特征参数

Feature parameters are achieved by comparing the coefficient of standard representation and general representation. As for cone, parameter of general representation has no explicit geometric meaning and can not reflect design intent.

基于二次曲面的统一表示方程，采用最小二乘法进行参数拟合，通过对比其标准形式和二次曲面的统一表示方程，确定圆柱曲面特征带有明显几何意义的参数圆柱轴线法矢量、圆柱的中心和半径。

It is composed of a deformable parametric curve and corresponding energy function.

主动轮廓模型是一种基于高层信息的目标轮廓特征提取算法，它由一条可变形的参数曲线及其相应的能量函数组成，以最小化能量函数为目标，控制参数曲线变形，具有最小能量的闭合曲线就是目标轮廓。

Based on the new explicit parametric solution to the generalized Sylvester matrix equation, a parametric approach for eigenstructure assignment via output feedback is proposed.

基于广义Sylvester矩阵方程新的显式参数解，提出了输出反馈特征结构配置的一种参数化方法。

Based on the parametric eigenstructure assignment result for descriptor second-order systems, the parametric expression of the optimization index is obtained.

根据广义二阶动力学系统基于状态加微分反馈的参数化特征结构配置结果，给出了优化指标的完全参数形式。

Based on a general parametric eigenstructure assignment result proposed for descriptor linear systems via proportional plus partial derivative state feedback and a result for generalized eigenvalue sensitivity problem of matrix pairs, parametric representation of the closed-loop eigenvalue sensitivities to the perturbed elements in the open-loop system matrices is obtained. An effective algorithm for eigenvalue assignment with minimum sensitivity in descriptor linear systems via proportional plus partial derivative state feedback is then proposed.

摘要基于广义线性系统比例与部分状态导数反馈参数化特征结构配置结果和矩阵对广义特征值灵敏度结果，得到了关于开环系统矩阵中摄动元素的闭环特征值灵敏度的参数表达式，并在此基础上提出了广义线性系统比例与部分状态导数反馈最小灵敏度特征值配置的有效算法。

In this paper dimension-chain is used to calculate the last effective dimension formed under the influence of tolerances and other distortions. Feature modeling is applied to construct the three-dimension mode of the parts in solidworks. Based on the parametric design function, simulation of assembling result is realized by making use of VB to develop Solidworks. The accomplish of variable parametric design system in tolerance designing is realiazed.

运用尺寸链技术计算出零件在公差及其他变形影响下的最终作用尺寸，利用solidworks中特征建模方法建立起装配体的三维模型，并根据该软件的参数化设计功能，利用VB对其进行二次开发，模拟了装配结果，实现了变参数设计方法在公差设计评价技术上的应用。

The influences of relevant parameters such as mass velocity, heat flux, pressure, inlet subcooling, and compressible volume on the threshold, period and amplitude of oscillation were studied.

分别研究了压力降脉动和密度波脉动的特征、脉动机理及其有关参数，如质量流速、系统压力、过冷度、可压缩容积、热负荷等参数对脉动界限值、周期和振幅的影响。

Secondly, the key technology of how to align point cloud with surface feature model of human body, analyze error, adjust position are researched and the algorithms of calculating center of mass, inertia axis, and symmetry plane are successfully introduced.

然后，研究了对齐后的模型，如何将点云投影到曲面，识别出曲面特征，并对点云进行参数化和采用基于约束及能量优化法算法进行曲面重构，快速的建立不同人体的光滑G~1连续的B样条参数曲面模型。

Secondly, by establishing a discrete time Markov model with spatial reuse for a MANET, we analyze the performance of the network under the AODV routing protocol. The average route length and the probability to communicate within a limited hop distance are obtained. Several performance parameters of the route discovery and route maintain process are analytically studied, such as the probability generating function and the expectation of the flooding distabce. the probability that a route is discovered by a query packet with a "hop limit", the probability that a request packet finds a valid route, the average time needed to discover a valid route and the cost to successfully route a data packet to its destination. Furthermore, we present a concrete example based on the transmitter characteristic of directional antennas and obtain the corresponding results.

建立了移动自组网络空间可重用的离散时间马氏链模型，得到了AODV路由协议下网络任意两节点间的平均路由长度、在指定"跳限"要求下通信的概率；对随选型路由协议下路由发现和路由维护过程中若干网络性能参数进行了解析分析，如网络中任意两节点问的泛洪距离的概率母函数及其期望、限定泛洪步数时成功寻路的概率、发现一条有效路由的平均时间、成功路由的代价等；并基于定向天线的发射特征给出了一个具体实例，分析计算了相应的网络性能参数。

Through the new research methods, this thesis has made the following contributions in this field: 1. For the first time the curvature radii and relative angles of a planar continuous curve at discrete points are chosen as local parameters to represent the curve, which reflect clearly the local geometrical characteristics of the curve and are easy to be dealt with.

借助于新的研究方法，本文在这一领域作出如下贡献：（1）首次提出用曲线上离散点处曲率半径和相对转角作为局部参数表示平面连续曲线，直观地反映曲线各个局部的几何特征，且便于曲线的修改和变换，并通过机构运动分析，快速求出机构轨迹的这两个局部参数。

According to the clear water experiment, aeration performance of the new equipment is good with high total oxygen transfer coefficient and oxygen utilization ratio.

曝气设备的动力效率在叶轮转速为120rpm～150rpm时取得最大值，此时氧利用率和充氧能力也具有较高值。

The environmental stability of that world - including its crushing pressures and icy darkness - means that some of its most famous inhabitants have survived for eons as evolutionary throwbacks, their bodies undergoing little change.

稳定的海底环境─包括能把人压扁的压力和冰冷的黑暗─意谓海底某些最知名的栖居生物已以演化返祖的样态活了万世，形体几无变化。