Computing the Face Lattice of a Polytope from its Vertex-Facet Incidences

We give an algorithm that constructs the Hasse diagram of the face lattice of a convex polytope P from its vertex-facet incidences in time O(min{n,m}*a*f), where n is the number of vertices, m is the number of facets, a is the number of vertex-facet incidences, and f is the total number of faces of P. This improves results of Fukuda and Rosta (1994), who described an algorithm for enumerating all faces of a d-polytope in O(min{n,m}*d*f^2) steps. For simple or simplicial d-polytopes our algorithm can be specialized to run in time O(d*a*f). Furthermore, applications of the algorithm to other atomic lattices are discussed, e.g., to face lattices of oriented matroids.Comment: 14 pages; to appear in: Comput. Geom.; the new version contains some minor extensions and corrections as well as a more detailed treatment of oriented matroid

Safety in maritime oil sector: Content analysis of machinery space fire hazards

An in-depth study of the practice within the maritime oil industry was undertaken to ascertain safety issues in seafaring vessels. It was more concentrated on the type of accidents that occur in machine spaces of seafaring vessels in this industry. The main focus of the research was streamlined to fire in machinery spaces. The literature review later concentrated on two of such incidences, they are oil spill and fire events. An investigation was done to assess those factors which actually contribute or are in association to fire outbreak. A content analysis methodology was used to investigate the associative relationships to fire outbreak with the aid of NVivo 9.0 software. The investigation focused on 15 key in-depth reports on machinery space incidences which were uploaded into the software. The results indicate that leakages on hot surfaces were the major causes of fire hazards in seafaring vessels. The results from using this methodology also highlighted two more fire hazards that were not so apparent in previous studies. They are generator fire and compressors fire. The results supported other studies about leakages on hot surfaces as a major contributor, but also clearly show that there are other hazardous factors of fire in machinery spaces that require further investigation

A comprehensive analysis of it/is indirect costs: Enhancing the evaluation of information systems investments

The level of Information Technology (IT) expenditure within organizations continues to increase over the years in an attempt to gain a competitive advantage in their respective industries. Nonetheless, IT projects still experience budget overruns taking into account the continual fall of hardware costs. This phenomenon presents a dilemma to managers who struggle to evaluate their investments in IT. Adding to the difficulty is the peculiar nature of such investments having Human and Organizational dimensions. Such dimensions are later translated into indirect costs that are both difficult to identify and quantify hence are ignored by managers which hinders the evaluation process. The lack of knowledge of managers about IT/IS indirect costs affect their ability to determine the true costs of deploying IT. It is closing the gap that this paper strives to explore a new method for identifying, managing and controlling IT indirect costs through a case study enquiry of a leading gold producing company. The research establishes a rational that goes beyond the traditional quantification appraisal of costs which is inadequate in the case of indirect costs. It proposes a solution that helps to thoroughly identify the indirect costs, mitigate their effect and achieve the desired control while enhancing the evaluation process through their inclusion

On topological and geometric (194)(19_4) configurations

An $(n_k)$ configuration is a set of $n$ points and $n$ lines such that each point lies on $k$ lines while each line contains $k$ points. The configuration is geometric, topological, or combinatorial depending on whether lines are considered to be straight lines, pseudolines, or just combinatorial lines. The existence and enumeration of $(n_k)$ configurations for a given $k$ has been subject to active research. A current front of research concerns geometric $(n_4)$ configurations: it is now known that geometric $(n_4)$ configurations exist for all $n \ge 18$, apart from sporadic exceptional cases. In this paper, we settle by computational techniques the first open case of $(19_4)$ configurations: we obtain all topological $(19_4)$ configurations among which none are geometrically realizable.Comment: 13 pages, 7 figure

In Search of Poverty Predictors: The Case of Urban and Rural Pakistan

The main objective of this research is to provide correlates of household consumption or poverty using the latest household survey. The estimated coefficients and their weights may be used to predict poverty incidence from light monitoring survey such as Core Welfare Indicator Questionnaire (CWIQ). The CWIQ survey instrument essentially collects simple welfare indicators from a large segment of population and is not designed to measure income, consumption or expenditure. The paper estimates consumption functions separately for urban and rural areas. These functions are estimatedwith the help of non-monetary correlates of consumption and applied to predict poverty at provincial and district levels. The paper also provides the latest estimates of poverty in the country using a consistent methodology. Overall, 33 percent people were poor, according to estimates from the latest available household survey of 2001-02. Incidence, depth, and severity of poverty are high in rural areas, as compared to their urban counterpart.

Assignment Methods for Incidence Calculus

AbstractIncidence calculus is a mechanism for probabilistic reasoning in which sets of possible worlds, called incidences, are associated with axioms, and probabilities are then associated with these sets. Inference rules are used to deduce bounds on the incidence of formulae which are not axioms, and bounds for the probability of such a formula can then be obtained. In practice an assignment of probabilities directly to axioms may be given, and it is then necessary to find an assignment of incidence which will reproduce these probabilities. We show that this task of assigning incidences can be viewed as a tree searching problem, and two techniques for performing this research are discussed. One of these is a new proposal involving a depth first search, while the other incorporates a random element. A Prolog implementation of these methods has been developed. The two approaches are compared for efficiency and the significance of their results are discussed. Finally we discuss a new proposal for applying techniques from linear programming to incidence calculus