3,808 research outputs found

    Partitioning Relational Matrices of Similarities or Dissimilarities using the Value of Information

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    In this paper, we provide an approach to clustering relational matrices whose entries correspond to either similarities or dissimilarities between objects. Our approach is based on the value of information, a parameterized, information-theoretic criterion that measures the change in costs associated with changes in information. Optimizing the value of information yields a deterministic annealing style of clustering with many benefits. For instance, investigators avoid needing to a priori specify the number of clusters, as the partitions naturally undergo phase changes, during the annealing process, whereby the number of clusters changes in a data-driven fashion. The global-best partition can also often be identified.Comment: Submitted to the IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP

    An Analysis of the Value of Information when Exploring Stochastic, Discrete Multi-Armed Bandits

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    In this paper, we propose an information-theoretic exploration strategy for stochastic, discrete multi-armed bandits that achieves optimal regret. Our strategy is based on the value of information criterion. This criterion measures the trade-off between policy information and obtainable rewards. High amounts of policy information are associated with exploration-dominant searches of the space and yield high rewards. Low amounts of policy information favor the exploitation of existing knowledge. Information, in this criterion, is quantified by a parameter that can be varied during search. We demonstrate that a simulated-annealing-like update of this parameter, with a sufficiently fast cooling schedule, leads to an optimal regret that is logarithmic with respect to the number of episodes.Comment: Entrop

    Reduction of Markov Chains using a Value-of-Information-Based Approach

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    In this paper, we propose an approach to obtain reduced-order models of Markov chains. Our approach is composed of two information-theoretic processes. The first is a means of comparing pairs of stationary chains on different state spaces, which is done via the negative Kullback-Leibler divergence defined on a model joint space. Model reduction is achieved by solving a value-of-information criterion with respect to this divergence. Optimizing the criterion leads to a probabilistic partitioning of the states in the high-order Markov chain. A single free parameter that emerges through the optimization process dictates both the partition uncertainty and the number of state groups. We provide a data-driven means of choosing the `optimal' value of this free parameter, which sidesteps needing to a priori know the number of state groups in an arbitrary chain.Comment: Submitted to Entrop

    The availability of local aerial photography in southern California

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    Some of the major photography and photogrammetric suppliers and users located in Southern California are listed. Recent trends in aerial photographic coverage of the Los Angeles basin area are also noted, as well as the uses of that imagery

    Análisis del efecto que tiene la selección del modelo de construcción de portafolio óptimo y de valoración en riesgo de mercado en la administración de la riqueza

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    Como consecuencia del desarrollo económico vivido en las últimas décadas, se ha producido un fenómeno superavitario de riqueza en la sociedad, el cual requiere de una adecuada planeación financiera y un eficiente manejo de los excedentes económicos; esto ha hecho que la teoría de la administración de la riqueza (Wealth Management) juegue un papel protagónico al momento de la toma de decisiones de inversión -- Desconocer esta teoría puede llevar a un inversionista a tomar decisiones sin fundamentos, las cuales no conllevan al punto óptimo donde se maximicen las utilidades con el menor riesgo posible -- Entendiendo esto, expondremos cómo la selección entre dos métodos de construcción del portafolio óptimo y el cálculo del valor en riesgo, al parecer una decisión poco trascendental o poco conocida para un inversionista, puede afectar directamente la rentabilidad de un fondo a causa de la respectiva recomposición del portafolio que ocasiona cada métodoAs a consequence of the economic development experienced in the last decades, there has been a surplus wealth phenomenon in society, which requires adequate financial planning and efficient management of economic surpluses -- This has led to the theory of the administration of Wealth Management plays a leading role when making investment decisions -- Not knowing this theory can lead an investor to make decisions without fundamentals, which do not lead to the optimum where profit maximizes with the lowest possible risk -- Understanding this, we will explain how the selection between two methods of constructing the optimum portfolio and the calculation of the value at risk, apparently a decision little transcendental or little known for an investor, can directly affect the profitability of a fund because of the respective recomposition of the portfolio that causes each metho

    The acetabular blood supply: implications for periacetabular osteotomies

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    As the popularity of juxta-acetabular osteotomies in adults increases, concern arises that such a procedure will potentially cause avascular necrosis of the acetabular fragment. In order to verify the remaining vascularization after a Bernese periacetabular osteotomy, an injection study with colored latex was performed. The vascularity of the outside of the periacetabular bone was studied in 16 hips after injection of colored latex into the abdominal aorta and the inside in four hips. To confirm the conclusions drawn from the anatomic study, a Bernese periacetabular osteotomy was performed in two additional hips after latex injection. This study demonstrated that through a modified Smith-Peterson approach and with execution of the osteotomies from the inside of the pelvis the acetabular fragment remains vascularized by the supra-acetabular and acetabular branches of the superior gluteal artery, the obturator artery and the inferior gluteal artery. Some uncertainty remains about how much correction is tolerated by the smaller blood vessel

    Software Tools for Indigenous Knowledge Management

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    Indigenous communities are beginning to realize the potential benefits which digital technologies can offer with regard to the documentation and preservation of their histories and cultures. However they are also coming to understand the opportunities for misuse and misappropriation of their knowledge which may accompany digitization. In this paper we describe a set of open source software tools which have been designed to enable indigenous communities to protect unique cultural knowledge and materials which have been preserved through digitization. The software tools described here enable authorized members of communities to: define and control the rights, accessibility and reuse of their digital resources; uphold traditional laws pertaining to secret/sacred knowledge or objects; prevent the misuse of indigenous heritage in culturally inappropriate or insensitive ways; ensure proper attribution to the traditional owners; and enable indigenous communities to describe their resources in their own words. Hopefully the deployment of such tools will contribute to the self-determination and empowerment of indigenous communities through the revitalization of their cultures and knowledge which have been eroded by colonization, western laws, western cultures and globalization

    Traumatic labral avulsion from the stable rim: a constant pathology in displaced transverse acetabular fractures

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    Introduction: During the treatment of a malunited transverse acetabular fracture, a hitherto undescribed extended avulsion of the labrum from the stable acetabular fragment was found. Based on the labral pathomorphology present in this case, the hypothesis was put forward that traumatic acetabular labral avulsions are a constant phenomenon in transverse acetabular fractures. Patients and methods: Fourteen patients underwent capsulotomy and/or surgical dislocation of the involved hip to facilitate open reduction and internal fixation of transverse acetabular fractures. Results: In all cases, the labrum was partially or completely detached from the superior acetabular rim. In eight cases with bucket-handle tears of the labrum from the stable superior fragment, the injured portion was resected back to normal margins. In one case the labrum was avulsed with an attached piece of bone and was repaired by screw fixation. Small separations of the labrum from the underlying acetabular rim occurred at the level of the fractures in five cases with minor displacement and received no treatment. Conclusion: With displaced transverse acetabular fractures, consideration should be given to opening the joint at the time of open reduction and internal fixation to look for associated intracapsular injuries. An avulsed portion of the labrum should be left if stable and undamaged. If unstable and damaged, it is probably better resected and if unstable but intact and/or attached to a bony fragment, it should be repaire
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