Hierarchy of structure functions for passive scalars advected by turbulent flows

A hierarchical model is proposed for the joint moments of the passive scalar dissipation and the velocity dissipation in fluid turbulence. This model predicts that the joint probability density function (PDF) of the dissipations is a bivariate log-Poisson. An analytical calculation of the scaling exponents of structure functions of the passive scalar is carried out for this hierarchical model, showing a good agreement with the results of direct numerical simulations and experiments.

Structure, magnetization, and low-temperature spin dynamic behavior of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs

We have fabricated a set of samples of zincblende Mn-rich Mn(Ga)As clusters embedded in GaAs matrices by annealing (Ga,Mn)As films with different nominal Mn content at 650 degrees C. For the samples with Mn content no more than 4.5%, the Curie temperature reaches nearly 360 K. However, when Mn content is higher than 5.4%, the samples exhibit a spin-glass-like behavior. We suggest that these different magnetic properties are caused by the competing result of dipolar and Ruderman-Kittel-Kasuya-Yosida interaction among clusters. The low-temperature spin dynamic behavior, especially the relaxation effect, shows the extreme creeping effect which is reflected by the time constant tau of similar to 10(11) s at 10 K. We explain this phenomenon by the hierarchical model based on the mean-field approach. We also explain the memory effect by the relationship between the correlation function and the susceptibility.

Memory effect in a system of zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs

Zincblende Mn-rich Mn(Ga)As nanoclusters embedded in GaAs matrices are fabricated by in situ postgrowth annealing diluted magnetic semiconductor (Ga,Mn)As films with Mn concentration ranging from 2.6% to 8% at 650 degrees C. Magnetization measurements show that memory effect and slow magnetic relaxation, the typical characteristics of the spin-glass-like phase, occur below the blocking temperature of 45 K in samples with high Mn concentration, while for samples with low Mn concentration, ferromagnetic order remains up to 360 K. The behavior of low-temperature spin dynamics can be explained by the hierarchical model. (c) 2007 American Institute of Physics.

空间关系类别的形成与计算

Spatial categorization and computation were studied systematically and sequentially in the dissertation, in which, category learning paradigm was transferred to spatial domain. Four parts were developed in our study, in which, the former two parts investigated the mechanism of spatial categorization, and the latter two parts explored two applied issues. Spatial category formation was investigated by two aspects in distance and angle respectively in research one. The results showed that subjects can make accurate judgment and rating for corresponding spatial categorical prototypes and boundaries. In the second research, the formation of spatial relationship categorization was examined through two factors of number of categories and different spatial configurations. The results were repeated in this part, and also, different influences of reference of frame were found in the process of spatial categorization. In the third research, the influences of spatial categorization on spatial localization were found, that in subject could make different location judgment with new acquired spatial categories. Spatial position distribution has no effect on spatial localization on the other hand. The result that reference objects have significant influences on applicability of spatial relationship was found in research four. Our Bayesian hierarchical model could be applied in simulation and prediction of perception of “above” spatial relationship. Theoretical significance and applied importance were discussed in detail.

消费者特征对其网络购物态度和行为意向的影响

In recent years, global online shopping grows rapidly, China's growth rate is far greater than the average level of the world. Online shopping as a new type of shopping patterns gradually drew the researcher's attention. There were so many existing researches on the relationship between consumer characteristic and online shopping attitude and intention, but few togethered the different abstract levels of consumer characteristic in one research. In this study, 3M Model was introduced as theory guide of whole research work, the Chinese consumers who knew about the online shopping was the research object, questionnaire survey was used to collect the data, different abstract levels of consumer characteristic were togethered in a hierarchical model, tried to establish a model to explain the relationship between different abstract levels of consumer characteristic and online shopping attitude and intention. In addition, the study also compared the models posed by data from different consumer groups. The results showed that: First, consumers’ openness, need for arousal, assessment of online shopping experience, perceived risk of online shopping would affect their online shopping attitude and online shopping intention. Second, openness, need for arousal indirectly influenced the online shopping intention through the perceived risk of online shopping. Third, the perceived risk of online shopping indirectly influenced the online shopping intention through online shopping attitude. Fourth, assessment of online shopping experience indirectly influenced the online shopping intention through the perceived risk of online shopping and online shopping attitude. Fifth, only online shopping attitude would directly affect online shopping intention. It also worked as a mediator variable in the final model. Sixth, network age, risk propensity did not significantly affect the online shopping attitude and online shopping intention. Seventh, freight fluctuation can affect student more than in-service on online shopping intention.

Towards an Example-Based Image Compression Architecture for Video-Conferencing

This paper consists of two major parts. First, we present the outline of a simple approach to very-low bandwidth video-conferencing system relying on an example-based hierarchical image compression scheme. In particular, we discuss the use of example images as a model, the number of required examples, faces as a class of semi-rigid objects, a hierarchical model based on decomposition into different time-scales, and the decomposition of face images into patches of interest. In the second part, we present several algorithms for image processing and animation as well as experimental evaluations. Among the original contributions of this paper is an automatic algorithm for pose estimation and normalization. We also review and compare different algorithms for finding the nearest neighbors in a database for a new input as well as a generalized algorithm for blending patches of interest in order to synthesize new images. Finally, we outline the possible integration of several algorithms to illustrate a simple model-based video-conference system.

Early determinants of overweight and obesity at 5 years old in preschoolers from inner of Minas Gerais, Brazil

Introduction: Brazil is experiencing a nutritional transition characterized by a reduction in the prevalence of nutritional deficits and an increase in overweight and obesity, not only in adults but also in children and adolescents.Objectives: This study was designed to evaluate the factors associated with overweight and obesity in Brazilian 5-year-old preschoolers.Methods: A cross-sectional study of a cohort of 232 preschoolers born in Diamantina/Minas Gerais, Brazil, was undertaken. the data, including socioeconomic status, anthropometry, diet, previous history of the preschoolers and family history, were collected between July of 2009 and July of 2010. To identify the factors associated with overweight and obesity, a logistic regression and a hierarchical model were undertaken.Results: Overweight and obesity occurred in 17.2% of the preschoolers. After adjusting for mother's obesity, per capita income, protective food intake, weight gain at age 0-4 months and time spent playing, the factors associated with overweight and obesity that reached statistical significance were mother's obesity [OR = 3.12 (95% CI 1.41-6.91), P = 0.01], weight gain of more than 0.85 kg/month in the first four months of life [OR = 2.16 (95% CI 1.01-4.64), P = 0.041 and lower per capita income [OR = 0.32 (95 %CI 0.13-0.79), P = 0.01].Conclusion: the results show that more weight gain during the first four months of life and being born of mothers with obesity increased the odds of overweight/obesity in the preschoolers, while lower per capita income was a protective factor.

Impact of the intrinsic motivation on the academic performance through voluntary assignments: An empirical analysis

The students academic performance is a key aspect for all agents involved in a higher education quality program. However, there is no unanimity on how to measure it. Some professionals choose assessing only cognitive aspects while others lean towards assessing the acquisition of certain skills. The need to train increasingly adapted professionals in order to respond to the companies’ demands and being able to compete internationally in a global labour market requires a kind of training that goes beyond memorizing. Critical and logical thinking are amongst written language skills demanded in the field of Social Sciences. The objective of this study is to empirically demonstrate the impact of voluntary assignments on the academic performance of students. Our hypothesis is that students who complete high quality voluntary assignments are those more motivated and, therefore, those with higher grades. An experiment with students from the "Financial Accounting II" during the academic year of 2012/13 at the Business and Economics School of the UCM was carried out. A series of voluntary assessments involving the preparation of accounting essays were proposed in order to develop skills and competencies as a complement to the lessons included in the curriculum of the subject. At the end of the course, the carrying-out or not of the essay together with its critical, reflective quality and style, were compared. Our findings show a relationship between the voluntarily presented papers of quality and the final grade obtained throughout the course. These results show that the students intrinsic motivation is a key element in their academic performance. On the other hand, the teachers role focuses on being a motivating element through the learning process.

La visión artificial, un nuevo aliado para el análisis de imágenes artísticas

En este estudio se evalúa el rendimiento de los métodos de Bag-of-Visualterms (BOV) para la clasificación automática de imágenes digitales de la base de datos del artista Miquel Planas. Estas imágenes intervienen en la ideación y diseño de su producción escultórica. Constituye un interesante desafío dada la dificultad de la categorización de escenas cuando éstas difieren más por los contenidos semánticos que por los objetos que contienen. Hemos empleado un método de reconocimiento basado en Kernels introducido por Lazebnik, Schmid y Ponce en 2006. Los resultados son prometedores, en promedio, la puntuación del rendimiento es aproximadamente del 70%. Los experimentos sugieren que la categorización automática de imágenes basada en métodos de visión artificial puede proporcionar principios objetivos en la catalogación de imágenes y que los resultados obtenidos pueden ser aplicados en diferentes campos de la creación artística.

Forecasting Death Rates Using Exogenous Determinants

Mortality models used for forecasting are predominantly based on the statistical properties of time series and do not generally incorporate an understanding of the forces driving secular trends. This paper addresses three research questions: Can the factors found in stochastic mortality-forecasting models be associated with real-world trends in health-related variables? Does inclusion of health-related factors in models improve forecasts? Do resulting models give better forecasts than existing stochastic mortality models? We consider whether the space spanned by the latent factor structure in mortality data can be adequately described by developments in gross domestic product, health expenditure and lifestyle-related risk factors using statistical techniques developed in macroeconomics and finance. These covariates are then shown to improve forecasts when incorporated into a Bayesian hierarchical model. Results are comparable or better than benchmark stochastic mortality models.

A new statistical framework for the quantification of covariate associations with species distributions

Identifying processes that shape species geographical ranges is a prerequisite for understanding environmental change. Currently, species distribution modelling methods do not offer credible statistical tests of the relative influence of climate factors and typically ignore other processes (e.g. biotic interactions and dispersal limitation). We use a hierarchical model fitted with Markov Chain Monte Carlo to combine ecologically plausible niche structures using regression splines to describe unimodal but potentially skewed response terms. We apply spatially explicit error terms that account for (and may help identify) missing variables. Using three example distributions of European bird species, we map model results to show sensitivity to change in each covariate. We show that the overall strength of climatic association differs between species and that each species has considerable spatial variation in both the strength of the climatic association and the sensitivity to climate change. Our methods are widely applicable to many species distribution modelling problems and enable accurate assessment of the statistical importance of biotic and abiotic influences on distributions.

Trends in adult body-mass index in 200 countries from 1975 to 2014: a pooled analysis of 1698 population-based measurement studies with 19·2 million participants

Background: Underweight and severe and morbid obesity are associated with highly elevated risks of adverse health outcomes. We estimated trends in mean body-mass index (BMI), which characterises its population distribution, and in the prevalences of a complete set of BMI categories for adults in all countries.

Methods: We analysed, with use of a consistent protocol, population-based studies that had measured height and weight in adults aged 18 years and older. We applied a Bayesian hierarchical model to these data to estimate trends from 1975 to 2014 in mean BMI and in the prevalences of BMI categories (<18·5 kg/m2 [underweight], 18·5 kg/m2 to <20 kg/m2, 20 kg/m2 to <25 kg/m2, 25 kg/m2 to <30 kg/m2, 30 kg/m2 to <35 kg/m2, 35 kg/m2 to <40 kg/m2, ≥40 kg/m2 [morbid obesity]), by sex in 200 countries and territories, organised in 21 regions. We calculated the posterior probability of meeting the target of halting by 2025 the rise in obesity at its 2010 levels, if post-2000 trends continue.
Findings: We used 1698 population-based data sources, with more than 19·2 million adult participants (9·9 million men and 9·3 million women) in 186 of 200 countries for which estimates were made. Global age-standardised mean BMI increased from 21·7 kg/m2 (95% credible interval 21·3–22·1) in 1975 to 24·2 kg/m2 (24·0–24·4) in 2014 in men, and from 22·1 kg/m2 (21·7–22·5) in 1975 to 24·4 kg/m2 (24·2–24·6) in 2014 in women. Regional mean BMIs in 2014 for men ranged from 21·4 kg/m2 in central Africa and south Asia to 29·2 kg/m2 (28·6–29·8) in Polynesia and Micronesia; for women the range was from 21·8 kg/m2 (21·4–22·3) in south Asia to 32·2 kg/m2 (31·5–32·8) in Polynesia and Micronesia. Over these four decades, age-standardised global prevalence of underweight decreased from 13·8% (10·5–17·4) to 8·8% (7·4–10·3) in men and from 14·6% (11·6–17·9) to 9·7% (8·3–11·1) in women. South Asia had the highest prevalence of underweight in 2014, 23·4% (17·8–29·2) in men and 24·0% (18·9–29·3) in women. Age-standardised prevalence of obesity increased from 3·2% (2·4–4·1) in 1975 to 10·8% (9·7–12·0) in 2014 in men, and from 6·4% (5·1–7·8) to 14·9% (13·6–16·1) in women. 2·3% (2·0–2·7) of the world's men and 5·0% (4·4–5·6) of women were severely obese (ie, have BMI ≥35 kg/m2). Globally, prevalence of morbid obesity was 0·64% (0·46–0·86) in men and 1·6% (1·3–1·9) in women.

Interpretation: If post-2000 trends continue, the probability of meeting the global obesity target is virtually zero. Rather, if these trends continue, by 2025, global obesity prevalence will reach 18% in men and surpass 21% in women; severe obesity will surpass 6% in men and 9% in women. Nonetheless, underweight remains prevalent in the world's poorest regions, especially in south Asia.

Modelling HIV/AIDS length of stay in Portugal

Tese apresentada como requisito parcial para obtenção do grau de Doutor em Estatística e Gestão de Informação pelo Instituto Superior de Estatística e Gestão de Informação da Universidade Nova de Lisboa

Worldwide trends in diabetes since 1980: a pooled analysis of 751 population-based studies with 4.4 million participants.

One of the global targets for non-communicable diseases is to halt, by 2025, the rise in the age-standardised adult prevalence of diabetes at its 2010 levels. We aimed to estimate worldwide trends in diabetes, how likely it is for countries to achieve the global target, and how changes in prevalence, together with population growth and ageing, are affecting the number of adults with diabetes. We pooled data from population-based studies that had collected data on diabetes through measurement of its biomarkers. We used a Bayesian hierarchical model to estimate trends in diabetes prevalence-defined as fasting plasma glucose of 7.0 mmol/L or higher, or history of diagnosis with diabetes, or use of insulin or oral hypoglycaemic drugs-in 200 countries and territories in 21 regions, by sex and from 1980 to 2014. We also calculated the posterior probability of meeting the global diabetes target if post-2000 trends continue. We used data from 751 studies including 4,372,000 adults from 146 of the 200 countries we make estimates for. Global age-standardised diabetes prevalence increased from 4.3% (95% credible interval 2.4-7.0) in 1980 to 9.0% (7.2-11.1) in 2014 in men, and from 5.0% (2.9-7.9) to 7.9% (6.4-9.7) in women. The number of adults with diabetes in the world increased from 108 million in 1980 to 422 million in 2014 (28.5% due to the rise in prevalence, 39.7% due to population growth and ageing, and 31.8% due to interaction of these two factors). Age-standardised adult diabetes prevalence in 2014 was lowest in northwestern Europe, and highest in Polynesia and Micronesia, at nearly 25%, followed by Melanesia and the Middle East and north Africa. Between 1980 and 2014 there was little change in age-standardised diabetes prevalence in adult women in continental western Europe, although crude prevalence rose because of ageing of the population. By contrast, age-standardised adult prevalence rose by 15 percentage points in men and women in Polynesia and Micronesia. In 2014, American Samoa had the highest national prevalence of diabetes (>30% in both sexes), with age-standardised adult prevalence also higher than 25% in some other islands in Polynesia and Micronesia. If post-2000 trends continue, the probability of meeting the global target of halting the rise in the prevalence of diabetes by 2025 at the 2010 level worldwide is lower than 1% for men and is 1% for women. Only nine countries for men and 29 countries for women, mostly in western Europe, have a 50% or higher probability of meeting the global target. Since 1980, age-standardised diabetes prevalence in adults has increased, or at best remained unchanged, in every country. Together with population growth and ageing, this rise has led to a near quadrupling of the number of adults with diabetes worldwide. The burden of diabetes, both in terms of prevalence and number of adults affected, has increased faster in low-income and middle-income countries than in high-income countries. Wellcome Trust.

What's the difference under the gown? : new professors' development as university teachers

This study explores how new university teachers develop a teaching identity. Despite the significance ofteaching, which usually comprises 40% of a Canadian academic's workload, few new professors have any formal preparation for that aspect of their role. Discipline-specific education for postsecondary professors is a well-defined path; graduates applying for faculty positions will have the terminal degree to attest to their knowledge and skill conducting research in the discipline. While teaching is usually given the same workload balance as research, it is not clear how professors create themselves as teaching professionals. Drawing on Kelly's (1955) personal construct theory and Kegan's (1982, 1994) model ofdevelopmental constructivism through differentiation and integration, this study used a phenomenographic framework~(Marton, 1986, 1994; Trigwell & Prosser, 1996) to investigate the question of how new faculty members construe their identity as university teachers. Further, my own role development as researcher was used as an additional lens through which to view the study results. The study focused particularly on the challenges and supports to teaching role development and outlines recommendations the participants made for supporting other newcomers. In addition, the variations and similarities in the results suggest a developmental model to conceptions ofteaching roles, one in which teaching, research, and service roles are viewed as more integrated over time. Developing a teacher identity was seen as a progression on a hierarchical model similar to Maslow's (1968) hierarchy of needs.