Header error control schemes for coping with upstream channel noise in the HFC network     

Chen Hui-fang  Xie Lei  Qiu Pei-liang 《浙江大学学报(A卷英文版)》2001,2(1):51-55

The Hybrid Fiber-Coax (HFC) network is being paid close attention to in recent years as a bi-directional broadband access network. To achieve seamless connection with the backbone network, and Asynchronous Transfer Mode (ATM) Network Network Interface (NNI) cell format is used as the basic transmission packet unit in the HFC system. As the transmission condition of the HFC system’s upstream channel is bad, two improved header error control (HEC) schemes, i. e. the improved HEC and the cell interleaving technique, are employed to guarantee the packet integrity. Theoretical analysis of the results showed that the improved HEC and the cell interleaving technique are applicable to isolated random errors and burst errors, respectively.  相似文献   

优美图的若干性质   总被引：2，自引：0，他引：2  

谢继国  张效贤  刘永平 《甘肃高师学报》2004,9(2):1-6

刻划了优美图的基本性质 ,给出了某些优美图的具体标号。  相似文献   

Novel high torque bearingless two-sided rotary ultrasonic motor   总被引：3，自引：0，他引：3  

LI Xia CHEN Wei-shan XIE Tao LIU Jun-kao 《浙江大学学报(A卷英文版)》2007,8(5):786-792

Applications are limited at present because the currently available ultrasonic motors (USMs) do not provide suffi-ciently high torque and power. The conventional travelling-wave USM needs the bearing to support, which required lubricant. To solve the above problem, a bearingless travelling-wave USM is designed. First, a novel structure of the two-sided USM consisting of a two-sided teeth stator and two disk-type rotors is designed. And the excitation principle of the two-sided travelling-wave USM is analyzed. Then, using ANSYS software, we set up the model of the stator to predict the excitation frequency and modal response of the stator. The shape of the vibration mode was obtained. Last, the load characteristics of the USM are measured using ex-perimental method. The maximum stall torque and the no-load speed were obtained. The results showed that the characteristics of the two-sided USM are better than those of the conventional one-sided USM.  相似文献   

Event triggering power sharing control for AC/DC microgrids based on P -F droop curve method     

Dazhong Ma  Qiuye Sun  Xiangpeng Xie  Xiaoyu Li 《Journal of The Franklin Institute》2019,356(3):1225-1246

The power sharing of AC/DC micro-grids is researched in this paper. The proposed strategy mainly include two parts: the primary power event triggering control with secondary control and an adaptive quasi sliding mode voltage control in inner-loop. Firstly, a event triggering power sharing control (ETPSC) based on $P?F$ droop curve is developed to regulate the voltage and frequency of AC and voltage of DC with the aim of the proportional power sharing between AC and DC micro-grids. The triggered threshold of ETPSC can be chosen to decide the transmitted power between AC and DC micro-grids. When the difference power between AC and DC micro-grids is less than the triggered threshold of power flow, there is no power sharing between AC and DC micro-grids, which can less the number of switching the power flow direction and the transmitted line power loss. The ETPSC has a great robust for the disturbances of load and improve the stability of the system. An adaptive quasi-sliding-mode control,which is implemented easily and flexibly with small computational burden and only based on input/output (I/O) measurement data but not the model any more, is used to control voltage in inner-loop. The effectiveness of the proposed control schemes is demonstrated by some numerical simulations and experimental results.  相似文献   

地方高校图书馆特色馆藏建设策略   总被引：12，自引：0，他引：12  

夏有根  谢惠 《情报探索》2007,(6):117-119

论述特色馆藏建设的重要意义，探讨了地方高校图书馆加强特色馆藏建设的途径和方法。  相似文献   

滦平试区水土流失及泥沙来源研究     

谢永生王恒俊吕惠明 《资源科学》1996,18(6):51-55

本文以实地考察与实测分析为据，对滦平试区水土流失分布、不同土地利用类型的水土流失量进行系统分析，并提出了整个燕山东段山区今后水土保持工作的重点。  相似文献   

中国彩电总装企业的技术学习     

谢伟 《科研管理》2001,22(3):53-61

本从产品和工艺技术的角度，总结了中国彩电总装企业的技术学习行为及其特点，指出了总装企业主要是学习了产品的整机设计能力和装配操作技能，导致了总装企业较窄的知识基础，因此，总装企业的“追赶”主要是专注于国内同质且可大批量生产产品的生产能力和国内市场份额的扩张，难以升级到高端和正在增长的差别化产品市场。因此，总装企业需要加强与国内供应商的后向联系，以创造更广和更多样化的知识基础，尤其在关键零部件和生产设备的生产和设计方面。  相似文献   

坐骨神经痛中医治疗初探     

谢晓娥 《西藏科技》2003,(6):48-49

中医认为原发性坐骨神经痛属于痹症范围，因风寒邪入侵，局部气滞血瘀，经络闭阻所致，本文就近年来坐内神经痛的治疗方法作一探讨。  相似文献   

隔姜灸加超短波治疗急性细菌性痢疾31例临床观察     

洛桑曲珍  谢挺杉 《西藏科技》2002,(1):58-58,60

笔者于1997～2000年间运用隔姜灸配合超短波,治疗急性细菌性痢疾31例,取得了较满意的疗效,现报告如下:  相似文献   

国产化作为技术学习过程：上海桑塔纳案例分析   总被引：4，自引：3，他引：4  

谢伟  吴贵生 《科研管理》1997,18(1):34-40

本文通过对上海桑塔纳的案例分析，总结了汽车工业技术引进过程的特点，有助于理解技术学习的过程和本质，尤其是政府在技术学习过程中的地位  相似文献