were set up to test the relationship between near-bed water velocity and periphyton growth. Periphyton community samples collected from a Japanese stream were incubated for 44 days under a light intensity of 252 ± 72 μmol·photons/m2·s, a temperature of 20–25 °C, and three near-bed water velocity classes: low (<17.9 cm/s, moderate (17.9–32.8 cm/s, and high (>32.8 cm/s. A logistic model was applied to estimate the maximum net growth rate (μmax and carrying capacity (Bmax. A response surface method was also applied to estimate chlorophyll a (Chl-a and ash-free dry mass (AFDM with respect to the independent variables (i.e., time and water velocity. We detected both the highest μmax (1.99 d−1 and highest Bmax (7.01 mg/m2 for Chl-a at the moderate water velocity. For AFDM, we observed the highest μmax (0.57 d−1 and Bmax (1.47 g/m2 at the low and moderate velocity classes, respectively. The total algae density in the region of moderate velocity at the end of the experiment was 6.47 × 103 cells/cm2, corresponding to levels 1.7 and 1.3 times higher than those at lower and higher velocities, respectively. Our findings indicated that the moderate near-bed water velocity provided favorable conditions for algal growth and corresponding biomass accumulation.
Springback Analysis in Sheet Metal Forming of Non-linear Work-Hardening material Under Pure Bending
Lal, Radha Krishna; Dwivedi, Jai Prakash; Bhagat, Manish Kumar; Singh, Virendra Pratap
2016-09-01
This paper deals with the springback analysis in sheet metal forming for non-linear work-hardening material under pure bending. Using the deformation theory of plasticity, formulation of the problem and spring back ratio is derived using Ramberg-Osgood stress strain relationship with Tresca and Von-Mises yielding criteria. The results have been representing the effect of different value of Y/E or σo/E ratio, different values of strain hardening index (n), Poisson's ratio (ν) and thickness on springback ratio (R0/Rf). The main aim of this paper is to study the effects of the thickness, Y/E ratio, n and Poisson's ratio in spring back ratio.
Wang, John T.; Bomarito, Geoffrey F.
2016-01-01
This study implements a plasticity tool to predict the nonlinear shear behavior of unidirectional composite laminates under multiaxial loadings, with an intent to further develop the tool for use in composite progressive damage analysis. The steps for developing the plasticity tool include establishing a general quadratic yield function, deriving the incremental elasto-plastic stress-strain relations using the yield function with associated flow rule, and integrating the elasto-plastic stress-strain relations with a modified Euler method and a substepping scheme. Micromechanics analyses are performed to obtain normal and shear stress-strain curves that are used in determining the plasticity parameters of the yield function. By analyzing a micromechanics model, a virtual testing approach is used to replace costly experimental tests for obtaining stress-strain responses of composites under various loadings. The predicted elastic moduli and Poisson's ratios are in good agreement with experimental data. The substepping scheme for integrating the elasto-plastic stress-strain relations is suitable for working with displacement-based finite element codes. An illustration problem is solved to show that the plasticity tool can predict the nonlinear shear behavior for a unidirectional laminate subjected to multiaxial loadings.
Majumder, Manoj K; S, Ramkumar; Mahajan, Dhiraj K; Basu, Sumit
2010-01-01
Simulation of the deformation of polymers below their glass transition through molecular dynamics provides an useful route to correlate their molecular architecture to deformation behavior. However, present computational capabilities severely restrict the time and length scales that can be simulated when detailed models of these macromolecules are used. Coarse-graining techniques for macromolecular structures intend to make bigger and longer simulations possible by grouping atoms into superatoms and devising ways of determining reasonable force fields for the superatoms in a manner that retains essential macromolecular features relevant to the process under study but jettisons unnecessary details. In this work we systematically develop a coarse-graining scheme aimed at simulating uniaxial stress-strain behavior of polymers below their glass transition. The scheme involves a two step process of obtaining the coarse grained force field parameters above glass transition. This seems to be enough to obtain "faithful" stress-strain responses after quenching to below the glass transition temperature. We apply the scheme developed to a commercially important polymer polystyrene, derive its complete force field parameters and thus demonstrate the effectiveness of the technique.
A New Method to Evaluate Rock Mass Brittleness Based on Stress-Strain Curves of Class I
Xia, Y. J.; Li, L. C.; Tang, C. A.; Li, X. Y.; Ma, S.; Li, M.
2017-05-01
Brittleness is a key controlling parameter for rock engineering projects such as hydrocarbon production and other applications. In this paper, commonly used methods based on stress-strain curves of Class I for the calculation of rock brittleness are reviewed. In order to describe the rock brittleness more reasonable, the new index B i was proposed based on the stress drop rate obtained from post-peak stress-strain curve and the ratio of elastic energy released during failure to the total energy stored before the peak strength. Then the validity of B i is verified with experimental tests conducted on rock specimens drilled from the interlayer and oil layer through a well of Shengli Oilfield. Moreover, numerical simulation is performed to analyze the effects of primary mechanical parameters on the brittleness of rock masses. Based on experimental tests and numerical simulation results, the acoustic emission modes influenced by brittleness index B i are summarized. At last, correlation between acoustic emission mechanism and index B i is verified by comparing the acoustic emission modes of limestone under different levels of confining pressure and various types of coal.
Directory of Open Access Journals (Sweden)
Khodzhiboev Abduaziz Abdusattorovich
2012-10-01
Full Text Available The subject matter of the article represents a solution to the problem of the stress-strain state of a heterogeneous structure resting on the elastic half-plane. The condition of continuity of deformations and stresses alongside the line of contact between the sections of the structure and between the structure and the half-plane is observed; the system of boundary equations is derived on the basis of the above. Coefficients associated with unknown values of the structure are identified with the help of Kelvin's fundamental solutions, while the coefficients associated with the half-plane are identified on the basis of the Mindlin's solutions. The mathematical model and the analytical algorithm developed by the author are implemented within the framework of the examination of the stress-strained state of an earth dam. Analysis of application of the algorithm has proven that concentrated shearing stresses emerge in the area of the upper wall alongside the line of contact between the structure and the half-plane, while mechanical properties of sections of the structure and the half-plane influence the distribution of vertical relocations of the half-plane contour line.
He, Ling-Yun; Chen, Shu-Peng
2011-01-01
Nonlinear dependency between characteristic financial and commodity market quantities (variables) is crucially important, especially between trading volume and market price. Studies on nonlinear dependency between price and volume can provide practical insights into market trading characteristics, as well as the theoretical understanding of market dynamics. Actually, nonlinear dependency and its underlying dynamical mechanisms between price and volume can help researchers and technical analysts in understanding the market dynamics by integrating the market variables, instead of investigating them in the current literature. Therefore, for investigating nonlinear dependency of price-volume relationships in agricultural commodity futures markets in China and the US, we perform a new statistical test to detect cross-correlations and apply a new methodology called Multifractal Detrended Cross-Correlation Analysis (MF-DCCA), which is an efficient algorithm to analyze two spatially or temporally correlated time series. We discuss theoretically the relationship between the bivariate cross-correlation exponent and the generalized Hurst exponents for time series of respective variables. We also perform an empirical study and find that there exists a power-law cross-correlation between them, and that multifractal features are significant in all the analyzed agricultural commodity futures markets.
Khanafer, Khalil; Duprey, Ambroise; Schlicht, Marty; Berguer, Ramon
2009-04-01
Tensile tests on Polydimethylsiloxane (PDMS) materials were conducted to illustrate the effects of mixing ratio, definition of the stress-strain curve, and the strain rate on the elastic modulus and stress-strain curve. PDMS specimens were prepared according to the ASTM standards for elastic materials. Our results indicate that the physiological elastic modulus depends strongly on the definition of the stress-strain curve, mixing ratio, and the strain rate. For various mixing ratios and strain rates, true stress-strain definition results in higher stress and elastic modulus compared with engineering stress-strain and true stress-engineering strain definitions. The elastic modulus increases as the mixing ratio increases up-to 9:1 ratio after which the elastic modulus begins to decrease even as the mixing ratio continues to increase. The results presented in this study will be helpful to assist the design of in vitro experiments to mimic blood flow in arteries and to understand the complex interaction between blood flow and the walls of arteries using PDMS elastomer.
Nonlinear model calibration of a shear wall building using time and frequency data features
Asgarieh, Eliyar; Moaveni, Babak; Barbosa, Andre R.; Chatzi, Eleni
2017-02-01
This paper investigates the effects of different factors on the performance of nonlinear model updating for a seven-story shear wall building model. The accuracy of calibrated models using different data features and modeling assumptions is studied by comparing the time and frequency responses of the models with the exact simulated ones. Simplified nonlinear finite element models of the shear wall building are calibrated so that the misfit between the considered response data features of the models and the structure is minimized. A refined FE model of the test structure, which was calibrated manually to match the shake table test data, is used instead of the real structure for this performance evaluation study. The simplified parsimonious FE models are composed of simple nonlinear beam-column fiber elements with nonlinearity infused in them by assigning generated hysteretic nonlinear material behaviors to uniaxial stress-strain relationship of the fibers. Four different types of data features and their combinations are used for model calibration: (1) time-varying instantaneous modal parameters, (2) displacement time histories, (3) acceleration time histories, and (4) dissipated hysteretic energy. It has been observed that the calibrated simplified FE models can accurately predict the nonlinear structural response in the absence of significant modeling errors. In the last part of this study, the physics-based models are further simplified for casting into state-space formulation and a real-time identification is performed using an Unscented Kalman filter. It has been shown that the performance of calibrated state-space models can be satisfactory when reasonable modeling assumptions are used.
Edelaar, Lisa M; van Dieën, Jaap H; van der Esch, Martin; Roorda, Leo D; Dekker, Joost; Lems, Willem F; van der Leeden, Marike
2017-07-07
To investigate whether relationships between upper leg muscle strength and activity limitations are non-linear in patients with knee osteoarthritis, and, if so, to determine muscle strength thresholds for limitations in daily activities. Baseline data were used for 562 patients with knee osteoarthritis in the Amsterdam-Osteoarthritis cohort. Upper leg muscle strength (Nm/kg) was measured isokinetically. Activity limitations were measured with the timed Get Up and Go test and timed Stair Climb Test, subdivided into stair-ascent and stair-descent. Linear and non-linear relationships between muscle strength and activity limitations were evaluated, and thresholds were determined. Non-linear models improved model fit compared with linear models. The improvement in percentage variance accounted for was 5.9, 8.2 and 5.2 percentage points for the timed Get Up and Go, stair-ascent and stair-descent times, respectively. Muscle strength thresholds were 0.93 Nm/kg (95% confidence interval (95% CI) 0.82-1.04), 0.89 Nm/kg (95% CI 0.77-1.02) and 0.97 Nm/kg (95% CI 0.85-1.11) for relationships with timed Get Up and Go, stair-ascent and stair-descent times, respectively. In patients with knee osteoarthritis, relationships between muscle strength and activity limitations are non-linear. Patients with muscle strength below the described thresholds might benefit more from muscle strength training to reduce limitations in daily activities than would patients with muscle strength above the thresholds. Further research is needed to assess the clinical value of the thresholds determined.
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Mendel Friedman
2013-08-01
Full Text Available Aflatoxin-producing fungi contaminate food and feed during pre-harvest, storage and processing periods. Once consumed, aflatoxins (AFs accumulate in tissues, causing illnesses in animals and humans. Most human exposure to AF seems to be a result of consumption of contaminated plant and animal products. The policy of blending and dilution of grain containing higher levels of aflatoxins with uncontaminated grains for use in animal feed implicitly assumes that the deleterious effects of low levels of the toxins are linearly correlated to concentration. This assumption may not be justified, since it involves extrapolation of these nontoxic levels in feed, which are not of further concern. To develop a better understanding of the significance of low dose effects, in the present study, we developed quantitative methods for the detection of biologically active aflatoxin B1 (AFB1 in Vero cells by two independent assays: the green fluorescent protein (GFP assay, as a measure of protein synthesis by the cells, and the microculture tetrazolium (MTT assay, as a measure of cell viability. The results demonstrate a non-linear dose-response relationship at the cellular level. AFB1 at low concentrations has an opposite biological effect to higher doses that inhibit protein synthesis. Additional studies showed that heat does not affect the stability of AFB1 in milk and that the Vero cell model can be used to determine the presence of bioactive AFB1 in spiked beef, lamb and turkey meat. The implication of the results for the cumulative effects of low amounts of AFB1 in numerous foods is discussed.
Zheng, Dingchang; Murray, Alan
2009-05-29
Arterial wall function is associated with different physiological and clinical factors. Changes in arterial pressure cause major changes in the arterial wall. This study presents a simple non-invasive method to quantify arterial volume distensibility changes with different arterial pressures. The electrocardiogram, finger and ear photoplethysmogram were recorded from 15 subjects with the right arm at five different positions (90 degrees , 45 degrees , 0 degrees , -45 degrees and -90 degrees referred to the horizontal level). Arm pulse propagation time was determined by subtracting ear pulse transit time from finger pulse transit time, and was used to obtain arterial volume distensibility. The mean arterial blood pressure with the arm at the horizontal level was acquired, and changes with position were calculated using the hydrostatic principle that blood pressure in the arm is linearly related to its vertical distance from the horizontal level. The mean arm pulse propagation times for the five different positions were 88, 72, 57, 54 and 52ms, with the corresponding mean arterial volume distensibility of 0.234%, 0.158%, 0.099%, 0.088% and 0.083% per mmHg. For all consecutive changes in arm position, arm pulse propagation time and arterial volume distensibility, were significantly different (all probability Ppressure decreased significantly between each consecutive arm position from 90 degrees to -45 degrees (all Ppressure changes from 101 to 58mmHg. In conclusion, the inverse and non-linear relationship between arterial volume distensibility and arterial pressure has been quantified using a simple arm positioning procedure, with the greatest effect at low pressures. This work is an important step in developing a simple non-invasive technique for assessing peripheral arterial volume distensibility.
Institute of Scientific and Technical Information of China (English)
周里群; 邓晶; 周凯; 李玉平
2011-01-01
Hill localized instability theory was used to derive the stress-strain equations of nickel coating sheet during forming process.By using polynomial fitting for experimental data,actual stress-strain curves of the electrodeposited nickel coating sheet were obtained.The forming limit left region of the nickel coating sheet was calculated by solving a nonlinear equation,and compared with one by using strain hardening curves.The research results show that the forming limit of the nickel coating by polynomial fitting is higher in security than the one by strain hardening curves,and the substrate anisotropy,coating thickness and substrate thickness have little influences on the formed limit curves.The results may play a directive role on the electrodeposited nickel coating sheet preparation.%基于Hill集中失稳理论推导出了冲压成形过程中涂层与基体的应力-应变方程,通过求解非线性方程计算出各主应变。依据实验数据采用多项式拟合法拟合了材料的应力-应变曲线,对电沉积镍涂层的冲压成形极限的左边进行了计算,并和应变硬化曲线求得的成形极限进行了比较。计算结果表明,用多项式拟合法求得的电沉积镍涂层的成形极限安全区域比用应变硬化曲线求得的安全区域要高,基体厚向异性、涂层厚度和基体厚度对板料成形极限左边影响不大。
Institute of Scientific and Technical Information of China (English)
Chen Lianwang; Yang Shuxin; Xie Furen; Lu Yuanzhong; Guo Ruomei
2006-01-01
Based on the active crustal block structures, the Holocene active faults and the wave velocity structures with a resolution of 1°× 1°, a two-dimensional finite element model for the tectonic stress-strain field of the Chinese mainland is constructed in the paper. Using GPS measurements, the velocity boundary conditions for the model are deduced, then, the annual change patterns of the present-day stress-strain field of the Chinese mainland are simulated.The results show that (1) the general pattern of the recent tectonic deformation in the Chinese mainland is governed by the interactions of its surrounding plates, of which, the Indian Plate plays a major role. There is a NNE-directed velocity distribution in the west of the Chinese mainland. The maximum slip rate appears at the collision boundary. The north-directed components decrease, while the east-directed components increase gradually from south to north and from west to east. In the east part, there is a general east-directed movement, with a certain amount of south-directed components. (2) The present-day tectonic stress field in the Chinese mainland has undergone the process of enhancement in recent years, and this process presents a general pattern of radiating eastwards from the Qinghai-Xizang (Tibet) Plateau as the center. The general pattern is similar to the ambient tectonic stress field, indicating the inheritance of contemporary tectonic deformation on the Chinese mainland. (3) The maximum principal strain presents an obvious pattern of being high in the west and low in the east. The tectonic movement in the west is stronger than that in the east. Large active faults are all located in the high-value zones of maximum principal strain. However, the magnitude of strain is smaller in the interior of the active crustal blocks, which are enclosed by these faults. (4) The stress-strain field of the Sichuan-Yunnan region is unique. It may not be governed by collision of plates alone but a combination of
应变计组的应力应变转换%Stress-strain conversion of strain gauge set
Institute of Scientific and Technical Information of China (English)
黄浩
2014-01-01
为提高应力应变转换最终应力结果的准确度，根据应力应变转换的一般步骤，分析了其中基准时间选取、无应力计可靠性分析、徐变参数公式拟合、应力增量加载方式和应变计组平衡等关键问题，结果表明：基准时间选取缺少一个科学合理的定量原则；无应力计可靠性分析缺少一个可行的分析评判准则；徐变参数公式拟合应该采用全局优化算法；应力增量加载方式应该采用中点瞬时加载终点结束，得到终点时刻应力的方式；对于应变计组平衡问题，基于概率论将平衡问题转化成最优化问题，提出了最优化平衡法，数学实验结果证明该方法是一种科学合理的平衡方法。%In order to improve the accuracy of the final stress result in stress-strain conversion , we analyze some key problems , including the reference time selection , non-stress gauge reliability , formula fitting of creep parameters , stress increment loading mode , and strain gauge set balance , according to general steps of stress-strain conversion .The analysis results show that the reference time selection lacks a scientific and reasonable quantitative principle, the non-stress strain gauge reliability analysis lacks a feasible evaluation criterion , the formula fitting of creep parameters requires a global optimization algorithm , and the stress increment loading mode requires instantaneous loading at the midpoint and ending at the endpoint .Meanwhile , based on the probability theory , the problem of strain gauge set balance is transformed into an optimization problem , and an optimization balance method is put forward , and proven to be scientific and reasonable through a mathematical experiment .
Shmakov, A. F.; Modorskii, V. Ya.
2016-10-01
This paper presents the results of numerical modeling of gas-dynamic processes occurring in the flow path, thermal analysis and evaluation of the stress-strain state of a three-stage design of the compressor gas pumping unit. Physical and mathematical models of the processes developed. Numerical simulation was carried out in the engineering software ANSYS 13. The problem is solved in a coupled statement, in which the results of the gas-dynamic calculation transferred as boundary conditions for the evaluation of the thermal and stress-strain state of a three-stage design of the compressor gas pumping unit. The basic parameters, which affect the stress-strain state of the housing and changing gaps of labyrinth seals in construction. The method of analysis of the pumped gas flow influence on the strain of construction was developed.
Nonlinear Elastic Deformation of Thin Composite Shells of Discretely Variable Thickness
Lutskaya, I. V.; Maksimyuk, V. A.; Storozhuk, E. A.; Chernyshenko, I. S.
2016-11-01
A method for analyzing the stress-strain state of nonlinear elastic orthotropic thin shells with reinforced holes and shells of discretely variable thickness is developed. The reference surface is not necessarily the midsurface. The constitutive equations are derived using Lomakin's theory of anisotropic plasticity. The methods of successive approximations and variational differences are used. The Kirchhoff-Love hypotheses are implemented using Lagrange multipliers. The method allows analyzing the stress-strain state of shells with arbitrarily varying thickness and ribbed shells. The numerical results are presented in the form of tables and analyzed
THE CALCULATION OF STRESS-STRAIN STATE OF THREE-LAYER BEAM TAKING INTO ACCOUNT EDGE EFFECTS
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Kh. M. Muselemov
2015-01-01
Full Text Available The work is dedicated to the calculation of the stress-strain state (SSS of the three-layer beam (TLB subject to boundary effects.In this paper, a system of differential equations of equilibrium of the threelayer beam. To solve these equations, it is necessary to know the 12 boundary conditions, co-which depend on support conditions and loading of sandwich beams under study. This system of equations is solved by the application package of mathematical modeling "Maple 5.4." The solution of this system we obtain expressions for determining de-formations and stress all components (bearing layers and filler, a three-layer beam anywhere under specified conditions of fastening the ends of the beam and its loading.
Mathematical modeling of the stress-strain state of the outlet guide vane made of various materials
Grinev, M. A.; Anoshkin, A. N.; Pisarev, P. V.; Zuiko, V. Yu.; Shipunov, G. S.
2016-11-01
The present work is devoted to the detailed stress-strain analysis of the composite outlet guide vane (OGV) for aircraft engines with a special focus on areas with twisted layers where the initiation of high interlaminar stresses is most expected. Various polymer composite materials and reinforcing schemes are researched. The technological scheme of laying-out of anisotropic plies and the fastening method are taken into account in the model. The numerical simulation is carried out by the finite element method (FEM) with the ANSYS Workbench software. It is shown that interlaminar shear stresses are most dangerous. It is found that balanced carbon fiber reinforced plastic (CFRP) with the [0°/±45°] reinforcing scheme allows us to provide the double strength margin under working loads for the developed OGV.
Meng, Yi; Yi, Weijian
2011-06-01
Polyvinylidene fluoride (PVDF) piezoelectric material has been successfully applied in many engineering fields and scientific research. However, it has rarely been used for direct measurement of concrete stresses under impact loading. In this paper, a new PVDF-based stress gauge was developed to measure concrete stresses under impact loading. Calibrated on a split Hopkinson pressure bar (SHPB) with a simple measurement circuit of resistance strain gauges, the PVDF gauge was then used to establish dynamic stress-strain curves of concrete cylinders from a series of axial impact testing on a drop-hammer test facility. Test results show that the stress curves measured by the PVDF-based stress gauges are more stable and cleaner than that of the stress curves calculated with the impact force measured from a load cell.
Lyukshin, P. A.; Bochkareva, S. A.; Grishaeva, N. Yu.; Lyukshin, B. A.; Matolygina, N. Yu.; Panin, S. V.
2016-11-01
Thermal barrier coatings (TBC) are aimed at protection of machine parts working under extremely high temperatures. One of the major problems at their exploitation is related to delamination of the coating from the substrate. In this concern, investigation of the patterns and evolution of the stress-strain state (SSS) at their interface is of particular interest. The main reasons of the delamination are associated with the distinction of thermo-physical properties (first of all, thermal expansion coefficient) of the interfaced material, as well as by the difference in heating conditions (heat supply and abstraction). The latter is of particular importance when the transient regimes take place under the heat impact, i.e. the TBC becomes rapidly heated, while the substrate has much lower temperature. In order to analyze and simulate the processes that give rise to the delamination, a number of problems is to be solved. At the first stage, the temperature variation induced by the thermal impact both in the coating and the substrate is to be determined. At the second stage, the distribution of the Stress Strain State (SSS) in the coating and the substrate are to be found. Based on the values of the calculated stresses, the stability loss patterns of the coating might be revealed. In doing so, the latter is regarded as a plate rested on Winkler elastic foundation. By defining the plate deflections in concern of its interaction with the substrate, the distribution of the SSS parameters at the contact surface can be found. Finally, the conditions to determine the TBC delamination from the substrate are estimated.
Directory of Open Access Journals (Sweden)
Gonzalez Cezar Henrique
2004-01-01
Full Text Available Recently, electrical resistivity (ER measurements have been done during some thermomechanical tests in copper based shape memory alloys (SMA's. In this work, single crystals of Cu-based SMA's have been studied at different temperatures to analyse the relationship between stress (s and ER changes as a function of the strain (e. A good consistency between ER change values is observed in different experiments: thermal martensitic transformation, stress induced martensitic transformation and stress induced reorientation of martensite variants. During stress induced martensitic transformation (superelastic behaviour and stress induced reorientation of martensite variants, a linear relationship is obtained between ER and strain as well as the absence of hys teresis. In conclusion, the present results show a direct evidence of martensite electrical resistivity anisotropy.
FINITE ELEMENT FOR STRESS-STRAIN STATE MODELING OF TWO-LAYERED AXIALLY SYMMETRIC SHELLS
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K. S. Kurochka
2015-07-01
Full Text Available Subject of Research. Computation of composite material designs requires application of numerical methods. The finiteelement method usage is connected with surface approximation problems. Application of volumetric and laminar elements leads to systems with large sizes and a great amount of computation. The objective of this paper is to present an equivalent two-layer mathematical model for evaluation of displacements and stresses of cross-ply laminated cone shells subjected to uniformly distributed load. An axially symmetric element for shell problems is described. Method. Axially symmetric finite element is proposed to be applied in calculations with use of correlation for the inner work of each layer separately. It gives the possibility to take into account geometric and physical nonlinearities and non-uniformity in the layers of the shell. Discrete mathematical model is created on the base of the finite-element method with the use of possible motions principle and Kirchhoff–Love assumptions. Hermite element is chosen as a finite one. Cone shell deflection is considered as the quantity sought for. Main Results. One-layered and two-layered cone shells have been considered for proposed mathematical model verification with known analytical and numerical analytical solutions, respectively. The axial displacements of the two-layered cone are measured with an error not exceeding 5.4 % for the number of finite elements equal to 30. The proposed mathematical model requires fewer nodes to define the finite element meshing of the system and much less computation time. Thereby time for finding solution decreases considerably. Practical Relevance. Proposed model is applicable for computation of multilayered designs under axially symmetric loads: composite high-pressure bottles, cylinder shaped fiberglass pipes, reservoirs for explosives and flammable materials, oil and gas storage tanks.
Konovalov, I B
2002-01-01
The nonlinear features of the relationships between particulate matter (PM) and volatile organic compounds (VOC) and oxides of nitrogen (NOx) are derived directly from data of long-term routine measurements of NOx, VOC, and total suspended PM. The main idea of the method used for the analysis is creation of special empirical models based on artificial neural networks of the perceptron type. These models which are in essence the nonlinear extension of commonly used linear regression models are believed to provide the best fit for the real nonlinear PM-NOx-VOC relationships under different observed levels of air pollution and various meteorological conditions. It is believed that such models may be useful in context of various scientific and practical problems concerning PM. The method is demonstrated by the example of two empirical models created with independent data-sets collected at two air quality monitoring stations at South Coast Air Basin, California. It is shown that in spite of considerable distance b...
McDonald, Alison C; Sanei, Kia; Keir, Peter J
2013-06-01
Muscle force estimates are important for full understanding of the musculoskeletal system and EMG is a modeling method used to estimate muscle force. The purpose of this investigation was to examine the effect of high pass filtering and non-linear normalization on the EMG-force relationship of sub-maximal finger exertions. Sub-maximal isometric ramp exertions were performed under three conditions (i) extension with restraint at the mid-proximal phalanx, (ii) flexion at the proximal phalanx and (iii) flexion at the distal phalanx. Thirty high pass filter designs were compared to a standardized processing procedure and an exponential fit equation was used for non-linear normalization. High pass filtering significantly reduced the %RMS error and increased the peak cross correlation between EMG and force in the distal flexion condition and in the other two conditions there was a trend towards improving force predictions with high pass filtering. The degree of linearity differed between the three contraction conditions and high pass filtering improved the linearity in all conditions. Non-linear normalization had greater impact on the EMG-force relationship than high pass filtering. The difference in optimal processing parameters suggests that high pass filtering and linearity are dependent on contraction mode as well as the muscle analyzed.
Energy Technology Data Exchange (ETDEWEB)
Kim, Sei-wan [Department of Economics, Ewha Womans University, Seoul (Korea, Republic of); Lee, Kihoon, E-mail: khl@cnu.ac.k [Department of Economics, Chungnam National University, Daejeon (Korea, Republic of); Nam, Kiseok [Sy Syms School of Business, Yeshiva University, New York, NY 10033 (United States)
2010-10-15
Using STAR models, we investigate the nonlinear dynamic properties and the interdependence of CO{sub 2} emissions and economic growth for Korea. The estimation results indicate that the growth rate of both CO{sub 2} emissions and industrial production exhibit a significant nonlinear asymmetric dynamics. While the linear Granger causality test finds no causality in any direction, the results of the nonlinear Granger causality tests show a two-way causality between CO{sub 2} emissions and economic growth. The strong mutual causation between CO{sub 2} emissions and economic activities indicates that the economic impact from CO{sub 2} mitigation is expected to be higher in Korea. This suggests that the appropriate energy and environmental policy be to mitigate CO{sub 2} emissions while having less impact on the economy.
Energy Technology Data Exchange (ETDEWEB)
Kim, Sei-wan [Department of Economics, Ewha Womans University, Seoul (Korea); Lee, Kihoon [Department of Economics, Chungnam National University, Daejeon (Korea); Nam, Kiseok [Sy Syms School of Business, Yeshiva University, New York, NY 10033 (United States)
2010-10-15
Using STAR models, we investigate the nonlinear dynamic properties and the interdependence of CO{sub 2} emissions and economic growth for Korea. The estimation results indicate that the growth rate of both CO{sub 2} emissions and industrial production exhibit a significant nonlinear asymmetric dynamics. While the linear Granger causality test finds no causality in any direction, the results of the nonlinear Granger causality tests show a two-way causality between CO{sub 2} emissions and economic growth. The strong mutual causation between CO{sub 2} emissions and economic activities indicates that the economic impact from CO{sub 2} mitigation is expected to be higher in Korea. This suggests that the appropriate energy and environmental policy be to mitigate CO{sub 2} emissions while having less impact on the economy. (author)
Quantifying Grain Level Stress-Strain Behavior for AM40 via Instrumented Microindentation
Energy Technology Data Exchange (ETDEWEB)
Cheng, Guang; Barker, Erin I.; Stephens, Elizabeth V.; Choi, Kyoo Sil; Sun, Xin
2016-01-13
Nanoindentation is performed on hot isostatic pressing (HIP) Mg-Al (AM40) alloy samples prepared from high-pressure die cast (HPDC) for the purpose of characterizing the mechanical properties of the α-grains. Extracting elastic modulus and hardness from resulting load-depth curves is well established. A new inverse method is developed to extract plastic material properties as well. The method utilizes empirical yield strength-hardness relationship reported in the literature with finite element modeling of the indentation. Due to the shallow depth of the indentation, indentation size effect (ISE) is taken into account when determine plastic properties. Elastic and plastic properties are determined for a series of indents. The resulting average values and standard deviation are calculated for use as input distributions for microstructure modeling of the AM40.
Energy Technology Data Exchange (ETDEWEB)
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.
Finger, R. W.
1978-01-01
Static fracture tests were performed on surface flawed specimens of aluminum and titanium alloys. A simulated proof overload cycle was applied prior to all of the cyclic tests. Variables included in each test series were flaw shapes and thickness. Additionally, test temperature was a variable for the aluminum test series. The crack opening displacement and stress-strain data obtained are presented.
Impact of weightlessness on cardiac shape and left ventricular stress/strain distributions.
Iskovitz, Ilana; Kassemi, Mohammad; Thomas, James D
2013-12-01
In this paper, a finite element model of the heart is developed to investigate the impact of different gravitational loadings of Earth, Mars, Moon, and microgravity on the cardiac shape and strain/stress distributions in the left ventricle. The finite element model is based on realistic 3D heart geometry, detailed fiber/sheet micro-architecture, and a validated orthotropic cardiac tissue model and constitutive relationship that capture the passive behavior of the heart at end-diastole. The model predicts the trend and magnitude of cardiac shape change at different gravitational levels with great fidelity in comparison to recent cardiac sphericity measurements performed during simulated reduced-gravity parabolic flight experiments. Moreover, the numerical predictions indicate that although the left ventricular strain distributions remain relatively unaltered across the gravitational fields and the strain extrema values occur at the same relative locations, their values change noticeably with decreasing gravity. As for the stress, however, both the magnitude and location of the extrema change with a decrease in the gravitational field. Consequently, tension regions of the heart on Earth can change into compression regions in space.
Prediction of stress-strain state of municipal solid waste with application of soft soil creep model
Directory of Open Access Journals (Sweden)
Ofrikhter Vadim Grigor'evich
Full Text Available The deformation of municipal solid waste is a complex process caused by the nature of MSW, the properties of which differ from the properties of common soils. The mass of municipal solid waste shows the mixed behaviour partially similar to granular soils, and partially - to cohesive. So, one of mechanical characteristics of MSW is the cohesion typical to cohesive soils, but at the same time the filtration coefficient of MSW has an order of 1 m/day that is characteristic for granular soils. It has been established that MSW massif can be simulated like the soil reinforced by randomly oriented fibers. Today a significant amount of the verified and well proved software products are available for numerical modelling of soils. The majority of them use finite element method (FEM. The soft soil creep model (SSC-model seems to be the most suitable for modelling of municipal solid waste, as it allows estimating the development of settlements in time with separation of primary and secondary consolidation. Unlike the soft soil, one of the factors of secondary consolidation of MSW is biological degradation, the influence of which is possible to consider at the definition of the modified parameters essential for soft soil model. Application of soft soil creep model allows carrying out the calculation of stress-strain state of waste from the beginning of landfill filling up to any moment of time both during the period of operation and in postclosure period. The comparative calculation presented in the paper is executed in Plaxis software using the soft-soil creep model in contrast to the calculation using the composite model of MSW. All the characteristics for SSC-model were derived from the composite model. The comparative results demonstrate the advantage of SSC-model for prediction of the development of MSW stress-strain state. As far as after the completion of the biodegradation processes MSW behaviour is similar to cohesion-like soils, the demonstrated
Zhu, H.; Shan, G. C.; Shek, C. H.; Lee, J. E.-Y.
2012-07-01
The frequency response of a single crystal silicon resonator under nonlinear vibration is investigated and related to the shear property of the material. The shear stress-strain relation of bulk silicon is studied using a first-principles approach. By incorporating the calculated shear property into a device-level model, our simulation closely predicts the frequency response of the device obtained by experiments and further captures the nonlinear features. These results indicate that the observed nonlinearity stems from the material's mechanical property. Given the high quality factor (Q) of the device reported here (˜2 × 106), this makes it highly susceptible to such mechanical nonlinear effects.
Institute of Scientific and Technical Information of China (English)
孙志刚; 苗艳; 宋迎东
2012-01-01
提出了蒙特卡罗方法模拟陶瓷基复合材料基体随机开裂过程,采用剪滞模型描述了复合材料出现损伤时细观应力场,并推导得到了考虑基体开裂时复合材料拉伸应力-应变曲线计算公式.开展了室温环境下C/SiC复合材料的单轴拉伸试验,并将理论预测应力-应变曲线与试验结果进行对比.同时,采用该方法对SiC/CAS,SiC/Si3N4复合材料应力-应变曲线进行了模拟,并与国外提供的相关试验数据进行比较,发现两者吻合得较好,从而证实了蒙特卡罗法可有效地模拟考虑基体随机开裂过程的陶瓷基复合材料应力-应变曲线.此外,还分析了Weibull模量、残余热应力和初始开裂应力对应力-应变曲线的影响.研究表明：Weibull模量越大,应力-应变曲线非线性越明显;热残余应力越大,应力-应变曲线偏转越早,非线性越明显;初始开裂应力与Weibull模量对应力-应变曲线影响规律相似.%The matrix random cracking of ceramic matrix composite was simulated by Montel Carlo model.The shear-lag model was used to analyze the micro-stress field of the damaged composites,and the formula of the stress-strain behavior was derived.The uniaxial tensile experiment of unidirectional-C/SiC composites at ambient temperature has been performed,and the simulated stress-strain curve was compared to the experimental data.The tensile stress-strain curves of SiC/CAS and SiC/Si3N4 composites were simulated,which agreed well with the related experimental results.Besides,infuence of the model parameters on stress-strain curve was analyzed.Research shows that the higher the Weibull modulus,the more evident the non-linear phenomenon;the higher the thermal residual stress,the earlier the non-linear phenomenon appears;the effect of the minimum cracking stress on the stress-strain is similar to the effect of the Weibull modulus;the Monte Carlo model can simulate the stress-strain curve of ceramic matrix composites
Directory of Open Access Journals (Sweden)
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.
Directory of Open Access Journals (Sweden)
Francisca Guadalupe Cabrera-Covarrubias
2016-12-01
Full Text Available The difficult current environmental situation, caused by construction industry residues containing ceramic materials, could be improved by using these materials as recycled aggregates in mortars, with their processing causing a reduction in their use in landfill, contributing to recycling and also minimizing the consumption of virgin materials. Although some research is currently being carried out into recycled mortars, little is known about their stress-strain (σ-ε; therefore, this work will provide the experimental results obtained from recycled mortars with recycled ceramic aggregates (with contents of 0%, 10%, 20%, 30%, 50% and 100%, such as the density and compression strength, as well as the σ-ε curves representative of their behavior. The values obtained from the analytical process of the results in order to finally obtain, through numerical analysis, the equations to predict their behavior (related to their recycled content are those of: σ (elastic ranges and failure maximum, ε (elastic ranges and failure maximum, and Resilience and Toughness. At the end of the investigation, it is established that mortars with recycled ceramic aggregate contents of up to 20% could be assimilated just like mortars with the usual aggregates, and the obtained prediction equations could be used in cases of similar applications.
Liu, Jinfeng; Fokker, Peter; Spiers, Christopher
2016-04-01
Permeability evolution in coal reservoirs during CO2-Enhanced Coalbed Methane (ECBM) production is strongly influenced by swelling/shrinkage effects related to sorption and desorption of CO2 and CH4, respectively. Numerous permeability models, coupling the swelling response of coal to gas sorption, have been developed to predict in-situ coal seam permeability evolution during (E)CBM. However, experimental studies, aimed at testing such models, have mainly focused on the permeability changes occurring under constant lateral stress conditions, which are inconsistent with the in-situ boundary condition of (near) zero lateral strain. We performed CH4 permeability measurements, using the steady-state method, on a cylindrical sample of high volatile bituminous coal (25mm in diameter), under (near) fixed volume versus fixed stress conditions. The sample possessed a clearly visible cleat system. To isolate the effect of sorption on permeability evolution, helium (non-sorbing gas) was used as a control fluid. The bulk sample permeability to helium, under stress control conditions, changed from 4.07×10-17to 7.5×10-18m2, when the effective stress increased from 19.1 to 35.2MPa. Sorption of CH4 at a constant pressure of 10MPa, under fixed volume boundary conditions, resulted in a confining pressure increase from a poroelastically supported value of 29.3MPa to a near-equilibrium value of 38.6MPa over 171 hours. This is caused by the combined effect of the sorption-induced swelling and the self-compression of the sample. The concentration of CH4 adsorbed by the sample was 0.113 mmol/gcoal. During the adsorption process, the permeability to CH4 also decreased from 2.38×10-17 to 4.91×10-18m2, proving a strong influence of stress-strain-sorption behavior (c.f. Hol et al., 2012) on fracture permeability evolution. The CH4 permeability subsequently measured under stress controlled conditions varied from 1.37×10-17 to 4.33×10-18m2, for same change in confining pressure, i.e. 28
Energy Technology Data Exchange (ETDEWEB)
Drofenik, U.; Kovacevic, I.; Kolar, J. W. [Swiss Federal Institute of Technology, Power Electronic Systems Laboratory, Zuerich (Switzerland); Schmidt, R. [ABB Switzerland Ltd., Corporate Research, Baden-Daettwil (Switzerland)
2008-07-01
For lifetime estimation of power converters in traction applications, one method is to calculate numerically the stress-strain hysteresis curves of the interfaces silicon-solder-DCB and/or DCB-solder-baseplate inside the power modules. This can only be achieved if the transient junction temperatures in these layers are known for a defined mission profile. Therefore, one has to couple circuit simulation with thermal simulation and stress-strain computation. The second challenge of this problem is to perform this transient simulation taking into account switching losses in the {mu}s-range for mission profiles over a couple of minutes. In this paper we employ a new multi-domain simulation software to achieve results with reasonable computational effort. (author)
3D Stress-Strain Analysis of a Failed Limestone Wedge Influenced by an Intact Rock Bridge
Paronuzzi, Paolo; Bolla, Alberto; Rigo, Elia
2016-08-01
This paper presents a back-analysis of a rock wedge failure (volume = 25-30 m3) that involved a limestone scarp in the Rosandra valley (Trieste karst, NE Italy). Thanks to the mechanical survey of the detachment surface, a single rock bridge having a size of about 15 cm × 30 cm has been ascertained. A 3D stress-strain analysis has been performed to examine the influence of the rock bridge on the block stability (initial unweathered condition: strength reduction factor SRF equal to 1.14). The shear strength provided by the basal and lateral joints represents the main contributing factor for the wedge stability (about 60-75 % of the whole resisting system). However, the equilibrium of the wedge was temporarily attained thanks to the strength contribution provided by the rock bridge (25-40 %) until the acting forces locally exceeded the resisting forces, thus determining the bridge rupture and, as a consequence, the wedge collapse. The mean shear stress acting on the rock bridge at failure ranges from about 3.5 to 5 MPa. Calculated block displacements up to failure vary from 0.6 to 1.5 mm, depending on the different elastic modulus assumed for the wedge ( E = 30, 10, and 4 GPa). Pre-collapse block displacements increase as a result of the shear strength decrease that was initially caused by the weathering of the delimiting rock joints and, further, by the progressive failure of the rock bridge. The cohesion at failure of the rock bridge ranges from 2.1 to 2.6 MPa (friction angle of intact rock φ = 40°).
Wang, Lu; Liu, Hongji; Li, Fanzhu; Shen, Jianxiang; Zheng, Zijian; Gao, Yangyang; Liu, Jun; Wu, Youping; Zhang, Liqun
2016-10-05
Although numerous research studies have been focused on studying the self-assembled morphologies of block-copolymers (BCPs) and their nanocomposites, little attention has been directed to explore the relation between their ordered structures and the resulting mechanical properties. We adopt coarse-grained molecular dynamics simulation to study the influence of the morphologies on the stress-strain behavior of pure block copolymers and block copolymers filled with uniform or Janus nanoparticles (NPs). At first, we examine the effect of the arrangement (di-block, tri-block, alternating-block) and the components of the pure block copolymers, and by varying the component ratio between A and B blocks, spherical, cylindrical and lamellar phases are all formed, showing that spherical domains bring the largest reinforcing effect. Then by studying BCPs filled with NPs, the Janus NPs induce stronger bond orientation of polymer chains and greater mechanical properties than the uniform NPs, when these two kinds of NPs are both located in the interface region. Meanwhile, some other anisotropic Janus NPs, such as Janus rods and Janus sheets, are incorporated to examine the effect on the morphology and the stress-strain behavior. These findings deepen our understanding of the morphology-mechanics relation of BCPs and their nanocomposites, opening up a vast number of approaches such as designing the arrangement and components of BCPs, positioning uniform or Janus NPs with different shapes and shear flow to tailor their stress-strain performance.
Directory of Open Access Journals (Sweden)
mossayeb dalvand
2017-08-01
Full Text Available In this study 3D stress-strain distribution of dowel and glue line on L-type joints made of plywood doweled was investigated. Members of joints made of 11-ply hardwood plywood (Hornbeam, Beech and Alder that were 19 mm in thickness. In this study effect of beech dowels in three levels diameters (6, 8 and 10 mm and penetration of depth (9, 13 and 17 mm on bending moment capacity of L-type joints under compression loading was investigated as experimental test, then stress-strain distribution of wood dowel and glue line in specimens were simulated by means of ANSYS 15 software with finite element method (FEM.Results have shown that bending moment resistance increased with increasing dowel diameter from 6 to 8 mm, but downward trend was observed with increasing 8 to 10 mm in dowel diameter. Bending moment resistance increased with increasing penetration depth. Also, result obtained of simulation by means of ANSYS software have shown that stress-strain in dowel and glue line increased with increasing diameter of dowel and Increasing stress in joints made of diameter dowel 10 mm due to fracture in joints and decrease in resistance once. According to results obtained of model analysis, the ultimate stress of dowel and glue line occurred in the area that joints were contacted.
Directory of Open Access Journals (Sweden)
Thiyanga Talagala
2015-12-01
Full Text Available Dengue fever and its more severe deadly complication dengue hemorrhagic fever is an infectious mosquito borne disease. The rise in dengue fever has made a heavy economic burden to the country. Climate variability is considered as the major determinant of dengue transmission. Sri Lanka has a favorable climatic condition for development and transmission of dengue. Hence the aim of this study is to estimate the effect of diverse climatic variables on the transmission of dengue while taking the lag effect and nonlinear effect into account. Weekly data on dengue cases were obtained from January, 2009 to September, 2014. Temperature, precipitation, visibility, humidity, and wind speed were also recorded as weekly averages. Poisson regression combined with distributed lag nonlinear model was used to quantify the impact of climatic factors. Results of DLNM revealed; Mean Temperature 250C – 270C at lag 1 – 8 weeks, Precipitation higher than 70mm at lag 1- 5 weeks and 20- 50mm at lag 10 – 20 weeks, humidity ranged from 65% to 80% at lag 10 – 18 weeks, visibility greater than 14 km have a positive impact on the occurrence of dengue incidence while, mean temperature higher than 280C at lag 6 – 25 weeks, maximum temperature at lag 4 – 6 weeks, precipitation higher than 65mm at lag 15 – 20 weeks, humidity less than 70% at lag 4 – 9 weeks, visibility less than 14km, high wind speed have a negative impact on the occurrence of dengue incidence. These findings can aid the targeting of vector control interventions and the planning for dengue vaccine implementation.
Hemmateenejad, Bahram; Shamsipur, Mojtaba; Miri, Ramin; Elyasi, Maryam; Foroghinia, Farzaneh; Sharghi, Hashem
2008-03-03
A quantitative structure-property relation (QSPR) study was conducted on the solubility in supercritical fluid carbon dioxide (SCF-CO2) of some recently synthesized anthraquinone, anthrone and xanthone derivatives. The data set consisted of 29 molecules in various temperatures and pressures, which form 1190 solubility data. The combined data splitting-feature selection (CDFS) strategy, which previously developed in our research group, was used as descriptor selection and model development method. Modeling of the relationship between selected molecular descriptors and solubility data was achieved by linear (multiple linear regression; MLR) and nonlinear (artificial neural network; ANN) methods. The QSPR models were validated by cross-validation as well as application of the models to predict the solubility of three external set compounds, which did not have contribution in model development steps. Both linear and nonlinear methods resulted in accurate prediction whereas more accurate results were obtained by ANN model. The respective root mean square error of prediction obtained by MLR and ANN models were 0.284 and 0.095 in the term of logarithm of g solute m(-3) of SCF-CO2. A comparison was made between the models selected by CDFS method and the conventional stepwise feature selection method. It was found that the latter produced models with higher number of descriptors and lowered prediction ability, thus it can be considered as an over-fitted model.
Design of materials with prescribed nonlinear properties
DEFF Research Database (Denmark)
Wang, Fengwen; Sigmund, Ole; Jensen, Jakob Søndergaard
2014-01-01
We systematically design materials using topology optimization to achieve prescribed nonlinear properties under finite deformation. Instead of a formal homogenization procedure, a numerical experiment is proposed to evaluate the material performance in longitudinal and transverse tensile tests un....... The numerical examples illustrate optimized materials with rubber-like behavior and also optimized materials with extreme strain-independent Poisson's ratio for axial strain intervals of εi ∈ [0.00,0.30]. © 2014 Elsevier Ltd. All rights reserved....... under finite deformation, i.e. stress-strain relations and Poisson's ratio. By minimizing errors between actual and prescribed properties, materials are tailored to achieve the target. Both two dimensional (2D) truss-based and continuum materials are designed with various prescribed nonlinear properties...
Breakdown of nonlinear elasticity in stress-controlled thermal amorphous solids
Dailidonis, Vladimir; Ilyin, Valery; Procaccia, Itamar; Shor, Carmel A. B. Z.
2017-03-01
In recent work it was clarified that amorphous solids under strain control do not possess nonlinear elastic theory in the sense that the shear modulus exists but nonlinear moduli exhibit sample-to-sample fluctuations that grow without bound with the system size. More relevant, however, for experiments are the conditions of stress control. In the present Rapid Communication we show that also under stress control the shear modulus exists, but higher-order moduli show unbounded sample-to-sample fluctuation. The unavoidable consequence is that the characterization of stress-strain curves in experiments should be done with a stress-dependent shear modulus rather than with nonlinear expansions.
Molenaar, P.C.M.; Raijmakers, M.E.J.
2000-01-01
It is shown that the Piagetian model of stagewise cognitive development can be assigned a powerful causal interpretation in terms of self-organizing epigenetic processes. A detailed heuristic explanation is given of self-organizing epigenetics. In addition, the relationships between self-organizing
Gonçalves, M A D; Bello, N M; Dritz, S S; Tokach, M D; DeRouchey, J M; Woodworth, J C; Goodband, R D
2016-05-01
Advanced methods for dose-response assessments are used to estimate the minimum concentrations of a nutrient that maximizes a given outcome of interest, thereby determining nutritional requirements for optimal performance. Contrary to standard modeling assumptions, experimental data often present a design structure that includes correlations between observations (i.e., blocking, nesting, etc.) as well as heterogeneity of error variances; either can mislead inference if disregarded. Our objective is to demonstrate practical implementation of linear and nonlinear mixed models for dose-response relationships accounting for correlated data structure and heterogeneous error variances. To illustrate, we modeled data from a randomized complete block design study to evaluate the standardized ileal digestible (SID) Trp:Lys ratio dose-response on G:F of nursery pigs. A base linear mixed model was fitted to explore the functional form of G:F relative to Trp:Lys ratios and assess model assumptions. Next, we fitted 3 competing dose-response mixed models to G:F, namely a quadratic polynomial (QP) model, a broken-line linear (BLL) ascending model, and a broken-line quadratic (BLQ) ascending model, all of which included heteroskedastic specifications, as dictated by the base model. The GLIMMIX procedure of SAS (version 9.4) was used to fit the base and QP models and the NLMIXED procedure was used to fit the BLL and BLQ models. We further illustrated the use of a grid search of initial parameter values to facilitate convergence and parameter estimation in nonlinear mixed models. Fit between competing dose-response models was compared using a maximum likelihood-based Bayesian information criterion (BIC). The QP, BLL, and BLQ models fitted on G:F of nursery pigs yielded BIC values of 353.7, 343.4, and 345.2, respectively, thus indicating a better fit of the BLL model. The BLL breakpoint estimate of the SID Trp:Lys ratio was 16.5% (95% confidence interval [16.1, 17.0]). Problems with
Sayar, Beyza S; Rüegg, Simon; Schmidt, Enno; Sibilia, Maria; Siffert, Myriam; Suter, Maja M; Galichet, Arnaud; Müller, Eliane J
2014-01-01
Novel insights into intra-cellular signalling involved in pemphigus vulgaris (PV), an autoimmune blistering disease of skin and mucous membranes, are now revealing new therapeutic approaches such as the chemical inhibition of PV-associated signals in conjunction with standard immunosuppressive therapy. However, extensive inhibition of signalling molecules that are required for normal tissue function and integrity may hamper this approach. Using a neonatal PV mouse model, we demonstrate that epidermal blistering can be prevented in a dose-dependent manner by clinically approved EGFR inhibitors erlotinib and lapatinib, but only up to approximately 50% of normal EGFR activity. At lower EGFR activity, blisters again aggravated and were highly exacerbated in mice with a conditional deletion of EGFR. Statistical analysis of the relation between EGFR activity and the extent of skin blistering revealed the best fit with a non-linear, V-shaped curve with a median break point at 52% EGFR activity (P = 0.0005). Moreover, lapatinib (a dual EGFR/ErbB2 inhibitor) but not erlotinib significantly reduced blistering in the oral cavity, suggesting that signalling mechanisms differ between PV predilection sites. Our results demonstrate that future clinical trials evaluating EGFR/ErbB2 inhibitors in PV patients must select treatment doses that retain a specific level of signal molecule activity. These findings may also be of relevance for cancer patients treated with EGFR inhibitors, for whom skin lesions due to extensive EGFR inhibition represent a major threat.
Lokstein, Heiko; Krikunova, Maria; Teuchner, Klaus; Voigt, Bernd
2011-08-15
Photosynthetically active pigments are usually organized into pigment-protein complexes. These include light-harvesting antenna complexes (LHCs) and reaction centers. Site energies of the bound pigments are determined by interactions with their environment, i.e., by pigment-protein as well as pigment-pigment interactions. Thus, resolution of spectral substructures of the pigment-protein complexes may provide valuable insight into structure-function relationships. By means of conventional (linear) and time-resolved spectroscopic techniques, however, it is often difficult to resolve the spectral substructures of complex pigment-protein assemblies. Nonlinear polarization spectroscopy in the frequency domain (NLPF) is shown to be a valuable technique in this regard. Based on initial experimental work with purple bacterial antenna complexes as well as model systems NLPF has been extended to analyse the substructure(s) of very complex spectra, including analyses of interactions between chlorophylls and "optically dark" states of carotenoids in LHCs. The paper reviews previous work and outlines perspectives regarding the application of NLPF spectroscopy to disentangle structure-function relationships in pigment-protein complexes.
Sharifzadeh, Yasamin; Kao, Ming-Chih; Sturgeon, John A; Rico, Thomas J; Mackey, Sean; Darnall, Beth D
2017-07-01
Pain catastrophizing is a maladaptive response to pain that amplifies chronic pain intensity and distress. Few studies have examined how pain catastrophizing relates to opioid prescription in outpatients with chronic pain. The authors conducted a retrospective observational study of the relationships between opioid prescription, pain intensity, and pain catastrophizing in 1,794 adults (1,129 women; 63%) presenting for new evaluation at a large tertiary care pain treatment center. Data were sourced primarily from an open-source, learning health system and pain registry and secondarily from manual review of electronic medical records. A binary opioid prescription variable (yes/no) constituted the dependent variable; independent variables were age, sex, pain intensity, pain catastrophizing, depression, and anxiety. Most patients were prescribed at least one opioid medication (57%; n = 1,020). A significant interaction and main effects of pain intensity and pain catastrophizing on opioid prescription were noted (P < 0.04). Additive modeling revealed sex differences in the relationship between pain catastrophizing, pain intensity, and opioid prescription, such that opioid prescription became more common at lower levels of pain catastrophizing for women than for men. Results supported the conclusion that pain catastrophizing and sex moderate the relationship between pain intensity and opioid prescription. Although men and women patients had similar Pain Catastrophizing Scale scores, historically "subthreshold" levels of pain catastrophizing were significantly associated with opioid prescription only for women patients. These findings suggest that pain intensity and catastrophizing contribute to different patterns of opioid prescription for men and women patients, highlighting a potential need for examination and intervention in future studies.
Frequency Response of Synthetic Vocal Fold Models with Linear and Nonlinear Material Properties
Shaw, Stephanie M.; Thomson, Scott L.; Dromey, Christopher; Smith, Simeon
2014-01-01
Purpose The purpose of this study was to create synthetic vocal fold models with nonlinear stress-strain properties and to investigate the effect of linear versus nonlinear material properties on fundamental frequency during anterior-posterior stretching. Method Three materially linear and three materially nonlinear models were created and stretched up to 10 mm in 1 mm increments. Phonation onset pressure (Pon) and fundamental frequency (F0) at Pon were recorded for each length. Measurements were repeated as the models were relaxed in 1 mm increments back to their resting lengths, and tensile tests were conducted to determine the stress-strain responses of linear versus nonlinear models. Results Nonlinear models demonstrated a more substantial frequency response than did linear models and a more predictable pattern of F0 increase with respect to increasing length (although range was inconsistent across models). Pon generally increased with increasing vocal fold length for nonlinear models, whereas for linear models, Pon decreased with increasing length. Conclusions Nonlinear synthetic models appear to more accurately represent the human vocal folds than linear models, especially with respect to F0 response. PMID:22271874
Energy Technology Data Exchange (ETDEWEB)
Hakan Ozaltun; Pavel Medvedev
2014-11-01
The effects of the foil flatness on stress-strain behavior of monolithic fuel mini-plates during fabrication and irradiation were studied. Monolithic plate-type fuels are a new fuel form being developed for research and test reactors to achieve higher uranium densities. This concept facilitates the use of low-enriched uranium fuel in the reactor. These fuel elements are comprised of a high density, low enrichment, U–Mo alloy based fuel foil encapsulated in a cladding material made of Aluminum. To evaluate the effects of the foil flatness on the stress-strain behavior of the plates during fabrication, irradiation and shutdown stages, a representative plate from RERTR-12 experiments (Plate L1P756) was considered. Both fabrication and irradiation processes of the plate were simulated by using actual irradiation parameters. The simulations were repeated for various foil curvatures to observe the effects of the foil flatness on the peak stress and strain magnitudes of the fuel elements. Results of fabrication simulations revealed that the flatness of the foil does not have a considerable impact on the post fabrication stress-strain fields. Furthermore, the irradiation simulations indicated that any post-fabrication stresses in the foil would be relieved relatively fast in the reactor. While, the perfectly flat foil provided the slightly better mechanical performance, overall difference between the flat-foil case and curved-foil case was not significant. Even though the peak stresses are less affected, the foil curvature has several implications on the strain magnitudes in the cladding. It was observed that with an increasing foil curvature, there is a slight increase in the cladding strains.
Guo, Xiaoya; Zhu, Jian; Maehara, Akiko; Monoly, David; Samady, Habib; Wang, Liang; Billiar, Kristen L; Zheng, Jie; Yang, Chun; Mintz, Gary S; Giddens, Don P; Tang, Dalin
2017-02-01
Computational models have been used to calculate plaque stress and strain for plaque progression and rupture investigations. An intravascular ultrasound (IVUS)-based modeling approach is proposed to quantify in vivo vessel material properties for more accurate stress/strain calculations. In vivo Cine IVUS and VH-IVUS coronary plaque data were acquired from one patient with informed consent obtained. Cine IVUS data and 3D thin-slice models with axial stretch were used to determine patient-specific vessel material properties. Twenty full 3D fluid-structure interaction models with ex vivo and in vivo material properties and various axial and circumferential shrink combinations were constructed to investigate the material stiffness impact on stress/strain calculations. The approximate circumferential Young's modulus over stretch ratio interval [1.0, 1.1] for an ex vivo human plaque sample and two slices (S6 and S18) from our IVUS data were 1631, 641, and 346 kPa, respectively. Average lumen stress/strain values from models using ex vivo, S6 and S18 materials with 5 % axial shrink and proper circumferential shrink were 72.76, 81.37, 101.84 kPa and 0.0668, 0.1046, and 0.1489, respectively. The average cap strain values from S18 material models were 150-180 % higher than those from the ex vivo material models. The corresponding percentages for the average cap stress values were 50-75 %. Dropping axial and circumferential shrink consideration led to stress and strain over-estimations. In vivo vessel material properties may be considerably softer than those from ex vivo data. Material stiffness variations may cause 50-75 % stress and 150-180 % strain variations.
Energy Technology Data Exchange (ETDEWEB)
Nijhuis, A; Ilyin, Y; Abbas, W [Faculty of Science and Technology, Low Temperature Division, University of Twente, PO Box 217, 7500 AE Enschede (Netherlands)], E-mail: a.nijhuis@tnw.utwente.nl
2008-06-15
We have measured the critical current (I{sub c}) of a high current density Nb{sub 3}Sn strand subjected to spatial periodic bending, periodic contact stress and uniaxial strain. The strand is destined for the cable-in-conduit conductors (CICC) of the European dipole (EDIPO) 12.5 T superconducting magnet test facility. The spatial periodic bending was applied on the strand, using the bending wavelengths from 5 to 10 mm with a peak bending strain of 1.5%, a periodic contact stress with a periodicity of 4.7 mm and a stress level exceeding 250 MPa. For the uniaxial strain characterization, the voltage-current characteristics were measured with an applied axial strain from -0.9% to +0.3%, with a magnetic field from 6 to 14 T, temperature from 4.2 to 10 K and currents up to almost 900 A. In addition the axial stiffness was determined by a tensile axial stress-strain test. The characterization of the strand is essential for understanding the behaviour of the strand under mainly axial thermal stress variation during cool down and transverse electromagnetic forces during charging, which is essential for the design of the CICC for the dipole magnet. The strand appears to be fully reversible in the compressive regime during the axial strain testing, while in the tensile regime, the behaviour is already irreversibly degraded when reaching the maximum in the critical current versus strain characteristic. The degradation is accentuated by an immediate decrease of the n value by a factor of 2. The parameters for the improved deviatoric strain description are derived from the I{sub c} data, giving the accuracy of the scaling with a standard deviation of 4 A, which is by far within the expected deviation for the large scale strand production of such a high J{sub c} strand. The I{sub c} versus the applied bending strain follows the low resistivity limit, indicative of full interfilament current transfer, while a strong decrease is observed at a peak bending strain of {approx}0
Energy Technology Data Exchange (ETDEWEB)
Byers, Loren W. [Los Alamos National Laboratory; Ten Cate, James A. [Los Alamos National Laboratory; Johnson, Paul A. [Los Alamos National Laboratory
2012-06-28
Nonlinear resonance ultrasound spectroscopy experiments conducted on concrete cores, one chemically and mechanically damaged by alkali-silica reactivity, and one undamaged, show that this material displays highly nonlinear wave behavior, similar to many other damaged materials. They find that the damaged sample responds more nonlinearly, manifested by a larger resonant peak and modulus shift as a function of strain amplitude. The nonlinear response indicates that there is a hysteretic influence in the stress-strain equation of state. Further, as in some other materials, slow dynamics are present. The nonlinear response they observe in concrete is an extremely sensitive indicator of damage. Ultimately, nonlinear wave methods applied to concrete may be used to guide mixing, curing, or other production techniques, in order to develop materials with particular desired qualities such as enhanced strength or chemical resistance, and to be used for damage inspection.
Energy Technology Data Exchange (ETDEWEB)
Doh, Jaeh Yeok; Lee, Jong Soo [Yonsei University, Seoul (Korea, Republic of); Lee, Seung Uk [Gyeongbuk Hybrid Technology Institute, Yeongcheon (Korea, Republic of)
2016-03-15
In this study, a Back-propagation neural network (BPN) is employed to conduct an approximation of a true stress-strain curve using the load-displacement experimental data of DP590, a high-strength material used in automobile bodies and chassis. The optimized interconnection weights are obtained with hidden layers and output layers of the BPN through intelligent learning and training of the experimental data; by using these weights, a mathematical model of the material's behavior is suggested through this feed-forward neural network. Generally, the material properties from the tensile test cannot be acquired until the fracture regions, since it is difficult to measure the cross-section area of a specimen after diffusion necking. For this reason, the plastic properties of the true stress-strain are extrapolated using the weighted-average method after diffusion necking. The accuracies of BPN-based meta-models for predicting material properties are validated in terms of the Root mean square error (RMSE). By applying the approximate material properties, the reliable finite element solution can be obtained to realize the different shapes of the finite element models. Furthermore, the sensitivity analysis of the approximate meta-model is performed using the first-order approximate derivatives of the BPN and is compared with the results of the finite difference method. In addition, we predict the tension velocity's effect on the material property through a first-order sensitivity analysis.
Institute of Scientific and Technical Information of China (English)
张丰发; 杜星文; 于增信
2003-01-01
Effects of transverse loads on longitudinal stress-strain behaviors and longitudinal constant tensile loads on transverse stress-strain behaviors of single ply of nylon cord-rubber composite are studied respectively under biaxial tensile condition with cruciform specimen. Effects of transverse constant tensile load on longitudinal tensile mechanical properties are indistinctive compared with corresponding uniaxial longitudinal tensile mechanical properties. It can be relative to larger difference between longitudinal and transverse mechanical properties. Its dominating failure mode is typical fiber-dominated mode; However, Experiment results indicate that transverse mechanical properties of nylon cord-rubber composite with longitudinal constant tensile loads are distinct from its uniaxial transverse tensile mechanical properties. It can be attribute to action of longitudinal tension that makes material rigidify in the direction perpendicular to fiber, Mode of failure is representative of matrix-dominated failure. For the measurement of large deformation up to 50 percent, a special CCD imaging method is employed in the experimental investigation that makes measurement of large deformations more precise.
Imaeva, L. P.; Imaev, V. S.; Mel'nikova, V. I.; Koz'min, B. M.
2016-11-01
A comprehensive investigation aimed at determining seismotectonic types of destruction and the stress-strain state of the Earth's crust in the main seismogenerating structures of the Arctic-Asian seismic belt is conducted for the territory of the northeastern sector of the Russian Arctic region. Based on the degree of activity of geodynamical processes, the regional principles for ranking neotectonic structures are elaborated, and neotectonic zoning is carried out based on the substantiated differentiation of the corresponding classes. Within the limits of the Laptev Sea, Kharaulakh, and Lena-Anabar segments, we analyzed I the structural-tectonic position of the most recent structures, II the deep structure parameters, III the parameters of the active fault system, and IV the parameters of the tectonic stress field, as revealed from tectonophysical analysis of Late Cenozoic fault and fold deformations. Based on the seismological data, the mean seismotectonic deformation tensors are calculated to determine, in combination with geological and geophysical data, the orientations of the principal stress axes and to reveal the structural-tectonic regularity for tectonic regimes of the stress-strain state of the Earth's crust in the Arctic sector of the boundary between the Eurasian and North American lithospheric plates.
Perrino, Alma P; Garcia, Ricardo
2016-04-28
Understanding the mechanical functionalities of complex biological systems requires the measurement of the mechanical compliance of their smallest components. Here, we develop a force microscopy method to quantify the softness of a single antibody pentamer by measuring the stress-strain curve with force and deformation resolutions, respectively, of 5 pN and 50 pm. The curve shows three distinctive regions. For ultrasmall compressive forces (5-75 pN), the protein's central region shows that the strain and stress are proportional (elastic regime). This region has an average Young's modulus of 2.5 MPa. For forces between 80 and 220 pN, the stress is roughly proportional to the strain with a Young's modulus of 9 MPa. Higher forces lead to irreversible deformations (plastic regime). Full elastic recovery could reach deformations amounting to 40% of the protein height. The existence of two different elastic regions is explained in terms of the structure of the antibody central region. The stress-strain curve explains the capability of the antibody to sustain multiple collisions without any loss of biological functionality.
Hamiltonian realizations of nonlinear adjoint operators
Fujimoto, Kenji; Scherpen, Jacquelien M.A.; Gray, W. Steven
2002-01-01
This paper addresses the issue of state-space realizations for nonlinear adjoint operators. In particular, the relationships between nonlinear Hilbert adjoint operators, Hamiltonian extensions and port-controlled Hamiltonian systems are established. Then, characterizations of the adjoints of control
Hamiltonian Realizations of Nonlinear Adjoint Operators
Fujimoto, Kenji; Scherpen, Jacquelien M.A.; Gray, W. Steven
2000-01-01
This paper addresses state-space realizations for nonlinear adjoint operators. In particular the relationship among nonlinear Hilbert adjoint operators, Hamiltonian extensions and port-controlled Hamiltonian systems are clarified. The characterization of controllability, observability and Hankel ope
Institute of Scientific and Technical Information of China (English)
Yu Wang; Daining Fang; Ai Kah Soh; Bin Liu
2007-01-01
In this paper, by capturing the atomic informa-tion and reflecting the behaviour governed by the nonlin-ear potential function, an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes (SWCNT's) is established to describe the nonlinear stress-strain curve of SWCNT's and to predict both the elastic properties and breaking strain of SWCNT's during tensile deformation. An analysis based on the virtual internal bond (VIB) model proposed by P. Zhang et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an acceptable analytical method for analyzing the mechanical behavior of SWCNT's.
On the nonlinear anelastic behaviour of AHSS
Torkabadi, A.; Meinders, V. T.; van den Boogaard, A. H.
2016-08-01
It has been widely observed that below the yield stress the loading/unloading stress-strain curves of plastically deformed metals are in fact not linear but slightly curved, showing a hysteresis behaviour during unloading/reloading cycles. In addition to the purely elastic strain, extra dislocation based micro-mechanisms are contributing to the reversible strain of the material which results in the nonlinear unloading/reloading behaviour. This extra reversible strain is the so called anelastic strain. As a result, the springback will be larger than that predicted by FEM considering only the recovery of the elastic strain. In this work the physics behind the anelastic behaviour is discussed and experimental results for a dual phase steel are demonstrated. Based on the physics of the phenomenon a model for anelastic behaviour is presented that can fit the experimental results with a good accuracy.
Bloembergen, Nicolaas
1996-01-01
Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe
Directory of Open Access Journals (Sweden)
Orekhov Vyacheslav Valentinovich
Full Text Available The interaction process of a power plant building with the soil base is studied basing on mathematical modeling of the construction process of Kambarata-2 HPP, taking into account the excavation of foundation pit, the concreting schedule of the building construction, the HPP units putting into operation and territory planning. Mathematical modeling of stress-strain state of the system “power plant - soil base” in the process of construction was performed by using the computer program “Zemlya” (the Earth, which implements the method of finite elements. Such a behavior of soil was described using elastoplastic soil model, the parameters of which were determined from the results of the triaxial tests. As shown by the results of the research, the continuous change of settlement, slope, deflection and torsion of the bottom plate and accordingly change of stressed-strained state of power plant are noted during the construction process. The installed HPP construction schedule, starting from the construction of the first block and the adjacent mounting platform, is leading to the formation of initial roll of bottom plate to the path of the mounting pad. In the process of further construction of powerhouse, up to the 29th phase of construction (out of 40, a steady increase in its subsidence (maximum values of about 4.5 cm is noted. Filling of foundation pit hollows and territorial planning of the construction area lead to drastic situation. In this case, as a territory planning points exceeded the relief, the plastic deformation in the soil evolves, resulting in significant subsidence of the bottom plate under the first block (up to 7.4 cm. As a result, the additional subsidence of the soil of bottom plate edges lead to the large vertical movement in relation to its central part and it is bent around the X axis, resulting in a large horizontal tensile stress values of Sz (up to 2.17 MPa in the constructive elements of the upper part of the
岩石剪切破坏全应力-应变性状%COMPLETE STRESS-STRAIN BEHAVIOR FOR SHEAR FAILURE OF ROCKS
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The investigation of complete stress-strain behavior andcompressive failure behavior of some Hong Kong rocks are carried out. A large number of tests have been conducted to study the deformation and failure features of rocks. Some interesting test results have been obtained. These results show that localized deformation and failure strongly affect the deformation and failure process of the specimens just prior to the peak stress and in the post-peak stage. The two types of failure modes, namely exfoliation and shear failure have been investigated in detail. For the exfoliation failure mode, an experiment method has been proposed to observe the exfoliating process. A proposed model has been used to explain the influence of exfoliation on the gross stress-strain curve. It is found that the exfoliation during loading may be one of the reasons that a granite specimen exhibits Class Ⅱ behavior. The influences of machine stiffness control modes, end constraints, loading rate and confining pressure on the test results have been discussed and investigated. A new classification method of rock failure has been proposed. Special attention has been devoted to the investigation of the localized deformation and failure process of intact rock in the shear failure mode. A test method is proposed to detect the process. It is found that the deformation of rock material may be divided into three stages: namely uniform stage, pre-peak bifurcation stage and post-peak bifurcation stage. This phenomenon has been explained by a proposed qualitative analysis. It is further found that this localized process will significantly influence the shape of stress-strain curves, that is, the localized deformation is one of reasons that rock displays the effect of length to diameter ratio. A constitutive model is proposed to simulate the localized deformation and failure process. It can simulate the strain softening, strain localization, effect of length to diameter(L/D) ratio， unloading
Energy Technology Data Exchange (ETDEWEB)
Geniet, F; Leon, J [Physique Mathematique et Theorique, CNRS-UMR 5825, 34095 Montpellier (France)
2003-05-07
A nonlinear system possessing a natural forbidden band gap can transmit energy of a signal with a frequency in the gap, as recently shown for a nonlinear chain of coupled pendulums (Geniet and Leon 2002 Phys. Rev. Lett. 89 134102). This process of nonlinear supratransmission, occurring at a threshold that is exactly predictable in many cases, is shown to have a simple experimental realization with a mechanical chain of pendulums coupled by a coil spring. It is then analysed in more detail. First we go to different (nonintegrable) systems which do sustain nonlinear supratransmission. Then a Josephson transmission line (a one-dimensional array of short Josephson junctions coupled through superconducting wires) is shown to also sustain nonlinear supratransmission, though being related to a different class of boundary conditions, and despite the presence of damping, finiteness, and discreteness. Finally, the mechanism at the origin of nonlinear supratransmission is found to be a nonlinear instability, and this is briefly discussed here.
Energy Technology Data Exchange (ETDEWEB)
Oudalova, Alla; Geras' kin, Stanislav; Dikarev, Vladimir; Dikareva, Nina; Chernonog, Elena [Russian Institute of Agricultural Radiology and Agroecology, RIARAE, 249032 Obninsk (Russian Federation); Copplestone, David [Environment Agency, Millbank Tower, 25th. Floor, 21/24 Millbank, London, SW1P 4XL (United Kingdom); Evseeva, Tatyana [Institute of Biology, Kommunisticheskaya st., 28 Syktyvkar 167610, Komi Republic (Russian Federation)
2006-07-01
Over several decades, modelling the effects of ionizing radiation on biological system has relied on the target principle [Timofeeff-Ressovsky et al., 1935], which assumes that cell damage or modification to genes appear as a direct consequence of the exposure of biological macromolecules to charged particles. Furthermore, it is assumed that there is no threshold for the induction of biological damage and that the effects observed are proportional to the energy absorbed. Following this principle, the average number of hits per target should increase linearly with dose, and the yield of mutations per unit of dose is assumed to be the same at both low and high doses (linearity of response). This principle has served as the scientific background for the linear no-threshold (LNT) concept that forms the basis for the radiological protection for the public and the environment [ICRP, 1990]. It follows from the LNT that there is an additional risk for human health from exposure to any radiation level, even below natural background. Since the mid 50's, however, the scientific basis for the LNT concept has been challenged as experimental data have shown that, at low doses, there was a non linear relationship in the dose response. Luchnik and Timofeeff-Ressovsky were the first who showed a non-linear response to a low dose exposure [Luchnik, 1957; Timofeeff-Ressovsky and Luchnik, 1960]. Since then, many data have been accumulated which contradict the LNT model at low doses and dose rates. However, the hit-effect paradigm has become such a strong and indissoluble fact that it has persisted even under the growing pressure of scientific evidence for phenomena at low dose exposure that can not be successfully accounted for by the LNT concept. In recent years, additional information on non-targeted effects of radiation has been accumulated following the first reports of an adaptive response in human lymphocytes [Olivieri et al., 1984] as well as bystander mutagenic effect of
Directory of Open Access Journals (Sweden)
Budiamin
2015-07-01
Full Text Available Buton granular asphalt (BGA is produced from natural rock asphalt. The employment of hotmix cold laid containing BGA with modifier oil base and modifier oil base can substitute hot rolled asphalt (HRA construction in the remote and distance areas. Natural rock asphalt that deposited in Buton Island, Southeast Sulawesi in Indonesia is crushed to produce Buton granular asphalt (BGA. BGA and cold modifier were utilized to produce hot mixture that can be laid at cold temperature of 50OC to 27OC.The present study provides the information concerning the stress-strain pattern and compressive strength of hotmix cold laid containing BGA and Modifier Oil Base and Modifier Water Base at the storing and compaction time of 4 hours, 3 days and 7 days.
Energy Technology Data Exchange (ETDEWEB)
Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik (Clay Technology AB, Lund (Sweden))
2010-12-15
This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed
Hong, S. D.; Fedors, R. F.; Schwarzl, F.; Moacanin, J.; Landel, R. F.
1981-01-01
A theoretical analysis of the tensile stress-strain relation of elastomers at constant strain rate is presented which shows that the time and the stress effect are separable if the experimental time scale coincides with a segment of the relaxation modulus that can be described by a single power law. It is also shown that time-strain separability is valid if the strain function is linearly proportional to the Cauchy strain, and that when time-strain separability holds, two strain-dependent quantities can be obtained experimentally. In the case where time and strain effect are not separable, superposition can be achieved only by using temperature and strain-dependent shift factors.
Energy Technology Data Exchange (ETDEWEB)
Funk, D.J.; Laabs, G.W.; Peterson, P.D.; Asay, B.W.
1995-09-01
We have measured the stress/strain behavior of PBX 9501, Mock 900-21 and two new mocks consisting of monoclinic granular sugar embedded in (1) a BDNPA-F/estane binder (a 9501 material mock; a hard organic crystal embedded in a plastic) and (2) neat estane (an LX-14 mock) at strain rates from 10{sup -3} to 10{sup -1}, at two L/D`s and at two temperatures (25 and 60 C). We find that the compressive strength falls with increasing temperature and rises with increasing strain rate. We also find that the new 9501 sugar mock most closely resembles the behavior of the 9501 explosive and differences may be attributable to the different ages of the estane binder used.
Energy Technology Data Exchange (ETDEWEB)
Dueck, Ann; Boergesson, Lennart; Johannesson, Lars-Erik (Clay Technology AB, Lund (Sweden))
2010-12-15
This report describes a laboratory study conducted to update the material model of the buffer material used in the analyses of the effect of a rock shear through a deposition hole. The study considers some new conditions and is especially focused on the reference case with MX-80Ca developed for SR-Site (MX-80 ion exchanged to Ca). The material model is based on relations between density, swelling pressure, shear strength and rate of strain. The reference model is described by Boergesson et al. (2010). The laboratory study is focused on undrained stress-strain-strength properties, which have been studied mainly by conducting triaxial tests and unconfined compression tests. The test results are compared to the earlier measurements and models which show that the new results fit very well into the general picture and models. For the new conditions suitable values of constants included in the model are proposed
Directory of Open Access Journals (Sweden)
Tran Ngoc Dang
2016-01-01
Full Text Available Background: The relationship between temperature and mortality has been found to be U-, V-, or J-shaped in developed temperate countries; however, in developing tropical/subtropical cities, it remains unclear. Objectives: Our goal was to investigate the relationship between temperature and mortality in Hue, a subtropical city in Viet Nam. Design: We collected daily mortality data from the Vietnamese A6 mortality reporting system for 6,214 deceased persons between 2009 and 2013. A distributed lag non-linear model was used to examine the temperature effects on all-cause and cause-specific mortality by assuming negative binomial distribution for count data. We developed an objective-oriented model selection with four steps following the Akaike information criterion (AIC rule (i.e. a smaller AIC value indicates a better model. Results: High temperature-related mortality was more strongly associated with short lags, whereas low temperature-related mortality was more strongly associated with long lags. The low temperatures increased risk in all-category mortality compared to high temperatures. We observed elevated temperature-mortality risk in vulnerable groups: elderly people (high temperature effect, relative risk [RR]=1.42, 95% confidence interval [CI]=1.11–1.83; low temperature effect, RR=2.0, 95% CI=1.13–3.52, females (low temperature effect, RR=2.19, 95% CI=1.14–4.21, people with respiratory disease (high temperature effect, RR=2.45, 95% CI=0.91–6.63, and those with cardiovascular disease (high temperature effect, RR=1.6, 95% CI=1.15–2.22; low temperature effect, RR=1.99, 95% CI=0.92–4.28. Conclusions: In Hue, the temperature significantly increased the risk of mortality, especially in vulnerable groups (i.e. elderly, female, people with respiratory and cardiovascular diseases. These findings may provide a foundation for developing adequate policies to address the effects of temperature on health in Hue City.
Directory of Open Access Journals (Sweden)
Danilov Aleksandr Ivanovich
2014-12-01
Full Text Available In the article, the co-authors analyze the findings of the experimental and theoretical studies into the real behaviour of a thin-walled cold-formed purlin as part of the roof structure made of sandwich panels. The roof structure fragment was tested; displacements and stresses, that the purlin was exposed to, were identified in respect of each loading increment. NASTRAN software was employed to perform the numerical analysis of the roof structure, pre-exposed to experimental tests, in the geometrically and physically non-linear setting. The finite element model, generated as a result (the numerical analysis pattern, is sufficiently well-set, given the proposed grid of elements, and it ensures reasonably trustworthy results. The diagrams describing the stress/displacement to the load ratio and obtained numerically are consistent with those generated experimentally. The gap between the critical loading values reaches 4%. Analytical and experimental findings demonstrate their close conformity, and this fact may justify the application of the numerical model, generated within the framework of this research project, in the course of any further research actions. The co-authors have identified that the exhaustion of the bearing capacity occurs due to the loss of the buckling resistance as a result of the lateral torsional buckling.
Directory of Open Access Journals (Sweden)
Paolo Vinciguerra
2014-01-01
Full Text Available Purpose. To compare biomechanical effect, riboflavin penetration and distribution in transepithelial corneal collagen cross-linking with iontophoresis (I-CXL, with standard cross linking (S-CXL and current transepithelial protocol (TE-CXL. Materials and Methods. The study was divided into two different sections, considering, respectively, rabbit and human cadaver corneas. In both sections corneas were divided according to imbibition protocols and irradiation power. Imaging mass spectrometry by matrix-assisted laser desorption/ionization (MALDI-IMS and stress-strain measurements were used. Forty-eight rabbit and twelve human cadaver corneas were evaluated. Results. MALDI-IMS showed a deep riboflavin penetration throughout the corneal layers with I-CXL, with a roughly lower concentration in the deepest layers when compared to S-CXL, whereas with TE-CXL penetration was considerably less. In rabbits, there was a significant increase (by 71.9% and P=0.05 in corneal rigidity after I-CXL, when compared to controls. In humans, corneal rigidity increase was not significantly different among the subgroups. Conclusions. In rabbits, I-CXL induced a significant increase in corneal stiffness as well as better riboflavin penetration when compared to controls and TE-CXL but not to S-CXL. Stress-strain in human corneas did not show significant differences among techniques, possibly because of the small sample size of groups. In conclusion, I-CXL could be a valid alternative to S-CXL for riboflavin delivery in CXL, preserving the epithelium.
2016-07-01
Advanced Research Projects Agency (DARPA) Dynamics-Enabled Frequency Sources (DEFYS) program is focused on the convergence of nonlinear dynamics and...Early work in this program has shown that nonlinear dynamics can provide performance advantages. However, the pathway from initial results to...dependent nonlinear stiffness observed in these devices. This work is ongoing, and will continue through the final period of this program . Reference 9
Nonlinear Interaction of Waves in Geomaterials
Ostrovsky, L. A.
2009-05-01
Progress of 1990s - 2000s in studying vibroacoustic nonlinearities in geomaterials is largely related to experiments in resonance samples of rock and soils. It is now a common knowledge that many such materials are very strongly nonlinear, and they are characterized by hysteresis in the dependence between the stress and strain tensors, as well as by nonlinear relaxation ("slow time"). Elastic wave propagation in such media has many peculiarities; for example, third harmonic amplitude is a quadratic (not cubic as in classical solids) function of the main harmonic amplitude, and average wave velocity is linearly (not quadratically as usual) dependent on amplitude. The mechanisms of these peculiarities are related to complex structure of a material typically consisting of two phases: a hard matrix and relatively soft inclusions such as microcracks and grain contacts. Although most informative experimental results have been obtained in rock in the form of resonant bars, few theoretical models are yet available to describe and calculate waves interacting in such samples. In this presentation, a brief overview of structural vibroacoustic nonlinearities in rock is given first. Then, a simple but rather general approach to the description of wave interaction in solid resonators is developed based on accounting for resonance nonlinear perturbations which are cumulating from period to period. In particular, the similarity and the differences between traveling waves and counter-propagating waves are analyzed for materials with different stress-strain dependences. These data can be used for solving an inverse problem, i.e. characterizing nonlinear properties of a geomaterial by its measured vibroacoustic parameters. References: 1. L. Ostrovsky and P. Johnson, Riv. Nuovo Chimento, v. 24, 1-46, 2007 (a review); 2. L. Ostrovsky, J. Acoust. Soc. Amer., v. 116, 3348-3353, 2004.
Nayfeh, Ali Hasan
1995-01-01
Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim
Yoshida, Zensho
2010-01-01
This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl
Nanda, Sudarsan
2013-01-01
"Nonlinear analysis" presents recent developments in calculus in Banach space, convex sets, convex functions, best approximation, fixed point theorems, nonlinear operators, variational inequality, complementary problem and semi-inner-product spaces. Nonlinear Analysis has become important and useful in the present days because many real world problems are nonlinear, nonconvex and nonsmooth in nature. Although basic concepts have been presented here but many results presented have not appeared in any book till now. The book could be used as a text for graduate students and also it will be useful for researchers working in this field.
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...
Krempl, Erhard; Hong, Bor Zen
1989-01-01
A macromechanics analysis is presented for the in-plane, anisotropic time-dependent behavior of metal matrix laminates. The small deformation, orthotropic viscoplasticity theory based on overstress represents lamina behavior in a modified simple laminate theory. Material functions and constants can be identified in principle from experiments with laminae. Orthotropic invariants can be repositories for tension-compression asymmetry and for linear elasticity in one direction while the other directions behave in a viscoplastic manner. Computer programs are generated and tested for either unidirectional or symmetric laminates under in-plane loading. Correlations with the experimental results on metal matrix composites are presented.
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...
Analysis of Tensile Stress-Strain and Work-Hardening Behavior in 9Cr-1Mo Ferritic Steel
Choudhary, B. K.; Palaparti, D. P. Rao; Samuel, E. Isaac
2013-01-01
Detailed analysis on tensile true stress ( σ)-true plastic strain ( ɛ) and work-hardening behavior of 9Cr-1Mo steel have been performed in the framework of the Voce relationship and Kocks-Mecking approach for wide range of temperatures, 300 K to 873 K (27 °C to 600 °C) and strain rates (6.33 × 10-5 to 6.33 × 10-3 s-1). At all test conditions, σ- ɛ data were adequately described by the Voce equation. 9Cr-1Mo steel exhibited two-stage work-hardening behavior characterized by a rapid decrease in instantaneous work-hardening rate ( θ = dσ/ dɛ) with stress at low stresses (transient stage) followed by a gradual decrease in θ at high stresses (stage III). The variations of work-hardening parameters and θ- σ as a function of temperature and strain rate exhibited three distinct temperature regimes. Both work-hardening parameters and θ- σ displayed signatures of dynamic strain aging at intermediate temperatures and dominance of dynamic recovery at high temperatures. Excellent correlations have been obtained between work-hardening parameters evaluated using the Voce relationship and the respective tensile properties. A comparison of work-hardening parameters obtained using the Voce equation and Kocks-Mecking approach suggested an analogy between the two for the steel.
Directory of Open Access Journals (Sweden)
Baño, V.
2012-06-01
Full Text Available The objective of this paper is to develop a twodimensional numerical model to simulate the response of Scots pine (Pinus sylvestris L. defect free timber members in order to predict the behaviour of these members when subjected to external forces. For this purpose, data of the mechanical properties of Scots pine were obtained by performing experimental tests on specimens. We determined the stresses and deformations of timber beams in the elastic-plastic and plastic phases. In addition, we developed a finite element software that considered the orthotropic nature of timber, the non-linearity of the compression-reduction branch and the differing moduli of elasticity in tension and compression for Scots pine beams free from defects. The software developed simulates an experimental four point bending test according to UNE-EN 408 Standard.
El objetivo de este trabajo es el desarrollo de un modelo numérico bidimensional de piezas de madera de Pinus sylvestris L. libre de defectos que prediga su comportamiento frente a solicitaciones externas. Para su desarrollo, fue necesario realizar ensayos experimentales sobre probetas de pequeño tamaño con el fin de obtener los datos de las propiedades mecánicas para el Pinus sylvestris L. de procedencia española. A partir de los datos experimentales obtenidos, se desarrolla un programa de elementos finitos que considera la ortotropía de la madera, la no linealidad de la rama compresión-acortamiento y los distintos módulos de elasticidad a tracción y a compresión para vigas libres de defectos. El programa simula el ensayo experimental de flexión en cuatro puntos según la Norma UNE-EN 408 y aborda la determinación de las tensiones y deformaciones de las vigas de madera en las tres fases de comportamiento: elástica, elastoplástica y plástica.
Nonlinear systems in medicine.
Higgins, John P
2002-01-01
Many achievements in medicine have come from applying linear theory to problems. Most current methods of data analysis use linear models, which are based on proportionality between two variables and/or relationships described by linear differential equations. However, nonlinear behavior commonly occurs within human systems due to their complex dynamic nature; this cannot be described adequately by linear models. Nonlinear thinking has grown among physiologists and physicians over the past century, and non-linear system theories are beginning to be applied to assist in interpreting, explaining, and predicting biological phenomena. Chaos theory describes elements manifesting behavior that is extremely sensitive to initial conditions, does not repeat itself and yet is deterministic. Complexity theory goes one step beyond chaos and is attempting to explain complex behavior that emerges within dynamic nonlinear systems. Nonlinear modeling still has not been able to explain all of the complexity present in human systems, and further models still need to be refined and developed. However, nonlinear modeling is helping to explain some system behaviors that linear systems cannot and thus will augment our understanding of the nature of complex dynamic systems within the human body in health and in disease states.
Nonlinearity and nonclassicality in a nanomechanical resonator
Energy Technology Data Exchange (ETDEWEB)
Teklu, Berihu [Clermont Universite, Blaise Pascal University, CNRS, PHOTON-N2, Institut Pascal, Aubiere Cedex (France); Universita degli Studi di Milano, Dipartimento di Fisica, Milano (Italy); Ferraro, Alessandro; Paternostro, Mauro [Queen' s University, Centre for Theoretical Atomic, Molecular, and Optical Physics, School of Mathematics and Physics, Belfast (United Kingdom); Paris, Matteo G.A. [Universita degli Studi di Milano, Dipartimento di Fisica, Milano (Italy)
2015-12-15
We address quantitatively the relationship between the nonlinearity of a mechanical resonator and the nonclassicality of its ground state. In particular, we analyze the nonclassical properties of the nonlinear Duffing oscillator (being driven or not) as a paradigmatic example of a nonlinear nanomechanical resonator. We first discuss how to quantify the nonlinearity of this system and then show that the nonclassicality of the ground state, as measured by the volume occupied by the negative part of the Wigner function, monotonically increases with the nonlinearity in all the working regimes addressed in our study. Our results show quantitatively that nonlinearity is a resource to create nonclassical states in mechanical systems. (orig.)
Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.
2012-01-01
Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.
Zhu, Hong-Ming; Pen, Ue-Li; Chen, Xuelei; Yu, Hao-Ran
2016-01-01
We present a direct approach to non-parametrically reconstruct the linear density field from an observed non-linear map. We solve for the unique displacement potential consistent with the non-linear density and positive definite coordinate transformation using a multigrid algorithm. We show that we recover the linear initial conditions up to $k\\sim 1\\ h/\\mathrm{Mpc}$ with minimal computational cost. This reconstruction approach generalizes the linear displacement theory to fully non-linear fields, potentially substantially expanding the BAO and RSD information content of dense large scale structure surveys, including for example SDSS main sample and 21cm intensity mapping.
Boyd, Robert W
2013-01-01
Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q
Ruszczynski, Andrzej
2011-01-01
Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates t
Institute of Scientific and Technical Information of China (English)
郑为为; 杨王玥; 孙祖庆
2002-01-01
B2-ordered Fe3Al single crystals with various orientations were deformed in tension at room temperature in vacuum. The shape of shear stress-strain curves and work hardening rates were found to be strongly dependent on the orientation. The formation of the five different work hardening stages were considered to be related to the number of operative slip systems, the effect of secondary slip systems and the dissociation of the twofold superdislocation. Stage I is an easy glide stage corresponding to single slip. Stage II, with high hardening rate, often corresponds to the existence of conjugate slip systems. Stage III, with relatively low hardening rate, corresponds to the weaker hardening of secondary slip systems. Stage IV, with the highest hardening rate, is not only related to multiple slip but also the dissociation of twofold superdislocations and the moving of superpartials with an antiphase boundary (APB) trap. Stages V, with a negative hardening rate, may be caused by the cross slip of single dissociated superdislocation. The number of stages and the work hardening rate of the same stage were also found to change significantly, when the tensile orientation lies in different orientation regions.
Directory of Open Access Journals (Sweden)
N. D. Chainov
2015-01-01
Full Text Available The paper considers a developed computational model to study a stress-strain state of the assembly unit components of a medium-speed diesel engine of new generation, type CH26.5/31, which comprises a cylinder head, a sleeve, a gasket, a block, two mounting studs and four power studs.The developed three-dimensional finite element model presented in this article allows us to take into consideration all the components that make up a gas joint, regardless of their geometric complexity. Its use enables us to estimate the cylinder head - gasket - sleeve tightness of sealing when applying the mounting, temperature, and gas loads, to define the stress and strain components of parts, as well as to study the gasket condition, including pressure distribution across its surface.Based on the results obtained in the study the finite element model of the cylinder head was modified considering a more detailed description of its geometry, thus reducing the principal tensile stresses.
Omori, Yasutomo; Barresi, Antonello; Kimura, Nozomi; Okamoto, Atsushi; Masuda, Toshiaki
2016-08-01
Our analyses of microboudinage structures of piemontite grains embedded within six samples of metachert, one collected from an ultrahigh-pressure (UHP) metamorphic unit at Lago di Cignana in Italy of the Western Alps, and the other five from surrounding high-pressure (HP) metamorphic units in Italy and France, have revealed that the structures are all symmetrical in type, and were presumably produced in coaxial strain fields. Stress-strain analyses of the microboudinaged grains revealed significant contrasts in the stress and strain histories of the UHP and HP metamorphic units, with the differential stress recorded by the UHP sample being unequivocally lower than that recorded by the five HP samples. In addition, our analyses showed that the UHP sample underwent stress-relaxation during microboudinage, whereas the five HP samples did not. On the basis of these observations and analyses we discuss the mechanical decoupling of the UHP and HP units that led to different histories in differential stress between the units during exhumation of the Western Alps.
Duc-Toan, Nguyen; Tien-Long, Banh; Dong-Won, Jung; Seung-Han, Yang; Young-Suk, Kim
2012-02-01
In order to predict correctly stress-strain curve for tensile tests at elevated and cooling temperatures, a modification of a Johnson-Cook (J-C) model and a new method to determine (J-C) material parameters are proposed. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick and Voce's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. An FEM tensile test simulation based on the isotropic hardening model for metal sheet at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code. The simulation results at elevated temperatures were firstly presented and then compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation. The modified (J-C) model showed the good comparability between the simulation results and the corresponding experiments.
Duc-Toan, Nguyen; Tien-Long, Banh; Young-Suk, Kim; Dong-Won, Jung
2011-08-01
In this study, a modified Johnson-Cook (J-C) model and an innovated method to determine (J-C) material parameters are proposed to predict more correctly stress-strain curve for tensile tests in elevated temperatures. A MATLAB tool is used to determine material parameters by fitting a curve to follow Ludwick's hardening law at various elevated temperatures. Those hardening law parameters are then utilized to determine modified (J-C) model material parameters. The modified (J-C) model shows the better prediction compared to the conventional one. As the first verification, an FEM tensile test simulation based on the isotropic hardening model for boron sheet steel at elevated temperatures was carried out via a user-material subroutine, using an explicit finite element code, and compared with the measurements. The temperature decrease of all elements due to the air cooling process was then calculated when considering the modified (J-C) model and coded to VUMAT subroutine for tensile test simulation of cooling process. The modified (J-C) model showed the good agreement between the simulation results and the corresponding experiments. The second investigation was applied for V-bending spring-back prediction of magnesium alloy sheets at elevated temperatures. Here, the combination of proposed J-C model with modified hardening law considering the unusual plastic behaviour for magnesium alloy sheet was adopted for FEM simulation of V-bending spring-back prediction and shown the good comparability with corresponding experiments.
Gou, Xiaofan; Schwartz, Justin
2013-10-01
Bi2Sr2CaCu2Ox/AgMg (Bi2212) multi filamentary superconducting round wires (RWs) can be only potential candidate for constructing the superconducting magnet with higher magnetic field (>25T). Very complicated microstructure of Bi2212 RWs has been found by recent SEM studies, and then the vital problems of Characterization of this unique microstructure and further exploration of the correlation of macro electromechanical properties with this microstructure arise. In this paper, it is firstly found that the rough surface of individual filaments can be well characterized by fractals. On the geometrical model with the fractal simulation of the rough surface, stress-strain relation of Bi2212 RWs has been investigated. The modelling result with considering the rough surface has a better agreement to the experimental data. At the request of the authors, and with the agreement of the Proceedings Editor, the above paper in AIP Proceedings has been retracted (as of 26 November 2013) due to a prior publication by the authors which reports similar data/results. That paper was first published in volume 26 (issue 5) of the journal Superconductor Science and Technology and was published on 4 April 2013: Fractal analysis of the role of the rough interface between Bi2Sr2CaCu2Ox filaments and the Ag matrix in the mechanical behavior of composite round wires The authors wish to apologize for any inconvenience caused by publication of their AIP Proceedings article.
Energy Technology Data Exchange (ETDEWEB)
Belattar, Adel, E-mail: adel.belattar@insa-rouen.fr [INSA Rouen/GPM, UMR CNRS 6634, BP 08, Avenue de l' Universite, 76800 St. Etienne du Rouvray (France); Taleb, Lakhdar; Hauet, Annie [INSA Rouen/GPM, UMR CNRS 6634, BP 08, Avenue de l' Universite, 76800 St. Etienne du Rouvray (France); Taheri, Said [LaMSID UMR EDF-CNRS 2832, Department AMA, 1 Avenue du General de Gaulle, 92141 Clamart Cedex (France)
2012-02-28
Highlights: Black-Right-Pointing-Pointer Contrary to low deformation, cyclic curve is not unique at high strain amplitude. Black-Right-Pointing-Pointer However, as the loading was continued cyclic hardening tends to stabilize. Black-Right-Pointing-Pointer Cyclic hardening is mainly kinematic type, isotropic component remains quasi-linear. Black-Right-Pointing-Pointer Increasing in pre-hardening strain amplitude has almost no effect on fatigue damage. Black-Right-Pointing-Pointer Fatigue life decreasing is associated with formation of walls, cells and defect bands. - Abstract: This study investigates the effects of loading history on the cyclic stress-strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension-compression tests were performed on the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results show that the cyclic curve is not unique, as it depends on the loading sequence. The same predeformed specimens were subjected to fatigue tests. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after preloading and their evolution during the fatigue cycles were characterized by transmission electron microscopy (TEM). The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction.
Directory of Open Access Journals (Sweden)
Boštjan Antoncic
2007-06-01
Full Text Available In this paper we propose one possible explanation of the interrelationships between education continuation or avoidance, satisfaction level, and experience (entrepreneurial maturity of potential and practicing entrepreneurs. By using the cusp catastrophe model we propose that relationship between education satisfaction and continuation tends to be linear for less experienced entrepreneurs (pre-entrepreneurs, whereas for more experienced entrepreneurs the relationship is proposed to be positive but non-linear (s-shaped. Data were collected with a structured questionnaire from 122 participants in management and entrepreneurship education and training programs. The proposed model was tested with linear and non-linear regression equations. The relationship between satisfaction and continuation (loyalty was found to be positive for all entrepreneurial and nonentrepreneurial groups. The appropriate functional form for the satisfaction-continuation relationship discovered for non-entrepreneurs and people that are only thinking about entrepreneurship (maybe-entrepreneurs is close to linear and less steep than for more entrepreneurial groups. By contrast, prospective entrepreneurs (people in the process of pre-start up and practicing entrepreneurs tend to be more sensitive to their education satisfaction in their future education continuation decisions. The appropriate functional form for these entrepreneurial groups tends to be cubical, which is close to the s-shaped function proposed in the cusp model. The study provided evidence that the relationships between entrepreneurial maturity, education satisfaction and education continuation may be modeled as a cusp catastrophe model. The proposed model can be helpful for education and for training providers (and marketers in explaining and predicting of education loyalty or the switching behavior of entrepreneurs.
In, Visarath; Longhini, Patrick; Kho, Andy; Neff, Joseph D.; Leung, Daniel; Liu, Norman; Meadows, Brian K.; Gordon, Frank; Bulsara, Adi R.; Palacios, Antonio
2012-12-01
The nonlinear channelizer is an integrated circuit made up of large parallel arrays of analog nonlinear oscillators, which, collectively, serve as a broad-spectrum analyzer with the ability to receive complex signals containing multiple frequencies and instantaneously lock-on or respond to a received signal in a few oscillation cycles. The concept is based on the generation of internal oscillations in coupled nonlinear systems that do not normally oscillate in the absence of coupling. In particular, the system consists of unidirectionally coupled bistable nonlinear elements, where the frequency and other dynamical characteristics of the emergent oscillations depend on the system's internal parameters and the received signal. These properties and characteristics are being employed to develop a system capable of locking onto any arbitrary input radio frequency signal. The system is efficient by eliminating the need for high-speed, high-accuracy analog-to-digital converters, and compact by making use of nonlinear coupled systems to act as a channelizer (frequency binning and channeling), a low noise amplifier, and a frequency down-converter in a single step which, in turn, will reduce the size, weight, power, and cost of the entire communication system. This paper covers the theory, numerical simulations, and some engineering details that validate the concept at the frequency band of 1-4 GHz.
Institute of Scientific and Technical Information of China (English)
魏岳嵩; 杜翠真
2014-01-01
确定变量间的因果关系是时间序列分析的重要内容。传统的图模型因果推断算法有着明显的局限性，要求模型是线性的且噪声项服从Gauss分布。本文利用图模型方法辨识非线性结构向量自回归模型变量间的因果关系，给出了一种基于互信息和条件互信息的非线性结构向量自回归因果图模型结构的非参数辨识方法。数值模拟结果验证了方法的有效性。%It is important to detect and clarify the cause-effect relationships among variables in time series analysis. Traditional graphical models causality inference methods have a salient limitation that the model must be linear and with Gaussian noise. In this paper, we apply the graphical models to infer the causal relationships a-mong variables of nonlinear structural vector autoregressive models. We propose a nonparametric method which employs both the mutual information and condi-tional mutual information to identify the causal structure of nonlinear structural vector autoregressive causal graph model. Numerical simulations demonstrate the effectiveness of the method.
Energy Technology Data Exchange (ETDEWEB)
Turchetti, G. (Bologna Univ. (Italy). Dipt. di Fisica)
1989-01-01
Research in nonlinear dynamics is rapidly expanding and its range of applications is extending beyond the traditional areas of science where it was first developed. Indeed while linear analysis and modelling, which has been very successful in mathematical physics and engineering, has become a mature science, many elementary phenomena of intrinsic nonlinear nature were recently experimentally detected and investigated, suggesting new theoretical work. Complex systems, as turbulent fluids, were known to be governed by intrinsically nonlinear laws since a long time ago, but received purely phenomenological descriptions. The pioneering works of Boltzmann and Poincare, probably because of their intrinsic difficulty, did not have a revolutionary impact at their time; it is only very recently that their message is reaching a significant number of mathematicians and physicists. Certainly the development of computers and computer graphics played an important role in developing geometric intuition of complex phenomena through simple numerical experiments, while a new mathematical framework to understand them was being developed.
Seider, Warren D.; Ungar, Lyle H.
1987-01-01
Describes a course in nonlinear mathematics courses offered at the University of Pennsylvania which provides an opportunity for students to examine the complex solution spaces that chemical engineers encounter. Topics include modeling many chemical processes, especially those involving reaction and diffusion, auto catalytic reactions, phase…
Directory of Open Access Journals (Sweden)
Timothy West
2016-10-01
Full Text Available In this paper we investigated the dopaminergic modulation of neuronal interactions occurring in the subthalamic nucleus (STN during Parkinson’s disease (PD. We utilized linear measures of local and long range synchrony such as power and coherence, as well as Detrended Fluctuation Analysis for Phase Synchrony (DFA-PS- a recently developed non-linear method that computes the extent of long tailed autocorrelations present in the phase interactions between two coupled signals. Through analysis of local field potentials (LFPs taken from the STN we seek to determine changes in the neurodynamics that may underpin the pathophysiology of PD in a group of 12 patients who had undergone surgery for deep brain stimulation. We demonstrate up modulation of alpha-theta (5-12 Hz band power in response to L-DOPA treatment, whilst low beta band power (15-20 Hz band-power is suppressed. We also find evidence for significant local connectivity within the region surrounding STN although there was no evidence for modulation via administration of L-DOPA. Further to this we present evidence for a positive correlation between the phase ordering of bilateral STN interactions and the severity of bradykinetic and rigidity symptoms in PD. Although the ability of non-linear measures to predict clinical state did not exceed standard measures such as beta power, these measures may help identify the connections which play a role in pathological dynamics.
Dodrill, Michael J.; Yackulic, Charles B.
2016-01-01
Drift-foraging models offer a mechanistic description of how fish feed in flowing water and the application of drift-foraging bioenergetics models to answer both applied and theoretical questions in aquatic ecology is growing. These models typically include nonlinear descriptions of ecological processes and as a result may be sensitive to how model inputs are summarized because of a mathematical property of nonlinear equations known as Jensen’s inequality. In particular, we show that the way in which continuous size distributions of invertebrate prey are represented within foraging models can lead to biases within the modeling process. We begin by illustrating how different equations common to drift-foraging models are sensitive to invertebrate inputs. We then use two case studies to show how different representations of invertebrate prey can influence predictions of energy intake and lifetime growth. Greater emphasis should be placed on accurate characterizations of invertebrate drift, acknowledging that inferences from drift-foraging models may be influenced by how invertebrate prey are represented.
Glower, D D; Spratt, J A; Snow, N D; Kabas, J S; Davis, J W; Olsen, C O; Tyson, G S; Sabiston, D C; Rankin, J S
1985-05-01
The Frank-Starling relationship generally has been examined with filling pressure as the index of preload, resulting in a curvilinear function that plateaus at higher filling pressures. To investigate this relationship further in the intact heart, 32 dogs were chronically instrumented with left ventricular and pleural micromanometers and with regional (10 dogs) or global (22 dogs) ultrasonic dimension transducers. Seven days after implantation, left ventricular pressure and regional or global dimensions were recorded in the conscious state. After autonomic blockade, preload was varied by vena caval occlusion. Myocardial function was assessed by calculating regional or global stroke work, and preload was measured as end-diastolic segment length or chamber volume. The relationship between stroke work and either end-diastolic segment length or chamber volume (termed the preload recruitable stroke work relationship) was highly linear in every study (mean r = .97) and could be quantified by a slope (MW) and x-intercept (LW). Previous nonlinear relationships between stroke work and filling pressure seemed to reflect the exponential diastolic pressure-volume curve. Over the physiologic range of systolic arterial pressures produced by infusion of nitroprusside or phenylephrine, no significant change was observed in MW or LW in the normal dog. Calcium infusion increased both regional and global MW by 71 +/- 19% and 65 +/- 9%, respectively (p less than .02), with no significant change in LW. To normalize for ventricular geometry and heart rate, stroke work was computed from circumferential stress-strain data and converted to myocardial power output, which was then plotted against end-diastolic circumferential strain. This relationship also was highly linear, and the slope, Mmp (mW/cm3 of myocardium), is proposed as a potential measure of intrinsic myocardial performance independent of loading, geometry, and heart rate.
Geometrical Nonlinearity Analysis of the Steel Network Arch Bridges
Directory of Open Access Journals (Sweden)
Sigutė Žilėnaitė
2016-12-01
Full Text Available Arch bridges are one of the popular, oldest and graceful bridges which are being built in zones of the city and out of the city. However arches becomes especially sensitive to their buckling response due to dominated compressive force in the arch. In order to ensure stability conditions of the individual arch and arch bridges, it is estimated not just geometrical factor of arch, residual stress, work conditions, geometric imperfections but geometrical nonlinearity too. Geometric nonlinearity especially dominates in many times static indeterminable systems such as network arch bridges. However there are a few represents of estimation of geometric nonlinearity of the new construction form of the arch bridges created in a middle of 20th century. This paper represents estimation of geometric nonlinearity with numerical method of the steel arch bridges with vertical hangers and network arch bridges. There are determined stress-strain law and principal behavior of the steel network arch bridges under symmetric and asymmetric pedestrian loadings.
Liu, Li; Wan, Jieqiu
2012-12-01
This paper explores the co-movement of Shanghai stock market and China Yuan (CNY) exchange rates. First, we find that stock price and exchange rate are significantly cross-correlated. Second, employing a cointegration test allowing for a structural break, we find that the Shanghai Composite Index (SCI) is not cointegrated with the exchange rate of CNY/USD. The so-called “cointegration” found in previous studies is just caused by the shock of the recent financial crisis. Third, using linear and nonlinear Granger causality tests, we find no causality between stock prices and exchange rates during the period before the recent financial crisis. After the financial crisis, a unidirectional causality behavior running from exchange rates to stock index is present.
2015-01-01
From the Back Cover: The emphasis throughout the present volume is on the practical application of theoretical mathematical models helping to unravel the underlying mechanisms involved in processes from mathematical physics and biosciences. It has been conceived as a unique collection of abstract methods dealing especially with nonlinear partial differential equations (either stationary or evolutionary) that are applied to understand concrete processes involving some important applications re...
Directory of Open Access Journals (Sweden)
Hendri Yanda
2010-11-01
Full Text Available Demand for higher productivity and good quality for machining parts has encourage many researchers to study the effects of machining parameters using FEM simulation using either two or three dimensions version. These are due to advantages such as software package and computational times are required. Experimental work is very costly, time consuming and labor intensive. The present work aims to simulate a three-dimensional orthogonal cutting operations using FEM software (Deform-3D to study the effects of rake angle on the cutting force, effective stress, strain and temperature on the edge of carbide cutting tool. There were seven runs of simulations. All simulations were performed for various rake angles of -15 deg, -10 deg, -5 deg, 0 deg, +5 deg, +10 deg, and +15 deg. The cutting speed, feed rate and depth of cut (DOC were kept constant at 100 m/min, 0.35 mm/rev and 0.3 mm respectively. The work piece used was ductile cast iron FCD500 grade and the cutting tool was DNMA432 series (tungsten, uncoated carbide tool, SCEA = 0; and radius angle 55 deg. The analysis of results show that, the increase in the rake angle from negative to positive angle, causing the decrease in cutting force, effective stress and total Von Misses strain. The minimum of the cutting force, effective stress and total Von Misses strain were obtained at rake angle of +15 deg. Increasing the rake caused higher temperature generated on the edge of carbide cutting tool and resulted in bigger contact area between the clearance face and the workpiece, consequently caused more friction and wear. The biggest deformation was occurred in the primary deformation zone, followed by the secondary deformation zone. The highest stress was also occurred in the primary deformation zone. But the highest temperature on the chip usually occurs in secondary deformation zone, especially in the sliding region, because the heat that was generated in the sticking region increased as the workpiece was
Neugebauer, Jennifer M; Hawkins, David A
2012-09-21
The purposes of this study were (1) determine if youth peak Achilles tendon (AT) strain, peak AT stress, and AT stiffness, measured during an isometric plantar flexion, differed after six months (mos) of growth, and (2) determine if sex, physical activity level (Physical Activity Questionnaire (PAQ-C)), and/or growth rate (GR) were related to these properties. AT stress, strain, and stiffness were quantified in 20 boys (13.47±0.81 years) and 22 girls (11.18±0.82 years) at 2 times (0 and 6 mos). GR (change in height in 6 mos) was not significantly different between boys and girls (3.5±1.4 and 3.4±1.1cm/6 mos respectively). Peak AT strain and stiffness (mean 3.8±0.4% and 128.9±153.6N/mm, respectively) did not differ between testing sessions or sex. Peak AT stress (22.1±2.4 and 24.0±2.1MPa at 0 and 6 mos, respectively) did not differ between sex and increased significantly at 6 mos due to a significant decrease in AT cross-sectional area (40.6±1.3 and 38.1±1.6mm(2) at 0 and 6 mos, respectively) with no significant difference in peak AT force (882.3±93.9 and 900.3± 65.5N at 0 and 6 mos, respectively). Peak AT stress was significantly greater in subjects with greater PAQ-C scores (9.1% increase with 1 unit increase in PAQ-C score) and smaller in subjects with faster GRs (13.8% decrease with 1cm/6 mos increase in GR). These results indicate that of the AT mechanical properties quantified, none differed between sex, and only peak AT stress significantly differed after 6 months and was related to GR and physical activity.
Directory of Open Access Journals (Sweden)
Michael Roerecke
2016-06-01
Conclusions: Alcohol consumption showed a complex association with hepatic steatosis with substantial differences by ethnicity and sex. Low alcohol consumption was beneficial in Japan with good epidemiological evidence, whereas there was no association in other countries. However, heterogeneity was large in countries other than Japan. More and higher quality research in diverse ethnic populations is needed to further clarify this relationship.
A simple approach to nonlinear oscillators
Ren, Zhong-Fu; He, Ji-Huan
2009-10-01
A very simple and effective approach to nonlinear oscillators is suggested. Anyone with basic knowledge of advanced calculus can apply the method to finding approximately the amplitude-frequency relationship of a nonlinear oscillator. Some examples are given to illustrate its extremely simple solution procedure and an acceptable accuracy of the obtained solutions.
Non-Linear Behaviour Of Gelatin Networks Reveals A Hierarchical Structure
Yang, Zhi
2015-12-14
We investigate the strain hardening behaviour of various gelatin networks - namely physically-crosslinked gelatin gel, chemically-crosslinked gelatin gels, and a hybrid gels made of a combination of the former two - under large shear deformations using the pre-stress, strain ramp, and large amplitude oscillation shear protocols. Further, the internal structures of physically-crosslinked gelatin gel and chemically-crosslinked gelatin gels were characterized by small angle neutron scattering (SANS) to enable their internal structures to be correlated with their nonlinear rheology. The Kratky plots of SANS data demonstrate the presence of small cross-linked aggregates within the chemically-crosslinked network, whereas in the physically-crosslinked gels a relatively homogeneous structure is observed. Through model fitting to the scattering data, we were able to obtain structural parameters, such as correlation length (ξ), cross-sectional polymer chain radius (Rc), and the fractal dimension (df) of the gel networks. The fractal dimension df obtained from the SANS data of the physically-crosslinked and chemically crosslinked gels is 1.31 and 1.53, respectively. These values are in excellent agreement with the ones obtained from a generalized non-linear elastic theory we used to fit our stress-strain curves. The chemical crosslinking that generates coils and aggregates hinders the free stretching of the triple helices bundles in the physically-crosslinked gels.
Lee, Cameron C.; Sheridan, Scott C.; Barnes, Brian B.; Hu, Chuanmin; Pirhalla, Douglas E.; Ransibrahmanakul, Varis; Shein, Karsten
2016-08-01
The coastal waters of the southeastern USA contain important protected habitats and natural resources that are vulnerable to climate variability and singular weather events. Water clarity, strongly affected by atmospheric events, is linked to substantial environmental impacts throughout the region. To assess this relationship over the long-term, this study uses an artificial neural network-based time series modeling technique known as non-linear autoregressive models with exogenous input (NARX models) to explore the relationship between climate and a water clarity index (KDI) in this area and to reconstruct this index over a 66-year period. Results show that synoptic-scale circulation patterns, weather types, and precipitation all play roles in impacting water clarity to varying degrees in each region of the larger domain. In particular, turbid water is associated with transitional weather and cyclonic circulation in much of the study region. Overall, NARX model performance also varies—regionally, seasonally and interannually—with wintertime estimates of KDI along the West Florida Shelf correlating to the actual KDI at r > 0.70. Periods of extreme (high) KDI in this area coincide with notable El Niño events. An upward trend in extreme KDI events from 1948 to 2013 is also present across much of the Florida Gulf coast.
Institute of Scientific and Technical Information of China (English)
邱宝象; 王效贵; 高增梁; Jiang Y
2011-01-01
提出预测缺口构件疲劳寿命的多轴局部应力应变法.采用Armstrong-Frederick (A-F)类循环塑性理论,描述具有非Masing特性的16MnR材料的循环塑性行为.结合A-F类循环塑性模型和增量式Neuber法,分析比例和非比例加载下缺口根部处的多轴应力应变状态.将局部应力应变应用于基于临界面的多轴疲劳损伤模型,对缺口构件进行疲劳损伤分析和疲劳寿命预测.分析结果表明,基于A-F类循环塑性理论的多轴局部应力应变法,能很好地描述缺口根部处的多轴应力应变状态,疲劳寿命的预测结果与试验数据基本吻合.%A multiaxial local stress-strain method was proposed to predict the fatigue life of notched components. The Armstrong-Frederick (A-F) type cyclic plasticity theory was adopted to describe the cyclic plasticity behavior. This newly developed cyclic plasticity theory is able to characterize the non-Masing behavior of 16MnR steel. The multiaxial stress-strain state at the notch root of notched components subjected to proportional and non-proportional loading was predicted by combining the A-F cyclic plasticity model and the incremental Neuber's rule. On the basis of the multiaxial local stress-strain state and a critical plane based multiaxial fatigue damage criterion, the fatigue damage of the notched components was analyzed and then the fatigue life was predicted. The numerical results show that the proposed multiaxial local stress-strain method can describe the multiaxial stress state at the notch root very well, and the predicted fatigue lives correlate well with the experimental data.
Unconstrained Finite Element for Geometrical Nonlinear Dynamics of Shells
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Humberto Breves Coda
2009-01-01
Full Text Available This paper presents a positional FEM formulation to deal with geometrical nonlinear dynamics of shells. The main objective is to develop a new FEM methodology based on the minimum potential energy theorem written regarding nodal positions and generalized unconstrained vectors not displacements and rotations. These characteristics are the novelty of the present work and avoid the use of large rotation approximations. A nondimensional auxiliary coordinate system is created, and the change of configuration function is written following two independent mappings from which the strain energy function is derived. This methodology is called positional and, as far as the authors' knowledge goes, is a new procedure to approximated geometrical nonlinear structures. In this paper a proof for the linear and angular momentum conservation property of the Newmark algorithm is provided for total Lagrangian description. The proposed shell element is locking free for elastic stress-strain relations due to the presence of linear strain variation along the shell thickness. The curved, high-order element together with an implicit procedure to solve nonlinear equations guarantees precision in calculations. The momentum conserving, the locking free behavior, and the frame invariance of the adopted mapping are numerically confirmed by examples.
Prieur, Fabrice; Vilenskiy, Gregory; Holm, Sverre
2012-10-01
A corrected derivation of nonlinear wave propagation equations with fractional loss operators is presented. The fundamental approach is based on fractional formulations of the stress-strain and heat flux definitions but uses the energy equation and thermodynamic identities to link density and pressure instead of an erroneous fractional form of the entropy equation as done in Prieur and Holm ["Nonlinear acoustic wave equations with fractional loss operators," J. Acoust. Soc. Am. 130(3), 1125-1132 (2011)]. The loss operator of the obtained nonlinear wave equations differs from the previous derivations as well as the dispersion equation, but when approximating for low frequencies the expressions for the frequency dependent attenuation and velocity dispersion remain unchanged.
A computer program for predicting nonlinear uniaxial material responses using viscoplastic models
Chang, T. Y.; Thompson, R. L.
1984-01-01
A computer program was developed for predicting nonlinear uniaxial material responses using viscoplastic constitutive models. Four specific models, i.e., those due to Miller, Walker, Krieg-Swearengen-Rhode, and Robinson, are included. Any other unified model is easily implemented into the program in the form of subroutines. Analysis features include stress-strain cycling, creep response, stress relaxation, thermomechanical fatigue loop, or any combination of these responses. An outline is given on the theoretical background of uniaxial constitutive models, analysis procedure, and numerical integration methods for solving the nonlinear constitutive equations. In addition, a discussion on the computer program implementation is also given. Finally, seven numerical examples are included to demonstrate the versatility of the computer program developed.
Three-dimensional Material and Geometrical Nonlinear Analysis of Adhesively Bonded Single Lap Joint
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S. Narasimhan
2003-04-01
Full Text Available The paper presents 3-D viscoplastic analysis of adhesively bonded single lap joint considering material and geometric nonlinearity. Total Lagrangian formulation is used to develop a 3-D finite element for geometric nonlinear analysis. The overall geometry of the single lap joint, the loading, and the boundary conditions has been considered, both according to the ASTM testing standards and from those adopted in earlier investigations. The constitutive relations for the adhesive are developed using a pressure-dependant (modified von Mises yield function and Ramberg-Osgood idealisation for the experimental stress-strain curve. The adherends and adhesive layers are both modelled using 20-noded solid elements. However, observations have been made, in particular, on peel and shear stresses in the adhesive layer, which provide useful insight into the 3-D nature of the problem.
A non-linear elastic constitutive framework for replicating plastic deformation in solids.
Energy Technology Data Exchange (ETDEWEB)
Roberts, Scott Alan; Schunk, Peter Randall
2014-02-01
Ductile metals and other materials typically deform plastically under large applied loads; a behavior most often modeled using plastic deformation constitutive models. However, it is possible to capture some of the key behaviors of plastic deformation using only the framework for nonlinear elastic mechanics. In this paper, we develop a phenomenological, hysteretic, nonlinear elastic constitutive model that captures many of the features expected of a plastic deformation model. This model is based on calculating a secant modulus directly from a materials stress-strain curve. Scalar stress and strain values are obtained in three dimensions by using the von Mises invariants. Hysteresis is incorporated by tracking an additional history variable and assuming an elastic unloading response. This model is demonstrated in both single- and multi-element simulations under varying strain conditions.
Longitudinal stress-strain relation of human peripheral vessels ex vivo%人体血管在离体情况下的纵向应力-应变规律
Institute of Scientific and Technical Information of China (English)
颉强; 杨柳; 赵黎; 黄耀添; 胡蕴玉; 李珏
2007-01-01
temperature was 20-25 ℃, and experiments were finished in 5 hours after sampling. The curve of stress-strain was fitted by the measured data.MAIN OUTCOME MEASURES: Longitudinal stretching ratio, residue strain and stress-strain relationship of normal limb arteries and veins.RESULTS: The longitudinal stretch ratio of each artery decreased along vascular branch from proximal heart part to distal heart part, and that of each vein was contrast; There were significant difference in the longitudinal stretch ratios of major artery compared with those of saphena megna vein and branchiocephalicae vein (P ＜ 0.001). The curve of artery shifting right showed the stiffness of vessels decreased along vascular branch from proximal heart part to distal heart part. That of vein shifting left showed the stiffness of vessels increased along vascular branch.CONCLUSION: With the major artery of human limbs from proximal end to distal end, both the longitudinal residue strain and the vascular stiffness gradually decreases, as for the vein, the condition is contrast. It suggests that the longitudinal biomechanical property should be involved into the consideration of repairing the artery and vein injuries of different sites.%背景:由于种属间的差异,只有人体血管的数据,才对医学临床实际有特殊而直接的意义.目的:从人体四肢动、静脉的纵向残余应变及应力-应变关系方面探讨四肢动、静脉的血管生物力学特性对损伤修复方法选择的影响.设计:观察性实验.单位:解放军第四军医大学西京医院骨科.材料:实验于2005-09/2006-09在解放军第四军医大学西京医院完成.标本取自13例男性急性严重头颅创伤死亡患者(已签署捐献同意书),年龄18～30岁.方法:①动、静脉血管标本的切取与保存:死亡后2 h内取材.用亚甲蓝在四肢主要动、静脉血管上做标记点,用游标卡尺测定各标记点间距,切取标记段血管并立即放入置于冰盒中的Kreb液中,
Rajasekar, Shanmuganathan
2016-01-01
This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...
Institute of Scientific and Technical Information of China (English)
1996-01-01
3.1 A Unified Nonlinear Feedback Functional Method for Study Both Control and Synchronization of Spatiotemporal Chaos Fang Jinqing Ali M. K. (Department of Physics, The University of Lethbridge,Lethbridge, Alberta T1K 3M4,Canada) Two fundamental questions dominate future chaos control theories.The first is the problem of controlling hyperchaos in higher dimensional systems.The second question has yet to be addressed:the problem of controlling spatiotemporal chaos in a spatiotemporal system.In recent years, control and synchronization of spatiotemporal chaos and hyperchaos have became a much more important and challenging subject. The reason for this is the control and synchronism of such behaviours have extensive and great potential of interdisciplinary applications, such as security communication, information processing, medicine and so on. However, this subject is not much known and remains an outstanding open.
Institute of Scientific and Technical Information of China (English)
李颗; 李向辉; 徐西林; 袁哲明
2014-01-01
[Aim] Repellent can protect the users by driving target pests away from them.It is important to establish a nonlinear quantitative structure-activity relationship (QSAR) model with high precision and strong interpretation for designing and synthesizing the new insect repellent with higher bioactivity.[Methods] Based on the repellent activities of 37 aromatic carboxylic acid derivatives against the housefly,Musca domestica,the initial descriptors were generated with stoichiometry software PCLIENT,and then the binary matrix shuffling filter (BMSF) and worst descriptor elimination multi-round method (WDEM) were successively used to conduct the nonlinear selection for initial descriptors.With the reserved descriptors,a support vector regression (SVR) model was established for the QSAR analysis of these 37 repellent derivatives.The influence of reserved descriptors on repellent activities was further analyzed with SVR interpretation system.[Results] The F-score of SVR model with original 1 542 descriptors was 1.2.However,it was 184.6 with the retained six descriptors after feature screening,indicating that feature screening has important effects on the precision of QSAR model.The importance of six molecular descriptors was as follows:p4BCD ＞ GATS7v ＞ T(O..O) ＞ JGI8 ＞ SssO ＞ nArCONR2.[Conclusion] The nonlinear relationship between reserved descriptors and the repellent activities of aromatic carboxylic acid derivatives against M.domestica was remarkable,and a high-performance SVR-QSAR model for repellent derivatives was constructed.%[目的]驱避剂可使害虫不敢接近受用者从而保护受用者免遭其害.建立高精度、可解释性强的非线性定量构效关系(quantitative structure-activity relationship,QSAR)模型对设计合成新的高效昆虫驱避剂有重要意义.[方法]基于37个芳香羧酸类化合物对家蝇Musca domestica的驱避活性,以量子化学计算软件PCLIENT获取每一化合物初始描述符,以二元矩阵重
The Nonlinearity of Sum and Product for Boolean Functions
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Huang Jinglian
2016-01-01
Full Text Available In this paper, we study the relationship between the nonlinearity of Boolean function and the nonlinearity of the sum and product of Boolean function, while derivative and e-derivative are used to study the problem further. We obtain that the sum of two functions’ nonlinearity is not less than the nonlinearity of the sum of two functions. The relationship between the nonlinearity of function and the nonlinearity of the sum and product of two functions are also obtained. Furthermore, we also get the relationship between the nonlinearity of the product of functions, and the derivative and e-derivative of function. Moreover, we also deduced some important applications on the basis of the above work.
Nonlinear Materials Characterization Facility
Federal Laboratory Consortium — The Nonlinear Materials Characterization Facility conducts photophysical research and development of nonlinear materials operating in the visible spectrum to protect...
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
Institute of Scientific and Technical Information of China (English)
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.
Nonlinear singular vectors and nonlinear singular values
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A novel concept of nonlinear singular vector and nonlinear singular value is introduced, which is a natural generalization of the classical linear singular vector and linear singular value to the nonlinear category. The optimization problem related to the determination of nonlinear singular vectors and singular values is formulated. The general idea of this approach is demonstrated by a simple two-dimensional quasigeostrophic model in the atmospheric and oceanic sciences. The advantage and its applications of the new method to the predictability, ensemble forecast and finite-time nonlinear instability are discussed. This paper makes a necessary preparation for further theoretical and numerical investigations.
Institute of Scientific and Technical Information of China (English)
张珊珊; 周明洁; 陈爽; 张建新
2012-01-01
Chinese personality traits have unique differences from other cultures due to China's special geography and collectivist cultural background. Therefore, the philosophy of localization was accepted and advocated by more and more Chinese psychologists. Meanwhile, the nonlinear relationships between personality traits and job performance have been found in some studies. These results transformed the traditional top - down strategy into double strategies for the applications of personality tests in the psychology of personnel management. However, there was no research to combine the linear and nonlinear models to examine the relationships between indigenous personality traits and job performance in the Chinese work setting. In the current study, we explored the linear and/or nonlinear reationships between indigenous personality traits and job performance. The participants were 182 service employees from several service industries in Beijing, and the immediate supervisors of the respondents provided ratings of their job performance and returned independently to the interviewers. The ratings of job performance were self - compiled based on job analysis and in - depth interview. Confirmatory factor analysis found that the one - factor performance model had a better fit (χ2 = 27.79, df = 8, CFI = . 95, NF1 = . 93, RMSEA = . 07), and the coefficient alpha was . 85. Meanwhile, the nine subscales from CPAI -2 were selected to assess the indigenous personality traits: face (FAC), family orientation (FAM), defensiveness (DEF), graciousness vs. meanness (G_M), veraciousness vs. slickness (V_S), traditionalism vs. modernity (T_M), renqing (REN), harmony (HAR) and thrift vs. extravagance (T_E). The mean Cronbach's coefficient for the entire set of personality scales was . 70 in the representative normal sample in Chinese mainland and Hong Kong. The data were analyzed with SPSS 15.0, and the main statistical methods were correlation analysis and hierarchical polynomial regression
Arnold, S. M.; Saleeb, A. F.; Castelli, M. G.
1995-01-01
Specific forms for both the Gibb's and complementary dissipation potentials are chosen such that a complete (i.e., fully associative) potential base multiaxial, nonisothermal unified viscoplastic model is obtained. This model possesses one tensorial internal state variable (that is, associated with dislocation substructure) and an evolutionary law that has nonlinear kinematic hardening and both thermal and strain induced recovery mechanisms. A unique aspect of the present model is the inclusion of nonlinear hardening through the use of a compliance operator, derived from the Gibb's potential, in the evolution law for the back stress. This nonlinear tensorial operator is significant in that it allows both the flow and evolutionary laws to be fully associative (and therefore easily integrated), greatly influences the multiaxial response under non-proportional loading paths, and in the case of nonisothermal histories, introduces an instantaneous thermal softening mechanism proportional to the rate of change in temperature. In addition to this nonlinear compliance operator, a new consistent, potential preserving, internal strain unloading criterion has been introduced to prevent abnormalities in the predicted stress-strain curves, which are present with nonlinear hardening formulations, during unloading and reversed loading of the external variables. The specific model proposed is characterized for a representative titanium alloy commonly used as the matrix material in SiC fiber reinforced composites, i.e., TIMETAL 21S. Verification of the proposed model is shown using 'specialized' non-standard isothermal and thermomechanical deformation tests.
Directory of Open Access Journals (Sweden)
K. R. McCall
1996-01-01
Full Text Available The velocity of sound in rock is a strong function of pressure, indicating that wave propagation in rocks is very nonlinear. The quasistatic elastic properties of rocks axe hysteretic, possessing discrete memory. In this paper a new theory is developed, placing all of these properties (nonlinearity, hysteresis, and memory on equal footing. The starting point of the new theory is closer to a microscopic description of a rock than the starting point of the traditional five-constant theory of nonlinear elasticity. However, this starting point (the number density Ï? of generic mechanical elements in an abstract space is deliberately independent of a specific microscopic model. No prejudice is imposed as to the mechanism causing nonlinear response in the microscopic mechanical elements. The new theory (1 relates suitable stress-strain measurements to the number density Ï? and (2 uses the number density Ï? to find the behaviour of nonlinear elastic waves. Thus the new theory provides for the synthesis of the full spectrum of elastic behaviours of a rock. Early development of the new theory is sketched in this contribution.
Scalerandi, Marco; Agostini, Valentina; Delsanto, Pier Paolo; Van Den Abeele, Koen; Johnson, Paul A
2003-06-01
Recent studies show that a broad category of materials share "nonclassical" nonlinear elastic behavior much different from "classical" (Landau-type) nonlinearity. Manifestations of "nonclassical" nonlinearity include stress-strain hysteresis and discrete memory in quasistatic experiments, and specific dependencies of the harmonic amplitudes with respect to the drive amplitude in dynamic wave experiments, which are remarkably different from those predicted by the classical theory. These materials have in common soft "bond" elements, where the elastic nonlinearity originates, contained in hard matter (e.g., a rock sample). The bond system normally comprises a small fraction of the total material volume, and can be localized (e.g., a crack in a solid) or distributed, as in a rock. In this paper a model is presented in which the soft elements are treated as hysteretic or reversible elastic units connected in a one-dimensional lattice to elastic elements (grains), which make up the hard matrix. Calculations are performed in the framework of the local interaction simulation approach (LISA). Experimental observations are well predicted by the model, which is now ready both for basic investigations about the physical origins of nonlinear elasticity and for applications to material damage diagnostics.
A Fully Associative, Non-Linear Kinematic, Unified Viscoplastic Model for Titanium Based Matrices
Arnold, S. M.; Saleeb, A. F.; Castelli, M. G.
1994-01-01
Specific forms for both the Gibb's and complementary dissipation potentials are chosen such that a complete (i.e., fully associative) potential based multiaxial unified viscoplastic model is obtained. This model possesses one tensorial internal state variable that is associated with dislocation substructure, with an evolutionary law that has nonlinear kinematic hardening and both thermal and strain induced recovery mechanisms. A unique aspect of the present model is the inclusion of non-linear hardening through the use of a compliance operator, derived from the Gibb's potential, in the evolution law for the back stress. This non-linear tensorial operator is significant in that it allows both the flow and evolutionary laws to be fully associative (and therefore easily integrated) and greatly influences the multiaxial response under non-proportional loading paths. In addition to this nonlinear compliance operator, a new consistent, potential preserving, internal strain unloading criterion has been introduced to prevent abnormalities in the predicted stress-strain curves, which are present with nonlinear hardening formulations, during unloading and reversed loading of the external variables. Specification of an experimental program for the complete determination of the material functions and parameters for characterizing a metallic matrix, e.g., TIMETAL 21S, is given. The experiments utilized are tensile, creep, and step creep tests. Finally, a comparison of this model and a commonly used Bodner-Partom model is made on the basis of predictive accuracy and numerical efficiency.
Institute of Scientific and Technical Information of China (English)
陈爽; 周明洁; 张冠男; 王可欣; 李保滨; 张建新
2015-01-01
Objective To investigate the relationships between time spent on different types of Internet services and mental health,including linear and nonlinear relationship. Methods In December 2013,a five -item version of the mental health inventory(MHI-5)and a self-made questionnaire about time spent on different types of Internet services(including six types of Internet services:social network sites,instant messaging tools,online videos,online games,online shopping,other webpages)were administrated on 152 students. Pearson correlation analysis and hierarchical polynomial regression analysis were conducted to investigate the relationships between time spent on different types of Internet services and mental health. Results There were 139 valid responses(valid return rate was 91. 5%). There was no significant linear relationship between time spent on six types of Internet services and mental health(r= -0. 14~0. 03,P﹥0. 05). The square of time spent on social network sites(SNS)showed statistic significance in its regression coefficient to mental health(β= -0. 25,P﹤0. 05). Besides,time spent on SNS and mental health had a reversed-U curve relationship. Conclusion Time spent on SNS and mental health have a reversed-U curve relationship,which means moderate SNS users have better mental health compared to non SNS users and excessive SNS users.%目的：考察不同类型网络应用使用时间与心理健康的关系，包括线性与非线性关系。方法2013年12月，采用自编网络应用使用时间问卷（包括社交网站、聊天工具、网络视频、网络游戏、购物网站、其他网页6种类型的网络应用）与心理健康问卷（ five-item version of the mental health inventory，MHI-5）对北京某大学的学生152例进行问卷调查。二者关系研究采用皮尔逊相关分析以及分层多项式回归分析。结果回收有效问卷139份，有效率为91.5%。学生心理健康得分为（4.46±0.74）分，所有类型的网
Predicting nonlinear properties of metamaterials from the linear response.
O'Brien, Kevin; Suchowski, Haim; Rho, Junsuk; Salandrino, Alessandro; Kante, Boubacar; Yin, Xiaobo; Zhang, Xiang
2015-04-01
The discovery of optical second harmonic generation in 1961 started modern nonlinear optics. Soon after, R. C. Miller found empirically that the nonlinear susceptibility could be predicted from the linear susceptibilities. This important relation, known as Miller's Rule, allows a rapid determination of nonlinear susceptibilities from linear properties. In recent years, metamaterials, artificial materials that exhibit intriguing linear optical properties not found in natural materials, have shown novel nonlinear properties such as phase-mismatch-free nonlinear generation, new quasi-phase matching capabilities and large nonlinear susceptibilities. However, the understanding of nonlinear metamaterials is still in its infancy, with no general conclusion on the relationship between linear and nonlinear properties. The key question is then whether one can determine the nonlinear behaviour of these artificial materials from their exotic linear behaviour. Here, we show that the nonlinear oscillator model does not apply in general to nonlinear metamaterials. We show, instead, that it is possible to predict the relative nonlinear susceptibility of large classes of metamaterials using a more comprehensive nonlinear scattering theory, which allows efficient design of metamaterials with strong nonlinearity for important applications such as coherent Raman sensing, entangled photon generation and frequency conversion.
Directory of Open Access Journals (Sweden)
I. K. Badalakha
2009-12-01
Full Text Available The article presents the results of solving several problems of a flat deformation of elastic infinitely long massifs of different width and limited thickness. Various cases of conditions at the massif/base contact. The relationships between stressed and strained states previously suggested by the author, which differ from the generalized Hooke’s law, are used in the solutions.
NONLINEAR EXPECTATIONS AND NONLINEAR MARKOV CHAINS
Institute of Scientific and Technical Information of China (English)
PENG SHIGE
2005-01-01
This paper deals with nonlinear expectations. The author obtains a nonlinear generalization of the well-known Kolmogorov's consistent theorem and then use it to construct filtration-consistent nonlinear expectations via nonlinear Markov chains. Compared to the author's previous results, i.e., the theory of g-expectations introduced via BSDE on a probability space, the present framework is not based on a given probability measure. Many fully nonlinear and singular situations are covered. The induced topology is a natural generalization of Lp-norms and L∞-norm in linear situations.The author also obtains the existence and uniqueness result of BSDE under this new framework and develops a nonlinear type of von Neumann-Morgenstern representation theorem to utilities and present dynamic risk measures.
Rayleigh reflections and nonlinear acoustics of solids
Breazeale, M. A.
1980-10-01
Schlierken studies of ultrasonic waves, and nonlinear acoustics of solids are addressed. A goniometer for use in a Schlieren system for visualization of ultrasonic waves in liquids is described. The goniometer is used to obtain Schlieren photographs of leaky Rayleigh waves excited on an Al2O3 layer on a stainless steel reflector immersed in water, showing that the Rayleigh wave velocity in this case is less than that of either a water Al203 layer or a water stainless steel layer. Also investigated are: (1) nonlinearity parameters and third order elastic constants of copper between 300 and 3 K; (2) measurement of nonlinearity parameters in small solid samples by the harmonic generation technique; (3) relationship between solid nonlinearity parameters and thermodynamic Gruneisen parameters; and (4) quantum mechanical theory of nonlinear interaction of ultrasonic waves.
Energy Technology Data Exchange (ETDEWEB)
Barus, R. P. P., E-mail: rismawan.ppb@gmail.com [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung and Centre for Material and Technical Product, Jalan Sangkuriang No. 14 Bandung (Indonesia); Tjokronegoro, H. A.; Leksono, E. [Engineering Physics, Faculty of Industrial Technology, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia); Ismunandar [Chemistry Study, Faculty of Mathematics and Science, Institut Teknologi Bandung, Jalan Ganesa 10 Bandung (Indonesia)
2014-09-25
Fuel cells are promising new energy conversion devices that are friendly to the environment. A set of control systems are required in order to operate a fuel cell based power plant system optimally. For the purpose of control system design, an accurate fuel cell stack model in describing the dynamics of the real system is needed. Currently, linear model are widely used for fuel cell stack control purposes, but it has limitations in narrow operation range. While nonlinear models lead to nonlinear control implemnetation whos more complex and hard computing. In this research, nonlinear cancellation technique will be used to transform a nonlinear model into a linear form while maintaining the nonlinear characteristics. The transformation is done by replacing the input of the original model by a certain virtual input that has nonlinear relationship with the original input. Then the equality of the two models is tested by running a series of simulation. Input variation of H2, O2 and H2O as well as disturbance input I (current load) are studied by simulation. The error of comparison between the proposed model and the original nonlinear model are less than 1 %. Thus we can conclude that nonlinear cancellation technique can be used to represent fuel cell nonlinear model in a simple linear form while maintaining the nonlinear characteristics and therefore retain the wide operation range.
Nonlinear modeling of an aerospace object dynamics
Davydov, I. E.; Davydov, E. I.
2017-01-01
Here are presented the scientific results, obtained by motion modeling of complicated technical systems of aerospace equipment with consideration of nonlinearities. Computerized panel that allows to measure mutual influence of the system's motion and stabilization device with consideration of its real characteristics has been developed. Analysis of motion stability of a system in general has been carried out and time relationships of the system's motion taking in account nonlinearities are presented.
Energy Technology Data Exchange (ETDEWEB)
Munoz, V.; Rohr, G. A.; Tomba Martinez, A. G.; Cavalieri, A. L.
2011-07-01
A methodology for the mechanical evaluation of refractory materials at high temperatures and controlled atmosphere, designed and implemented in the Structural Materials Laboratory of Ceramics Division of INTEMA, is described. The methodology includes the measurement of the specimen deformation by contact extensometry in compression tests to obtain stress-strain curves and the use of a gaseous flow as a system to control atmosphere. The determination of stress-strain curves of Al{sub 2}O{sub 3}-MgO-C commercial refractories used in steelmaking ladles at room temperature and 1260 degree centigrade in different atmospheres is presented as an example of application of this methodology. (Author) 34 refs.
Nonlinear predictive control in the LHC accelerator
Blanco, E; Cristea, S; Casas, J
2009-01-01
This paper describes the application of a nonlinear model-based control strategy in a real challenging process. A predictive controller based on a nonlinear model derived from physical relationships, mainly heat and mass balances, has been developed and commissioned in the inner triplet heat exchanger unit (IT-HXTU) of the large hadron collider (LHC) particle accelerator at European Center for Nuclear Research (CERN). The advanced regulation\\ maintains the magnets temperature at about 1.9 K. The development includes a constrained nonlinear state estimator with a receding horizon estimation procedure to improve the regulator predictions.
Institute of Scientific and Technical Information of China (English)
郑瑞兰; 王旭升; 胡晓农
2016-01-01
位于内蒙古阿拉善盟的巴丹吉林沙漠是中国第二大沙漠,以其存在世界上最高的沙山以及约100个湖泊而著称.现今湖面海拔一般为1150~1200 m,前人研究认为在过去3万年以来的某些时期存在更高的湖面.假设沙丘洼地的形态基本保持不变,可以根据现今湖泊洼地的三维形态来模拟高湖面时期的湖泊群分布特征和总面积.以90 m分辨率的DEM数据为基础,对若干典型洼地等高面面积随高程的变化进行了分析,发现可以用幂函数和多项式2种非线性方程模拟.多数情况下需要多项式,但一般只要达到3阶就可以精确拟合.对于湖泊洼地,由于很少有湖水最大深度的数据,湖底最低高程往往是未知的.利用湖面以上的等高面数据建立拟合程度最佳的非线性函数可以反推最低高程,但仍然存在不确定性.这一点对恢复历史上的高湖面形态并没有影响.%Badain Jaran Desert located on the Alxa Plateau in Inner Mongolia is the second largest desert in China.It is renowned for its tallest sand hills in the world as well as for about 100 lakes.The water level in the lakes ranges from 1150 m and 1200m above the sea level.Previous studies have suggested higher water levels in the past 30 ka.Assuming that shapes of sand dunes and inter-dune depressions do not change,distribution of lakes and total lake area during those high-lake-level periods could be modeled from three-dimensional shape of the landscape.The 90 m-resolution DEM data are used to analyze relationship between area of the plan with an equal height and elevation of the plan in several typical depressions.Relationship is found to be approximated with two kinds of nonlinear equations:power or polynomial functions.In most cases third-order polynomial equation is available.The bottom elevation of a lake basin is usually unknown due to the lack of lake depth data.It can be estimated by nonlinear equations with optimized parameters
Energy Technology Data Exchange (ETDEWEB)
Bemer, E.; Bouteca, M.; Vincke, O. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France); Hoteit, N.; Ozanam, O. [Agence Nationale pour la Gestion des Dechets Radioactifs ANDRA, 92 - Chatenay Malabry (France)
2001-07-01
Due to the impact on productivity and oil an place estimates, reliable modeling of rock behavior is essential in reservoir engineering. This paper examines several aspects of rock poro-elastic behavior within the framework of Biot's mechanics of fluid saturated porous solids. Constitutive laws of linear and nonlinear poro-elasticity are first determined from a fundamental stress decomposition, which allows to clearly connect linear and nonlinear models. Concept of effective stress and rock compressibility are considered. Linear incremental stress-strain relations are derived from the proposed nonlinear constitutive law by defining tangent elastic properties. These characteristics are naturally functions of strains and pore pressure, but explicit expressions as functions of stresses and pore pressure are established herein. Experiments performed on a reservoir sandstone illustrate these points. A constitutive law of poro-visco-elasticity is finally presented and applied to experimental data obtained on clay. (authors)
Chen, Xianfeng; Zeng, Heping; Guo, Qi; She, Weilong
2015-01-01
This book presents an overview of the state of the art of nonlinear optics from weak light nonlinear optics, ultrafast nonlinear optics to electro-optical theory and applications. Topics range from the fundamental studies of the interaction between matter and radiation to the development of devices, components, and systems of tremendous commercial interest for widespread applications in optical telecommunications, medicine, and biotechnology.
Distributed nonlinear optical response
DEFF Research Database (Denmark)
Nikolov, Nikola Ivanov
2005-01-01
The purpose of the research presented here is to investigate basic physical properties in nonlinear optical materials with delayed or nonlocal nonlinearity. Soliton propagation, spectral broadening and the influence of the nonlocality or delay of the nonlinearity are the main focusses in the work...
Noncommutative Nonlinear Supersymmetry
Nishino, H; Nishino, Hitoshi; Rajpoot, Subhash
2002-01-01
We present noncommutative nonlinear supersymmetric theories. The first example is a non-polynomial Akulov-Volkov-type lagrangian with noncommutative nonlinear global supersymmetry in arbitrary space-time dimensions. The second example is the generalization of this lagrangian to Dirac-Born-Infeld lagrangian with nonlinear supersymmetry realized in dimensions D=2,3,4 and 6 (mod 8).
Fiber Nonlinearities: A Tutorial
Institute of Scientific and Technical Information of China (English)
Govind P. Agrawal
2003-01-01
Fiber nonlinearities have long been regarded as being mostly harmful for fiber-optic communication systems. Over the last few years, however, the nonlinear effects are increasingly being used for practical telecommunications applications,the Raman amplification being only one of the recent examples. In this tutorial I review the vario us nonlinear effects occurring in optical fibers from both standpoints..
Fiber Nonlinearities: A Tutorial
Institute of Scientific and Technical Information of China (English)
Govind; P.; Agrawal
2003-01-01
Fiber nonlinearities have long been regarded as being mostly harmful for fiber-optic communication systems. Over the last few years, however, the nonlinear effects are increasingly being used for practical telecommunications applications, the Raman amplification being only one of the recent examples. In this tutorial I review the various nonlinear effects occurring in optical fibers from both standpoints..
Recent advance in nonlinear aeroelastic analysis and control of the aircraft
Xiang Jinwu; Yan Yongju; Li Daochun
2014-01-01
A review on the recent advance in nonlinear aeroelasticity of the aircraft is presented in this paper. The nonlinear aeroelastic problems are divided into three types based on different research objects, namely the two dimensional airfoil, the wing, and the full aircraft. Different nonlinearities encountered in aeroelastic systems are discussed firstly, where the emphases is placed on new nonlinear model to describe tested nonlinear relationship. Research techniques, especially new theoretica...
Nonlinear and Stochastic Morphological Segregation
Blanton, M R
1999-01-01
I perform a joint counts-in-cells analysis of galaxies of different spectral types using the Las Campanas Redshift Survey (LCRS). Using a maximum-likelihood technique to fit for the relationship between the density fields of early- and late-type galaxies, I find a relative linear bias of $b=0.76\\pm 0.02$. This technique can probe the nonlinearity and stochasticity of the relationship as well. However, the degree to which nonlinear and stochastic fits improve upon the linear fit turns out to depend on the redshift range in question. In particular, there seems to be a systematic difference between the high- and low-redshift halves of the data (respectively, further than and closer than $cz\\approx 36,000$ km/s); all of the signal of stochasticity and nonlinearity comes from the low-redshift portion. Analysis of mock catalogs shows that the peculiar geometry and variable flux limits of the LCRS do not cause this effect. I speculate that the central surface brightness selection criteria of the LCRS may be responsi...
PBH tests for nonlinear systems
Kawano, Yu; Ohtsuka, Toshiyuki
2017-01-01
Recently, concepts of nonlinear eigenvalues and eigenvectors are introduced. In this paper, we establish connections between the nonlinear eigenvalues and nonlinear accessibility/observability. In particular, we provide a generalization of Popov- Belevitch-Hautus (PBH) test to nonlinear accessibilit
Tetrick, L E; Slack, K J; Da Silva, N; Sinclair, R R
2000-10-01
One hundred sixty licensed morticians were surveyed to examine differences among business owners, managers, and employees on the relations proposed by G. F. Koeske and R. D. Koeske's (1993) stressor-strain-outcome model. Forty-eight percent of the morticians were owners, 16% were managers, and 36% were employees. Owners had less social support from work-related sources and perceived lower levels of role ambiguity and role conflict, less emotional exhaustion, and higher levels of job satisfaction and professional satisfaction than did nonowners. Social support from work-related sources and ownership each moderated the relationship between emotional exhaustion and job satisfaction but not between emotional exhaustion and professional satisfaction. Emotional exhaustion partially mediated the effect of stressors on job satisfaction and professional satisfaction.
Energy Technology Data Exchange (ETDEWEB)
Tan, Z.; Khoo, H. [Carleton Univ., Ottawa, ON (Canada). Dept. of Civil and Environmental Engineering
2009-07-01
Failures in steel pipelines are typically preceded by inelastic local buckling which depends on the shape of the material stress-strain curve. Non-dimensional equations can be used to quantify and predict the buckling limits for a range of stress-strain curves found in pipes through parametric finite element analyses. This paper evaluated the feasibility and ease of using an equation to generate the stress-strain curve for a pipe buckling parametric study. A power-law based equation for generating the true stress-true plastic strain curve was adopted. The equation made it possible to quantify the local buckling response to various material stress-strain curves using only a few parameters, such as ultimate to yield strength (proportional limit) ratio, and strain at ultimate stress measured from the end of yield plateau. The same parameters can therefore be used for different material yield strength and length of yield plateau, and enable the development of a more compact material property dependent non-dimensional buckling limit equation. 6 refs., 6 tabs., 3 figs.
Directory of Open Access Journals (Sweden)
Vabishchevych М.О.
2015-12-01
Full Text Available The paper considers the investigation of the features of stress-strain state of the structure with heterogeneous physical and mechanical properties on the example of the finite element calculation model of soil arch, which is reinforced by composite reinforcing cage.
Nonlinear dynamics and complexity
Luo, Albert; Fu, Xilin
2014-01-01
This important collection presents recent advances in nonlinear dynamics including analytical solutions, chaos in Hamiltonian systems, time-delay, uncertainty, and bio-network dynamics. Nonlinear Dynamics and Complexity equips readers to appreciate this increasingly main-stream approach to understanding complex phenomena in nonlinear systems as they are examined in a broad array of disciplines. The book facilitates a better understanding of the mechanisms and phenomena in nonlinear dynamics and develops the corresponding mathematical theory to apply nonlinear design to practical engineering.
Comparing coefficients of nested nonlinear probability models
DEFF Research Database (Denmark)
Kohler, Ulrich; Karlson, Kristian Bernt; Holm, Anders
2011-01-01
In a series of recent articles, Karlson, Holm and Breen have developed a method for comparing the estimated coeffcients of two nested nonlinear probability models. This article describes this method and the user-written program khb that implements the method. The KHB-method is a general decomposi......In a series of recent articles, Karlson, Holm and Breen have developed a method for comparing the estimated coeffcients of two nested nonlinear probability models. This article describes this method and the user-written program khb that implements the method. The KHB-method is a general...... decomposition method that is unaffected by the rescaling or attenuation bias that arise in cross-model comparisons in nonlinear models. It recovers the degree to which a control variable, Z, mediates or explains the relationship between X and a latent outcome variable, Y*, underlying the nonlinear probability...
Effective ac response in weakly nonlinear composites
Energy Technology Data Exchange (ETDEWEB)
Wei Enbo [Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 (China); Yang Zidong [College of Power Engineering, University of Shanghai Science and Technology, Shanghai 200093 (China); Gu Guoqing [Information College of Science and Technology, East China Normal University, Shanghai 200062 (China)
2004-01-07
The perturbation method is developed to deal with the problem of determining the effective nonlinear conductivity of Kerr-like nonlinear media under an external ac electric field. As an example, we have considered the cylindrical inclusion embedded in a host under the sinusoidal external field E{sub 1} sin (<{omega}t) + E{sub 3} sin (3<{omega}t) with frequencies{omega} and 3{omega}. The potentials of composites at higher harmonics are derived in both local inclusion particle and host regions. The effective responses of bulk nonlinear composites at basic frequency and harmonics are given for cylindrical composites in the dilute limit. Moreover, the relationships between the nonlinear effective responses at the basic frequency and the third harmonics are derived.
Nonlinear Elliptic Differential Equations with Multivalued Nonlinearities
Indian Academy of Sciences (India)
Antonella Fiacca; Nikolaos Matzakos; Nikolaos S Papageorgiou; Raffaella Servadei
2001-11-01
In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is defined on all $\\mathbb{R}$. Assuming the existence of an upper and of a lower solution, we prove the existence of a solution between them. Also for a special version of the problem, we prove the existence of extremal solutions in the order interval formed by the upper and lower solutions. Then we drop the requirement that the monotone nonlinearity is defined on all of $\\mathbb{R}$. This case is important because it covers variational inequalities. Using the theory of operators of monotone type we show that the problem has a solution. Finally in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity. Using the critical point theory for nonsmooth locally Lipschitz functionals we prove the existence of at least two nontrivial solutions (multiplicity theorem).
Nonlinear I-V characteristics of nanoparticle compacts and nanocomposites
Energy Technology Data Exchange (ETDEWEB)
Herth, Simone [Rensselaer Polytechnic Institute, Troy, NY (United States); Bielefeld University, Bielefeld (Germany); Wang, Xiaoping; Hugener, Teresa; Schadler, Linda; Siegel, Richard [Rensselaer Polytechnic Institute, Troy, NY (United States); Hillborg, Henrik; Auletta, Tommaso [ABB AB, Corporate Research, Schweden (Sweden)
2007-07-01
Materials with nonlinear I-V characteristics are commonly used as field grading materials. In many cases, the non-linearity is achieved through the addition of equiaxed fillers to a polymer matrix. These composite field grading materials are optimized in terms of nonlinearity, conductivity, and breakdown strength. One limitation in designing new field grading materials is a robust understanding of the relationship between powder morphology, composition and electrical characteristics of the powder, as well as a robust understanding of the relationship between powder conductivity and non-linearity and composite non-linearity. In this work, treatment of ZnO powder with a SnF{sub 2} solution resulted in a powder that yielded highly non-linear behavior. The highest non-linearity was achieved for powders with at least two different phases and a rough surface, as indicated by transmission electron micrographs. In contrast, the non-linearity of the nanocomposite conductivity is mainly determined by the conductivity of the nanofiller. The electrical behavior of the non-linear powder can be understood by a polarization of the nanoparticles at the interfaces, whereas the nonlinearity of the nanocomposites can be explained by a tunnelling mechanism between two particles.
Caporali, Alessandro; Braitenberg, Carla; Burrato, Pierfrancesco; Carafa, Michele; Di Giovambattista, Rita; Gentili, Stefania; Mariucci, Maria Teresa; Montone, Paola; Morsut, Federico; Nicolini, Luca; Pivetta, Tommaso; Roselli, Pamela; Rossi, Giuliana; Valensise, Gian Luca; Vigano, Alfio
2016-04-01
may be seen as an indicator of the rate at which the regional stress is transferred to each fault; as its sign can be positive or negative, the Coulomb Failure Function rate should ultimately indicate the rate at which every fault for which sufficient geodetic data are available is loading or unloading elastic energy. A better understanding of the relationships among geodetically-documented strains, present-day stress, active faulting and seismicity for the entire country should enable us to outline regions where the current strains explain well the known seismicity and to single out areas where stress is consistently building up but are historically quiescent. In such areas the lack of seismicity may result from a limited earthquake coupling - i.e. current strains are consumed aseismically - or from the incompleteness of the earthquake record. Our results may ultimately contribute to the assessment of time-dependent seismic hazard in Italy, thus complementing the time-independent approach used for conventional seismic hazard maps.
Directory of Open Access Journals (Sweden)
Wei Khim Ng
2009-02-01
Full Text Available We construct nonlinear extensions of Dirac's relativistic electron equation that preserve its other desirable properties such as locality, separability, conservation of probability and Poincaré invariance. We determine the constraints that the nonlinear term must obey and classify the resultant non-polynomial nonlinearities in a double expansion in the degree of nonlinearity and number of derivatives. We give explicit examples of such nonlinear equations, studying their discrete symmetries and other properties. Motivated by some previously suggested applications we then consider nonlinear terms that simultaneously violate Lorentz covariance and again study various explicit examples. We contrast our equations and construction procedure with others in the literature and also show that our equations are not gauge equivalent to the linear Dirac equation. Finally we outline various physical applications for these equations.
Institute of Scientific and Technical Information of China (English)
李立新; 胡盛德; 叶奔
2012-01-01
To determine the twinning kinetics and the influence of twins on dislocation density and flow stress of 304 stainless steel, a constitutive relation model including the twinning kinetics was established by using dislocation theory and the stress-strain curve measured. The undetermined coefficients in this model were optimized by the tensile test data. Therefore, the model of twinning kinetics was obtained. Results for the model show that the dislocation density and flow stress increase rapidly with the increase of deformation when twins exist.%为确定304不锈钢的孪生动力学模型及孪生对位错密度和变形抗力的影响规律,利用位错理论建立了含材料孪生动力学关系的本构关系模型,实测了材料的应力应变曲线,运用实测结果优化确定了本构关系模型中的待定常数,进而建立了材料的孪生动力学关系模型,本构关系模型还表明,在孪生条件下,材料的位错密度及变形抗力随变形程度增加而快速增大.
Ionescu, Tudor C.; Scherpen, Jacquelien M. A.
We study the notion of cross Gramians for nonlinear gradient systems, using the characterization in terms of prolongation and gradient extension associated to the system. The cross Gramian is given for the variational system associated to the original nonlinear gradient system. We obtain linearization results that correspond to the notion of a cross Gramian for symmetric linear systems. Furthermore, first steps towards relations with the singular value functions of the nonlinear Hankel operator are studied and yield promising results.
Directory of Open Access Journals (Sweden)
W. L. Fouché
1983-03-01
Full Text Available In this article we discuss some aspects of nonlinear functional analysis. It included reviews of Banach’s contraction theorem, Schauder’s fixed point theorem, globalising techniques and applications of homotopy theory to nonlinear functional analysis. The author emphasises that fundamentally new ideas are required in order to achieve a better understanding of phenomena which contain both nonlinear and definite infinite dimensional features.
Nonlinear Electrodynamics and QED
2003-01-01
The limits of linear electrodynamics are reviewed, and possible directions of nonlinear extension are explored. The central theme is that the qualitative character of the empirical successes of quantum electrodynamics must be used as a guide for understanding the nature of the nonlinearity of electrodynamics at the subatomic level. Some established theories of nonlinear electrodynamics, namely, those of Mie, Born, and Infeld are presented in the language of the modern geometrical and topologi...
Non-linear Constitutive Model for the Oligocarbonate Polyurethane Material
Institute of Scientific and Technical Information of China (English)
Marek Pawlikowski
2014-01-01
The polyurethane,which was the subject of the constitutive research presented in the paper,was based on oligocarbonate diols Desmophen C2100 produced by Bayer@.The constitutive modelling was performed with a view to applying the material as the inlay of intervertebral disc prostheses.The polyurethane was assumed to be non-linearly viscohyperelastic,isotropic and incompressible.The constitutive equation was derived from the postulated strain energy function.The elastic and rheological constants were identified on the basis of experimental tests,i.e.relaxation tests and monotonic uniaxial tests at two different strain rates,i.e.λ =0.1 min-1 and λ =1.0 min-1.The stiffness tensor was derived and introduced to Abaqus@finite element (FE) software in order to numerically validate the constitutive model.The results of the constants identification and numerical implementation show that the derived constitutive equation is fully adequate to model stress-strain behavior of the polyurethane material.
Kono, Mitsuo
2010-01-01
A nonlinearity is one of the most important notions in modern physics. A plasma is rich in nonlinearities and provides a variety of behaviors inherent to instabilities, coherent wave structures and turbulence. The book covers the basic concepts and mathematical methods, necessary to comprehend nonlinear problems widely encountered in contemporary plasmas, but also in other fields of physics and current research on self-organized structures and magnetized plasma turbulence. The analyses make use of strongly nonlinear models solved by analytical techniques backed by extensive simulations and available experiments. The text is written for senior undergraduates, graduate students, lecturers and researchers in laboratory, space and fusion plasmas.
Nonlinear magnetic metamaterials.
Shadrivov, Ilya V; Kozyrev, Alexander B; van der Weide, Daniel W; Kivshar, Yuri S
2008-12-08
We study experimentally nonlinear tunable magnetic metamaterials operating at microwave frequencies. We fabricate the nonlinear metamaterial composed of double split-ring resonators where a varactor diode is introduced into each resonator so that the magnetic resonance can be tuned dynamically by varying the input power. We demonstrate that at higher powers the transmission of the metamaterial becomes power-dependent and, as a result, such metamaterial can demonstrate various nonlinear properties. In particular, we study experimentally the power-dependent shift of the transmission band and demonstrate nonlinearity-induced enhancement (or suppression) of wave transmission. (c) 2008 Optical Society of America
Organic nonlinear optical materials
Umegaki, S.
1987-01-01
Recently, it became clear that organic compounds with delocalized pi electrons show a great nonlinear optical response. Especially, secondary nonlinear optical constants of more than 2 digits were often seen in the molecular level compared to the existing inorganic crystals such as LiNbO3. The crystallization was continuously tried. Organic nonlinear optical crystals have a new future as materials for use in the applied physics such as photomodulation, optical frequency transformation, opto-bistabilization, and phase conjugation optics. Organic nonlinear optical materials, e.g., urea, O2NC6H4NH2, I, II, are reviewed with 50 references.
Nonlinearity-reduced interferometer
Wu, Chien-ming
2007-12-01
Periodic nonlinearity is a systematic error limiting the accuracy of displacement measurements at the nanometer level. It results from many causes such as the frequency mixing, polarization mixing, polarization-frequency mixing, and the ghost reflections. An interferometer having accuracy in displacement measurement of less than one-nanometer is necessary in nanometrology. To meet the requirement, the periodic nonlinearity should be less than deep sub-nanometer. In this paper, a nonlinearity-reduced interferometry has been proposed. Both the linear- and straightness-interferometer were tested. The developed interferometer demonstrated of a residual nonlinearity less than 25 pm.
Lasers for nonlinear microscopy.
Wise, Frank
2013-03-01
Various versions of nonlinear microscopy are revolutionizing the life sciences, almost all of which are made possible because of the development of ultrafast lasers. In this article, the main properties and technical features of short-pulse lasers used in nonlinear microscopy are summarized. Recent research results on fiber lasers that will impact future instruments are also discussed.
Eaton, D F
1991-07-19
The current state of materials development in nonlinear optics is summarized, and the promise of these materials is critically evaluated. Properties and important materials constants of current commercial materials and of new, promising, inorganic and organic molecular and polymeric materials with potential in second- and third-order nonlinear optical applications are presented.
Billings, S. A.
1988-03-01
Time and frequency domain identification methods for nonlinear systems are reviewed. Parametric methods, prediction error methods, structure detection, model validation, and experiment design are discussed. Identification of a liquid level system, a heat exchanger, and a turbocharge automotive diesel engine are illustrated. Rational models are introduced. Spectral analysis for nonlinear systems is treated. Recursive estimation is mentioned.
Ionescu, T. C.; Scherpen, J. M. A.; Korytowski, A; Malanowski, K; Mitkowski, W; Szymkat, M
2009-01-01
We study the notion of cross Gramians for nonlinear gradient systems, using the characterization in terms of prolongation and gradient extension associated to the system. The cross Gramian is given for the variational system associated to the original nonlinear gradient system. We obtain
DEFF Research Database (Denmark)
Clausen, Carl A. Balslev; Christiansen, Peter Leth; Torner, L.
1999-01-01
We show that with the quasi-phase-matching technique it is possible to fabricate stripes of nonlinearity that trap and guide light like waveguides. We investigate an array of such stripes and find that when the stripes are sufficiently narrow, the beam dynamics is governed by a quadratic nonlinear...
Controllability in nonlinear systems
Hirschorn, R. M.
1975-01-01
An explicit expression for the reachable set is obtained for a class of nonlinear systems. This class is described by a chain condition on the Lie algebra of vector fields associated with each nonlinear system. These ideas are used to obtain a generalization of a controllability result for linear systems in the case where multiplicative controls are present.
Menon, P. K. A.; Badgett, M. E.; Walker, R. A.
1992-01-01
Trajectory-control laws based on singular-perturbation theory and nonlinear dynamical modeling. Nonlinear maneuver autopilot commands flight-test trajectories of F-15 airplane. Underlying theory of controller enables separation of variables processed in fast and slow control loops, reducing amount of computation required.
State-variable analysis of non-linear circuits with a desk computer
Cohen, E.
1981-01-01
State variable analysis was used to analyze the transient performance of non-linear circuits on a desk top computer. The non-linearities considered were not restricted to any circuit element. All that is required for analysis is the relationship defining each non-linearity be known in terms of points on a curve.
Nonlinear optics and photonics
He, Guang S
2015-01-01
This book provides a comprehensive presentation on most of the major topics in nonlinear optics and photonics, with equal emphasis on principles, experiments, techniques, and applications. It covers many major new topics including optical solitons, multi-photon effects, nonlinear photoelectric effects, fast and slow light , and Terahertz photonics. Chapters 1-10 present the fundamentals of modern nonlinear optics, and could be used as a textbook with problems provided at the end of each chapter. Chapters 11-17 cover the more advanced topics of techniques and applications of nonlinear optics and photonics, serving as a highly informative reference for researchers and experts working in related areas. There are also 16 pages of color photographs to illustrate the visual appearances of some typical nonlinear optical effects and phenomena. The book could be adopted as a textbook for both undergraduates and graduate students, and serve as a useful reference work for researchers and experts in the fields of physics...
Lugiato, Luigi; Brambilla, Massimo
2015-01-01
Guiding graduate students and researchers through the complex world of laser physics and nonlinear optics, this book provides an in-depth exploration of the dynamics of lasers and other relevant optical systems, under the umbrella of a unitary spatio-temporal vision. Adopting a balanced approach, the book covers traditional as well as special topics in laser physics, quantum electronics and nonlinear optics, treating them from the viewpoint of nonlinear dynamical systems. These include laser emission, frequency generation, solitons, optically bistable systems, pulsations and chaos and optical pattern formation. It also provides a coherent and up-to-date treatment of the hierarchy of nonlinear optical models and of the rich variety of phenomena they describe, helping readers to understand the limits of validity of each model and the connections among the phenomena. It is ideal for graduate students and researchers in nonlinear optics, quantum electronics, laser physics and photonics.
Modeling of the nonlinear resonant response in sedimentary rocks
Energy Technology Data Exchange (ETDEWEB)
Ten Cate, James A [Los Alamos National Laboratory; Shankland, Thomas J [Los Alamos National Laboratory; Vakhnenko, Vyacheslav O [NON LANL; Vakhnenko, Oleksiy [NON LANL
2009-04-03
We suggest a model for describing a wide class of nonlinear and hysteretic effects in sedimentary rocks at longitudinal bar resonance. In particular, we explain: hysteretic behaviour of a resonance curve on both its upward and downward slopes; linear softening of resonant frequency with increase of driving level; gradual (almost logarithmic) recovery of resonant frequency after large dynamical strains; and temporal relaxation of response amplitude at fixed frequency. Starting with a suggested model, we predict the dynamical realization of end-point memory in resonating bar experiments with a cyclic frequency protocol. These theoretical findings were confirmed experimentally at Los Alamos National Laboratory. Sedimentary rocks, particularly sandstones, are distinguished by their grain structure in which each grain is much harder than the intergrain cementation material. The peculiarities of grain and pore structures give rise to a variety of remarkable nonlinear mechanical properties demonstrated by rocks, both at quasistatic and alternating dynamic loading. Thus, the hysteresis earlier established for the stress-strain relation in samples subjected to quasistatic loading-unloading cycles has also been discovered for the relation between acceleration amplitude and driving frequency in bar-shaped samples subjected to an alternating external drive that is frequency-swept through resonance. At strong drive levels there is an unusual, almost linear decrease of resonant frequency with strain amplitude, and there are long-term relaxation phenomena such as nearly logarithmic recovery (increase) of resonant frequency after the large conditioning drive has been removed. In this report we present a short sketch of a model for explaining numerous experimental observations seen in forced longitudinal oscillations of sandstone bars. According to our theory a broad set of experimental data can be understood as various aspects of the same internally consistent pattern. Furthermore
Derivation of an Applied Nonlinear Schroedinger Equation.
Energy Technology Data Exchange (ETDEWEB)
Pitts, Todd Alan; Laine, Mark Richard; Schwarz, Jens; Rambo, Patrick K.; Karelitz, David B.
2015-01-01
We derive from first principles a mathematical physics model useful for understanding nonlinear optical propagation (including filamentation). All assumptions necessary for the development are clearly explained. We include the Kerr effect, Raman scattering, and ionization (as well as linear and nonlinear shock, diffraction and dispersion). We explain the phenomenological sub-models and each assumption required to arrive at a complete and consistent theoretical description. The development includes the relationship between shock and ionization and demonstrates why inclusion of Drude model impedance effects alters the nature of the shock operator. Unclassified Unlimited Release
Derivation of an applied nonlinear Schroedinger equation
Energy Technology Data Exchange (ETDEWEB)
Pitts, Todd Alan [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Laine, Mark Richard [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Schwarz, Jens [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Rambo, Patrick K. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Karelitz, David B. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2015-01-01
We derive from first principles a mathematical physics model useful for understanding nonlinear optical propagation (including filamentation). All assumptions necessary for the development are clearly explained. We include the Kerr effect, Raman scattering, and ionization (as well as linear and nonlinear shock, diffraction and dispersion). We explain the phenomenological sub-models and each assumption required to arrive at a complete and consistent theoretical description. The development includes the relationship between shock and ionization and demonstrates why inclusion of Drude model impedance effects alters the nature of the shock operator. Unclassified Unlimited Release
A spectral characterization of nonlinear normal modes
Cirillo, G. I.; Mauroy, A.; Renson, L.; Kerschen, G.; Sepulchre, R.
2016-09-01
This paper explores the relationship that exists between nonlinear normal modes (NNMs) defined as invariant manifolds in phase space and the spectral expansion of the Koopman operator. Specifically, we demonstrate that NNMs correspond to zero level sets of specific eigenfunctions of the Koopman operator. Thanks to this direct connection, a new, global parametrization of the invariant manifolds is established. Unlike the classical parametrization using a pair of state-space variables, this parametrization remains valid whenever the invariant manifold undergoes folding, which extends the computation of NNMs to regimes of greater energy. The proposed ideas are illustrated using a two-degree-of-freedom system with cubic nonlinearity.
PNNL Stress/Strain Correlation for Zircaloy
Energy Technology Data Exchange (ETDEWEB)
Geelhood, Kenneth J.; Beyer, Carl E.; Luscher, Walter G.
2008-07-18
Pacific Northwest National Laboratory (PNNL) was tasked with incorporating cladding mechanical property data into the Nuclear Regulatory Commission (NRC) fuel codes, FRAPCON-31 and FRAPTRAN2, by the NRC Office of Nuclear Reactor Research. The objective of that task was to create a mechanical model that can calculate true stress, true strain, and the possible failure of the fuel rod cladding based on uniaxial test data.
Stress,strain and earthquake activity
Institute of Scientific and Technical Information of China (English)
Yaolin Shi
2009-01-01
@@ There are 13 papers in this special issue on stress field,crustal deformation and seismicity.The great Wenchuan earthquake is a grievous disaster,but Chinese scientists are trying to learn more from the event in order to understand better the physics of earthquakes for future hazard mitigation planning.
The Application of Stress-Strain Test in Floor Damage Depth Testing%应力应变法在底板破坏深度测试中的应用
Institute of Scientific and Technical Information of China (English)
周江东; 吕育强
2015-01-01
The floor aquiclude of Liu Jialiang coal mine in XuanGang area are faced with water inrush due to Ordovician high pressure water with mining. Controlling and preventing water inrush from coal floor had been the main task ,which need evaluate the floor damage depth under mining. Stress-strain test is used to detect the floor damage depth during mining as a new way, taking the ultimate strain of concrete when it is broken as the standard to evaluate the floor damage depth, good results was achieved that the floor damage depth was 13m Under full-mechanized caving mining.It provided reliable da-ta for rational evaluation of water inrush from floor under mining with pressure in working face 8416.%文中针对轩岗矿区刘家梁煤矿受底板下伏奥陶系灰岩岩溶裂隙水威胁的情况，指出当前底板突水防治成为矿井防治水的主要工作任务，需要探查回采工作对底板的破坏程度。通过采用应力应变法进行底板破坏深度测试，利用混凝土的破坏时产生的极限应变作为判断底板岩层破坏深度的依据，得到综放开采条件下采场底板破坏深度为13 m，为合理评价带压开采条件下8416工作面底板突水提供了可靠的数据支撑。
Zweig, George
2016-05-01
An earlier paper characterizing the linear mechanical response of the organ of Corti [J. Acoust. Soc. Am. 138, 1102-1121 (2015)] is extended to the nonlinear domain. Assuming the existence of nonlinear oscillators nonlocally coupled through the pressure they help create, the oscillator equations are derived and examined when the stimuli are modulated tones and clicks. The nonlinearities are constrained by the requirements of oscillator stability and the invariance of zero crossings in the click response to changes in click amplitude. The nonlinear oscillator equations for tones are solved in terms of the fluid pressure that drives them, and its time derivative, presumably a proxy for forces created by outer hair cells. The pressure equation is reduced to quadrature, the integrand depending on the oscillators' responses. The resulting nonlocally coupled nonlinear equations for the pressure, and oscillator amplitudes and phases, are solved numerically in terms of the fluid pressure at the stapes. Methods for determining the nonlinear damping directly from measurements are described. Once the oscillators have been characterized from their tone and click responses, the mechanical response of the cochlea to natural sounds may be computed numerically. Signal processing inspired by cochlear mechanics opens up a new area of nonlocal nonlinear time-frequency analysis.
Effects of Analog-to-Digital Converter Nonlinearities on Radar Range-Doppler Maps
Energy Technology Data Exchange (ETDEWEB)
Doerry, Armin Walter [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Dubbert, Dale F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Tise, Bertice L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2014-07-01
Radar operation, particularly Ground Moving Target Indicator (GMTI) radar modes, are very sensitive to anomalous effects of system nonlinearities. These throw off harmonic spurs that are sometimes detected as false alarms. One significant source of nonlinear behavior is the Analog to Digital Converter (ADC). One measure of its undesired nonlinearity is its Integral Nonlinearity (INL) specification. We examine in this report the relationship of INL to GMTI performance.
Agrawal, Govind P
2001-01-01
The Optical Society of America (OSA) and SPIE - The International Society for Optical Engineering have awarded Govind Agrawal with an honorable mention for the Joseph W. Goodman Book Writing Award for his work on Nonlinear Fiber Optics, 3rd edition.Nonlinear Fiber Optics, 3rd Edition, provides a comprehensive and up-to-date account of the nonlinear phenomena occurring inside optical fibers. It retains most of the material that appeared in the first edition, with the exception of Chapter 6, which is now devoted to the polarization effects relevant for light propagation in optical
Will Nonlinear Backcalculation Help?
DEFF Research Database (Denmark)
Ullidtz, Per
2000-01-01
demonstrates, that treating the subgrade as a nonlinear elastic material, can result in more realistic moduli and a much better agreement between measured and calculated stresses and strains.The response of nonlinear elastic materials can be calculated using the Finite Element Method (FEM). A much simpler...... approach is to use the Method of Equivalent Thicknesses (MET), modified for a nonlinear subgrade. The paper includes an example where moduli backcalculated using FEM, linear elastic theory and MET are compared. Stresses and strains predicted by the three methods are also compared to measured values...
Nonlinear graphene metamaterial
Nikolaenko, Andrey E; Atmatzakis, Evangelos; Luo, Zhiqiang; Shen, Ze Xiang; De Angelis, Francesco; Boden, Stuart A; Di Fabrizio, Enzo; Zheludev, Nikolay I
2012-01-01
We demonstrate that the broadband nonlinear optical response of graphene can be resonantly enhanced by more than an order of magnitude through hybridization with a plasmonic metamaterial,while retaining an ultrafast nonlinear response time of ~1 ps. Transmission modulation close to ~1% is seen at a pump uence of ~0.03 mJ/cm^2 at the wavelength of ~1600 nm. This approach allows to engineer and enhance graphene's nonlinearity within a broad wavelength range enabling applications in optical switching, mode-locking and pulse shaping.
On the nonlinear anelastic behaviour of AHSS
Torkabadi, A.; Meinders, V.T.; Boogaard, van den A.H.; Cardoso, R.; De Souza Neto, E.; César de Sá, J.M.A.; Adetoro, O.B.
2016-01-01
It has been widely observed that below the yield stress the loading/unloading stress-strain curves of plastically deformed metals are in fact not linear but slightly curved, showing a hysteresis behaviour during unloading/reloading cycles. In addition to the purely elastic strain, extra dislocation
High resolution 3D nonlinear integrated inversion
Institute of Scientific and Technical Information of China (English)
Li Yong; Wang Xuben; Li Zhirong; Li Qiong; Li Zhengwen
2009-01-01
The high resolution 3D nonlinear integrated inversion method is based on nonlinear theory. Under layer control, the log data from several wells (or all wells) in the study area and seismic trace data adjacent to the wells are input to a network with multiple inputs and outputs and are integratedly trained to obtain an adaptive weight function of the entire study area. Integrated nonlinear mapping relationships are built and updated by the lateral and vertical geologic variations of the reservoirs. Therefore, the inversion process and its inversion results can be constrained and controlled and a stable seismic inversion section with high resolution with velocity inversion, impedance inversion, and density inversion sections, can be gained. Good geologic effects have been obtained in model computation tests and real data processing, which verified that this method has high precision, good practicality, and can be used for quantitative reservoir analysis.
Multipolar nonlinear nanophotonics
Smirnova, Daria
2016-01-01
Nonlinear nanophotonics is a rapidly developing field with many useful applications for a design of nonlinear nanoantennas, light sources, nanolasers, sensors, and ultrafast miniature metadevices. A tight confinement of the local electromagnetic fields in resonant photonic nanostructures can boost nonlinear optical effects, thus offering versatile opportunities for subwavelength control of light. To achieve the desired functionalities, it is essential to gain flexible control over the near- and far-field properties of nanostructures. Thus, both modal and multipolar analyses are widely exploited for engineering nonlinear scattering from resonant nanoscale elements, in particular for enhancing the near-field interaction, tailoring the far-field multipolar interference, and optimization of the radiation directionality. Here, we review the recent advances in this recently emerged research field ranging from metallic structures exhibiting localized plasmonic resonances to hybrid metal-dielectric and all-dielectric...
Solitons in nonlinear lattices
Kartashov, Yaroslav V; Torner, Lluis
2010-01-01
This article offers a comprehensive survey of results obtained for solitons and complex nonlinear wave patterns supported by purely nonlinear lattices (NLs), which represent a spatially periodic modulation of the local strength and sign of the nonlinearity, and their combinations with linear lattices. A majority of the results obtained, thus far, in this field and reviewed in this article are theoretical. Nevertheless, relevant experimental settings are surveyed too, with emphasis on perspectives for implementation of the theoretical predictions in the experiment. Physical systems discussed in the review belong to the realms of nonlinear optics (including artificial optical media, such as photonic crystals, and plasmonics) and Bose-Einstein condensation (BEC). The solitons are considered in one, two, and three dimensions (1D, 2D, and 3D). Basic properties of the solitons presented in the review are their existence, stability, and mobility. Although the field is still far from completion, general conclusions c...
Directory of Open Access Journals (Sweden)
Shakeeb Bin Hasan
2014-12-01
Full Text Available Contrary to traditional optical elements, plasmonic antennas made from nanostructured metals permit the localization of electromagnetic fields on length scales much smaller than the wavelength of light. This results in huge amplitudes for the electromagnetic field close to the antenna being conducive for the observation of nonlinear effects already at moderate pump powers. Thus, these antennas exhibit a promising potential to achieve optical frequency conversion and all-optical control of light at the nano-scale. This opens unprecedented opportunities for ultrafast nonlinear spectroscopy, sensing devices, on-chip optical frequency conversion, nonlinear optical metamaterials, and novel photon sources. Here, we review some of the recent advances in exploiting the potential of plasmonic antennas to realize robust nonlinear applications.
Leburn, Christopher; Reid, Derryck
2013-01-01
The field of ultrafast nonlinear optics is broad and multidisciplinary, and encompasses areas concerned with both the generation and measurement of ultrashort pulses of light, as well as those concerned with the applications of such pulses. Ultrashort pulses are extreme events – both in terms of their durations, and also the high peak powers which their short durations can facilitate. These extreme properties make them powerful experiment tools. On one hand, their ultrashort durations facilitate the probing and manipulation of matter on incredibly short timescales. On the other, their ultrashort durations can facilitate high peak powers which can drive highly nonlinear light-matter interaction processes. Ultrafast Nonlinear Optics covers a complete range of topics, both applied and fundamental in nature, within the area of ultrafast nonlinear optics. Chapters 1 to 4 are concerned with the generation and measurement of ultrashort pulses. Chapters 5 to 7 are concerned with fundamental applications of ultrasho...
DEFF Research Database (Denmark)
Nguyen-Duy, Khiem
and remains the prime source of energy in non-terrestrial applications such as those in sky-explorers. However, a renewable energy source is expensive, bulky, and its performance is weather dependent, which make testing of downstream converters very difficult. As a result, a nonlinear source emulator (NSE......) is a good solution to solve the problems associated with the use of real nonlinear sources in testing phases. However, a recent technical survey conducted during this work shows that most existing NSEs have only been concerned with simulating nonlinear systems in terrestrial applications. Furthermore......, their dynamic performance were not fast enough in order to imitate how a real nonlinear energy source would react under extreme conditions and operation modes. Particularly, a system in the sky can experience a step change of sunlight irradiation. Moreover, operation modes may include load step between nominal...
Introduction to nonlinear science
Nicolis, G
1995-01-01
One of the most unexpected results in science in recent years is that quite ordinary systems obeying simple laws can give rise to complex, nonlinear or chaotic, behavior. In this book, the author presents a unified treatment of the concepts and tools needed to analyze nonlinear phenomena and to outline some representative applications drawn from the physical, engineering, and biological sciences. Some of the interesting topics covered include: dynamical systems with a finite number of degrees of freedom, linear stability analysis of fixed points, nonlinear behavior of fixed points, bifurcation analysis, spatially distributed systems, broken symmetries, pattern formation, and chaotic dynamics. The author makes a special effort to provide a logical connection between ordinary dynamical systems and spatially extended systems, and to balance the emphasis on chaotic behavior and more classical nonlinear behavior. He also develops a statistical approach to complex systems and compares it to traditional deterministi...
Nonlinear magnetoinductive transmission lines
Lazarides, Nikos; Tsironis, G P
2011-01-01
Power transmission in one-dimensional nonlinear magnetic metamaterials driven at one end is investigated numerically and analytically in a wide frequency range. The nonlinear magnetic metamaterials are composed of varactor-loaded split-ring resonators which are coupled magnetically through their mutual inductances, forming thus a magnetoiductive transmission line. In the linear limit, significant power transmission along the array only appears for frequencies inside the linear magnetoinductive wave band. We present analytical, closed form solutions for the magnetoinductive waves transmitting the power in this regime, and their discrete frequency dispersion. When nonlinearity is important, more frequency bands with significant power transmission along the array may appear. In the equivalent circuit picture, the nonlinear magnetoiductive transmission line driven at one end by a relatively weak electromotive force, can be modeled by coupled resistive-inductive-capacitive (RLC) circuits with voltage-dependent cap...
Optimization under Nonlinear Constraints
1982-01-01
In this paper a timesaving method is proposed for maximizing likelihood functions when the parameter space is subject to nonlinear constraints, expressible as second order polynomials. The suggested approach is especially attractive when dealing with systems with many parameters.
Nonlinearity in nanomechanical cantilevers
DEFF Research Database (Denmark)
Villanueva Torrijo, Luis Guillermo; Karabalin, R. B.; Matheny, M. H.
2013-01-01
Euler-Bernoulli beam theory is widely used to successfully predict the linear dynamics of micro-and nanocantilever beams. However, its capacity to characterize the nonlinear dynamics of these devices has not yet been rigorously assessed, despite its use in nanoelectromechanical systems development....... These findings underscore the delicate balance between inertial and geometric nonlinear effects in the fundamental mode, and strongly motivate further work to develop theories beyond the Euler-Bernoulli approximation. DOI: 10.1103/PhysRevB.87.024304....... In this article, we report the first highly controlled measurements of the nonlinear response of nanomechanical cantilevers using an ultralinear detection system. This is performed for an extensive range of devices to probe the validity of Euler-Bernoulli theory in the nonlinear regime. We find that its...
Nonlinear Stokes Mueller Polarimetry
Samim, Masood; Barzda, Virginijus
2015-01-01
The Stokes Mueller polarimetry is generalized to include nonlinear optical processes such as second- and third-harmonic generation, sum- and difference-frequency generations. The overall algebraic form of the polarimetry is preserved, where the incoming and outgoing radiations are represented by column vectors and the intervening medium is represented by a matrix. Expressions for the generalized nonlinear Stokes vector and the Mueller matrix are provided in terms of coherency and correlation matrices, expanded by higher-dimensional analogues of Pauli matrices. In all cases, the outgoing radiation is represented by the conventional $4\\times 1$ Stokes vector, while dimensions of the incoming radiation Stokes vector and Mueller matrix depend on the order of the process being examined. In addition, relation between nonlinear susceptibilities and the measured Mueller matrices are explicitly provided. Finally, the approach of combining linear and nonlinear optical elements is discussed within the context of polarim...
Influence of storm magnitude and watershed size on runoff nonlinearity
Lee, Kwan Tun; Huang, Jen-Kuo
2016-06-01
The inherent nonlinear characteristics of the watershed runoff process related to storm magnitude and watershed size are discussed in detail in this study. The first type of nonlinearity is referred to rainfall-runoff dynamic process and the second type is with respect to a Power-law relation between peak discharge and upstream drainage area. The dynamic nonlinearity induced by storm magnitude was first demonstrated by inspecting rainfall-runoff records at three watersheds in Taiwan. Then the derivation of the watershed unit hydrograph (UH) using two linear hydrological models shows that the peak discharge and time to peak discharge that characterize the shape of UH vary event-to-event. Hence, the intention of deriving a unique and universal UH for all rainfall-runoff simulation cases is questionable. In contrast, the UHs by the other two adopted nonlinear hydrological models were responsive to rainfall intensity without relying on linear proportion principle, and are excellent in presenting dynamic nonlinearity. Based on the two-segment regression, the scaling nonlinearity between peak discharge and drainage area was investigated by analyzing the variation of Power-law exponent. The results demonstrate that the scaling nonlinearity is particularly significant for a watershed having larger area and subjecting to a small-size of storm. For three study watersheds, a large tributary that contributes relatively great drainage area or inflow is found to cause a transition break in scaling relationship and convert the scaling relationship from linearity to nonlinearity.
Adaptive and Nonlinear Control
1992-02-29
in [22], we also applied the concept of zero dynamics to the problem of exact linearization of a nonlinear control system by dynamic feedback. Exact ...nonlinear systems, although it was well-known that the conditions for exact linearization are very stringent and consequently do not apply to a broad...29th IEEE Conference n Decision and Control, Invited Paper delivered by Dr. Gilliam. Exact Linearization of Zero Dynamics, 29th IEEE Conference on
Nonlinear Optics and Turbulence
1992-10-01
currently at Queen Mary College, London Patrick Dunne, (Ph.D., 1987, M.I.T., Hydrodynamic Stability, Nonlinear Waves), 1987-1988. Alecsander Dyachenko...U I I I U I I 3 9 3 V. BIOGRAPHIES A. FACULTY BRUCE BAYLY, 31, Ph.D. 1986, Princeton University. Postdoctoral visiting member 1986-88 at Courant...Caputo, A. C. Newell, and M. Shelley , "Nonlinear Wave Propagation Through a Random Medium and Soliton Tunneling", Integrable Systems and
Yang, Qianli; Pitkow, Xaq
2015-03-01
Most interesting natural sensory stimuli are encoded in the brain in a form that can only be decoded nonlinearly. But despite being a core function of the brain, nonlinear population codes are rarely studied and poorly understood. Interestingly, the few existing models of nonlinear codes are inconsistent with known architectural features of the brain. In particular, these codes have information content that scales with the size of the cortical population, even if that violates the data processing inequality by exceeding the amount of information entering the sensory system. Here we provide a valid theory of nonlinear population codes by generalizing recent work on information-limiting correlations in linear population codes. Although these generalized, nonlinear information-limiting correlations bound the performance of any decoder, they also make decoding more robust to suboptimal computation, allowing many suboptimal decoders to achieve nearly the same efficiency as an optimal decoder. Although these correlations are extremely difficult to measure directly, particularly for nonlinear codes, we provide a simple, practical test by which one can use choice-related activity in small populations of neurons to determine whether decoding is suboptimal or optimal and limited by correlated noise. We conclude by describing an example computation in the vestibular system where this theory applies. QY and XP was supported by a grant from the McNair foundation.
Nonlinear Multiantenna Detection Methods
Directory of Open Access Journals (Sweden)
Chen Sheng
2004-01-01
Full Text Available A nonlinear detection technique designed for multiple-antenna assisted receivers employed in space-division multiple-access systems is investigated. We derive the optimal solution of the nonlinear spatial-processing assisted receiver for binary phase shift keying signalling, which we refer to as the Bayesian detector. It is shown that this optimal Bayesian receiver significantly outperforms the standard linear beamforming assisted receiver in terms of a reduced bit error rate, at the expense of an increased complexity, while the achievable system capacity is substantially enhanced with the advent of employing nonlinear detection. Specifically, when the spatial separation expressed in terms of the angle of arrival between the desired and interfering signals is below a certain threshold, a linear beamformer would fail to separate them, while a nonlinear detection assisted receiver is still capable of performing adequately. The adaptive implementation of the optimal Bayesian detector can be realized using a radial basis function network. Two techniques are presented for constructing block-data-based adaptive nonlinear multiple-antenna assisted receivers. One of them is based on the relevance vector machine invoked for classification, while the other on the orthogonal forward selection procedure combined with the Fisher ratio class-separability measure. A recursive sample-by-sample adaptation procedure is also proposed for training nonlinear detectors based on an amalgam of enhanced -means clustering techniques and the recursive least squares algorithm.
Handbook of nonlinear optical crystals
Dmitriev, Valentin G; Nikogosyan, David N
1991-01-01
This Handbook of Nonlinear Optical Crystals provides a complete description of the properties and applications of nonlinear crystals In addition, it presents the most important equations for calculating the main parameters of nonlinear frequency converters This comprehensive reference work will be of great value to all scientists and engineers working in nonlinear optics, quantum electronics and laser physics
Evolutionary quantitative genetics of nonlinear developmental systems.
Morrissey, Michael B
2015-08-01
In quantitative genetics, the effects of developmental relationships among traits on microevolution are generally represented by the contribution of pleiotropy to additive genetic covariances. Pleiotropic additive genetic covariances arise only from the average effects of alleles on multiple traits, and therefore the evolutionary importance of nonlinearities in development is generally neglected in quantitative genetic views on evolution. However, nonlinearities in relationships among traits at the level of whole organisms are undeniably important to biology in general, and therefore critical to understanding evolution. I outline a system for characterizing key quantitative parameters in nonlinear developmental systems, which yields expressions for quantities such as trait means and phenotypic and genetic covariance matrices. I then develop a system for quantitative prediction of evolution in nonlinear developmental systems. I apply the system to generating a new hypothesis for why direct stabilizing selection is rarely observed. Other uses will include separation of purely correlative from direct and indirect causal effects in studying mechanisms of selection, generation of predictions of medium-term evolutionary trajectories rather than immediate predictions of evolutionary change over single generation time-steps, and the development of efficient and biologically motivated models for separating additive from epistatic genetic variances and covariances.
Nonlinear Approaches in Engineering Applications
Jazar, Reza
2012-01-01
Nonlinear Approaches in Engineering Applications focuses on nonlinear phenomena that are common in the engineering field. The nonlinear approaches described in this book provide a sound theoretical base and practical tools to design and analyze engineering systems with high efficiency and accuracy and with less energy and downtime. Presented here are nonlinear approaches in areas such as dynamic systems, optimal control and approaches in nonlinear dynamics and acoustics. Coverage encompasses a wide range of applications and fields including mathematical modeling and nonlinear behavior as applied to microresonators, nanotechnologies, nonlinear behavior in soil erosion,nonlinear population dynamics, and optimization in reducing vibration and noise as well as vibration in triple-walled carbon nanotubes. This book also: Provides a complete introduction to nonlinear behavior of systems and the advantages of nonlinearity as a tool for solving engineering problems Includes applications and examples drawn from the el...
Properties of GH4169 Superalloy Characterized by Nonlinear Ultrasonic Waves
Directory of Open Access Journals (Sweden)
Hongjuan Yan
2015-01-01
Full Text Available The nonlinear wave motion equation is solved by the perturbation method. The nonlinear ultrasonic coefficients β and δ are related to the fundamental and harmonic amplitudes. The nonlinear ultrasonic testing system is used to detect received signals during tensile testing and bending fatigue testing of GH4169 superalloy. The results show that the curves of nonlinear ultrasonic parameters as a function of tensile stress or fatigue life are approximately saddle. There are two stages in relationship curves of relative nonlinear coefficients β′ and δ′ versus stress and fatigue life. The relative nonlinear coefficients β′ and δ′ increase with tensile stress when tensile stress is lower than 65.8% of the yield strength, and they decrease with tensile stress when tensile stress is higher than 65.8% of the yield strength. The nonlinear coefficients have the extreme values at 53.3% of fatigue life. For the second order relative nonlinear coefficient β′, there is good agreement between the experimental data and the comprehensive model. For the third order relative nonlinear coefficient δ′, however, the experiment data does not accord with the theoretical model.
Composite exponential-sine model for dynamic stress-strain curve of soft soil%软土动应力-应变曲线复合指数-正弦模型
Institute of Scientific and Technical Information of China (English)
王伟; 凌华; 孙斌祥
2011-01-01
软土动应力-应变曲线（DSSC）模型是土动力学研究中的一个重要课题。结合软土DSSC的试验规律,分析了其数学模型应具有的基本性质。以最终动强度和初始切线模量为基本参数,对传统双曲线模型和指数模型进行了数学分析。引入动强度因子的概念,揭示了两传统DSSC模型的缺陷。提出了一个软土DSSC复合指数-正弦模型,该模型是一个单调递增、外凸且有极限值的函数。数学分析表明,新模型克服了传统模型的不足,两传统模型均是新模型对应的特例。最后,给出了模型参数的确定方法,通过实测数据拟合验证了新模型的正确性。%Mathematical modeling of dynamic stress-strain curve（DSSC）is important to the study of dynamic behavior of soft soil.Based on an analysis of measured data,the required primary behaviors of DSSC model are analyzed.Ultimate dynamic strength and initial tangent modulus are used to analytically examine the conventional DSSC models,hyperbolic model and exponential model,and a dynamical stress index is proposed and adopted to show the shortcomings of these two models.A composite exponential-sine model of three parameters,or a monotonically increasing and convex function with an upper bound,is developed,and an approach for determinination of model parameters is presented.Mathematical analysis shows that this model can overcome the shortcomings of the two conventional models that are two special cases of the new model,and the modeling results agree with the measured data.
Maganaris, Constantinos N.; Chatzistergos, Panagiotis; Reeves, Neil D.; Narici, Marco V.
2017-01-01
of the stress created by the exercise and is not only reliant upon the type of muscle contraction performed. To better understand the micromechanical behavior and regional adaptability/mal-adaptability of tendon tissue it is important to estimate its internal stress-strain fields. Recent relevant advancements in numerical techniques related to tendon loading are discussed. PMID:28293194
National Research Council Canada - National Science Library
Boštjan Antoncic; Barbara Hvalic Erzetic; Otmar Zorn; Robert D. Hisrich
2007-01-01
... (entrepreneurial maturity) of potential and practicing entrepreneurs. By using the cusp catastrophe model we propose that relationship between education satisfaction and continuation tends to be linear for less experienced entrepreneurs (pre-entrepreneurs...
Nonlinear effect of elastic vortexlike motion on the dynamic stress state of solids
Shilko, Evgeny V.; Grinyaev, Yurii V.; Popov, Mikhail V.; Popov, Valentin L.; Psakhie, Sergey G.
2016-05-01
We present a theoretical analysis of the dynamic stress-strain state of regions in a solid body that are involved in a collective elastic vortexlike motion. It is shown that the initiation of elastic vortexlike motion in the material is accompanied by the appearance of dilatancy and equivalent strain, the magnitudes of which are proportional to the square of the ratio of linear velocity on the periphery of the elastic vortex to the velocity of longitudinal elastic waves (P wave). Under conditions of dynamic loading the described dynamic effects are able to initiate inelastic deformation or destruction of the material at loading speeds of a few percent of the P -wave speed. The obtained analytical estimates suggest that dynamic nonlinear strains can make a significant contribution in a number of widely studied nonlinear dynamic phenomena in solids. Among them are the effect of acoustic (dynamic) dilatancy in solids and granular media, which leads to the generation of longitudinal elastic waves by transverse waves [V. Tournat et al., Phys. Rev. Lett. 92, 085502 (2004), 10.1103/PhysRevLett.92.085502] and the formation of an array of intense "hot spots" (reminiscent of shear-induced hydrodynamic instabilities in fluids) in adiabatic shear bands [P. R. Guduru et al., Phys. Rev. E 64, 036128 (2001), 10.1103/PhysRevE.64.036128].
Food Addiction: An Evolving Nonlinear Science
2014-01-01
The purpose of this review is to familiarize readers with the role that addiction plays in the formation and treatment of obesity, type 2 diabetes and disorders of eating. We will outline several useful models that integrate metabolism, addiction, and human relationship adaptations to eating. A special effort will be made to demonstrate how the use of simple and straightforward nonlinear models can and are being used to improve our knowledge and treatment of patients suffering from nutrition...
Analysis of nonlinear damping properties of carbon
Kazakova, Olga I.; Smolin, Igor Yu.; Bezmozgiy, Iosif M.
2016-11-01
This paper describes research results of nonlinear damping properties of carbon fiber reinforced plastics. The experimental and computational research is performed on flat composite specimens with the gradual structure complication (from 1 to 12 layers). Specimens are subjected to three types of testing which are modal, harmonic and transient analyses. Relationships between the amplitude response and damping ratio are obtained by means of the analysis of variance as the result of this research.
Higher-order nonlinear effects in a Josephson parametric amplifier
Kochetov, Bogdan A.; Fedorov, Arkady
2015-12-01
Nonlinearity of the current-phase relationship of a Josephson junction is the key resource for a Josephson parametric amplifier (JPA) as well as for a Josephson traveling-wave parametric amplifier, the only devices in which the quantum limit for added noise has so far been approached at microwave frequencies. A standard approach to describe JPA takes into account only the lowest order (cubic) nonlinearity resulting in a Duffing-like oscillator equation of motion or in a Kerr-type nonlinearity term in the Hamiltonian. In this paper we derive the quantum expression for the gain of JPA including all orders of the Josephson junction nonlinearity in the linear response regime. We then analyze gain saturation effect for stronger signals within a semiclassical approach. Our results reveal nonlinear effects of higher orders and their implications for operation of a JPA.
The nonlinear standing wave inside the space of liquid
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Based on the basic equations of hydrodynamics, the nonlinear acoustic wave equation is obtained. By taking into account the boundary condition and properties of nonlinear standing wave, the equation is solved through perturbation method, and the stable expressions of fundamental wave and second harmonic are presented. The sound pressures in an ultrasonic cleaner are measured by hydrophones, and the relationship between the received voltages of hydrophones and the output voltages of the ultrasonic generator is researched. The study shows the existence of the nonlinear effect of liquid and analyzes the frequency spectrum of the received signals by hydrophones, by which the fundamental wave, second and high order harmonics are found coexisting in the bounded space filled with liquids. The theory and experimental results testify the existence of the nonlinear standing wave in liquid. Owing to the restricted applicability of perturbation method, the theoretical results of the fundamental wave and second harmonic are good only for the weak nonlinear phenomenon.
Energy Technology Data Exchange (ETDEWEB)
Davis, C.G.
1990-01-01
The advent of nonlinear pulsation theory really coincides with the development of the large computers after the second world war. Christy and Stobbie were the first to make use of finite difference techniques on computers to model the bumps'' observed in the classical Cepheid light and velocity curves, the so-called Hertzsprung'' sequence. Following this work a more sophisticated analysis of the light and velocity curves from the models was made by Simon and Davis using Fourier techniques. Recently a simpler amplitude equation formalism has been developed that helps explain this resonance mechanism. The determination of Population I Cepheid masses by nonlinear methods will be discussed. For the lower mass objects, such as RR Lyrae and BL Her. stars, we find general agreement using evolutionary masses and nonlinear pulsation theory. An apparent difficulty of nonlinear pulsation theory occurs in the understanding of double'' mode pulsation, which will also be discussed. Recent studies in nonlinear pulsation theory have dealt with the question of mode selection, period doubling and the trends towards chaotic behavior such as is observed in the transition from W Virginis to RV Tauri-like stars. 10 refs., 1 fig., 2 tabs.
Nonlinear elastic waves in materials
Rushchitsky, Jeremiah J
2014-01-01
The main goal of the book is a coherent treatment of the theory of propagation in materials of nonlinearly elastic waves of displacements, which corresponds to one modern line of development of the nonlinear theory of elastic waves. The book is divided on five basic parts: the necessary information on waves and materials; the necessary information on nonlinear theory of elasticity and elastic materials; analysis of one-dimensional nonlinear elastic waves of displacement – longitudinal, vertically and horizontally polarized transverse plane nonlinear elastic waves of displacement; analysis of one-dimensional nonlinear elastic waves of displacement – cylindrical and torsional nonlinear elastic waves of displacement; analysis of two-dimensional nonlinear elastic waves of displacement – Rayleigh and Love nonlinear elastic surface waves. The book is addressed first of all to people working in solid mechanics – from the students at an advanced undergraduate and graduate level to the scientists, professional...
Nonlinear Dynamic Force Spectroscopy
Björnham, Oscar
2016-01-01
Dynamic force spectroscopy (DFS) is an experimental technique that is commonly used to assess information of the strength, energy landscape, and lifetime of noncovalent bio-molecular interactions. DFS traditionally requires an applied force that increases linearly with time so that the bio-complex under investigation is exposed to a constant loading rate. However, tethers or polymers can modulate the applied force in a nonlinear regime. For example, bacterial adhesion pili and polymers with worm-like chain properties are examples of structures that show nonlinear force responses. In these situations, the theory for traditional DFS cannot be readily applied. In this work we expand the theory for DFS to also include nonlinear external forces while still maintaining compatibility with the linear DFS theory. To validate the theory we modeled a bio-complex expressed on a stiff, an elastic and a worm-like chain polymer, using Monte Carlo methods, and assessed the corresponding rupture force spectra. It was found th...
Nonlinear optomechanical paddle nanocavities
Kaviani, Hamidreza; Wu, Marcelo; Ghobadi, Roohollah; Barclay, Paul E
2014-01-01
A photonic crystal optomechanical system combining strong nonlinear optomechanical coupling, low effective mass and large optical mode spacing is introduced. This nanoscale "paddle nanocavity" device supports mechanical resonances with effective mass of 300--600 fg which couple nonlinearly to co-localized optical modes with a quadratic optomechanical coupling coefficient $g^{(2)} > 2\\pi\\times400$ MHz/nm$^2$, and a two phonon to single photon optomechanical coupling rate $\\Delta \\omega_0 > 2\\pi\\times 16$ Hz. This coupling relies on strong phonon-photon interactions in a structure whose optical mode spectrum is highly non--degenerate. Simulations indicate that nonlinear optomechanical readout of thermally driven motion in these devices should be observable for T $> 50 $ mK, and that measurement of phonon shot noise is achievable.
Nonlinear dynamics of structures
Oller, Sergio
2014-01-01
This book lays the foundation of knowledge that will allow a better understanding of nonlinear phenomena that occur in structural dynamics. This work is intended for graduate engineering students who want to expand their knowledge on the dynamic behavior of structures, specifically in the nonlinear field, by presenting the basis of dynamic balance in non‐linear behavior structures due to the material and kinematics mechanical effects. Particularly, this publication shows the solution of the equation of dynamic equilibrium for structure with nonlinear time‐independent materials (plasticity, damage and frequencies evolution), as well as those time dependent non‐linear behavior materials (viscoelasticity and viscoplasticity). The convergence conditions for the non‐linear dynamic structure solution are studied, and the theoretical concepts and its programming algorithms are presented.
Nonlinear Photonic Crystal Fibers
DEFF Research Database (Denmark)
Hansen, Kim Per
2004-01-01
, leading to reduced mode confinement and dispersion flexibility. In this thesis, we treat the nonlinear photonic crystal fiber – a special sub-class of photonic crystal fibers, the core of which has a diameter comparable to the wavelength of the light guided in the fiber. The small core results in a large...... nonlinear coefficient and in various applications, it is therefore possible to reduce the required fiber lengths quite dramatically, leading to increased stability and efficiency. Furthermore, it is possible to design these fibers with zero-dispersion at previously unreachable wavelengths, paving the way...... for completely new applications, especially in and near the visible wavelength region. One such application is supercontinuum generation. Supercontinuum generation is extreme broadening of pulses in a nonlinear medium (in this case a small-core fiber), and depending on the dispersion of the fiber, it is possible...
Schmidt, Bruno E; Ernotte, Guilmot; Clerici, Matteo; Morandotti, Roberto; Ibrahim, Heide; Legare, Francois
2016-01-01
In the framework of linear optics, light fields do not interact with each other in a medium. Yet, when their field amplitude becomes comparable to the electron binding energies of matter, the nonlinear motion of these electrons emits new dipole radiation whose amplitude, frequency and phase differ from the incoming fields. Such high fields are typically achieved with ultra-short, femtosecond (1fs = 10-15 sec.) laser pulses containing very broad frequency spectra. Here, the matter not only couples incoming and outgoing fields but also causes different spectral components to interact and mix through a convolution process. In this contribution, we describe how frequency domain nonlinear optics overcomes the shortcomings arising from this convolution in conventional time domain nonlinear optics1. We generate light fields with previously inaccessible properties because the uncontrolled coupling of amplitudes and phases is turned off. For example, arbitrary phase functions are transferred linearly to the second har...
Nonlinear optomechanics with graphene
Shaffer, Airlia; Patil, Yogesh Sharad; Cheung, Hil F. H.; Wang, Ke; Vengalattore, Mukund
2016-05-01
To date, studies of cavity optomechanics have been limited to exploiting the linear interactions between the light and mechanics. However, investigations of quantum signal transduction, quantum enhanced metrology and manybody physics with optomechanics each require strong, nonlinear interactions. Graphene nanomembranes are an exciting prospect for realizing such studies due to their inherently nonlinear nature and low mass. We fabricate large graphene nanomembranes and study their mechanical and optical properties. By using dark ground imaging techniques, we correlate their eigenmode shapes with the measured dissipation. We study their hysteretic response present even at low driving amplitudes, and their nonlinear dissipation. Finally, we discuss ongoing efforts to use these resonators for studies of quantum optomechanics and force sensing. This work is supported by the DARPA QuASAR program through a Grant from the ARO.
Nonlinear Analysis of Buckling
Directory of Open Access Journals (Sweden)
Psotný Martin
2014-06-01
Full Text Available The stability analysis of slender web loaded in compression was presented. To solve this problem, a specialized computer program based on FEM was created. The nonlinear finite element method equations were derived from the variational principle of minimum of potential energy. To obtain the nonlinear equilibrium paths, the Newton-Raphson iteration algorithm was used. Corresponding levels of the total potential energy were defined. The peculiarities of the effects of the initial imperfections were investigated. Special attention was focused on the influence of imperfections on the post-critical buckling mode. The stable and unstable paths of the nonlinear solution were separated. Obtained results were compared with those gained using ANSYS system.
Nonlinear Metamaterials for Holography
Almeida, Euclides; Prior, Yehiam
2015-01-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multi-layer metamaterial holograms where by the nonlinear process of Third Harmonic Generation, a background free image is formed at a new frequency which is the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analyzed and prospects for future device applications are discussed.
Multidimensional nonlinear descriptive analysis
Nishisato, Shizuhiko
2006-01-01
Quantification of categorical, or non-numerical, data is a problem that scientists face across a wide range of disciplines. Exploring data analysis in various areas of research, such as the social sciences and biology, Multidimensional Nonlinear Descriptive Analysis presents methods for analyzing categorical data that are not necessarily sampled randomly from a normal population and often involve nonlinear relations. This reference not only provides an overview of multidimensional nonlinear descriptive analysis (MUNDA) of discrete data, it also offers new results in a variety of fields. The first part of the book covers conceptual and technical preliminaries needed to understand the data analysis in subsequent chapters. The next two parts contain applications of MUNDA to diverse data types, with each chapter devoted to one type of categorical data, a brief historical comment, and basic skills peculiar to the data types. The final part examines several problems and then concludes with suggestions for futu...
Virial Theorem for a Class of Quantum Nonlinear Harmonic Oscillators
Institute of Scientific and Technical Information of China (English)
王雪红; 郭军义; 李艳
2012-01-01
In this paper,the Virial Theorem based on a class of quantum nonlinear harmonic oscillators is presented.This relationship has to do with parameter λ and ?/?λ,where the λ is a real number.When λ=0,the nonlinear harmonic oscillator naturally reduces to the usual quantum linear harmonic oscillator,and the Virial Theorem also reduces to the usual Virial Theorem.
Nonlinear airship aeroelasticity
Bessert, N.; Frederich, O.
2005-12-01
The aeroelastic derivatives for today's aircraft are calculated in the concept phase using a standard procedure. This scheme has to be extended for large airships, due to various nonlinearities in structural and aerodynamic behaviour. In general, the structural model of an airship is physically as well as geometrically nonlinear. The main sources of nonlinearity are large deformations and the nonlinear material behaviour of membranes. The aerodynamic solution is also included in the nonlinear problem, because the deformed airship influences the surrounding flow. Due to these nonlinearities, the aeroelastic problem for airships can only be solved by an iterative procedure. As one possibility, the coupled aerodynamic and structural dynamic problem was handled using linked standard solvers. On the structural side, the Finite-Element program package ABAQUS was extended with an interface to the aerodynamic solver VSAERO. VSAERO is based on the aerodynamic panel method using potential flow theory. The equilibrium of the internal structural and the external aerodynamic forces leads to the structural response and a trimmed flight state for the specified flight conditions (e.g. speed, altitude). The application of small perturbations around a trimmed state produces reaction forces and moments. These constraint forces are then transferred into translational and rotational acceleration fields by performing an inertia relief analysis of the disturbed structural model. The change between the trimmed flight state and the disturbed one yields the respective aeroelastic derivatives. By including the calculated derivatives in the linearised equation of motion system, it is possible to judge the stability and controllability of the investigated airship.
Agrawal, Govind
2012-01-01
Since the 4e appeared, a fast evolution of the field has occurred. The 5e of this classic work provides an up-to-date account of the nonlinear phenomena occurring inside optical fibers, the basis of all our telecommunications infastructure as well as being used in the medical field. Reflecting the big developments in research, this new edition includes major new content: slow light effects, which offers a reduction in noise and power consumption and more ordered network traffic-stimulated Brillouin scattering; vectorial treatment of highly nonlinear fibers; and a brand new chapter o
DEFF Research Database (Denmark)
Mosegaard, Klaus
2012-01-01
For non-linear inverse problems, the mathematical structure of the mapping from model parameters to data is usually unknown or partly unknown. Absence of information about the mathematical structure of this function prevents us from presenting an analytical solution, so our solution depends on our......-heuristics are inefficient for large-scale, non-linear inverse problems, and that the 'no-free-lunch' theorem holds. We discuss typical objections to the relevance of this theorem. A consequence of the no-free-lunch theorem is that algorithms adapted to the mathematical structure of the problem perform more efficiently than...
Fundamentals of nonlinear optics
Powers, Peter E
2011-01-01
Peter Powers's rigorous but simple description of a difficult field keeps the reader's attention throughout. … All chapters contain a list of references and large numbers of practice examples to be worked through. … By carefully working through the proposed problems, students will develop a sound understanding of the fundamental principles and applications. … the book serves perfectly for an introductory-level course for second- and third-order nonlinear optical phenomena. The author's writing style is refreshing and original. I expect that Fundamentals of Nonlinear Optics will fast become pop
Tunable nonlinear graphene metasurfaces
Smirnova, Daria A; Kivshar, Yuri S; Khanikaev, Alexander B
2015-01-01
We introduce the concept of nonlinear graphene metasurfaces employing the controllable interaction between a graphene layer and a planar metamaterial. Such hybrid metasurfaces support two types of subradiant resonant modes, asymmetric modes of structured metamaterial elements ("metamolecules") and graphene plasmons exhibiting strong mutual coupling and avoided dispersion crossing. High tunability of graphene plasmons facilitates strong interaction between the subradiant modes, modifying the spectral position and lifetime of the associated Fano resonances. We demonstrate that strong resonant interaction, combined with the subwavelength localization of plasmons, leads to the enhanced nonlinear response and high efficiency of the second-harmonic generation.
Nonlinear Kalman Filtering in Affine Term Structure Models
DEFF Research Database (Denmark)
Christoffersen, Peter; Dorion, Christian; Jacobs, Kris;
2014-01-01
The extended Kalman filter, which linearizes the relationship between security prices and state variables, is widely used in fixed-income applications. We investigate whether the unscented Kalman filter should be used to capture nonlinearities and compare the performance of the Kalman filter...... with that of the particle filter. We analyze the cross section of swap rates, which are mildly nonlinear in the states, and cap prices, which are highly nonlinear. When caps are used to filter the states, the unscented Kalman filter significantly outperforms its extended counterpart. The unscented Kalman filter also...
Nonlinear effects in optical fibers
Ferreira, Mario F
2011-01-01
Cutting-edge coverage of nonlinear phenomena occurring inside optical fibers Nonlinear fiber optics is a specialized part of fiber optics dealing with optical nonlinearities and their applications. As fiber-optic communication systems have become more advanced and complex, the nonlinear effects in optical fibers have increased in importance, as they adversely affect system performance. Paradoxically, the same nonlinear phenomena also offer the promise of addressing the bandwidth bottleneck for signal processing for future ultra-high speed optical networks. Nonlinear Effects in Optical Fiber
Daniels, Jonathan S.; Anderson, Erik P.; Lee, Thomas H.; Pourmand, Nader
2009-01-01
Impedance biosensors detect the binding of a target to an immobilized probe by quantifying changes in the impedance of the electrode-electrolyte interface. The interface's I-V relationship is inherently nonlinear, varying with DC bias, and target binding can alter the degree of nonlinearity. We propose and demonstrate a method to simultaneously measure the nonlinearity and conventional small-signal impedance using intermodulation products from a two-tone input. Intermodulation amplitudes accurately reflect the impedance's manually-measured voltage dependence. We demonstrate that changes in nonlinearity can discriminate protein binding. Our measurements suggest that target binding can alter nonlinearity via the voltage dependence of the ionic double layer. PMID:19164024
Influence of storm magnitude and watershed size on runoff nonlinearity
Indian Academy of Sciences (India)
Kwan Tun Lee; Jen-Kuo Huang
2016-06-01
The inherent nonlinear characteristics of the watershed runoff process related to storm magnitude andwatershed size are discussed in detail in this study. The first type of nonlinearity is referred to rainfallrunoffdynamic process and the second type is with respect to a Power-law relation between peakdischarge and upstream drainage area. The dynamic nonlinearity induced by storm magnitude was firstdemonstrated by inspecting rainfall-runoff records at three watersheds in Taiwan. Then the derivation ofthe watershed unit hydrograph (UH) using two linear hydrological models shows that the peak dischargeand time to peak discharge that characterize the shape of UH vary event-to-event. Hence, the intentionof deriving a unique and universal UH for all rainfall-runoff simulation cases is questionable. In contrast,the UHs by the other two adopted nonlinear hydrological models were responsive to rainfall intensitywithout relying on linear proportion principle, and are excellent in presenting dynamic nonlinearity.Based on the two-segment regression, the scaling nonlinearity between peak discharge and drainagearea was investigated by analyzing the variation of Power-law exponent. The results demonstrate thatthe scaling nonlinearity is particularly significant for a watershed having larger area and subjecting toa small-size of storm. For three study watersheds, a large tributary that contributes relatively greatdrainage area or inflow is found to cause a transition break in scaling relationship and convert the scalingrelationship from linearity to nonlinearity.
Toward a Nonlinear Acoustic Analogy: Turbulence as a Source of Sound and Nonlinear Propagation
Miller, Steven A. E.
2015-01-01
An acoustic analogy is proposed that directly includes nonlinear propagation effects. We examine the Lighthill acoustic analogy and replace the Green's function of the wave equation with numerical solutions of the generalized Burgers' equation. This is justified mathematically by using similar arguments that are the basis of the solution of the Lighthill acoustic analogy. This approach is superior to alternatives because propagation is accounted for directly from the source to the far-field observer instead of from an arbitrary intermediate point. Validation of a numerical solver for the generalized Burgers' equation is performed by comparing solutions with the Blackstock bridging function and measurement data. Most importantly, the mathematical relationship between the Navier-Stokes equations, the acoustic analogy that describes the source, and canonical nonlinear propagation equations is shown. Example predictions are presented for nonlinear propagation of jet mixing noise at the sideline angle.
Nonlinear elliptic systems with exponential nonlinearities
Directory of Open Access Journals (Sweden)
Said El Manouni
2002-12-01
Full Text Available In this paper we investigate the existence of solutions for {gather*} -mathop{m div}( a(| abla u | ^N| abla u |^{N-2}u = f(x,u,v quad mbox{in } Omega -mathop{m div}(a(| abla v| ^N| abla v |^{N-2}v = g(x,u,v quad mbox{in } Omega u(x = v(x = 0 quad mbox{on }partial Omega. end{gather*} Where $Omega$ is a bounded domain in ${mathbb{R}}^N$, $Ngeq 2$, $f$ and $g$ are nonlinearities having an exponential growth on $Omega$ and $a$ is a continuous function satisfying some conditions which ensure the existence of solutions.
Nonlinearity and disorder: Classification and stability of nonlinear impurity modes
DEFF Research Database (Denmark)
Sukhorukov, Andrey A.; Kivshar, Yuri S.; Bang, Ole
2001-01-01
We study the effects produced by competition of two physical mechanisms of energy localization in inhomogeneous nonlinear systems. As an example, we analyze spatially localized modes supported by a nonlinear impurity in the generalized nonlinear Schrödinger equation and describe three types of no...
Generalized Nonlinear Yule Models
Lansky, Petr; Polito, Federico; Sacerdote, Laura
2016-10-01
With the aim of considering models related to random graphs growth exhibiting persistent memory, we propose a fractional nonlinear modification of the classical Yule model often studied in the context of macroevolution. Here the model is analyzed and interpreted in the framework of the development of networks such as the World Wide Web. Nonlinearity is introduced by replacing the linear birth process governing the growth of the in-links of each specific webpage with a fractional nonlinear birth process with completely general birth rates. Among the main results we derive the explicit distribution of the number of in-links of a webpage chosen uniformly at random recognizing the contribution to the asymptotics and the finite time correction. The mean value of the latter distribution is also calculated explicitly in the most general case. Furthermore, in order to show the usefulness of our results, we particularize them in the case of specific birth rates giving rise to a saturating behaviour, a property that is often observed in nature. The further specialization to the non-fractional case allows us to extend the Yule model accounting for a nonlinear growth.
Ritz, Christian; Parmigiani, Giovanni
2009-01-01
R is a rapidly evolving lingua franca of graphical display and statistical analysis of experiments from the applied sciences. This book provides a coherent treatment of nonlinear regression with R by means of examples from a diversity of applied sciences such as biology, chemistry, engineering, medicine and toxicology.
Gorban, A. N.; Karlin, I.V.
2003-01-01
Nonlinear kinetic equations are reviewed for a wide audience of specialists and postgraduate students in physics, mathematical physics, material science, chemical engineering and interdisciplinary research. Contents: The Boltzmann equation, Phenomenology and Quasi-chemical representation of the Boltzmann equation, Kinetic models, Discrete velocity models, Direct simulation, Lattice Gas and Lattice Boltzmann models, Minimal Boltzmann models for flows at low Knudsen number, Other kinetic equati...
Intramolecular and nonlinear dynamics
Energy Technology Data Exchange (ETDEWEB)
Davis, M.J. [Argonne National Laboratory, IL (United States)
1993-12-01
Research in this program focuses on three interconnected areas. The first involves the study of intramolecular dynamics, particularly of highly excited systems. The second area involves the use of nonlinear dynamics as a tool for the study of molecular dynamics and complex kinetics. The third area is the study of the classical/quantum correspondence for highly excited systems, particularly systems exhibiting classical chaos.
DEFF Research Database (Denmark)
Jørgensen, Michael Finn
1995-01-01
It is generally very difficult to solve nonlinear systems, and such systems often possess chaotic solutions. In the rare event that a system is completely solvable, it is said to integrable. Such systems never have chaotic solutions. Using the Inverse Scattering Transform Method (ISTM) two...
Nonlinear phased array imaging
Croxford, Anthony J.; Cheng, Jingwei; Potter, Jack N.
2016-04-01
A technique is presented for imaging acoustic nonlinearity within a specimen using ultrasonic phased arrays. Acoustic nonlinearity is measured by evaluating the difference in energy of the transmission bandwidth within the diffuse field produced through different focusing modes. The two different modes being classical beam forming, where delays are applied to different element of a phased array to physically focus the energy at a single location (parallel firing) and focusing in post processing, whereby one element at a time is fired and a focused image produced in post processing (sequential firing). Although these two approaches are linearly equivalent the difference in physical displacement within the specimen leads to differences in nonlinear effects. These differences are localized to the areas where the amplitude is different, essentially confining the differences to the focal point. Direct measurement at the focal point are however difficult to make. In order to measure this the diffuse field is used. It is a statistical property of the diffuse field that it represents the total energy in the system. If the energy in the diffuse field for both the sequential and parallel firing case is measured then the difference between these, within the input signal bandwidth, is largely due to differences at the focal spot. This difference therefore gives a localized measurement of where energy is moving out of the transmission bandwidth due to nonlinear effects. This technique is used to image fatigue cracks and other damage types undetectable with conventional linear ultrasonic measurements.
Generalized Nonlinear Yule Models
Lansky, Petr; Polito, Federico; Sacerdote, Laura
2016-11-01
With the aim of considering models related to random graphs growth exhibiting persistent memory, we propose a fractional nonlinear modification of the classical Yule model often studied in the context of macroevolution. Here the model is analyzed and interpreted in the framework of the development of networks such as the World Wide Web. Nonlinearity is introduced by replacing the linear birth process governing the growth of the in-links of each specific webpage with a fractional nonlinear birth process with completely general birth rates. Among the main results we derive the explicit distribution of the number of in-links of a webpage chosen uniformly at random recognizing the contribution to the asymptotics and the finite time correction. The mean value of the latter distribution is also calculated explicitly in the most general case. Furthermore, in order to show the usefulness of our results, we particularize them in the case of specific birth rates giving rise to a saturating behaviour, a property that is often observed in nature. The further specialization to the non-fractional case allows us to extend the Yule model accounting for a nonlinear growth.
Trirefringence in nonlinear metamaterials
De Lorenci, Vitorio A
2012-01-01
We study the propagation of electromagnetic waves in the limit of geometrical optics for a class of nearly transparent nonlinear uniaxial metamaterials for which their permittivity tensors present a negative principal component. Their permeability are assumed positive and dependent on the electric field. We show that light waves experience triple refraction -- trirefringence. Additionally to the ordinary wave, two extraordinary waves propagate in such media.
Borghi, M.; Castellan, C.; Signorini, S.; Trenti, A.; Pavesi, L.
2017-09-01
Silicon photonics is a technology based on fabricating integrated optical circuits by using the same paradigms as the dominant electronics industry. After twenty years of fervid development, silicon photonics is entering the market with low cost, high performance and mass-manufacturable optical devices. Until now, most silicon photonic devices have been based on linear optical effects, despite the many phenomenologies associated with nonlinear optics in both bulk materials and integrated waveguides. Silicon and silicon-based materials have strong optical nonlinearities which are enhanced in integrated devices by the small cross-section of the high-index contrast silicon waveguides or photonic crystals. Here the photons are made to strongly interact with the medium where they propagate. This is the central argument of nonlinear silicon photonics. It is the aim of this review to describe the state-of-the-art in the field. Starting from the basic nonlinearities in a silicon waveguide or in optical resonator geometries, many phenomena and applications are described—including frequency generation, frequency conversion, frequency-comb generation, supercontinuum generation, soliton formation, temporal imaging and time lensing, Raman lasing, and comb spectroscopy. Emerging quantum photonics applications, such as entangled photon sources, heralded single-photon sources and integrated quantum photonic circuits are also addressed at the end of this review.
Nonlinear fibre optics overview
DEFF Research Database (Denmark)
Travers, J. C.; Frosz, Michael Henoch; Dudley, J. M.
2010-01-01
, provides a background to the associated nonlinear optical processes, treats the generation mechanisms from continuous wave to femtosecond pulse pump regimes and highlights the diverse applications. A full discussion of numerical methods and comprehensive computer code are also provided, enabling readers...
Tsia, Kevin K.; Jalali, Bahram
2010-05-01
An intriguing optical property of silicon is that it exhibits a large third-order optical nonlinearity, with orders-ofmagnitude larger than that of silica glass in the telecommunication band. This allows efficient nonlinear optical interaction at relatively low power levels in a small footprint. Indeed, we have witnessed a stunning progress in harnessing the Raman and Kerr effects in silicon as the mechanisms for enabling chip-scale optical amplification, lasing, and wavelength conversion - functions that until recently were perceived to be beyond the reach of silicon. With all the continuous efforts developing novel techniques, nonlinear silicon photonics is expected to be able to reach even beyond the prior achievements. Instead of providing a comprehensive overview of this field, this manuscript highlights a number of new branches of nonlinear silicon photonics, which have not been fully recognized in the past. In particular, they are two-photon photovoltaic effect, mid-wave infrared (MWIR) silicon photonics, broadband Raman effects, inverse Raman scattering, and periodically-poled silicon (PePSi). These novel effects and techniques could create a new paradigm for silicon photonics and extend its utility beyond the traditionally anticipated applications.
Leitao, J C; Gerlach, M; Altmann, E G
2016-01-01
One of the most celebrated findings in complex systems in the last decade is that different indexes y (e.g., patents) scale nonlinearly with the population~x of the cities in which they appear, i.e., $y\\sim x^\\beta, \\beta \
Nonlinear Gravitational Lagrangians revisited
Magnano, Guido
2016-01-01
The Legendre transformation method, applied in 1987 to deal with purely metric gravitational Lagrangians with nonlinear dependence on the Ricci tensor, is extended to metric-affine models and is shown to provide a concise and insightful comparison of the dynamical content of the two variational frameworks.
Nonlinearities in Microwave Superconductivity
Ledenyov, Dimitri O.; Ledenyov, Viktor O.
2012-01-01
The research is focused on the modeling of nonlinear properties of High Temperature Superconducting (HTS) thin films, using Bardeen, Cooper, Schrieffer and Lumped Element Circuit theories, with purpose to enhance microwave power handling capabilities of microwave filters and optimize design of microwave circuits in micro- and nano- electronics.
Nonlinear tsunami generation mechanism
Directory of Open Access Journals (Sweden)
M. A. Nosov
2001-01-01
Full Text Available The nonlinear mechanism of long gravitational surface water wave generation by high-frequency bottom oscillations in a water layer of constant depth is investigated analytically. The connection between the surface wave amplitude and the parameters of bottom oscillations and source length is investigated.
DEFF Research Database (Denmark)
Mosekilde, Erik
Through a significant number of detailed and realistic examples this book illustrates how the insights gained over the past couple of decades in the fields of nonlinear dynamics and chaos theory can be applied in practice. Aomng the topics considered are microbiological reaction systems, ecological...
Terahertz semiconductor nonlinear optics
DEFF Research Database (Denmark)
Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias
2013-01-01
nonlinearity in doped semiconductors originates from the near-instantaneous heating of free electrons in the ponderomotive potential created by electric field of the THz pulse, leading to ultrafast increase of electron effective mass by intervalley scattering. Modification of effective mass in turn leads...
Nonlinear Kalman Filtering in Affine Term Structure Models
DEFF Research Database (Denmark)
Christoffersen, Peter; Dorion, Christian; Jacobs, Kris;
When the relationship between security prices and state variables in dynamic term structure models is nonlinear, existing studies usually linearize this relationship because nonlinear fi…ltering is computationally demanding. We conduct an extensive investigation of this linearization and analyze...... Monte Carlo experiment demonstrates that the unscented Kalman fi…lter is much more accurate than its extended counterpart in fi…ltering the states and forecasting swap rates and caps. Our fi…ndings suggest that the unscented Kalman fi…lter may prove to be a good approach for a number of other problems...... in fi…xed income pricing with nonlinear relationships between the state vector and the observations, such as the estimation of term structure models using coupon bonds and the estimation of quadratic term structure models....
Nonlinear Optical Terahertz Technology Project
National Aeronautics and Space Administration — Our approach is based on high-Q optical WGM resonators made with a nonlinear crystal. Such resonators have been demonstrated to dramatically enhance nonlinear...
Phase retrieval using nonlinear diversity.
Lu, Chien-Hung; Barsi, Christopher; Williams, Matthew O; Kutz, J Nathan; Fleischer, Jason W
2013-04-01
We extend the Gerchberg-Saxton algorithm to phase retrieval in a nonlinear system. Using a tunable photorefractive crystal, we experimentally demonstrate the noninterferometric technique by reconstructing an unknown phase object from optical intensity measurements taken at different nonlinear strengths.
Strong nonlinear oscillators analytical solutions
Cveticanin, Livija
2017-01-01
This book outlines an analytical solution procedure of the pure nonlinear oscillator system, offering a solution for free and forced vibrations of the one-degree-of-freedom strong nonlinear system with constant and time variable parameter. Includes exercises.
Numerical Method for Modeling the Constitutive Relationship of Sand under Different Stress Paths
Institute of Scientific and Technical Information of China (English)
Ren Qingyang; Wang Jingtao
2005-01-01
A numerical method was used in order to establish the constitutive relationship of sands under different stress paths. Firstly, based on the numerical method modeling the constitutive law of sands, the elastoplastic constitutive relationship of sand was established for three paths: the constant proportion of principle stress path, the conventional triaxial compression (CTC) path, and the p=constant (TC) path. The yield lines of plastic volumetric strain and plastic generalized shear strain were given. Through visualization, the three dimensional surface of the stress-strain relationship in the whole stress field (p, q) obtained under the three paths was plotted. Also, by comparing the stress-strain surfaces and yield locus of the three stress paths, the differences were found to be obvious, which demonstrates that the influence of the stress paths on constitutive law was not neglected. The numerical modeling method overcame the difficulty of finding an analytical expression for plastic potential. The results simulated the experimental data with an accuracy of 90 % on average, so the constitutive model established in this paper provides an effective constitutive equation for this kind of engineering, reflecting the effect of practical stress paths that occur in sands.
Cubication of Conservative Nonlinear Oscillators
Belendez, Augusto; Alvarez, Mariela L.; Fernandez, Elena; Pascual, Immaculada
2009-01-01
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear…
Terahertz Nonlinear Optics in Semiconductors
DEFF Research Database (Denmark)
Turchinovich, Dmitry; Hvam, Jørn Märcher; Hoffmann, Matthias C.
2013-01-01
We demonstrate the nonlinear optical effects – selfphase modulation and saturable absorption of a single-cycle THz pulse in a semiconductor. Resulting from THz-induced modulation of Drude plasma, these nonlinear optical effects, in particular, lead to self-shortening and nonlinear spectral...
Fault Detection for Nonlinear Systems
DEFF Research Database (Denmark)
Stoustrup, Jakob; Niemann, H.H.
1998-01-01
The paper describes a general method for designing fault detection and isolation (FDI) systems for nonlinear processes. For a rich class of nonlinear systems, a nonlinear FDI system can be designed using convex optimization procedures. The proposed method is a natural extension of methods based...
Nonlinear electrostatic drift Kelvin-Helmholtz instability
Sharma, Avadhesh C.; Srivastava, Krishna M.
1993-01-01
Nonlinear analysis of electrostatic drift Kelvin-Helmholtz instability is performed. It is shown that the analysis leads to the propagation of the weakly nonlinear dispersive waves, and the nonlinear behavior is governed by the nonlinear Burger's equation.
Horowitz, A; Sheinman, I; Lanir, Y
1988-02-01
A three dimensional incompressible and geometrically as well as materially nonlinear finite element is formulated for future implementation in models of cardiac mechanics. The stress-strain relations in the finite element are derived from a recently proposed constitutive law which is based on the histological composition of the myocardium. The finite element is formulated for large deformations and considers incompressibility by introducing the hydrostatic pressure as an additional variable. The results of passive loading cases simulated by this element allow to analyze the mechanical properties of ventricular wall segments, the main of which are that the circumferential direction is stiffer than the longitudinal one, that its shear stiffness is considerably lower than its tensile and compressive stiffness and that, due to its mechanically prominent role, the collagenous matrix may affect the myocardial perfusion.
Optothermal nonlinearity of silica aerogel
Braidotti, Maria Chiara; Fleming, Adam; Samuels, Michiel C; Di Falco, Andrea; Conti, Claudio
2016-01-01
We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass $(\\simeq 10^{-12} $m$^2/$W), with negligible optical nonlinear absorption. The non\\-li\\-near coefficient can be increased to values in the range of $10^{-10} $m$^2/$W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.
Insights into alkali-silica reaction damage in mortar through acoustic nonlinearity
Rashidi, M.; Kim, J.-Y.; Jacobs, L. J.; Kurtis, K. E.
2016-02-01
The progression of damage as a result of alkali-silica reaction in mortar samples is monitored by using the Nonlinear Impact Resonance Acoustic Spectroscopy (NIRAS) method and expansion measurements, which were performed daily. Results of this study show a strong correlation between the cumulative average nonlinearity parameter and expansion for each sample type, and a strong linear relationship between fourteen-day expansion and the cumulative average nonlinearity of among sample types. In addition to the cumulative average nonlinearity parameter, the standard deviation of average nonlinearity parameter shows strong correlation with the fourteen-day expansion of sample types. Results provide insights to the relationship with the acoustic nonlinearity and damage caused by the ASR.
Essentials of nonlinear optics
Murti, Y V G S
2014-01-01
Current literature on Nonlinear Optics varies widely in terms of content, style, and coverage of specific topics, relative emphasis of areas and the depth of treatment. While most of these books are excellent resources for the researchers, there is a strong need for books appropriate for presenting the subject at the undergraduate or postgraduate levels in Universities. The need for such a book to serve as a textbook at the level of the bachelors and masters courses was felt by the authors while teaching courses on nonlinear optics to students of both science and engineering during the past two decades. This book has emerged from an attempt to address the requirement of presenting the subject at college level. A one-semester course covering the essentials can effectively be designed based on this.
Nonlinear metamaterials for holography
Almeida, Euclides; Bitton, Ora; Prior, Yehiam
2016-08-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency--the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed.
Nonlinear metamaterials for holography
Almeida, Euclides; Bitton, Ora
2016-01-01
A hologram is an optical element storing phase and possibly amplitude information enabling the reconstruction of a three-dimensional image of an object by illumination and scattering of a coherent beam of light, and the image is generated at the same wavelength as the input laser beam. In recent years, it was shown that information can be stored in nanometric antennas giving rise to ultrathin components. Here we demonstrate nonlinear multilayer metamaterial holograms. A background free image is formed at a new frequency—the third harmonic of the illuminating beam. Using e-beam lithography of multilayer plasmonic nanoantennas, we fabricate polarization-sensitive nonlinear elements such as blazed gratings, lenses and other computer-generated holograms. These holograms are analysed and prospects for future device applications are discussed. PMID:27545581
Van Leeuwen, Peter Jan; Reich, Sebastian
2015-01-01
This book contains two review articles on nonlinear data assimilation that deal with closely related topics but were written and can be read independently. Both contributions focus on so-called particle filters. The first contribution by Jan van Leeuwen focuses on the potential of proposal densities. It discusses the issues with present-day particle filters and explorers new ideas for proposal densities to solve them, converging to particle filters that work well in systems of any dimension, closing the contribution with a high-dimensional example. The second contribution by Cheng and Reich discusses a unified framework for ensemble-transform particle filters. This allows one to bridge successful ensemble Kalman filters with fully nonlinear particle filters, and allows a proper introduction of localization in particle filters, which has been lacking up to now.
Nonlinearity without Superluminality
Kent, A
2002-01-01
Quantum theory is compatible with special relativity. In particular, though measurements on entangled systems are correlated in a way that cannot be reproduced by local hidden variables, they cannot be used for superluminal signalling. As Gisin and Polchinski first pointed out, this is not true for general nonlinear modifications of the Schroedinger equation. Excluding superluminal signalling has thus been taken to rule out most nonlinear versions of quantum theory. The no superluminal signalling constraint has also been used for alternative derivations of the optimal fidelities attainable for imperfect quantum cloning and other operations. These results apply to theories satisfying the rule that their predictions for widely separated and slowly moving entangled systems can be approximated by non-relativistic equations of motion with respect to a preferred time coordinate. This paper describes a natural way in which this rule might fail to hold. In particular, it is shown that quantum readout devices which di...
Monte Carlo and nonlinearities
Dauchet, Jérémi; Blanco, Stéphane; Caliot, Cyril; Charon, Julien; Coustet, Christophe; Hafi, Mouna El; Eymet, Vincent; Farges, Olivier; Forest, Vincent; Fournier, Richard; Galtier, Mathieu; Gautrais, Jacques; Khuong, Anaïs; Pelissier, Lionel; Piaud, Benjamin; Roger, Maxime; Terrée, Guillaume; Weitz, Sebastian
2016-01-01
The Monte Carlo method is widely used to numerically predict systems behaviour. However, its powerful incremental design assumes a strong premise which has severely limited application so far: the estimation process must combine linearly over dimensions. Here we show that this premise can be alleviated by projecting nonlinearities on a polynomial basis and increasing the configuration-space dimension. Considering phytoplankton growth in light-limited environments, radiative transfer in planetary atmospheres, electromagnetic scattering by particles and concentrated-solar-power-plant productions, we prove the real world usability of this advance on four test-cases that were so far regarded as impracticable by Monte Carlo approaches. We also illustrate an outstanding feature of our method when applied to sharp problems with interacting particles: handling rare events is now straightforward. Overall, our extension preserves the features that made the method popular: addressing nonlinearities does not compromise o...
Nonlinear Photonics 2014: introduction.
Akhmediev, N; Kartashov, Yaroslav
2015-01-12
International Conference "Nonlinear Photonics-2014" took place in Barcelona, Spain on July 27-31, 2014. It was a part of the "Advanced Photonics Congress" which is becoming a traditional notable event in the world of photonics. The current focus issue of Optics Express contains contributions from the participants of the Conference and the Congress. The articles in this focus issue by no means represent the total number of the congress contributions (around 400). However, it demonstrates wide range of topics covered at the event. The next conference of this series is to be held in 2016 in Australia, which is the home of many researchers working in the field of photonics in general and nonlinear photonics in particular.
Huang, Chun-Yuh; Stankiewicz, Anna; Ateshian, Gerard A; Mow, Van C
2005-04-01
The tensile and compressive properties of human glenohumeral cartilage were determined by testing 120 rectangular strips in uniaxial tension and 70 cylindrical plugs in confined compression, obtained from five human glenohumeral joints. Specimens were harvested from five regions across the articular surface of the humeral head and two regions on the glenoid. Tensile strips were obtained along two orientations, parallel and perpendicular to the split-line directions. Two serial slices through the thickness, corresponding to the superficial and middle zones of the cartilage layers, were prepared from each tensile strip and each compressive plug. The equilibrium tensile modulus and compressive aggregate modulus of cartilage were determined from the uniaxial tensile and confined compression tests, respectively. Significant differences in the tensile moduli were found with depth and orientation relative to the local split-line direction. Articular cartilage of the humeral head was significantly stiffer in tension than that of the glenoid. There were significant differences in the aggregate compressive moduli of articular cartilage between superficial and middle zones in the humeral head. Furthermore, tensile and compressive stress-strain responses exhibited nonlinearity under finite strain, while the tensile modulus differed by up to two orders of magnitude from the compressive aggregate modulus at 0% strain, demonstrating a high degree of tension-compression nonlinearity. The complexity of the mechanical properties of human glenohumeral cartilage was exposed in this study, showing anisotropy, inhomogeneity, and tension-compression nonlinearity within the same joint. The observed differences in the tensile properties of human glenohumeral cartilage suggest that the glenoid may be more susceptible to cartilage degeneration than the humeral head.
Fourier series expansion for nonlinear Hamiltonian oscillators.
Méndez, Vicenç; Sans, Cristina; Campos, Daniel; Llopis, Isaac
2010-06-01
The problem of nonlinear Hamiltonian oscillators is one of the classical questions in physics. When an analytic solution is not possible, one can resort to obtaining a numerical solution or using perturbation theory around the linear problem. We apply the Fourier series expansion to find approximate solutions to the oscillator position as a function of time as well as the period-amplitude relationship. We compare our results with other recent approaches such as variational methods or heuristic approximations, in particular the Ren-He's method. Based on its application to the Duffing oscillator, the nonlinear pendulum and the eardrum equation, it is shown that the Fourier series expansion method is the most accurate.
Nonlinear optics of astaxanthin thin films
Esser, A.; Fisch, Herbert; Haas, Karl-Heinz; Haedicke, E.; Paust, J.; Schrof, Wolfgang; Ticktin, Anton
1993-02-01
Carotinoids exhibit large nonlinear optical properties due to their extended (pi) -electron system. Compared to other polyenes which show a broad distribution of conjugation lengths, carotinoids exhibit a well defined molecular structure, i.e. a well defined conjugation length. Therefore the carotinoid molecules can serve as model compounds to study the relationship between structure and nonlinear optical properties. In this paper the synthesis of four astaxanthins with C-numbers ranging from 30 to 60, their preparation into thin films, wavelength dispersive Third Harmonic Generation (THG) measurements and some molecular modelling calculations will be presented. Resonant (chi) (3) values reach 1.2(DOT)10-10 esu for C60 astaxanthin. In the nonresonant regime a figure of merit (chi) (3)/(alpha) of several 10-13 esu-cm is demonstrated.
Nonlinear analysis of RED - a comparative study
Energy Technology Data Exchange (ETDEWEB)
Jiang Kai; Wang Xiaofan E-mail: xfwang@sjtu.edu.cn; Xi Yugeng
2004-09-01
Random Early Detection (RED) is an active queue management (AQM) mechanism for routers on the Internet. In this paper, performance of RED and Adaptive RED are compared from the viewpoint of nonlinear dynamics. In particular, we reveal the relationship between the performance of the network and its nonlinear dynamical behavior. We measure the maximal Lyapunov exponent and Hurst parameter of the average queue length of RED and Adaptive RED, as well as the throughput and packet loss rate of the aggregate traffic on the bottleneck link. Our simulation scenarios include FTP flows and Web flows, one-way and two-way traffic. In most situations, Adaptive RED has smaller maximal Lyapunov exponents, lower Hurst parameters, higher throughput and lower packet loss rate than that of RED. This confirms that Adaptive RED has better performance than RED.
Nonlinear fractional relaxation
Indian Academy of Sciences (India)
A Tofighi
2012-04-01
We deﬁne a nonlinear model for fractional relaxation phenomena. We use -expansion method to analyse this model. By studying the fundamental solutions of this model we ﬁnd that when → 0 the model exhibits a fast decay rate and when → ∞ the model exhibits a power-law decay. By analysing the frequency response we ﬁnd a logarithmic enhancement for the relative ratio of susceptibility.
Indian Academy of Sciences (India)
Ramaswamy Jaganathan; Sudeshna Sinha
2005-03-01
Motivated by studies on -deformed physical systems related to quantum group structures, and by the elements of Tsallis statistical mechanics, the concept of -deformed nonlinear maps is introduced. As a specific example, a -deformation procedure is applied to the logistic map. Compared to the canonical logistic map, the resulting family of -logistic maps is shown to have a wider spectrum of interesting behaviours, including the co-existence of attractors – a phenomenon rare in one-dimensional maps.
Controllability of nonlinear systems.
Sussmann, H. J.; Jurdjevic, V.
1972-01-01
Discussion of the controllability of nonlinear systems described by the equation dx/dt - F(x,u). Concepts formulated by Chow (1939) and Lobry (1970) are applied to establish criteria for F and its derivatives to obtain qualitative information on sets which can be obtained from x which denotes a variable of state in an arbitrary, real, analytical manifold. It is shown that controllability implies strong accessibility for a large class of manifolds including Euclidean spaces.-
Stochastic Nonlinear Aeroelasticity
2009-01-01
STOCHASTIC NONLINEAR AEROELASTICITY 5a. CONTRACT NUMBER In- house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 0601102 6. AUTHOR(S) Philip S...ABSTRACT This report documents the culmination of in- house work in the area of uncertainty quantification and probabilistic techniques for... coff U∞ cs ea lw cw Figure 6: Wing and store geometry (left), wing box structural model (middle), flutter distribution (right
2007-03-01
IEEE Transactions on Automatic Control , AC- 48, pp. 1712-1723, (2003). [14] C.I. Byrnes, A. Isidori...Nonlinear internal models for output regulation,” IEEE Transactions on Automatic Control , AC-49, pp. 2244-2247, (2004). [15] C.I. Byrnes, F. Celani, A...approach,” IEEE Transactions on Automatic Control , 48 (Dec. 2003), 2172–2190. 2. C. I. Byrnes, “Differential Forms and Dynamical Systems,” to appear
Filamentation with nonlinear Bessel vortices.
Jukna, V; Milián, C; Xie, C; Itina, T; Dudley, J; Courvoisier, F; Couairon, A
2014-10-20
We present a new type of ring-shaped filaments featured by stationary nonlinear high-order Bessel solutions to the laser beam propagation equation. Two different regimes are identified by direct numerical simulations of the nonlinear propagation of axicon focused Gaussian beams carrying helicity in a Kerr medium with multiphoton absorption: the stable nonlinear propagation regime corresponds to a slow beam reshaping into one of the stationary nonlinear high-order Bessel solutions, called nonlinear Bessel vortices. The region of existence of nonlinear Bessel vortices is found semi-analytically. The influence of the Kerr nonlinearity and nonlinear losses on the beam shape is presented. Direct numerical simulations highlight the role of attractors played by nonlinear Bessel vortices in the stable propagation regime. Large input powers or small cone angles lead to the unstable propagation regime where nonlinear Bessel vortices break up into an helical multiple filament pattern or a more irregular structure. Nonlinear Bessel vortices are shown to be sufficiently intense to generate a ring-shaped filamentary ionized channel in the medium which is foreseen as opening the way to novel applications in laser material processing of transparent dielectrics.
Strongly nonlinear oscillators analytical solutions
Cveticanin, Livija
2014-01-01
This book provides the presentation of the motion of pure nonlinear oscillatory systems and various solution procedures which give the approximate solutions of the strong nonlinear oscillator equations. The book presents the original author’s method for the analytical solution procedure of the pure nonlinear oscillator system. After an introduction, the physical explanation of the pure nonlinearity and of the pure nonlinear oscillator is given. The analytical solution for free and forced vibrations of the one-degree-of-freedom strong nonlinear system with constant and time variable parameter is considered. Special attention is given to the one and two mass oscillatory systems with two-degrees-of-freedom. The criteria for the deterministic chaos in ideal and non-ideal pure nonlinear oscillators are derived analytically. The method for suppressing chaos is developed. Important problems are discussed in didactic exercises. The book is self-consistent and suitable as a textbook for students and also for profess...
Quantum well nonlinear microcavities
Oudar, J. L.; Kuszelewicz, R.; Sfez, B.; Pellat, D.; Azoulay, R.
We report on recent progress in reducing the power threshold of all-optical bistable quantum well vertical microcavities. Significant improvements are achieved through an increase of the cavity finesse, together with a reduction of the device active layer thickness. A critical intensity of 5 μW/μm 2 has been observed on a microcavity of finesse 250, with a nonlinear medium of only 18 GaAs quantum wells of 10 nm thickness. Further improvements of the Bragg mirror quality resulted in a finesse of 700 and a power-lifetime product of 15 fJ/μm 2. Microresonator pixellation allows to obtain 2-dimensional arrays. A thermally-induced alloy-mixing technique is described, which produced a 110 meV carrier confinement energy, together with a refractive index change of -.012, averaged over the 2.6 μm nonlinear medium thickness. The resulting electrical and optical confinement is shown to improve the nonlinear characteristics, by limiting lateral carrier diffusion and light diffraction.
Robust Absolute Stability of General Interval Lur'e Type Nonlinear Control Systems
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
In this paper, Lyapunov function method isused to study the robust absolute stability of general interval Lur'e type nonlinear control systems. As a result, algebraically sufficient conditions with interval matrix inequality form are obtained for the general interval Lur'e type nonlinear control systems, thus the relationship between the stability of symmetrical interval matrix and the robust absolute stability of general interval Lur'e type nonlinear control systems is established.
Geometric and material nonlinear analysis of tensegrity structures
Institute of Scientific and Technical Information of China (English)
Hoang Chi Tran; Jaehong Lee
2011-01-01
A numerical method is presented for the large deflection in elastic analysis of tensegrity structures including both geometric and material nonlinearities.The geometric nonlinearity is considered based on both total Lagrangian and updated Lagrangian formulations,while the material nonlinearity is treated through elastoplastic stressstrain relationship.The nonlinear equilibrium equations are solved using an incremental-iterative scheme in conjunction with the modified Newton-Raphson method.A computer program is developed to predict the mechanical responses of tensegrity systems under tensile,compressive and flexural loadings.Numerical results obtained are compared with those reported in the literature to demonstrate the accuracy and efficiency of the proposed program.The flexural behavior of the double layer quadruplex tensegrity grid is sufficiently good for lightweight large-span structural applications.On the other hand,its bending strength capacity is not sensitive to the self-stress level.
Effective nonlinear AC response to composite with spherical particles
Institute of Scientific and Technical Information of China (English)
Chen Xiao-Gang; Liang Fang-Chu; Wei En-Bo
2005-01-01
An effective nonlinear alternative-current (AC) response to granular nonlinear-composite with spherical inclusions embedded in a host medium under the action of an external AC field is investigated by using a perturbation approach.The local potentials of composite at higher harmonics are derived both in a region of local inclusion particles and in a local host region under the action of a sinusoidal field E1 sinωt + E3sin3ωt. An effective nonlinear-response to composite and the relationship between the effective nonlinear-responses at the fundamental frequency and the third harmonics are also studied for the spherical inclusions in a dilute limit.
Nonlinear oscillations in a unijunction transistor (UJT) circuit
Zielinski, John
2005-10-01
Phenomena such as plasma wavesootnotetextT Tsuru, Nonlinear resonance phenomena of elect. plasma oscillations by beam modulation, J. Phys. Soc. Japan, 40, 548, 1976. and oscillations in electric circuits which employ a plasma componentootnotetextM Wendt, I Axnas, S Torven, Amplitude collapse of nonlinear double-layer oscillations, Phys. Rev. E, 57, 4638, 1998. can be described by a differential equation with nonlinear dissipative and restoring force terms. The UJT oscillator circuit developed by Koepke and HartleyootnotetextME Koepke, DM Hartley, Experimental verification of periodic pulling in a nonlinear electronic oscillator, Phys. Rev. A, 44, 6877, 1991 is also described by a similar equation. During the past year efforts have been made to understand the following aspects of this circuit's operation: 1) Determining conditions which lead to oscillation onset and termination (amplitude collapse). 2) Analytic and numerical modeling. 3) Characterizing the capacitances associated with the emitter-base junctions. 4) Exploring the relationship between this circuit and astable multivibrators.
Approximate Series Solutions for Nonlinear Free Vibration of Suspended Cables
Directory of Open Access Journals (Sweden)
Yaobing Zhao
2014-01-01
Full Text Available This paper presents approximate series solutions for nonlinear free vibration of suspended cables via the Lindstedt-Poincare method and homotopy analysis method, respectively. Firstly, taking into account the geometric nonlinearity of the suspended cable as well as the quasi-static assumption, a mathematical model is presented. Secondly, two analytical methods are introduced to obtain the approximate series solutions in the case of nonlinear free vibration. Moreover, small and large sag-to-span ratios and initial conditions are chosen to study the nonlinear dynamic responses by these two analytical methods. The numerical results indicate that frequency amplitude relationships obtained with different analytical approaches exhibit some quantitative and qualitative differences in the cases of motions, mode shapes, and particular sag-to-span ratios. Finally, a detailed comparison of the differences in the displacement fields and cable axial total tensions is made.
A Boussinesq model with alleviated nonlinearity and dispersion
Institute of Scientific and Technical Information of China (English)
ZHANG Dian-xin; TAO Jian-hua
2008-01-01
The classical Boussinesq equation is a weakly nonlinear and weakly dispersive equation, which has been widely applied to simulate wave propagation in off-coast shallow waters. A new form of the Boussinesq model for an uneven bottoms is derived in this paper. In the new model, nonlinearity is reduced without increasing the order of the highest derivative in the differential equations. Dispersion relationship of the model is improved to the order of Pade (2,2) by adjusting a parameter in the model based on the long wave approximation. Analysis of the linear dispersion, linear shoaling and nonlinearity of the present model shows that the performances in terms of nonlinearity, dispersion and shoaling of this model are improved. Numerical results obtained with the present model are in agreement with experimental data.