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   

“颖井《兰亭序》、《黄庭经》刻石”及拓本考     

张飞莺 《合肥教育学院学报》2004,21(4):67-71,79

晋代王羲之撰文并书写的《兰亭序》、《黄庭经》真迹早佚，后世所传皆乃当时摹拓各种副本。其中《兰亭序》除《定武刻本》为最早外，唐摹系列推《褚遂良临本》为第二，然《褚本》中又以《颖井思古斋本》为最佳。或云《颖本》乃宋米芾临褚翻刻，历代争议颇多。“颖井《兰亭序》、《黄庭经》刻石”系唐褚临本，于万历年问出于古井，后虽毁于兵燹，但尚有残块存世，辗转千年流传，现归藏安徽省博物馆。校之新旧拓片数种，可见该石之沧桑变化。  相似文献   

机械零部件表面硬度无损检测的研究     

韦江宇 《黑龙江科技信息》2007,(21):26

针对传统硬度测量方法的局限性,阐述了超声波、电涡流等无损检测手段进行机械零部件表面硬度测量的系统和原理,并对无损硬度检测方法的应用进行了简单介绍,最后得出无损检测表面硬度是优势。  相似文献   

OFDM技术及降低其峰均功率比的一种有效的方法     

关义波  邹传云  莫延飞 《中国科技信息》2005,2(19):35

OFDM是一种多载波调制技术,其特有的调制特性决定了它有较高的峰均功率比值。高峰均功率比信号会对实际放大器提出很高的线性要求,因此,它是限制OFDM技术实用化的主要障碍。目前虽有很多降低OFDM信号的峰均功率比PAPR的方案,但大多是以增加系统的复杂程度为代价的。本文提出了一种降低OFDM信号PAPR的方法,可以在不过分增加系统复杂性的基础上使其PAPR在很大程度上得到降低。  相似文献   

巴蜀文化之渊薮 中国教育之胜迹——四川大学图书馆馆藏“张之洞捐俸置书”     

党跃武  丁伟 《四川档案》2020,(1):55-59

光绪元年(1875年),四川省城尊经书院(以下简称尊经书院)在成都石犀寺正式落成。清代洋务派代表人物、时任四川学政张之洞是尊经书院的实际建议、造端、经营、规划者。1875年,为解决尊经阁藏书和生员学习用书的不足,张之洞用自己的俸禄,为尊经书院的生员购置大量图书,沿存至今,成为今日四川大学图书馆的重要馆藏——集档案、文物和文献于一体的"张之洞捐俸置书"。  相似文献   

Effect of a distal protection device on epicardial blood flow and myocardial perfusion in primary percutaneous coronary intervention   总被引：2，自引：0，他引：2  

Zhou BQ  Tahk SJ 《Journal of Zhejiang University. Science. B》2007,8(8):575-579

Objective: The beneficial effect of percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI) has been well established, but there is the problem of no-reflow phenomenon which is an adverse prognostic factor in primary PCI. In the present study the effect of a distal protection device (PercuSurge GuardWire; GW) on epicardial blood flow and myocardial perfusion was evaluated. Methods and Results: Patients with AMI were randomly divided into 2 groups, the GW and the control groups. The GW group included 52 patients with AMI who underwent primary PCI with GW protection and the control group included 60 patients who underwent primary PCI without GW protection. Epicardial blood flow in the infarct-related artery (IRA) and myocardial perfusion were evaluated according to the thrombolysis in myocardial infarction (TIMI) flow grade and the myocardial blush grade (MBG). We found TIMI score of 3 was obtained significantly more frequently in the GW group (96%) than in the control group (80%). The MBG score of 3 was obtained also significantly greater in the GW group (65%) than in the control group (33%). Conclusion: Primary PCI with GW protection can significantly improve epicardial blood flow and myocardial perfusion.  相似文献   

他自云中来     

朝烟 《中文自修》2007,(6):9-11

如果说缘分天注定,那王维与佛的缘分确是从呱呱坠地便结下了。笃信佛教的母亲给他起名“维”,字“摩诘”,取意于《维摩诘所说经》。母亲在他心中不仅播下了佛的种子,“持戒安禅、乐住山林”的她也深深影响了王维的思想、性灵与胸怀。千百年后,人们将他与诗仙李白、诗圣杜甫并称,号“诗佛”。  相似文献   

《新安志》志源考述     

肖建新 《安徽师范大学学报(人文社会科学版)》2007,35(1):70-75

罗愿的《新安志》是在南北朝以后地记、图经,尤其北宋大中祥符《新图经》的基础上修撰而成的。它继承地记、图经的地理记载的传统,又逐渐超越地记、图经的局限,特别是增扩历史文化的内容,使地方志不断完善,走向成熟。  相似文献   

最早提议建立黄埔军校的人     

学习 《历史学习》2007,(3):29-29

最早提出国民党要建立军事学校的人不是孙中山,而是共产国际来华进行联络工作的代表马林。马林,1921年初接运动会共产国际特使维经斯基到了中国。他在中国工作生活两年。这期间他奔走国共两党领导层之间,广泛地宣传共产国际关于在中国建立民主联合战线的主张。  相似文献   

“每经头条”：以深度报道体现舆论引领能力     

刘学东  易启江 《新闻战线》2023,(3):95-96

“每经头条”强调故事化表达,标题和文字通俗易懂;以短视频扩大受众覆盖范围,以杂志式海报、数据图表等包装方式传播财经事件。既为专业财经领域人士提供“价值阅读”,又为普通读者提供经济、金融和资本市场教育;既扩大了传播效果,也提升了舆论引领能力。  相似文献