236,762 research outputs found

    A 5-Approximation for Universal Facility Location

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    In this paper, we propose and analyze a local search algorithm for the Universal facility location problem. Our algorithm improves the approximation ratio of this problem from 5.83, given by Angel et al., to 5. A second major contribution of the paper is that it gets rid of the expensive multi operation that was a mainstay of all previous local search algorithms for capacitated facility location and universal facility location problem. The only operations that we require to prove the 5-approximation are add, open, and close. A multi operation is basically a combination of the open and close operations. The 5-approximation algorithm for the capacitated facility location problem, given by Bansal et al., also uses the multi operation. However, on careful observation, it turned out that add, open, and close operations are sufficient to prove a 5-factor for the problem. This resulted into an improved algorithm for the universal facility location problem, with an improved factor

    Health Financing In Ghana: Perceived Factors That Help Healthcare Facility Providers to Render Services to Clients of National Health Insurance Scheme

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    Health financing has become a universal concern especially for developing countries. Ghana has introduced National Health Insurance Scheme (NHIS) programme for its residents. This paper explores the perceived factors that help the accredited Healthcare Facility Providers (HFPs) to render services to the clients who have registered with the NHIS. The design used a survey which relied on questionnaire that provided six factors for respondents to rank according to how important they perceive the factor to help them in serving the clients of NHIS. These factors were selected based on the researcher’s own interactions with the HFPs. Claims payment was ranked as the most important factor, followed by staff at post, patients support facilities, services rendered, culture at the facility and facility location. These factors were discussed and recommendations were made to help HFPs serve the clients of NHIS. Keywords: National Health Insurance Scheme (NHIS), Healthcare Facility Providers (HFPs),   Community-based Health Planning Service (CHPS

    Set covering with our eyes closed

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    Given a universe UU of nn elements and a weighted collection S\mathscr{S} of mm subsets of UU, the universal set cover problem is to a priori map each element u∈Uu \in U to a set S(u)∈SS(u) \in \mathscr{S} containing uu such that any set X⊆UX{\subseteq U} is covered by S(X)=\cup_{u\in XS(u). The aim is to find a mapping such that the cost of S(X)S(X) is as close as possible to the optimal set cover cost for XX. (Such problems are also called oblivious or a priori optimization problems.) Unfortunately, for every universal mapping, the cost of S(X)S(X) can be Ω(n)\Omega(\sqrt{n}) times larger than optimal if the set XX is adversarially chosen. In this paper we study the performance on average, when XX is a set of randomly chosen elements from the universe: we show how to efficiently find a universal map whose expected cost is O(log⁥mn)O(\log mn) times the expected optimal cost. In fact, we give a slightly improved analysis and show that this is the best possible. We generalize these ideas to weighted set cover and show similar guarantees to (nonmetric) facility location, where we have to balance the facility opening cost with the cost of connecting clients to the facilities. We show applications of our results to universal multicut and disc-covering problems and show how all these universal mappings give us algorithms for the stochastic online variants of the problems with the same competitive factors

    Waste Reduction, Construction and Demolition Debris: Guide for Building, Construction and Environmental Professionals, Revised November 2008

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    This document is intended to lay the foundation for resource reduction strategies in new construction, renovation and demolition. If you have an innovative idea or information that you believe should be included in future updates of this manual please email Shelly Codner at [email protected] or Jan Loyson at [email protected]. Throughout this manual, we use the term “waste reduction” to define waste management initiatives that will result in less waste going to the landfill. In accordance with the waste management hierarchy these practices include reducing (waste prevention), reusing (deconstruction and salvage), recycling and renewing (making old things new again) - in that order. This manual will explain what these practices are and how to incorporate them into your projects

    UNIVERSAL DESIGN APPLICATION THROUGH SOUTH KOREA REDEVELOPMENT (A Study Review)

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    The evolution toward Universal Design was began in the 1950s with a new attention to design for people with disabilities. At the same era South Korea began their development after several wars. Recently some of researchs and projects in South Korea which conducted on Universal Design concept are increasing in quantity and widening in multidiciplinary areas to make a better living for people in South Korea. This study examined those researches and projects to determine the progress of Universal Design principles application in South Korea in several periods and evaluated the result by the project’s purpose. This study is a review from several literatures related to universal design application in South Korea. The Review revealed that South Korea has published regulations, guidelines and law based on universal design principles. South Korea has established universal design principles as fundamental basis in designing and developing their public space, public facilities building and elderly residential houses. Application of universal design influenced the knowledge of diversity for people especialy in disability and elderly. Universal design encourage people with diversity in ability, ages, gender to live together without barrier to access and use every facilities in their regions. Keywords : Universal Design, Development, South Korea, Review, Diversit

    Maximum gradient embeddings and monotone clustering

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    Let (X,d_X) be an n-point metric space. We show that there exists a distribution D over non-contractive embeddings into trees f:X-->T such that for every x in X, the expectation with respect to D of the maximum over y in X of the ratio d_T(f(x),f(y)) / d_X(x,y) is at most C (log n)^2, where C is a universal constant. Conversely we show that the above quadratic dependence on log n cannot be improved in general. Such embeddings, which we call maximum gradient embeddings, yield a framework for the design of approximation algorithms for a wide range of clustering problems with monotone costs, including fault-tolerant versions of k-median and facility location.Comment: 25 pages, 2 figures. Final version, minor revision of the previous one. To appear in "Combinatorica

    Solving the p-median location problem with the Erlenkotter approach in public service system design

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    The problem can be often formulated as a weighted p-median problem. Real instances of the problem are characterized by big numbers of possible service center locations, which can take the value of several hundreds or thousands. The optimal solution can be obtained by the universal IP solvers only for smaller instances of the problem. The universal IP solvers are very time-consuming and often fail when solving a large instance. Our approach to the problem is based on the Erlenkotter procedure for solving of the uncapacitated facility location problem and on the Lagrangean relaxation of the constraint which limits number of the located center. The suggested approach finds the optimal solution in most of the studied instances. The quality and the feasibility of the resulting solutions of the suggested approach depend on the setting of the Lagrangean multiplier. A suitable value of the multiplier can be obtained by a bisection algorithm. The resulting multiplier cannot guarantee an optimal solution, but provides a near-to-optimal solution and a lower bound. If our approach does not obtain the optimal solution, then a heuristic improves the near-to-optimal solution. The resulting solution of our approach and the optimal solution obtained by the universal IP solver XPRESS-IVE are compared in the computational time and the quality of solutions

    Traffic-Redundancy Aware Network Design

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    We consider network design problems for information networks where routers can replicate data but cannot alter it. This functionality allows the network to eliminate data-redundancy in traffic, thereby saving on routing costs. We consider two problems within this framework and design approximation algorithms. The first problem we study is the traffic-redundancy aware network design (RAND) problem. We are given a weighted graph over a single server and many clients. The server owns a number of different data packets and each client desires a subset of the packets; the client demand sets form a laminar set system. Our goal is to connect every client to the source via a single path, such that the collective cost of the resulting network is minimized. Here the transportation cost over an edge is its weight times times the number of distinct packets that it carries. The second problem is a facility location problem that we call RAFL. Here the goal is to find an assignment from clients to facilities such that the total cost of routing packets from the facilities to clients (along unshared paths), plus the total cost of "producing" one copy of each desired packet at each facility is minimized. We present a constant factor approximation for the RAFL and an O(log P) approximation for RAND, where P is the total number of distinct packets. We remark that P is always at most the number of different demand sets desired or the number of clients, and is generally much smaller.Comment: 17 pages. To be published in the proceedings of the Twenty-Third Annual ACM-SIAM Symposium on Discrete Algorithm

    Generating Representative ISP Technologies From First-Principles

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    Understanding and modeling the factors that underlie the growth and evolution of network topologies are basic questions that impact capacity planning, forecasting, and protocol research. Early topology generation work focused on generating network-wide connectivity maps, either at the AS-level or the router-level, typically with an eye towards reproducing abstract properties of observed topologies. But recently, advocates of an alternative "first-principles" approach question the feasibility of realizing representative topologies with simple generative models that do not explicitly incorporate real-world constraints, such as the relative costs of router configurations, into the model. Our work synthesizes these two lines by designing a topology generation mechanism that incorporates first-principles constraints. Our goal is more modest than that of constructing an Internet-wide topology: we aim to generate representative topologies for single ISPs. However, our methods also go well beyond previous work, as we annotate these topologies with representative capacity and latency information. Taking only demand for network services over a given region as input, we propose a natural cost model for building and interconnecting PoPs and formulate the resulting optimization problem faced by an ISP. We devise hill-climbing heuristics for this problem and demonstrate that the solutions we obtain are quantitatively similar to those in measured router-level ISP topologies, with respect to both topological properties and fault-tolerance

    Place, time and experience: barriers to universalization of institutional child delivery in rural Mozambique

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    CONTEXT: Although institutional coverage of childbirth is increasing in the developing world, a substantial minority of births in rural Mozambique still occur outside of health facilities. Identifying the remaining barriers to safe professional delivery services can aid in achieving universal coverage. METHODS: Survey data collected in 2009 from 1,373 women in Gaza, Mozambique, were used in combination with spatial, meteorological and health facility data to examine patterns in place of delivery. Geographic information system–based visualization and mapping and exploratory spatial data analysis were used to outline the spatial distribution of home deliveries. Multilevel logistic regression models were constructed to identify associations between individual, spatial and other characteristics and whether women's most recent delivery took place at home. RESULTS: Spatial analysis revealed high- and low-prevalence clusters of home births. In multivariate analyses, women with a higher number of clinics within 10 kilometers of their home had a reduced likelihood of home delivery, but those living closer to urban centers had an increased likelihood. Giving birth during the rainy, high agricultural season was positively associated with home delivery, while household wealth was negatively associated with home birth. No associations were evident for measures of exposure to and experience with health institutions. CONCLUSIONS: The results suggest the need for a comprehensive approach to expansion of professional delivery services. Such an approach should complement measures facilitating physical access to health institutions for residents of harder-to-reach areas with community-based interventions aimed at improving rural women's living conditions and opportunities, while also taking into account seasonal and other variables
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