787 resultados para Gradient-based approaches
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In the complex landscape of public education, participants at all levels are searching for policy and practice levers that can raise overall performance and close achievement gaps. The collection of articles in this edition of the Journal of Applied Research on Children takes a big step toward providing the tools and tactics needed for an evidence-based approach to educational policy and practice.
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We present a technique to reconstruct the electromagnetic properties of a medium or a set of objects buried inside it from boundary measurements when applying electric currents through a set of electrodes. The electromagnetic parameters may be recovered by means of a gradient method without a priori information on the background. The shape, location and size of objects, when present, are determined by a topological derivative-based iterative procedure. The combination of both strategies allows improved reconstructions of the objects and their properties, assuming a known background.
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Laser processing has been the tool of choice last years to develop improved concepts in contact formation for high efficiency crystalline silicon (c-Si) solar cells. New concepts based on standard laser fired contacts (LFC) or advanced laser doping (LD) techniques are optimal solutions for both the front and back contacts of a number of structures with growing interest in the c-Si PV industry. Nowadays, substantial efforts are underway to optimize these processes in order to be applied industrially in high efficiency concepts. However a critical issue in these devices is that, most of them, demand a very low thermal input during the fabrication sequence and a minimal damage of the structure during the laser irradiation process. Keeping these two objectives in mind, in this work we discuss the possibility of using laser-based processes to contact the rear side of silicon heterojunction (SHJ) solar cells in an approach fully compatible with the low temperature processing associated to these devices. First we discuss the possibility of using standard LFC techniques in the fabrication of SHJ cells on p-type substrates, studying in detail the effect of the laser wavelength on the contact quality. Secondly, we present an alternative strategy bearing in mind that a real challenge in the rear contact formation is to reduce the damage induced by the laser irradiation. This new approach is based on local laser doping techniques previously developed by our groups, to contact the rear side of p-type c-Si solar cells by means of laser processing before rear metallization of dielectric stacks containing Al2O3. In this work we demonstrate the possibility of using this new approach in SHJ cells with a distinct advantage over other standard LFC techniques.
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One of the main challenges for intelligent vehicles is the capability of detecting other vehicles in their environment, which constitute the main source of accidents. Specifically, many methods have been proposed in the literature for video-based vehicle detection. Most of them perform supervised classification using some appearance-related feature, in particular, symmetry has been extensively utilized. However, an in-depth analysis of the classification power of this feature is missing. As a first contribution of this paper, a thorough study of the classification performance of symmetry is presented within a Bayesian decision framework. This study reveals that the performance of symmetry-based classification is very limited. Therefore, as a second contribution, a new gradient-based descriptor is proposed for vehicle detection. This descriptor exploits the known rectangular structure of vehicle rears within a Histogram of Gradients (HOG)-based framework. Experiments show that the proposed descriptor outperforms largely symmetry as a feature for vehicle verification, achieving classification rates over 90%.
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The extension to new languages is a well known bottleneck for rule-based systems. Considerable human effort, which typically consists in re-writing from scratch huge amounts of rules, is in fact required to transfer the knowledge available to the system from one language to a new one. Provided sufficient annotated data, machine learning algorithms allow to minimize the costs of such knowledge transfer but, up to date, proved to be ineffective for some specific tasks. Among these, the recognition and normalization of temporal expressions still remains out of their reach. Focusing on this task, and still adhering to the rule-based framework, this paper presents a bunch of experiments on the automatic porting to Italian of a system originally developed for Spanish. Different automatic rule translation strategies are evaluated and discussed, providing a comprehensive overview of the challenge.
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With the increasing availability of effective, evidence-based physical activity interventions, widespread diffusion is needed. We examine conceptual foundations for research on dissemination and diffusion of physical activity interventions; describe two school-based program examples; review examples of dissemination and diffusion research on other health behaviors; and examine policies that may accelerate the diffusion process. Lack of dissemination and diffusion evaluation research and policy advocacy is one of the factors limiting the impact of evidence-based physical activity interventions on public health. There is the need to collaborate with policy experts from other fields to improve the interdisciplinary science base for dissemination and diffusion. The promise of widespread adoption of evidence-based physical activity interventions to improve public health is sufficient to justify devotion of substantial resources to the relevant research on dissemination and diffusion.
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The failures of traditional target-species management have led many to propose an ecosystem approach to fisheries to promote sustainability. The ecosystem approach is necessary, especially to account for fishery-ecosystem interactions, but by itself is not sufficient to address two important factors contributing to unsustainable fisheries: inappropriate incentives bearing on fishers and the ineffective governance that frequently exists in commercial, developed fisheries managed primarily by total-harvest limits and input controls. We contend that much greater emphasis must be placed on fisher motivation when managing fisheries. Using evidence from more than a dozen natural experiments in commercial fisheries, we argue that incentive-based approaches that better specify community and individual harvest or territorial rights and price ecosystem services and that are coupled with public research, monitoring, and effective oversight promote sustainable fisheries.
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This study presents some quantitative evidence from a number of simulation experiments on the accuracy of the productivitygrowth estimates derived from growthaccounting (GA) and frontier-based methods (namely data envelopment analysis-, corrected ordinary least squares-, and stochastic frontier analysis-based malmquist indices) under various conditions. These include the presence of technical inefficiency, measurement error, misspecification of the production function (for the GA and parametric approaches) and increased input and price volatility from one period to the next. The study finds that the frontier-based methods usually outperform GA, but the overall performance varies by experiment. Parametric approaches generally perform best when there is no functional form misspecification, but their accuracy greatly diminishes otherwise. The results also show that the deterministic approaches perform adequately even under conditions of (modest) measurement error and when measurement error becomes larger, the accuracy of all approaches (including stochastic approaches) deteriorates rapidly, to the point that their estimates could be considered unreliable for policy purposes.
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Relationship-based approaches to leadership (e.g., Leader–Member Exchange theory) currently represent one of the most popular approaches to understanding workplace leadership. Although the concept of “relationship” is central to these approaches, generally this has not been well articulated and is often conceptualized simply in terms of relationship quality between the leader and the follower. In contrast, research in the wider relationship science domain provides a more detailed exposition of relationships and how they form and develop. We propose that research and methodology developed in relationship science (i.e., close relationships) can enhance understanding of the leader–follower relationship and therefore advance theory in this area. To address this issue, we organize our review in two areas. First, we examine how a social cognitive approach to close relationships can benefit an understanding of the leader–follower relationship (in terms of structure, content, and processes). Second, we show how the research designs and methodologies that have been developed in relationship science can be applied to understand better the leader–follower relationship. The cross-fertilization of research from the close relationships literature to understanding the leader–follower relationship provides new insights into leadership processes and potential avenues for further research. Copyright © 2013 John Wiley & Sons, Ltd.
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The research described in this PhD thesis focuses on proteomics approaches to study the effect of oxidation on the modification status and protein-protein interactions of PTEN, a redox-sensitive phosphatase involved in a number of cellular processes including metabolism, apoptosis, cell proliferation, and survival. While direct evidence of a redox regulation of PTEN and its downstream signaling has been reported, the effect of cellular oxidative stress or direct PTEN oxidation on PTEN structure and interactome is still poorly defined. In a first study, GST-tagged PTEN was directly oxidized over a range of hypochlorous acid (HOCl) concentration, assayed for phosphatase activity, and oxidative post-translational modifications (oxPTMs) were quantified using LC-MS/MS-based label-free methods. In a second study, GSTtagged PTEN was prepared in a reduced and reversibly H2O2-oxidized form, immobilized on a resin support and incubated with HCT116 cell lysate to capture PTEN interacting proteins, which were analyzed by LC-MS/MS and comparatively quantified using label-free methods. In parallel experiments, HCT116 cells transfected with a GFP-tagged PTEN were treated with H2O2 and PTENinteracting proteins immunoprecipitated using standard methods. Several high abundance HOCl-induced oxPTMs were mapped, including those taking place at amino acids known to be important for PTEN phosphatase activity and protein-protein interactions, such as Met35, Tyr155, Tyr240 and Tyr315. A PTEN redox interactome was also characterized, which identified a number of PTEN-interacting proteins that vary with the reversible inactivation of PTEN caused by H2O2 oxidation. These included new PTEN interactors as well as the redox proteins peroxiredoxin-1 (Prdx1) and thioredoxin (Trx), which are known to be involved in the recycling of PTEN active site following H2O2-induced reversible inactivation. The results suggest that the oxidative modification of PTEN causes functional alterations in PTEN structure and interactome, with fundamental implications for the PTEN signaling role in many cellular processes, such as those involved in the pathophysiology of disease and ageing.
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This study explored the relative value of behavioral and cognitive psychology as the basis of instruction for underprepared college students enrolled in developmental reading courses. Specifically this study examined the effects of a metacognitive strategy-based instructional approach (MSIA) modeling a metacognitive self-questioning technique (MSQT) versus a traditional skills-based instructional approach (SIA) on the Nelson-Denny reading comprehension scores of college developmental readers and whether there were significant differences in achievement based on instructional method used and on the sex of students. The sample consisted of 100 college developmental reading students who were enrolled in six intact sections of a reading course (REA0002). Participants completed a pretest of the comprehension subtest of the Nelson-Denny Reading Test (Form G). Three of these classes (n = 49) were taught using metacognitive-strategy instruction and three classes (n = 51) were instructed using skills-based instruction. They then received a semester of instruction intended to improve their reading comprehension. At the end of the semester, participants completed a post-test of the Nelson-Denny Reading Comprehension Test (Form H). A two (Between) x one (Within) Repeated Measures Analysis of Variance (ANOVA) was utilized to test each of the hypotheses of this study. Results showed that there were no significant differences in reading comprehension between the groups receiving the different instructional treatments and no differences in reading comprehension between the men and women participants. Based on the findings, implications for research and recommendations for future research were discussed.