Optimal staffing in nonstationary service centers with constraints

This paper considers optimal staffing in service centers. We construct models for profit and cost centers using dynamic rate queues. To allow for practical optimal controls, we approximate the queueing process using a Gaussian random variable with equal mean and variance. We then appeal to the Pontryagin's maximum principle to derive a closed form square root staffing (SRS) rule for optimal staffing. Unlike most traditional SRS formulas, the main parameter in our formula is not the probability of delay but rather a cost‐to‐benefit ratio that depends on the shadow price. We show that the delay experienced by customers can be interpreted in terms of this ratio. Throughout the article, we provide theoretical support of our analysis and conduct extensive numerical experiments to reinforce our findings. To this end, various scenarios are considered to evaluate the change in the staffing levels as the cost‐to‐benefit ratio changes. We also assess the change in the service grade and the effects of a service‐level agreement constraint. Our analysis indicates that the variation in the ratio of customer abandonment over service rate particularly influences staffing levels and can lead to drastically different policies between profit and cost service centers. Our main contribution is the introduction of new analysis and managerial insights into the nonstationary optimal staffing of service centers, especially when the objective is to maximize profitability. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 615–630, 2017     

单一基窃听方式下B92协议的安全性研究

从概率论和信息论两个角度对单一基窃听方式下B92协议的安全性进行了研究,得出了最佳窃听角度和信源概率分布之间的关系;以马尔柯夫串联信道模型计算了Alice和Eve之间及Alice和Bob之间的信息量,并与广义量子测量窃听进行了比较,结果表明,Eve采用单一基窃听不仅能以较高概率猜中Alice发出的量子态,并且能获得较高平均互信息.得出的结论为合法通信者的安全通信和对窃听者的检测提供了标准.     

一种基于导航点的航天器相对运动轨迹生成策略

针对圆(近圆)轨道航天器相对运动的固定时间状态转移问题,提出了一种基于导航点的多脉冲优化轨迹生成策略.从相对运动动力学出发,应用最优控制理论给出了基于连续推力的最优转移轨线,将引入的导航点限定在最优转移轨线上得到其位置参数;然后利用导航点位置参数建立了脉冲约束下的基于脉冲的优化轨迹生成模型,采用二次规划算法求解,通过改变导航点位置和脉冲间隔优化轨迹.仿真算例验证了策略的有效性.     

Capacity expansion and cost efficiency improvement in the warehouse problem

The warehouse problem with deterministic production cost, selling prices, and demand was introduced in the 1950s and there is a renewed interest recently due to its applications in energy storage and arbitrage. In this paper, we consider two extensions of the warehouse problem and develop efficient computational algorithms for finding their optimal solutions. First, we consider a model where the firm can invest in capacity expansion projects for the warehouse while simultaneously making production and sales decisions in each period. We show that this problem can be solved with a computational complexity that is linear in the product of the length of the planning horizon and the number of capacity expansion projects. We then consider a problem in which the firm can invest to improve production cost efficiency while simultaneously making production and sales decisions in each period. The resulting optimization problem is non‐convex with integer decision variables. We show that, under some mild conditions on the cost data, the problem can be solved in linear computational time. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 367–373, 2016     

（2015卫星导航）基于双天线载波相位差的卫星导航接收机抗欺骗技术研究

针对欺骗干扰信号难以有效实时模拟真实卫星信号空间分布特性的特点,本文提出了利用双天线载波相位差进行欺骗信号检测的方法。在已知接收机天线阵基线以及姿态条件下,同一路信号在两副天线上表现出的相位差与天线基线长度与信号入射相关。而信号入射角是空间信号的物理传播特性,欺骗干扰源无法通过数字方式改变。以通过卫星星历获取所跟踪卫星的精确位置为先验信息,即可确定真实信号在已知天线阵上的载波相位差,从而实现对欺骗信号的有效检测。本文分析了载波相位差计算的各种误差源,并在此基础上建立了针对欺骗信号的二元假设检验。最后,通过理论分析和仿真实验,验证了本文提出的欺骗信号检测技术的有效性,并得出了天线阵基线越长、入射方位角越小,载波相位差检测技术对欺骗信号的检测性能越优的结论。     

基于高斯伪谱法的弹道跟踪制导律

针对拦截临近空间高超声速飞行器的弹道跟踪过程，设计了一种基于高斯伪谱法的跟踪制导律。为了对标称弹道进行精确跟踪，基于线性二次型跟踪问题，应用最优控制理论推导最优解的充要条件，得到带时变增益的线性状态反馈控制量的表达式；基于高斯伪谱法，在离散的勒让德-高斯(LG)点上利用标称弹道数据计算差分矩阵和系数矩阵，求得状态扰动反馈控制律。仿真结果表明，该方法能够快速、有效的消除跟踪误差，满足在线实施要求。     

Doubly Stochastic Sequential Assignment Problem

This article introduces the Doubly Stochastic Sequential Assignment Problem (DSSAP), an extension of the Sequential Stochastic Assignment Problem (SSAP), where sequentially arriving tasks are assigned to workers with random success rates. A given number of tasks arrive sequentially, each with a random value coming from a known distribution. On a task arrival, it must be assigned to one of the available workers, each with a random success rate coming from a known distribution. Optimal assignment policies are proposed for DSSAP under various assumptions on the random success rates. The optimal assignment algorithm for the general case of DSSAP, where workers have distinct success rate distribution, has an exponential running time. An approximation algorithm that achieves a fraction of the maximum total expected reward in a polynomial time is proposed. The results are illustrated by several numerical experiments. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 124–137, 2016     

Equivalent accelerated life testing plans for log‐location‐scale distributions

Accelerated life testing (ALT) is widely used to determine the failure time distribution of a product and the associated life‐stress relationship in order to predict the product's reliability under normal operating conditions. Many types of stress loadings such as constant‐stress, step‐stress and cyclic‐stress can be utilized when conducting ALT. Extensive research has been conducted on the analysis of ALT data obtained under a specified stress loading. However, the equivalency of ALT experiments involving different stress loadings has not been investigated. In this article, a log‐location‐scale distribution under Type I censoring is considered in planning ALT. An idea is provided for the equivalency of various ALT plans involving different stress loadings. Based on this idea, general equivalent ALT plans and some special types of equivalent ALT plans are explored. For demonstration, a constant‐stress ALT and a ramp‐stress ALT for miniature lamps are presented and their equivalency is investigated. © 2010 Wiley Periodicals, Inc. Naval Research Logistics, 2010     

一种跳频通信中增加可用频率数的方法及其性能分析

针对跳频通信中传统收发同频体制的不足,介绍了一种新的增加可用频率数的方法。提出了不对称频率表的概念及设计,对其在短波跳频通信中提高跳频处理增益、改善系统抗阻塞干扰等性能进行了分析,并与常规跳频进行了比较,得出了一些有益的结论。     

小口径舰炮对空虚拟校射校正量的最优估计

首先建立了小口径舰炮对空虚拟校射脱靶量的观测方程,分析了脱靶量的统计性质,在此基础上推导出校正量的最优估计量,并用仿真结果验证了结论的正确性。