边界条件对自然河流形成及演变影响机理的实验研究

运用自然模型法,采用清水冲刷成功地塑造了室内天然小河。实验研究了不同的初始河流几何边界条件以及水流条件对河流演变的影响。研究发现流量对河流展宽幅值影响最大。水流入射角的大小与河流展宽幅度及河流弯曲度的变化没有必然的联系,30°入射角时小河的河流展宽及弯曲度变化最明显。入射角对河流演变的作用只是短期的,且在演变初始阶段影响较大。受初始边界条件的影响,河流向下游演变具有滞后性及曲率变化的传递性等特点。本文最后分析了河流演变过程中的泥沙分选现象。     

一种高精度低温漂带隙基准源的设计

该文参考了带隙基准电压源领域的现阶段技术,结合自偏置共源共栅电流镜以及适当的启动电路、补偿电路,设计了一种高精度、低温漂的多输出带隙基准电路。首先简述了传统带隙电压基准的基本原理,然后详细阐述了具体的各电路设计过程。该基准电压源可广泛应用于电源管理芯片等对能耗要求极高的芯片中。     

利用曲面曲率划分的高速数控加工进给速度修正

为保证数控加工中的切削效率和机床运动的平稳性,提出了基于曲面曲率划分的进给速度修正方法。以最大工作进给速度的变化比率为阈值,把零件表面的法曲率半径划分为不同的区域;在不同的曲率区域内,分别以恒定的刀触点速度对进给速度进行修正,修正后的进给速度随着零件表面曲率的变化而自适应变化;实例表明该方法具有合理性和有效性。     

弯管传感器弯径比的三坐标测量方法

对ZWL型智能弯管流量计中弯管传感器弯径比测量方法地不断探索,提出了用三坐标测量机对弯管传感器进行测量的三坐标测量方法.通过建立求解弯径比的数学模型,三坐标测量机测取三维坐标点和用MATLAB软件编写弯径比的计算软件,完成了对弯径比的计算.此方法是将测头直接伸入管内的接触式测量,能直接反映弯管的形状特征,测量结果具有较高的精度,且操作方便,具有通用性.     

平面曲线运动加速度公式的物理-数学推导法

指出了现有平面曲线运动加速度公式物理推导方法的不足．通过将自然坐标系和二维笛卡尔坐标系相结合，将质点运动的物理量和运动曲线的数学量相结合，利用加速度的定义及曲率圆和曲率的概念从数学上严格地推导出了一般平面曲线运动的加速度公式，并对该推导方法的意义进一步作了讨论．     

Translation Surfaces with Zero Mean Curvature in （2+p）-Dimensional Pseudo-Euclidean Space E22+p or Ep2+p

Let Ep^2＋p（resp.E2^2＋p） be a （2＋p）-dimensional pseudo-Euclidean space with the index p （resp.2）. The maximal spacelike or minimal timelike translation surfaces M^2 in Ep^2＋p or E2^2＋p are considered and a complete classification is given.     

Optimization of a piezoelectric linear motor in terms of the contact parameters

The contact kinetics of piezoelectric linear motors determines the operational characteristics like speed and torque or transmitted mechanical power and efficiency. Piezoelectric linear motors are driven by tangential stress in the interface between tip of shaking beam and slider. A good contact between the tip and slider is necessary for a reliable analysis of the motor, which is needed for the optimization of its performance. The piezoelectric linear motor was fabricated and the characteristics of the motor were investigated by external conditions such as tip shape with different curvatures and contact force between the tip and the slider. It was found in this investigation that the optimal curvature of the tip and the contact force are curvature of 1 and 10, respectively, for the high actuating speed, and curvature of 1 and 40 N, respectively, for the high actuating force. Finally, tip shape has an influence on the characteristics of linear motor.     

An Efficient Active Contour Model Through Curvature Scale Space Filtering

Active contour models can be successfully used in multimedia database retrieval systems if they have good accuracy and high speed. The majority of existing active contour models do not lock on to interest objects very accurately and quickly especially in complex images. The behavior of the active contour is generally controlled by its internal and external energies. Internal energy is composed of two parts; the first part acts to shorten the active contour as it iterates towards the interest object, while the second part is the curvature of the active contour and forces smoothness of active contour during its movement towards interest object. In this paper, first a reformulated internal energy is proposed to improve the computation of curvature at point v _i by making use of the three points v _{i – 1}, v _i and v _{i + 1}. Second, an accurate and high speed active contour model, SAC is proposed based on reformulating internal energy by removing the curvature part and using Gaussian filtering with low scale of smoothing. The SAC model has only one parameter that affects the internal energy of active contour and as a result of using the Curvature Scale Space (CSS)¹ technique for smoothing, the SAC model is more independent of model parameter setting and the initial snake.     

基于高光线模型修改NURBS曲面不光顺性

高光线模型是一种评估曲面光顺性的强有力工具．提出一种基于高光线模型修改NURBS曲面不光顺性的新方法，将高光线模型对应的非线性方程组转化成线性方程组，从而大大简化了问题的复杂性，修改后的控制点通过解一组线性方程求得．新NURBS曲面的某些点具有指定的法方向．该方法直观、适用于实时交互设计，通过简单的操作就能修改NURBS强曲面，从而使其具有良好的光顺性．还给出了测试文中方法有效性的实例．     

常曲率空间中曲面的等距变形

Ｏ．Ｂｏｎｎｅｔ首先研究了保持主曲率不变的曲面的等距变形问题，并证明了常中曲率曲面具有保主曲率的等距变形。１９８５年Ｓ．Ｓ．Ｃｈｅｒｎ证明了在欧氏空间中具有保持主曲率不变的非常中曲率曲面是Ｗ－曲面。