3,408 research outputs found

    TendĂȘncias em sistemas inteligentes de transporte aplicados a ĂŽnibus : anĂĄlise da cidade de Porto Alegre

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    É crescente a demanda por soluçÔes que lidem com o fluxo de viagens nas cidades do sĂ©culo XXI. Como solução, surgem tecnologias que auxiliam no planejamento, controle e operação de sistemas de transporte, chamados Intelligent Transportation Systems. Sabe-se, no entanto, que hĂĄ desafios atrelados Ă  aplicação destas tendĂȘncias, principalmente em paĂ­ses em desenvolvimento. Neste trabalho, coletou-se aplicaçÔes em ITS ao redor do mundo e propostas de novos sistemas na literatura acadĂȘmica. Posteriormente, foram realizadas entrevistas com o ĂłrgĂŁo gestor e a instituição representante das empresas privadas de ĂŽnibus da cidade de Porto Alegre (Brasil). Discutiu-se o cenĂĄrio atual do ITS para ĂŽnibus na cidade, alĂ©m dos entraves e perspectivas para implementação das tendĂȘncias pesquisadas. Conclui-se que ainda sĂŁo necessĂĄrios investimentos em sistemas de base que possibilitem a aplicação de conceitos recentes. Ademais, a falta de subsĂ­dios, aliada a uma crise setorial, resultam em escassez de recursos para projetos.The demand for solutions to the traffic problem of the cities of Century XXI is increasing. To solve this, technologies arise to help planning, controlling and operating transportation systems, named Intelligent Transportation Systems. However, there are challenges related to the application of these tendencies, mainly in underdeveloped countries. In this article, ITS cases around the world were collected, as well as innovative proposals coming from academic articles. Posteriorly, the organization responsible for managing the transportation and the entity representing the bus companies in the city of Porto Alegre (Brazil) were interviewed. The scenario of ITS for buses was discussed, besides the hindrances and perspectives to implement the examined cases and tendencies. It’s concluded that investments in introductory systems are still necessary to enable the application of the most recent concepts in ITS. Furthermore, the lack of subsidies together with a sectorial crisis result in scarcity of resources to projects

    The Alleged Necessity of Microfoundations

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    It is often said that models in the microfoundations literature derive macroeconomic results from the theory of individual behavior only. This paper examines two of the assumptions that are usually made in these models: market clearing and rational expectations. In the context of simple models it is shown that only in some special cases these assumptions can be derived from the fundamental notion that individuals behave rationally. Thus, the usual rationale for the microfoundations literature is challenged. The paper concludes with a more modest rationale for the “necessity” of microfoundations

    Evaluation of a standardized test protocol to measure wheelchair-specific anaerobic and aerobic exercise capacity in healthy novices on an instrumented roller ergometer

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    This study aims to evaluate whether a test protocol with standardized and individualized resistance settings leads to valid wheelchair Wingate tests (WAnT) and graded exercise tests (GXT) in healthy novices. Twenty able-bodied individuals (10M/10F, age 23 ± 2 years, body mass 72 ± 11 kg) performed an isometric strength test, sprint test, WAnT and GXT on a wheelchair ergometer. Using a previously developed set of regression equations, individuals' isometric strength outcome was used to estimate the WAnT result (P30est), from which an effective individual WAnT resistance was derived. The subsequently measured WAnT outcome (P30meas) was used to estimate the GXT outcome (POpeakest) and to scale the individual GXT resistance steps. Estimated and measured outcomes were compared. The WAnT protocol was considered valid when maximal velocity did not exceed 3 m·s-1; the GXT protocol was considered valid when test duration was 8-12 min. P30est did not significantly differ from P30meas, while one participant did not have a valid WanT, as maximal velocity exceeded 3 m·s-1. POpeakest was 10% higher than POpeakmeas, and six participants did not reach a valid GXT: five participants had a test duration under 8 min and one participant over 12 min. The isometric strength test can be used to individually scale the WAnT protocol. The WAnT outcome scaled the protocol for the GXT less accurately, resulting in mostly shorter-than-desired test durations. In conclusion, the evaluated standardized and individualized test protocol was valid for the WAnT but less valid for the GXT among a group of novices. Before implementing the standardized individual test protocol on a broader scale, e.g. among paralympic athletes, it should be evaluated among different athletic wheelchair-dependent populations

    Natural Gas Compressibility Factor Measurement and Evaluation for High Pressure High Temperature Gas Reservoirs

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    The Natural gas compressibility factor is an important reservoir fluid property used in reservoir engineering computations either directly or indirectly in material balance calculations, well test analysis, gas reserve estimates, gas flow in lines and in numerical reservoir simulations. Existing gas compressibility factor correlations were derived using measured data at low to moderate pressures(less than 8, 000 psia) and temperatures (less than 212oF), and an extrapolation to High Pressure High temperature (HPHT) is doubtful. The need to understand and predict gas compressibility factor at HPHT has become increasingly important as exploration and production has moved to ever deeper formations where HPHT conditions are to be encountered. This paper presents laboratory measurement of gas compressibility factors at HPHT natural gas systems and the evaluation of some selected gas compressibility factors correlations. Samples of gas mixtures were collected from the high pressure gas reservoirs from the Niger Delta region of Nigeria. Vinci PVT Cell was used to measure the gas compressibility factors for a pressures ranging from 6,000 to 14,000 psia and temperatures at 270oF and 370oF. The new laboratory data was compared to some of the gas compressibility factor correlations/ models used in the petroleum industry. Results showed that majority of the correlations studied overestimated the gas compressibility factor at HPHT. Mean relative and absolute error analysis were done based on the temperature difference; it was found that the total mean relative and absolute errors for the 370o F cases are higher than those for 270oF. Among all the correlations assessed, Hall and Yarborough equation performed better than other existing correlations with a mean absolute error of 3.545 and relative error of -2.668 at 270oF. At 370oF, Beggs and Brills correlation predicted better than other correlations studied with a mean relative error of -4.77 and absolute error of 7.18

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    Rehabilitation:mobility, exercise & sports; a critical position stand on current and future research perspectives

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    Background Human movement, rehabilitation, and allied sciences have embraced their ambitions within the cycle of “RehabMove” congresses over the past 30 years. This combination of disciplines and collaborations in the Netherlands has tried to provide answers to questions in the fields of rehabilitation and adapted sports, while simultaneously generating new questions and challenges. These research questions help us to further deepen our understanding of (impaired) human movement and functioning, with and without supportive technologies, and stress the importance of continued multidisciplinary (inter)national collaboration. Methods This position stand provides answers that were conceived by the authors in a creative process underlining the preparation of the 6th RehabMove Congress. Results The take-home message of the RehabMove2018 Congress is a plea for continued multidisciplinary research in the fields of rehabilitation and adapted sports. This should be aimed at more individualized notions of human functioning, practice, and training, but also of performance, improved supportive technology, and appropriate “human and technology asset management” at both individual and organization levels and over the lifespan. Conclusions With this, we anticipate to support the development of rehabilitation sciences and technology and to stimulate the use of rehabilitation notions in general health care. We also hope to help ensure a stronger embodiment of preventive and lifestyle medicine in rehabilitation practice. Indeed, general health care and rehabilitation practice require a healthy and active lifestyle management and research agenda in the context of primary, secondary, and tertiary prevention. IMPLICATIONS FOR REHABILITATION Continued multidisciplinary (international) collaboration will stimulate the development of rehabilitation and human movement sciences. Notions from “human and technology asset management and ergonomics” are fundamental to rehabilitation practice and research. The rehabilitation concept will further merge into general health care and the quality there-off
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