卫星数传调度模型研究

卫星数传调度问题是一个具有多时间窗口、多资源约束的优化问题。针对该问题,建立了卫星数传需求模型、任务模型和调度模型。在建模过程中,采用了框架模型形式,把问题中的主要约束封闭于每个数传任务中,这在降低调度模型复杂度的同时,也降低了调度算法设计难度。还提出了调度算法设计思想,并设计了一基于灵活度的调度算法。仿真表明,所建立的模型及算法对解决卫星数传调度问题是可行的。     

HLA数据回放及其可通用性问题研究

为了给HLA分布仿真系统提供运行数据的回放能力并解决各种回放策略都必须面对的数据完备、时序准确、运行高效及回放方法的可通用性等问题,对HLA联邦中的数据回放问题进行了研究,分析了HLA仿真中的回放需求以及HLA对回放实现技术的影响,指出回放方法的可通用性实质上是联邦独立性的概念,研究了将回放数据对象化处理的方法,针对成员式数据回放策略、基于对象序列化技术和成员自动生成技术提出了一种可通用的HLA数据回放实现方案,最后介绍了通用HLA数据回放工具的应用情况。     

P2P系统中数据复制算法研究

比较分析了P2P系统中各种数据复制算法,并提出了一种基于LDPC编码的数据复制算法Dyre,数据块采用动态分配算法存储到节点中,在节点邻居中保存数据块的副本以提高数据块的有效性,数据块的数量过小时重建数据块。实验表明,即使节点的可靠性非常低,该算法也能够获得很高的数据可用性。     

一种新的多传感器多机动目标快速跟踪算法

基于FAFDA滤波算法,根据Houles和Shalom将PDA算法推广到解决两个传感器单目标的跟踪问题的思路中,构造一种两个同类传感器的序列观测数据的融合来跟踪多个机动目标的数据关联方法(MSFAFDA)。它主要使用的是点/航迹联合和序列估计法。算法计算量远小于原先的顺序和并行多传感器联合概率数据关联算法,蒙特卡洛仿真结果也表明它对多机动目标的跟踪具有比FAFDA更好的跟踪性能。     

基于数据库的MO图层控制机制

MapObjects中对图层的控制方法是预先将图层的控制信息写在程序里,在程序运行时对图层进行约束。这种通过编写程序进行控制的方法不但比较麻烦,而且当图层的控制方式发生变化时,维护困难。提出基于数据库的图层管理和控制机制,先将图层的控制信息放在数据表里,系统运行时动态读取图层的控制信息,实现对图层进行方便、直观地约束。     

A model of supply-chain decisions for resource sharing with an application to ventilator allocation to combat COVID-19

We present a stochastic optimization model for allocating and sharing a critical resource in the case of a pandemic. The demand for different entities peaks at different times, and an initial inventory for a central agency are to be allocated. The entities (states) may share the critical resource with a different state under a risk-averse condition. The model is applied to study the allocation of ventilator inventory in the COVID-19 pandemic by FEMA to different U.S. states. Findings suggest that if less than 60% of the ventilator inventory is available for non-COVID-19 patients, FEMA's stockpile of 20 000 ventilators (as of March 23, 2020) would be nearly adequate to meet the projected needs in slightly above average demand scenarios. However, when more than 75% of the available ventilator inventory must be reserved for non-COVID-19 patients, various degrees of shortfall are expected. In a severe case, where the demand is concentrated in the top-most quartile of the forecast confidence interval and states are not willing to share their stockpile of ventilators, the total shortfall over the planning horizon (until May 31, 2020) is about 232 000 ventilator days, with a peak shortfall of 17 200 ventilators on April 19, 2020. Results are also reported for a worst-case where the demand is at the upper limit of the 95% confidence interval. An important finding of this study is that a central agency (FEMA) can act as a coordinator for sharing critical resources that are in short supply over time to add efficiency in the system. Moreover, through properly managing risk-aversion of different entities (states) additional efficiency can be gained. An additional implication is that ramping up production early in the planning cycle allows to reduce shortfall significantly. An optimal timing of this production ramp-up consideration can be based on a cost-benefit analysis.     

Retailer's rationale to refuse consumer returns in supply chains

While accepting consumer returns has long been proposed as a solution to resolve the consumer valuation uncertainty problem, there are still a sizable portion of retailers who insist on a “no return” policy. In this article, we offer an economic rationale for these seemingly unreasonable strategies in a supply chain context. We demonstrate when and why the retailer may benefit from refusing consumer returns, even though offering consumer returns allows the supply chain to implement the expostmarket segmentation. Granting the retailer the right to refuse consumer returns may sometimes improve supply chain efficiency: it eliminates the manufacturer's attempt to induce inefficient consumer returns and bring the equilibrium back to that in the vertically integrated benchmark. We also find that the refund and the retail price can move in the opposite directions when product reliability varies, and consumer returns have a nontrivial impact on the quality choice. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 686–701, 2015     

Environmental regulation in project‐based industries

We study the environmental regulation of industrial activities that are organized as projects. Applications arise in construction, ship and aircraft building, and film making, among other industries. Relative to manufacturing, environmental regulation is different in project‐based industries, due to the uniqueness and geographical diversity of projects, and a lack of product takeback programs. Because the amount of waste and pollution generated by project companies can be large, regulators need environmental policies to ensure reduction of waste and pollution. We consider a regulator who attempts to maximize social welfare. We model this problem as a bilevel nonlinear program. The upper level regulator specifies waste reduction targets, which the lower level project companies meet using waste stream reduction and remediation of pollution, while attempting to control their project costs. We find that high waste diversion targets lead to outcomes with little pollution, but excessive project costs and only modest waste stream reduction. Projects that have lower task precedence density, or that have pollutants with different environmental impacts, show larger increases in project cost and time resulting from regulation. We describe a subsidy for waste stream reduction that coordinates the system, and we estimate the value of coordination. We also describe a bonus that encourages truthful reporting by project companies, and evaluate the relative cost and effectiveness of the subsidy and the bonus. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 228–247, 2015     

Pricing and inventory management during new product introduction when shortage creates hype

In this study, we analyze the joint pricing and inventory management during new product introduction when product shortage creates additional demand due to hype. We develop a two‐period model in which a firm launches its product at the beginning of the first period, before it observes sales in the two periods. The product is successful with an exogenous probability, or unsuccessful with the complementary probability. The hype in the second period is observed only when the product is successful. The firm learns the actual status of the product only after observing the first‐period demand. The firm must decide the stocking level and price of the product jointly at the beginning of each of the two periods. In this article, we derive some structural properties of the optimal prices and inventory levels, and show that (i) firms do not always exploit hype, (ii) firms do not always increase the price of a successful product in the second period, (iii) firms may price out an unsuccessful product in the first period if the success probability is above a threshold, and (iv) such a threshold probability is decreasing in the first‐period market potential of the successful product. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 304–320, 2015     

Smart Power and Military Force: An Introduction

Abstract

Smart power is comprised of two elements: the quest for building society among states and between states and non-state actors; as well as the desire for cleaner forms of power projection. This special issue explores how states continue to fumble over achieving the optimum mix of hard and soft power across several country cases and themed articles. This set of contributions suggests that smart power is not unlike a ‘Swiss Army Knife’ analogy: multifunctional and challenging to choose the right combination of ideational and material tools.