Balancing a one‐way corridor capacity and safety‐oriented reliability: A stochastic optimization approach for metro train timetabling

In urban rail transit systems of large cities, the headway and following distance of successive trains have been compressed as much as possible to enhance the corridor capacity to satisfy extremely high passenger demand during peak hours. To prevent train collisions and ensure the safety of trains, a safe following distance of trains must be maintained. However, this requirement is subject to a series of complex factors, such as the uncertain train braking performance, train communication delay, and driver reaction time. In this paper, we propose a unified mathematical framework to analyze the safety‐oriented reliability of metro train timetables with different corridor capacities, that is, the train traffic density, and determine the most reliable train timetable for metro lines in an uncertain environment. By employing a space‐time network representation in the formulations, the reliability‐based train timetabling problem is formulated as a nonlinear stochastic programming model, in which we use 0‐1 variables to denote the time‐dependent velocity and position of all involved trains. Several reformulation techniques are developed to obtain an equivalent mixed integer programming model with quadratic constraints (MIQCP) that can be solved to optimality by some commercial solvers. To improve the computational efficiency of the MIQCP model, we develop a dual decomposition solution framework that decomposes the primal problem into several sets of subproblems by dualizing the coupling constraints across different samples. An exact dynamic programming combined with search space reduction strategies is also developed to solve the exact optimal solutions of these subproblems. Two sets of numerical experiments, which involve a relatively small‐scale case and a real‐world instance based on the operation data of the Beijing subway Changping Line are implemented to verify the effectiveness of the proposed approaches.     

Effect of microstructure on short pulse duration shock initiation of TATB and initial response mechanism

Micro-TATB particles with different sizes and 3D nanoporous TATB architectures with different specific surface areas were prepared through recrystallization to study short pulse duration shock initiation properties by electric gun technology. For micro-TATB, the initiation threshold significantly decreases with TATB average size ranging from 79.7 μm to 0.5 μm. For 3D nanoporous TATB architecture, the initiation threshold decreases and then increases with specific surface areas increased from 9.6 m²/g to 36.2 m²/g. The lowest initiation thresholds are obtained for the micro-TATB with average sizes of 1.3 μm and 0.5 μm, and 3D nanoporous TATB architecture with specific surface area of 22.4 m²/g. The shock initiation thresholds of micro-TATB and 3D nanoporous TATB architectures show significantly decreases with the porosity increased. The decomposition reaction and thermal conductivity properties were further investigated to understand the initial response mechanism. High porosity provides more collapse sites to generate high temperature for formation of hot spots. The low thermal conductivity and decomposition temperature could enhance the formation and ignition of the hot spots, and initial decomposition reaction of TATB. The effect of the decomposition temperature is higher than that of the thermal conductivity on the shock initiation properties. The enhanced decomposition reaction could promote energy release and transfer process from the ignition to the combustion. This work offers a new insight to understand the effects of microstructure on the shock initiation properties and the initial response mechanism of TATB.     

基于压力测量的发动机汽缸磨损寿命预测方法

对不同摩托小时的某型坦克发动机进行了实车检测试验,采用压力传感器测量了发动机汽缸压缩压力,分析了汽缸压缩压力随发动机使用时间的变化趋势。分析了汽缸套磨损的特点及对发动机使用寿命的影响。针对发动机汽缸磨损的非线性特点,建立了人工神经网络预测模型,实现了对坦克发动机汽缸使用寿命的预测。     

针对窄脉冲雷达测角的相位干涉仪仿真研究

以Matlab／simulink为工具，对相位干涉仪快速准确获取窄脉冲目标雷达的角信息问题进行了仿真研究。研究表明，相位干涉仪快速、准确获取窄脉冲目标雷达角信息的基本能力主要取决于鉴相器中低通滤波器截止频率的设计，并给出了截止频率的设计公式。此外，还对读取相关信息的时机和方法等问题进行了研究，给出了相应的解决方案。     

数据采集中脉冲丢失补偿算法

针对测试中遇到的脉冲丢失问题,采用脉冲边沿、脉冲到达时间和脉冲间隔等特征量,设计了快速进行脉冲丢失位置定位和补偿的算法。仿真结果表明,该算法能有效地解决脉冲丢失的问题,对脉冲敏感型的数据分析和故障诊断具有重要意义。     

考虑细观结构变化的原状Q3黄土变形和强度特性

为研究结构性对非饱和原状Q3黄土变形和强度特性的影响，做了12个非饱和原状Q3黄土的CT-三轴侧向卸荷试验。在试验剪切过程中，利用CT机对试样进行跟踪扫描，共得到168张CT图像。基于试验数据建立了细观结构参数，并利用该参数来反映非饱和原状Q3黄土的变形和强度特性，从而得到能反映细观结构性影响的非线性应力-应变关系以及摩尔-库伦强度公式。     

基于功率谱的舰船水压信号检测方法研究

为了有效地从风浪背景下检测舰船水压场信号,鉴于舰船水压场信号与海浪水压信号在频谱上的差异,采用求卓越频率下的功率谱的方法对信号进行检测,取窗宽20s,每次计算21个采样点,分别求取海浪水压场的仿真信号及不同波浪级别下海上某目标的水压场实测数据的功率谱进行信号检测,验证了方法的有效性。     

电磁脉冲武器对抗来袭目标可行性研究

针对电磁脉冲武器独特的毁伤机理,计算了杀伤覆盖区域和辐射到目标处的功率密度等作战能力指标,并以反舰导弹为例分析了强电磁脉冲的耦合途径,通过评估前后门耦合的电磁能量,在理论上论证了用电磁脉冲武器对抗来袭目标的可行性.     

某高炮火控系统弹道风与气压修正的研究

针对部队在某型高炮射击训练中,常常出现弹道气象诸元不进行装定或装定时换算错误的问题,本文简要介绍了弹道风偏差的内容及其对弹道的影响,重点分析了该火控系统对射击弹道风偏差量的修正、弹道气象诸元换算和装定问题,并利用C Builder软件对换算进行了实现,为进一步提高该火控系统的射击精度提供了理论依据和技术手段。     

双泵源电液舵机线谱噪声控制

采取变频调速控制策略的电液舵机可大幅降低操舵噪声，但系统线谱噪声明显且随工况变化而迁移，衰减难度大。基于此，结合泵源双冗余的电液舵机原理，仅改变原系统控制策略，提出基于辅助泵源合流的压力脉动控制措施。理论分析指出，两泵源转速一致，初始相位角为半个周期可衰减奇数次谐波。设计了主从同步控制策略，配置相应硬件，并应用于实际系统，实测相同操舵工况下可降低基脚结构振动总级3~5 dB，一阶线谱最大可衰减23 dB。