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.     

三方会谈:感知海事风云变幻

2005年10月31日～11月1日;;由全球船厂、船东、船级社共同参与的第5次三方对话在北京举行。今年的“三方会议”已是第2次在中国召开;;与会的国内外海事界精英共有80余人;;会谈内容涉及了船厂、船东和船级社共同利益范围内的广泛事宜。我们不仅在此听到了来自亚洲造船强国的声音,而且看到了利益各方对目前一些热门海事话题的见解。当三股力量汇聚一堂的时候,分歧、误解被弱化,经验、教训被分享,在谋求共同利益的远景目标下,“三方会议”正将一个团结繁荣的海事界展现在世人的面前,同时,它也在见证着海事繁荣期的种种变局。     

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     

基于FPGA的伪码测距电路设计

介绍伪随机码的性质，将伪随机码用于无线电测距中。采用滑动相关法实现伪随机码的捕获，并给出捕获电路的原理和仿真结果。用脉冲计数法实现捕获完成后的两组伪随机码相位差的精确测量。在FPGA芯片EPIC3T144C8进行硬件验证，结果表明该电路可以文现2．5ns的测时精度。     

对巷道变形、破坏及支护的探讨

针对甘肃金川一矿区矿井下采用喷锚网联合支护的矮墙半圆拱断面巷道的变形、破坏特点,结合金川地应力状况,分析了矮墙半圆拱巷道的应力分布特点、变形、破坏原因,并提出相应措施,并取得了良好的效果。     

可口可乐、AD钙奶等食品中常见防腐剂测定

样品前处理采用传统的液-液萃取。样品酸化后用乙醇提取,取上清液进样分析。使用日本岛津公司2010型气相色谱仪,氢火焰离子化检测器(FID)可测得五种防腐剂的平均回收率为98.63%(n=3),平均相对标准偏差小于3%,标准曲线的线性回归系数也均在0.9918以上。仪器稳定性好,重现性也能够满足分析实验的要求。     

超级电容器在直流电力系统中应用研究

本文介绍了以超级电容器作为储能元件的储能系统在直流电力系统中的应用.通过对储能系统运行状态的分析,给出了储能系统中各主要元件取值的计算方法,并利用SimPlorer6.0对所介绍的系统进行了仿真,仿真结果验证了分析的正确性.