A group of orthogonal frequency carriers are used in ofdm system to improve the using rate of spectrum . if the orthogonal character can be held and ignore the inter - channel interference ( ici ) , the symbol error character of ofdm depend on the modulate of source codes . this dissertation propose the theoretic formula of ofdm - qam and ofdm - psk in this precondition 为了提高频谱利用率, ofdm系统使用了一组正交的子载波来传输信号,若能保证各子载波间的正交性不被破坏、不考虑信道间干扰( ici ) ,则ofdm系统的误码性能由信元调制方案的误码性能决定,文中推导了该情况下ofdm - qam和ofdm - psk的理论误码率公式。
In this paper i calculate the reasonable possession quantity of port handling machineries with chance - constrained linear programming . first in the paper is the background and meaning of this research ; then analysis present situation of port machinery management both in practice and theory ; in chapter 3 , i qualitatively discusses characters influencing machinery quantity , which include lifting ton , intact rate and using rate , age of machinery , machinery purchase and working cost and so on . in chapter 4 , i take the influencing characters to mathematic model of chance - constrained linear programming , aiming to maintain the need of production and reduce machinery cost 文章首先介绍了选题的背景、意义以及主要工作;第2章介绍了港口机械管理在港口企业管理中的地位与作用,以及我国港口机械设备管理与配置现状,并简要介绍目前港机合理拥有量的理论研究方法;第3章从技术与经济角度定性分析了各种因素对港机拥有量的影响,其中主要包括机械起运量、完好率与利用率、机械设备役龄、购置与营运成本等;第4章将各种影响因素引入模犁,提出以完成生产任务、机械成本最低为目标,应用随机线性规划模型计算港口流动机械合理拥有量的方法;第5章以大连港大港区为例对模型进行应用,选择四种型号叉车为研究对象,对其历史经济与技术数据进行统计分析,其中重点对随机变量单位台时维修费用进行了正态分布拟合。
Lengthen working hours to work overtime at will , it is health of body and mind of serious effect laborer above all ; the 2nd cause excessive hair to work overtime salary , reduce national finance income ; the 3rd reduce business economic benefits , go against economic system to make reform ; the 4th , execute extensively work overtime , also go against improvement business management ; the 5th , go against when improving skill , use rate and improve labor productivity 随意延长工作时间加班加点,首先是严重影响劳动者身心健康;第二造成滥发加班加点工资,减少国家财政收入;第三降低企业经济效益,不利于经济体制改革;第四,广泛实行加班加点,也不利于改善企业治理;第五,不利于提高工时利用率以及提高劳动生产率。
Measures should be taken to improve the economic compensation system for paid use of the natural resources and the renewal of resources , enhance the comprehensive use rate of resources and economic profits , stop the destructive exploitation of natural resources , alleviate the controversy between the explosive population , the economic growth and the limitation of the resources 完善自然资源有偿使用和资源更新的经济补偿制度,提高资源综合利用率和经济效益,遏制资源破坏性开发,缓解人口和经济增长同资源有限性之间的矛盾。
Weed control could be achieved with very low use rate herbicides ( benbrook , 2001a , b ) , reducing the volume of chemicals used for weed management to levels below that currently used in non - glyphosate hrcs or with grcs . if this were more economical and efficacious , farmers would probably adopt such a strategy 用很少的除草剂即可达到控制杂草的效果,并且可减少杂草管理阶段化学药品的使用量,使其低于目前非草甘膦除草剂抗性作物的化学药品用量,或者低于耐草甘膦作物的化学药品用量.如果这种作法更经济有效的话,这种技术就可能被农民采纳