移动Ad Hoc网络中一种支持QoS的多址接入协议

基于随机竞争和冲突解决的思想,为多跳移动Ad Hoc网络提出了一种支持服务质量(QoS)的多址接入(QMA)协议.将业务负载划分为时延敏感的实时业务和非时延敏感的数据业务.按照该协议,节点在发送业务分组前利用预报突发进行竞争接入,节点按照业务分组时延情况确定预报突发的长度,所发预报突发能持续到最后的节点优先获得接入.同时,具有实时业务的节点可以按照其优先级在更早的竞争微时隙中开始发送预报突发,因而可以比发送数据业务的节点更优先接入信道.最后利用OPNET仿真评估了QMA协议的多址性能,通过与带冲突避免的载波侦听(CSMA/CA)协议比较表明,QMA协议可以提供较高的吞吐量和较低的消息丢失率,并能为实时业务提供较低的时延,从而实现了对多媒体业务的QoS支持.      

网格计算环境中的安全信任协商系统

网格技术促进了广域网络环境下的资源共享和协同工作.然而,在网格环境中,服务的提供方和请求方往往位于不同的安全域,如何为位于不同安全区域的陌生主体间动态地建立信任关系成为一项应用难题.基于信任管理基础设施,通过协作主体间信任证、访问控制策略的交互披露逐渐为各方建立信任关系,设计并实现了一个保护协商方隐私信息的安全信任协商系统.该系统采用一种基于属性的委托授权信任证、访问控制策略及一致性验证算法,实现策略的动态调整,从而生成满足访问控制策略的所有最小可满足信任证集,能够使理论上存在的信任关系得以自动建立.通过在CROWN平台中的应用,显示该系统能够满足网格应用中信任自动建立和敏感信息保护的需求.      

东航发展战略及对策建议

1997年东航在组织结构和经营机制等方面发生了根本性的变化：东航集团公司与东航股份公司进行了机构分立、东航股份公司股票在海外上市取得成功并即将发行A股，这标志着东航从此进入了一个新的发展阶段。本文在分析东航集团所面临的经营环境和自身条件的基础上，提出东航的若干战略发展思路以及所应采取的对策建议。一、东航面临环境：充满发展机遇、面临严峻挑战上海区域经济近几年的蓬勃发展，不仅使L海及其临近城市成为我国航空运输需求量增长最快的市场，为东航集团航空运输主业的发展提供了良好的发展机遇，而且也为东航集团其他行业…     

旅游目的地广告中的区域文化影响因素分析

旅游目的地广告是旅游业生存和发展的重要策略之一。旅游目的地广告自身发展规律和旅游者需求等决定了区域文化对其有重要影响。语言、宗教信仰等是区域文化影响旅游目的地广告活动的主要因素,在旅游目的地广告活动中要注意恰当地运用这些因素。     

对我国民机发展方针与策略的看法

预测了国内外市场民机销售的前景,提出了发展我国民用飞机的方针、策略及拟采取的措施。     

一种策略可配置的IMA系统故障管理方法

随着综合化模块化航空电子(IMA)系统的综合化程度增加,其故障发生概率及类型增多,且IMA系统在功能升级、集成过程中,其故障管理方式不断迭代、管理难度增加。提出一种可灵活策略、可配置的故障管理方法。方法基于IMA平台构建于分区OS上,参考ASAAC标准管理层级,提出预先配置故障管理策略及多级权限的管理机制,解决了传统故...     

Research of multi-path routing based on network coding in space information networks

A multi-path routing algorithm based on network coding is proposed for combating long propagation delay and high bit error rate of space information networks. On the basis of traditional multi-path routing, the algorithm uses a random linear network coding strategy to code data pack- ets. Code number is determined by the next hop link status and the number of current received packets sent by the upstream node together. The algorithm improves retransmission and cache mechanisms through using redundancy caused by network coding. Meanwhile, the algorithm also adopts the flow distribution strategy based on time delay to balance network load. Simulation results show that the proposed routing algorithm can effectively improve packet delivery rate, reduce packet delay, and enhance network performance.     

Configurationmodelofpartial repairablesparesunder batch ordering policy based on inventory state

Rational planning of spares configuration project is an effective approach to improve equipment availability as well as reduce life cycle cost （LCC）. With an analysis of various impacts on support system, the spares demand rate forecast model is constructed. According to systemic analysis method, spares support effectiveness evaluation indicators system is built, and then, initial spares configuration and optimization method is researched. To the issue of discarding and con-sumption for incomplete repairable items, its expected backorders function is approximated by Laplace demand distribution. Combining the （s-1, s） and （R, Q） inventory policy, the spares resup-ply model is established under the batch ordering policy based on inventory state, and the optimi-zation analysis flow for spares configuration is proposed. Through application on shipborne equipment spares configuration, the given scenarios are analyzed under two constraint targets：one is the support effectiveness, and the other is the spares cost. Analysis reveals that the result is consistent with practical regulation;therefore, the model＇s correctness, method＇s validity as well as optimization project＇s rationality are proved to a certain extent.     

Rescheduling of observing spacecraft using fuzzy neural network and ant colony algorithm

This paper aims at rescheduling of observing spacecraft imaging plans under uncertainties. Firstly, uncertainties in spacecraft observation scheduling are analyzed. Then, considering the uncertainties with fuzzy features, this paper proposes a fuzzy neural network and a hybrid rescheduling policy to deal with them. It then establishes a mathematical model and manages to solve the rescheduling problem by proposing an ant colony algorithm, which introduces an adaptive control mechanism and takes advantage of the information in an existing schedule. Finally, the above method is applied to solve the rescheduling problem of a certain type of earth-observing satellite. The computation of the example shows that the approach is feasible and effective in dealing with uncertainties in spacecraft observation scheduling. The approach designed here can be useful in solving the problem that the original schedule is contaminated by disturbances.     

浅析民用机场竞争战略的制定

<正>竞争战略是企业战略中的业务层次战略,主要是指为了获得市场竞争优势,以便在市场上处于比较有利的竞争地位,与竞争对手相比,获得更大市场份额和更好经济效益,所做的长远谋划和指导策略。美国著名管理大师彼得·德鲁克曾指出:"对企业而言,未来至关重要,经营战略使企业为明天而战。"随着经济全球化趋势的蔓延,技术的同源、产品的同质、信息的共享,企业间的竞争愈演愈烈,驱动企业发展更趋集中在竞争战略的高下及其手段的优