编组站动态配流模型与算法研究

如何从众多的解体方案中选择有利方案 ,这是编组站动态配流所要解决的核心问题。本文在文献 [3 ]的基础上 ,运用组合数学原理构造方案树 ,提出最大可能剩余量概念 ,导出计算公式 ,并以此作为方案值控制树的生长 ,进而利用回溯算法搜索有利方案。这样 ,本文连同文献 [2 ]、[3 ]一起 ,为配流问题的全面解决提供了完整的思路和具体的计算方法     

Influence of microbubble diameter and distribution on frictional resistance reduction

Investigations into frictional resistance reduction by microbubbles were carried out using a two-dimensional channel. The flow velocity and the amount of air injected were varied, and the frictional resistance reduction was measured. The frictional resistance reduction increased with increasing mean void ratio. When the bubble diameter was changed, the influence on frictional resistance reduction was negligible. The influence of bubble distribution near a wall was also investigated. Although it is thought that the influence of microbubbles near a wall is large, further investigations are required. Received: February 6, 2002 / Accepted: April 30, 2002 Acknowledgments. This research was supported by a special research program of Toyo University, SR239 Research Committee of the Shipbuilding Research Association of Japan, and the Research Project on Smart Control of Turbulence. The authors express their sincere gratitude for these supports. Address correspondence to: H. Kato (kato@eng.toyo.ac.jp)     

新型双体船和三体船阻力性能研究

针对小水线面双体船(SWATH)的不足,提出了新型双体、三体船型.通过模型试验方法,对上述船型的阻力性能进行了研究.结果表明,新型三体船由于舯前首中体的设置使得阻力在一定的航速范围内大幅降低;新型双体和三体船型在阻力性能上较SWATH船表现出了一定的优越性.     

道碴清筛机挖掘阻力的试验研究

针对清筛机挖掘阻力的形成，对挖掘阻力中运碴阻力形成原因进行了分析．利用设计的试验装置对不同道碴条件下的道碴阻力进行了测试，并在测试数据的基础上，给出了修正挖掘阻力的计算公式     

运用线性兴波理论进行船型设计与改进

通过导出简化的兴波阻力理论公式,提出一种运用线性兴波阻力理论进行船型设计与改进的方法。实际应用结果显示,该方法对船型改进很有效,可供船型设计部门及人员应用。     

聚乙烯醇指示剂用于医院污水总余氯的测定

目的 探讨医院污水总余氯测定新指示剂的使用。方法 参考《铁道法规汇编》提供的方法，应用PVA(聚乙烯醇)作指示剂进行余氯测定。结果 对4组不同浓度的样品用淀粉和PVA作指示剂进行测定，浓度分别为7．39、9．51、5．56、12．47和7．43、9．47、5．54、12．51mg／L。结论 PVA(聚乙烯醇)作指示剂，精密度和准确度均满足要求，且稳定性优于淀粉指示剂，故可取代。     

多跨长联预应力混凝土连续箱梁桥的次轴力分析

悬臂浇筑施工的多跨长联连续箱梁桥,张拉合龙束,合龙束预加力压缩梁体产生轴向变形,合龙口一侧支座摩阻力会约束梁体轴向变形,故产生预加力次轴力。次轴力和次弯矩一样,是预应力次内力的一项,且次轴力一般体现为拉力。无论从抗裂还是从抗弯的角度看,次轴力是一种不利的内力,在设计时对它的忽略,将会产生工程隐患。以一座14跨悬臂浇筑施工的多跨长联预应力混凝土连续梁桥为背景,计算出各跨合龙束引起的次轴力。然后对次轴力产生的原理和分布特点,以及减小次轴力的措施进行了讨论。最后在规范的基础上,增加预加力次轴力的考虑项,给出多跨连续梁桥正截面抗弯设计、抗裂验算的修正公式。     

确定焊接反变形的数值模拟及规律分析

焊接接头附近局部的加热及冷却使被焊结构产生残余应力及角变形.目前在船厂精度控制中,通常采用构件焊接后对某些部位进行火工校正的方法来控制残余角变形.文章提供了另外一种有效控制结构残余角变形的方法:对结构焊前施加弹性的反向变形.利用热弹塑性有限元法来模拟结构的焊接过程,并对不同板厚、不同热源的结构分别进行数值模拟,最终确定焊接结构的弹性反变形规律:焊接前施加弹性反变形的结构在焊接后角变形趋于零.     

Fatigue design for plug/ring type gas welded joints of sts301l including welding residual stresses

This paper presents a fatigue design method for plug and ring type gas welded joints, which incorporates welding residual stress effects. A non-linear finite element analysis (FEA) was first performed to simulate the gas welding process. The numerically predicted residual stresses of the gas welds were then compared to experimental results measured using a hole drilling method. In order to evaluate the fatigue strength of the plug and ring type gas welded joints, a stress amplitude (σ _a ) _R taling the welding residual stress of the gas weld into account was introduced and is based on a modified Goodman equation incorporating the effect of the residual stress. Using the stress amplitude (σ _a ) _R , the ΔP-N _f relations obtained from fatigue tests for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged into (σ _a ) _R -N _f relations. It was found that the proposed stress amplitude (σ _a ) _R could provide a systematic and reasonable fatigue design criterion for the plug and ring type gas welded joints.     

高频振捣对道路工程混凝土结构物抗冻性影响的研究

为研究高频振捣对混凝土抗冻性的影响,采用先进的硬化混凝土气泡结构测试设备,通过测定硬化混凝土的气泡特征参数随高频振捣时间增加的变化情况,研究了高频振捣对混凝土抗冻性的影响规律。试验结果表明,经适当高频振捣后,虽然混凝土的含气量有较大损失,但其气泡比表面积增大,气泡间隔系数变化不大。随高频振捣时间的增加,硬化混凝土中气泡总数和小气泡数(直径小于120μm)会出现峰值,而后急剧减少。高频振捣的时间控制在合理范围内,有利于改善引气混凝土的气泡结构,不会对其抗冻性产生不利影响。