An analytical solver for the multi-group two-dimensional neutron-diffusion equation by integral transform techniques

In this work, we present an analytical solver for neutron diffusion in a rectangular two-dimensional geometry by a two-step integral transform procedure. To this end, we consider a regionwise homogeneous problem for two energy groups, i.e. fast and thermal neutrons, respectively. Each region has its specific physical properties, specified by cross-sections and diffusion constants. The problem is set up by two coupled bi-dimensional diffusion equations in agreement with general perturbation theory. These are solved by integral transforms Laplace transform and generalized integral transform technique yielding analytical expressions for the scalar neutron fluxes. The solutions for neutron fluxes are presented for fast and thermal neutrons in the four regions

Modelo euleriano semi-analítico para a dispersão de contaminantes na Camada Limite Planetária

An analytical air quality dispersion model based on a discretization of the planetary boundary layer in N sub-layers is presented. In each sub-layer the diffusion-advection equation is solved by the Laplace Transform techniques, considering an average value for the vertical exchange coefficient and the wind speed. As a consequence, the present approach allows to employ realistic semi-empirical profiles for the eddy diffusivity and wind speed, in such manner that the inhomogeneous turbulence can be handle. The model performance have been evaluated using the well-known Copenhagen and Prairie Grass datasets. Then, the application of the statistical evalution procedure (Hanna, 1989) over the out coming results has show that the proposed analytical dispersion model produces a good fitting of the observational data.Um modelo de dispersão analítico baseado na discretização da Camada Limite Planetária em N subcamadas é apresentado. Em cada subcamada a equação de difusão-adevcção é resolvida pelo emprego da transformada de Laplace, considerando um valor médio para o coeficiente de difusão e para a velocidade do vento. O presente modelo emprega perfis realísticos semi-empíricos para o coeficiente de difusão e velocidade do vento, de modo que a turbulência não homogênea pode ser utilizada. A performance do modelo é testada confrontando as simulações com os dados experimentais de Prairie Grass e Copenhagen. A aplicação de índices estatísticos (Hanna, 1989) mostra que o modelo analítico de dispersão proposto produz bons resultados

Ferramentas para a caracterização de painéis fotovoltaicos

Neste trabajo apresentamos procedimientos y herramientas para la caracterización completa de paneles fotovoltaicos. Como punto de partida, fueron obtenidas las curvas caracteristicas provenidas por el fabricante. En un segundo momento fueron hechas coletas manuales de dados para la confección de las curvas caracteristicas. A partir de las propriedades fisicas de semiconductores el modelamento del panel fue establecido. El procedimiento establecido és muy fatigoso y reiterativo, podendo llevar a imprecisiones. Para la automatización deste procedimiento, lo siguiente sistema fue proyectado y montado: un conversor dc/dc permite realizar el control electronico de carga resistiva; un computadora realiza el control cíclico de la variación de carga del panel. Un sistema de aquisición de dados permite la obtención de los parámetros en el panel. A partir desta coleta de dados automatizada un software constroe las curvas caracteristicas.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Relationships between Parental Education and Overweight with Childhood Overweight and Physical Activity in 9-11 Year Old Children: Results from a 12-Country Study

Background: Globally, the high prevalence of overweight and low levels of physical activity among children has serious implications for morbidity and premature mortality in adulthood. Various parental factors are associated with childhood overweight and physical activity. The objective of this paper was to investigate relationships between parental education or overweight, and (i) child overweight, (ii) child physical activity, and (iii) explore household coexistence of overweight, in a large international sample. Methods: Data were collected from 4752 children (9-11 years) as part of the International Study of Childhood Obesity, Lifestyle and the Environment in 12 countries around the world. Physical activity of participating children was assessed by accelerometry, and body weight directly measured. Questionnaires were used to collect parents' education level, weight, and height. Results: Maternal and paternal overweight were positively associated with child overweight. Higher household coexistence of parent-child overweight was observed among overweight children compared to the total sample. There was a positive relationship between maternal education and child overweight in Colombia 1.90 (1.23-2.94) [odds ratio (confidence interval)] and Kenya 4.80 (2.21-10.43), and a negative relationship between paternal education and child overweight in Brazil 0.55 (0.33-0.92) and the USA 0.54 (0.33-0.88). Maternal education was negatively associated with children meeting physical activity guidelines in Colombia 0.53 (0.33-0.85), Kenya 0.35 (0.19-0.63), and Portugal 0.54 (0.31-0.96). Conclusions: Results are aligned with previous studies showing positive associations between parental and child overweight in all countries, and positive relationships between parental education and child overweight or negative associations between parental education and child physical activity in lower economic status countries. Relationships between maternal and paternal education and child weight status and physical activity appear to be related to the developmental stage of different countries. Given these varied relationships, it is crucial to further explore familial factors when investigating child overweight and physical activity

Taenia solium Infections in a Rural Area of Eastern Zambia-A Community Based Study

Taenia solium taeniosis/cysticercosis is a zoonotic infection endemic in many developing countries, with humans as the definitive host (taeniosis) and pigs and humans as the intermediate hosts (cysticercosis). When humans act as the intermediate host, the result can be neurocysticercosis, which is associated with acquired epilepsy, considerable morbidity and even mortality. In Africa, most studies have been carried out in pigs with little or no data in humans available. In this human study, conducted in a rural community in Eastern Zambia, prevalences for taeniosis and cysticercosis were determined at 6.3% and 5.8% respectively, indicating the hyperendemicity of the area. Cysticercosis infection was strongly related with age, with a significant increase in prevalence occurring in individuals from the age of 30 onward. A collected tapeworm was confirmed to be T. solium. Risk factors associated with the transmission and maintenance of the parasite such as free roaming pigs, households without latrines, backyard slaughter of pigs without inspection and consumption of undercooked pork were also present. The findings of this work have identified the need for further research in the transmission dynamics and the burden that this infection has on the resources of poor local people