场效应管夹断电压的作用及测试

根据夹断电压能确定可变电阻区与饱和区的分界点,使场效应管可靠地工作在饱和区的原理。研究了夹断电压的测试问题,介绍了测试场效应管夹断电压的方法,进而找出预夹断电压,由此即可确定场效应管的饱和区。     

英国超市消费现象分析及其启示

英国超市消费逐年增长 ,其经营方式更加灵活 ,销售领域更加广泛。中国是一个人口大国 ,随着居民收入水平的不断提高 ,消费水平也必然不断提高 ,如何使我国超市消费成为新的消费热点 ,引导超市经营向良性发展 ,我们可以透过英国超市消费现象 ,得到很好的启迪     

MICTS: Municipal ICT Schools – A Means for Bridging the Digital Divide Between Rural and Urban Communities

There is a substantial difference in use and development of information and communication technologies and services between and within countries. Some denote this phenomenon as the digital divide.This paper addresses the competence aspect of the digital divide. It proposes municipal ICT schools as one model aimed to bridge this gap and provides an assessment of the model based on the results from a field trial in three rural municipalities in Norway. The model brings the benefits of increased competence of ICT in the communities but in addition have a potential with regard to stimulating talent development, serving as a resource for local business and offering meeting places in the communities for building social capital. The model may be successfully implemented within reasonable economic limitations but is also challenging in several ways, for instance on how teaching resources are recruited and supported.The purpose of the paper is to bring forward the discussion about how to bring all people, also those in rural areas, to be participators in the information technology age.     

连续定态传热过程平均温差的统一推导

采用统一的方法对定态传热逆流和并流的平均温差进行了推导。推导过程无需假定冷热流体的特定流向,并利于得到对数平均温差“同侧相减”的规律。     

Beta-Gamma函数对余元公式的推导与实现

对构造的公式①,在复数域将其被积函数分解得2n个复根.在实数域将其实虚部积分取极限获证.对构造的公式②,由①将其被积函数的连续性、收敛性及一致收敛性与构造的有理数列用变量替换代入取极限获证.再由①与②应用Gamma-Beta函数的另一形式及(3),得到了余元公式的实现.     

再论向量场X(v)=Av+f(v)v的极限环

得到了向量场有极限环的必要条件是2×2矩阵A有复特征值,以及讨论了极限环存在和唯一的一些充分条件,这里f(v)也许是非齐次函数。     

关于比较教育若干问题的再探讨

虽然比较教育作为一门学科,人们已经形成了共识。但关于比较教育仍有许多值得探讨的问题。文章就对“比较”的认识,比较教育是一门学科还是一个研究领域以及比较教育的特征进行了探讨。     

静电场环路定理在静电场中的地位及应用

文章从静电场力作功的特点出发，说明静电场是保守力场。然后通过与高斯定理比较，阐述了静电场环路定理在静电场中的地位。并通过两个典型例子说明静电场环路定理的应用。     

Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system

Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNGk-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43000. The working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model. Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera. The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good agreement with the numerical result. Project supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry of China (No. 50175097)     

物流业入世后过渡期营销创新研究

随着入世后过渡期的到来,市场开放将提速,并逐步取消外贸引入的地域限制、数量限制、股权限制等,这将对中国的物流业带来一定的影响。通过对中国物流业的SWOT和应对WTO 策略分析,营销创新对振兴中国物流业将起到积极的作用。