On Level Sets of Lorentzian Distance Function

Level sets of Lorentzian distance functions with respect to a point and with respect to an achronal spacelike hypersurface, are analyzed. Some bounds for the Laplacian of such Lorentzian distance functions are obtained and, in relation to them, some spacetime singularity theorems are given.Supported by project BFM2001-3778-C03-01 (Spain).     

Strongly polynomial dual simplex methods for the maximum flow problem

This paper presents dual network simplex algorithms that require at most 2nm pivots and O(n ² m) time for solving a maximum flow problem on a network ofn nodes andm arcs. Refined implementations of these algorithms and a related simplex variant that is not strictly speaking a dual simplex algorithm are shown to have a complexity of O(n ³). The algorithms are based on the concept of apreflow and depend upon the use of node labels that are underestimates of the distances from the nodes to the sink node in the extended residual graph associated with the current flow. © 1998 The Mathematical Programming Society, Inc. Published by Elsevier Science B.V.Research was supported by NSF Grants DMS 91-06195, DMS 94-14438 and CDR 84-21402 and DOE Grant DE-FG02-92ER25126.Research was supported by NSF Grant CDR 84-21402 at Columbia University.     

非线性再生散度模型基于统计曲率的诊断统计量

对非线性散度模型在Euclid空间建立几何结构。在此基础上，研究了均值漂移模型的曲率度量。从而导出相应Cook距离，似然距离等诊断统计量的二阶近似公式。     

F34—Ⅰ型深部X射线治疗机固定照射野间照射量率的比值确定

测量了１２部Ｆ３４－Ⅰ型深部 Ｘ射线治疗机的照射量率，确定了固定照射野在 １５ × １０、１０ × ８、８ × ６、６ × ４单位ｃｍ×ｃｍ）情况下的照射量率比值：在空气介质中，源皮距为３０ｃｍ时，分别为１．０１５、１．０００、０．９７６、０．９５１以及源皮距为４０ｃｍ时，分别为１．０２６、１．０００、０．９７２、０．９４１；在水模体介质中，源皮距４０ｃｍ时，分别为１．１３６、１．０００、０．８７３、０．７３４。利用这些比值，可以快速准确计算出实际照射量率，为治疗恶性肿瘤提供准确可靠的剂量率值。     

The differential solution to the flyinc locus equation of the shot and its application

This paper establishes a locus equation of the shot according to kinematical principes. By using differential and integral calculus and trigonometric function, we have found the extreme valve of the angles of delivery and the best flying distances, with the falling points of t’ short considered. Thus a simple expression showing the relationships among the bes’ angle o delivery, the best flying distance, the height of delivery point and its initial velocity can be attained and a diagram can be made by calculating, showing the best angle of delivery and the best flying distance.     

Calculation of the Distance betweeen Two Random Sets

Two independent random sets are formed by finite systems of independent random variables uniformly distributed on the unit circle. A formula for the distribution of the distance between the sets is derived.     

Vacuum Solutions of Classical Gravity on Cyclic Groups from Noncommutative Geometry

Based on the observation that the moduli of a link variable on a cyclic group modify Connes‘ distance on this group,we construct several action functionals for this link variable within the framework of noncommutative geometry.After solving the equations of motion,we find that one type of action gives nontrivial vacuum solution for gravity on this cyclic group in a broad range of coupling constants and that such a solution can be expressed with Chebyshev‘s polynomials.     

脉冲激光测距机消光比测试系统精度分析

介绍了脉冲激光测距机最大测程———消光比测试方法中的消光比测量原理公式。并以原理公式为依据 ,对影响系统测量精度的诸因素逐一进行了分析和估算 ,根据测量消光比值的合成标准的不确定度进行精度分配。     

Analysis of preemptive loss priority queues with preemption distance

In a queueing system with preemptive loss priority discipline, customers disappear from the system immediately when their service is preempted by the arrival of another customer with higher priority. Such a system can model a case in which old requests of low priority are not worthy of deferred service. This paper is concerned with preemptive loss priority queues in which customers of each priority class arrive in a Poisson process and have general service time distribution. The strict preemption in the existing model is extended by allowing the preemption distance parameterd such that arriving customers of only class 1 throughp — d can preempt the service of a customer of classp. We obtain closed-form expressions for the mean waiting time, sojourn time, and queue size from their distributions for each class, together with numerical examples. We also consider similar systems with server vacations.     

超外差干涉绝对距离测量研究综述

近几年来，基于多波长干涉理论的绝对距离测量技术取得了很大的进展。其中，超外差绝对距离干涉测量可以克服光学元件引起的模耦合误差，这是普通的外差干涉测量所不能避免的。超外差测量还能够实现合成波长相位的实时检测。本文简要介绍了多波长干涉测量（也叫小数重合法）的基本原理，论述和分析了超外差干涉测量的原理，指出了超外差测量的优点。最后，对超外差测量的方案进行了综述，并指出了它们在实际测量中的特点。