用分岔方法讨论有心力场轨道的稳定性     

孙彦  孙祝  程丽平 《雁北师范学院学报》1998,(5)

该文用分岔理论证明了在有心力场中运动的质点,其运动轨道不论形式如何,只要n<3,都是稳定轨道。  相似文献   

A step function in pigeons’ temporal generalization in the peak shift task     

Marcia L. Spetch  Ken Cheng 《Learning & behavior》1998,26(1):103-118

Pigeons were reinforced for pecking a key following one signal duration (S+) but not following another signal duration (S?). The S+ and S? were 2.52 and 5.67 sec, respectively, counterbalanced across birds. Subsequent generalization tests with a range of signal durations revealed a step function, with high response rates for all durations on the S+ side of the distribution, low response rates for all durations on the S? side, and an intermediate rate for the intermediate duration. A comparison group of pigeons trained with only the S+ duration showed a flat generalization function. For the discrimination-trained birds, the delay between signal termination and opportunity to respond was subsequently varied during generalization testing. A step function again appeared, and no evidence of subjective shortening over the delay was found. The overall pattern of results suggests that the birds categorized the temporal signal into two classes and retained a categorical code over the delay.  相似文献   

Distances and directions are computed separately by honeybees in landmark-based search     

Ken Cheng 《Learning & behavior》1998,26(4):455-468

Honeybees were trained with two landmarks at some angle (e.g., 120°) apart from the target. On crucial unrewarded tests, only a single landmark was present. If distances and directions to landmarks are computed separately (independent averaging), the search distance to the landmark should equal the landmark-target distance found in training. If entire vectors are averaged, the search distance should be much shorter. Three experiments with short target-landmark distances showed results in between the predictions of the two hypotheses. A fourth experiment used longer target-landmark distances and isolated double peaks on single-landmark tests: one predicted by the independent averaging hypothesis, and one very close to the landmark. The near peak is interpreted as arising from approach and exploration of a landmark in a new location, and not from searching.  相似文献   

γ射线对长寿命mRNA的影响     

陈梅香  邓小芳 《衡阳师范学院学报》1998,19(6):40-43

本实验根据中心法则,用放线菌素D抑制新mRNA转录而研究γ射线对长寿命mRNA的生理生化功能的影响,得出γ射线抑制新转录mRNA的生长效应而促进预存mRNA的生长效应。  相似文献   

以成本信息集成为中心的CIMS建立     

蔡自兴  王志坚  陈松乔 《中国教育信息化》1998,(1)

本文在分析企业当前生产经营管理特点的基础上,讨论了 CIMS 中信息集成模式的问题,提出CIMS 中以成本信息集成为中心的信息集成模式,以期通过成本信息的集成来实现整个 CIMS 信息的集成。文章讨论了企业对成本管理的要求、作业成本计算过程、成本信息的范畴和成本控制的方法等问题,论述了成本信息集成的技术路线和成本信息集成的基本原则,最后讨谈论了企业 CIMS 分阶段目标规划。  相似文献   

谈如何提高听说能力     

程淑荣 《北京城市学院学报》2004,(4):96-97

学生的听说能力一直是大学英语教学中的薄弱环节。本文提出,要提高听说水平,教师必须纠正传统 的教学方式,既要重视语言基础传授,又要强化听说技能的培养。  相似文献   

分层流体中弧立波的理论分析和符号运算研究     

程友良 《上海大学学报(英文版)》1999,3(1):84-86

The study of solitary waves has been a subject highly popular and full of interest sinec Russell[1]first observed the solitary waves in a channel and the research on the internal solitary waves in stratified fluids is one of the branches of this subject.There are extensively internal solitary waves in the atmosphere,oceans.fjords and lakes.To study them is of academic and practical significance[2].Numerous investigators have made contributions since the theoretical work on internal solitary waves was initiated by Keulegan[3].Nevertheless,some problems remain still to be discussed,for example,the higher-order theories for one-dimensional internal solitary waves in stratified fluids of small depth,the two-dimensional internal solitary waves,the explanation of the experimental and the practical phenomena by means of theoretical analysis.In this thesis,we hope to gain an insight into the above three items by combining of theoretical analysis and symbolic computation.The following work has been completed.  相似文献   

On self-recovery mechanism and additional maneuverability of a mini mobile robot     

QIAN Jin wu SU Jian liang GU Jian feng HE Yong yi CHENG Wei ming ZHANG Ya nan 《上海大学学报(英文版)》1999,3(3):223-226

１　Ｉｎｔｒｏｄｕｃｔｉｏｎ　Ａｕｔｏｎｏｍｏｕｓｍｏｂｉｌｅｒｏｂｏｔｓｗｉｔｈｌｅｇｓｏｒｗｈｅｅｌｓｗｏｒｋｉｎｇｉｎｈａｚａｒｄｅｎｖｉｒｏｎｍｅｎｔｓｏｒｏｎｒｏｕｇｈｔｅｒｒａｉｎｗｉｌｌｆａｃｅｔｈｅｐｏｓｓｉｂｉｌｉｔｙｏｆｂｅｉｎｇｔｕｒｎｅｄｏｖｅｒｂｙｕｎｅｘｐｅｃｔｅｄｒｅａｃｔｉｏｎｂｅｔｗｅｅｎｔｈｅｒｏｂｏｔａｎｄｔｈｅｅｎｖｉｒｏｎｍｅｎｔ．Ｔｙｐｉｃａｌｅｘａｍｐｌｅｓａｒｅｖｏｌｃａｎｏｅｘｐｌｏｒａｔｉｏｎｒｏｂｏｔｓ,ｌｕｎａｒｏｒＭａｒｓｒｏｖｅｒｓ…  相似文献   

在齿轮强度计算中应注意的几个问题     

程友联 《荆门职业技术学院学报》1999,14(3):56-57

本文列举了在“齿轮传动强度计算”中易产生误解或不易理解的几个问题,并对这些问题进行了探讨,提出了教师在教学中解决这些问题的方法。  相似文献   

教育评估专家评判的价值取向          下载免费PDF全文

程婕  林涛 《上海教育评估研究》2020,9(2):22-27

现阶段我国教育评估中对人的评价出现了唯分数、唯升学、唯文凭、唯论文、唯帽子的价值偏差,脱离了教书育人的根本目的。专家评判是教育评估的重要组成部分,专家评判的价值取向直接关系到评估结果的科学性和公信力,但是专家判断中也严重存在"五唯"现象。因此教育评估要回归到教育的本意,即"育人",要以"立德树人"成效为依据,以促进"人的全面发展"为目标,破除唯一性、单一性的评价价值取向,并从专家主体的价值认同和评判尺度统一、评估标准"唯"与"不唯"的平衡点、客观数据与主观评判关系、道德自律与规则他律四个方面探寻教育评估专家评判价值取向的实现路径。  相似文献