Hybrid Model of High Speed Machining Centre Headstock

A hybrid high-speed machining centre headstock model based on two computation methods: the finite element method and the finite difference method is presented. The model allows one to calculate precisely the headstock's indices on the basis of which its optimal operating characteristics can be determined. The presented modelling methods allow one to evaluate a design from thermal, stiffness and durability points of view. By way of illustration, the behaviour of three machining centre headstocks with: an electrospindle on rolling bearings, a conventional spindle and an electrospindle on aerostatic bearings are modelled using the hybrid model.     

Changes in atmospheric corrosion rate caused by chloride ions depending on rain regime

Plain carbon steel and copper samples were exposed in two atmospheric test stations located in Havana, Cuba and Medellin, Colombia. Samples were submitted to accelerated outdoor test by intermittent spraying of a salt solution (SCAB test) according to ISO 11474:98.A remarkable difference in the acceleration rate of chloride ions for mild steel and copper between Cuban and Colombian stations was determined. Differences in rain amount and frequency between Havana and Medellin are noticeable. The influence of rain seems to be important in determining the acceleration rate of chloride ions on steel and copper due to its washing effect. A model for the influence of the interaction between rain characteristics and chloride deposition rate on mild steel and copper corrosion behaviour with time is proposed. Data fit very well to the proposed model. It is concluded that rain regime should be taken into account in order to determine the real acceleration rate caused by chloride ions in atmospheric conditions.     

Modelling of Material Side Flow in Hard Turning

In this paper an attempt has been made to model the material side flow generated during hard turning operation. A three dimensional thermo elasto-viscoplastic finite element model is presented. The model incorporates cutting tools with different nose radii and cutting conditions. The model was also used to investigate the effect of different process parameters on the extent of material side flow. The predicted results revealed that more side flow is generated when higher nose radius is used. A similar observation is noted when lower feed is used. The simulated results agreed well with the experimentally examined machined surface, viewed with a scanning electron microscope.     

Modelling of a dual circuit induced draft cooling water system for control and optimisation purposes

The successful operation of any petrochemical plant is dependent on the use of several utilities which may include electricity, steam, compressed air, cooling media, refrigeration media, nitrogen, condensate and fuel gas. These utilities form a significant portion of the fixed cost associated with running a plant. Utility optimisation has not received much attention until recently, driven by rising energy costs, stricter environmental policies, more competitive markets, and the threat of climate change. The generation, preparation, and transportation of utilities require energy and therefore should be optimised to reduce losses and improve operating efficiency. One example of such a utility is a cooling water system. This paper describes the modelling of a dual circuit induced draft cooling water system for control and optimisation purposes. The derived model is verified with plant data indicating promising results. The model is represented in a steady-state algebraic form as well as a dynamic state-space form. This provides a convenient basis for simulation studies and controller/optimiser design.     

Real-Time Reflexion Modelling in architecture reconciliation: A multi case study

ContextReflexion Modelling is considered one of the more successful approaches to architecture reconciliation. Empirical studies strongly suggest that professional developers involved in real-life industrial projects find the information provided by variants of this approach useful and insightful, but the degree to which it resolves architecture conformance issues is still unclear.ObjectiveThis paper aims to assess the level of architecture conformance achieved by professional architects using Reflexion Modelling, and to determine how the approach could be extended to improve its suitability for this task.MethodAn in vivo, multi-case-study protocol was adopted across five software systems, from four different financial services organizations. Think-aloud, video-tape and interview data from professional architects involved in Reflexion Modelling sessions were analysed qualitatively.ResultsThis study showed that (at least) four months after the Reflexion Modelling sessions less than 50% of the architectural violations identified were removed. The majority of participants who did remove violations favoured changes to the architectural model rather than to the code. Participants seemed to work off two specific architectural templates, and interactively explored their architectural model to focus in on the causes of violations, and to assess the ramifications of potential code changes. They expressed a desire for dependency analysis beyond static-source-code analysis and scalable visualizations.ConclusionThe findings support several interesting usage-in-practice traits, previously hinted at in the literature. These include (1) the iterative analysis of systems through Reflexion models, as a precursor to possible code change or as a focusing mechanism to identify the location of architecture conformance issues, (2) the extension of the approach with respect to dependency analysis of software systems and architectural modelling templates, (3) improved visualization support and (4) the insight that identification of architectural violations in itself does not lead to their removal in the majority of instances.     

A supply network-modelling system for a small- to medium-sized manufacturing company

During the late 1990s and early 2000s, the profile of global manufacturing has experienced many changes. There is anecdotal evidence that many western manufacturing companies have chosen to expand their manufacturing base across geographical boundaries. The common reasons sited for these ventures are to exploit less expensive labour markets, to establish a presence in expanding markets and in response to the threat of new competition. Whilst a global manufacturing base can prove to have many cost and sales benefits, there are also many disadvantages. Logistics operations can often increase in complexity leading to higher reliance on planning and effective interpretation of demand data. In response, systems modelling has remerged as a fertile research area after many years. Many modelling and simulation techniques have been developed, but these have had very limited practical success. The authors have identified that majority of these simulation techniques rely upon a detailed market structure being known, when this is rarely the case. This paper describes the outcome of a research project to develop of a pragmatic set of tools to gather, assess and verify supply chain structure data. A hybrid collection of technologies are utilised to assist these operations and to build a dynamic supply network model.     

Modelling user experience with web sites: Usability, hedonic value, beauty and goodness

Recent research into user experience has identified the need for a theoretical model to build cumulative knowledge in research addressing how the overall quality or ‘goodness’ of an interactive product is formed. An experiment tested and extended Hassenzahl’s model of aesthetic experience. The study used a 2 × 2 × (2) experimental design with three factors: principles of screen design, principles for organizing information on a web page and experience of using a web site. Dependent variables included hedonic perceptions and evaluations of a web site as well as measures of task performance, navigation behaviour and mental effort. Measures, except Beauty, were sensitive to manipulation of web design. Beauty was influenced by hedonic attributes (identification and stimulation), but Goodness by both hedonic and pragmatic (user-perceived usability) attributes as well as task performance and mental effort. Hedonic quality was more stable with experience of web-site use than pragmatic quality and Beauty was more stable than Goodness.     

Decentralised control of chromatographic simulated moving bed processes based on wave front reconstruction

The behaviour of chromatographic simulated moving bed processes is described by the movement of concentration profiles through a circle of separation columns. A closed-loop control manipulates the profiles in order to meet demands concerning specified product purity and disturbance attenuation. If steep wave fronts of the concentration profiles occur, the controlled variables undergo fast changes in case of a transient of the process. In this case, a reconstruction of the wave fronts is necessary for a successful control.A simple and effective decentralised controller structure is proposed based on cascaded discrete-time PI controllers. On-line product purity measurements and the reconstructed wave fronts are used for control purposes. Two kinds of process models are used: a rigorous model for dynamic simulations, and strongly simplified plant models for the design of the wave front reconstruction and the controller. The latter models are identified based on experimental step tests with the reference plant and numerical simulations. The performance of the control system is evaluated by numerical simulations.     

基于Petri网的联锁软件测评仿真建模

车站联锁软件一直有着严格的测试要求,仿真模块是软件测试的重要组成部分,Petri网作为形式化语言的一种,有着准确与完备的特点,对于联锁软件这类安全苛求软件的测试尤为适合,提出了一种使用Petri网对联锁软件测试中仿真模块建模的方式,并分别给出了用基本Petri网和有色Petri网的2个建模实例.该模型有助于提高铁路联锁软件测试系统的安全性与精确性.     

基于Web的虚拟物流实验室设计与实现

通过对虚拟物流实验室设计特点的分析,提出了基于Web的虚拟物流实验室构架,并设计了实现方案.运用3D 软件结合VRML建立虚拟场景模型,通过Java 3D对模型文件的调用实现虚拟场景的构建.调用Java 3D类库实现场景漫游、人机交互等功能,并对虚拟模型进行优化、重组.最后建立一个虚拟实验室的场景实例,验证了该设计方法具有良好的开发效率以及系统的沉浸性与交互性.