BST组分对介电可调性的影响

从钛酸锶钡（BST）相变行为出发,指出在外加电场的作用下,氧八面体中心的Ti4＋偏离在零场中氧八面体的位置,可使介电常数降低,并讨论了组分对介电性的影响。结果表明,在居里点以上50-100 K的范围内具有介电可调性,并且越接近居里点可调性越强。     

浅析我国新阶段下的“三农”问题

三农(农民、农业、农村)在中国城市化、工业化、现代化过程中具有不可逾越的地位,有着不可低估的人口影响、空间影响、素质影响和政治影响。由于受经济、产业、制度的制约,出现了农民增长缓慢、农业发展动力不足、农村剩余劳动力过多等“三农”问题。新的国际、国内发展阶段又加剧了“三农”问题,使其成为影响我国经济持续健康发展的重要因素。“三农”问题的解决需要新的思路、新的方法和新的措施,这要求我们必须从以下几方面思考:大力发展小城镇,转移农村剩余劳动力;调整产业结构,提高农产品市场竞争力;大力发展教育,增加劳动力的人力资本存量;加大对“三农”的支持力度,创造良好的发展环境。     

Production‐inventory systems with imperfect advance demand information and updating

We consider a supplier with finite production capacity and stochastic production times. Customers provide advance demand information (ADI) to the supplier by announcing orders ahead of their due dates. However, this information is not perfect, and customers may request an order be fulfilled prior to or later than the expected due date. Customers update the status of their orders, but the time between consecutive updates is random. We formulate the production‐control problem as a continuous‐time Markov decision process and prove there is an optimal state‐dependent base‐stock policy, where the base‐stock levels depend upon the numbers of orders at various stages of update. In addition, we derive results on the sensitivity of the state‐dependent base‐stock levels to the number of orders in each stage of update. In a numerical study, we examine the benefit of ADI, and find that it is most valuable to the supplier when the time between updates is moderate. We also consider the impact of holding and backorder costs, numbers of updates, and the fraction of customers that provide ADI. In addition, we find that while ADI is always beneficial to the supplier, this may not be the case for the customers who provide the ADI. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

Inventory control in divergent supply chains with time‐based dispatching and shipment consolidation

This article analyses a divergent supply chain consisting of a central warehouse and N nonidentical retailers. The focus is on joint evaluation of inventory replenishment and shipment consolidation effects. A time‐based dispatching and shipment consolidation policy is used at the warehouse in conjunction with real‐time point‐of‐sale data and centralized inventory information. This represents a common situation, for example, in various types of vendor managed inventory systems. The main contribution is the derivation of an exact recursive procedure for determining the expected inventory holding and backorder costs for the system, under the assumption of Poisson demand. Two heuristics for determining near optimal shipment intervals are also presented. The results are applicable both for single‐item and multiitem systems. © 2011 Wiley Periodicals, Inc. Naval Research Logistics 58: 59–71, 2011     

A combination of Lagrangian relaxation and column generation for order batching in steelmaking and continuous‐casting production

This article considers the order batching problem in steelmaking and continuous‐casting production. The problem is to jointly specify the slabs needed to satisfy each customer order and group all the slabs of different customer orders into production batches. A novel mixed integer programming model is formulated for the problem. Through relaxing the order assignment constraints, a Lagrangian relaxation model is then obtained. By exploiting the relationship between Lagrangian relaxation and column generation, we develop a combined algorithm that contains nested double loops. At the inner loop, the subgradient method is applied for approximating the Lagrangian dual problem and pricing out columns of the master problem corresponding to the linear dual form of the Lagrangian dual problem. At the outer loop, column generation is employed to solve the master problem exactly and adjust Lagrangian multipliers. Computational experiments are carried out using real data collected from a large steel company, as well as on large‐scaled problem instances randomly generated. The results demonstrate that the combined algorithm can obtain tighter lower bound and higher quality solution within an acceptable computation time as compared to the conventional Lagrangian relaxation algorithm. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

载体角运动对旋转式惯导系统旋转调制效果的影响

为了提高惯性导航系统长时间导航精度,采用旋转调制技术将惯性器件常值误差在导航系中调制成周期变化的信号,抑制系统误差发散.基于惯性测量单元误差模型,阐述了旋转调制技术的基本原理.理论分析了载体角运动对旋转调制效果的影响,推导了载体水平角运动下导航系中等效陀螺误差方程.进行了仿真和试验.理论分析、仿真和试验结果表明:载体水...     

复杂波形反数字储频干扰思考

阐述了数字射频存储器的基本结构,以及干扰的优点和局限性,从设计复杂波形进行反数字储频干扰研究,对阶段相位扰动LFM信号、串并联信号、脉内非线性调频脉间相位编码信号进行了分析。这3种复杂信号能够造成干扰信号和雷达信号失配,弱化干扰和回波的相干度,能够区分出干扰信号和回波信号,达到反干扰的效果,为反数字储频干扰的研究提供理论依据。     

二相编码雷达前沿复制干扰的能量效率分析

针对提高干扰的能量利用效率提供一些理论和技术问题,介绍了前沿复制干扰的产生背景。对二相编码雷达、灵巧噪声干扰和前沿复制干扰的基本成分通过匹配滤波器后的输出信号脉冲峰值进行了分析。以在匹配滤波器输出端产生相同数量和相同幅度大小的脉冲为能量利用效率比较基准,给出了这两种干扰方式各自所需的干扰信号能量的计算公式,并进行了典型条件下,这两种干扰方式所需干扰信号能量的数值计算;在一般情况下,对这两种干扰方式的能量利用效率进行了比较。指出若前沿波形宽度为雷达发射信号宽度的1/n,则前沿复制干扰所需能量为灵巧噪声干扰所需能量的n倍,前沿复制干扰的能量利用效率仅为灵巧噪声干扰的能量利用效率的1/n。     

m序列二相编码雷达灵巧噪声干扰研究

针对前沿复制干扰能量利用效率低的问题,提出了利用前沿波形,通过预测,超前获取雷达信号完整波形,进而实施灵巧噪声干扰的思路。对于采用由n级移位寄存器产生的m序列的二相编码雷达,给出了利用获得的前2n个码元,通过解n元线性方程组,预测获得完整m序列的方法。进一步,针对该线性方程组的生成特点,提出了一种快速算法。利用该快速算法,可以将预测的计算工作量平均分配到从获得m序列的第n＋1个码元到获得第2n个码元的各个节拍中去,使得一旦获得m序列的第2n个码元,就能够立刻得到m序列的所有反馈系数,获取雷达的当前发射信号的完整波形,并以最短的延迟实施针对性的灵巧噪声干扰。     

一种基于循环谱的数字信号调制识别方法

文章基于循环平稳信号处理理论,利用数字通信信号的循环谱特征的不同提出四个特征参数,用于信号调制识别。提取的参数较少,计算量较高阶循环累积量小。给出了三类信号调制方式自动识别算法的实现流程,该识别算法以统计理论为基础,不要求实现载波同步。仿真结果表明,在信噪比RSN≥5 dB时,算法的平均识别成功率>96%。