UC3875在超声电源功率控制系统中的应用

根据超声波发生器的功率控制系统原理 ,阐述了移相控制策略对超声波发生器输出电压波形的影响 ,介绍了移相控制专用芯片UC3875的电路结构和使用设计方法。     

提高托盘利用效率的重要手段——电子信息化管理

托盘能否有效运用对物流的畅通与否关系重大,这已经引起了国内外专家和学者们的重视,并就此制定了托盘电子信息化管理系统,旨在更合理地使用托盘,推进托盘一体化和共用系统的建立。而RFID技术在托盘的电子信息化管理的应用更将大大提高物流的效率与准确性,托盘电子信息化管理将成为今后托盘管理的趋势。     

两种基于弯曲损耗的光纤测试仪器原理及应用

光纤通信技术的飞速发展带动了光纤测试仪器的发展。主要对两种利用弯曲损耗对光纤进行检测的仪器——光纤识别仪、光纤对线器的原理、结构及其在光纤通信工程中的应用进行了阐述，两种仪器可以在不中断光纤通信的情况下对光纤进行检测，极大地降低了对光纤通信系统的影响，对光纤通信系统具有重要意义。     

电视新闻拍摄也需要美感

分析电视新闻拍摄美感的重要性和必要性,提出在实地拍摄过程中如何体现电视新闻的美感。     

有线电视系统工程的招标

针对有线电视系统工程建设的特点，依照《招标投标法》的规定和程序，对有线电视系统工程招标的种类、招标方式、招标工程必备的条件、标底的编制及审定、开标、评标和中标的原则进行详细介绍，对招标文件的编制进行具体说明。     

小井距开发现河油田低渗油藏可行性研究

认为注采井网井距大,水驱控制程度差,采收率偏低是影响胜利油田现河低渗透油藏开发的关键,通过井间密度与水驱控制程度和采收率的关系等分析,提出了现河低渗透油藏开发的合理的井网密度。     

水资源承载力及其研究

文章简要介绍了我国水资源情况,分析了我国水资源承载力与可持续发展的关系,并阐述了水资源承载力 研究的特点和方法。     

Optimal Control of the Primary Drying Stage of Freeze Drying of Solutions in Vials Using Variational Calculus

The problem of operating freeze drying of pharmaceutical products in vials placed in trays of a freeze dryer to remove free water (in frozen state) at a minimum time was formulated as an optimal control problem. Two different types of freeze dryer designs were considered. In type I freeze dryer design, upper and lower plate temperatures were controlled together, while in type II freeze dryer design, upper and lower plate temperatures were controlled independently. The heat input to the material being dried and the drying chamber pressure were considered as control variables. Constraints were placed on the system state variables by the melting and scorch temperatures during primary drying stage. Necessary conditions of optimality for the primary drying stage of freeze drying process in vials are derived and presented. Furthermore, an approach for constructing the optimal control policies that would minimize the drying time for the primary drying stage was given. In order to analyze optimal control policy for the primary drying stage of the freeze-drying process in vials, a rigorous multi-dimensional unsteady state mathematical model was used. The theoretical approach presented in this work was applied in the freeze drying of skim milk. Significant reductions in the drying times of primary drying stage of freeze drying process in vials were obtained, as compared to the drying times obtained from conventional operational policies.     

CSTN-LCD用铬版清洗效果的改善

利用铬版清洗机对CSTN-LCD用铬版进行清洗处理,分析了清洗过程中出现的铬层脱落现象,铬层脱落与轴向喷射压力和水平切力密切相关,通过调整转速和喷射压力探索了安全使用条件:在转速不超过1000r/min,喷射压力低于0.5×105Pa的情况下使用铬版清洗机进行清洗是相对安全的。同时采用预清洗处理的方法满足清洁要求,使换线时间由平均3h缩短到平均1h以内,年产能提高270000片。     

Scheduling Algorithms for Packet-Oriented MAC Protocols in Wireless Multimedia Systems

Future generation wireless multimediacommunications will require efficient Medium AccessControl (MAC) protocols able to guarantee suitable Qualityof Service (QoS) levels for different traffic classes whileachieving a high utilization of radio resources. This paperproposes a new scheduling technique to be adopted at the MAClevel in wireless access systems, named Dynamic Scheduling-Time DivisionDuplexing (DS-TDD), that efficiently managesvideo, voice, Web and background traffics. A theoretical approachis proposed in this paper to evaluate the DS-TDD performance withvoice and Web traffics. Simulation results have permitted tohighlight the following promising characteristics of the DS-TDDscheme: (i) a high capacity of real-time traffics isattained with a QoS insensitive to Web and background trafficloads; (ii) a high throughput can be guaranteed whilepreserving the QoS levels of the different traffic classes;(iii) heavier downlink traffic loads do not modify the QoSof uplink traffics. Finally, extensive comparisons with differentscheduling schemes proposed in the literature have permitted tohighlight the better performanceof DS-TDD.