885 resultados para Heteroskedasticity-based identification
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Objective: To investigate whether advanced visualizations of spirography-based objective measures are useful in differentiating drug-related motor dysfunctions between Off and dyskinesia in Parkinson’s disease (PD). Background: During the course of a 3 year longitudinal clinical study, in total 65 patients (43 males and 22 females with mean age of 65) with advanced PD and 10 healthy elderly (HE) subjects (5 males and 5 females with mean age of 61) were assessed. Both patients and HE subjects performed repeated and time-stamped assessments of their objective health indicators using a test battery implemented on a telemetry touch screen handheld computer, in their home environment settings. Among other tasks, the subjects were asked to trace a pre-drawn Archimedes spiral using the dominant hand and repeat the test three times per test occasion. Methods: A web-based framework was developed to enable a visual exploration of relevant spirography-based kinematic features by clinicians so they can in turn evaluate the motor states of the patients i.e. Off and dyskinesia. The system uses different visualization techniques such as time series plots, animation, and interaction and organizes them into different views to aid clinicians in measuring spatial and time-dependent irregularities that could be associated with the motor states. Along with the animation view, the system displays two time series plots for representing drawing speed (blue line) and displacement from ideal trajectory (orange line). The views are coordinated and linked i.e. user interactions in one of the views will be reflected in other views. For instance, when the user points in one of the pixels in the spiral view, the circle size of the underlying pixel increases and a vertical line appears in the time series views to depict the corresponding position. In addition, in order to enable clinicians to observe erratic movements more clearly and thus improve the detection of irregularities, the system displays a color-map which gives an idea of the longevity of the spirography task. Figure 2 shows single randomly selected spirals drawn by a: A) patient who experienced dyskinesias, B) HE subject, and C) patient in Off state. Results: According to a domain expert (DN), the spirals drawn in the Off and dyskinesia motor states are characterized by different spatial and time features. For instance, the spiral shown in Fig. 2A was drawn by a patient who showed symptoms of dyskinesia; the drawing speed was relatively high (cf. blue-colored time series plot and the short timestamp scale in the x axis) and the spatial displacement was high (cf. orange-colored time series plot) associated with smooth deviations as a result of uncontrollable movements. The patient also exhibited low amount of hesitation which could be reflected both in the animation of the spiral as well as time series plots. In contrast, the patient who was in the Off state exhibited different kinematic features, as shown in Fig. 2C. In the case of spirals drawn by a HE subject, there was a great precision during the drawing process as well as unchanging levels of time-dependent features over the test trial, as seen in Fig. 2B. Conclusions: Visualizing spirography-based objective measures enables identification of trends and patterns of drug-related motor dysfunctions at the patient’s individual level. Dynamic access of visualized motor tests may be useful during the evaluation of drug-related complications such as under- and over-medications, providing decision support to clinicians during evaluation of treatment effects as well as improve the quality of life of patients and their caregivers. In future, we plan to evaluate the proposed approach by assessing within- and between-clinician variability in ratings in order to determine its actual usefulness and then use these ratings as target outcomes in supervised machine learning, similarly as it was previously done in the study performed by Memedi et al. (2013).
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Internet research methods in nursing science are less developed than in other sciences. We choose to present an approach to conducting nursing research on an internet-based forum. This paper presents LiLEDDA, a six-step forum-based netnographic research method for nursing science. The steps consist of: 1. Literature review and identification of the research question(s); 2. Locating the field(s) online; 3. Ethical considerations; 4. Data gathering; 5. Data analysis and interpretation; and 6. Abstractions and trustworthiness. Traditional research approaches are limiting when studying non-normative and non-mainstream life-worlds and their cultures. We argue that it is timely to develop more up-to-date research methods and study designs applicable to nursing science that reflect social developments and human living conditions that tend to be increasingly online-based.
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As técnicas tradicionais de avaliação de rentabilidade apresentam características que resultam eficazes no que tange aos aspectos econômicos da análise de investimentos. No entanto, a validade das informações fornecidas por estes métodos depende dos dados incluídos na avaliação. Neste sentido, em função da complexidade e do inter-relacionamento existente nos processos produtivos de empresas, as alterações proporcionadas por um investimento podem ter impacto sobre áreas que não estão diretamente envolvidas com o projeto a ser implementado. Este fato dificulta a identificação e conseqüente inclusão da totalidade dos fatores que causam impacto na análise do projeto. Além disso, impactos relacionados a atividades indiretas não possuem uma metodologia que permita sua quantificação. Como forma de abordar o problema, este trabalho apresenta uma sistemática de avaliação de investimentos que, através de uma seqüência estruturada de passos e com a utilização das informações geradas por um sistema de custeio do tipo ABC (Activity-Based Costing), possibilita incluir na análise impactos indiretos gerados pelo projeto. A aplicação desta sistemática em um projeto de substituição de equipamento numa empresa do ramo industrial mostra que as informações geradas complementam aquelas obtidas quando da aplicação das técnicas tradicionais. Desta forma, foi possível avaliar o impacto econômico provocado por possíveis alterações nos setores não diretamente ligados ao projeto.
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Com a globalização do mercado e o alto nível de competitividade no setor educacional, as organizações, para manterem-se, devem ser ágeis e competentes. Neste contexto, a gestão eficiente dos recursos e a obtenção de informações precisas que apóiem a tomada de decisão dependerão, em grande parte, de um sistema de informações de custos. Este sistema deverá ter como base um método de custeio que forneça informações, a fim de atender as distintas necessidades dos gestores dos diversos níveis hierárquico e das diversas áreas de atuação. O trabalho consiste no estudo de uma metodologia de custeio aplicável a uma Instituição de Ensino Superior – IES privada, a qual atenda as três perspectivas que são fornecer informações para embasar a composição dos preços, para apoiar o processo decisório e para o planejamento e controle de gastos. Para tanto, partiu-se da pesquisa bibliográfica no levantamento do estado da arte relacionada ao tema. Com o estudo de caso buscou-se a identificação das necessidades de informações de custos, demandadas pelos gestores da IES, por meio de pesquisa qualitativa. A partir dessa identificação, as necessidades foram cruzadas com os métodos de custeio existentes, o que permitiu a identificação do método mais adequado a IES. Nesta etapa foi possível o cruzamento entre a teoria e a prática, onde foram comparados o método proposto em relação ao atual método adotado pela IES o que possibilitou a identificação das deficiências do modelo atual e suas causas. A partir disto, propõe-se uma sistemática mais adequada para apoiar a tomada de decisão, com o intuito de melhoria do desempenho da instituição. Os resultados obtidos demonstram o cumprimento do objetivo onde, considerando as necessidades de informações de custos dos gestores, o método de custeio por atividades é o mais adequado para o suporte a gestão da IES.
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This paper presents semiparametric estimators of changes in inequality measures of a dependent variable distribution taking into account the possible changes on the distributions of covariates. When we do not impose parametric assumptions on the conditional distribution of the dependent variable given covariates, this problem becomes equivalent to estimation of distributional impacts of interventions (treatment) when selection to the program is based on observable characteristics. The distributional impacts of a treatment will be calculated as differences in inequality measures of the potential outcomes of receiving and not receiving the treatment. These differences are called here Inequality Treatment Effects (ITE). The estimation procedure involves a first non-parametric step in which the probability of receiving treatment given covariates, the propensity-score, is estimated. Using the inverse probability weighting method to estimate parameters of the marginal distribution of potential outcomes, in the second step weighted sample versions of inequality measures are computed. Root-N consistency, asymptotic normality and semiparametric efficiency are shown for the semiparametric estimators proposed. A Monte Carlo exercise is performed to investigate the behavior in finite samples of the estimator derived in the paper. We also apply our method to the evaluation of a job training program.
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Exchange rate misalignment assessment is becoming more relevant in recent period particularly after the nancial crisis of 2008. There are di erent methodologies to address real exchange rate misalignment. The real exchange misalignment is de ned as the di erence between actual real e ective exchange rate and some equilibrium norm. Di erent norms are available in the literature. Our paper aims to contribute to the literature by showing that Behavioral Equilibrium Exchange Rate approach (BEER) adopted by Clark & MacDonald (1999), Ubide et al. (1999), Faruqee (1994), Aguirre & Calderón (2005) and Kubota (2009) among others can be improved in two following manners. The rst one consists of jointly modeling real e ective exchange rate, trade balance and net foreign asset position. The second one has to do with the possibility of explicitly testing over identifying restrictions implied by economic theory and allowing the analyst to show that these restrictions are not falsi ed by the empirical evidence. If the economic based identifying restrictions are not rejected it is also possible to decompose exchange rate misalignment in two pieces, one related to long run fundamentals of exchange rate and the other related to external account imbalances. We also discuss some necessary conditions that should be satis ed for disrcarding trade balance information without compromising exchange rate misalignment assessment. A statistical (but not a theoretical) identifying strategy for calculating exchange rate misalignment is also discussed. We illustrate the advantages of our approach by analyzing the Brazilian case. We show that the traditional approach disregard important information of external accounts equilibrium for this economy.
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Differences-in-Differences (DID) is one of the most widely used identification strategies in applied economics. However, how to draw inferences in DID models when there are few treated groups remains an open question. We show that the usual inference methods used in DID models might not perform well when there are few treated groups and errors are heteroskedastic. In particular, we show that when there is variation in the number of observations per group, inference methods designed to work when there are few treated groups tend to (under-) over-reject the null hypothesis when the treated groups are (large) small relative to the control groups. This happens because larger groups tend to have lower variance, generating heteroskedasticity in the group x time aggregate DID model. We provide evidence from Monte Carlo simulations and from placebo DID regressions with the American Community Survey (ACS) and the Current Population Survey (CPS) datasets to show that this problem is relevant even in datasets with large numbers of observations per group. We then derive an alternative inference method that provides accurate hypothesis testing in situations where there are few treated groups (or even just one) and many control groups in the presence of heteroskedasticity. Our method assumes that we can model the heteroskedasticity of a linear combination of the errors. We show that this assumption can be satisfied without imposing strong assumptions on the errors in common DID applications. With many pre-treatment periods, we show that this assumption can be relaxed. Instead, we provide an alternative inference method that relies on strict stationarity and ergodicity of the time series. Finally, we consider two recent alternatives to DID when there are many pre-treatment periods. We extend our inference methods to linear factor models when there are few treated groups. We also derive conditions under which a permutation test for the synthetic control estimator proposed by Abadie et al. (2010) is robust to heteroskedasticity and propose a modification on the test statistic that provided a better heteroskedasticity correction in our simulations.
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Differences-in-Differences (DID) is one of the most widely used identification strategies in applied economics. However, how to draw inferences in DID models when there are few treated groups remains an open question. We show that the usual inference methods used in DID models might not perform well when there are few treated groups and errors are heteroskedastic. In particular, we show that when there is variation in the number of observations per group, inference methods designed to work when there are few treated groups tend to (under-) over-reject the null hypothesis when the treated groups are (large) small relative to the control groups. This happens because larger groups tend to have lower variance, generating heteroskedasticity in the group x time aggregate DID model. We provide evidence from Monte Carlo simulations and from placebo DID regressions with the American Community Survey (ACS) and the Current Population Survey (CPS) datasets to show that this problem is relevant even in datasets with large numbers of observations per group. We then derive an alternative inference method that provides accurate hypothesis testing in situations where there are few treated groups (or even just one) and many control groups in the presence of heteroskedasticity. Our method assumes that we know how the heteroskedasticity is generated, which is the case when it is generated by variation in the number of observations per group. With many pre-treatment periods, we show that this assumption can be relaxed. Instead, we provide an alternative application of our method that relies on assumptions about stationarity and convergence of the moments of the time series. Finally, we consider two recent alternatives to DID when there are many pre-treatment groups. We extend our inference method to linear factor models when there are few treated groups. We also propose a permutation test for the synthetic control estimator that provided a better heteroskedasticity correction in our simulations than the test suggested by Abadie et al. (2010).
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The purpose of this study was to identify whether activity modeling framework supports problem analysis and provides a traceable and tangible connection from the problem identification up to solution modeling. Methodology validation relied on a real problem from a Portuguese teaching syndicate (ASPE), regarding courses development and management. The study was carried out with a perspective to elaborate a complete tutorial of how to apply activity modeling framework to a real world problem. Within each step of activity modeling, we provided a summary elucidation of the relevant elements required to perform it, pointed out some improvements and applied it to ASPE’s real problem. It was found that activity modeling potentiates well structured problem analysis as well as provides a guiding thread between problem and solution modeling. It was concluded that activity-based task modeling is key to shorten the gap between problem and solution. The results revealed that the solution obtained using activity modeling framework solved the core concerns of our customer and allowed them to enhance the quality of their courses development and management. The principal conclusion was that activity modeling is a properly defined methodology that supports software engineers in problem analysis, keeping a traceable guide among problem and solution.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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O café é um dos principais produtos agrícolas, sendo considerado o segundo item em importância do comércio internacional de commodities. O gênero Coffea pertence à família Rubiaceae que também inclui outras plantas importantes. Este gênero contém aproximadamente 100 espécies, mas a produção comercial é baseada somente em duas espécies, Coffea arabica e Coffea canephora, que representam aproximadamente 70 % e 30 % do mercado total de café, respectivamente. O Projeto Genoma Café Brasileiro foi desenvolvido com o objetivo de disponibilizar os modernos recursos da genômica à comunidade científica e aos diferentes segmentos da cadeia produtiva do café. Para isso, foram seqüenciados 214.964 clones escolhidos aleatoriamente de 37 bibliotecas de cDNA de C. arabica, C. canephora e C. racemosa representando estádios específicos do desenvolvimento de células e de tecidos do cafeeiro, resultando em 130.792, 12.381 e 10.566 seqüências de cada espécie, respectivamente, após processo de trimagem. Os ESTs foram agrupados em 17.982 contigs e em 32.155 singletons. A comparação destas seqüências pelo programa BLAST revelou que 22 % não tiveram nenhuma similaridade significativa às seqüências no banco de dados do National Center for Biotechnology Information (de função conhecida ou desconhecida). A base de dados de ESTs do cafeeiro resultou na identificação de cerca de 33.000 unigenes diferentes. Os resultados de anotação das seqüências foram armazenados em base de dados online em http://www.lge.ibi.unicamp.br/cafe. Os recursos desenvolvidos por este projeto disponibilizam ferramentas genéticas e genômicas que podem ser decisivas para a sustentabilidade, a competitividade e a futura viabilidade da agroindústria cafeeira nos mercados interno e externo.
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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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This paper presents a method for automatic identification of dust devils tracks in MOC NA and HiRISE images of Mars. The method is based on Mathematical Morphology and is able to successfully process those images despite their difference in spatial resolution or size of the scene. A dataset of 200 images from the surface of Mars representative of the diversity of those track features was considered for developing, testing and evaluating our method, confronting the outputs with reference images made manually. Analysis showed a mean accuracy of about 92%. We also give some examples on how to use the results to get information about dust devils, namelly mean width, main direction of movement and coverage per scene. (c) 2012 Elsevier Ltd. All rights reserved.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)