龙门刨床工作台电气传动系统的改造     

耿梅芳 《科技广场》2011,(9)

本文阐述了运用西门子6RA70全数字直流调速系统和三菱FX2N-80MR型PLC对龙门刨床工作台电气传动系统进行改造,对6RA70全数字直流调速系统的调试运行作详细介绍。  相似文献   

IGBT电焊机的稳定性设计     

孙英 《喀什师范学院学报》2013,(6):34-35

介绍了IGBT模块在电焊机中的应用以及IGBT电焊机的众多优点和缺点,指出了IGBT电焊机存在的安全隐患;在此基础上,从电压保护、电流保护、吸收电路以及热保护等方面论述了电源中IGBT模块必要的典型保护方法.  相似文献   

开关电源中驱动电路的设计方法     

郑耀添 《内江科技》2007,28(3):94-96

开关电源一般都采用脉冲宽度调制(PWM)技术,其特点是频率高、效率高、功率密度高、可靠性高.本文着重研究了几种驱动电路的设计方法,通过对这几种驱动电路的设计和研究,为设计性能更加出色的PWM型开关电源提供理论基础.  相似文献   

基于ANSYS的非对偶蜗轮蜗杆不同啮合位置有限元分析     

王汝青  陈兴燕  卢利 《科技广场》2012,(5):6-9

本文针对蜗杆蜗轮传动装置在使用过程中出现的非对偶蜗轮蜗杆严重失效问题,使用SolidWorks对非对偶蜗轮蜗杆建模,利用ANSYSWorkbench对非对偶蜗轮蜗杆的啮合进行静力学有限元分析,计算出轮齿在不同啮合位置的等效应力并对计算结果作了相应分析。为设计非对偶蜗轮蜗杆提供理论依据。  相似文献   

Ethnic identity: Myth and reality in Western Canada     

J. Frideres  S. Goldenberg 《Int J Intercult Relat》1982,6(2):137-151

The paper analyzes eleven research projects which have focused on the issue of ethnic identity. Each study addresses the question of how important ethnicity is to the individual. The results suggest that ethnicity, as measured in the present studies, is of little importance to Canadians. Ethnicity, however, should be viewed as an adaptive response to the conditions governing the context for acquisition of scarce and desired goods! What is clear is that assertions of the universal and constant import of ethnicity to Canadians are not true.  相似文献   

Locus of control, persistence, and use of contingency information in physically abused children     

Bonnie B. Slade Ph.D.  Margaret S. Steward Ph.D.  Thomas L. Morrison Ph.D.  Stephen I. Abramowitz Ph.D. 《Child abuse & neglect》1984,8(4):447-457

Abused children are believed to develop in a harsh environment with minimal contingency of parental responses to their behavior. Seligman proposed that noncontingent caregiving produces helplessness. In this study, helplessness was assessed by measures of persistence and locus of control and by an experimental manipulation which varied contingency feedback. Compared to matched nonabused peers, abused children showed no less persistence in working for rewards, made equivalent use of contingency information to maintain persistence, and assumed equivalent responsibility for success. However, they took less responsibility for failure. Family learning history may render abused children helpless primarily in avoidance of aversive outcomes.  相似文献   

Some correlates of culture shock among American tourists in Africa     

Douglas A. Cort  Michael King 《Int J Intercult Relat》1979,3(2):211-225

The effects on culture shock of prior travel experience, feelings of internal/external control, and intolerance of ambiguity were examined in American tourists to Africa. Participants, 42 members of a university sponsored six week tour of East Africa, ranged widely in age and prior travel experience. Hostility toward Africans, withdrawal from cross cultural contact, and overidentification with America were assessed with ratings by tour leaders and by participant self reports. Prior travel experience does not correlate significantly with culture shock, a finding confounded in this study by age. Older tourists had more prior travel but also experienced greater culture shock. Those less tolerant of ambiguity experienced greater culture shock. Internal/external control feelings did not correlate significantly with culture shock. Combining personality and prior travel in multiple regression did not significantly improve prediction of any of the culture shock manifestations over that of the best single predictor. Results are discussed primarily in terms of differences between the cross cultural experience of tourists and that of other groups in which culture shock has been studied.  相似文献   

基于PLC的液压机械手控制系统改造     

张文汉  陈军峰 《科技广场》2008,(7)

本文叙述了管料冷弯机液压机械手的控制系统改造,主要包括冷弯机液压机械手的液压传动系统、PLC控制系统的设计、机型选择等改造内容。  相似文献   

家用多媒体电脑的配置     

许芝卉 《雁北师范学院学报》2000,(6)

该文就配置较为理想和实用的光驱、声卡、解压卡、调制解调器等多媒体部件做了说明  相似文献   

《骆驼祥子》"被"字句定量分析     

殷相印 《济宁师范专科学校学报》2005,26(2):70-72,88

“被”字含蒙受义,表示一种遭受现象,这种语义上的独特之处,使汉语“被”字句在被动意义之外,多了一层不幸、不如意不愉快或者有所损害等语义色彩。本文拟就《骆驼祥子》被字句的补语和否定形式的句法结构特点的数量统计和分析,探究现代汉语“被”字的这一语义特征。  相似文献