Mathematical Analysis of Energy Efficiency in IEEE 802.11 DCF

The standardized IEEE ,802. II distributed coordination function （ DCF） provides a contention-based distributed channel access mechanism for mobile stations to share the wireless medium. However, when stations are mobile or portable units, power consumption becomes a primary issue since terminals are usually battery driven. This paper proposes an analytical model that calculates the energy efficiency of both the basic and the RTS/CTS access mechanisms of the IEEE 802. II protocol. The model is validated with simulation results using NS-2 simulation package. The effects of the network size, the average packet length, the initial contention window and maximum backoff stages on the energy efficiency of both access mechanisms are also investigated. Results show that the basic scheme has low energy efficiency at large packet length and large network size, and depends strongly on the number of stations and the backoff procedure parameters. Conversely, the RTS/CTS mechanism provides higher energy efficiency when the network size is large, and is more robust to variations in the backoff procedure parameters.     

地方高校师德建设存在的问题及对策

本文以大连海洋大学为例,分析了目前地方高校师德建设的现状,并对近年来学校师德建设的实践展开探究,旨在为地方院校建设具有鲜明特色师德文化和品牌化师资队伍提供参考.     

自适应有限元方法在凹角域椭圆问题上最佳误差估计

完整给出由‖·‖ L∞(Ω) 范数最佳误差估计推出的一种关于线性椭圆问题近似解的自适应有限元方法 .本方法对给定误差能自动剖分 ,且不需要关于精确解的先验信息 ,通过在凹角域详细分析此过程 ,证明该方法是有效的 .在实例中也得到了所期望的结果 .     

目标管理在高职院校素质教育中的应用研究

目标管理理论在企业界和相当一部分事业单位中得到广泛应用并已取得显著实效。近几年, 这一理论也逐步进入高职商专院校并在高职高专院校素质教育中取得初步成效。     

配对补助金计划:政府、高校、社会在高等教育投资中的新型关系

人力资本理论、公共产品理论、高等教育成本分担与补偿理论以及治理理论构成了高等教育投资的理论依据。在大学教育资助委员会资助的8所院校面临连续7年削减整体补助金的背景下,香港政府连续实施三轮配对补助金计划。政府、高校与社会由此在高等教育投资中构建了新型关系,即对于准公共产品性质的高等教育投资,政府不再一手包办院校财政而是对高校进行分权治理与行政指导、社会资本注入高教领域、高校一反传统"等、靠、要"的角色,在一推一拉形势下积极向社会运作筹款。     

广义正交矩阵的几个性质

推广了正交矩阵 ,并研究了广义正交矩阵在行列式、特征根、伴随矩阵等问题中的四个性质     

形式情绪--新诗的声情

从新诗否定形式要素的现象出发,在提出"声情"这一传统诗论概念的基础上,引入了"形式情绪"这一概念从心理学的角度入手分析形式情绪的自我赋形机制.     

冷战后西欧政党格局的变化及其影响

自 2 0世纪 80年代末以来 ,西欧政党格局发生一定变化 ,进一步向两极格局靠拢。政党格局的变化是由于冷战后冲击波、各国社会经济政治及选民队伍变化等一系列因素所致。西欧政党格局的变化将对未来西欧政治走向产生深刻影响。     

Study on pig growth hormone gene polymorphisms in western meat-type breeds and Chinese local breeds

Chinese Meishan and Jiangquhai pigs are two of the most prolific pigs in the world, but their growth rate is lower than that of Duroc, Landrace and Pietrain pigs. It is suggested that growth rate is regulated by growth hormone. The objective of the current study was to analyze the porcine growth hormone (pGH) gene polymorphisms based on the polymerase chain reaction restriction fragment-length polymorphism method (PCR-RFLP) for three western meat-type breeds (Duroc, Landrace and Pietrain) and two local Chinese pigs (Meishan and Jiangquhai). Five polymorphic restriction sites were detected with the ApaI, MspI, BspI and HhaI restriction enzymes in two amplified fragments (605 bp, -119 to +486; 506 bp, +206 to +711). Breed difference was found only in the 506 bp fragment. There was no difference in allelic frequencies of BspI and HhaI restriction sites among the five breeds (P>0.05). Landrace and Meishan pigs lacked allele G3 of MspI site. The allele G3 frequency of restriction MspI site of the 506 bp fragment in Pietrain pigs was higher than that in Duroc and Jianquhai pigs (P<0.001). For ApaI site, the Meishan pigs lacked allele G1; no difference was found in allelic frequencies among Pietrain, Duroc, Landrace and Jiangquhai pigs (P>0.05). This new and rapid PCR-RFLP typing method is an attractive tool for analysis of porcine growth hormone gene restriction sites. The differences in MspI and ApaI restriction sites may explain the growth difference between the foreign meat-type breeds above mentioned and local Chinese pigs.     

高校教学管理中的四大关系的探讨

本文结合实际简要阐述了高等学校教学管理工作要处理好的四大关系，力争为高校教育管理和教学提供一些可资借鉴的有益经验。