902 resultados para Lai


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Estimation of soil parameters by inverse modeling using observations on either surface soil moisture or crop variables has been successfully attempted in many studies, but difficulties to estimate root zone properties arise when heterogeneous layered soils are considered. The objective of this study was to explore the potential of combining observations on surface soil moisture and crop variables - leaf area index (LAI) and above-ground biomass for estimating soil parameters (water holding capacity and soil depth) in a two-layered soil system using inversion of the crop model STICS. This was performed using GLUE method on a synthetic data set on varying soil types and on a data set from a field experiment carried out in two maize plots in South India. The main results were (i) combination of surface soil moisture and above-ground biomass provided consistently good estimates with small uncertainity of soil properties for the two soil layers, for a wide range of soil paramater values, both in the synthetic and the field experiment, (ii) above-ground biomass was found to give relatively better estimates and lower uncertainty than LAI when combined with surface soil moisture, especially for estimation of soil depth, (iii) surface soil moisture data, either alone or combined with crop variables, provided a very good estimate of the water holding capacity of the upper soil layer with very small uncertainty whereas using the surface soil moisture alone gave very poor estimates of the soil properties of the deeper layer, and (iv) using crop variables alone (else above-ground biomass or LAI) provided reasonable estimates of the deeper layer properties depending on the soil type but provided poor estimates of the first layer properties. The robustness of combining observations of the surface soil moisture and the above-ground biomass for estimating two layer soil properties, which was demonstrated using both synthetic and field experiments in this study, needs now to be tested for a broader range of climatic conditions and crop types, to assess its potential for spatial applications. (C) 2012 Elsevier B.V. All rights reserved.

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The effect of thermal-mechanical loading on a surface mount assembly with interface cracks between the solder and the resistor and between the solder and the printed circuit board (PCB) was studied using a non-linear thermal finite element analysis. The thermal effect was taken as cooling from the solder eutectic temperature to room temperature. Mechanical loading at the ends of the PCB was also applied. The results showed that cooling had the effect of causing large residual shear displacement at the region near the interface cracks. The mechanical loading caused additional crack opening displacements. The analysis on the values of J-integral for the interface cracks showed that J-integral was approximately path independent, and that the effect of crack at the solder/PCB interface is much more serious than that between the component and solder.

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The mechanical behaviour of a composite of Al–5Cu matrix reinforced with 15% SiC particles was studied at different strain rates from 1×10−3 to 2.5×103 s−1 using both a conventional universal testing machine (for low strain-rate tests) and a split Hopkinson bar (for tests at dynamic strain rates). Whilst the yield stress of the composite increases as the strain rate increases, the maximum flow stresses, 440 MPa for compression and 450 MPa for tension, are independent of strain rate. The microstructures and defect structures of the deformed composite were studied with both scanning electron microscopy and transmission electron microscopy and were correlated to the observed mechanical behaviour. Fracture surface studies of samples after dynamic tensile testing indicates that failure of the composite is controlled by ductile failure of the aluminium matrix by the nucleation, growth and coalescence of voids.

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对涡轮流量传感器进行了理论分析,给出了涡轮流量计仪表常数的计算方法,讨论了获得较大固有仪表常数K_0时涡轮传感器结构参数(如叶片数、涡轮半径、口径等)的优化组合问题,通过多相流动实验,总结出K_0与流动密度之间的实验关系,由此给出用涡轮流量计测量多相流的半理论半经验公式,并在油井多相流量测量中得到了实际应用,符合较好。

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Em cumprimento ao disposto no art. 30 da Lei nº 12.527, de 2011, a Câmara dos Deputados apresenta à sociedade brasileira seu primeiro relatório consolidado sobre a aplicação da Lei de Acesso a Informação – LAI. Este relatório é dividido em três seções e um apêndice metodológico. A primeira seção traz informações e dados estatísticos sobre as solicitações de acesso a informação recebidas pela Câmara dos Deputados entre os dias 16/05/2012, data de início de vigência da LAI, e 30/04/2013. Além de tabela específica sobre solicitações de informação recebidas, atendidas e indeferidas, são apresentados dados consolidados sobre a distribuição temática dos requerimentos, as razões para indeferimento e a distribuição dos prazos de atendimento das solicitações.

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Examina a aplicação da Lei nº 12.527, de 18 de novembro de 2011 – a Lei de Acesso à Informação (LAI) – tendo como locus a Câmara dos Deputados e o seu órgão de gestão da informação, de relacionamento e de atendimento ao público usuário, o Centro de Documentação e Informação (Cedi) e, em particular, a Coordenação de Relacionamento, Pesquisa e Informação (Corpi). Analisa-se, à luz da Ciência da Informação, o impacto causado pela LAI no processo de provimento de informação e na disponibilidade da informação institucional para a sociedade, no contexto do amplo acesso às informações públicas, desejável na Câmara. A pesquisa, de caráter documental, firma-se em documentos e na legislação produzidos na esfera da Câmara dos Deputados. Para o estudo do caso, utilizou-se entrevista com servidores da Corpi, onde se colheram impressões sobre o impacto da LAI na dinâmica do trabalho de atendimento e pesquisa, identificaram-se os principais problemas percebidos e as suas sugestões de melhoria. Discorre-se, também, subsidiariamente, sobre a gestão da informação como parte do ciclo informacional e condição para o acesso à informação, tópico central desta pesquisa. Aborda-se a questão da cidadania e do controle social, bem o direito à informação e transparência governamental que subjazem à proposta de amplo acesso à informação pública preconizada pela LAI, em razão da mudança de paradigma e do regime de informação a que a LAI conduz. O estudo dos efeitos da LAI no âmbito da Câmara teve como marco temporal o período de maio a dezembro de 2012. Estima-se que os indicadores desta pesquisa possam contribuir com estudos futuros relacionados com a governança da informação na Câmara.

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We propose a universal quantum computation scheme for trapped ions in thermal motion via the technique of adiabatic passage, which incorporates the advantages of both the adiabatic passage and the model of trapped ions in thermal motion. Our scheme is immune from the decoherence due to spontaneous emission from excited states as the system in our scheme evolves along a dark state. In our scheme the vibrational degrees of freedom are not required to be cooled to their ground states because they are only virtually excited. It is shown that the fidelity of the resultant gate operation is still high even when the magnitude of the effective Rabi frequency moderately deviates from the desired value.

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A feasible scheme for constructing quantum logic gates is proposed on the basis of quantum switches in cavity QED. It is shown that the light field which is fed into the cavity due to the passage of an atom in a certain state can be used to manipulate the conditioned quantum logical gate. In our scheme, the quantum information is encoded in the states of Rydberg atoms and the cavity mode is not used as logical qubits or as a communicating "bus"; thus, the effect of atomic spontaneous emission can be neglected and the strict requirements for the cavity can be relaxed.