968 resultados para Riemann sum


Relevância:

10.00% 10.00%

Publicador:

Resumo:

The U.S. Fish Commission was initiated in 1871 with Spencer Fullerton Baird as the first U.S. Fish Commissioner as an independent entity. In 1903 it became a part of the new U.S. Department of Commerce and Labor and was renamed the Bureau of Fisheries, a name it retained when the Departments of Commerce and Labor were separated in 1912. The Bureau remained in the Commerce Department until 1941 when it was merged with the Biological Survey and placed in the Department of Interior as the U.S. Fish and Wildlife Service. It was a scientific agency with well conceived programs of action, and it provided knowledge, advice, and example to state governments and individuals with fisheries interests and needs. Its efforts were supported by timely international agreements which constituted the precedent for Federal interest in fishery matters. The Fisheries Service earned stature as an advisor through heavy emphasis on basic biological research. The lack of such knowledge was marked and universal in the 1870’s, but toward the end of that decade, strong steps had been taken to address those needs under Baird’s leadership. USFC research activities were conducted cooperatively with other prominent scientists in the United States and abroad. Biological stations were established, and the world’s first and most productive deepsea research vessel, the Albatross, was constructed, and its 40-year career gave a strong stimulus to the science of oceanography. Together, the agency’s scientists and facilities made important additions to the sum of human knowledge, derived principles of conservation which were the vital bases for effective regulatory legislation, conducted extensive fish cultural work, collected and disseminated fisheries statistics, and began important research in methods of fish harvesting, preservation, transportation, and marketing.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Neste trabalho calculamos os fatores de forma e constantes de acoplamento para os vértices B*sBK, B*BsK e BsBK* usando as Regras de Soma da Cromodinâmica Quântica (QCD). Ainda estão incluídos os diagramas não perturbativos. Nós usamos a técnica de considerar dois mésons fora da camada de massa para obter dois fatores de forma diferentes a fim de diminuir as incertezas. Os cálculos das incertezas foram incluídos neste trabalho.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The worldwide literature on management of spotted seals, Phoca largha, was reviewed and updated, and aerial surveys weref lown in 1992 and 1993 to determine the species' distribution and abundance in U.S. waters. In April, spotted seals were found only in the Bering Sea ice front. In June, they were seen along deteriorating ice floes and fast ice in Norton Sound. Surveys along most of Alaska's western coast in August and September found over 2,500 spotted seals in Kuskokwim Bay and concentrations of 100-400 seals around Nunivak Island, Scammon Bay, Golovnin Bay/Norton Sound, Cape Espenberg/Kotzebue Sound, and Kasegaluk Lagoon. All of these sites have been used by spotted seals in the past. The sum of the highest counts, irrespective of year, was 3,570 seals (CV =0.06). This is not an abundance estimate for all spotted seals in the Bering Sea, because it does not account for animals in the water, and we did not survey the Asian coast and some islands. Also, spotted seals and harbor seals, Phoca vitulina, are too similar in appearance to be identified accurately from the air, so our results probably include a mix of these species where their ranges overlap.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Esse texto trata do problema de um fluido contaminado escoando por um meio poroso, tratando os componentes na mistura como meios contínuos. Na primeira parte, desenvolvemos a teoria de misturas de meios contínuos e discutimos equações da continuidade, momento linear e momento angular. A seguir, descrevemos o problema em detalhe e fazemos hipóteses para simplificar o escoamento. Aplicamos as equações encontradas anteriormente para encontrarmos um sistema de equações diferenciais parciais. Desse ponto em diante, o problema se torna quase puramente matemático. Discutimos o caso insaturado, e depois a saturação do meio poroso. Finalmente, adicionamos um contaminante à mistura e, em seguida, N contaminantes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Energy is a key input into the fish harvesting process. Efficient use of energy helps in reducing operational costs and environmental impact, while increasing profits. Energy optimisation is an important aspect of responsible fishing as enunciated in the Code of Conduct for Responsible Fisheries. Gross Energy Requirement (GER) is the sum of all non-renewable energy resources consumed in making available a product or service and is expressed in energy units per physical unit of product or service delivered. GER is a measure of intensity of non-renewable resource use and it reflects the amount of depletion of earth’s inherited store of non-renewable energy in order to create and make available a product or service. In this study, GER in fish harvesting up to the point of landing is estimated in selected fish harvesting systems in the small-mechanised sectors of Indian fisheries and compared with reported results from selected non mechanised and motorised fishing systems to reflect the situation during 1997-1998. Among the fish harvesting systems studied, GER t fish-1 ranged from 5.54 and 5.91 GJ, respectively, for wooden and steel purse seiners powered by 156 hp engines; 6.40 GJ for wooden purse seiner with 235 hp engine; 25.18 GJ for mechanised gillnet/line fishing vessel with 89 hp engines; to 31.40 and 36.97 GJ, respectively, for wooden and steel trawlers powered by 99-106 hp engines.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A presente dissertação tem o objetivo de mostrar a arte Origami sob um contexto matemático, apresentando um pequeno resumo dos aspectos história e o desenvolvimento do Origami ao longo do tempo e dando maior destaque às suas aplicações na matemática, com o emprego dos axiomas de Huzita e a proposta de ampliação deste conjunto de axiomas com a inclusão da circunferência no papel Origami. Com o uso das técnicas de dobraduras, este trabalho mostra várias aplicações do Origami na matemática, tais como: a solução de alguns problemas clássicos, a construção de polígonos, a demonstração da soma dos ângulos internos de um triângulo, cálculo de algumas áreas, a solução de alguns problemas de máximos e mínimos, seguidos dos conceitos matemático envolvidos em cada um deles. E a inclusão da circunferência no plano Origami permitiu ainda, o estudo das construções das cônicas por dobraduras

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A presente dissertação tem o objetivo de mostrar a arte Origami sob um contexto matemático, apresentando um pequeno resumo dos aspectos história e o desenvolvimento do Origami ao longo do tempo e dando maior destaque às suas aplicações na matemática, com o emprego dos axiomas de Huzita e a proposta de ampliação deste conjunto de axiomas com a inclusão da circunferência no papel Origami. Com o uso das técnicas de dobraduras, este trabalho mostra várias aplicações do Origami na matemática, tais como: a solução de alguns problemas clássicos, a construção de polígonos, a demonstração da soma dos ângulos internos de um triângulo, cálculo de algumas áreas, a solução de alguns problemas de máximos e mínimos, seguidos dos conceitos matemático envolvidos em cada um deles. E a inclusão da circunferência no plano Origami permitiu ainda, o estudo das construções das cônicas por dobraduras.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Sabe-se que um estilo de vida sedentário e uma condição aeróbica baixa são associados com uma maior chance de desenvolvimento de doenças cardiovasculares e um maior risco de mortalidade por todas as causas. Contudo, é possível que outros indicadores de aptidão física possam ter significado clínico prognóstico. Originalmente proposto em 1999, o teste de sentar-levantar (TSL) é, simples de executar e possui comprovada reprodutibilidade inter e intra-avaliador. O avaliado inicia o teste com o escore máximo de 5 pontos para cada uma das ações de sentar e levantar, sendo subtraído do mesmo, um ponto para cada apoio extra utilizado (mão, braço e joelho) e meio ponto para cada desequilíbrio corporal perceptível. A pontuação do TSL escore, variando de 0 a 10, é realizada pela soma das ações de sentar e levantar. Considerando o potencial papel da flexibilidade para uma execução mais eficiente de gestos motores, não é surpreendente que o desempenho sobre TSL possa ser influenciado por essa valência. O objetivo desta dissertação foi analisar a relação entre o resultado do TSL e a mortalidade por todas as causas e a flexibilidade. No primeiro estudo, 2002 indivíduos entre 51 e 80 anos (68% homens), realizaram o TSL e os resultados foram estratificados em quatro faixas: 0/3; 3,5/5,5, 6/7,5 and 8/10. Baixos resultados no TSL escore foram associados com um maior risco de mortalidade (p<0,001). Uma tendência contínua de maior sobrevivência se refletiu no ajuste multivariado idade, sexo, índice de massa corporal em um razão de risco de 5,44 [95%IC=3,19,5], 3,44 [95%IC=2,05,9] e 1,84 [95%IC=1,13,0] (p<0,001) dos menores para as maiores faixas de resultados do TSL. Cada aumento de um ponto no escore do TSL significou uma melhora de 21% na sobrevivência. Já o segundo estudo, contou com 3927 indivíduos (67,4% homens) que realizaram o TSL e o Flexiteste. O Flexiteste avalia a amplitude máxima passiva de 20 movimentos corporais. Para cada um dos movimentos, existem cinco escores possíveis, 0 a 4 em uma ordem de mobilidade crescente. A soma dos resultados dos 20 movimentos fornece uma pontuação de flexibilidade global denominada de Flexíndice (FLX). Os resultados do FLX foram estratificados em quartis (626, 2735, 3644 and 4577). Os valores do TSL em cada quartil diferiram entre si (p<0,001). Além disso, o escore do TSL e o FLX foram diretamente associados (r=0,296; p<0,001). Os indivíduos com um TSL escore zero são menos flexíveis para todos os 20 movimentos do Flexiteste do que aqueles com escore 10. Portanto, os dados da presente dissertação, indicam que: o resultado do TSL se mostrou um importante preditor de mortalidade por todas as causas para indivíduos entre 51-80 anos de idade e que indivíduos mais flexíveis tendem a ter maiores escores no TSL.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A teoria magneto-hidrodinâmicos permite a estruturação de modelos computacionais, designados modelos MHDs, que são uma extensão da dinâmica dos fluidos para lidar com fluidos eletricamente carregados, tais como os plasmas, em que se precisa considerar os efeitos de forças eletromagnéticas. Tais modelos são especialmente úteis quando o movimento exato de uma partícula não é de interesse, sendo que as equações descrevem as evoluções de quantidades macroscópicas. Várias formas de modelos MHD têm sido amplamente utilizadas na Física Espacial para descrever muitos tipos diferentes de fenômenos de plasma, tais como reconexão magnética e interações de ventos estelares com diferentes objetos celestiais. Neste trabalho, o objetivo é analisar o comportamento de diversos fluxos numéricos em uma discretização de volumes finitos de um modelo numérico de MHD usando um esquema de malha entrelaçada sem separação direcional considerando alguns casos testes. Para as simulações, utiliza-se o código Flash, desenvolvido pela Universidade de Chicago, por ser um código de amplo interesse nas simulações astrofísicas e de fenômenos no espaço próximo à Terra. A metodologia consiste na inclusão de um fluxo numérico, permitindo melhoria com respeito ao esquema HLL.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Our ability to skillfully manipulate an object often involves the motor system learning to compensate for the dynamics of the object. When the two arms learn to manipulate a single object they can act cooperatively, whereas when they manipulate separate objects they control each object independently. We examined how learning transfers between these two bimanual contexts by applying force fields to the arms. In a coupled context, a single dynamic is shared between the arms, and in an uncoupled context separate dynamics are experienced independently by each arm. In a composition experiment, we found that when subjects had learned uncoupled force fields they were able to transfer to a coupled field that was the sum of the two fields. However, the contribution of each arm repartitioned over time so that, when they returned to the uncoupled fields, the error initially increased but rapidly reverted to the previous level. In a decomposition experiment, after subjects learned a coupled field, their error increased when exposed to uncoupled fields that were orthogonal components of the coupled field. However, when the coupled field was reintroduced, subjects rapidly readapted. These results suggest that the representations of dynamics for uncoupled and coupled contexts are partially independent. We found additional support for this hypothesis by showing significant learning of opposing curl fields when the context, coupled versus uncoupled, was alternated with the curl field direction. These results suggest that the motor system is able to use partially separate representations for dynamics of the two arms acting on a single object and two arms acting on separate objects.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Over the past one hundred and fifty years, the landscape and ecosystems of the Pacific Northwest coastal region, already subject to many variable natural forces, have been profoundly affected by human activities. In virtually every coastal watershed from the Strait of Juan de Fuca to Cape Mendocino, settlement, exploitation and development of resou?-ces have altered natural ecosystems. Vast, complex forests that once covered the region have been largely replaced by tree plantations or converted to non-forest conditions. Narrow coastal valleys, once filled with wetlands and braided streams that tempered storm runoff and provided salmon habitat, were drained, filled, or have otherwise been altered to create land for agriculture and other uses. Tideflats and saltmarshes in both large and small estuaries were filled for industrial, commercial, and other urban uses. Many estuaries, including that of the Columbia River, have been channeled, deepened, and jettied to provide for safe, reliable navigation. The prodigious rainfall in the region, once buffered by dense vegetation and complex river and stream habitat, now surges down sirfiplified stream channels laden with increased burdens of sediment and debris. Although these and many other changes have occurred incrementally over time and in widely separated areas, their sum can now be seen to have significantly affected the natural productivity of the region and, as a consequence, changed the economic structure of its human communities. This activity has taken place in a region already shaped by many interacting and dynamic natural forces. Large-scale ocean circulation patterns, which vary over long time periods, determine the strength and location of currents along the coast, and thus affect conditions in the nearshore ocean and estuaries throughout the region. Periodic seasonal differences in the weather and ocean act on shorter time scales; winters are typically wet with storms from the southwest while summers tend to be dry with winds from the northwest. Some phenomena are episodic, such as El Nifio events, which alter weather, marine habitats, and the distribution and survival of marine organisms. Other oceanic and atmospheric changes operate more slowly; over time scales of decades, centuries, and longer. Episodic geologic events also punctuate the region, such as volcanic eruptions that discharge widespread blankets of ash, frequent minor earthquakes, and major subduction zone earthquakes each 300 to 500 years that release accumulated tectonic strain, dropping stretches of ocean shoreline, inundating estuaries and coastal valleys, and triggering landslides that reshape stream profiles. While these many natural processes have altered, sometimes dramatically, the Pacific Northwest coastal region, these same processes have formed productive marine and coastal ecosystems, and many of the species in these systems have adapted to the variable environmental conditions of the region to ensure their long-term survival.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Longitudinal surveys of anglers or boat owners are widely used in recreational fishery management to estimate total catch over a fishing season. Survey designs with repeated measures of the same random sample over time are effective if the goal is to show statistically significant differences among point estimates for successive time intervals. However, estimators for total catch over the season that are based on longitudinal sampling will be less precise than stratified estimators based on successive independent samples. Conventional stratified variance estimators would be negatively biased if applied to such data because the samples for different time strata are not independent. We formulated new general estimators for catch rate, total catch, and respective variances that sum across time strata but also account for correlation stratum samples. A case study of the Japanese recreational fishery for ayu (Plecoglossus altivelis) showed that the conventional stratified variance estimate of total catch was about 10% of the variance estimated by our new method. Combining the catch data for each angler or boat owners throughout the season reduced the variance of the total catch estimate by about 75%. For successive independent surveys based on random independent samples, catch, and variance estimators derived from combined data would be the same as conventional stratified estimators when sample allocation is proportional to strata size. We are the first to report annual catch estimates for ayu in a Japanese river by formulating modified estimators for day-permit anglers.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Biochemical composition of the muscle of juveniles belonging to 18 different species of freshwater fishes showed that the protein percentage in juveniles was higher than the adults. The fat, on the other hand, was much lower. This suggests that the body fat increases with the onset of maturity. No clear inverse relationship was found between fat and protein in juveniles. Moisture percentage was very high in juveniles. This was probably because of low fat content. In most species the sum of fat and water contents (F + W) was found to be constant. The percentages of ash, calcium and phosphorus were higher in juveniles than those of adults. Dry matter percentage varied inversely with the moisture and in most species carbohydrate was generally low. In juveniles although the calorific value of protein-fraction was high the total calorific value was lower than the adults.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The fishing industry on Lake Victoria continued to provide a wide spectrum of activities to a variety of people principally the fishermen and the fish mongers, boat builders,fishnets and associated equipment manufacturer transporters on land and water and finally the consumers of the end product the fish. Though there were such varied activities in the industry the year under review, as in previous other recent years, was difficult one being, characterized by continued shortages of fishing gear and accessories, spare parts for the outboard engines, timber for boat building, nails, paints and generally high prices of those items when ever found. Thus this total sum the activities of the fishing industry on Lake victoria was rather slack as compared to those of precious year.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Numerical techniques for non-equilibrium condensing flows are presented. Conservation equations for homogeneous gas-liquid two-phase compressible flows are solved by using a finite volume method based on an approximate Riemann solver. The phase change consists of the homogeneous nucleation and growth of existing droplets. Nucleation is computed with the classical Volmer-Frenkel model, corrected for the influence of the droplet temperature being higher than the steam temperature due to latent heat release. For droplet growth, two types of heat transfer model between droplets and the surrounding steam are used: a free molecular flow model and a semi-empirical two-layer model which is deemed to be valid over a wide range of Knudsen number. The computed pressure distribution and Sauter mean droplet diameters in a convergent-divergent (Laval) nozzle are compared with experimental data. Both droplet growth models capture qualitatively the pressure increases due to sudden heat release by the non-equilibrium condensation. However the agreement between computed and experimental pressure distributions is better for the two-layer model. The droplet diameter calculated by this model also agrees well with the experimental value, whereas that predicted by the free molecular model is too small. Condensing flows in a steam turbine cascade are calculated at different Mach numbers and inlet superheat conditions and are compared with experiments. Static pressure traverses downstream from the blade and pressure distributions on the blade surface agree well with experimental results in all cases. Once again, droplet diameters computed with the two-layer model give best agreement with the experiments. Droplet sizes are found to vary across the blade pitch due to the significant variation in expansion rate. Flow patterns including oblique shock waves and condensation-induced pressure increases are also presented and are similar to those shown in the experimental Schlieren photographs. Finally, calculations are presented for periodically unsteady condensing flows in a low expansion rate, convergent-divergent (Laval) nozzle. Depending on the inlet stagnation subcooling, two types of self-excited oscillations appear: a symmetric mode at lower inlet subcooling and an asymmetric mode at higher subcooling. Plots of oscillation frequency versus inlet sub-cooling exhibit a hysteresis loop, in accord with observations made by other researchers for moist air flow. Copyright © 2006 by ASME.