76 resultados para Characteristic Initial Value Problem


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By a sequence of rollings without slipping or twisting along segments of a straight line of the plane, a spherical ball of unit radius has to be transferred from an initial state to an arbitrary final state taking into account the orientation of the ball. We provide a new proof that with at most 3 moves, we can go from a given initial state to an arbitrary final state. The first proof of this result is due to Hammersley ( 1983). His proof is more algebraic than ours which is more geometric. We also showed that generically no one of the three moves, in any elimination of the spin discrepancy, may have length equal to an integral multiple of 2 pi.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Objectives: The purpose of this study was to determine if intra-abdominal pressure (IAP) could predict acute renal injury (AKI) in the postoperative period of abdominal surgeries, and which would be its cutoff value. Patients and methods: A prospective observational study was conducted in the period from January 2010 to March 2011 in the Intensive Care Units (ICUs) of the University Hospital of Botucatu Medical School, UNESP. Consecutive patients undergoing abdominal surgery were included in the study. Initial evaluation, at admission in ICU, was performed in order to obtain demographic, clinical surgical and therapeutic data. Evaluation of IAP was obtained by the intravesical method, four times per day, and renal function was evaluated during the patient's stay in the ICU until discharge, death or occurrence of AKI. Results: A total of 60 patients were evaluated, 16 patients developed intra-abdominal hypertension (IAH), 45 developed an abnormal IAP (>7 mmHg) and 26 developed AKI. The first IAP at the time of admission to the ICU was able to predict the occurrence of AKI (area under the receiver-operating characteristic curve was 0.669; p=0.029) with the best cutoff point (by Youden index method) >= 7.68 mmHg, sensitivity of 87%, specificity of 46% at this point. The serial assessment of this parameter did not added prognostic value to initial evaluation. Conclusion: IAH was frequent in patients undergoing abdominal surgeries during ICU stay, and it predicted the occurrence of AKI. Serial assessments of IAP did not provided better discriminatory power than initial evaluation.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Purpose - The purpose of this paper is twofold: to analyze the computational complexity of the cogeneration design problem; to present an expert system to solve the proposed problem, comparing such an approach with the traditional searching methods available.Design/methodology/approach - The complexity of the cogeneration problem is analyzed through the transformation of the well-known knapsack problem. Both problems are formulated as decision problems and it is proven that the cogeneration problem is np-complete. Thus, several searching approaches, such as population heuristics and dynamic programming, could be used to solve the problem. Alternatively, a knowledge-based approach is proposed by presenting an expert system and its knowledge representation scheme.Findings - The expert system is executed considering two case-studies. First, a cogeneration plant should meet power, steam, chilled water and hot water demands. The expert system presented two different solutions based on high complexity thermodynamic cycles. In the second case-study the plant should meet just power and steam demands. The system presents three different solutions, and one of them was never considered before by our consultant expert.Originality/value - The expert system approach is not a "blind" method, i.e. it generates solutions based on actual engineering knowledge instead of the searching strategies from traditional methods. It means that the system is able to explain its choices, making available the design rationale for each solution. This is the main advantage of the expert system approach over the traditional search methods. On the other hand, the expert system quite likely does not provide an actual optimal solution. All it can provide is one or more acceptable solutions.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Some experiments in Physics teaching have an amazing effect among the students, that is, generally be characterized by counteracting the initial expectations of students. This characteristic may contribute to the emergence of learning situations extremely promising. However, the privilege, by the teacher, the description of certain results shortens the involvement that the student could establish on teaching situations favor a more careful observation that can be done. We discuss in this paper, the that surprise may be manifested in the student on an experimental demonstration and its ability to mobilize the interest and curiosity of this student. We intend to observe the pedagogic value that represents the amazing effect such in situations of teaching and learning, particularly for the Teaching of Physics, as well as the possibilities for educational approaches.Through an extensive analysis of several authors who address about experimental learning activities, Epistemology of Science and Education, we found some results that lead us to understand some of the possibilities that the surprise element can propose. We describe a demonstration activity that we consider amazingly from our point of view and that was realized in a regular classroom in a of Rio Claro Public High School in the year of 2011

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The increasing number of space debris in operating regions around the earth constitutes a real threat to space missions. The goal of the research is to establish appropriate scientific-technological conditions to prevent the destruction and/or impracticability of spacecraft in imminent collision in these regions. A definitive solution to this problem has not yet been reached with the degree of precision that the dynamics of spatial objects (vehicle and debris) requires mainly due to the fact that collisions occur in chains and fragmentation of these objects in the space environment. This fact threatens the space missions on time and with no prospects for a solution in the near future. We present an optimization process in finding the initial conditions (CIC) to collisions, considering the symmetry of the distributions of maximum relative positions between spatial objects with respect to the spherical angles. For this, we used the equations of the dynamics on the Clohessy-Witshire, representing a limit of validation that is highly computationally costly. We simulate different maximum relative positions values of the corresponding initial conditions given in terms of spherical angles. Our results showed that there are symmetries that significantly reduce operating costs, such that the search of the CIC is advantageously carried out up to 4 times the initial processing routine. Knowledge of CIC allows the propulsion system operating vehicle implement evasive maneuvers before impending collisions with space debris.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)