National security,military spending and the business cycle

This paper develops a Dynamic Stochastic General Equilibrium model where national security is an argument in the agent’s utility function and the government chooses optimally the level of military spending to maximize social welfare. National defense depends on military expenditure and on the strategic environment reflecting a potential hostile external threat. We use aggregate data on consumption, investment, and military spending for the US economy to estimate the parameters of the model. Estimation results suggest that consumption and national defense are complements and that military spending variability is mainly explained by external threat shocks although it also depends on the macroeconomic conditions. We compute impulse response functions of the main macroeconomic variables to several shocks: a total factor productivity shock, a defense technology shock, and a strategic environment shock. Surprisingly, we find that the optimal response to an increase in the external threat (a worsening in the strategic environment) will rise output by reducing consumption and increasing investment.     

Fire truck relocation during major incidents

The effectiveness of a fire department is largely determined by its ability to respond to incidents in a timely manner. To do so, fire departments typically have fire stations spread evenly across the region, and dispatch the closest truck(s) whenever a new incident occurs. However, large gaps in coverage may arise in the case of a major incident that requires many nearby fire trucks over a long period of time, substantially increasing response times for emergencies that occur subsequently. We propose a heuristic for relocating idle trucks during a major incident in order to retain good coverage. This is done by solving a mathematical program that takes into account the location of the available fire trucks and the historic spatial distribution of incidents. This heuristic allows the user to balance the coverage and the number of truck movements. Using extensive simulation experiments we test the heuristic for the operations of the Fire Department of Amsterdam‐Amstelland, and compare it against three other benchmark strategies in a simulation fitted using 10 years of historical data. We demonstrate substantial improvement over the current relocation policy, and show that not relocating during major incidents may lead to a significant decrease in performance.     

Interdiction models for delaying adversarial attacks against critical information technology infrastructure

Information technology (IT) infrastructure relies on a globalized supply chain that is vulnerable to numerous risks from adversarial attacks. It is important to protect IT infrastructure from these dynamic, persistent risks by delaying adversarial exploits. In this paper, we propose max‐min interdiction models for critical infrastructure protection that prioritizes cost‐effective security mitigations to maximally delay adversarial attacks. We consider attacks originating from multiple adversaries, each of which aims to find a “critical path” through the attack surface to complete the corresponding attack as soon as possible. Decision‐makers can deploy mitigations to delay attack exploits, however, mitigation effectiveness is sometimes uncertain. We propose a stochastic model variant to address this uncertainty by incorporating random delay times. The proposed models can be reformulated as a nested max‐max problem using dualization. We propose a Lagrangian heuristic approach that decomposes the max‐max problem into a number of smaller subproblems, and updates upper and lower bounds to the original problem via subgradient optimization. We evaluate the perfect information solution value as an alternative method for updating the upper bound. Computational results demonstrate that the Lagrangian heuristic identifies near‐optimal solutions efficiently, which outperforms a general purpose mixed‐integer programming solver on medium and large instances.     

Attrition through a partially coordinated area defense

An area defense consists of several groups that act independently, i.e., do not communicate with each other. Each group has a fixed number of defenders and a controller that allocates these defenders optimally against the individual attackers comprising an attack. We analyze the effectiveness of this partially coordinated defense against a simultaneous attack of known size in which all attackers are considered to be equally lethal. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

Do Military Expenditures Crowd-out Health Expenditures? Evidence from around the World, 2000–2013

Abstract

The paper examines the relationship between health and military expenditures using pooled cross-sectional (197 countries) and time series (2000–2013) data. Simultaneous equation models were employed to estimate the relationship between an array of public sector expenditures in order to address potential endogeneity. Our empirical findings strongly support the crowding-out hypothesis whereby increased military expenditures reduce the capacity of government to direct expenditures to health expenditures. These findings were robust to alternative specifications explored in the sensitivity analyses. Compared with upper-middle-income countries, the crowding-out effect became more pronounced among lower-middle-income countries. Consequently, this study shows that increased military expenditures negatively impacts health expenditures, and therefore poses as an important risk factor for population health and individual well-being. Moreover, it is the poorest of nations that are most sensitive to the negative effects of increased military expenditures.     

新算法在划船和伪划船效应中的应用

划船效应补偿是高精度捷联惯导系统解算的重要环节。通过研究其误差特性,推导了新的通用划船效应补偿公式。同时提出了角振动环境中伪划船效应的存在,对伪划船效应的产生原因、表达方式以及对捷联惯导系统的影响进行了分析。对新的补偿算法在划船效应和伪划船效应下进行了仿真试验。     

舰载光电跟踪的船摇扰动复合补偿控制

针对船摇扰动引起的机械谐振和视轴不稳定的问题,舰载条件下通过安装多个陀螺来实现船摇扰动的复合补偿,在原有等效闭环系统中串入高通滤波器,消除谐振环节带来的影响。从仿真结果看,复合补偿控制具有良好船摇隔离效果,有利于高精度跟踪系统的实现。     

水中微气泡上浮过程的力学影响因子研究

从受力分析的角度,对气泡运动方程进行了推导,并对半径在40~500μm之间的微小气泡上浮过程进行了仿真计算。结果表明,当半径小于500μm、气泡上浮距离大于0.1 m时,可忽略加速过程对气泡上浮速度的影响。在此基础上,对气泡运动方程进行了详细分析,结果表明,阻力系数与粘滞系数是影响气泡上浮速度的主要因素,它们的取值与上浮速度成反比,并得出了Re≤150条件下的微气泡运动通用的阻力系数表达式。     

依据噪声能量变化提取目标运动信息的方法

在对被动噪声声纳接收的噪声能量随时间的变化规律分析的基础上,从理论上分析噪声能量的变化与目标运动参数关系,给出了其中所含目标运动信息的提取方法.