Temperature distribution in toroidal electrical coils of rectangular cross section

The essential content of a recent paper by the present writer comprises a comprehensive discussion of the physical bases underlying derivation of formulas for calculating the temperature distribution T, maximum temperature T_m and average temperature T_a in a toroidal electrical coil of rectangular cross section, internally generated heat and change of wire resistance with temperature being taken into account. Illustratively, the solution for the boundary value condition of constant surface temperature and uniform equivalent thermal conductivity was obtained.For the most part, however, problems that arise in practice are not encompassed in the comparatively simple boundary conditions of constant temperature. Experiment shows that in general the boundary condition is $\text{T ? T′ = ?}\text{K?}\text{?n}$; whereof n denotes the outward drawn normal to the coil surface, $\text{K = (}\text{k}{}_{\mathrm{n}}\text{h}\text{)}$ the ratio of the equivalent thermal conductivity in the direction of n to the emissivity of the boundary surface, and T and T′ are the corresponding temperatures in the coil surface and the immediately adjacent ambient medium. Again, it frequently ensues in practice that the thermal conductivity is substantially different in the directions of the two principal axes of the cross section.In the present paper formulas for T, T_m, and T_a are obtained for electrical coils of ratio of external to internal radius greater than (roughly) two whereof (i) the thermal conductivity is different in the directions of the two principal axes of the cross section, (ii) K is different on but constant over each of the four faces of the coil, and (iii) no restriction is made as to T′ except that over each face it be expressible in a generalized Fourier series. Determination of T is posed as a boundary-value problem in the mathematical theory of heat; the formal solution of T effected by expansions in orthogonal functions; and T_m and T_a then determined through use of their known relationships with T. The resulting formulas are in the form of rapidly-converging singly-infinite trigonometric-hyperbolic series. Illustrative of application of these general formulas, the maximum temperatures in a coil of given dimensions subject to two different sets of surface conditions are calculated and found to be in excellent agreement with the known measured values.The just-mentioned formulas encompass practically all cases encountered in practice except those coils which do not satisfy the restriction as to ratio of radii. For these latter formulas for T, T_m, and T_a are obtained pursuant to conditions of (i) equivalent thermal conductivity different in the directions of the two principal axes of the cross section, (ii) K, and likewise T′, different on but constant over each of the four faces of the coil. These formulas are in the form of rapidly-converging singly-infinite trigonometric- Bessel function (of zero order) series: Illustratively, the maximum temperature in a coil of given dimensions is calculated and found to be in excellent agreement with the known measured value.     

Radiation fields from polygonal sources

The calculation of the radiation field D(x, y, z) produced by a uniform polygonal source is of considerable practical importance. Fock showed that there are advantages in replacing the traditional surface integral by a contour integral, using Stokes' theorem. This innovation, however, has not yet penetrated very deeply. It seemed worthwhile, therefore, to systematize the procedure and to show how easily results can be obtained by the Fock method. An incidental conclusion of the paper is that the radiation field from a polygonal source often differs by less than one per cent from the field produced by a circular disk of the same area. Thus the simple disk formula can often be substituted for the more complicated polygonal formula.     

NSFC医学论文的Z-P分布

本文利用《中国生物医学文献光盘数据库》(2002.1-2004.12),对国家自然科学基金(NSFC)论文的Z-P分布进行分析和探讨。将我国各省(市、自治区)受NSFC资助产生的医学科研论文进行统计分析和横向比较,从理论上和实际应用两个方面进一步验证Z-P分布模型,并为我国科学基金政策提供数据支持。     

不同来源FDI在华技术溢出效应实证研究

本文使用中国各地区相关数据,分析了不同来源FDI在我国工业部门产生的技术溢出效应差异。发现在总体层次上,港澳台外资产生了明显的技术溢出效应,而其它外资没有表现出显著的技术溢出效应。通过进一步研究经济发展程度对技术溢出效应的影响,发现只有在经济发达地区,港澳台外资才产生了明显的技术溢出效应。     

Determinants of environmental innovation—New evidence from German panel data sources

In most cases, empirical analyses of environmental innovations based on firm-level data relied on surveys for one point in time. These surveys allow for the inclusion of many explanatory variables such as different policy instruments or the influence of pressure groups but it is not possible to address the dynamic character of environmental innovations. This paper uses two German panel databases, the establishment panel of the Institute for Employment Research (IAB) and the Mannheim innovation panel (MIP) of the Centre for European Economic Research (ZEW), to explore the determinants of environmental innovations. The econometric estimations show that the improvement of the technological capabilities (“knowledge capital”) by R&D triggers environmental innovations. Environmental regulation, environmental management tools and general organizational changes also encourage environmental innovation, a result that has also been postulated by the famous Porter-hypothesis.     

International alliances as sources of capital: Evidence from the biotechnology industry

This study empirically tested the relationship between three signaling mechanisms (scientific capabilities, firm location and top management team international experience) and the amount of capital raised through international strategic alliances. The number of patents held by the firm, firm location and the number of products in stage III of development were found to be significant. Implications for managers and researchers are discussed.     

Pulsatile fully developed flow in rectangular channels

Solutions for pulsatile fully developed flow of Newtonian viscous fluid in a straight rectangular channel can be synthesized from analytic solutions of steady flow and oscillatory flow. A new steady solution is presented that is valid for all duct aspect ratios. Also new oscillatory solutions are given, showing dependence on a “viscous diffusion length”, the square root of the kinematic viscosity divided by frequency.     

福建省能源发展科技月谈会建议 重视洁净新能源和可再生能源开发利用

6月21日,省科协举行福建能源发展科技月谈会.省委粱绮萍副书记、省政府黄小晶常务副省长出席会议并讲了话.省能源研究会的专家、省直有关单位和部门的负责人以及新闻记者参加了会议.月谈会由省科协党组书记、副主席刘群英主持.     

矩形平板典型非定常拍动的三维效应

用三维非定常面元法研究了不同展弦比矩形平板拍动的非定常气动响应.通过对矩形平板沉浮和俯仰2种基元运动的三维效应分析,得到如下结论:矩形平板非定常运动中,附加惯性效应影响了升力的瞬时值,其幅值随着展弦比的降低而减小,但时均值总为零;尾缘涡和侧缘涡作用是平均升力的来源,因矩形板在一个拍动周期内流向涡的方向发生改变,涡致升力的三维效应会随拍动非定常性增强而减弱.     

农业生态系统地下水氮面源污染数值模拟

结合农业生态系统特征,以实例展示了在仅有短期有限野外监测数据及少量野外试验条件下,通过合理概化、参数分步识别与过程综合分析等,使模型识别的可靠性提高,成功地建立了农业生态系统地下水氮面源污染数值模型,并反演出表征农业氮面源污染特征的地下水入渗补给强度和氮补给量.本研究对定量评价农业生态系统地下水氮面源污染,特别是对野外基本调查工作部署与根据有限的基本数据较好地模拟识别特征参数,具有一定借鉴意义.