63 resultados para drawbacks

em Repositório Institucional UNESP - Universidade Estadual Paulista "Julio de Mesquita Filho"


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The development of robots has shown itself as a very complex interdisciplinary research field. The predominant procedure for these developments in the last decades is based on the assumption that each robot is a fully personalized project, with the direct embedding of hardware and software technologies in robot parts with no level of abstraction. Although this methodology has brought countless benefits to the robotics research, on the other hand, it has imposed major drawbacks: (i) the difficulty to reuse hardware and software parts in new robots or new versions; (ii) the difficulty to compare performance of different robots parts; and (iii) the difficulty to adapt development needs-in hardware and software levels-to local groups expertise. Large advances might be reached, for example, if physical parts of a robot could be reused in a different robot constructed with other technologies by other researcher or group. This paper proposes a framework for robots, TORP (The Open Robot Project), that aims to put forward a standardization in all dimensions (electrical, mechanical and computational) of a robot shared development model. This architecture is based on the dissociation between the robot and its parts, and between the robot parts and their technologies. In this paper, the first specification for a TORP family and the first humanoid robot constructed following the TORP specification set are presented, as well as the advances proposed for their improvement.

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A produção de mudas de caramboleira é um dos fatores limitantes à expansão comercial da cultura, devido ao tempo que estas levam para serem formadas e iniciarem a produção. Uma boa alternativa pode estar na otimização dos métodos de propagação vegetativa, através de estudos relativos aos processos e fatores envolvidos no enraizamento de estacas. Este trabalho foi desenvolvido com o objetivo de estudar o enraizamento de estacas apicais e basais de caramboleira, tratadas com ácido indolbutírico (IBA), em condições de nebulização intermitente. Estacas apicais e basais de caramboleira foram coletadas de ramos de plantas-matrizes da cultivar B-10 e submetidas à aplicação de cinco concentrações de IBA (0; 1.000; 3.000; 5.000 e 7000 mg.L-1), em imersão por 10 segundos, para avaliar a capacidade de sobrevivência, enraizamento e número médio de raízes/estaca. Posteriormente, as estacas foram colocadas em caixas de madeira contendo vermiculita média como substrato e mantidas em casa de vegetação, sob nebulização intermitente, durante 70 dias. O delineamento experimental utilizado foi em esquema fatorial 2 x 5, com 4 repetições e 10 estacas/parcela. As estacas apicais obtiveram melhores resultados para porcentagem de sobrevivência (49,26%), enraizamento (34,84%) e número médio de raízes (20,51), mostrando-se superiores às basais. O uso de IBA não influenciou em nenhuma das variáveis analisadas.

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One of the main drawbacks of the GPS accuracy for L1 users is the error due to ionosphere. This error depends on the total electron content presents in the ionosphere, as well as of the carrier frequency. Some models have been developed to correct GPS observables of the systematic error due to the ionosphere. The model more known and used is the Klobuchar model, which corrected 50-60% of the ionospheric error approximately. Alternatively, IGS (International GNSS Service) also has developed a model called Global Ionospheric Map (GIM). These maps, in format IONEX, are available in the site of the IGS, and one of the applications of them is to correct the GPS observables of the error due to ionosphere. This work aims at evaluating the quality of GPS point positioning using the IGS ionospheric model in the southerm region of Brazil. Tests carried out had shown an average improvement in the horizontal and vertical determination of 44% and 77%, respectively, when GIM is used in the point positioning.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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In this article, we propose new control charts for monitoring the mean vector and the covariance matrix of bivariate processes. The traditional tools used for this purpose are the T (2) and the |S| charts. However, these charts have two drawbacks: (1) the T (2) and the |S| statistics are not easy to compute, and (2) after a signal, they do not distinguish the variable affected by the assignable cause. As an alternative to (1), we propose the MVMAX chart, which only requires the computation of sample means and sample variances. As an alternative to (2), we propose the joint use of two charts based on the non-central chi-square statistic (NCS statistic), named as the NCS charts. Once the NCS charts signal, the user can immediately identify the out-of-control variable. In general, the synthetic MVMAX chart is faster than the NCS charts and the joint T (2) and |S| charts in signaling processes disturbances.

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Energy policies and technological progress in the development of wind turbines have made wind power the fastest growing renewable power source worldwide. The inherent variability of this resource requires special attention when analyzing the impacts of high penetration on the distribution network. A time-series steady-state analysis is proposed that assesses technical issues such as energy export, losses, and short-circuit levels. A multiobjective programming approach based on the nondominated sorting genetic algorithm (NSGA) is applied in order to find configurations that maximize the integration of distributed wind power generation (DWPG) while satisfying voltage and thermal limits. The approach has been applied to a medium voltage distribution network considering hourly demand and wind profiles for part of the U.K. The Pareto optimal solutions obtained highlight the drawbacks of using a single demand and generation scenario, and indicate the importance of appropriate substation voltage settings for maximizing the connection of MPG.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Some patients with obsessive-compulsive disorder (OCD) exhibit an unsatisfactory reduction in symptom severity despite being treated with all the available therapeutic alternatives. The clinical variables associated with treatment-refractoriness in OCD are inconsistently described in the literature.Methods: To investigate factors associated with treatment-reftactoriness of patients with OCD, we conducted a case-control study, comparing 23 patients with treatment-refractory OCD to 26 patients with treatment-responding OCD.Results: the factors associated with refractoriness of OCD were higher severity of symptoms since the onset of OCD (P < 0.001), chronic course (p=0.003), lack of a partner (p=0.037), unemployment (p=0.025), low economic status (p=0.015), presence of obsessive-compulsive symptoms of sexual/religious content (p=0.043), and higher scores on family accommodation (P < 0.001). Only the three latter variables remained significantly associated with treatment-reftactoriness after regression analyses. Limitations: small sample size, the biases and drawbacks inherent to a case-control study, and the inclusion criteria used to define the study groups may have limited the generalisation of the results.Conclusion: A major strength of this study is the systematic and structured evaluation of a vast array of variables related to the clinical expression of OCD, including epigenetic factors and ratings derived from instruments evaluating family accommodation. The presence of sexual/religious symptoms, low economic status and high modification on family function due to OCD were independently associated with, treatment-refractoriness. Future longitudinal studies are warranted to verify if these variables represent predictive factors of treatment non-response. (c) 2006 Elsevier B.V. All rights reserved.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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We review the information currently available on the reproduction of the Amphisbaenia and provide original data on the reproductive biology of four Neotropical species: Amphisbaena alba; A. mertensi; Cercolophia roberti, and Leposternon infraorbitale. In total, we compiled data for 22 species: 17 Amphisbaenidae, 1 Rhineuridae, 3 Bipedidae, and 1 Trogonophidae. The majority of the species were oviparous with the exceptions of Loveridgea ionidesii, Monopeltis anchietae, M. capensis, and Trogonophis wiegmanni. Viviparity was interpreted as a derived trait that evolved independently for at least 3 times within the Amphisbaenia. In most species, reproduction is synchronized with the hot and rainy season and seems to vary with latitude. Although Amphisbaenia eggs have been found in ant nests, it remains disputable whether this is an obligatory or even a preferable location for egg-laying. Incubation time in A. mertensii lasts 59 days and this is the first report encompassing egg-laying to hatching for any Amphisbaenia species. Nonetheless, a two months incubation period seems to be the common rule for oviparous Amphisbaenia. The general pattern of reproductive output in Amphisbaenia is characterized by a low number of eggs/embryos per clutch whose individual size is comparatively large in relation to adult body size. Eggs are markedly elongated on the long axis and arranged in-line within the abdominal cavity possibly to prevent/diminish biomechanic drawbacks of egg bearing. Hatchlings of A. mertensi possess an egg-tooth implanted at the upper jaw, exhibit positive geotropism, and display defensive behaviors known to be present in adults. Our review shows that our current knowledge of Amphisbaenia reproduction is fragmentary, often based on the examination of small samples, and heavily dependent on the publication of anedoctal observations. Future publications on this subject are encouraged.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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The sol-gel method combined with a spin-coating technique has been successfully applied for the preparation of rare-earth doped silica:germania films used for the fabrication of erbium-doped waveguide amplifiers (EDWA), presenting several advantages over other methods for the preparation of thin films. As with other methods, the sol-gel route also shows some drawbacks, such as cracks related to the thickness of silica films and high hydrolysis rate of certain precursors such as germanium alkoxides. This article describes the preparation and optical characterization of erbium and ytterbium co-doped SiO2:GeO2 crack-free thick films prepared by the sol-gel route combined with a spin-coating technique using a chemically stable non-aqueous germanium oxide solution as an alternative precursor. The non-crystalline films obtained are planar waveguides exhibiting a single mode at 1,550 nm with an average thickness of 3.9 mu m presenting low percentages of porosity evaluated by the Lorentz-Lorenz Effective Medium Approximation, and low stress, according to the refractive index values measured in both transversal electric and magnetic polarizations. Weakly confining core layers (0.3% < Delta n < 0.75%) were obtained according to the refractive index difference between the core and buffer layers, suggesting that low-loss coupling EDWA may be obtained. The life time of the erbium I-4(13/2) metastable state was measured as a function of erbium concentration in different systems and based on these values it is possible to infer that the hydroxyl group was reduced and the formation of rare-earth clusters was avoided.

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Instrumento de política pública ligado ao licenciamento ambiental prévio de projetos de empreendimentos potencialmente degradadores do ambiente, a Avaliação de Impacto Ambiental (AIA), atualmente, apresenta algumas inconsistências. Dentre elas, autores registram a disparidade no que se refere à indicação e à efetiva implantação das medidas de controle ambiental estabelecidas nos EIA/RIMAs. Diante disso, o presente trabalho analisa a implantação das medidas mitigadoras estabelecidas para empreendimentos minerais licenciados pela Fundação Estadual do Meio Ambiente (FEAM) do Estado de Minas Gerais, para a região do Quadrilátero Ferrífero. No estudo, constata-se que intervenções ambientais são hoje partes integrantes dos projetos minerais; porém, como na mineração a operação impõe certo dinamismo ao empreendimento, verifica-se que parte das medidas mitigadoras apontadas no EIA acaba não sendo executada, como o previsto e o aprovado na fase da Licença Prévia (LP), enquanto outras apenas ficam listadas como propostas de mitigação de impactos, deixando de ser efetivamente executadas.

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Titanium oxide (TiO2) is a good candidate for support of hydrotreating catalysts but has the disadvantage of presenting a low surface area and a poor thermal stability when compared with Al2O3. A mixed TiO2-Al2O3 support was proposed as an alternative that is expected to be free from these drawbacks. The variation during firing of the nanoporous texture of supports composed of TiO2-Al2O3, TiO2 and Al2O3 was studied by small angle X-ray scattering (SAXS). The supports were prepared by the sol-gel route using Ti and Al isopropoxides. We have particularly analyzed the effects of acid and basic hydrolysis on the nanostructural features of catalyst supports fired at different temperatures. The nanopore radius distribution functions were determined from SAXS results assuming a simple model of spherical nanopores embedded in a homogeneous solid matrix. The modal pore radius in both pure TiO2 and pure Al2O3 supports grows from 1.3 to 2.2 nm as the firing temperature increases from 673 to 973 K. on the other hand, the modal pore radius in the mixed TiO2-Al2O3 support remains below 1.2 nm over the same range of firing temperatures. These results demonstrate the good thermal stability of the nanoporous texture of mixed TiO2-Al2O3 supports.