高超声速风洞进气道流量系数测量精度影响因素研究

进气道是飞行器动力装置的重要组成部分,准确测量进气道流量系数是进气道风洞试验的重要内容。对来流马赫数Ma=4.5,5.0和6.0状态下皮托管进气道开展流量系数测量研究,通过对比理论值和实测值,获取各状态流量系数修正系数。试验结果表明,随着来流马赫数增加,进气道流量系数与理论值偏差较明显,并逐渐增大。超声速风洞试验通常认为测量截面总温与来流总温相等,通过对测量截面总温与来流总温偏差以及测量截面流场畸变情况的分析,判断测量偏差主要是由测量截面总温等于来流总温的假设导致的。在高超声速风洞试验中,由于模型壁面热交换的存在,测量截面总温低于来流总温,进气道流量系数测量时需要进行总温修正,以提高流量测量精度。      

Exploring International Investment Through a Classroom Portfolio Simulation Project

A rapid integration of financial markets has prevailed during the last three decades. Investors are able to diversify investment beyond national markets to mitigate return volatility of a “pure domestic portfolio.” This article discusses a simulation project through which students learn the role of international investment by managing their own portfolios. The article explains the project's investment ground rule, trading requirement, and grading rubric. The students are required to examine many important factors in international business such as currency risks and regional policies. The structure of this project can also be applied to a course involving student-managed investment funds.     

Operational planning of vehicles for rescue and relief operations considering the unavailability of the relocated vehicles

Rapid urbanization has led to increasing fire incidents and false alarms, increasing the response time of fire departments. When a call arrives, the current technology deploys and relocates the vehicles based on their immediate impact on the system's preparedness. However, the unavailability of the relocated vehicles is often ignored during the relocation, thus the system's preparedness is overestimated. This paper presents a novel mixed-integer programming (MIP) model developed for the relocation and deployment of emergency/fire vehicles. The proposed model incorporates the unavailability element, and estimates system preparedness for future incidents more accurately than current models. To confirm the efficiency of the proposed approach, the required simulations were conducted in Mashhad, Iran. The results demonstrated the ability of the proposed model to improve the performance of the fire department in several performance metrics. We also provide sensitivity analysis over the critical parameters to demonstrate the robustness of the model.     

Indicative bidding: An experimental analysis

Indicative bidding is a practice commonly used in sales of complex and very expensive assets. Theoretical analysis shows that efficient entry is not guaranteed under indicative bidding, since there is no equilibrium in which more qualified bidders are more likely to be selected for the final sale. Furthermore, there exist alternative bid procedures that, in theory at least, guarantee 100% efficiency and higher revenue for the seller. We employ experiments to compare actual performance between indicative bidding and one of these alternative procedures. The data shows that indicative bidding performs as well as the alternative procedure in terms of entry efficiency, while having other characteristics that favor it over the alternative procedure. Our results provide an explanation for the widespread use of indicative bidding despite the potential problem identified in the equilibrium analysis.     

RSB-CWS算法解决CVRP问题

RSB-CWS算法结合了蒙特卡洛模拟和CWS节省算法,利用蒙特卡洛模拟对CWS算法节省列表中顾客对间的边进行模拟,模拟过程中采用基于类几何分布的直接抽样方法进行路径采样。对模拟得到的边序列应用CWS算法,所得解的质量能达到或者优于当前最优解.与其他CVRP问题算法相比具有高效、高质量的特点,且可以解决规模较大的CVRP问题。     

企业投资效率演进与中国总产出波动

本文将企业投资效率的变动过程引入包含名义和实际刚性等多种结构特征的新凯恩斯主义宏观模型,并用贝叶斯极大似然方法估计了模型的结构参数。边际数据密度比较结果显示,刚性价格-工资模型能够较好的解释实际数据。同时,我们还就企业投资效率冲击对实际总产出波动的解释力和历史贡献进行了评估,波动性分解的结果说明投资效率冲击对产出波动具有30%以上的解释力,是所有冲击中贡献最大的。历史分解和反事实模拟的结果显示投资效率是动态演化的,在本届政府的两个任期内,投资效率呈现总体改善趋势,相对于十五计划时期,十一五计划时期的投资效率更稳定、效率水平也更高。投资效率改善对2006年后产出增长有显著拉动作用,需要强调的是,如果没有投资效率改善所形成的产出拉动,2008年金融危机所导致的经济衰退要比实际情形严重很多倍。     

引入土地流转因素的新型农村社会养老保险基金预测

本文以政策外部性关联与协同效应为切入点,通过陕西省西安市新农保试点区县农民问卷调查,对引入土地流转因素的新型农村社会养老保险基金预测进行精算建模和政策仿真研究。结果表明：土地流转因素对新农保参保率、缴费率具有显著影响,基金收支呈现由盈余转向缺口、并逐年扩大的趋势,基金、制度存在双重失衡风险。通过关键制度因素的单一、组合调整结果分析对比,提出促进土地流转与新农保制度良性融合与可持续发展的对策建议。     

基于多标度分形理论的金融资产收益非对称性测度方法研究

基于多标度分形理论,提出了一种新的更适用于实际金融资产收益数据的非对称性测度方法——两阶段非对称性检验法（Two-step asymmetry testing,TAT）,并运用Monte Carlo模拟考察了其与传统的偏度系数检验法的非对称性判定结论差异。实证结果表明：总体来讲,本文提出的两阶段非对称性检验法在常用检验水平下取得了较偏度系数法更为准确的金融资产收益非对称性判定结论,且两阶段非对称性检验法较偏度系数法更适用于具有非独立、非正态特性数据的非对称性检验。     

基于共同冲击和异质风险叠加传导的风险传染研究——来自中国上市银行网络的传染模拟

本文将银行系统遭遇外部共同冲击作为研究起点,建立了一个共同冲击和异质风险交互传导与放大的简化模型,冲击的传导包括“原始冲击”、“增量冲击”和“违约冲击”三个风险传染阶段。基于2018年我国15家上市银行的股票收益率和年报数据、2006年至2018年的银行评级数据,本文构建了贝叶斯分层图模型和银行间拆借矩阵,并利用蒙特卡洛模拟测度不同触发银行所引发的系统性风险损失、单个银行的系统性风险杠杆能力(文中定义为“传染乘数”指标)以及政府监管介入的效果。模拟结果显示:共同冲击损失远大于异质风险损失;规模和网络关联性是决定传染乘数的重要因素,且当规模因素不突出时,网络关联性对传染乘数的决定作用相对更强,极容易出现小规模、高关联性银行具有较高的传染乘数;当银行风险资产损失率在10%至25%之间时,造成系统性风险损失的杠杆能力普遍增强;政府监管介入能较好地降低系统性风险。本研究的相关结论为系统性风险的监管设计提供经验证据和参考。     

银行排队系统服务效率问题研究

银行排长队现象是困扰银行和客户的难题,其实质是排队系统的效率问题。叫号机变多队一多服务台系统为单队一多服务台系统,改变了排队系统模型。本文运用蒙特卡罗仿真方法对两种排队系统模型进行比较,发现叫号机确实可以有效提升银行服务系统的效率。