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A New Algorithm Based on Differential Transform Method for Solving Partial Differential Equation System with Initial and Boundary Conditions 认领
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作者 Chenlu Huang Jiwei Li Fali Lin 《理论数学进展(英文)》 2020年第5期337-349,共13页
In this paper, a new Fourier-differential transform method (FDTM) based on differential transformation method (DTM) is proposed. The method can effectively and quickly solve linear and nonlinear partial differential e... In this paper, a new Fourier-differential transform method (FDTM) based on differential transformation method (DTM) is proposed. The method can effectively and quickly solve linear and nonlinear partial differential equations with initial boundary value (IBVP). According to boundary condition, the initial condition is expanded into a Fourier series. After that, the IBVP is transformed to an iterative relation in K-domain. The series solution or exact solution can be obtained. The rationality and practicability of the algorithm FDTM are verified by comparisons of the results obtained by FDTM and the existing analytical solutions. 展开更多
关键词 DIFFERENTIAL TRANSFORM METHOD INITIAL BOUNDARY Value Problem Fourier-Differential TRANSFORM METHOD FOURIER Series Typical Zero BOUNDARY
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A Method for Rapid Determination of Polymer Dissolution Time 认领
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作者 Juan Zhao Jian Zhang +5 位作者 Wensen Zhao Wenjuan Chen Haiyan Guo Quan Wang Zhao Hua Guang Yang 《材料科学与化学工程(英文)》 2020年第5期1-9,共9页
In view of the limited space of offshore platform and the large amount of polymer injection, the dissolution time method, solution viscosity method, conductivity method, undissolved filtration method and falling ball ... In view of the limited space of offshore platform and the large amount of polymer injection, the dissolution time method, solution viscosity method, conductivity method, undissolved filtration method and falling ball method are used as the rapid detection methods of polymer dissolution. The results show that the error of conductivity method is the largest, and that of dissolution time method is the second, and both methods are time-consuming. Solution viscosity method and insolubles filtration method have small error, but they are time-consuming, especially for offshore platforms, which makes detection inconvenient. The drop ball method is simple in operation and has a small error, so it is a promising method for rapid determination of polymer dissolution time. 展开更多
关键词 RAPID Determination DISSOLUTION Time VISCOSITY METHOD Falling-Ball METHOD
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A Scaled Conjugate Gradient Method Based on New BFGS Secant Equation with Modified Nonmonotone Line Search 认领
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作者 Tsegay Giday Woldu Haibin Zhang Yemane Hailu Fissuh 《美国计算数学期刊(英文)》 2020年第1期1-22,共22页
In this paper, we provide and analyze a new scaled conjugate gradient method and its performance, based on the modified secant equation of the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method and on a new modified nonmo... In this paper, we provide and analyze a new scaled conjugate gradient method and its performance, based on the modified secant equation of the Broyden-Fletcher-Goldfarb-Shanno (BFGS) method and on a new modified nonmonotone line search technique. The method incorporates the modified BFGS secant equation in an effort to include the second order information of the objective function. The new secant equation has both gradient and function value information, and its update formula inherits the positive definiteness of Hessian approximation for general convex function. In order to improve the likelihood of finding a global optimal solution, we introduce a new modified nonmonotone line search technique. It is shown that, for nonsmooth convex problems, the proposed algorithm is globally convergent. Numerical results show that this new scaled conjugate gradient algorithm is promising and efficient for solving not only convex but also some large scale nonsmooth nonconvex problems in the sense of the Dolan-Moré performance profiles. 展开更多
关键词 Conjugate Gradient METHOD BFGS METHOD MODIFIED SECANT EQUATION NONMONOTONE Line Search Nonsmooth Optimization
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Liquefaction Potential Assessment of Guwahati City Using One Dimensional Ground Response Analysis 认领
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作者 Amar Farooq Siddique Binu Sharma 《地球科学和环境保护期刊(英文)》 2020年第5期176-194,共19页
Guwahati city which lies in the North Eastern region of India, falls in the highest seismic risk zonal level i.e. zone V in India. However, there are very few works on seismic hazard analysis of Guwahati soil consider... Guwahati city which lies in the North Eastern region of India, falls in the highest seismic risk zonal level i.e. zone V in India. However, there are very few works on seismic hazard analysis of Guwahati soil considering the local site effects. The effect of large modifications in seismic waves that occur due to variation in soil properties near the surface of the earth is of great importance in geotechnical earthquake engineering. Seismic soil liquefaction, a soil seismic hazard, is evaluated in Guwahati city in terms of factor of safety against liquefaction along the soil profiles using ground response analysis. One dimensional ground response analysis has been conducted using equivalent linear and non linear method using the Deepsoil software. The input motion of 2011 Sikkim earthquake (Mw = 6.9) having bedrock PGA of 0.152 g at 30 m depth is considered. A comparative study has been made of the equivalent linear and non linear analysis in terms of surface PGA (g), maximum strain (%), maximum stress ratio and liquefaction potential using soil profiles of Guwahati city. It has been observed that stiffer soil layer results in similar PGA from both the analysis however non linear analysis generally gives a lesser surface PGA than by equivalent linear analysis. Non linear analysis generally gives a higher strain range and a lower maximum stress ratio as compared to the equivalent linear method. A slightly higher factor of safety is obtained using non linear analysis than using equivalent linear analysis. A soil database of 200 bore holes was used for the study. Spatial distribution of soil liquefaction potential is presented in the form of GIS based maps of factor of safety values. 展开更多
关键词 GROUND Response Analysis EQUIVALENT LINEAR METHOD Non LINEAR METHOD Soil LIQUEFACTION
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Research on Simulation Methods of Electric Field Intensity on Surface of 10 kV Cable Joint 认领
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作者 Ruxin Zhang Jun Xiong +9 位作者 Zheng Wu Lei Liao Mingyan Wu Gang Du Xueyou Huang Wenpei Jin Haiming Li Jian Zhang Wenli Cheng Binxian Lu 《能源与动力工程(英文)》 2020年第4期37-45,共9页
The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field... The electric field intensity (EFI) is important characteristic quantity for evaluating the internal insulation state of cable joints. Based on finite element method, this paper proposes two EFI research methods, field-circuit coupling method and equivalent circuit method. The average EFI of the inner surface of the outer semi-conducting shield can be calculated from the current in the measuring circuit. The relative error between these two methods is about 15%, which roughly proves the consistency of the two methods. Further practical application research enables online monitoring of cable joints. 展开更多
关键词 Cable JOINTS Electric FIELD INTENSITY EQUIVALENT CIRCUIT METHOD Field-Circuit Coupling METHOD Finite Element Simulation Software
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Acoustic Monitoring of Anomaly Stressed Zones, Determination Their Positions, Surfaces, Evaluation of Catastrophic Risk 认领
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作者 Olga Hachay Oleg Khachay 《地质学期刊(英文)》 2020年第5期501-509,共9页
Abstract Problem statement. Self-organization is not a universal property of matter, it exists under certain internal and external conditions and this is not associated with a special class of substances. The study of... Abstract Problem statement. Self-organization is not a universal property of matter, it exists under certain internal and external conditions and this is not associated with a special class of substances. The study of the morphology and dynamics of migration of anomalous zones associated with increased stresses is of particular importance in the development of deep deposits, complicated by dynamic phenomena in the form of rock impacts. Applied method and design: An important tool for this study is geophysical exploration. To describe the geological environment in the form of an array of rocks with its natural and technogenic heterogeneity, one should use its more adequate description, which is a discrete model of the medium in the form of a piecewise heterogeneous block medium with embedded heterogeneities of a lower rank than the block size. This nesting can be traced several times, i.e. changing the scale of the study;we see that heterogeneities of a lower rank now appear in the form of blocks for heterogeneities of the next rank. A simple averaging of the measured geophysical parameters can lead to distorted ideas about the structure of the medium and its evolution. Typical results: We have analyzed the morphology of the structural features of disintegration zones before a strong dynamic phenomenon. The introduction of the proposed integrated passive and active geophysical monitoring into the mining system, aimed at studying the transient processes of the redistribution of stress-strain and phase states, can help prevent catastrophic dynamic manifestations during the development of deep-located deposits. Concluding note (Practical value/implications): Active geophysical monitoring methods should be tuned to a model of a hierarchical heterogeneous environment. Iterative algorithms for 2-D modeling and interpretation for sound diffraction and a linearly polarized transverse elastic wave on the inclusion with a hierarchical elastic structure located in the J-th layer of the N-layer elastic medium are constructed. 展开更多
关键词 High-Stressed ZONES Electromagnetic Induction METHOD Acoustic METHOD Hierarchical INCLUSIONS Layered-Block Medium Algorithms of Modeling And Interpretation Estimation of MASSIF No Stability
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A Connection between Geometrical Spreading and the Adjoint Field in Travel Time Tomography 认领
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作者 William Menke 《应用数学(英文)》 2020年第2期84-96,共13页
The goal of tomography is to reconstruct a spatially-varying image function s(x,m), where x is position and m is a finite-length vector of parameters. Many reconstruction methods minimize the total L2 error E ≡ eTe, ... The goal of tomography is to reconstruct a spatially-varying image function s(x,m), where x is position and m is a finite-length vector of parameters. Many reconstruction methods minimize the total L2 error E ≡ eTe, where individual errors ei quantify misfit between predictions and observations, to quantify goodness of fit. So-called adjoint state methods allow the gradient &#8706;E/&#8706;mi to be computed extremely efficiently from an adjoint field, facilitating image reconstruction by gradient-descent methods. We examine the structure of the differential equation for the adjoint field under the ray approximation and find that it has the same form as the transport equation, whose solution involves the well-known geometrical spreading function R Consequently, as R is routinely tabulated as part of a ray calculation, no extra work is needed to compute the adjoint field, permitting a rapid calculation of the gradient?&#8706;E/&#8706;mi. 展开更多
关键词 ADJOINT State METHOD EIKONAL EQUATION GEOMETRICAL SPREADING Gradient-Descent METHOD Transport EQUATION Travel Time Tomography
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EXPANDABLE PARALLEL FINITE ELEMENT METHODS FOR LINEAR ELLIPTIC PROBLEMS 认领
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作者 杜光芝 《数学物理学报:B辑英文版》 SCIE CSCD 2020年第2期572-588,共17页
In this article,two kinds of expandable parallel finite element methods,based on two-grid discretizations,are given to solve the linear elliptic problems.Compared with the classical local and parallel finite element m... In this article,two kinds of expandable parallel finite element methods,based on two-grid discretizations,are given to solve the linear elliptic problems.Compared with the classical local and parallel finite element methods,there are two attractive features of the methods shown in this article:1)a partition of unity is used to generate a series of local and independent subproblems to guarantee the final approximation globally continuous;2)the computational domain of each local subproblem is contained in a ball with radius of O(H)(H is the coarse mesh parameter),which means methods in this article are more suitable for parallel computing in a large parallel computer system.Some a priori error estimation are obtained and optimal error bounds in both H^1-normal and L^2-normal are derived.Finally,numerical results are reported to test and verify the feasibility and validity of our methods. 展开更多
关键词 Two-grid method expandable method partition of unity parallel algorithm finite element method
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A Comparison Study of Deep Galerkin Method and Deep Ritz Method for Elliptic Problems with Different Boundary Conditions 认领
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作者 Jingrun Chen Rui Du Keke Wu 《数学研究通讯:英文版》 CSCD 2020年第3期354-376,共23页
Recent years have witnessed growing interests in solving partial differential equations by deep neural networks,especially in the high-dimensional case.Unlike classical numerical methods,such as finite difference meth... Recent years have witnessed growing interests in solving partial differential equations by deep neural networks,especially in the high-dimensional case.Unlike classical numerical methods,such as finite difference method and finite element method,the enforcement of boundary conditions in deep neural networks is highly nontrivial.One general strategy is to use the penalty method.In the work,we conduct a comparison study for elliptic problems with four different boundary conditions,i.e.,Dirichlet,Neumann,Robin,and periodic boundary conditions,using two representative methods:deep Galerkin method and deep Ritz method.In the former,the PDE residual is minimized in the least-squares sense while the corresponding variational problem is minimized in the latter.Therefore,it is reasonably expected that deep Galerkin method works better for smooth solutions while deep Ritz method works better for low-regularity solutions.However,by a number of examples,we observe that deep Ritz method can outperform deep Galerkin method with a clear dependence of dimensionality even for smooth solutions and deep Galerkin method can also outperform deep Ritz method for low-regularity solutions.Besides,in some cases,when the boundary condition can be implemented in an exact manner,we find that such a strategy not only provides a better approximate solution but also facilitates the training process. 展开更多
关键词 Partial differential equations boundary conditions deep Galerkin method deep Ritz method penalty method
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Advance of Multiplex PCR in Rapid Detecting Transgenic Soybean Oil 认领
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作者 Yi Liu Siya Yin 《美国植物学期刊(英文)》 2020年第3期382-392,共11页
Transgenic food safety is a high-profile public health issue in worldwide, especially transgenic soybean (Glycine max L.) oil. To rapidly and effectively detect transgenic components of soybean oil, in the present stu... Transgenic food safety is a high-profile public health issue in worldwide, especially transgenic soybean (Glycine max L.) oil. To rapidly and effectively detect transgenic components of soybean oil, in the present study, we isolated DNA from transgenic soybean oil by modified method, and employed the multiplex PCR method to identify targeted genes, including CaMV35S promoter, Nos terminator, NPTII, CP4-EPSPS and endogenous gene Lectin. The research aims to build a method which is accurate, rapid and reliable for detection of genetically modified soybeans oil. The targeted gene including DNA was successfully established by the improved method, and then amplified by PCR. Five genes are simultaneously specifically detected. Commercial soybean, genetically modified soy bean and oil were detected with the Multiplex PCR. The improved method of DNA extraction was rapid and accurate to extract high quality total DNA which was amplified by PCR. The method could eliminate the PCR inhibitor. A way of detecting the genetically modified soybean and Oil was set up in this study. 展开更多
关键词 TRANSGENIC SOYBEAN OIL DNA EXTRACTION Method Multiplex PCR
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Mechanical Properties of Self-Assembled Microtubule Curved Protofilaments 认领
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作者 Ramana Pidaparti Divya Jakkam 《生物医学工程(英文)》 2020年第3期37-44,共8页
The microtubule self-assembly process involves the basic building blocks, alpha and beta tubulins which spontaneously bind to one another through polymerization and under controlled intracellular conditions form proto... The microtubule self-assembly process involves the basic building blocks, alpha and beta tubulins which spontaneously bind to one another through polymerization and under controlled intracellular conditions form protofilaments which in turn assemble into microtubules. The mechanical properties of the self-assembled protofilaments play an important role in formation of the microtubules. In this study, we investigate the mechanical properties of the experimentally self-assembled protofilaments (straight and curved) for under different loadings through 3D finite element analysis. Results of force-deformation and stiffness values obtained from the finite element analysis are presented. The results indicate that the stiffness and maximum stress properties change with varying protofilamant curvature. These force-deformation behaviors and stress distributions should help further understand the contribution of protofilaments mechanical properties in forming self-assembled microtubules. 展开更多
关键词 MICROTUBULE Protofilament TUBULIN FINITE ELEMENT Method MECHANICAL Properties
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Calculation of disconnected quark loops in lattice QCD 认领
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作者 程贞 张剑波 熊光仪 《中国物理C:英文版》 SCIE CAS CSCD 2020年第3期52-58,共7页
Calculation of disconnected quark loops in lattice QCD is very time consuming.Stochastic noise methods are generally used to estimate these loops.However,stochastic estimation gives large errors in the calculations of... Calculation of disconnected quark loops in lattice QCD is very time consuming.Stochastic noise methods are generally used to estimate these loops.However,stochastic estimation gives large errors in the calculations of disconnected diagrams.We use the symmetric multi-probing source(SMP)method to estimate the disconnected quark loops,and compare the results with the Z(2)noise method and the spin-color explicit(SCE)method on a quenched lattice QCD ensemble with lattice volume 12^3×24 and lattice spacing a≈0.1 fm.The results show that the SMP method is very suitable for the calculation of pseudoscalar disconnected quark loops.However,the SMP and SCE methods do not have an obvious advantage over the Z(2)noise method in the evaluation of the scalar disconnected loops. 展开更多
关键词 lattice QCD Wilson matrix disconnected QUARK LOOPS Z(2)noise METHOD SMP METHOD
Chebyshev spectral variational integrator and applications 认领
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作者 Zhonggui YI Baozeng YUE Mingle DENG 《应用数学和力学:英文版》 SCIE EI CSCD 2020年第5期753-768,共16页
The Chebyshev spectral variational integrator(CSVI) is presented in this paper. Spectral methods have aroused great interest in approximating numerically a smooth problem for their attractive geometric convergence rat... The Chebyshev spectral variational integrator(CSVI) is presented in this paper. Spectral methods have aroused great interest in approximating numerically a smooth problem for their attractive geometric convergence rates. The geometric numerical methods are praised for their excellent long-time geometric structure-preserving properties.According to the generalized Galerkin framework, we combine two methods together to construct a variational integrator, which captures the merits of both methods. Since the interpolating points of the variational integrator are chosen as the Chebyshev points,the integration of Lagrangian can be approximated by the Clenshaw-Curtis quadrature rule, and the barycentric Lagrange interpolation is presented to substitute for the classic Lagrange interpolation in the approximation of configuration variables and the corresponding derivatives. The numerical float errors of the first-order spectral differentiation matrix can be alleviated by using a trigonometric identity especially when the number of Chebyshev points is large. Furthermore, the spectral variational integrator(SVI) constructed by the Gauss-Legendre quadrature rule and the multi-interval spectral method are carried out to compare with the CSVI, and the interesting kink phenomena for the Clenshaw-Curtis quadrature rule are discovered. The numerical results reveal that the CSVI has an advantage on the computing time over the whole progress and a higher accuracy than the SVI before the kink position. The effectiveness of the proposed method is demonstrated and verified perfectly through the numerical simulations for several classical mechanics examples and the orbital propagation for the planet systems and the Solar system. 展开更多
关键词 geometric numerical method spectral method variational integrator Clenshaw-Curtis quadrature rule barycentric Lagrange interpolation orbital propagation
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Multi-Level, Multi-Scale Modeling and Predictive Mapping for Jaguars in the Brazilian Pantanal 认领
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作者 Eve Bohnett Dave Hulse +1 位作者 Bilal Ahmad Thomas Hoctor 《生态学期刊(英文)》 2020年第5期243-263,共21页
Multi-level multi-scale resource selection models using machine learning were compared and contrasted for generating predictive maps of jaguar habitat (Panthera onca) in the Brazilian Pantanal. Multiple spatial scales... Multi-level multi-scale resource selection models using machine learning were compared and contrasted for generating predictive maps of jaguar habitat (Panthera onca) in the Brazilian Pantanal. Multiple spatial scales and temporal movement levels were run within several analytical modeling frameworks for comparison. Included in the analysis were multi-scale raster grains (30 m, 90 m, 180 m, 360 m, 720 m, 1440 m) and GPS collaring temporal movement levels (point, path, and step). Various analytical methods were used for comparison of models that could accommodate data structural levels (group, individual, case-control). Models compared included conditional logistic regression, generalized additive modeling (GAM), and classification regression trees, such as random forests (RF) and gradient boosted regression tree (GBM). The goals of the study were to discuss the potential and limitations for machine learning methods using GPS collaring data to produce predictive habitat suitability mapping using the various scales and levels available. Results indicated that choosing the appropriate temporal level and raster scale improved model outputs. Overall, larger level analytical modeling frameworks and those that used multi-scale raster grains showed the best model evaluation with the inherent condition that they predict a broader scale and subset of data. The identification of the appropriate spatial scale, temporal scale and statistical model need careful consideration in predictive mapping efforts. 展开更多
关键词 Machine Learning Movement Ecology HABITAT SELECTION Resource SELECTION MULTIPLE Levels MULTIPLE Scales PREDICTIVE Models Gradient Boosting Method Random Forest
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Nurses’ Experiences of Process-Oriented Supervision—Acquiring New Approaches to Demanding Situations 认领
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作者 Lotta Carlson Linda Berg Margaretha Jenholt Nolbris 《护理学期刊(英文)》 2020年第4期449-461,共13页
Background: Providing nursing care for patients and relatives requires a great effort from a nurse. It is therefore important for the nurse to have the opportunity to reflect on the caring acts included in process-ori... Background: Providing nursing care for patients and relatives requires a great effort from a nurse. It is therefore important for the nurse to have the opportunity to reflect on the caring acts included in process-oriented nursing supervision (PRONS). The overall objective of the nursing supervision is to support the professional development identity, competences, skills and ethics in different situations in nursing care. Aim: To investigate nurses’ experiences of the model of purging, playing and learning (PPL) according to Eriksson theory in a (PRONS) related to strengthen safe care, quality and professional development. Method: A qualitative study with individual interviews and the data was analyzed using qualitative interpretive content analysis. Participants: All eleven registered participated nurses were from southwestern Sweden and worked in different hospital units. Ethical Considerations: The study carried out in accordance with the ethical guidelines laid down in the Helsinki Declaration and according to the recommendations of the regional ethics committee. Findings: Three categories were identified, valuable purging in the process, responsive playing and awareness of learning. The study found that by participating in PRONS the nurses had developed new approaches with different “tools” when difficult situations occurred in daily nursing practice. Conclusion: PRONS with the model PPL has an important role to support nurses in daily nursing practice. The study highlights that there are residual successful effects after PRONS for the nurses in managing care situations that experienced strengthen quality in care and professional development. 展开更多
关键词 NURSING Process-Oriented SUPERVISION REFLECTION Qualitative DESCRIPTIVE METHOD
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基于S-method时频分析的制动意图识别方法 认领
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作者 孙嘉兵 李志光 谢志鹏 《汽车实用技术》 2020年第10期166-169,共4页
为了提高电动汽车制动能量回收效率,不可避免需要增加制动意图判断的准确率,提出了基于S-method时频分析的制动意图识别方法。鉴于S-method处理非平稳信号兼顾算法响应时间和时频分辨率的优点,通过建立S-method时频模型的基础上,运用奇... 为了提高电动汽车制动能量回收效率,不可避免需要增加制动意图判断的准确率,提出了基于S-method时频分析的制动意图识别方法。鉴于S-method处理非平稳信号兼顾算法响应时间和时频分辨率的优点,通过建立S-method时频模型的基础上,运用奇异值分解方法提取特征值。最后,运用聚类算法识别驾驶员制动意图。实验结果表明,该方法能实时有效识别中等制动和平缓制动。 展开更多
关键词 电动汽车 S-method 奇异值分解 聚类识别
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Vibration-Based Analysis for Detecting Turbocharger Blade Defect on High-Power Diesel Generator 认领
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作者 Metaga Jeremi Sogoba Badié Diourté Moussa Magara Traoré 《力学国际期刊(英文)》 2020年第1期1-10,共10页
This study is concerned with 12-MW capacity turbochargers on diesel power generators. These are generators equipped with 18 cylinders. Our previous studies [1] showed that the processing of vibration signature collect... This study is concerned with 12-MW capacity turbochargers on diesel power generators. These are generators equipped with 18 cylinders. Our previous studies [1] showed that the processing of vibration signature collected from a power generator is very complex, insomuch the dominant vibration remains the one originating from explosion frequency in the diesel generator cylinders, with a fairly high number of cylinders. This vibration drowns out all other possible vibrations, which can expose defects. The study at hand is focused on turbochargers with 20,940 rpm, while the rotation speed in the diesel engine is 600 rpm only. With the turbocharger rotating at very high speed, it results in severe mechanical constraints on the rotor shaft in the turbocharger and its related organs (turbine blades). The wear of turbine blades can result in breakdowns in the turbocharger. This article is an attempt to early detect defaults in turbine blades based on vibration signature that can be experimentally determined. We noted in our investigations that a diesel engine and its turbochargers do not bear the same mechanic loads. While the diesel engine is the seat of violent shocks brought about by explosions in cylinders, the turbochargers are driven by the action of exhaust gas from explosions, without being affected by explosion shocks. The study found that explosion frequency in the diesel engine cylinders, which disrupted the vibration signals in the diesel engine and alternator, did not impact on the vibration signals in the turbocharger. We experimentally determined, following several campaigns of measurements, a vibration signature on the turbochargers under study, which corresponds to a defect in turbine blades. 展开更多
关键词 VIBRATION Signature Fast Fourier Transform Method (FFT) TURBOCHARGER Tur-bine BLADES
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Numerical Simulation of Elastic Stress Wave Refraction at Air-Solid Interfaces 认领
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作者 Ruchao Shi Xiaowang Sun 《北京理工大学学报:英文版》 EI CAS 2020年第2期209-221,共13页
Elastic wave refraction at the air-solid interface and wave propagations in the vicinity of the air-solid interface are numerically studied.The modified ghost fluid method(MGFM)and isobaric fix methods are combined to... Elastic wave refraction at the air-solid interface and wave propagations in the vicinity of the air-solid interface are numerically studied.The modified ghost fluid method(MGFM)and isobaric fix methods are combined to solve the fluid and solid statuses at the air-solid interface and construct a continuous boundary condition for the air-solid interface.The states in the ghost domain are evaluated by the MGFM-algorithm.The solid governing equations are solved with second order spatial discretization.Numerical tests verify the correctness of the presented continuous boundary condition and show that the combined method is convergent in the vicinity of the air-solid interface.The 3D numerical results by the combined method are close to those of the ArbitraryLagrangian-Eulerian(ALE)method.The combined method is robust when applied for multi-dimensional problems.A compression stress wave impacting on the air-solid interface result in a compression wave in air.A tension stress wave impacting on the air-solid interface result in an expansion wave in air. 展开更多
关键词 fluid-structure interaction finite difference method level set method continuity condition stress wave propagation
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Size Effect on Onset and Subsequent Evolution of Adiabatic Shear Band:Theoretical and Numerical Analysis 认领
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作者 Jiejian Liu Tao Suo +1 位作者 Fenghua Zhou Yulong Li 《固体力学学报:英文版》 SCIE EI CSCD 2020年第3期294-306,共13页
The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the firs... The adiabatic shear instability of ductile materials has attracted more and more attentions of researchers and groups,who have been sparing no effort in further understanding of the underlying mechanism since the first experimental depiction of adiabatic shear instability by Zener and Hollomon.As for the adiabatic shear instability,many factors account for its occurrence,including heat conduction,inertia effect,microstructure effect and so on.However,lots of experimental evidence has shown that metal materials display a strong size effect when the characteristic length scale is in the order of microns.The size effect has also been observed in the analysis of shear band in the ductile materials because the order of the bandwidth stays within the microscale range.However,a comprehensive understanding of the whole process of adiabatic shear banding(ASB),including the early onset and the subsequent evolution,is still lacking.In this work,a gradient plasticity model based on the Taylor-based nonlocal theory feasible for the linear perturbation analysis and convenient for numerical calculation is proposed to investigate the strain gradient on the onset of ASB and the coupling effect of heat conduction,inertia effect and strain gradient at the early stage,as well as on the subsequent evolution process at later stages.As for the onset of ASB,the linear perturbation method is used to consider the effect on the initial formation of ASB.After the investigation of the onset of ASB.the characteristic line method is applied to describe the subsequent nonlinear evolution process of ASB.Three stages of ASB evolution are clearly depicted during the evolution process,and the significance of size effect on the ASB nonlinear evolution process of ASB at different stages is analyzed.With the help of linear perturbation analysis and characteristic line method,a comprehensive description of the role of strain gradient in the ASB from the early onset to the end of the evolution is provided. 展开更多
关键词 Adiabatic shear band Strain gradient Nonlinear evolution process Linear perturbation method Characteristic line method
A constructive method for approximating trigonometric functions and their integrals 认领
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作者 CHEN Xiao-diao WANG Long-quan WANG Yi-gang 《高校应用数学学报:英文版(B辑)》 SCIE CSCD 2020年第3期293-307,共15页
This paper presents an interpolation-based method(IBM)for approximating some trigonometric functions or their integrals as well.It provides two-sided bounds for each function,which also achieves much better approximat... This paper presents an interpolation-based method(IBM)for approximating some trigonometric functions or their integrals as well.It provides two-sided bounds for each function,which also achieves much better approximation effects than those of prevailing methods.In principle,the IBM can be applied for bounding more bounded smooth functions and their integrals as well,and its applications include approximating the integral of sin(x)/x function and improving the famous square root inequalities. 展开更多
关键词 Padéapproximant trigonometric function constructive method interpolation-based method two-sided bounds
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