关系数据库设计范式应用实例剖析

关系数据库中的关系必须满足一定的要求,满足不同程度要求的为不同范式,本文就数据库设计中经常使用的1NF、2NF、3NF和BCNF进行了详细的剖析,通过实例指出满足一定的范式可以使数据库结构清晰简洁。     

学校管理标准:构建及思考——兼谈UNICEF爱生学校标准的主要内容

作为一个国家教育管理的标志和衡量尺度,学校管理标准具有引领、规范、监测、预测和解释学校管理及学校教育发展的多种功能。为促进我国学校管理的规范化和科学化,克服"凭经验办教育"、"凭感觉做管理"的历史缺陷,我国应尽快建立自己的学校管理标准。联合国儿童基金会的"爱生学校标准"值得我们借鉴。     

毛泽东社会主义思想的理论贡献与时代意义

毛泽东社会主义思想的全面提出为开拓中国特色社会主义事业留下了宝贵的理论遗产。它是社会主义思想史上的一次飞跃。其理论贡献和时代意义，为我们在新的发展历史阶段上，建设中国特色社会主义提供了重要启示。     

电导法准确测量乙酸乙酯皂化反应速率常数的实验方法研究

本文拟在通过实验,叙述乙酸乙酯的皂化反应速率常数的测定,使用原来酯碱有相同起始浓度的所谓常规电导法进行测定,其实验结果不准确,与化学方法测定的文献值相差较大,分析误差产生的内在原因后,提出改进电导法的测定原理。克服了原来常规电导法的不足,并用实验数据加以论证,从而得出较满意的结果。     

Sap flow response of Eucaylyptus (<Emphasis Type="Italic">Eucalyptus urophylla</Emphasis>) to environmental stress in South China

Sap flow and environmental conditions were monitored at two Eucalyptus (Eucalyptus urophylla S.T. Blake) plantations at Hetou and Jijia, located in Leizhou, Zhanjiang, Guangdong Province. It was found that daily sap flux density (SFD) of Eucalyptus was closely related to daily atmospheric vapor pressure deficit (VPD) (R ²=0.76, P=0.01 at Hetou and R ²=0.7021, P=0.01 at Jijia) at both sites. No significant relationship existed between daily SFD and mean daily air temperature at both sites. Daily SFD varied with wind speed Y=−17585X ³+15147X ²−1250.7X+2278.4 (R ²=0.68; P=0.01) at Hetou and Y=−101.67X ³−1.65X ²−376.4X+1914.8 (R ²=0.40, P=0.05) at Jijia, where Y was daily SFD, X was daily wind speed. Experimental observations yielded the following data: (1) the critical lower and upper daily VPD threshold were 0 and 2 kPa, within which daily SFD varied from 540±70 L/(m²·d) to 4739±115 L/(m²·d) at Hetou site, from 397±26 L/(m²·d) to 3414±191 L/(m²·d) at Jijia site; (2) Diurnal SFDs at Hetou site were much higher under low relative humidity (<30%) and slightly lower under high relative humidity (>80%) compared with those at the Jijia site; (3) The upper and lower threshold of daily and diurnal RAD for the optimal water use of E. urophylla plantations were 18±2.7 and 2±1 MJ/(m²·d), 669 and 0 J/(cm²·h) during the observation period. Project supported by Knowledge Innovation Funds from Chinese Academy of Sciences (Nos. KSCX2-SW-120, KZCX1-SW-01-01A3) and the Key Project of Guangdong Natural Science Foundation (No. 010567), China     

Na?ve Students’ Conceptual Development and Beliefs: The Need for Multiple Analyses to Determine what Contributes to Student Success in a University Introductory Physics Course

This research involved na?ve physics learners who were interested in majoring in science or engineering. In a semester-long quasi-experimental study, open-ended pretests and weekly interviews were used to analyse the progressive development of students’ conceptions relating to sound and wave motion. Semi-structured interviews were also conducted to elucidate: (1) how their conceptions developed from everyday conceptions to unclear scientific conceptions to scientific conceptions, and (2) their beliefs of physics knowledge. Despite efforts to enable these students to learn physics, the findings showed that only two out of ten students developed acceptable physics conceptions during the course that would enable them to pursue the subject to a higher level. Also, students’ conceptual development was found to be related to their cognitive understanding and to epistemological beliefs of physics. Therefore, to facilitate na?ve physics learners’ success in a general physics course, in addition to the acquisition of content knowledge, explicit emphasis needs to be placed on the nature of physics knowledge.     

菊科莴苣属订正及亚洲大陆菊科植物二新属

本文是对菊科莴苣属Lactuca L. 的分类订正, 文中起用了乳苣属Mulgedium Cass.和山   莴苣属Lagedium Sojak两个较老的属名, 建立了二个新属，即翅果菊属Ptrocypsela Shih与假   福王草属Paraprenathes Chang. 文末提供了莴苣属及邻近属以及东亚地区的有关种类的分属分种检索表。     

我国生物安全问题的现状分析及对策

在跨越了改变自身以适应环境和改变环境以适应自身的两大历史阶段之后,人类社会已进入到既能改变环境又能改变自身的历史新时期。由生物技术带来的安全风险具有人类历史发展的必然性,只能面对而不能回避。除空天、海洋、网络、传统安全外,生物威胁已上升为新的安全疆域,在当前我国重要战略机遇期构成了全新的安全需求。文章简述了自SARS暴发以来国内外生物安全问题的发展态势,深入分析了当前我国所面临生物安全威胁的现实特点。在对前人所做生物安全问题研究的基础上,总结归纳出了生物安全理论的框架。同时,以生物安全理论内涵为指导,对未来我国所面临生物安全威胁的发展走向进行了预测,提出了以新观念主导战略能力建设、以理论创新主导科技支撑、以体系应对新型生物性危害的实施策略。