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‣ A small area 8 bits 50 MHz CMOS DAC for Bluetooth transmitter

HERNANDEZ, Hugo; NOIJE, Wilhelmus Van; ROA, Elkim; NAVARRO, Joao
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
562.99727%
This paper presents a small-area CMOS current-steering segmented digital-to-analog converter (DAC) design intended for RF transmitters in 2.45 GHz Bluetooth applications. The current-source design strategy is based on an iterative scheme whose variables are adjusted in a simple way, minimizing the area and the power consumption, and meeting the design specifications. A theoretical analysis of static-dynamic requirements and a new layout strategy to attain a small-area current-steering DAC are included. The DAC was designed and implemented in 0.35 mu m CMOS technology, requiring an active area of just 200 mu m x 200 mu m. Experimental results, with a full-scale output current of 700 mu A and a 3.3 V power supply, showed a spurious-free dynamic range of 58 dB for a 1 MHz output sine wave and sampling frequency of 50 MHz, with differential and integral nonlinearity of 0.3 and 0.37 LSB, respectively.

‣ Mortalidade por AIDS e condições socioeconômicas no Município de São Paulo, 1994 a 1999.; AIDS Mortality and socioeconomic conditions in the city of São Paulo, 1994-1999.

Farias, Norma Suely de Oliveira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/06/2002 Português
Relevância na Pesquisa
560.0629%
Introdução. A influência de fatores sócioeconômicos na epidemia pelo HIV/Aids tem sido discutida na literatura científica. Objetivo. Estudar a mortalidade por Aids segundo condições sócioeconômicas no município de São Paulo, no período de 1994 a 1999, entre homens e mulheres de 15 a 49 anos (15 a 24; 25 a 49). Método. Trata-se de um estudo ecológico tendo como unidades de análise os 96 distritos e 5 áreas homogêneas, classificadas segundo o índice social para cada distrito. Foram utilizados dados secundários do PROGRAMA DE APRIMORAMENTO DAS INFORMAÇÕES DE MORTALIDADE DO MUNICÍPIO (PRÓ – AIM), estimativas populacionais do censo de 1991 e os índices sociais do Mapa da exclusão/inclusão social para a cidade. Foram calculados os coeficientes de mortalidade por Aids por sexo e idade, em cada ano e área. Foi analisada a correlação entre o logarítmo dos coeficientes de mortalidade por Aids e os índices de exclusão/inclusão social nos 96 distritos. A tendência da mortalidade por Aids foi analisada na série histórica, nas 5 áreas homogêneas. Resultados. Foi encontrada correlação negativa estatisticamente significativa entre o log dos coeficientes de mortalidade por Aids e o índice de eqüidade entre homens e mulheres de 15 a 49 anos...

‣ Problems in the interpretation of small area analysis of epidemiological data: the case of cancer incidence in the West of Scotland.

Hole, D J; Lamont, D W
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1992 Português
Relevância na Pesquisa
659.63445%
STUDY OBJECTIVE--The aim was to examine the extent to which random variation alone will produce differences in observed incidence rates between small areas which will affect measures of spatial clustering and estimates of relative risk. DESIGN--This was a study of changes in the pattern of spatial concentration of cancer incidence over a five year time period. A comparison was made of observed incidence rates for 34 tumour sites with randomly generated values and, where possible, with expected values derived from known relative risks. SETTING--Twenty six local government districts in the West of Scotland. MAIN RESULTS--A statistically significant relationship was observed between sample size and the stability of a summary measure of spatial concentration. Almost all observed highest:mean rate ratios were within the 95% confidence interval of the simulated distribution of these values. In three cases examined, both observed and simulated highest:lowest rate ratios were larger than those expected on the basis of known exposures to risk. CONCLUSIONS--In the absence of a prior hypothesis, small area analysis of epidemiological data for periods of less than 10 years will almost always give misleading results for all but the most common diseases.

‣ What is too much variation? The null hypothesis in small-area analysis.

Diehr, P; Cain, K; Connell, F; Volinn, E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1990 Português
Relevância na Pesquisa
665.7807%
A small-area analysis (SAA) in health services research often calculates surgery rates for several small areas, compares the largest rate to the smallest, notes that the difference is large, and attempts to explain this discrepancy as a function of service availability, physician practice styles, or other factors. SAAs are often difficult to interpret because there is little theoretical basis for determining how much variation would be expected under the null hypothesis that all of the small areas have similar underlying surgery rates and that the observed variation is due to chance. We developed a computer program to simulate the distribution of several commonly used descriptive statistics under the null hypothesis, and used it to examine the variability in rates among the counties of the state of Washington. The expected variability when the null hypothesis is true is surprisingly large, and becomes worse for procedures with low incidence, for smaller populations, when there is variability among the populations of the counties, and when readmissions are possible. The characteristics of four descriptive statistics were studied and compared. None was uniformly good, but the chi-square statistic had better performance than the others. When we reanalyzed five journal articles that presented sufficient data...

‣ Testing the null hypothesis in small area analysis.

Cain, K C; Diehr, P
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1992 Português
Relevância na Pesquisa
659.63445%
The goal of small area analysis is often to demonstrate that hospital admission rates or procedure rates vary greatly among regions, suggesting the occurrence of unnecessary admissions or procedures in some regions. Recent articles have shown that such variation may be largely due to chance, even if no underlying differences exist among the small areas; thus, it is important to test if the observed variation is larger than expected by chance. In this article we discuss how the appropriate method for testing the null hypothesis depends on the distribution of the number of admissions at the person level. If it is not possible for an individual to have more than one admission for a given procedure, the appropriate test is a simple chi-square test. If multiple admissions are possible, a modified chi-square test can be used to account for the excess variability due to multiple admissions. Failure to make the correct modification to the chi-square test in this latter case can result in spurious results. This underscores the importance of collecting data on multiple admissions in order to estimate the distribution of the number of admissions at the individual-patient level.

‣ A small area simulation approach to determining excess variation in dental procedure rates.

Diehr, P; Grembowski, D
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1990 Português
Relevância na Pesquisa
560.6468%
All small area analyses need to compare the observed variability in rates to that expected by chance alone, but the expected variability is usually not known. This paper uses patient-level data for five dental procedures to simulate the distributions of the summary statistics that are usually generated in such studies. These statistics are found to vary greatly even under the "null hypothesis" that all dentists are using procedures at the same rates. The simulated dentist rates are compared to observed rates obtained in a different study. These findings illustrate problems that can occur in small area analysis studies, and emphasize the importance of using statistical techniques that are appropriate for the data that are to be analyzed. Investigators should make every effort to obtain patient-level data, or at least to understand the underlying distribution of the number of procedures per patient, to avoid mistaking significant deviations from an incorrect model as evidence for significant variation among small areas.

‣ Role of individual and contextual effects in injury mortality: new evidence from small area analysis

Borrell, C; Rodriguez, M; Ferrando, J; Brugal, M; Pasarin, M; Martinez, V; Plasencia, A
Fonte: BMJ Group Publicador: BMJ Group
Tipo: Artigo de Revista Científica
Publicado em /12/2002 Português
Relevância na Pesquisa
656.7%
Objective: To analyse the role of individual and contextual variables in injury mortality inequalities from a small area analysis perspective, looking at the data for the city of Barcelona (Spain) for 1992–98.

‣ Three Essays of Applied Bayesian Modeling: Financial Return Contagion, Benchmarking Small Area Estimates, and Time-Varying Dependence

Vesper, Andrew Jay
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation
Português
Relevância na Pesquisa
666.90984%
This dissertation is composed of three chapters, each an application of Bayesian statistical models to particular research questions. In Chapter 1, we evaluate systemic risk exposure of financial institutions. Building upon traditional regime switching approaches, we propose a network model for volatility contagion to assess linkages between institutions in the financial system. Focusing empirical analysis on the financial sector, we find that network connectivity has dynamic properties, with linkages between institutions increasing immediately before the recent crisis. Out-of-sample forecasts demonstrate the ability of the model to predict losses during distress periods. We find that institutional exposure to crisis events depends upon the structure of linkages, not strictly the number of linkages. In Chapter 2, we develop procedures for benchmarking small area estimates. In sample surveys, precision can be increased by introducing small area models which "borrow strength" by incorporating auxiliary covariate information. One consequence of using small area models is that small area estimates at lower geographical levels typically will not aggregate to the estimate at the corresponding higher geographical levels. Benchmarking is the statistical procedure for reconciling these differences. Two new approaches to Bayesian benchmarking are introduced...

‣ How Good a Map? Putting Small Area Estimation to the Test

Demombynes, Gabriel; Elbers, Chris; Lanjouw, Jean O.; Lanjouw, Peter
Fonte: World Bank, Washington, DC Publicador: World Bank, Washington, DC
Português
Relevância na Pesquisa
658.841%
The authors examine the performance of small area welfare estimation. The method combines census and survey data to produce spatially disaggregated poverty and inequality estimates. To test the method, they compare predicted welfare indicators for a set of target populations with their true values. They construct target populations using actual data from a census of households in a set of rural Mexican communities. They examine estimates along three criteria: accuracy of confidence intervals, bias, and correlation with true values. The authors find that while point estimates are very stable, the precision of the estimates varies with alternative simulation methods. While the original approach of numerical gradient estimation yields standard errors that seem appropriate, some computationally less-intensive simulation procedures yield confidence intervals that are slightly too narrow. The precision of estimates is shown to diminish markedly if unobserved location effects at the village level are not well captured in underlying consumption models. With well specified models there is only slight evidence of bias...

‣ Small Area Estimation of Poverty in Rural Bhutan

World Bank
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Other Poverty Study; Economic & Sector Work
Português
Relevância na Pesquisa
559.81723%
The Small Area Estimation (SAE) of poverty in Rural Bhutan was prepared with an objective to provide a more disaggregated picture of poverty in Bhutan down to the gewog level, based on the Bhutan living standard survey 2007 and Population and Housing Census of Bhutan (PHCB) 2005. The report records the estimation process in detail and describes results of statistical tests for quality checks. According to these tests, the poverty estimates at the gewog level are reliable. The report also enhances the transparency of the process and intends to serve as a guide for future updates. According to the Poverty Analysis Report (PAR) 2007, about one-fourth of the country's population is estimated to be poor with rural poverty as high as 30.9 percent. This report, which presents some results of the SAE, compliments the PAR 2007. However, vast differences in poverty levels across dzongkhag (district) and gewog (sub-district) persist. Popular perceptions suggest that the geography of poverty and of economic affluence is accentuated at the local level...

‣ Small-area variation in health care affecting the choice of cesarean delivery: the case of a Colombian health insurer

Vecino Ortiz, Andrés Ignacio; Bardey, David; Castaño Yepes, Ramón Abel
Fonte: Facultad de Economía Publicador: Facultad de Economía
Tipo: info:eu-repo/semantics/book; info:eu-repo/semantics/acceptedVersion Formato: application/pdf
Publicado em /10/2009 Português
Relevância na Pesquisa
660.7593%
In the midst of health care reform, Colombia has succeeded in increasing health insurance coverage and the quality of health care. In spite of this, efficiency continues to be a matter of concern, and small-area variations in health care are one of the plausible causes of such inefficiencies. In order to understand this issue, we use individual data of all births from a Contributory-Regimen insurer in Colombia. We perform two different specifications of a multilevel logistic regression model. Our results reveal that hospitals account for 20% of variation on the probability of performing cesarean sections. Geographic area only explains 1/3 of the variance attributable to the hospital. Furthermore, some variables from both demand and supply sides are found to be also relevant on the probability of undergoing cesarean sections. This paper contributes to previous research by using a hierarchical model and by defining hospitals as cluster. Moreover, we also include clinical and supply induced demand variables.

‣ Low-income neighborhoods and the risk of severe pediatric injury: a small-area analysis in northern Manhattan.

Durkin, M S; Davidson, L L; Kuhn, L; O'Connor, P; Barlow, B
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1994 Português
Relevância na Pesquisa
656.7%
OBJECTIVES. The purpose of this study was to investigate the relationship between socioeconomic disadvantage and the incidence of severe childhood injury. METHODS. Small-area analysis was used to examine socioeconomic risk factors for pediatric injury resulting in hospitalization or death in Northern Manhattan, New York, NY, during a 9-year period (1983 through 1991). RESULTS. The average annual incidence of all causes of severe pediatric injury was 72.5 per 10,000 children; the case-fatality rate was 2.6%. Census tract proportions of low-income households, single-parent families, non-high school graduates, and unemployment were significant predictors of risk for both unintentional and intentional injury. Among the socioeconomic factors considered, low income was the single most important predictor of all injuries; other socioeconomic variables were not independent contributors once income was included in the model. Compared with children living in areas with few low-income households, children in areas with predominantly low-income households were more than twice as likely to receive injuries from all causes and four and one half times as likely to receive assault injuries. The effect of neighborhood income disparities on injury risk persisted after race was controlled. CONCLUSIONS. These results illuminate the impact of socioeconomic disparities on child health and point to the need for injury prevention efforts targeting low-income neighborhoods.

‣ Embedded area-constrained Willmore tori of small area in Riemannian three-manifolds I: Minimization

Ikoma, Norihisa; Malchiodi, Andrea; Mondino, Andrea
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/11/2014 Português
Relevância na Pesquisa
562.05875%
We construct embedded Willmore tori with small area constraint in Riemannian three-manifolds under some curvature condition used to prevent M\"obius degeneration. The construction relies on a Lyapunov-Schmidt reduction; to this aim we establish new geometric expansions of exponentiated small symmetric Clifford tori and analyze the sharp asymptotic behavior of degenerating tori under the action of the M\"obius group. In this first work we prove two existence results by minimizing or maximizing a suitable reduced functional, in particular we obtain embedded area-constrained Willmore tori (or, equivalently, toroidal critical points of the Hawking mass under area-constraint) in compact 3-manifolds with constant scalar curvature and in the double Schwarzschild space. In a forthcoming paper new existence theorems will be achieved via Morse theory.; Comment: 41 pages

‣ Embedded area-constrained Willmore tori of small area in Riemannian three-manifolds II: Morse Theory

Ikoma, Norihisa; Malchiodi, Andrea; Mondino, Andrea
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/11/2014 Português
Relevância na Pesquisa
564.67184%
This is the second of a series of two papers where we construct embedded Willmore tori with small area constraint in Riemannian three-manifolds. In both papers the construction relies on a Lyapunov-Schmidt reduction, the difficulty being the M\"obius degeneration of the tori. In the first paper the construction was performed via minimization, here by Morse Theory; to this aim we establish new geometric expansions of the derivative of the Willmore functional on exponentiated small Clifford tori degenerating, under the action of the M\"obius group, to small geodesic spheres with a small handle. By using these sharp asymptotics we give sufficient conditions, in terms of the ambient curvature tensors and Morse inequalities, for having existence/multiplicity of embedded tori stationary for the Willmore functional under the constraint of prescribed (sufficiently small) area.; Comment: 48 pages

‣ Sampling design variance estimation of small area estimators in the Spanish Labour Force Survey

Herrador, M.; Morales, Domingo; Esteban, M. D.; Sánchez, A.; Santamaría, Laureano; Marhuenda, Y.; Pérez, A.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2008 Português
Relevância na Pesquisa
665.0878%
The main goal of this paper is to investigate how to estimate sampling design variances of modelbased and model-assisted small area estimators in a complex survey sampling setup. For this purpose the Spanish Labour Force Survey is considered. Sample and aggregated data are taken from the Canary Islands in the second trimester of 2003 in order to obtain some small area estimators of ILO unemployment totals. Several problems arising from the application of standard small area estimation procedures to the survey are described. It is shown that standard variance estimators based on explicit formulas are not applicable in the strict sense, since the assumptions under which they are derived do not hold. In addition two resampling techniques, bootstrap and jackknife, are considered. These methods treat all the considered estimators in the same manner and therefore they can be used as performance measures to compare them. From the analysis of the obtained results, some recommendations are given.

‣ Using Census and Survey Data to Estimate Poverty and Inequality for Small Areas

Tarozzi, Alessandro; Deaton, A.
Fonte: Review of Economics and Statistics Publicador: Review of Economics and Statistics
Tipo: Artigo de Revista Científica Formato: 774776 bytes; application/pdf
Publicado em //2008 Português
Relevância na Pesquisa
563.78836%
Household expenditure survey data cannot yield precise estimates of poverty or inequality for small areas for which no or few observations are available. Census data are more plentiful, but typically exclude income and expenditure data. Recent years have seen a widespread use of small-area “poverty maps” based on census data enriched by relationships estimated from household surveys that predict variables not covered by the census. These methods are used to estimate putatively precise estimates of poverty and inequality for areas as small as 20,000 households. In this paper we argue that to usefully match survey and census data in this way requires a degree of spatial homogeneity for which the method provides no basis, and which is unlikely to be satisfied in practice. The relationships that are used to bridge the surveys and censuses are not structural but are projections of missing variables on a subset of those variables that happen to be common to the survey and the census supplemented by local census means appended to the survey. As such, the coefficients of the projections will generally vary from area to area in response to variables that are not included in the analysis. Estimates of poverty and inequality that assume homogeneity will generally be inconsistent in the presence of spatial heterogeneity...

‣ Small-area measures of income poverty

Fenton, Alex
Fonte: Centre for the Analysis of Social Exclusion, London School of Economics and Political Science Publicador: Centre for the Analysis of Social Exclusion, London School of Economics and Political Science
Tipo: Monograph; NonPeerReviewed Formato: application/pdf
Publicado em /05/2013 Português
Relevância na Pesquisa
559.63445%
This paper considers techniques for measuring the prevalence of income poverty within small areas, or “neighbourhoods”, in Britain. The ultimate purpose is applying such statistics to investigating how the micro-spatial distribution of poverty within cities and regions changes over time as a consequence of political decisions and economic events. In the paper, some general criteria for small-area poverty measures are first set out, and two broad methods, poverty proxies and modelled income estimates, are identified. Empirical analyses of the validity and coverage of poverty proxies derived from UK administrative data, such as social security benefit claims, are presented. The concluding section assesses a new poverty proxy that will be used within a wider programme of analysis of the spatial-distributional effects of tax and welfare changes and of economic trends in Britain from 2000 to 2014. Particular attention is paid to the relationship between the proxy values and other local poverty measures in different kinds of places. These suggest that the proxy is an adequate, albeit imperfect, tool for investigating changes in intra-urban distributions of poverty.

‣ Small-area measures of income poverty

Fenton, Alex
Fonte: Centre for the Analysis of Social Exclusion, The London School of Economics and Political Science Publicador: Centre for the Analysis of Social Exclusion, The London School of Economics and Political Science
Tipo: Monograph; NonPeerReviewed Formato: application/pdf
Publicado em /05/2013 Português
Relevância na Pesquisa
559.63445%
This paper considers techniques for measuring the prevalence of income poverty within small areas, or “neighbourhoods”, in Britain. The ultimate purpose is applying such statistics to investigating how the micro-spatial distribution of poverty within cities and regions changes over time as a consequence of political decisions and economic events. In the paper, some general criteria for small-area poverty measures are first set out, and two broad methods, poverty proxies and modelled income estimates, are identified. Empirical analyses of the validity and coverage of poverty proxies derived from UK administrative data, such as social security benefit claims, are presented. The concluding section assesses a new poverty proxy that will be used within a wider programme of analysis of the spatial-distributional effects of tax and welfare changes and of economic trends in Britain from 2000 to 2014. Particular attention is paid to the relationship between the proxy values and other local poverty measures in different kinds of places. These suggest that the proxy is an adequate, albeit imperfect, tool for investigating changes in intra-urban distributions of poverty.

‣ Carpal tunnel release surgery: small-area variation and impact of ambulatory surgery in the autonomous region of Valencia, Spain

Rodríguez-Martínez,Pablo; Peiró,Salvador; Librero,Julián; Bernal-Delgado,Enrique; Gisbert-Grifo,Marina; Calabuig-Pérez,Julia; Ridao-López,Manuel; Sanfélix-Gimeno,Gabriel
Fonte: Gaceta Sanitaria Publicador: Gaceta Sanitaria
Tipo: info:eu-repo/semantics/article; journal article; info:eu-repo/semantics/publishedVersion Formato: text/html; application/pdf
Publicado em 01/06/2013 Português
Relevância na Pesquisa
765.9694%
Objective: This study aimed to analyze variability in rates of carpal tunnel release surgery among the healthcare areas of the autonomous region of Valencia, and to evaluate the contribution of ambulatory surgery and referrals to private hospitals to the variability found. Methods: We carried out a cross-sectional, population-based study, describing the rates of carpal tunnel release surgery, standardized by age and sex, among areas in the region of Valencia in 2006. The observed variation was then analyzed using small-area analysis methods. Data from hospital admissions, referrals to private hospitals, population statistics and hospital resources were used to construct standardized rates, and Spearman's correlation was used to test the association with surgical setting and hospital resources. Results: There were 8.2 carpal tunnel release surgeries per 10,000 inhabitants in the region of Valencia in 2006. Most (88.2%) of these interventions were performed as ambulatory surgery. After we excluded areas outside the 5th-95th percentiles, variation among areas was moderate and was similar for men and women. Variation was not associated with the proportion of the distinct surgical settings (admission to a public hospital, outpatient clinic...

‣ Carpal tunnel release surgery: small-area variation and impact of ambulatory surgery in the autonomous region of Valencia, Spain

Rodríguez-Martínez,Pablo; Peiró,Salvador; Librero,Julián; Bernal-Delgado,Enrique; Gisbert-Grifo,Marina; Calabuig-Pérez,Julia; Ridao-López,Manuel; Sanfélix-Gimeno,Gabriel
Fonte: Ediciones Doyma, S.L. Publicador: Ediciones Doyma, S.L.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2013 Português
Relevância na Pesquisa
765.9694%
Objective: This study aimed to analyze variability in rates of carpal tunnel release surgery among the healthcare areas of the autonomous region of Valencia, and to evaluate the contribution of ambulatory surgery and referrals to private hospitals to the variability found. Methods: We carried out a cross-sectional, population-based study, describing the rates of carpal tunnel release surgery, standardized by age and sex, among areas in the region of Valencia in 2006. The observed variation was then analyzed using small-area analysis methods. Data from hospital admissions, referrals to private hospitals, population statistics and hospital resources were used to construct standardized rates, and Spearman's correlation was used to test the association with surgical setting and hospital resources. Results: There were 8.2 carpal tunnel release surgeries per 10,000 inhabitants in the region of Valencia in 2006. Most (88.2%) of these interventions were performed as ambulatory surgery. After we excluded areas outside the 5th-95th percentiles, variation among areas was moderate and was similar for men and women. Variation was not associated with the proportion of the distinct surgical settings (admission to a public hospital, outpatient clinic...