CHARACTERISTICS OF SUBDIFFERENTIALS OF FUNCTIONS

ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＳＵＢＤＩＦＦＥＲＥＮＴＩＡＬＳＯＦＦＵＮＣＴＩＯＮＳ（郭兴明）ＣＨＡＲＡＣＴＥＲＩＳＴＩＣＳＯＦＳＵＢＤＩＦＦＥＲＥＮＴＩＡＬＳＯＦＦＵＮＣＴＩＯＮＳ￥ＧｕｏＸｉｎｇｍｉｎｇ（ＲｅｃｅｉｖｅｄＪｕｎｅ１６，１９９５...     

FORCED OSCILLATIONS OF BOUNDARY VALUE PROBLEMS OF HIGHER ORDER FUNCTIONAL PARTIAL DIFFERENTIAL EQUATIONS

ＦＯＲＣＥＤＯＳＣＩＬＬＡＴＩＯＮＳＯＦＢＯＵＮＤＡＲＹＶＡＬＵＥＰＲＯＢＬＥＭＳＯＦＨＩＧＨＥＲＯＲＤＥＲＦＵＮＣＴＩＯＮＡＬＰＡＲＴＩＡＬＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＪｉｎＭｉｎｇＺｈｏｎｇ（靳明忠），ＤｏｎｇＹｉｎｇ（董莹），Ｌｉ...     

FIRST INTEGRALS AND INTEGRAL INVARIANTS FOR VARIABLE MASS NONHOLONOMIC SYSTEM IN NONINERTIAL REFERENCE FRAMES

ＦＩＲＳＴＩＮＴＥＧＲＡＬＳＡＮＤＩＮＴＥＧＲＡＬＩＮＶＡＲＩＡＮＴＳＦＯＲＶＡＲＩＡＢＬＥＭＡＳＳＮＯＮＨＯＬＯＮＯＭＩＣＳＹＳＴＥＭＩＮＮＯＮＩＮＥＲＴＩＡＬＲＥＦＥＲＥＮＣＥＦＲＡＭＥＳＬｕｏＳｈａｏ－ｋａｉ（罗绍凯）（Ｓｈａｎｇｑｉｕ，Ｎｏｒ...     

SOLUTIONS FOR A SYSTEM OF NONLINEAR RANDOM INTEGRAL AND DIFFERENTIAL EQUATIONS

ＳＯＬＵＴＩＯＮＳＦＯＲＡＳＹＳＴＥＭＯＦＮＯＮＬＩＮＥＡＲＲＡＮＤＯＭＩＮＴＥＧＲＡＬＡＮＤＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳ￥ＤｉｎｇＸｉｅｐｉｎｇ（丁协平）ＷａｎｇＦａｎ（王凡）（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，Ｓｉｃｈ...     

A MODIFIED METHOD OF AVERAGING FOR SOLVING A CLASS OFNONLINEAR EQUATIONS

ＡＭＯＤＩＦＩＥＤＭＥＴＨＯＤＯＦＡＶＥＲＡＧＩＮＧＦＯＲＳＯＬＶＩＮＧＡＣＬＡＳＳＯＦＮＯＮＬＩＮＥＡＲＥＱＵＡＴＩＯＮＳＺｈａｎｇＢａｏ－ｓｈａｎ（张宝善）（ＤｅｐａｒｉｍｅｎｔｏｆＭａｉｈ．，ＸｕｚｈｏｕＴｅａｃｈｅｒｓＣｏｌｌｅｇｅ，Ｘｕｚｈ...     

ANISOTROPIC EFFECTS OF QUASI－ISOTROPIC COMPOSITES（II）──APPLICATIONS AND MICRO－MECHANICAL ANALYSIS

ＡＮＩＳＯＴＲＯＰＩＣＥＦＦＥＣＴＳＯＦＱＵＡＳＩ－ＩＳＯＴＲＯＰＩＣＣＯＭＰＯＳＩＴＥＳ（ＩＩ）－－ＡＰＰＬＩＣＡＴＩＯＮＳＡＮＤＭＩＣＲＯ－ＭＥＣＨＡＮＩＣＡＬＡＮＡＬＹＳＩＳＦａｎｇＨｕｉｙｕ（方辉宇），ＺｈｅｎｇＱｕａｎｇｓｈｕｉ（郑泉水）（...     

An Analysis of the Post-buckling of Laminated Plates of Symmetric Cross-Ply

ＡＮＡＮＡＬＹＳＩＳＯＦＴＨＥＰＯＳＴ－ＢＵＣＫＬＩＮＧＯＦＬＡＭＩＮＡＴＥＤＰＬＡＴＥＳＯＦＳＹＭＭＥＴＲＩＣＣＲＯＳＳ－ＰＬＹＷｅｎｇＺｏｎｇｙｉ（翁宗诒）（ＲｅｃｅｉｖｅｄＭａｒｃｈ６，１９９５，ＣｏｍｍｕｎｉｃａｔｅｄｂｙＺｈｏｕＣｈｅｎｇｔ...     

EXISTENCE THEOREMS OF EXTREMAL SOLUTIONS FOR A CLASS OF NONLINEAR INTEGRO－DIFFERENTIAL EQUATIONS

ＥＸＩＳＴＥＮＣＥＴＨＥＯＲＥＭＳＯＦＥＸＴＲＥＭＡＬＳＯＬＵＴＩＯＮＳＦＯＲＡＣＬＡＳＳＯＦＮＯＮＬＩＮＥＡＲＩＮＴＥＧＲＯ－ＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＳｏｎｇＧｕａｎｇｘｉｎｇ（宋光兴）（ＲｅｃｅｉｖｅｄＭａｙ４，１９９５；Ｃｏｍ...     

RESEARCH OF THE PERIODIC SOLUTION FOR A CLASS OF NONLINEAR DIFFERENTIAL EQUATIONS

ＲＥＳＥＡＲＣＨＯＦＴＨＥＰＥＲＩＯＤＩＣＳＯＬＵＴＩＯＮＦＯＲＡＣＬＡＳＳＯＦ　ＮＯＮＬＩＮＥＡＲＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＲＥＳＥＡＲＣＨＯＦＴＨＥＰＥＲＩＯＤＩＣＳＯＬＵＴＩＯＮＦＯＲＡＣＬＡＳＳＯＦＮＯＮＬＩＮＥＡＲＤＩＦＦＥ...     

ANALYSIS OF STABILITY ON ELASTIC PLATES WITH INITIAL IMPERFECTIONS

ＡＮＡＬＹＳＩＳＯＦＳＴＡＢＩＬＩＴＹＯＮＥＬＡＳＴＩＣＰＬＡＴＥＳＷＩＴＨＩＮＩＴＩＡＬＩＭＰＥＲＦＥＣＴＩＯＮＳＸｕＫａｉｙｕ（徐凯宇）（ＲｅｃｅｉｔｅｄＯｃｔ．５，１９９４．ＣｏｍｍｕｎｉｃａｔｅｄＰａｉＬｉｚｈｏｕ）ＡＮＡＬＹＳＩＳＯＦＳＴＡ...     

Explicit and implicit viscoplastic models for polymeric composite

The viscoplastic behavior of a carbon-fiber/polymer matrix composite was investigated through two different modeling efforts. The first model is phenomenological in nature and utilizes the tensile and stress relaxation experiments to predict the creep strain. The phenomenological model was constructed based on the overstress viscoplastic model. In the second model, the composite viscoplastic behavior is captured via neural networks formulation. The neural networks model was constructed directly from the experimental results obtained via creep tests performed at various stress–temperature conditions. The neural network was trained to predict the creep strain based on the stress–temperature–time values. The performance of the neural model is evaluated through the mean squared error between the neural network prediction and the experimental creep strain results. To minimize this error, several optimization techniques were examined. The minimization of the error when carried out by the Truncated Newton method outperforms the standard back-propagation and the conjugate gradient method in terms of convergence rate and accuracy. Using neural network with truncated Newton training algorithm, the prediction of the creep strain was very satisfactory compared to the phenomenological model.     

基于直接数值模拟的可压缩湍流模型评估和改进

对来流Mach数2.25和6的平板边界层湍流进行了直接数值模拟, 并通过与理论、实验及他人计算结果的对比对数值结果进行了验证. 基于直接数值模拟得到的湍流数据库, 对常用的湍流模型进行了先验评估. 评估的湍流模型有k-εvarepsilon模型(包括标准k-εvarepsilon 模型、可实现的k-εvarepsilon模型及低Reynolds数k-εvarepsilon模型)、SA模型及BL模型. 结果显示, 对于Mach2.25的平板边界层, 可实现的k-εvarepsilon 模型及低Reynolds 数k-εvarepsilon模型具有较好的预测能力, 而标准k-εvarepsilon模型预测的湍流黏性系数偏高; SA模型在边界层内层预测准确度较高, 而在外层预测值偏高. 而对于Mach6的平板边界层, k-εvarepsilon模型及SA模型预测的湍流黏性系数均偏高, 尤其是标准k-εvarepsilon模型. 对于Mach6的平板边界层, BL模型低估了内-外层交界位置, 造成湍流黏性系数预测值严重偏低. 作者通过修改模型系数及内-外层交界位置对BL模型进行了修改, 修改后模型预测的湍流黏性系数与DNS给出的值吻合较好.     

DH36钢拉伸塑性流动特性及本构关系

对DH36钢在温度从293~800 K、应变率为0.001和0.1 s-1的拉伸塑性流动特性进行实验研究，通过端口形貌图对变形前后的试样进行了微观分析，结果表明:(1)在实验温度范围内，0.001和0.1 s-1的应变率下，第三型应变时效现象出现，随应变率的增加，时效发生的温度区域移向更高温度；(2)第三型应变时效的发生与合金原子在晶界和晶粒中大量的第二相析出强化有关联；(3)建立包含第三型应变时效现象的统一本构模型，通过比较该模型能够较好的预测DH36的塑性拉伸流动应力。     

The dynamic coupling of left ventricle and systemic arteries

ＩｎｔｒｏｄｕｃｔｉｏｎＣａｒｄｉｏｖａｓｃｕｌａｒｓｙｓｔｅｍｉｓａｎｅｘｔｒｅｍｅｌｙｃｏｍｐｌｅｘｃｏｕｐｌｉｎｇｓｙｓｔｅｍｉｎｗｈｉｃｈｌｅｆｔｖｅｎｔｒｉｃｌｅ（ＬＶ）ａｎｄｓｙｓｔｅｍｉｃａｒｔｅｒｉｅｓ（ＳＡ）ｉｎｔｅｒａｃｔｗｉｔｈ...     

Improved global–local simulated annealing formulation for solving non-smooth engineering optimization problems

This paper is concerned with a novel optimization algorithm that implements an enhanced formulation of simulated annealing (SA). The new algorithm is denoted as ISA (improved simulated annealing) in the rest of the paper. ISA includes a two-level random search: “global annealing” where all design variables are perturbed simultaneously and “local annealing” where design variables are perturbed one at a time.The improvement with respect to classical SA is in the fact that trial designs are generated always taking care to choose directions along which the cost function may improve. To this purpose, cost function sensitivities are computed in order to properly choose the size of each random perturbation. In addition, the optimization problem is linearized about the current design point if the optimizer ends up in an infeasible region or there is no significant reduction in cost even though the cost function gradient is not close to zero. The linearization is controlled by a trust region model. The optimization algorithm continuously shifts from global to local annealing based on the current best record at the beginning of each cooling cycle. Finally, the cooling schedule is automatically adjusted within ISA based on the convergence behavior.In this work, the ISA algorithm is successfully utilized to solve complicated optimization problems which exhibit non-smooth/non-convex behavior: (i) the large-scale (200 design variables and 3500 constraints) weight minimization of a 200 bar truss under five independent loading conditions; (ii) the configuration optimization of a cantilevered bar truss with 45 elements and 81 design variables; (iii) an example of reverse engineering where in-plane elastic properties of an eight-ply woven composite laminate are to be determined.The performance of ISA is compared to that of classical SA, gradient based optimization codes recently published in literature and commercial software. The results obtained in this study indicate that ISA is a very efficient optimization code. In fact, ISA was much faster than classical SA. The present code allowed about 300 kg weight saving in the 200 bar truss case and about 80 kg in the cantilevered bar truss case. In addition, the residual error on elastic constants in the material identification problem was less than 3%.     

Identification of elastic property and loading fields from full-field displacement measurements

A method is introduced to identify simultaneously elastic properties and loading fields from a measured displacement field. Since the mechanical behavior of micro-electro-mechanical systems (MEMS) is governed by surface effects, this type of identification tool is thought to be of major interest. However, increasing the number of parameters to retrieve affects the redundancy necessary for an accurate identification. A finite-element formulation of a distance between measured and statically admissible (SA) displacement fields is shown to be equivalent to a standard least-squares distance to kinematically admissible (KA) fields if the used modeling is suitable. Any deviation from this equivalence is then the signature of a modeling error. Balancing the distance to KA and SA displacement fields allows one to retrieve unknown modeling parameters. This method is detailed on heterogeneous Euler–Bernoulli beams submitted to an unknown loading field and applied to experimental displacement fields of micro-cantilevers obtained with an electrostatic set-up. An elastic property field and a parameterized loading field are then identified, and the quality of the identification is assessed.     

两种湍流模型在高速旋转翼身组合弹箭中的对比研究1）

弹箭设计、弹道计算和稳定性研究都需要准确预测旋转弹箭的马格努斯力和力矩，国内针对旋转弹箭气动特性的数值模拟工作集中在旋成体上，对带翼外形进行完全时间相关的非定常研究鲜有见到；国外虽然有对带翼外形开展研究，但以验证方法为主，对湍流模型在复杂外形弹箭旋转中的研究未曾见到.采用完全时间相关的非定常N-S方程，对带翼弹箭开展计算，对比了一方程SA（Spalart-Allmaras）湍流模型和两方程k-!SST（shear-stress-transport）湍流模型对马格努斯效应产生的影响，并分析了旋转导致的边界层和涡非对称畸变，以及周向压力分布和剪切应力分布非对称畸变.结果表明：旋转引起的物面流场参数变化主要体现在弹体中后部，SA和SST湍流模型预测的全弹马格努斯特性与阿诺德工程发展中心（Arnold Engineering Development Center，AEDC）实验及陆军研究实验室（Army Research Laboratory，ARL）的计算结果一致性很好，对动导数而言两湍流模型计算精度相当.两湍流模型计算的弹体左侧流场参数差异比右侧大，分析认为正向旋转使左侧壁面速度方向与来流速度相反，相互阻碍使气流脉动效应更强.壁面附近湍流黏性系数SA结果大于SST结果，y=0截面物面压力SA结果小于SST结果、最大相差6%，摩阻系数SA结果大于SST结果、最大相差35%.SA对旋转产生的分离抑制作用强于SST.     

A Spalart–allmaras Turbulence Model Implementation for High-order Discontinuous Galerkin Solution of the Reynolds-averaged Navier-stokes Equations

A novel and robust approach has been proposed for the high-order discontinuous Galerkin (DG) discretization of the Reynolds-averaged Navier-Stokes (RANS) equations with the turbulence model of Spalart-Allmaras (SA). The solution polynomials of the SA equation are reconstructed by the Hermite weighted essentially non-oscillatory (HWENO) scheme. Several practical techniques are suggested to simplify and extend a positivity-preserving limiter to further guarantee the positivity of SA working variable. The resulting positivity-preserving HWENO limiting method is compact and easy to implement on arbitrary meshes. Typical turbulent flows are conducted to assess the accuracy and robustness of the present method. Numerical experiments demonstrate that with the increasing grid or order resolution, the limited results of the working variable are getting closer to the unlimited ones. And the most obvious improvement with proposed method is on the computation of the working variable field in wake regions.     

桥梁节段模型气弹振动的非线性判别方法研究

在ERA(Eigensystem Realization Algorithm)的理论框架内建立了误差因子,评估桥梁节段模型风洞实验中气动导数的辨识质量。通过子空间能量分解,分别计算辨识过程中有效识别信号成分能量和未被识别信号成分能量与总信号能量的比值,并以此构造误差因子。将相同实验环境下自由衰减振动和尾流激励随机振动两组实验的误差因子相互比对,判断桥梁节段模型的气弹振动非线性是否对气动导数辨识结果产生影响。依据误差因子判断,在本文所使用的两种节段模型中,部分流线型箱梁断面具有较强的耦合非线性;而槽形开口型断面的模型具有较低的耦合非线性。     

Meshing Requirements for Tidal Modeling in the Western North Atlantic

This paper presents an a posteriori approach to unstructured mesh generation via a localized truncation error analysis and applies it to the Western North Atlantic Tidal (WNAT) model domain. The WNAT model domain encompasses the Gulf of Mexico, the Caribbean Sea, and the North Atlantic Ocean east to the 60°W Meridian. Herein, we pay particular attention to the area surrounding the Bahamas.

A bathymetric data set with fine resolution is employed in seven separate linear, harmonic simulations of shallow water tidal flow for seven different tidal-forcing constituents. Each set of simulation results is used to perform a truncation error analysis of a linear, harmonic form of the depth-averaged momentum equations for each of the seven different tidal-forcing frequencies. Truncation error is then driven to a more uniform, domain-wide value by solving for local node spacing requirements. The process is built upon successful research aiming to produce unstructured grids for large-scale domains that can be used in the accurate and efficient modeling of shallow water flow. The methodology described herein can also be transferred to other modeling applications.