133,340 research outputs found

    Set multi-covering via inclusion-exclusion

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    Set multi-covering is a generalization of the set covering problem where each element may need to be covered more than once and thus some subset in the given family of subsets may be picked several times for minimizing the number of sets to satisfy the coverage requirement. In this paper, we propose a family of exact algorithms for the set multi-covering problem based on the inclusion-exclusion principle. The presented ESMC (Exact Set Multi-Covering) algorithm takes O* ((2 t)n) time and O* ((t + 1)n) space where t is the maximum value in the coverage requirement set (The O* (f (n)) notation omits a p o l y log (f (n)) factor). We also propose the other three exact algorithms through different tradeoffs of the time and space complexities. To the best of our knowledge, this present paper is the first one to give exact algorithms for the set multi-covering problem with nontrivial time and space complexities. This paper can also be regarded as a generalization of the exact algorithm for the set covering problem given in [A. Björklund, T. Husfeldt, M. Koivisto, Set partitioning via inclusion-exclusion, SIAM Journal on Computing, in: FOCS 2006 (in press, special issue)]. © 2009 Elsevier B.V. All rights reserved.postprin

    Dynamic programming based algorithms for set multicover and multiset multicover problems

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    Given a universe N containing n elements and a collection of multisets or sets over N, the multiset multicover (MSMC) problem or the set multicover (SMC) problem is to cover all elements at least a number of times as specified in their coverage requirements with the minimum number of multisets or sets. In this paper, we give various exact algorithms for these two problems with or without constraints on the number of times a multiset or set may be chosen. First, we show that the MSMC without multiplicity constraints problem can be solved in O* ((b + 1)n | F |) time and polynomial space, where b is the maximum coverage requirement and | F | denotes the total number of given multisets over N. (The O* notation suppresses a factor polynomial in n.) To our knowledge, this is the first known exact algorithm for the MSMC without multiplicity constraints problem. Second, by combining dynamic programming and the inclusion-exclusion principle, we can exactly solve the SMC without multiplicity constraints problem in O ((b + 2)n) time. Compared with two recent results, in [Q.-S. Hua, Y. Wang, D. Yu, F.C.M. Lau, Set multi-covering via inclusion-exclusion, Theoretical Computer Science, 410 (38-40) (2009) 3882-3892] and [J. Nederlof, Inclusion exclusion for hard problems, Master Thesis, Utrecht University, The Netherlands, 2008], respectively, ours is the fastest exact algorithm for the SMC without multiplicity constraints problem. Finally, by directly using dynamic programming, we give the first known exact algorithm for the MSMC or the SMC with multiplicity constraints problem in O ((b + 1)n | F |) time and O* ((b + 1)n) space. This algorithm can also be easily adapted as a constructive algorithm for the MSMC without multiplicity constraints problem. © 2010 Elsevier B.V. All rights reserved.postprin

    Best practices for deploying digital games for personal empowerment and social inclusion

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    Digital games are being increasingly used in initiatives to promote personal empowerment and social inclusion (PESI) of disadvantaged groups through learning and participation. There is a lack of knowledge regarding best practices, however. The literature on game-based learning insufficiently addresses the process and context of game-based practice and the diversity of contexts and intermediaries involved in PESI work. This paper takes an important step in addressing this knowledge gap using literature review, case studies, and expert consultation. Based on our findings, we formulate a set of best practices for different stakeholders who wish to set up a project using digital games for PESI. The seven cases in point are projects that represent various application domains of empowerment and inclusion. Case studies were conducted using documentation and interviews, covering background and business case, game format/technology, user groups, usage context, and impact assessment. They provide insight into each case’s strengths and weaknesses, allowing a meta-analysis of the important features and challenges of using digital games for PESI. This analysis was extended and validated through discussion at two expert workshops. Our study shows that a substantial challenge lies in selecting or designing a digital game that strikes a balance between enjoyment, learning and usability for the given use context. The particular needs of the target group and those that help implement the digital game require a highly specific approach. Projects benefit from letting both intermediaries and target groups contribute to the game design and use context. Furthermore, there is a need for multi-dimensional support to facilitate the use and development of game-based practice. Integrating game use in the operation of formal and informal intermediary support organiszations increases the chances at reaching, teaching and empowering those at risk of exclusion. The teachers, caregivers and counsellors involved in the implementation of a game-based approach, in turn can be helped through documentation and training, in combination with structural support

    Finite random coverings of one-complexes and the Euler characteristic

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    This article presents an algebraic topology perspective on the problem of finding a complete coverage probability of a one dimensional domain XX by a random covering, and develops techniques applicable to the problem beyond the one dimensional case. In particular we obtain a general formula for the chance that a collection of finitely many compact connected random sets placed on XX has a union equal to XX. The result is derived under certain topological assumptions on the shape of the covering sets (the covering ought to be {\em good}, which holds if the diameter of the covering elements does not exceed a certain size), but no a priori requirements on their distribution. An upper bound for the coverage probability is also obtained as a consequence of the concentration inequality. The techniques rely on a formulation of the coverage criteria in terms of the Euler characteristic of the nerve complex associated to the random covering.Comment: 25 pages,2 figures; final published versio

    A methodology for the incorporation of social inclusion into transport policy

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    4-8 July 2004. Istanbul, Turke

    The Criminalisation of Migration in Europe: A State-of-the-Art of the Academic Literature and Research. CEPS Liberty and Security in Europe No. 61, October 2013

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    In the last 30 years, a clear trend has come to define modern immigration law and policy. A set of seemingly disparate developments concerning the constant reinforcement of border controls, tightening of conditions of entry, expanding capacities for detention and deportation and the proliferation of criminal sanctions for migration offences, accompanied by an anxiety on the part of the press, public and political establishment regarding migrant criminality can now be seen to form a definitive shift in the European Union towards the so-called ‘criminalisation of migration’. This paper aims to provide an overview of the ‘state-of-the-art’ in the academic literature and EU research on criminalisation of migration in Europe. It analyses three key manifestations of the so-called ‘crimmigration’ trend: discursive criminalisation; the use of criminal law for migration management; and immigrant detention, focusing both on developments in domestic legislation of EU member states but also the increasing conflation of mobility, crime and security which has accompanied EU integration. By identifying the trends, synergies and gaps in the scholarly approaches dealing with the criminalisation of migration, the paper seeks to provide a framework for on-going research under Work Package 8 of the FIDUCIA project

    A Review on Software Architectures for Heterogeneous Platforms

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    The increasing demands for computing performance have been a reality regardless of the requirements for smaller and more energy efficient devices. Throughout the years, the strategy adopted by industry was to increase the robustness of a single processor by increasing its clock frequency and mounting more transistors so more calculations could be executed. However, it is known that the physical limits of such processors are being reached, and one way to fulfill such increasing computing demands has been to adopt a strategy based on heterogeneous computing, i.e., using a heterogeneous platform containing more than one type of processor. This way, different types of tasks can be executed by processors that are specialized in them. Heterogeneous computing, however, poses a number of challenges to software engineering, especially in the architecture and deployment phases. In this paper, we conduct an empirical study that aims at discovering the state-of-the-art in software architecture for heterogeneous computing, with focus on deployment. We conduct a systematic mapping study that retrieved 28 studies, which were critically assessed to obtain an overview of the research field. We identified gaps and trends that can be used by both researchers and practitioners as guides to further investigate the topic

    Does Accessibility Planning address what matters? A review of current practice and practitioner perspectives

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    'Accessibility' has become commonplace in transport planning and as such there is a plethora of interpretations of what accessibility means, what constitutes a good measure of accessibility, and how this might be applied in practice. This paper presents an overview of approaches to measuring accessibility and presents a case study of Accessibility Planning in England — one approach to formalising the concept of accessibility. Results of semi-structured interviews with local authority officers are discussed to establish whether current approaches, allow their desired outcomes to be met. This approach demonstrates where there might be gaps between measured or modelled accessibility and the perceptions of the individuals. Findings suggest that while the process is deemed useful in raising the profile of accessibility issues, measures of accessibility do not necessarily easily translate into quantifying benefits of those improvements that are perceived by practitioners to improve accessibility and reduce transport disadvantage
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