变速跳频通信抗跟踪干扰性能的研究

针对常规跳频通信抗跟踪干扰能力差的问题,分析跟踪干扰原理,提出变速跳频通信。建立数学模型,在干扰容限、压制比和追踪概率方面进行理论分析,分析变速跳频通信抗跟踪干扰对误码率的性能,并用MATLAB进行仿真验证。     

Strategic obfuscation of production capacities

Recent supply‐chain models that study competition among capacity‐constrained producers omit the possibility of producers strategically setting wholesale prices to create uncertainty with regards to (i.e., to obfuscate) their production capacities. To shed some light on this possibility, we study strategic obfuscation in a supply‐chain model comprised of two competing producers and a retailer, where one of the producers faces a privately‐known capacity constraint. We show that capacity obfuscation can strictly increase the obfuscating producer's profit, therefore, presenting a clear incentive for such practices. Moreover, we identify conditions under which both producers' profits increase. In effect, obfuscation enables producers to tacitly collude and charge higher wholesale prices by moderating competition between producers. The retailer, in contrast, suffers a loss in profit, raises retail prices, while overall channel profits decrease. We show that the extent of capacity obfuscation is limited by its cost and by a strategic retailer's incentive to facilitate a deterrence. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 244–267, 2014     

基于LVQ网络的高校科研能力评估

作为高校核心能力的科研能力,其高低已成为衡量一所高校综合实力的重要指标。如何准确高效的评价高校科研能力成为政府、企业和高校面临的一个十分重要的问题。影响高校科研能力的因素众多,本文选取11个典型指标,建立了基于LVQ的高校科研能力评估模型及算法。首先,介绍了LVQ网络;其次,建立了一种新的基于LVQ的高校科研能力评估模型及算法;最后,利用MATLAB R2009a编程实现了LVQ高校科研能力评估模型及算法。选取25所高校的科研能力数据用于仿真实验,其中20所高校数据作为训练集,其它5所作为测试集,该算法分类正确率为80%,达到了预期目标。仿真结果表明,该模型提高了高校科研能力评价的准确率,评价结果更加客观、公正,对高校科研能力评价具有一定的参考意义。     

Evergreening and operational risk under price competition

“Evergreening” is a strategy wherein an innovative pharmaceutical firm introduces an upgrade of its current product when the patent on this product expires. The upgrade is introduced with a new patent and is designed to counter competition from generic manufacturers that seek to imitate the firm's existing product. However, this process is fraught with uncertainty because the upgrade is subject to stringent guidelines and faces approval risk. Thus, an incumbent firm has to make an upfront production capacity investment without clarity on whether the upgrade will reach the market. This uncertainty may also affect the capacity investment of a competing manufacturer who introduces a generic version of the incumbent's existing product but whose market demand depends on the success or failure of the upgrade. We analyze a game where capacity investment occurs before uncertainty resolution and firms compete on prices thereafter. Capacity considerations that arise due to demand uncertainty introduce new factors into the evergreening decision. Equilibrium analysis reveals that the upgrade's estimated approval probability needs to exceed a threshold for the incumbent to invest in evergreening. This threshold for evergreening increases as the intensity of competition in the generic market increases. If evergreening is optimal, the incumbent's capacity investment is either decreasing or nonmonotonic with respect to low end market competition depending on whether the level of product improvement in the upgrade is low or high. If the entrant faces a capacity constraint, then the probability threshold for evergreening is higher than the case where the entrant is not capacity constrained. Finally, by incorporating the risk‐return trade‐off that the incumbent faces in terms of the level of product improvement versus the upgrade success probability, we can characterize policy for a regulator. We show that the introduction of capacity considerations may maximize market coverage and/or social surplus at incremental levels of product improvement in the upgrade. This is contrary to the prevalent view of regulators who seek to curtail evergreening involving incremental product improvement. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 71–89, 2016     

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     

气液比对液体中心式气液同轴离心喷嘴燃烧过程的影响

为了分析气液比对液体中心式气液同轴离心喷嘴燃烧过程的影响,针对一台采用液体中心式气液同轴离心喷嘴的燃气发生器在不同气液比下进行热试,并对试验结果进行深入分析。结果表明:随着气液比的增加,燃烧过程存在三种状态——稳定燃烧、稳定燃烧过渡到低频不稳定燃烧、低频不稳定燃烧。这种低频不稳定燃烧与供应系统的振荡无关,是由气液比增加造成三岔火焰远离喷注面板,当三岔火焰到达喷雾撞击点后火焰稳定性降低,使得火焰在回流区内前后振荡引起的。     

Improvise,adapt and fail to overcome? Capacity building,culture and exogenous change in Sierra Leone

Military capacity building (MCB) is as problematic as it is ubiquitous, with the British experience in Sierra Leone providing a rare example of ostensible success. This article critiques the dominant conceptualisation of MCB as purely a principal–agent (PA) problem, using military change scholarship to examine the impact of wartime British intervention on the Sierra Leonean armed forces. Here, indigenous military change was both externally driven and fundamentally adaptive in nature, allowing MCB to bypass some of the difficulties predicted by PA models. However, this adaptive approach nonetheless failed to reconcile Western military values with prevailing Sierra Leonean culture, complicating post-war stabilisation efforts.     

滑翔增程弹滑翔弹道优化设计分析

针对鸭式布局的滑翔增程弹,建立了滑翔增程弹滑翔弹道的模型,采用使滑翔弹道上每一点的升阻比最大的设计思想进行弹道优化设计,导出了俯仰舵偏角与平衡攻角的表达式,并对滑翔飞行弹道特性进行了仿真计算分析.仿真计算表明,滑翔弹道与常规弹道降弧段相比下降趋缓,增程效果显著.     

Unpacking the various meanings of redundancy: from refining the concept to military planning

The authors engage in the debate over waste in military force structure planning by rigorously deconstructing the concept of “redundancy.” First, a typology of redundancy is constructed that provides a common framework for identifying variety among redundant structures. These are labeled “true redundancy,” “expanded capacity,” “portfolio diversification,” and “mission overlap.” Further, a number of mechanisms are identified that produce these types of structures, and show the conditions under which planners may utilize redundant structure in the search for optimization. In sum, the article provides refined concepts for analysts and planners to identify when redundancy is deleterious or beneficial.     

Supercritical carbon dioxide as a new working medium for pneumatic launch: A theoretical study

Compared with the conventionally gaseous or liquid working media, the specific internal energy of supercritical carbon dioxide (SCD) is higher at the same temperature and pressure, and the critical temperature of carbon dioxide is close to room temperature, making SCD a potential new working medium for pneumatic launch. To analyze the feasibility of this conception, an analytical model of a pneumatic catapult is established on basis of the conservations of mass and energy. The model consists of a high-pressure chamber and a low-pressure chamber connected by multiple valves, and there is a movable piston in the low-pressure chamber that can push an aircraft to accelerate. The effects of the launch readiness state of SCD in the high-pressure chamber, the initial volume of the low-pressure chamber and the valve control on the movement of the aircraft are analyzed. It is found that there is a restrictive relation between the temperature and pressure of the launch readiness state of SCD, i.e., there is a maximum allowable launch readiness pressure when the launch readiness temperature is fixed. If this restrictive relation is not satisfied, the working medium in the low-pressure chamber will drop to its triple point within a few milliseconds, leading to a launch failure. Owing to this restrictive relation, there is an optimal launch readiness state of SCD with the highest working capacity for any allowable launch readiness temperature. The pressure of the low-pressure chamber will decrease significantly as the initial volume increases, leading to a decreased acceleration of the aircraft. The ac-celeration can be controlled below a critical value by a designed sequential blasting technique of multiple valves. The calculated results show that a 500 kg aircraft can be accelerated from 0 to 58 m/s in 0.9 s with 36 kg of carbon dioxide. This research provides a new technique for the controllable cold launch of an aircraft.