Solar array study for solar electric propulsion spacecraft for the Encke rendezvous mission

The work is described which was performed on the design, analysis and performance of a 20 kW rollup solar array capable of meeting the design requirements of a solar electric spacecraft for the 1980 Encke rendezvous mission. To meet the high power requirements of the proposed electric propulsion mission, solar arrays on the order of 186.6 sq m were defined. Because of the large weights involved with arrays of this size, consideration of array configurations is limited to lightweight, large area concepts with maximum power-to-weight ratios. Items covered include solar array requirements and constraints, array concept selection and rationale, structural and electrical design considerations, and reliability considerations

Kounis Syndrome Associated With Selective Anaphylaxis to Cefazolin.

info:eu-repo/semantics/publishedVersio

Development and evaluation of lessons for class and group situations in grade one

Thesis (Ed.M.)--Boston Universit

Optimal R&D subsidies in a model with physical capital, human capital and varieties

Copyright © 2013 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Economic Modelling. Changes resulting from the publishing process, such as editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. A definitive version was subsequently published in Economic Modelling 30, 217-224, 2013. DOI: http://dx.doi.org/10.1016/j.econmod.2012.07.019.[Abstract] In this paper, we analyze the social planner solution of an endogenous growth model with physical capital, human capital and R&D. The model incorporates three sources of inefficiency: monopolistic competition in the intermediate-goods sector, duplication externalities and spillovers in R&D. A complete stability analysis for the optimal growth problem of this model is provided. We characterize the optimal policy that can decentralize the optimal solution and find that the path of the optimal R&D subsidy can be non-monotonic.Ministerio de Economía y Competitividad; ECO2011-25490Portugal. Fundação para a Ciência e a Tecnologia; PTDC/EGE-ECO 102238/200

The transitional dynamics of an endogenous growth model: Generalizing production functions

The final publication is available at www.degruyter.comThis paper devises a class of endogenous growth models with physical capital, human capital and product varieties. Unlike previous literature, we introduce a general specification of production that allows for disentangling the gains from specialization from the monopolistic markup. The consequences of separating both parameters on the equilibrium dynamics of the model are analyzed. We find that the long-run growth rate ceases to depend on the markup when it is disentangled from the returns to specialization, and the same happens with the conditions for saddle-path stability. Numerical simulations show that the steady-state equilibria are more prone to be stable in the model that disentangles parameters. Furthermore, the model is able to generate a rich variety of development scenarios, accounting for a number of stylized facts related to the development process of industrialized countries.Ministerio de Ciencia e Innovación; ECO2011-25490.Portugal. Fundacão para a Ciência e Tecnologia; PTDC/EGE-ECO 102238/200

Phases of Economic Development: Do Initial Endowments Matter?

The final publication is available at www.degruyter.com[Abstract] Different industrializing experiences beginning on innovation or education could be explained not only by different structural parameters or policies but also by differences in factor endowments. In this paper, we consider an endogenous growth model with physical capital, human capital and R&D. We show that the initial endowments can determine the sequence of the phases of development that the economy follows; in particular, whether innovation precedes education or viceversa.Manuel Gómez gratefully acknowledges financial support from the Spanish Ministry of Science and Innovation through Grant ECO2011-25490. Tiago Sequeira gratefully acknowledges financial support from the Portuguese Ministry of Science, Technology and Higher Education, through FCT project PTDC/EGE-ECO/102238/2008Portugal. Fundação para a Ciência ea Tecnologia; PTDC/EGE-ECO/102238/200

The effect of phase transitions on the droplet size distribution in homogeneous isotropic turbulence

We investigate the dynamics of an ensemble of discrete aerosol droplets in a homogeneous, isotropic turbulent flow. Our focus is on the stationary distribution of droplet sizes that develops as a result of evaporation and condensation effects. For this purpose we simulate turbulence in a domain with periodic boundary conditions using pseudo-spectral discretization. We solve in addition equations for the temperature and for a scalar field, which represents the background humidity against which the size of the droplets evolves. We apply large-scale forcing of the velocity field to reach a statistically steady state. The droplets are transported by the turbulent field while exchanging heat and mass with the evolving temperature and humidity fields. In this Euler-Lagrange framework, we assume the droplets volume fraction to be sufficiently low to allow one-way coupling of the droplets and turbulence dynamics. The motion of the droplets is time-accurately tracked. The Stokes drag force is included in the equation of motion of the individual droplets. The responsiveness of the droplets to small turbulent scales is directly related to the size of the individual spherical droplets. We perform direct numerical simulation to ultimately obtain the probability density function of the evolving radius of the droplets at different points in time with characteristic heat and mass transfer parameters. We determine the gradual convergence of the distribution function to its statistically stationary state for forced homogeneous, isotropic turbulence

Aluminum matrix texture and particle characterization in Al-Al3Ti FGMs produced by a centrifugal solid-particle method

The centrifugal solid-particle method has proved to be effective in producing functionally graded materials (FGMs). In this study, Al-Al3Ti FGMs, were produced by this centrifugal method, from an Al-5 wt % Ti master alloy. Applied centrifugal forces were 30, 60 and 120G (units of gravity). Samples from the outer surface of each specimen were cut and aluminum matrix texture analyzed by Schulz reflection method. Analysis of the resulting pole figures indicates a preferred orientation along the (200) plane for the aluminum matrix crystals. Furthermore, increasing the applied centrifugal force enhances the orientation effect. Al3Ti platelet orientation and area fraction at the samples’ outer surface along three observation planes were also measured. The Al3Ti platelets in the outer region are orientated perpendicular to the centrifugal force direction along two of the observed planes, also an increase in centrifugal force leads to an increase in orientation in those two planes. The intermetallic particle volume fraction also increases with higher applied centrifugal force, although not significantly. A correlation appears to exist between particle orientation and the preferred orientation of the matrix.(undefined