王徵——欧洲科学技术与文化的传播者

王徵是明代末年著名的科学技术研究者和传播者,也是最早一代接受来自欧洲的科技和文化并皈依天主教的中国学者之一,在跨文化的知识传播及中国宗教史上占有重要的地位。王徵的父亲和舅父对他一生的治学宗旨及宗教观的形成有很大的影响。虽然王徵曾长时间研究佛教、道教,并最终在耶稣会士的影响下皈依了天主教,但本质上他从未背弃儒家的核心道德理念。儒家理念直接影响了他的工程技术实践及其对西方知识的选择。王徵将儒家经世思想与其对技术和机械制造方面的兴趣结合起来,成为一名敢于任事官吏及对维护社会稳定有贡献的士绅,并最终为效忠明王朝牺牲了自己的生命。他与邓玉函合译的《远西奇器图说录最》是最早系统介绍西方力学知识的中文著作,在中国力学史上具有里程碑的意义。     

农业机械标书评价指标体系设计原理

在农业机械购置补贴过程中，采取招投标的形式是实现科学选型的有效措施。然而在标书评价中，影响因素及评价指标的选取往往存在较大的主观随意性。针对此问题，根据辩证法的对立统一等哲学原理，从指标体系的设计过程入手，提出从影响主体确定、案例归纳与推理、评价主客体换位思考、影响因素显性化与系统体系形成相结合的农业机械标书评价指标体系设计原理，并详细剖析了设计原理具体实现的步骤。     

机械制造专业应用型人才培养方案的改革与实践

以中国制造发展战略和江苏的国际制造业基地建设规划为背景,依据高等学校机械学科本科专业规范、机械工程师资格考试大纲、应用型人才培养目标定位及其知识、能力、素质结构,重新设计了机械设计制造及其自动化专业机械制造方向人才培养方案。该方案以数控机床设计、制造、运用人才为培养目标,注重综合实践与工程训练,强化数字化设计制造应用能力培养,注意道德法律、技术经济、质量管理教育,提出以一个核心、两条路线、四个层面、五种意识、七种能力、八个环节构建实践教学体系。新方案的初步实践,正在展现其提高人才培养质量的成效。     

Online bin packing of fragile objects with application in cellular networks

We study a specific bin packing problem which arises from the channel assignment problems in cellular networks. In cellular communications, frequency channels are some limited resource which may need to share by various users. However, in order to avoid signal interference among users, a user needs to specify to share the channel with at most how many other users, depending on the user’s application. Under this setting, the problem of minimizing the total channels used to support all users can be modeled as a specific bin packing problem as follows: Given a set of items, each with two attributes, weight and fragility. We need to pack the items into bins such that, for each bin, the sum of weight in the bin must be at most the smallest fragility of all the items packed into the bin. The goal is to minimize the total number of bins (i.e., the channels in the cellular network) used. We consider the on-line version of this problem, where items arrive one by one. The next item arrives only after the current item has been packed, and the decision cannot be changed. We show that the asymptotic competitive ratio is at least 2. We also consider the case where the ratio of maximum fragility and minimum fragility is bounded by a constant. In this case, we present a class of online algorithms with asymptotic competitive ratio at most of 1/4+3r/2, for any r>1. A preliminary version of this paper appeared in Proc. of Workshop on Internet and Network Economics (WINE’05, pp. 564–573). The research of W.-T.C. was supported in part by Hong Kong RGC grant HKU5172/03E. The research of F.Y.-L.C. was supported in part by Hong Kong RGC Grant HKU7142/03E. The research of D.Y. was supported by NSFC (10601048). The research of G.Z. was supported in part by NSFC (60573020).     

机械原理课程实验教学改革探讨

机械原理实验课程是培养学生创新意识和实践能力的重要教学环节。文章从构建新型实验课程体系,更新实验教学手段,虚拟实验同传统实验手段相结合,合理安排实验,加强对实验教学考核等几方面对机械原理实验课程教学改革进行了有益的探索。     

机车牵引电机电器故障可靠性诊断分析系统

为了提高机车研究、设计、制造以及维修水平,提高机车牵引电机、电器设备的可靠度,有必要开发机车牵引电视、电器故障可靠性诊断系统.文中介绍了在WINDOWS98下开发的机车牵引电机、电器故障可靠性诊断分析系统的设计方法和实现技术,主要包括系统目标、系统设计及实现中的关键技术.     

Computational precision in statistics: variances and covariances †

“Precision” may be thought of either as the closeness with which a reported value approximates a “true” value, or as the number of digits carried in computations, depending on context. With suitable formal definitions, it is shown that the precision of a reported value is the difference between the precision with which computations are performed and the “loss” in precision due to the computations. Loss in precision is a function of the quantity computed and of the algorithm used to compute it; in the case of the usual “computing formula” for variances and covariances, it is shown that the loss of precision is expected to be log k _i k _j where k _i , the reciprocal of the coefficient of variation, is the ratio of the mean to the standard deviation of the ith variable. When the precision of a reported value, the precision of computations, and the loss of precision due to the computations are expressed to the same base, all three quantities have the units of significant digits in the corresponding number system. Using this metric for “precision,” the expected precision of a computed (co)variance may be estimated in advance of the computation; for data reported in the paper, the estimates agree closely with observed precision. Implications are drawn for the programming of general-purpose statistical programs, as well as for users of existing programs, in order to minimize the loss of precision resulting from characteristics of the data, A nomograph is provided to facilitate the estimation of precision in binary, decimal, and hexadecimal digits.     

博学多才的古代科学家祖冲之:纪念祖冲之逝世1500周年

简要介绍祖冲之的生平，阐述他在数学、天文、机械等方面的十项重要成就。     

1.5m2高频振动筛结构改进

针对目前在矿棉板备浆生产线上广泛使用的高频振动筛存在的噪音大、动力消耗大、筛板易堵塞、除渣效果差等 问题,对高频振动筛筛框结构、筛板形状和减震弹簧等进行了优化改进,对振动频率、振幅、筛板的孔径通过理论计算得 出几个基本数值范围,再通过对基本数值范围内的不同数值的实际测试,确定最佳数值。新设计的振动筛经实际使用表 明运行稳定,浆料利用率高,能耗低,噪音小,取得了很好的经济效果。     

铸铁烘缸椭圆人孔盖的计算

为了解决铸铁烘缸承压元件椭圆形人孔盖设计计算的困扰,设计人员基于国内规范结合ASME规范寻求一种新 的设计计算方法,即利用ASME规范提供的数表找到适合于铸铁烘缸人孔盖材料的特性曲线,将此特性曲线提供的特性 数值代入已经成熟的算例当中,从而计算出人孔盖的承压能力。此方法一旦成熟可以解决椭圆形人孔盖设计计算的难 题,使铸铁烘缸人孔盖的设计进一步的优化