4G核心技术OFDM及MIMO原理     

董莉 《渭南师范学院学报》2006,21(5):25-28

正交频分调制(OFDM)是一种新型调制技术,特别适合在频率选择性多径衰落信道中高速传输数据.而M IMO技术能够在空间中产生独立的并行信道同时传输多路数据流,这样就在不增加系统带宽的情况下增加频谱效率.可以看出这两者的结合是一种必然的趋势,并会成为第四代移动通信的关键技术.  相似文献   

全集成化高可靠电视图象信号发生器的设计     

石英  王振伟 《衡阳师范学院学报》1990,(3)

这种新型电视图象信号发生器完全由集成电路构成。与通常的同类型仪器相比,该仪器性能稳定,可靠性高,无调整,体积小,价格低廉,很适合厂家成批生产,可广泛用于电视教学和家用电器的修理。  相似文献   

Credibility and Security of Weighing System for Large Structure Object     

章青  周延兴 《天津大学学报(英文版)》2006,12(2):92-95

The weighing system designed for large structure object is mainly composed of three parts. The part of hydraulic system is made up of hydraulic cylinders, high pressure hydraulic hoses and electric pumps; the part of computer controlling system comprises pressure sensors, displacement sensors, data acquisitions, RS 485 network and the computer controlling model; the part of loading system is composed of the fulcrum structure and the concrete girder. The measurement principle and composition of the weighing system are discussed in this paper. Credibility and security of the weighing system are fully considered during the design phase. The hydraulic system is controlled by pilot operated check valves in case of the sudden loss of system pressure. The states of all gauges and RS485 network are monitored by computer controlling system functioning in different modules. When the system is running incorrectly, it will be switched to manual mode and give alarm. The finite element method is employed to analyze fulcrum structure so that the system has enough intensity to be lifted. Hence the reliability of the whole system is enhanced.  相似文献   

高校仪器设备寿命周期与延长寿命周期探讨     

陈新春 《衡阳师范学院学报》1996,(6)

本文结合笔者在教学仪器设备管理和使用维修中的实践经验，就设备自身寿命周期受有形磨损和无形磨损而老化；设备的先进程度，科学技术与生产力的发展速度对设备寿命周期的影响，掌握使用设备时期的规律，提高购置设备的超前意识等进行了讨论。  相似文献   

动态定位中机动和粗差检测延迟的探讨     

宋迎春 李琼吴芋  谢雪梅 《娄底师专学报》2006,(6):1-4

动态定位数据处理中，判定运动载体何时开始机动，测量数据何时出现粗差是一个困难的问题。为了在实时动态定位中尽可能快地检测出运动载体机动和观测数据何时出现粗差，文中提出了一种对机动和粗差检测的新方法。该检测算法是基于机动和粗差检测延迟最小的准则。通过分析，对不同的显著水平和机动幅度存在一个最优窗口长度。  相似文献   

The stability of kindergarten teachers’ effectiveness: A generalizability study comparing the Framework For Teaching and the Classroom Assessment Scoring System     

Panayota Mantzicopoulos  Brian F. French  Helen Patrick  J. Samuel Watson  Inok Ahn 《Educational Assessment》2018,23(1):24-46

To meet recent accountability mandates, school districts are implementing assessment frameworks to document teachers’ effectiveness. Observational assessments play a key role in this process, albeit without compelling evidence of their psychometric rigor. Using a sample of kindergarten teachers, we employed Generalizability theory to investigate (across teachers, raters, and lessons) the stability of scores obtained with two different observation measures: The CLASS K-3 and the FFT. We conducted a series of Decision studies to document (for both measures’ constituent domains) the number of lessons per teacher and raters per lesson that would justify the use of observation scores for high stakes decisions. Acceptable, stable scores for individual-level decisions about teachers may generally require more raters and lessons than is typically used in practice (1–2 raters and fewer than 3 lessons). The considerable variability of observation-based scores raises concerns about either measure’s appropriateness for making individual or group decisions about teachers’ effectiveness.  相似文献   

CET写作对英语教学的作用     

张俊杰 《安阳师范学院学报》2001,(3):69-70

任何语言测试对语言教学都有反作用。本文围绕CET写作的效度和信度探讨了它对英语教学的反作用。  相似文献   

How to achieve accurate peer assessment for high value written assignments in a senior undergraduate course     

Daniel Jeffery  Krassimir Yankulov  Alison Crerar 《Assessment & Evaluation in Higher Education》2016,41(1):127-140

The psychometric measures of accuracy, reliability and validity of peer assessment are critical qualities for its use as a supplement to instructor grading. In this study, we seek to determine which factors related to peer review are the most influential on these psychometric measures, with a primary focus on the accuracy of peer assessment or how closely peer-given grades match those of an instructor. We examine and rank the correlations of accuracy, reliability and validity with 17 quantitative and qualitative variables for three senior undergraduate courses that used peer assessment on high value written assignments. Based on these analyses, we altered the single most significant variable of one of the courses. We demonstrate that the number of reviews completed per reviewer has the greatest influence on the accuracy of peer assessment out of all the factors analysed. Our calculations suggest that six reviews must be completed per reviewer to achieve peer assessment that is no different from the grading of an instructor. Effective training, previous experience and strong academic abilities in the reviewers may reduce this number.  相似文献   

水电站坝体基础结构施工过程及结构分析   总被引：1，自引：0，他引：1  

郭征红  徐伟 《福建工程学院学报》2004,2(1):56-60,84

依据现行水利电力工程规范规定的方法扣原则，对水电站坝体基础结构进行结构形式扣施工过程的方案设计，并对各方案作有限元结构应力及可靠度分析，以比较方案及选择坝体尺寸。  相似文献   

高校招生中使用发展性评价结果面临的问题     

雷新勇 《教育发展研究》2007,29(20):77-79

高校招生中使用发展性评价结果是必要的.但是,对发展性评价的使用还存在着其评价结果缺乏可比性,效度、信度不高,在现有高校招生条件下难以操作等问题.  相似文献