Random vibration analysis of switching apparatus based on Monte Carlo method

The performance in vibration environment of switching apparatus containing mechanical contact is an important element when judging the apparatus’s reliability. A piecewise linear two-degrees-of-freedom mathematical model considering contact loss was built in this work, and the vibration performance of the model under random external Gaussian white noise excitation was investigated by using Monte Carlo simulation in Matlab/Simulink. Simulation showed that the spectral content and statistical characters of the contact force coincided strongly with reality. The random vibration character of the contact system was solved using time (numerical) domain simulation in this paper. Conclusions reached here are of great importance for reliability design of switching apparatus.     

水稻免耕栽培生理基础——Ⅱ.免耕水稻的光合特性

威优64、陆青早1号作为试验材料,免耕能提高功能叶的光合速率、生育前期功能叶的呼吸强度、绿叶面积、叶绿素和可溶性蛋白含量,并延缓它们在生育后期的下降速率,降低后期功能叶的呼吸速率。主分量分析说明,在研究光合作用时,光合强度、叶绿素、可溶性蛋白质、叶片含氮量,可以任意选择一个作为光合特性指际。粒/叶比说明,免耕对源的改善较对库的改善较好些。     

应用型本科CAD/CAM课程教学改革之初探

围绕应用型本科的培养目标和机械设计制造及自动化专业CAD/CAM课程教学的特点,从教学内容、教学方法、教学模式、考试方法及提高教师自身素质等方面的教学改革进行有益的尝试和探讨.     

和谐发展:反对消费主义

作为西方现代化产物的消费主义是现代资本的逻辑结果,与资本主义增长型发展观紧密相连。但它并不是现代化理想的实现,而是现代化畸形的片面发展,导致现代人生存的全面异化和一系列生存危机。和谐发展观作为救治现代生存病症、反对消费主义的一种努力,在人与自然的维度上,限制人类对自然的掠夺性消费,重建人与自然包括审美关系在内的全面健康、和谐共生的关系。在人与人、人与社会的维度上,把人际关系从单一的商品生产—消费关系及其衍生关系中解放出来,恢复亲情、友谊、伦理等丰富多元、和谐相处的人际关系。在人与自我的维度上,对“经济人”“消费者”的设定应持一种审慎的批判态度,彰显可能被其遮蔽的人之存在的所有可能性维度,尤其要恢复人的终极关切和敬畏。     

Paired peer learning through engineering education outreach

ABSTRACT

Undergraduate education incorporating active learning and vicarious experience through education outreach presents a critical opportunity to influence future engineering teaching and practice capabilities. Engineering education outreach activities have been shown to have multiple benefits; increasing interest and engagement with science and engineering for school children, providing teachers with expert contributions to engineering subject knowledge, and developing professional generic skills for engineers such as communication and teamwork. This pilot intervention paired 10 pre-service teachers and 11 student engineers to enact engineering outreach in primary schools, reaching 269 children. A longitudinal mixed methods design was employed to measure change in attitudes and Education Outreach Self-Efficacy in student engineers; alongside attitudes, Teaching Engineering Self-Efficacy and Engineering Subject Knowledge Confidence in pre-service teachers. Highly significant improvements were noted in the pre-service teachers’ confidence and self-efficacy, while both the teachers and engineers qualitatively described benefits arising from the paired peer mentor model.     

Hydrogenation properties of mechanically milled Mg2Nio.8Cr0.2-CoO/Al2O3 composites

Mg2Ni0.8Cr0.2-x wt.% CoO/Al2O3 (x=0.5, 1, 2 and 3) composites were prepared by mechanically milling sintered Mg2Ni0.8Cr0.2 alloy and CoO/Al2O3 compound for 45 h. The addition of CoO/Al2O3 compound resulted in the good kinetics properties of hydriding/dehydriding reaction of the composites. The composite with 1.0 wt.% CoO/Al2O3 catalyst could reach the maximum hydrogen absorption capacity (2.9 wt.%) within 5 min at 393 K under H2 pressure of 4 MPa, and can desorb rapidly at 493 K. The decomposition and synthesis of hydrogen molecule on Mg2Ni0.8Cr0.2 alloy surface was promoted by addition of CoO/Al2O3 catalyst. In addition, the formation of metallic Ni particles, strain and defects during the ball milling process also resulted in the improved hydrogenation performance of Mg2Ni-based alloys.     

结合专业特色应用现代教育技术服务于中小学教学

现代教育技术的应用,深刻影响高中小学各科教学.传统的教学模式必须与现代教育技术进行整合,才能适应新课程教学改革的需要.充分发挥教育技术专业人才的主导作用,担当教育技术现代化的排头兵.     

实时多媒体数据传输的研究及实现

本文主要进行RTP／RTCP与TCP协议的比较，着重分析RTP／RTCP协议对分组网上视频业务Qos的保证。在IP电话的实现中编码后的数据流采用RTP／RTCP协议来打包传送。结果表明，开发出的软件实时性好。     

8253定时/计数器方式3计数过程的实验研究

对于我系选用教材和部分参考资料关于8253定时/计数器在方式3的计数过程中表述中所存在的矛盾之处,基于武汉众友电子科技有限公司的接口实验台,提出了一个探究8253计数过程的实验方案。通过分析实验结果,指出了正确的计数过程。     

Three dimensional couette flow and heat transfer through a porous medium with variable permeability

This paper reports research on the effects of variations in injection velocity and permeability on the heat transfer and flow through a highly porous medium between two horizontal parallel plates situated at constant distance with constant suction by the upper plate. Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional. The governing equations are solved by adopting complex variable notations to obtain the expressions for the velocity and temperature field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs.