几何基础

Aimed at a changing power mechanism,a ratchet mechanism with double electric pawls,we introduce the operating principle,establish its model and optimize the important geometry parameters in its structure design in this paper.

针对一种动力转换机构———弹性双棘爪棘轮机构，介绍了它的工作原理，对其结构设计中的重要几何参数建立了模型，进行了优化，为下一步的动力学优化设计打下了基础。

Aimed at a changing power mechanism, a ratchet mechanism with double electric pawls, we introduce the operating principle, establish its model and optimize the important geometry parameters in its structure design in this paper. This founds a basis of next step for optimum design of its structural dynamics.

针对一种动力转换机构－弹性双棘爪棘轮机构，介绍了它的工作原理，对其结构设计中的重要几何参数建立了模型，进行了优化，为下一步的动力学优化设计打下了基础。

On applying the theory of differential geometry, the research shows the procedure for determining the required cutter path for cutting conical cam profile using a NC milling machine based on the analytical profile expression of conical cam with oscillation conical roller follower or with a translating conical roller follower established in 3D space. The analytical expression of cutter path is provided for a tapered endmill cutter, whose size may be identical to or smaller than that of the conical roller.

应用微分几何理论，以在3维空间所建立的圆锥滚子摆动从动件和直动从动件圆锥凸轮机构凸轮廓面的解析表达式为基础，对数控铣床加工圆锥凸轮廓面所需刀具轨迹方程的建立方法进行了研究，根据所采用的锥形刀尺寸等于或小于圆锥滚子尺寸的情况，推导出相应的刀具轨迹方程的解析表达式。

Wire electrode based on the trajectory of the different forms of control, WEDM can be divided into three types: one is shaped by the imitation controlled cutting in line in advance and work to create the same shape by mold, when processing the workpiece at the same time rough and on the mold clamping in the machine tool table, in the process of cutting wire electrode tightly against the mold on the edge of the track for the mobile, thus cutting out and die on the same shape and precision to the workpiece; another One is the electro-optical tracking control, to carry out the cutting line, before the basis of certain parts to enlarge the proportion of drawings depicts an electro-optical tracking map-processing machines will be placed in design stage of electro-optical tracking, tracking platform Photoelectric first line of graphics has always been to follow the track of the Mexican campaign, and then through the use of electrical, mechanical linkage to control the machine tool table, together with the workpiece so相似形wire electrode relative movement, thus cutting out the same shape and design to the workpiece; again a digital control, the use of advanced automatic control of digital technology-driven machine tool in accordance with the pre-processing parameters according to the workpiece geometry pre-processing procedures for the preparation of a good CNC auto-complete processing, the production does not require appearance on board the need to map to enlarge map of the previous two form of control has a higher machining accuracy and a broad range of applications, both at home and abroad more than 95% have adopted WEDM NC.

根据对电极丝运动轨迹的控制形式不同，电火花线切割机床又可分为三种：一种是靠模仿形控制，其在进行线切割加工前，预先制造出与工件形状相同的靠模，加工时把工件毛坯和靠模同时装夹在机床工作台上，在切割过程中电极丝紧紧地贴着靠模边缘作轨迹移动，从而切割出与靠模形状和精度相同的工件来；另一种是光电跟踪控制，其在进行线切割加工前，先根据零件图样按一定放大比例描绘出一张光电跟踪图，加工时将图样置于机床的光电跟踪台上，跟踪台上的光电头始终追随墨线图形的轨迹运动，再借助于电气、机械的联动，控制机床工作台连同工件相对电极丝做相似形的运动，从而切割出与图样形状相同的工件来；再一种是数字程序控制，采用先进的数字化自动控制技术，驱动机床按照加工前根据工件几何形状参数预先编制好的数控加工程序自动完成加工，不需要制作靠模样板也无需绘制放大图，比前面两种控制形式具有更高的加工精度和广阔的应用范围，目前国内外95%以上的电火花线切割机床都已采用数控化。切割属电加工范畴，是由前苏联人发明的，我国是第一个用于工业生产的国家，当时由复但大学和苏州长风机械厂合作生产的这是最早的机型叫复旦型，我们国内在此基础上发展了快走丝系统。欧美和日本发展了慢走系统LS

Firstly, this paper discusses the development actuality of the research on double-front axle steering system and power-train of automobile. Based on the structure of the design experiences from others, the kinematics formula of double-front axle steering system is fetched, and the mathematical model of optimization design of double rocking arms mechanism and steering trapezium mechanism is established by space geometry method. Considering the difference between the real steering angle from wheels and the ideal steering angle from the ideal formula as the objective function, the optimization design method of double-front axle steering system is presented.

本文首先论述了国内外对汽车双前桥转向系统和动力传动系统研究的发展状况，在总结前人研究设计经验的基础上推导出汽车双前桥转向系统运动学关系，运用空间几何法建立了双前桥双摇臂机构及转向梯形机构优化的数学模型，以转向轮实际转角值与理想公式求出的理想转角值之间的误差达到最小为目标函数，提出了双前桥转向系统参数的优化设计方法。

Based on analysis of ISAR imaging theory in detail, the projection image plane is firstly built according to arithmetic imaging model. We can get ideal image, with which we are able to discuss the effects of the ISAR target image with spinning axis during integration time.

在详尽分析了ISAR成像机理的基础上，首先提出了以数学建模的方法建立目标模型的瞬时几何投影像，讨论在相干积累时间内目标等效旋转轴矢量对成像的影响。

Aiming at the problem in the existing voxelization algorithms, a block-based algorithm is presented: GPU clipping method is used to voxelize the surface in every block, and ray intersection method is adopted to generate seeds filling the inner/outer space of blocks; among blocks, three seed planes are designed to help seeds span the blocks, so that a great deal computation for intersection is avoided.

提出以分块为基础的高分辨率实体体素化算法：在分块内部，采用基于图形处理器(Graphics Processing Unit， GPU)的切面光栅法对分块表面体素化过程进行加速，采用射线求交方式生成种子并进行块内填充；在分块之间，设计了3方向的种子扩散面及跨块扩散机制，避免因分块而导致的大量几何求交运算，提高了效率。

In comparison with the computation point by point according to Hencky stress equations, determination of the stress in slip line field by use of the geometrical mapping is clear and simple.

文献〔1〕〔2〕〔3〕在Prager极点轨迹基础上提出了一种摆线映射法，这是滑移线场在口一，应力平面上的一种几何映射，其图形由两族相互正交的摆线构成。

After the vein pattern was segmented from the vein image by an improved NiBlack method,authors obtained the vein pattern skeleton by an improved conditional thinning algorithm.On the basis,the algorithm extracted seven modified moment invariants of the vein pattern skeleton as the input vector of SVM for the recognition of vein pattern.The experiments on a database including 500 samples has achieved a recognition rate of 95.5%,and it indicates the algorithm is effective.

算法在采用修正的NiBlack算法从原始图中分割出静脉纹路，然后采用改进的条件细化算法进行细化获得静脉骨架的基础上，提取静脉骨架的7个修正的几何不变矩作为支持向量机分类器的输入进行静脉分类识别，在有500个样本的数据库上进行实验，获得了95.5%的识别率，表明了算法的有效性。

In studies of interaction among pile, platform that above it and surrounding soil, this paper employ the concept of plate element to simulate the loading character of platform, and employ the concept of solid element to simulate the character of pile and soil, using the finite element method after understanding the geometry properties of pile, soil and the platform. Analyzing the loading properties of the three entities above and their deformation, this paper also employ a special element, Penalty Element. The introduction of penalty element of this kind has served to guarantee the join harmony of displacement between solid element and plate element, thereby effectively resolving the join problem between platforms, pile that support it and surrounding soil.Considering significant property difference between pile material and its surrounding soil, there may be much shear stress on their contact interface produced under vertical load, thus causing displacement or fission. Therefore it is necessary to adopt one special constitutive law of this kind of contact interface, which can reflect its feature of loading and deformation thoroughly. On the basis of the deformation feature and constitutive laws of some contact interface obtained by Zhang Dongji and people concerned through some single-shear experiments on contact interface between structure and soil, this paper employ one pile-soil three-dimensional constant thickness contact interface model to simulate the " slide" taken place on the interface between pile and its surrounding soil. With this kind model, this paper has also created one finite element model, which can be applied to perform finite element calculation and analyze the pile-loading feature, and deduced its element stiffness matrix.

在承台-桩-土共同作用中，考虑桩与承台的几何特性，采用有限元方法，用实体单元模拟桩土，用板单元模拟承台，更具体地分析桩和承台的受力特性和变形，而且还采用罚单元—既实体单元与板单元之间连接必须满足变形协调条件，来有效地解决了承台与桩土的连接问题，且在桩土共同作用中，由于桩体结构的材料性能与周围土层性质相差较大，在竖向荷载下有可能在其接触面上产生较大的剪应力从而导致错动或开裂，因此，为了充分反映桩土接触面上的受力及变形特征，应采用一种桩土接触面特有的本构关系，即利用张冬霁等人关于结构与土体接触面单剪试验所得到的接触面变形特征及其本构关系，引入桩-土三维等厚度接触单元来模拟桩与桩侧土之间的&滑移&，在此基础上建立可用于桩基承载性状分析的有限元计算单元模型，并推导出了各单元的刚度矩阵。

I am accused of being overreligious," she said in her quiet, frank manner,"but that does not prevent me thinking the children very cruel who obstinately commit such suicide.""

客人们在卡罗利娜·埃凯家里，举止就文雅一些，因为卡罗利娜的母亲治家很严厉。

Designed by French fashion house Herm è s, this elegant uniform was manufactured in our home, Hong Kong, and was the first without a hat.

由著名品牌 Herm è s 设计，这件高贵的制服是香港本土制造，是我们第一套不配帽子的制服。