30,523 research outputs found

    Confidential Report on the Recent Bombing of Le Havre

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    Flight Lieutenant R.F. Delderfield was a RAF public relations officer in 1944 when he was ordered to the continent to cover the capture of Le Havre. Arriving about a week after the city was liberated, Delderfield spent two days examining the town and interviewing soldiers and civlians about their impressions of the RAF bombing of the city. The report is noteworthy for the attention it pays to the impact of the bombing of the local population. The RAF subsequently modified its plans for the bombing of Boulogne so that only defensive works around the perimeter of the city were attacked and a Royal Air Force officer was in direct communication with the aircraft during the attacks the ensure that accuracy was maintained

    Relational visual cluster validity

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    The assessment of cluster validity plays a very important role in cluster analysis. Most commonly used cluster validity methods are based on statistical hypothesis testing or finding the best clustering scheme by computing a number of different cluster validity indices. A number of visual methods of cluster validity have been produced to display directly the validity of clusters by mapping data into two- or three-dimensional space. However, these methods may lose too much information to correctly estimate the results of clustering algorithms. Although the visual cluster validity (VCV) method of Hathaway and Bezdek can successfully solve this problem, it can only be applied for object data, i.e. feature measurements. There are very few validity methods that can be used to analyze the validity of data where only a similarity or dissimilarity relation exists – relational data. To tackle this problem, this paper presents a relational visual cluster validity (RVCV) method to assess the validity of clustering relational data. This is done by combining the results of the non-Euclidean relational fuzzy c-means (NERFCM) algorithm with a modification of the VCV method to produce a visual representation of cluster validity. RVCV can cluster complete and incomplete relational data and adds to the visual cluster validity theory. Numeric examples using synthetic and real data are presente

    A sparse multinomial probit model for classification

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    A recent development in penalized probit modelling using a hierarchical Bayesian approach has led to a sparse binomial (two-class) probit classifier that can be trained via an EM algorithm. A key advantage of the formulation is that no tuning of hyperparameters relating to the penalty is needed thus simplifying the model selection process. The resulting model demonstrates excellent classification performance and a high degree of sparsity when used as a kernel machine. It is, however, restricted to the binary classification problem and can only be used in the multinomial situation via a one-against-all or one-against-many strategy. To overcome this, we apply the idea to the multinomial probit model. This leads to a direct multi-classification approach and is shown to give a sparse solution with accuracy and sparsity comparable with the current state-of-the-art. Comparative numerical benchmark examples are used to demonstrate the method

    Configurations of Control: A Transaction Cost Approach

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    In this paper, I present a theory of management control based on Transaction Cost Economics.This theory seeks to integrate into a single framework a set of insights as to the natureof the organization's activities, the control problems that are inherent in these activities,and the unique problem solving potential of various archetypal control structures. The gistof the argument is that activities predictably differ in the control problems to which theygive rise, whereas control archetypes differ in their problem-solving ability, and thatalignments between the two can be explained by delineating the efficiency properties of thematch. This is a contingent configuration approach. It is a configuration theory in that itoffers a set of ideal types, conceived of as internally consistent and discriminating clustersof attributes from multiple dimensions that have a specific effect on control structureeffectiveness as the variable to be explained. But it is also a contingent approach in that itspecifies the conditions in which each of the archetypes is most effective.transaction cost economics;management control theory;configuration theory

    Solving Lotsizing Problems on Parallel Identical Machines Using Symmetry Breaking Constraints

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    Production planning on multiple parallel machines is an interesting problem, both from a theoretical and practical point of view. The parallel machine lotsizing problem consists of finding the optimal timing and level of production and the best allocation of products to machines. In this paper we look at how to incorporate parallel machines in a Mixed Integer Programming model when using commercial optimization software. More specifically, we look at the issue of symmetry. When multiple identical machines are available, many alternative optimal solutions can be created by renumbering the machines. These alternative solutions lead to difficulties in the branch-and-bound algorithm. We propose new constraints to break this symmetry. We tested our approach on the parallel machine lotsizing problem with setup costs and times, using a network reformulation for this problem. Computational tests indicate that several of the proposed symmetry breaking constraints substantially improve the solution time, except when used for solving the very easy problems. The results highlight the importance of creative modeling in solving Mixed Integer Programming problems.Mixed Integer Programming;Formulations;Symmetry;Lotsizing

    Shore platforms and mass-movement: A reply

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    Implicit in Mr Wright's note on shore platforms and mass-movement is a criticism of our findings on the role of mass-movement in shore platform development along the Gisborne coastline, New Zealand (McLean and Davidson, 1968). The lack of explicit criticism makes any reply difficult; we are not rebuked on our own evidence, nor is any fresh evidence presented from the same area to make it necessary for us to change or modify our original views

    The role of mass-movement in shore platform development along the Gisborne coastline, New Zealand

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    Tidal shore platforms form a conspicuous part of the coastal scenery north of Gisborne, New Zealand. Some of these platforms are being extended landward under present-day conditions. Present widening results primarily from cliff-retreat by mass-movement. The coincidence in distribution of areas of wave convergence, mass-movement and shore platforms suggests a genetic connection between these marine and subaerial process and response elements. Various types of mass-movement are involved in cliff-retreat, notably slumps, flows, debris slides and soil and rock falls. While the products of such mass-movement forms are removed by wave action, extensive boulder fields on some shore platforms indicate that removal is not always complete. Not all of the shore platforms on this coast are being widened at present. Widening has ceased where active mass-movement is not occurring

    Iterative criteria-based approach to engineering the requirements of software development methodologies

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    Software engineering endeavours are typically based on and governed by the requirements of the target software; requirements identification is therefore an integral part of software development methodologies. Similarly, engineering a software development methodology (SDM) involves the identification of the requirements of the target methodology. Methodology engineering approaches pay special attention to this issue; however, they make little use of existing methodologies as sources of insight into methodology requirements. The authors propose an iterative method for eliciting and specifying the requirements of a SDM using existing methodologies as supplementary resources. The method is performed as the analysis phase of a methodology engineering process aimed at the ultimate design and implementation of a target methodology. An initial set of requirements is first identified through analysing the characteristics of the development situation at hand and/or via delineating the general features desirable in the target methodology. These initial requirements are used as evaluation criteria; refined through iterative application to a select set of relevant methodologies. The finalised criteria highlight the qualities that the target methodology is expected to possess, and are therefore used as a basis for de. ning the final set of requirements. In an example, the authors demonstrate how the proposed elicitation process can be used for identifying the requirements of a general object-oriented SDM. Owing to its basis in knowledge gained from existing methodologies and practices, the proposed method can help methodology engineers produce a set of requirements that is not only more complete in span, but also more concrete and rigorous
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