Evaluation of stress intensity factors for multiple surface cracks in bi-material tubes

This paper presents stress intensity factors (SIFs) of multiple semi-elliptical surface cracks in bi-material tubes subjected to internal pressure by boundary element method. In this case the water-tube boiler with oxide scale formed on the inner surface due to prolonged exposure at elevated temperature is considered as the bi-material tubes. Variations of modulus of elasticity and thickness for the oxide scale are used to evaluate their effects on the stress intensity factors. The increasing of thickness of the oxide scale causes decreasing values of the normalized stress intensity factor as the modulus of elasticity for the oxide scale is greater than that of the tube metal. Conversely, if the modulus of elasticity for the oxide scale is smaller, the increasing of thickness of the scale would also give increasing values of the normalized stress intensity factor.     

Seismic Behavior of Flexural Dominated Reinforced Concrete Bridge Columns at Low Temperatures

This paper presents the results from Phase II of an experimental study on the behavior of reinforced concrete bridge columns in cold seismicly active regions. Six half-scale circular reinforced concrete columns, designed to be flexural dominated, were tested under reversed cyclic loading while subjected to temperatures ranging from ?36°C (?33°F) to 22°C (72°F). Four of the units tested were reinforced concrete filled steel tube (RCFST) columns and the other two were ordinary reinforced concrete columns. Results obtained reiterated the observations made in Phase I, which is that low temperatures cause an increase in the flexural strength and initial stiffness as well as a reduction in the spread of plasticity and displacement capacity of the column. Another important observation made was that the plastic hinge length is drastically reduced in the RCFST units compromising the displacement capacity of this type of column even at room temperature conditions. Current predictive models were revised and modified to account for the low-temperature effect.     

A branch and bound enhanced genetic algorithm for scheduling a flowline manufacturing cell with sequence dependent family setup times

This paper addresses the permutation flowline manufacturing cell with sequence dependent family setup times problem with the objective to minimize the makespan criterion. We develop a cooperative approach including a genetic algorithm and a branch and bound procedure. The latter is probabilistically integrated in the genetic algorithm in order to enhance the current solution. Moreover, the application of the branch and bound algorithm is based upon the decomposition of the problem into subproblems. The performance of the proposed method is tested by numerical experiments on a large number of representative problems.     

一种星形件支臂端结构的改进

某型直升机在长时间使用过程中，星形件支臂端衬套经常出现松动，这里介绍了该型直升机星形件支臂端衬套出现松动的原因，提出了结构改进措施。     

挤扩支盘桩基的设计与应用

本文介绍了福建省防震减灾指挥中心桩基础的选型及设计,分析了该工程挤扩支盘桩的承载力及其沉降,同时对该桩型的经济性作了简单比较。     

现代江南城市中“河-路”空间关系的分析与评价--以苏州市为例

河道与道路空间是构成江南古城镇空间构架的基础,近年来传统河街空间关系瓦解,城市中河道与道路的紧密联系丧失。课题以苏州地区为样本,将现代江南城市中“河路”空间关系归纳为：“路近河”“路临河”“路夹河”“路跨河”“河路背离”几种空间类型。传统河路空间关系已不适应现代城市发展需要,应对错位的河路空间关系进行修复,最大限度地恢复河道与道路的空间关联,由此再现传统江南水乡特色空间形态。     

照明配电末端分支回路导体截面的选择

针对现行照明配电设计中末端分支回路导体截面的选择普遍偏大问题,结合有关规范标准．对与导体截面选择有关的各因素进行分析,提出在绝大多数情况下,将照明配电末端分支回路绝缘铜导体截面从2．5mm^2改为1．5mm^2,可以节约大量的铜材．是符合节能减排原则的举措。     

LTb电梯系统运行参数分析及工程应用

LTb电梯是在高层建筑物中新近开始研究和应用的一种新梯种．有广阔应用前景。本文对LTb电梯系统运行参数在大楼各层相同和各层不同条件下．用统计分析方法分别证明了其可能停站概率忍用单轿厢可能停站数fi和服务楼层数n的表示公式,并进一步提出和证明了用轿厢乘客人数r和服务楼层数n表示的公式;阐述了上述公式的工程应用;并给出了LTb电梯和其他多轿厢电梯的的使用比较例。     

Development and validation of a micro-fin tubes evaporator model using R134a and R1234yf as working fluids

This paper presents a model of shell and tube evaporator with micro-fin tubes using R1234yf and R134a. The model developed for this evaporator uses the ε-NTU method to predict the evaporating pressure, the refrigerant outlet enthalpy and the outlet temperature of the secondary fluid. The model accuracy is evaluated using different two-phase flow boiling correlations for micro-fin tubes and comparing predicted and experimental data. The experimental tests were carried out for a wide range of operating conditions using R134a and R1234yf as working fluids. The predicted parameter with maximum deviations, between the predicted and experimental data, is the evaporating pressure. The correlation of Akhavan– Behabadi et al. was used to predict flow boiling heat transfer, with an error on cooling capacity prediction below 5%. Simulations, carried out with this validated model, show that the overall heat transfer coefficient of R1234yf has a maximum decrease of 10% compared with R134a.     

Bi criteria flexible assembly line design problem with equipment decisions

In this paper, we address the assembly line balancing and design problem of assigning tasks and equipment to work stations where there are several equipment alternatives for each task. We consider minimizing the total equipment cost and the number of work stations criteria. We aim to generate efficient solutions with respect to these criteria and propose a branch and bound algorithm whose efficiency is enhanced with powerful reduction and bounding mechanisms. We find that our algorithm is capable of solving problem instances with up to 25 tasks and five pieces of equipment.