Sequential Discrete p-Facility Models for Competitive Location Planning

Two new models for duopolistic competitive discrete location planning with sequential acting and variable delivered prices are introduced. If locations and prices are assumed to be set once and for all by the players, the resulting bilevel program is nonlinear. Under the assumption that further price adjustments are possible, i.e., that a Nash equilibrium in prices is reached, the model can be simplified to a linear discrete bilevel formulation. It is shown that in either situation players should not share any locations or markets if they strive for profit-maximization.For the situation with price adjustments, a heuristic solution procedure is suggested. In addition, the bilevel models are shown to serve as a basis from which different well-known location models – as, for example, the p-median problem, the preemptive location problem and the maximum covering problem – can be derived as special cases.     

The Newton Bracketing Method for Convex Minimization

An iterative method for the minimization of convex functions f :ⁿ , called a Newton Bracketing (NB) method, is presented. The NB method proceeds by using Newton iterations to improve upper and lower bounds on the minimum value. The NB method is valid for n = 1, and in some cases for n > 1 (sufficient conditions given here). The NB method is applied to large scale Fermat–Weber location problems.     

Shrinkage estimators of the location parameter for certain spherically symmetric distributions

We consider estimation of a location vector for particular subclasses of spherically symmetric distributions in the presence of a known or unknown scale parameter. Specifically, for these spherically symmetric distributions we obtain slightly more general conditions and larger classes of estimators than Brandwein and Strawderman (1991,Ann. Statist.,19, 1639–1650) under which estimators of the formX +ag(X) dominateX for quadratic loss, concave functions of quadratic loss and general quadratic loss.Research supported by NSF grant DMS-88-22622     

二维图象中二阶导数滤波器边缘定位误差的理论分析

本文从理论上讨论了低通滤波后二维图象中弯曲边缘的定位误差问题.边缘位置通常由二阶导数算子的零交叉点定义.研究表明:梯度方向上的二阶导数算子(secondderivativein gradient direction SDGD)产生向心的、可预测的边缘偏移;而线性拉普拉斯算子(Laplacian Operator)产生相反方向(离心)的可预测位置偏移.由此可推断:两者之和——称之为PLUS,将产生比其组成成份(SDGD 和 Laplace)更为精确的边缘定位算子.文章讨论了常用的低通滤波器(如 Gaussian 滤波器及 Tepee 滤波器)对边缘定位精度的影响.     

Single facility location problems with unbounded unit balls

In this paper we consider a new class of continuous location problems where the distances are measured by gauges of closed (not necessarily bounded) convex sets. These distance functions do not satisfy the definiteness property and therefore they can be used to model those situations where there exist zero-distance regions. We prove a geometrical characterization of these measures of distance as the length of shortest paths between points using only a subset of directions of their unit balls. We also characterize the complete set of optimal solutions for this class of continuous single facility location problems and we give resolution methods to solve them. Our analysis allows to consider new models of location problems and generalizes previously known results.     

基于元胞传输模型的可变信息标志选址问题研究

随着智能交通技术的发展，可变信息标志(VMS)被广泛应用于动态交通管理中.元胞传输模型(CTM)可以较好地模拟交通流激波、排队形成与消散等交通流动力学特性.应用CTM对VMS选址问题进行了研究.数值模拟结果表明，合适的VMS位置可以减少系统内所有车辆的行驶时间.还分析了路径选择概率变化与VMS位置之间的关系.在一定范围内，交通事故越严重，VMS应设置在距离事故地点越远的地方. 关键词： 可变信息标志 选址问题 元胞传输模型 数值模拟     

基于曲线拟合的亚像素边缘定位方法的研究

图像的边缘定位是图像测量的关键之一,随着测量精度要求的提高,已由早期的像素级边缘定位发展到了现在的亚像素级边缘定位。根据地球在地球敏感器CCD阵面中的成像特性,提出了一种基于曲线拟合的亚像素边缘定位方法以获取地球“灼热圆盘”的边缘。该方法利用曲线拟合获得的拟合斜率以及灰度值来提取图像的边缘。仿真结果表明,采用曲线拟合亚像素边缘定位法可使图像的边缘定位精度达到百分之几个像素,具有较高的精度。     

A numerical model of multimode fiber PON frequency response

Frequency response of passive optical network (PON) based on multimode fibers is investigated. The network comprises fibers, connectors and splitters/couplers. It is shown that due to mode filtering at splitters, the frequency response is different for different network nodes in otherwise symmetrical network.     

天文导航中星体高精度细分定位方法研究

介绍了一种从星体图像中高精度提取恒星位置的方法.这种方法把星光成像看成是高斯点扩散函数模型,利用线性内插和最小二乘法拟合得到高斯曲面参数,从高斯曲面模型中得到亚像素级的恒星位置.由于直接进行高斯曲面拟合计算非常复杂,将二维曲面拟合转化为两个方向上的一维曲线拟合,分别得到不同的曲面系数.仿真结果表明当信噪比小于0.05时,定位精度能达到1/20像素,与质心法比较,高斯曲面拟合法精度高,抗噪声能力强.     

一种复杂车辆图像中的多车牌定位方法

针对复杂背景中多个车牌的定位问题,提出一种新的定位方法.该方法综合利用边缘检测、连通域分析、倾斜矫正等多种方法,解决了复杂背景中定位难的问题.能够准确定位杂乱背景中的车牌,对天气、光照变化、车牌在图像中的移动和旋转等,具有良好的适应能力.该方法为后续的字符分割和字符识别提供旋转角度、字符区域定位信息.