全启发式教学法在“金属切削机床与刀具”课程中的应用

针对当代大学生的特点,阐述了来自于建构主义的全启发式教学方法的理论,对“金属切削机床与刀具”课程内容进行问题分解,采用以启发诱导、共同协作为核心的全启发式教学方法,对该课程的教学环节进行了合理的设计。     

An automatic parameter calibration method for the SWAT model in runoff simulation

Runoff simulation is highly significant for hydrological monitoring, flood peak simulation, water resource management, and basin protection. Runoff simulation by distributed hydrological models, such as the soil and water assessment tool (SWAT) model which is the most widely used, is becoming a hotspot for hydrological forecasting research. However, parameter calibration is inefficient and inaccurate for the SWAT model. An automatic parameter calibration (APC) method of the SWAT model was developed by hybrid of the genetic algorithm (GA) and particle swarm optimization (PSO). Multi‐station and multi‐period runoff simulation and accuracy analysis were conducted in the basin of the Zhangjiang River on the basis of this hybrid algorithm. For example, in the Yaoxiaba Station, the calibration results produced an R² of 0.87 and Nash Sutcliffe efficiency (NSE) index of 0.85, while verification results revealed an R² of 0.83 and NSE of 0.83. Results of this study show that the proposed method can effectively improve the efficiency and simulation accuracy of the model parameters. It can be concluded that the feasibility and applicability of GA‐PSO as an APC method for the SWAT model were confirmed via case studies. The proposed method can provide theoretical guidance for many hydrological research fields, such as hydrological simulation, flood prevention, and forecasting.     

Finite difference method for dynamic response analysis of anchorage system简

Based on some assumptions, the dynamic analysis model of anchorage system is established. The dynamic governing equation is expressed as finite difference format and programmed by using MATLAB language. Compared with theoretical method, the finite difference method has been verified to be feasible by a case study. It is found that under seismic loading, the dynamic response of anchorage system is synchronously fluctuated with the seismic vibration. The change of displacement amplitude of material points is slight, and comparatively speaking, the displacement amplitude of the outside point is a little larger than that of the inside point, which shows amplification effect of surface. While the axial force amplitude transforms considerably from the inside to the outside. It increases first and reaches the peak value in the intersection between the anchoring section and free section, then decreases slowly in the free section. When considering damping effect of anchorage system, the finite difference method can reflect the time attenuation characteristic better, and the calculating result would be safer and more reasonable than the dynamic steady-state theoretical method. What is more, the finite difference method can be applied to the dynamic response analysis of harmonic and seismic random vibration for all kinds of anchor, and hence has a broad application prospect.     

符号几何规划问题的求解新方法

对符号几何规划问题,给出一种求其全局最优解的分支定界算法。利用不同的凸化方法将算法中关键的定下界操作转化为易于求解的凸规划问题。最后给出算法的收敛性证明和数值实验结果。     

Sensitivity analysis based preform die shape design using the finite element method

This paper uses a finite element-based sensitivity analysis method to design the preform die shape for metal forming processes. The sensitivity analysis was developed using the rigid visco-plastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of the B-spline are used as the design variables. The optimization problem is to minimize the difference between the realized and the desired final forging shapes. The sensitivity analysis includes the sensitivities of the objective function, nodal coordinates, and nodal velocities with respect to the design variables. The remeshing procedure and the interpolation/transfer of the history/dependent parameters are considered. An adjustment of the volume loss resulting from the finite element analysis is used to make the workpiece volume consistent in each optimization iteration and improve the optimization convergence. In addition, a technique for dealing with fold-over defects during the forming simulation is employed in order to continue the optimization procedures of the preform die shape design. The method developed in this paper is used to design the preform die shape for both plane strain and axisymmetric deformations with shaped cavities. The analysis shows that satisfactory final forging shapes are obtained using the optimized preform die shapes.     

高炉铜冷却壁凝固过程数值模拟

在对铜冷却壁砂型 金属型复合铸造条件下的热态工况进行分析的基础上,利用有限元数值模拟的方法首次建立了铸型传热分析对称模型。在模型中对铸型传热系统中的对流、辐射、接触边界条件和凝固潜热进行了处理,利用有限元分析软件ANSYS,分析了紫铜冷却壁的温度场的变化。数值模拟的结果与实际生产相当吻合。     

DEPENDENCE OF PREDICTION MODEL OF FORMING LIMIT STRAINS ON FORMING METHOD AND MECHANICAL PROPERTIES OF SHEET METALS

ＤＥＰＥＮＤＥＮＣＥＯＦＰＲＥＤＩＣＴＩＯＮＭＯＤＥＬＯＦＦＯＲＭＩＮＧＬＩＭＩＴＳＴＲＡＩＮＳＯＮＦＯＲＭＩＮＧＭＥＴＨＯＤＡＮＤＭＥＣＨＡＮＩＣＡＬＰＲＯＰＥＲＴＩＥＳＯＦＳＨＥＥＴＭＥＴＡＬＳ①ＺｈｏｕＷｅｉｘｉａｎＤｅｐａｒｔｍｅｎｔｏｆＡｅ...     

射线检测中运动模糊图像的恢复

X射线实时成像检测中,若曝光时间内工件和X射线图像采集设备有相对线性运动,会造成图像运动模糊降质。提出利用运动模糊点扩展函数的频域特征和Hough变换得到模糊图像的运动方向,并将之旋转到水平轴方向,利用差分法求解运动模糊点扩展函数的长度。并用Wiener滤波的方法,恢复降质的图像,取得了较好的效果。     

IDEF0法建立模具CAD／CAM系统的功能模型

本文阐述了 IDEFO 法建立系统功能模型的步骤、方法和意义,IDEFO 法是一种结构化的系统分析方法,最后用一个简单实例加以说明。     

系统失效的分支-界限分析法及其在桁架可靠性分析中的应用

本文首先介绍了系统失效的分支-界限分析法，然后以空间桁架系统为例用分支-界限分析法进行了可靠性分析。系统失效的分支-界限分析法直观、明了，适合对实际工程中的复杂系统进行可靠性分析。