841 resultados para Coordination scheme


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One pair of reactants, Cu(hfac)(2) = M and the hinge-flexible radical ligand 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine (3PPN = L), yields a diverse set of five coordination complexes: a cyclic loop M(2)L(1) dimer; a 1:1 cocrystal between an M(2)L(2) loop and an ML(2) fragment; a ID chain of M(2)L(2) loops linked by M; two 2D M(3)L(2) networks of (M-L)(n) chains crosslinked by M with different repeat length pitches; a 3D M(3)L(2) network of M(2)L(2) loops cross-linking (M-L)(n)-type chains with connectivity different from those in the 2D networks. Most of the higher dimensional complexes exhibit reversible, temperature-dependent spin-state conversion of high-temperature paramagnetic states to lower magnetic moment states having antiferromagnetic exchange within Cu-ON bonds upon cooling, with accompanying bond contraction. The 3D complex also exhibited antiferromagnetic exchange between Cu(II) ions linked in chains through pyrimidine rings.

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In this article, we present an analytical direct method, based on a Numerov three-point scheme, which is sixth order accurate and has a linear execution time on the grid dimension, to solve the discrete one-dimensional Poisson equation with Dirichlet boundary conditions. Our results should improve numerical codes used mainly in self-consistent calculations in solid state physics.

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In a previous paper, we developed a phenomenological-operator technique aiming to simplify the estimate of losses due to dissipation in cavity quantum electrodynamics. In this paper, we apply that technique to estimate losses during an entanglement concentration process in the context of dissipative cavities. In addition, some results, previously used without proof to justify our phenomenological-operator approach, are now formally derived, including an equivalent way to formulate the Wigner-Weisskopf approximation.

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Cyclization of (n)butyl glyoxylate thiosemicarbazone (HBuTSC) under reflux in the presence of Pb(OAc)(2) led to tile formation of the complex [Pb(HTz)(2)] (H(2)Tz = 3,4-dihydro-3-thioxo-1,2,4-triazin-5(2H)-one), which after recrystallization from DMSO afforded the polymer [Pb(Tz)](n), the first example of a Tz(2-) metal complex. (C) 2008 Elsevier B.V. All rights reserved.

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Complexes [RuCl(H4NO(2)Fo4M)(bipy)(dppb)]PF(6) (1), [RuCl(H4NO(2)Fo4M)(Mebipy)(dppb)]PF(6) (2), [RuCl(H4NO(2)Fo4M)(phen)(dppb)]PF(6) (3), [RuCl(H4NO(2)Ac4M)(bipy)(dppb)]PF(6) (4), [RuCl(H4NO(2)Ac4M)(Mebipy)(dppb)]PF(6) (5) and [RuCl(H4NO(2)Ac4M)(phen)(dppb)]PF(6) (6) with N(4)-methyl-4-nitrobenzalde hyde thiosemicarbazone (H4NO(2)Fo4M) and N(4)-methyl-4-nitroacetophenone thiosemicarbazone (H4NO(2) Ac4M) were obtained from [RuCl(2)(bipy)(dppb)], [RuCl(2)(Mebipy)(dppb)], and [RuCl(2)(phen)(dppb)], (dppb = 1,4-bis(diphenylphospine)butane; bipy = 2,2`-bipyridine: Mebipy = 4,4`-dimethyl-2,2`-bipyridine: phen = 1,10-phenanthroline). In all cases the thiosemicarbazone is attached to the metal center through the sulfur atom. Complexes (1-6), together with the corresponding ligands and the Ru precursors were evaluated for their ability to in vitro suppress the growth of Trypanosoma cruzi. All complexes were more active than their corresponding ligands and precursors. Complexes (1-3) and (5) revealed to be the most active among all studied compounds with ID(50) = 0.6-0.8 mu M. In all cases the association of the thiosemicarbazone with ruthenium, dppb and bipyridine or phenanthroline in one same complex proved to be an excellent strategy for activity improvement. (C) 2010 Elsevier Masson SAS. All rights reserved.

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Architectures based on Coordinated Atomic action (CA action) concepts have been used to build concurrent fault-tolerant systems. This conceptual model combines concurrent exception handling with action nesting to provide a general mechanism for both enclosing interactions among system components and coordinating forward error recovery measures. This article presents an architectural model to guide the formal specification of concurrent fault-tolerant systems. This architecture provides built-in Communicating Sequential Processes (CSPs) and predefined channels to coordinate exception handling of the user-defined components. Hence some safety properties concerning action scoping and concurrent exception handling can be proved by using the FDR (Failure Divergence Refinement) verification tool. As a result, a formal and general architecture supporting software fault tolerance is ready to be used and proved as users define components with normal and exceptional behaviors. (C) 2010 Elsevier B.V. All rights reserved.

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A forum is a valuable tool to foster reflection in an in-depth discussion; however, it forces the course mediator to continually pay close attention in order to coordinate learners` activities. Moreover, monitoring a forum is time consuming given that it is impossible to know in advance when new messages are going to be posted. Additionally, a forum may be inactive for a long period and suddenly receive a burst of messages forcing forum mediators to frequently log on in order to know how the discussion is unfolding to intervene whenever it is necessary. Mediators also need to deal with a large amount of messages to identify off-pattern situations. This work presents a piece of action research that investigates how to improve coordination support in a forum using mobile devices for mitigating mediator`s difficulties in following the status of a forum. Based on summarized information extracted from message meta-data, mediators consult visual information summaries on PDAs and receive textual notifications in their mobile phone. This investigation revealed that mediators used the mobile-based coordination support to keep informed on what is taking place within the forum without the need to log on their desktop computer. (C) 2009 Elsevier Ltd. All rights reserved.

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The goal of this paper is to present an approximation scheme for a reaction-diffusion equation with finite delay, which has been used as a model to study the evolution of a population with density distribution u, in such a way that the resulting finite dimensional ordinary differential system contains the same asymptotic dynamics as the reaction-diffusion equation.

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The traveling salesman problem is although looking very simple problem but it is an important combinatorial problem. In this thesis I have tried to find the shortest distance tour in which each city is visited exactly one time and return to the starting city. I have tried to solve traveling salesman problem using multilevel graph partitioning approach.Although traveling salesman problem itself very difficult as this problem is belong to the NP-Complete problems but I have tried my best to solve this problem using multilevel graph partitioning it also belong to the NP-Complete problems. I have solved this thesis by using the k-mean partitioning algorithm which divides the problem into multiple partitions and solving each partition separately and its solution is used to improve the overall tour by applying Lin Kernighan algorithm on it. Through all this I got optimal solution which proofs that solving traveling salesman problem through graph partition scheme is good for this NP-Problem and through this we can solved this intractable problem within few minutes.Keywords: Graph Partitioning Scheme, Traveling Salesman Problem.

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Agent-oriented software engineering (AOSE) is a promising approach to developing applications for dynamic open systems. If well developed, these applications can be opportunistic, taking advantage of services implemented by other developers at appropriate times. However, methodologies are needed to aid the development of systems that are both flexible enough to be opportunistic and tightly defined by the application requirements. In this paper, we investigate how developers can choose the coordination mechanisms of agents so that the agents will best fulfil application requirements in an open system.

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O objetivo da tese é analisar questões relativas à coordenação entre as políticas monetária e fiscal no Brasil após a adoção do regime de metas de inflação. Utiliza-se de um modelo de metas de inflação para uma economia pequena e aberta para a incorporação um bloco de equações que descrevem a dinâmica das variáveis fiscais. Tendo por base os conceitos de Leeper (1991), ambas as entidades, Banco Central e Tesouro Nacional, podem agir de forma ativa ou passiva, e será este comportamento estratégico que determinará a eficiência da política monetária. Foram estimados os parâmetros que calibram o modelo e feitas as simulações para alguns dos choques que abalaram a economia brasileira nos últimos anos. Os resultados mostraram que nos arranjos em que a autoridade fiscal reage a aumentos de dívida pública com alterações no superávit primário, a trajetória de ajuste das variáveis frente a choques tende a ser, na maioria dos casos, menos volátil propiciando uma atuação mais eficiente do Banco Central. Nestes arranjos, o Banco Central não precisa tomar para si funções que são inerentes ao Tesouro. Também são analisadas as variações no comportamento do Banco Central e do Tesouro Nacional em função de diferentes composições da dívida pública. Os resultados mostram que a estrutura do endividamento público será benéfica, ou não, à condução das políticas monetária e fiscal, dependendo do tipo de choque enfrentado. O primeiro capítulo, introdutório, procura contextualizar o regime de metas de inflação brasileiro e descrever, sucintamente, a evolução da economia brasileira desde sua implantação. No segundo capítulo são analisados os fundamentos teóricos do regime de metas de inflação, sua origem e principais componentes; em seguida, são apresentados, as regras de política fiscal necessárias à estabilidade de preços e o problema da dominância fiscal no âmbito da economia brasileira. O terceiro capítulo apresenta a incorporação do bloco de equações fiscais no modelo de metas de inflação para economia aberta proposto por Svensson (2000), e as estimações e calibrações dos seus parâmetros para a economia brasileira. O quarto capítulo discute as diferentes formas de coordenação entre as autoridades monetária e fiscal e a atuação ótima do Banco Central. O quinto capítulo tem como base a mais eficiente forma de coordenação obtida no capítulo anterior para analisar as mudanças no comportamento da autoridade monetária e fiscal frente a diferentes estruturas de prazos e indexadores da dívida pública que afetam suas elasticidades, juros, inflação e câmbio.

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This paper studies how constraints on the timing of actions affect equilibrium in intertemporal coordination problems. The model exhibits a unique symmetric equilibrium in cut-o¤ strategies. The risk-dominant action of the underlying one-shot game is selected when the option to delay effort is commensurate with the option to wait longer for others' actions. The possibility of waiting longer for the actions of others enhances coordination, but the option of delaying one s actions can induce severe coordination failures: if agents are very patient, they might get arbitrarily low expected payoffs even in cases where coordination would yield arbitrarily large returns.

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Fundamental models of money, while explicit about the frictions that render money essential, are silent on how agents actually coordinate in its use. This paper studies this coordination problem, providing an endogenous map between the primitives of the environment and the beliefs on the acceptability of money. We show that an increase in the frequency of trade meetings, besides its direct impact on payo¤s, facilitates coordination. In particular, for a large enough frequency of trade meetings, agents always coordinate in the use of money.