排除虚假交叉定位点的新方法

多站测向交叉定位法是无源定位方法中应用较多的一种,但该方法易产生大量虚假定位点。针对这个问题,提出了一种排除交叉定位中虚假点的新方法。该方法以两个观测站为主站,其他观测站为辅站,利用辅站数据对主站数据进行筛选及反馈从而快速排除两主站中的虚假点。仿真结果表明,该算法能够快速、准确地排除虚假定位点。     

舰船航渡过程中的松弛时间与航渡策略问题

针对舰船特点和任务要求,提出了舰船航渡中的松弛时间问题。在对问题分析的基础上,给出了松弛时间的定义并对其进行了建模,讨论了航渡失败的判断准则,给出了松弛时间的上下限以及航渡中实际的松弛时间的计算方法,并采用仿真的方法进行了典型航渡过程的松弛时间和成功概率的计算。在大量计算的基础上,初步探讨了航渡成功概率与各类航渡参数之间的关系,并对舰船最优航渡策略问题进行了初步分析,最后对于优化目标、计算初值、结果的表达方式等提出了一个可行的解决方案。     

基于磁记忆检测技术的即时报警功能设计与实现

根据金属磁记忆检测技术中缺陷判定依据的运算特点,为减少程序计算量、提高缺陷检测效率,改进了传统缺陷判定算法．在检测设备基本结构基础上增加了信号调理卡,并借助多功能采集卡的数字输出功能实现了缺陷检出时的即时报警,大幅提高了检测系统的工作效率．     

Dynamic necking of a near α titanium alloy at high strain rates:Experiments and modelling

The tensile behaviour of near α Ti3Al2.5 V alloy, conceived for applications in aerospace and automotive engineering, is characterized from quasi-static to high strain rates. The material is found to present noticeable strain rate sensitivity. The dynamic true strain rate in the necking cross-section reaches values up to ten times higher than the nominal strain rate. It is also observed that beyond necking the dynamic true stress-strain curves present limited rate dependence. The experimental results at different strain rates are used to determine a suitable constitutive model for finite element simulations of the dynamic tensile tests. The model predicts the experimentally macroscopic force-time response, true stress-strain response and effective strain rate evolution with good agreement.     

A melt-cast Duan-Zhang-Kim mesoscopic reaction rate model and experiment for shock initiation of melt-cast explosives

A melt-cast Duan-Zhang-Kim (DZK) mesoscopic reaction rate model is developed for the shock initiation of melt-cast explosives based on the pore collapse hot-spot ignition mechanism. A series of shock initiation experiments was performed for the Comp B melt-cast explosive to estimate effects of the loading pressure and the particle size of granular explosive component, and the mesoscopic model is validated against the experimental data. Further numerical simulations indicate that the initial density and formula proportion greatly affect the hot-spot ignition of melt-cast explosives.     

A critical look at the U.S. deceased‐donor organ procurement and utilization system

The U.S. system for procuring and utilizing deceased‐donor organs for transplantation has been studied and written about in many articles. The purpose of this paper is to examine the interactions between the elements that comprise this system, and point out improvement opportunities that may be affected through operations research/management techniques. The authors demonstrate the need for developing data‐driven and analytic tools. In fact, data is used to generate hypotheses and support claims throughout the paper. The paper also points out the need to fully leverage data that is available to researchers, and to seek data that is currently not deposited in a centralized archive.     

Traffic channeling under uncertain conversion rates on e-commerce platforms

Traffic is the lifeblood of every e-commerce platform. The question of how to channel traffic to merchants operating on a platform lies at the heart of platform management. We consider a platform on which two independent merchants sell their products. Merchants compete on inventory in the sense that some of the unmet demand at one merchant will spill over to the other. The platform channels traffic based on products' conversion rates to maximize the total sale on the platform. We show that traffic channeling plays three roles. First, it allows more efficient allocation of traffic; that is, the merchant with a high conversion rate is given a higher priority in receiving traffic. Second, it allows the platform to control demand spillover between the merchants to maximize total sales. The platform either facilitates or prevents demand spillover, depending on product substitutability. Third, traffic channeling intensifies competition between the merchants and hence increases the total inventory. More efficient allocation of traffic and the increase in inventory increase sales inequality between the merchants. In contrast, demand spillover decreases sales inequality. While the platform always benefits from traffic channeling, the merchants do not benefit when their products are moderately substitutable. Interestingly, when the two products are owned and sold by the same merchant, the opposite happens–traffic channeling always benefits the merchant but may hurt the platform. Our study provides a basis for informed discussions on how platforms should channel traffic in response to conversion rates, and how traffic channeling affects the welfare of merchants and platforms.