Integrated scheduling of loading and transportation with tractors and semitrailers separated

Motivated by some practical applications, we study a new integrated loading and transportation scheduling problem. Given a set of jobs, a single crane is available to load jobs, one by one, onto semitrailers with a given capacity. Loaded semitrailers are assigned to tractors for transportation tasks. Subject to limited resources (crane, semitrailers, and tractors), the problem is to determine (1) an assignment of jobs to semitrailers for loading tasks, (2) a sequence for the crane to load jobs onto semitrailers, (3) an assignment of loaded semitrailers to tractors for transportation tasks, and (4) a transportation schedule of assigned tractors such that the completion time of the last transportation task is minimized. We first formulate the problem as a mixed integer linear programming model (MILPM) and prove that the problem is strongly NP‐hard. Then, optimality properties are provided which are useful in establishing an improved MILPM and designing solution algorithms. We develop a constructive heuristic, two LP‐based heuristics, and a recovering beam search heuristic to solve this problem. An improved procedure for solutions by heuristics is also presented. Furthermore, two branch‐and‐bound (B&B) algorithms with two different lower bounds are developed to solve the problem to optimality. Finally, computational experiments using both real data and randomly generated data demonstrate that our heuristics are highly efficient and effective. In terms of computational time and the number of instances solved to optimality in a time limit, the B&B algorithms are better than solving the MILPM. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 416–433, 2015     

双圆阵模式空间二维解相干

提出一种相干信号二维波达方向(Direction of Arrival,DOA)估计算法——模式空间波达方向矩阵(Mode-Space DOA Matrix,MS-DOAM)法。算法基于双圆阵,利用模式空间转换将圆阵转换为虚拟双平行线阵,计算虚拟线阵阵元间的互相关信息,构造两个等效协方差矩阵,进而构造波达方向矩阵,对该波达方向矩阵特征分解,利用得到的特征值与特征矢量求得入射信号的仰角和方位角。算法无需二维搜索,实现估计参数自动配对。仿真结果表明,算法在低信噪比和短快拍条件下,估计误差低于虚拟空间平移算法。     

BDS/GPS双模自适应抗干扰接收机关键技术研究与设计

针对现代导航战对卫星导航接收机干扰对抗能力的要求,研究了BDS/GPS双模自适应抗干扰接收机的关键技术。在分析传统空时零陷技术的基础上,引入基于数字波束形成的自适应抗干扰技术,并使用惯性模块和历书进行卫星信号初始来波方向估计,显著增强了接收机的抗干扰能力。同时,提出了BDS/GPS双模多阵元天线耦合测量与校正技术,有效解决了双模天线设计难题。仿真测试表明:接收机使用数字波束形成技术后,总体抗干扰能力可达85dB,比单一使用空时零陷技术增加了8dB。     

低速平台随队干扰编队设计及过程分析

针对防空兵基地训练需求,设计了使用低速平台搭载干扰系统伴随高速战机实施随队干扰的编队方式,仿真分析了不同主瓣宽度雷达、不同平台速度下的随队干扰过程。结果表明,对于所设计的编队方式,存在某一速度取值范围使得全程随队过程得以实现;当平台速度低于实现全程随队干扰的取值范围时,存在最佳的初始进入距离以实现最大局部随队干扰过程。     

两路相互注入锁定Nd:YAG激光器

通过锁定多模块输出激光相位实现激光功率扩展的相干合成技术是获得高能高光束质量光源的有效途径.本文分析了相互注入锁定相干合成的机理及其对激光器相干性的影响,利用偏振元件将两路独立的Nd:YAG激光器关联起来,解决了耦合过程中的损耗问题,实现了两路激光器的相互注入锁定,获得了总功率4.4W的部分相干激光输出,长曝光结果表明远场光斑峰值功率密度提高了1.4倍,对利用相干合成技术实现高能固体激光器技术进行了初步探索.     

基于频谱分析的雷达信号分选新方法

相参性是现代雷达的普遍性质,利用雷达脉冲之间的相参性,提取相参特征参数,并运用于雷达信号分选,对降低当前信号分选中存在的“漏批”率具有重要的意义。本文在基于频谱分析的相参特征模型基础上,研究了基于最小二乘模板匹配误差的相参特征,并提出了具体应用中的改进措施。仿真结果表明,利用频谱主峰图像最小二乘模板匹配误差这一相参特征参数进行信号分选,可以有效地减少“漏批”率。     

主星带伴随分布式小卫星雷达系统的波束同步分析

波束同步是主星带伴随分布式小卫星雷达系统的同步问题之一,分析了主星带伴随分布式小卫星雷达系统的波束同步问题。根据主星带伴随分布式小卫星雷达系统的特点,结合小卫星天线俯仰向可扫描、姿态可调节,提出了三种波束指向同步方法;分析了分布式小卫星雷达系统的波束覆盖同步问题,分别建立了主星和伴随分布式小卫星的波束覆盖数学模型;仿真分析“干涉车轮”,结果不仅证明这些模型的正确性,同时发现波束指向同步方法2有较好的优越性。     

自由电子激光的粒子模拟

文中简单介绍了自由电子激光粒子模拟方法,用■维完全相对论性电磁模程序模拟了相对论电子束通过回旋磁场产生电磁辐射的过程,并作了理论解释;研究了纵向引导磁场对能量转换效率的影响。     

Responses of HFR-LWC beams under close-range blast loadings accompanying membrane action

The load-carrying capacities and failure patterns of reinforced concrete components can be significantly changed by membrane effects. However, limited work has been carried out to investigate the blast resistance of Hybrid Fiber Reinforced Lightweight Aggregate Concrete (HFR-LWC) members accompanying membrane action. This paper presents a theoretical approach to quantitatively depicting the membrane behavior and its contribution on the behavior of HFR-LWC beams under close-range blast loadings, and the suitability of the proposed model is validated by a series of field tests. An improved Single-Degree-of-Freedom (SDOF) model was employed to describe the dynamic responses of beam-like members under blast loadings accompanying membrane action, where the mass-load coefficient is determined according to the nonuniformly distributed load induced by close-range explosion, and the membrane action is characterized by an in-plane (longitudinal) force and a resisting moment. The elasto-plastic and recovery responses of HFR-LWC beams under the combined action of blast load and membrane force were analyzed by the promoted model. A specially built end-constrain clamp was developed to provide membrane action for the beam member when they are subjected to blast load simultaneously. It is demonstrated that the analytical displacement-time histories are in good agreement with experimental results before peak deflections and that the improved SDOF model is an acceptable tool for predicting the behavior of HFR-LWC beams under blast loadings accompanying membrane action.     

无衍射艾里光束的横向自加速特性

无衍射艾里光束的横向自加速特性使得光束在自由空间沿弯曲路径进行传输成为可能。利用一维傍轴波动方程对新型无衍射艾里光束的横向自加速特性进行了仿真研究。研究表明,当入射波长一定时,艾里光束的横向加速度大小与传播距离呈正比关系,而与任意横向尺度的大小呈反比关系。同时,利用波印廷矢量对艾里光束横向自加速的内在机理进行了研究。最后,利用通用型液晶空间光调制器对二维艾里光束的产生和横向自加速特性进行了实验研究,所得结果与仿真计算结果取得了较好的一致性。