一种VDSL上行链路自适应功率回馈方案

上行链路功率回馈技术(UPBO：upstream power back-off)是VDSL(very high-speed digital subscriber lines)系统中的关键技术,它用于抵消同一电缆中短线对长线引起的严重的远端串扰(FEXT:far-end crosstalk)。文中从功率控制的角度分析了基于迭代注水的自适应UPBO方案,并进行了性能仿真分析。     

EPON系统物理层参数优化

EPON是一种新出现的接入网技术,针对EPON系统的特点,对原来IEEE802.3z链路模型进行了改进,并以其为参考对EPON系统进行了分析。目的是结合目前光器件水平,对EPON系统物理层参数进行优化,如传输距离与分光比等。     

一种基于罚因子的DASH调度算法

随着移动互联网的普及,基于DASH的流媒体传输协议的应用越来越广泛。如何在带宽波动较大的移动互联网环境中保证用户实现流媒体的流畅点播,提高用户的体验度是DASH调度算法最主要研究的问题。以提高用户体验度为出发点,结合带宽和缓存深度两方面因素,对带宽预测模型的置信度进行评价。在高置信度情况下,大胆地对网络带宽估计模型的模型参量进行调整;在低置信度情况下,以保护缓冲区深度为目的,谨慎地对模型参量进行调整。这种调整势必会对QoE造成相应的影响,该影响作为"罚因子"反馈回模型置信度的评价,以获得模型参数的动态最优解,得到一种较好的DASH调度算法。     

两步保费率下的Erlang(2)风险过程

本文研究了两步保费率下Erlang(2)风险过程,给出了Gerber-Shiu折现罚函数的两个微积分方程及其解或更新方程.在索赔额为指数分布条件下得到了两个与破产相关的量并计算出了相应的数值结果.     

Optimal initial production control period based on a quality growth model

The initial production phase of new products or the initial installation phase of new manufacturing facilities is often unstable because of inexperienced workers and many defective products. An initial production process control, in which the defects in design, production technologies and products are fully fixed and removed, is switched to a normal process control whenever it is ready for actual mass production. This paper discusses a method of deciding the optimal initial production control period, based on a quality growth model. It is determined by the number of products with the minimum expected total quality control cost. Finally a penalty cost due to unattainable loss to the quality goal is introduced in the quality control cost: the realized stabilization level of the initial production process control is lower than the original quality objective. Numerical illustrations of the optimal policy are also presented. Copyright © 1999 John Wiley & Sons, Ltd.     

A natural gas cash-out problem: A bilevel programming framework and a penalty function method

One of the many complex problems that arise from the transmission and marketing of natural gas is when a shipper draws a contract with a pipeline company to deliver a certain amount of gas among several points. What is actually delivered is often different from the amount that had been originally agreed upon. This phenomenon is called an imbalance. When an imbalance occurs, the pipeline penalizes the shipper by imposing a cash-out penalty policy. Since this penalty is a function of the operating daily imbalances, an important decision-making problem for the shippers is how to carry out their daily imbalances so as to minimize their incurred penalty. In this paper, we introduce the problem of minimizing the cash-out penalty costs from the point of view of a natural gas shipping party. We present a mixed integer bilevel linear programming model and discuss its underlying assumptions. To solve it efficiently, we reformulate it as a standard mathematical program and describe a penalty-function algorithm functions for its solution. The algorithm is well-founded and its convergence is proved. Results of numerical experiments support the algorithm’s robustness providing a valuable solution technique for this very important and complex problem in the natural gas market.     

基于鱼体回声图像的鱼类识别算法

以图像处理技术理论为前提,使用Matlab中的DIP(Digtal Image Process)工具箱和GUI(Graph User Interface)工具,对鱼体回声图像进行处理,匹配专家数据库,成功实现了对单体鱼的识别.介绍了对单体鱼的识别方法,详细阐述了鱼体回声图像的预处理方法、单体鱼的体态及长度参数的提取方法、通过建立专家数据库来实现目标识别的方法.引入了自适应图像窗的概念,提出了对鱼群的识别算法.     

无缺陷退货下三级供应链应对突发事件的协调研究

设想一个三级供应链,由生产商、批发商和零售商三个环节构成,生产商生产一种短生命周期产品逐级批发给零售商销售,零售商以零售价格将产品销售给消费者并以销售价格回收消费者的无缺陷退货;批发商和生产商逐级对相关商品进行回收,这些相关商品包括零售商从消费者手中回收的无缺陷退货以及销售季节结束后形成的剩余商品.零售商的销售努力不仅对产品的需求有影响,而且对消费者的退货率也产生影响.在探讨回馈与惩罚契约对三级供应链协调功能的基础上,分析了市场需求因突发事件而变化时回馈与惩罚契约对三级供应链产生的协调影响,结果表明:在突发事件下,基准的回馈与惩罚契约对三级供应链的协调功能失效.对此,设计了三级供应链在突发事件下的最优应对策略,并调整了原来的回馈与惩罚契约使其具有抗突发事件性.应用一个算例对比加以说明.     

聚合物熔体的非等温平板收缩流动的数值模拟

用有限元法模拟了Carreau流体在4：1平板收缩口模中的非等温挤出流动,采用3节点的三角形单元对速度、压力和温度进行等阶插值,运用特殊的罚函数处理流体的不可压缩条件,解决了压力场的数值振荡问题,并用改进的Newton迭代法对非线性方程进行求解,成功地计算了Carreau流体在平板收缩流动中的速度、压力、粘度以及应力的分布,同时得到温度场的分布,计算的应力分布与实验的结果及Renardy的分析结构相符。     

带有间断系数椭圆方程的加权间断Galerkin方法

本文应用间断Galerkin(DG)方法求解带有间断系数的二维椭圆方程.针对扩散系数间断的特点,我们构造一种新的加权对称内惩罚方法.证明了相应双线性形式的连续性和强制性,并给出收敛性证明.数值算例表明我们的DG方法对于求解强间断系数问题十分有效.