The dynamics of surge in compression systems

In air-compression systems, instabilities occur during operation close to their peak pressure-rise capability. However, the peak efficiency of a compression system lies close to this region of instability. A surge is a violent mode of instability where there is total breakdown of flow in the system and pressure-rise capability is lost drastically. Generally, all compression systems operate with a margin defined as the ‘surge margin’, and, consequently, system operational efficiency is lower. It is of interest to study compression-system surge to understand its dynamics in order to operate compression systems close to the instability for achieving high efficiency safely without encountering surge. Unsteady pressure data from a compression system, captured during surge oscillations, reveal many aspects of flow physics and are analysed to understand the surge dynamics of the system. A set of controlled experiments was conducted with a simple desktop experimental test set-up and essential aspects of surge dynamics have been characterised.     

The design of experiments when there are errors in all the variables

The Error-in-Variables Model (EVM) applies to a large class of problems in parameter estimation in which there is error in all the variables. This property makes it of more general applicability than the widely used technique of ordinary Least Squares. While there is a voluminous literature on EVM there is nothing on a general method for designing experiments when EVM applies. In this paper we present an extension of the concept of D-optimality to provide such a general method. It is illustrated by applying it to the estimation of copolymer reactivity ratios and to fitting an ellipse.     

公差-成本稳健性分析研究

 根据稳健设计的思想，提出了一种成本稳健性分析方法，以此来获得影响成本值及其稳健性的关键因素．首先研究了公差设计中成本模型的误差因素(不同的模型和模型参数的误差)，然后应用试验设计方法分析了这两类因素对成本最小值及其稳健性的影响，最后通过实例验证了本方法．     

软土地基水泥搅拌桩室内配合比试验分析

对广州南沙某工程软土地基搅拌桩室内不同配比的水泥土标准试件进行对比试验,研究软土地基搅拌桩施工中水泥、石膏等添加剂的最佳配比方案,对指导搅拌桩的现场施工有着重要的意义。     

Complementary modelling of fluid separation processes

Optimal functioning of numerous technological processes depends primarily on relevant process design, properly selected column internals and sufficient understanding of the process behaviour. This can be achieved only with the help of accurate and reliable process models capable of considering process rates in a rigorous way, with respect to both transport phenomena and chemistry. In this article, a new modelling concept called complementary modelling is suggested for a large class of fluid separation processes. Since the conditions and criteria for these processes vary considerably, it is impossible to develop a unified modelling approach. Instead, a reasonable and effective combination of different modelling approaches provides solutions to many present and future tasks. The complementary modelling is discussed in detail and illustrated with several case studies.     

基于模拟试验法的离散公差稳健设计

 在分析计算机辅助公差设计技术的研究现状的基础上，提出了基于模拟试验法的离散公差稳健设计方法．在该方法中将加工成本与质量损失作为两个独立的目标函数，从而建立离散公差优化设计模型，采用试验设计法和CP方法相结合的技术实现公差的稳健设计，最后用实例证明该方法的可行性．     

Upper-bound analysis of the pressure-assisted injection forging of thick-walled tubular components with hollow flanges

An upper-bound analysis of the pressure-assisted injection forging (PAIF) of thick-walled tubular components with hollow flanges was conducted to predict the maximum forming-pressure requirements. The polymeric pressurizing material and the pure aluminium work material employed were assumed to obey the von-Mises’ yield criterion, the two materials being divided into three and six zones, respectively, and described using kinematically admissible velocity fields. An upper-bound solution was derived based on this model. Experiments were conducted to validate the solution. The results suggest that the upper-bound analysis has sufficient accuracy for the prediction of the forming-pressure requirements. Subsequently, a parametric analysis was conducted to study the effects of variation of the principal parameters of the process and the geometry, such as tube thicknesses, flange dimensions and friction, on the forming-force requirements, which showed other useful applications of the upper-bound solutions.     

An Extended Replication of an Experiment for Assessing Methods for Software Requirements Inspections

We have performed an extended replication of the Porter-Votta-Basili experiment comparing the Scenario method and the Checklist method for inspecting requirements specifications using identical instruments. The experiment has been conducted in our educational context represented by a more general definition of a defect compared to the original defect list. Our study involving 24 undergraduate students manipulated three independent variables: detection method, requirements specification, and the order of the inspections. The dependent variable measured is the defect detection rate. We found the requirements specification inspected and not the detection method to be the most probable explanation for the variance in defect detection rate. This suggests that it is important to gather knowledge of how a requirements specification can convey an understandable view of the product and to adapt inspection methods accordingly. Contrary to the original experiment, we can not significantly support the superiority of the Scenario method. This is in accordance with a replication conducted by Fusaro, Lanubile and Visaggio, and might be explained by the lack of individual defect detection skill of our less experienced subjects.     

大潮差河口闸下水流的流动特性分析

福建数座河口水闸发生剧烈淘刷,闸上游和下游的最大冲刷深度达到闸室高度的0.5~1.2倍,且屡修屡毁。有的水闸经多次除险加固后,不得不再花巨资重建。通过数学模型和物理模型揭示了河口水闸下游水位因受东海大潮差海潮影响发生剧烈波动时的变化规律,发现了水闸泄流过程中的间歇性淹没及非常工况甚至出现逆流的独特流动现象,给出了典型日孔流及堰流泄流能力动态变化过程线,分析了消能工变化对闸址水流结构的显著影响,并对水闸水毁修复前后闸下冲刷进行了预测。结果表明:水闸修复前闸下涨急最高水位4.53 m,修复后下降0.67 m,水闸修复后逆流现象减弱。修复后首次水跃位置往上游移动了35 m,平均水跃高度下降47.46%,闸后及二级池末端最大流速2.27 m/s和0.08 m/s,较修复前分别下降了40.58%和96.48%。常遇泄流条件下,水闸的淹没度和泄流能力呈现不断变化的动态过程。当西溪水闸62#先启孔全开,上游保持正常高水位3.2 m,下游为最低潮位-0.72 m时,修复后最大冲刷深度减少64.48%,消能防冲效果十分明显。研究成果对河口水闸安全运行具有一定的参考价值。