给数字万用表增加新功能

一般数字万用表不能直接测量电容、功放、运放等电路。但如果将数字万用表的压电陶瓷片的两端焊下一脚，串联接入一双孔插座A、B，并将A、B固定于表上，双孔外露，则可给数字万用表增加许多新的功能。下面以带有蜂鸣功能的890型数字表为例，介绍使用方法。     

A review of the effect of a／W ratio on fracture toughness （Ⅰ）—experimental investigation in EPFM

Many experimental investigations have previously been performed and recently done on different shipbuilding structural steels where the specimens size and crack depth/specimen width (a/W) were varied. A series of interesting results have been gained. It is worthwhile to have a review on the effect of a/W ratio on fracture toughness, and further theoretical analysis is necessary. In this paper, experimental work in elasticplastic fracture mechanics (EPFM) was discussed. Tests had been carried out on 10 kinds of strength steels. Results showed that J _i and δ₁ values increased with decreasing a/W when a/W<0.3 for three-point bend specimens and that shallow crack specimens which have less constrained flow field give markedly higher values of toughness than deeply notched specimens. However, for a/W>0.3, the toughness was found to be independent of a/W. Slip line field analysis shows that for shallow cracks, the hydrostatic stress is lower than that from standard deeply cracked bend specimen which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structure defects especially if initiation values of COD/J-integral are used.     

Geometric modelling of bulbous bows with the use of non-uniform rational B-spline surfaces

Nowadays, bulbous bow forms have become a common design feature in most conventional ship designs. The design of a bulbous bow is usually attempted with the use of certain form parameters that are imposed using the designer's experience or regression values that provide the optimum parameters based on experimental tests or computational fluid dynamics (CFD) calculations. In this article, the geometric modelling of a bulbous bow form that complies with a series of parameters is presented. First, a wire model was constructed with cubic B-spline curves that hold certain form parameters that the designer wants to impose. Second, a B-spline surface that fits these splines was mathematically constructed. A review of the influence of the design parameters used on the bulbous bow properties was made. This method could be used prior to numerical optimization of a bulbous bow because different variations of the design can be easily generated. These variations can be tested numerically using CFD software. A practical application example of the method is shown.     

浅谈铁路预应力钢筋混凝土T型简支梁投标报价中应注意的几个问题

近年来,铁路用钢筋混凝土简支梁的评标原则,均是在商务符合性评审的基础上,选择合理低标中标。以渝怀铁路预应力钢筋混凝土简支T梁,赣龙铁路预应力钢筋混凝土简支T梁及浙赣铁路电气化改造工程预应力钢筋混凝土简支T梁3个项目的投标情况为例,进行了详细分析,总结出投标报价应遵循的几个原则:合理分析风险,准确测算成本,巧妙确定利润率,科学确定报价。     

天津开发区会展中心顶管施工技术

天津开发区会展中心排水工程,采用多刀盘土压平衡掘进机顶管技术,2 000 mm和2 200 mm四排管并排顶进,一次连续顶进284.5 m,累计顶进3 650 m。该技术应用,对管路控制满足设计和施工规范,对地表扰动小,同时取得了良好的经济及社会效益。     

信号设备微机监测装置的管理与维护

从安全管理方面提出了微机监测设备管理的具体措施。在维护管理方面细划为工区维护、车间维护和段机维护，并说明其具体要求。     

New Model and Simulation of Condenser for Ship Nuclear Power Plant

A new reasonably perfect dynamic mathematic model has been established for condenser used in ship nuclear powerplant according to its structural features and Operating principle. The model has been solved by the Runge-Kutta method. Andan analysis program has been developed for dynamic numerical simulation under steady operation condition, disturbance condi-tion, and accident condition. The dynamic characteristics of condenser has been calculated and analyzed under several kinds of     

线性系统单位门函数响应的试验测定

杜氏变换以单位门函数响应ρ_T(t)作为线性系统的固有属性,用来描述系统的动态特性.当实际线性系统的数学模型较复杂时,则可直接利用本文提出的试验测定方法(门函数响应测试法和统计相关测试法)来确定其单位门函数响应.     

灌河口海域潮波数值模拟

本文对三维潮波模型进行垂向积分后获得的二维潮波模型采用ADI方法建立了差分方程,并计算了灌河口海域潮波模型的数值解,得到了与实际观测符合良好的结果。从而根据数值模拟和实测的结果,对灌河口海区的潮汐和潮流进行了讨论,为灌河口海区工程应用及环境保护提供了参考的依据。