Mathematical Analysis of Energy Efficiency in IEEE 802.11 DCF     

高波杨宇航  马惠业 《天津大学学报(英文版)》2005,11(5):332-337

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.  相似文献   

对"效率优先、兼顾公平"分配原则的思考     

肖萍 《商丘师范学院学报》2004,20(6):121-122

效率与公平是社会经济发展的两个重要目标，社会主义的本质是效率与公平的内在统一。市场经济条件下“效率优先、兼顾公平”的分配原则有其内在统一性和客观必然性，坚持这一原则是社会主义初级阶段的现实选择。  相似文献   

基于多元线性回归分析方法的物流流通水平研究          下载免费PDF全文

潘新宇  薛洋 《唐山学院学报》2016,29(6):72-77

根据2013年全国31个省市的物流水平相关指标,分别以经营单位所在地分的进出口总额、按境内目的地和货源地分的商品进出口总额作为因变量对物流流通水平进行线性回归分析,得到了多元线性回归模型,由此找出了流通水平的影响因素,并有针对性地提出了对策建议。  相似文献   

带电导体静电场等值面边值问题的边界积分方程     

肖志锋 《杨凌职业技术学院学报》2002,(1)

利用强极值原理将带电导体静电场内、外等值面边值问题化为几个常规的椭圆型Dirichlet边值问题,并建立它们相应的第一类Fredholm边界积分方程,由这些方程解的线性组合可构成原问题的解。  相似文献   

Leveraging information and communication technologies (ICT) to enhance education equity,quality, and efficiency: case studies of Bangladesh and Nepal     

Cher Ping Lim  Sungsup Ra  Brian Chin  Tianchong Wang 《Educational Media International》2020,57(2):87-111

ABSTRACT

Information and Communication Technologies (ICT) have had significant impacts on many sectors in today’s knowledge economy. In developing and emerging countries, ICT have enhanced equity, quality, and efficiency in the education sector. However, the adoption of ICT in the South Asian countries’ education sector has not been at scale and its impacts have been limited. There are several gaps and issues that are hindering the wider adoption of ICT and limiting its impacts in the education sector. Through the case studies of the adoption of ICT for education in Bangladesh and Nepal, this paper examines the gaps and issues to be addressed in order to better leverage ICT to enhance education equity, quality, and efficiency. This discussion is guided by the ICT in the education framework that has been developed by the authors, and could provide insights into the state of ICT in education and offer strategies to better leverage ICT for the education sector of other countries in South Asia and the region.  相似文献   

提高大型贵重仪器设备使用效益的探讨   总被引：3，自引：0，他引：3  

陈达银 《实验室研究与探索》2004,23(6):83-85

如何提高大型贵重仪器设备的使用效益是高校仪器设备管理工作中面临的一个重要问题。文章结合具体实践探讨了采用经济手段,引入开放、竞争、服务新机制,通过实施有偿占用制、有偿使用制、开放基金补贴制和信息化管理等方法,提高大型贵重仪器设备使用效益的途径。  相似文献   

反垄断法律中的一个经济学谬误——关于禁止低于成本竞争的解析     

熊毅 《成都师专学报》2007,26(4):47-50

很多国家都将低于成本竞争行为归结于垄断,并通过法律加以禁止,然而如果我们运用经济理论从立法依据的科学性和法律实施的操作性分析,可以清楚地看出这一法律规定的无效性,这一分析过程和结果可以给我们的反垄断立法提供一些有价值的参考。  相似文献   

论科技期刊编辑的时效意识     

曾志红  王玉燕 《韩山师范学院学报》2007,28(2):101-104

发文周期过长是目前我国科技期刊界一个普遍存在的问题,增强编辑的时效意识是解决此问题的有效途径。科技期刊编辑的时效意识是时间意识和效率意识的有机统一,二者相辅相成,忽视任一方面都不会取得最佳效果。在工作过程中,编辑主体不但要牢固树立时效意识,而且还要注意克服短时效意识及长时效意识带来的不利影响。  相似文献   

Measurement of conversion efficiency of soft X-ray from 0.35μm laser-irradiated aluminum planar targets     

Shu-xi Ren  Hong-liang Ma Ph. D.  Rong-qing Yi  Shen-ye Liu 《上海大学学报(英文版)》2006,10(3):224-227

Conversion efficiency of soft X-ray from 0.35 μm pulse laser-irradiated aluminium planar target at laser intensities 10¹³–10¹⁵ W/cm² on the Xingguang-II facility (laser energy 5–90 J, focal spot ⊃ Ф 200 μm full width of half maximun (FWHM) 400–800 ps) was measured. A simple model was given to explain soft X-ray conversion efficiency. In this model, because of the heat conduction from the laser-heated spot, the conversion was very small at lower irradiance limit, while at higher limit it was bounded by the energy lost in blow off plasma. Consequently, at the laser intensity around 2×10¹⁴ W/cm², the X-ray conversion efficiency reaches a maximum. Project suppoted by Shanghai Leading Academic Discipline Foundation (Grant No. T0104), and Science Foundation of Shanghai Municipal Commission of Education (Grant No. 214680)  相似文献   

效率再造--报业集团做强之策略分析     

雷鸣 《平原大学学报》2006,23(2):14-16

我国报业集团化发展至今已经9个年头,报业集团的数量也已增加到目前的41家。由于报业的集团化之路缺乏必要的企业化铺垫,都或多或少地受到政治力量的推动,因此,在一定时段内各子报子刊会存在貌合神离、各自为战的现象,很可能导致“内耗”,造成“规模不经济”。因此,只有将子报子刊的资源有效整合,才能弥补报业集团浮躁发展带来的危险,才能真正实现经济学意义上的“规模经济”。  相似文献