A comparative study of Multi-Objective Ant Colony Optimization algorithms for the Time and Space Assembly Line Balancing Problem

Assembly lines for mass manufacturing incrementally build production items by performing tasks on them while flowing between workstations. The configuration of an assembly line consists of assigning tasks to different workstations in order to optimize its operation subject to certain constraints such as the precedence relationships between the tasks. The operation of an assembly line can be optimized by minimizing two conflicting objectives, namely the number of workstations and the physical area these require. This configuration problem is an instance of the TSALBP, which is commonly found in the automotive industry. It is a hard combinatorial optimization problem to which finding the optimum solution might be infeasible or even impossible, but finding a good solution is still of great value to managers configuring the line. We adapt eight different Multi-Objective Ant Colony Optimization (MOACO) algorithms and compare their performance on ten well-known problem instances to solve such a complex problem. Experiments under different modalities show that the commonly used heuristic functions deteriorate the performance of the algorithms in time-limited scenarios due to the added computational cost. Moreover, even neglecting such a cost, the algorithms achieve a better performance without such heuristic functions. The algorithms are ranked according to three multi-objective indicators and the differences between the top-4 are further reviewed using statistical significance tests. Additionally, these four best performing MOACO algorithms are favourably compared with the Infeasibility Driven Evolutionary Algorithm (IDEA) designed specifically for industrial optimization problems.     

人工智能技术在机器人运动规划中的应用

机器人的运动规划问题是机器人学和人工智能中的一个重要课题。总结了国内外在机器人运动规划领域的一些典型算法,讨论了各种人工智能技术在运动规划中的应用,介绍了在空间机器人运动规划课题研究中的一些成果。     

图像处理中模糊算法问题的分析

图像处理是计算机常用技术之一,模糊算法的运用有助于提高图像处理的效果。传统图像处理存在诸多弊端,影响了用户获取信息的便捷性。本文分析了图像处理的基本操作内容,并阐述了模糊算法在图像处理流程中的运用,以进一步提升原始图像处理的效果。     

On the performance of self-organizing maps for the non-Euclidean Traveling Salesman Problem in the polygonal domain

In this paper, two state-of-the-art algorithms for the Traveling Salesman Problem (TSP) are examined in the multi-goal path planning problem motivated by inspection planning in the polygonal domain W. Both algorithms are based on the self-organizing map (SOM) for which an application in W is not typical. The first is Somhom’s algorithm, and the second is the Co-adaptive net. These algorithms are augmented by a simple approximation of the shortest path among obstacles in W. Moreover, the competitive and cooperative rules are modified by recent adaptation rules for the Euclidean TSP, and by proposed enhancements to improve the algorithms’ performance in the non-Euclidean TSP. Based on the modifications, two new variants of the algorithms are proposed that reduce the required computational time of their predecessors by an order of magnitude, therefore making SOM more competitive with combinatorial heuristics. The results show how SOM approaches can be used in the polygonal domain so they can provide additional features over the classical combinatorial approaches based on the complete visibility graph.     

Clarifying the semantics of value in use cases through Jackson's Problem Frames

Use cases constitute a popular technique to problem analysis, partly due to their focus on thinking in terms of the user needs. However this is not a guarantee for discovering all the subproblems that compose the structure of a given software problem. Moreover, a rigorous application of the technique requires a previous consensus about the meaning of I. Jacobson's statement “a use case must give a measurable value to a particular actor” (The Rational Edge, March 2003). This paper proposes a particular characterisation of the concept of “value” with the purpose of problem structuring. To this aim we base on the catalogue of frames for real software problems proposed by M. Jackson (Problem Frames, 2001) and we reason about what could be valuable for the user on each problem class. We illustrate our technique with the analysis of a web auction problem.     

人居互动中室内空间形态的情感化表达

人是当今环境的主角,随着现代人居空间设计的思路逐渐向关怀人文尺度转变,文章通过对室内空间形态和人文意识转换过程的研究,将重点放在人居互动的情感表达方面,人和空间通过不同的认知、情感、互动体验实现有意义的对话关系,通过人性化、智能化、功能化几个方面来分析人居互动中是如何达到满足人们行为需求的设计,最终做出具有丰富情感关怀的设计。     

Information sharing as enabler for the virtual team: an experimental approach to assessing the role of electronic mail in disintermediation

Abstract. This paper is an attempt to document empirically the relation between information sharing accomplished via electronic mail and the performance of teams. We report on an experimental study of the role of electronic mail in the operation of supply chains. A variation of the well known 'Beer Game' role-playing simulation game was computerized and implemented in an internet-based environment to study the information-sharing behaviour of teams. A total of 76 teams of four players each competed to achieve best net team profit. Results of the simulation game permit a detailed examination of email use in an organizational context. Findings indicate the expected significant correlation between email use to share information up the supply chain and net team profit. In other words, sharing information in the team has a positive impact on performance. The recorded behaviour of managers in the online simulation indicates that team members use electronic mail successfully to attempt disintermediation of the supply chain. When information is shared online, teams perform significantly better.     

Mediating team effectiveness in the context of collaborative learning: The importance of team and task awareness

Learning teams in higher education executing a collaborative assignment are not always effective. To remedy this, there is a need to determine and understand the variables that influence team effectiveness. This study aimed at developing a conceptual framework, based on research in various contexts on team effectiveness and specifically team and task awareness. Core aspects of the framework were tested to establish its value for future experiments on influencing team effectiveness. Results confirmed the importance of shared mental models, and to some extent mutual performance monitoring for learning teams to become effective, but also of interpersonal trust as being conditional for building adequate shared mental models. Apart from the importance of team and task awareness for team effectiveness it showed that learning teams in higher education tend to be pragmatic by focusing primarily on task aspects of performance and not team aspects. Further steps have to be taken to validate this conceptual framework on team effectiveness.     

A parallel algorithm for detection of linear structures in satellite images

To enhance linear structures in a gray level image, local operations with an additive score are normally used. Here a multiplicative score is used instead which gives better results than the additive one. The problem of segmenting the image of the multiplicative score is then dealt with where the threshold value can be automatically selected. The experimental results on some satellite images are reported.     

Data structures for the distributed iterative solution of non-conventional finite element models

A class of specialised data structures designed for the distributed solution of non-conventional finite element formulations, which are equally effective when used in conjunction with conventional formulations, is presented. We begin by briefly discussing how the non-conventional finite element formulations being developed within the structural analysis group at IST [Freitas JAT, Almeida JPM, Pereira EMBR. Non-conventional formulations for the finite element method. Comput Mech 1999;23(5–6):488–501] lead to systems of equations that appear to be naturally suited for parallel processing, but we also recognise that to take full advantage of the characteristics of these systems – large dimension, non-overlapping block structure and sparsity – it is necessary to use appropriate data structures. The approach presented, which references the logical subdivisions of the system matrices, was designed to fulfil these objectives. Examples of parallel performance and efficiency on an homogeneous distributed platform are presented.     

一种基于超链接结构的向量空间模型改进算法

在基于向量空间模型的信息检索系统中,TF2IDF 算法被广泛的应用在基于关键字的信息检索中。然而,对于网页独特的超链接结构,需要有一种技术在表示网页内容的同时将与它相邻链接的网页内容考虑进去。本文分析了向量空间模型的实质,并找出了其精度低的原因,在传统模型基础上提出了一种基于网页超链接结构的向量空间模型改进算法。实验分析表明改进后的算法与原算法相比检索精确度提高了10 % ,在一定程度上改善了检索效果。     

Split-ST-OFDM: Using split processing to improve the performance of space-time OFDM over digital TV channels

A new space diversity scheme for frequency selective channels is proposed. Split-ST-OFDM makes use of split processing to improve the performance of regular ST-OFDM. The novel approach is shown to be more general than the case where the Hadamard transform is used to explore the multipath diversity inherent to the frequency selective channel. Computer simulations show large gains of the proposed scheme over regular ST-OFDM for the case of terrestrial digital TV channels, at the expense of a very low additional computational complexity.     

Recent developments in the theory of data structures

This paper surveys some of the recent theoretical work on data structures. Work employing abstract graph models is covered as well as work on specific structures such as arrays and string patterns. Also included is work treating algorithms on complex structures and proving properties of programs that manipulate such structures. The paper concludes with a section on results using program schemata models to compare the utility of various data structures.     

Investigating the Prevalence and Performance Correlates of Vertical Versus Shared Leadership in Emergent Software Development Teams

ABSTRACT

In this multi-disciplinary study involving 44 software development projects, we investigate how leadership types—vertical versus shared—impact team performance. The results of the study show that while vertical leadership was found to have a higher positive impact on team efficiency, shared leadership was found to have a higher positive impact on team innovation, and a balanced shared and vertical leadership was found to optimally impact team effectiveness.     

Contextualising collective efficacy in virtual team research: The essential role of collaborative technologies in the virtual team efficacy conceptual framework

One factor receiving contemporary interest from virtual team researchers is collective-level efficacy, that is, a team's shared belief in its collective abilities to work effectively. However, our understanding of this literature leads to two concerns. First, depending on traditional team-focused collective-level efficacy concepts conveys an indifferent view of technology that ignores decades of research explaining how virtual teams' reliance on collaborative technologies differentiates them from traditional teams. Second, the information systems literature has largely ignored the concept of collective-level efficacy in virtual team research. That collective-level efficacy is underexamined in IS research is disappointing, given the growing recognition (outside the IS literature) that it is crucial to virtual team success. This absence becomes even more concerning given that IS researchers developed the concept of virtual team efficacy (VTE) specifically for virtual team settings. Unlike collective-level efficacy measures designed for traditional team settings, VTE incorporates technology into its conceptual definition and the operationalization of its measurement indicators. Thus, it is a stronger predictor of virtual team outcomes. To demonstrate its importance to IS research, we used a deductive theory-driven approach to propose and empirically evaluate whether VTE indirectly acts on virtual team effectiveness through the critical concepts of trust and participants' perceptions of problems associated with the collaboration inhibitors of time difference, geographical separation, and cultural differences. This research contributes significantly to the literature by confirming VTE's relationship to important virtual team success factors and informing IS researchers about the appropriate choice of constructs when studying collective-level efficacy in virtual team settings.     

试议后Windows XP时代信息安全问题

就Windows XP的安全问题、停止Windows XP更新对信息安全的影响进行了分析,提出了解决问题的具体对策。     

材料肌理在展览空间中的应用

随着社会的进步,人们对生活环境品质的追求越来越高,环境艺术设计已不仅仅停留在空间、造型、色彩和光线上,肌理设计给视觉带来的美感逐渐成为设计领域关注的焦点。特别是在展览空间中,根据展览主题的不同,肌理的运用手法更为丰富。拓展材料肌理的表现力和应用范畴能极大地丰富展览空间设计的造型语言,创造出更加多姿多彩的展示空间形态。     

Effects of different parameters on the performance of a fiber polarimetric sensor for smart structure applications

Studies of the effects of various parameters like pre-stress, input azimuth, fiber turns etc. on the polarimetric fiber optic sensing system for smart structure applications are presented. The presence of the smart structure modifies the output characteristics of the highly birefringent fiber due to elastic properties of the structure. Experimental procedures are repeated for Single Mode and the bow-tie HiBi fibers with different optical configurations. Both carbon fiber reinforced (CFRP) and glass fiber reinforced (GFRP) specimens are studied in detail. These experimental evaluation clearly point out that the sensitivity of such embedded polarimetric sensors are affected by the above mentioned parameters. Hence these parameters are optimized for making the smart sensing systems with specific objectives. Keeping the modulated signal at the optimum sensitivity range for defect detection in the composite laminates will also be discussed in this paper.     

An application of the self-organizing map in the non-Euclidean Traveling Salesman Problem

An application of the self-organizing map (SOM) to the Traveling Salesman Problem (TSP) has been reported by many researchers, however these approaches are mainly focused on the Euclidean TSP variant. We consider the TSP as a problem formulation for the multi-goal path planning problem in which paths among obstacles have to be found. We apply a simple approximation of the shortest path that seems to be suitable for the SOM adaptation procedure. The approximation is based on a geometrical interpretation of SOM, where weights of neurons represent nodes that are placed in the polygonal domain. The approximation is verified in a set of real problems and experimental results show feasibility of the proposed approach for the SOM based solution of the non-Euclidean TSP.