Modelling the dynamics of the tilt-casting process and the effect of the mould design on the casting quality

All titanium alloys are highly reactive in the molten condition and so are usually melted in a water-cooled copper crucible to avoid contamination using processes such as Induction Skull Melting (ISM). These provide only limited superheat which, coupled with the surface turbulence inherent in most conventional mould filling processes, results in entrainment defects such as bubbles in the castings. To overcome these problems, a novel tilt-casting process has been developed in which the mould is attached directly to the ISM crucible holding the melt and the two are then rotated together to achieve a tranquil transfer of the metal into the mould. From the modelling point of view, this process involves complex three-phase flow, heat transfer and solidification. In this paper, the development of a numerical model of the tilt-casting process is presented featuring several novel algorithm developments introduced into a general CFD package (PHYSICA) to model the complex dynamic interaction of the liquid metal and melting atmosphere. These developments relate to the front tracking and heat transfer representations and to a casting-specific adaptation of the turbulence model to account for an advancing solid front. Calculations have been performed for a 0.4 m long turbine blade cast in a titanium aluminide alloy using different mould designs. It is shown that the feeder/basin configuration has a crucial influence on the casting quality. The computational results are validated against actual castings and are used to support an experimental programme. Although fluid flow and heat transfer are inseparable in a casting, the emphasis in this paper will be on the fluid dynamics of mould filling and its influence on cast quality rather than heat transfer and solidification which has been reported elsewhere.     

Robotics in the factory of the future Role of Robots in the Factory of the Future

Robots represent a flexible source of automation in a variety of manufacturing processes today. As a result of this, robots are being increasingly used as an alternative for automation in a large number of manufacturing concerns. The present trend has been to link these islands of automation together with efficient material handling and computer control to attain to totally automated environment, what is commonly referred to as the “Factory of the Future”. This paper discusses the role of robots in such a factory and draws upon a case study to illustrate the varied aspects that one deals with in robotization in such an environment.     

VMware的技术与应用探析

虚拟化技术是当今服务器技术的一个主流方向,也是一项在计算机领域具有革命性意义的技术.作为x86架构体系下虚拟化技术的领军者-VMware,在技术上有其独到之处.研究VMware的技术与应用,对探知其优秀的技术特点,了解其成熟的产品体系有着现实意义.     

Study of the response of the area of the palm to impact: Relationship between the physical characteristic of the palm impact and the subject perception of the severity of the palm impact

Even though using the hand as a hammer causes injury, the practice continues, and may be increasing, in industry and in jobs that require intensive manual labor. This was an exploratory study aimed at measuring the relationships between the forces of strikes, the relative angles of strikes, and/or the number of strikes (up to 3) with the perception of severity of strikes when using the base of the palm of the hand. Eight subjects struck a metal force plate with the base of the palm of the hand at three levels of force, three levels of angle with respect to the surface of a force plate, and with three different numbers of times in a trial. Subjects were then asked to give a psychophysical rating after each trial. The subjective perception of the severity of each impact and force-time curves were recorded. From each force-time curve, peak force, maximum acceleration of force application, and the area of the force curve from initiation to peak were determined. Sixteen ANOVA models were analyzed.     

A survey of the state of the art in learning the kernels

In recent years, the machine learning community has witnessed a tremendous growth in the development of kernel-based learning algorithms. However, the performance of this class of algorithms greatly depends on the choice of the kernel function. Kernel function implicitly represents the inner product between a pair of points of a dataset in a higher dimensional space. This inner product amounts to the similarity between points and provides a solid foundation for nonlinear analysis in kernel-based learning algorithms. The most important challenge in kernel-based learning is the selection of an appropriate kernel for a given dataset. To remedy this problem, algorithms to learn the kernel have recently been proposed. These methods formulate a learning algorithm that finds an optimal kernel for a given dataset. In this paper, we present an overview of these algorithms and provide a comparison of various approaches to find an optimal kernel. Furthermore, a list of pivotal issues that lead to efficient design of such algorithms will be presented.     

Microsystems the Microprocessor in the Biological Laboratory

The use of microprocessors in the biological laboratory is a logical result of the evolution of computer use in the biomedical sciences. In 1963, H. K. Hartline and Floyd Ratliff, working at Rockefeller University in New York City, hooked up a CDC 160A computer as a generalpurpose laboratory instrument for data acquisition during their experiments on vision.¹For stimulus control, they used a digital programmer constructed from commercially available discrete transistor logic circuits.²The work in the Hartline-Ratliff laboratory was a continuation of earlier work done by Hartline on inhibitory interaction in the horseshoe crab's eye, for which Hartline shared the Nobel Prize for Physiology and Medicine in 1966, with Wald and Granit.³     

加强机房全面管理 提高机房使用效益

要提高高校机房的使用效益,必须加强机房的管理。在多年的工作实践中,针对加强机房管理的规范化、科学化、信息化建设,总结出一套行之有效的管理方法,保证了机房较高的利用率,提高了机房使用效益。     

巴洛克时代:世界艺术史上的黄金时期

文章对巴洛克艺术风格进行了简单的介绍,此风格对各个艺术层面的影响深远。在绘画,建筑,园林等方面都发挥了重大作用。巴洛克文化为世界艺术发展画上了浓墨重彩的一笔,对后世产生了巨大的影响。在文章中,具体介绍了巴洛克文化在不同方面的历史成就,这些成就都是人类艺术史上的瑰宝。     

浅谈多媒体教学的优势与存在的问题

多媒体现已在教学过程中得到了广泛的应用,但由于这种教学方式是一个新生事物,因此它在给教学带来新的理念的同时,也暴露了相当大的弊端。该文针对现阶段多媒体教学的优势及存在的问题进行了探讨。     

视觉传达设计中的传统之“意”、时尚之“境”

中国的视觉传达设计要想健康发展,必须汲取中国文化元素的营养,形成"有中国特色"的设计风格。中国传统图形元素在当今视觉传达设计中已经不再是单一的图形表现,漫漫衍生为一种形式,一种手法,它成为视觉传达设计中具有巨大生命力和感染力的一种设计元素。     

Using dynamic user models in the recognition of the plans of the user

This paper is concerned with information-seeking dialogues in a restricted domain (we consider a consultation system for a Computer Science Department, delivering information about the various tasks that the users may want to perform: for example, how to access the library, get information about the courses of the Department, etc.) and presents a framework where a plan recognition and a user modeling component are integrated to cooperate in the task of identifying the user's plans and goals. The focus of the paper is centered on the techniques used for building the user model and exploiting it in the determination of the user's intentions. For this task, we use stereotypes and we propose some inference rules for expanding the user model by inferring the user's beliefs from both the sentences s/he utters and the information stored in the plan library of the system, that describes the actions in the domain. Moreover, we introduce some disambiguation rules that are applied to the information in the user model for restricting the set of ambiguous hypotheses on the user's plans and goals to the most plausible ones. This also simplifies a further clarification dialogue if it is necessary for a precise identification of the user's intentions.     

Between the crystalline and the chaotic

This short feature documents elements of research in advance of a long-term work. Rather than a technical account or retrospective, the aim is to demonstrate by example how research itself is a primary process, illustrated by work carried out at the Institute of Creative Technologies (IOCT) during the last few years. When creative output is appraised only from its visible results, something is lost in the telling; carefully selected public facets rarely convey the depths of the underlying lines of inquiry. The research covered is for a work that generates quantitative data, driving visualisations of human movement, proximity and orientation. The aim is to reveal how these literal data reflect our relationships to one another in social settings. To contextualise the current process, complex systems, dynamic pattern formation and other works are also mentioned. As a personal account, it seemed appropriate to supplement the usual academic passive voice with first-person narrative.     

语料库中熟语的标记问题

熟语是自然语言中普遍存在的语言现象。本文分析了国内现有语料库对熟语的标注方式,发现这种方式对语料库的进一步加工是有问题的。为了在语料库标注阶段把熟语问题处理好,本文从信息处理的角度将熟语中的成语、惯用语、歇后语、习用语、专门语以及缩略语归为固定语的范畴,进而提出根据固定语的语法功能给定词性标记,再根据它们的词汇特征给定词汇范畴标记的双层标记法,这样在一定程度上解决了熟语的语料库标注问题。     

Evaluation of the genetic algorithm performance for the optimization of the grand potential in the cluster variation method

Due to the importance of phase diagrams in a wide range of material based industries, additional efforts should be dedicated to their elaboration techniques. The cluster variation method is a promising technique to model the entropy within different plane lattices and is recognized by the materials physics community as a powerful modeling framework. Motivated by the efficiency of genetic algorithms in solving numerous types of optimization problems, our aim in this work is to investigate their performance in minimizing the grand potential in the context of the cluster variation method. A comparison is conducted with respect to numerical iterative techniques namely the Newton-Raphson and natural iteration methods, where many performance criteria are computed and compared. The obtained results allow the ranking of the considered approaches according to their performance measures and suggest a more profound investigation of metaheuristics particularly for complicated cluster structures in the future.     

Using the theory of the professions to understand the IS identity crisis

Academic information systems (IS) is struggling with an identity crisis that is grounded in limited consensus about the discipline's core concepts, its important research questions and its boundaries. The result is a pluralistic discipline that has triggered an ongoing debate about whether the ‘liquidity’ characteristic of IS is a natural consequence of rapidly changing technologies or if it is indicative of a chaotic state that is unsustainable. This paper looks at IS through a new and different lens by using the theory of the professions to gain insight into current and heretofore unidentified problems facing the discipline. Casting IS as a profession presents an integrated view of academic IS, IS practice and IS education grounded in a framework that explores connections among these three elements. The paper concludes with a discussion of the processes by which professions evolve and likely consequences for IS research, practice and education.     

提升校园信息化水平

提升校园信息化水平是目前我国高校信息化发展面临的重要课题。提升信息化水平是培养高素质人才的需要;是开展高水平教学、科研活动的需要;是提高教学管理水平和效率的需要。“数字校园”的核心是“一个基础平台、一个门户和N个应用”     

以加盟商的视角谈品牌服装的商品组合

以品牌为主导的国内服装产业,目前正在以品牌特许经营的方式,在中国服装市场上到处建设销售网络。同时,作为拥有一定知名度和市场占有率的品牌服装,订货也由最初的代理制转变为买断制,这就给加盟商带来了一定程度的压力和风险,因此作为加盟商如何组织自己的商品组合就变得十分重要,本文将站在加盟商的角度,对商品组合的构成进行详细的分析,以希望能在提升品牌形象的基础上实现利益的最大化。     

Present-ing the user: constructing the persona

Abstract

During the last few years personas has become an established design technique within the IT-design field. Using personas has proven itself as a valuable approach for designers to switch between a developer's perspective and a user's perspectivein the design process. The technique is claimed to help designers in keeping a clear focus and shaping a consistent user-interface by making ‘the user’ present in the design work. In this paper we report on a number of projects where we have elaborated on the persona approach for collaborative design. With the goalof creating ‘user presence’ in the design process, we have developed an approach building on a combination of ethnographic exploration, participatory inquiry, and collaborative design. This paper carries two interrelated points: the grounding of personasin existing practice; and the notion that ‘the user’ is created as an ongoing process throughout the design work.     

Computing the Treewidth and the Minimum Fill-In with the Modular Decomposition

Using the notion of modular decomposition we extend the class of graphs on which both the treewidth and the minimum fill-in can be solved in polynomial time. We show that if C is a class of graphs that are modularly decomposable into graphs that have a polynomial number of minimal separators, or graphs formed by adding a matching between two cliques, then both the treewidth and the minimum fill-in on C can be solved in polynomial time. For the graphs that are modular decomposable into cycles we give algorithms that use respectively O(n) and O(n3) time for treewidth and minimum fill-in.     

Exhuming the criticism of the logicist

McDermott has recently explained his fundamental philosophical shift on the methodology of artificial intelligence (AI) and has further suggested that the shift is both necessary and inevitable. The shift results from a perception that a trend towards overformalisation has detached the real problems from the research results. McDermott's criticism is an enlightened exhumation of the criticisms of the seventies and explains new ways in which the logical methodology can be abused. I argue that McDermott's criticism should not discourage the use of logic, but force a timely reexamination of its fundamental role in AI.