971 resultados para Convergence model


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The contemporary individual finds on the Internet and especially on the Web facilitating conditions to build a basic infrastructure based on the concept of commons. He also finds favorable conditions which allow him to collaborate and share resources for the creation, use, reuse, access and dissemination of information. However, he also faces obstacles such as Copyright (Law 9610/98 in Brazil). An alternative is Creative Commons which not only allows the elaboration, use and dissemination of information under legal conditions but also function as a facilitator for the development of informational commons. This paper deals with this scenario.

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The contemporary individual finds on the Internet and especially on the Web facilitating conditions to build a basic infrastructure based on the concept of commons. He also finds favorable conditions which allow him to collaborate and share resources for the creation, use, reuse, access and dissemination of information. However, he also faces obstacles such as Copyright (Law 9610/98 in Brazil). An alternative is Creative Commons which not only allows the elaboration, use and dissemination of information under legal conditions but also function as a facilitator for the development of informational commons. This paper deals with this scenario.

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Purpose. The focus of maternal role development, historically, has been on the tasks and processes during pregnancy as they relate to postpartum role transition. The purpose of this study was to investigate how women hospitalized with high-risk pregnancy cognitively construct pregnancy and impending motherhood. ^ Design. The study employed a triangulation design using a convergence model with a dominant focused ethnographic approach. ^ Setting. The antepartum units of two tertiary care centers in a large metropolitan city in southeast Texas. ^ Sample. Data saturation was determined with thirteen (13) primigravid women who had been hospitalized more than 72 hours with preterm labor (PTL) or preterm premature rupture of membranes (PPROM) who subsequently delivered seventeen (17) infants which included 4 sets of twins. ^ Methods. Open-ended, semi-structured interviews and field work were used to explore the development of maternal role in this population. After collecting descriptive data, long individual interviews were conducted and the Prenatal Self Evaluation Questionnaire (PSEQ), an instrument to measure prenatal adaptation to pregnancy, was administered. The interview focused on exploring the woman's experiences of pregnancy and impending motherhood while hospitalized. Interview data and field notes were coded and analyzed using qualitative thematic analytic techniques. The PSEQ was scored and the findings of the qualitative data and PSEQ data were compared. ^ Findings. Thematic analysis of the qualitative data provided an understanding of the cognitive process that occurs as the pregnant woman builds a relationship with the fetus. Thematic analysis resulted in a conceptual model with two complementary components that occur throughout the pregnancy: Establishing a Relationship and Dynamic Equilibrium. Establishing a Relationship includes subthemes of: Courting, Building a Connection, and Engagement. Dynamic equilibrium is the balance between expectations and reality and exists regardless of pregnancy complications. The negotiation of this potential imbalance is triggered by uncertainty, loss of autonomy and control, and isolation and is exacerbated by the high-risk pregnancy and subsequent hospitalization. These triggers can serve as obstacles to maternal role development, but may be mediated by external support from friends and family or health care providers. Support from others may come in the form of anticipatory guidance, presence, or activities that promote self-agency. PSEQ scores were similar to previous reports, but due to the small sample, scores were used primarily for comparison to qualitative data. The qualitative findings were congruent with the PSEQ findings in all of the subscales except in the concern for the well-being of the baby. Interview reports included comments demonstrating significant concern for the well-being of the infant, yet the related subscale did not demonstrate such concern. ^ Conclusions. An understanding of the cognitive process involved in establishing a relationship with the developing fetus related to impending motherhood and the importance of dynamic equilibrium can allow healthcare providers and those who interact with pregnant women to support development of the maternal role and anticipate those barriers that may impede that process. Findings from this study identify those triggers and mediators that influence development of the maternal role and suggest potential intervening strategies for those involved in the care of childbearing families. ^

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The expectation-maximization (EM) algorithm has been of considerable interest in recent years as the basis for various algorithms in application areas of neural networks such as pattern recognition. However, there exists some misconceptions concerning its application to neural networks. In this paper, we clarify these misconceptions and consider how the EM algorithm can be adopted to train multilayer perceptron (MLP) and mixture of experts (ME) networks in applications to multiclass classification. We identify some situations where the application of the EM algorithm to train MLP networks may be of limited value and discuss some ways of handling the difficulties. For ME networks, it is reported in the literature that networks trained by the EM algorithm using iteratively reweighted least squares (IRLS) algorithm in the inner loop of the M-step, often performed poorly in multiclass classification. However, we found that the convergence of the IRLS algorithm is stable and that the log likelihood is monotonic increasing when a learning rate smaller than one is adopted. Also, we propose the use of an expectation-conditional maximization (ECM) algorithm to train ME networks. Its performance is demonstrated to be superior to the IRLS algorithm on some simulated and real data sets.

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The role of convergence feedback on the stability of a coupled ocean‐atmosphere system is studied using model III of Hirst (1986). It is shown that the unstable coupled mode found by Hirst is greatly modified by the convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes have very weak dependence on the wave number. These results may explain the behaviour of some coupled models and to some extent provide a mechanism for the observed aperiodicity of the El‐Nino and Southern Oscillation (ENSO) events.

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A class of model reference adaptive control system which make use of an augmented error signal has been introduced by Monopoli. Convergence problems in this attractive class of systems have been investigated in this paper using concepts from hyperstability theory. It is shown that the condition on the linear part of the system has to be stronger than the one given earlier. A boundedness condition on the input to the linear part of the system has been taken into account in the analysis - this condition appears to have been missed in the previous applications of hyperstability theory. Sufficient conditions for the convergence of the adaptive gain to the desired value are also given.

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We study the effects of population size in the Peck-Shell analysis of bank runs. We find that a contract featuring equal-treatment for almost all depositors of the same type approximates the optimum. Because the approximation also satisfies Green-Lin incentive constraints, when the planner discloses positions in the queue, welfare in these alternative specifications are sandwiched. Disclosure, however, it is not needed since our approximating contract is not subject to runs.

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A neural model for solving nonlinear optimization problems is presented in this paper. More specifically, a modified Hopfield network is developed and its internal parameters are computed using the valid-subspace technique. These parameters guarantee the convergence of the network to the equilibrium points that represent an optimal feasible solution. The network is shown to be completely stable and globally convergent to the solutions of nonlinear optimization problems. A study of the modified Hopfield model is also developed to analyze its stability and convergence. Simulation results are presented to validate the developed methodology.

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Fast-flowing ice streams discharge most of the ice from the interior of the Antarctic Ice Sheet coastward. Understanding how their tributary organisation is governed and evolves is essential for developing reliable models of the ice sheet's response to climate change. Despite much research on ice-stream mechanics, this problem is unsolved, because the complexity of flow within and across the tributary networks has hardly been interrogated. Here I present the first map of planimetric flow convergence across the ice sheet, calculated from satellite measurements of ice surface velocity, and use it to explore this complexity. The convergence map of Antarctica elucidates how ice-stream tributaries draw ice from the interior. It also reveals curvilinear zones of convergence along lateral shear margins of streaming, and abundant convergence ripples associated with nonlinear ice rheology and changes in bed topography and friction. Flow convergence on ice-stream tributaries and their feeding zones is markedly uneven, and interspersed with divergence at distances of the order of kilometres. For individual drainage basins as well as the ice sheet as a whole, the range of convergence and divergence decreases systematically with flow speed, implying that fast flow cannot converge or diverge as much as slow flow. I therefore deduce that flow in ice-stream networks is subject to mechanical regulation that limits flow-orthonormal strain rates. These properties and the gridded data of convergence and flow-orthonormal strain rate in this archive provide targets for ice- sheet simulations and motivate more research into the origin and dynamics of tributarization.

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Recent investigations into cross-country convergence follow Mankiw, Romer, and Weil (1992) in using a log-linear approximation to the Swan-Solow growth model to specify regressions. These studies tend to assume a common and exogenous technology. In contrast, the technology catch-up literature endogenises the growth of technology. The use of capital stock data renders the approximations and over-identification of the Mankiw model unnecessary and enables us, using dynamic panel estimation, to estimate the separate contributions of diminishing returns and technology transfer to the rate of conditional convergence. We find that both effects are important.

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This paper proposes a novel relative entropy rate (RER) based approach for multiple HMM (MHMM) approximation of a class of discrete-time uncertain processes. Under different uncertainty assumptions, the model design problem is posed either as a min-max optimisation problem or stochastic minimisation problem on the RER between joint laws describing the state and output processes (rather than the more usual RER between output processes). A suitable filter is proposed for which performance results are established which bound conditional mean estimation performance and show that estimation performance improves as the RER is reduced. These filter consistency and convergence bounds are the first results characterising multiple HMM approximation performance and suggest that joint RER concepts provide a useful model selection criteria. The proposed model design process and MHMM filter are demonstrated on an important image processing dim-target detection problem.