Comparison of Four Space Propulsion Methods for Reducing Transfer Times of Manned Mars Mission

We assess the possibility of reducing the travel time of a manned mission to Mars by examining four different propulsion methods, and keeping the mass at departure under 2,500 tonnes, for a fixed architecture. We evaluated representative systems of three different state of the art technologies (chemical, nuclear thermal, and electric), and one advance technology, the "Pure Electro-Magnetic Thrust" (PEMT) concept (proposed by Rubbia). A mission architecture mostly based on the Design Reference Architecture 5.0 is assumed in order to estimate the mass budget, that influences the performance of the propulsion system. Pareto curves of the duration of the mission and time of flight versus mass of mission are drawn. We conclude that the ion engine technology, combined with the classical chemical engine, yields the shortest mission times for this architecture with the lowest mass, and that chemical propulsion alone is the best to minimise travel time. The results obtained using the PEMT suggest that it could be a more suitable solution for farther destinations than Mars.Comment: Change in title, abstract and presentation so to clarify the main results. 14 pages, 7 figures and 2 table

Avaliação da composição da uva e do vinho varietal 'Tempranillo' segundo a época de produção, na região do Vale do Submédio São Francisco.

O Vale do Submédio do São Francisco é a segunda região produtora de vinhos finos do Brasil, sendo responsável por 15% da produção nacional, com oito milhões de litros/ano

How glassy are neural networks?

In this paper we continue our investigation on the high storage regime of a neural network with Gaussian patterns. Through an exact mapping between its partition function and one of a bipartite spin glass (whose parties consist of Ising and Gaussian spins respectively), we give a complete control of the whole annealed region. The strategy explored is based on an interpolation between the bipartite system and two independent spin glasses built respectively by dichotomic and Gaussian spins: Critical line, behavior of the principal thermodynamic observables and their fluctuations as well as overlap fluctuations are obtained and discussed. Then, we move further, extending such an equivalence beyond the critical line, to explore the broken ergodicity phase under the assumption of replica symmetry and we show that the quenched free energy of this (analogical) Hopfield model can be described as a linear combination of the two quenched spin-glass free energies even in the replica symmetric framework

Wine grape cultivars adaptation and selection for tropical regions.

Wine production is a recent economical activity on tropical regions. In Brazil, tropical wines production started on Sub-Middle São Francisco River Valley Region in the early 1980 years. In the following years, other tropical countries such as Venezuela, Thailand and India have invested in the wine industry. All wine grape cultivars used in the tropical zones are introduced from the traditional temperate winegrowing regions. There are a small number of wine grape cultivars whose cultivation is consolidated in tropical environments, such as ?Syrah? and ?Chenin Blanc?, which possess good adaptation and present a great potential of wine quality. Wine grape cultivars evaluation and selection is one of the important priorities in order to diversify the quality wine production in the tropics. The environmental diversity of tropical zones in comparison with the original regions of wine grape cultivars, all of them from temperate climates, requires detailed evaluation and specific cultural practice adjustments to obtain convenient production from each cultivar and for each tropical environment. Climatic factors as winter absence, temperature changes and rain variations throughout the year change the physiological behavior of vines, offering different grapes and wine qualities at different seasons. In this paper are discussed questions inherent to the screening criteria and evaluation methodology to select wine grape cultivars to produce quality wines in tropical regions. Results obtained at the Sub-Middle São Francisco River Valley are presented.Trabalho apresentado no II International Symposium on Tropical Wines, de 25 a 28 de maio de 2010, Petrolina. Editado por Giuliano Elias Pereira e Jorge Tonietto

On the seismic design of one-story precast structures for P-Δ effects

P-Δ effects can reduce the seismic safety of structures under seismic actions and they can be vital for one-story precast buildings because of the large flexibility of columns. According to European building code, P-Δ effects can be taken into account by following some design requirements. Such requirements can significantly influence the design of the structures since they may provide the amplification of the seismic demand by means of the stability factor as well as the oversizing of the elements. This study investigates the influence of P-Δ effects on the seismic performance of precast one-story structures. An extensive parametric study is performed on one-story precast structures by varying some geometric features of the structure and the seismicity level of the site. Nonlinear dynamic analyses are performed by using Newmark’s method on all the case studies and the results of the first order and second order analysis are compared and discussed. Moreover, different design approaches are adopted in order to assess the Eurocode provisions for P-Δ effects. The results of the nonlinear dynamic analyses demonstrate that the overstrength, due to seismic detailing of columns and the materials overstrength, induces very low ductility demand for the structures. Indeed, even if P-Δ effects are totally neglected in the design phase, the overstrength due to other code prescriptions (e.g. minimum longitudinal reinforcement ratio) can still induce low ductility demand. Moreover it is demonstrated that the code prescriptions on P-Δ effects do not generally increase the structural safety and an alternative design approach is proposed, which gives both safer and cheaper structures than the ones currently designed according to Eurocodes

Regimes hídricos e doses de fósforo em cafeeiro.

O trabalho objetivou estudar os crescimentos vegetativo e reprodutivo e a produtividade de cafeeiro sob três regimes hídricos e quatro doses de adubação fosfatada, no segundo ano após a poda, em solo de Cerrado. A cultivar utilizada foi a Catuaí Rubi MG 1192, Coffea arabica L., com 7.143 plantas ha-1. Os regimes hídricos aplicados foram: sem suspensão da irrigação, feita o ano todo (I); e a partir de 24/6/07, com suspensão da irrigação por 70 dias (SI70); e com suspensão da irrigação por 109 dias (SI109). Os tratamentos SI70 e SI109 foram interrompidos por uma chuva de 12 mm (1.o/10/07), que visualmente induziu a floração. As quatro doses anuais de adubação fosfatada foram: 0 (P0), 100 (P100), 200 (P200) e 400 (P400) kg de P2O5 ha-1. O delineamento experimental foi o de blocos completos ao acaso com o regime hídrico na parcela e a dose de fósforo na subparcela, com três repetições. As doses de fósforo (P200) e (P400) proporcionaram aumento no comprimento e área foliar de ramos, número de frutos e na produtividade de grãos. Os regimes hídricos SI70 e SI109 proporcionaram as maiores porcentagens de frutos cereja e a maior e menor produtividade de grãos respectivamente

A construction method of Atanassov’s intuitionistic fuzzy sets for image processing

In this work we introduce a new construction method of Atanassov\u27s intuitionistic fuzzy sets (A-IFSs) from fuzzy sets. We use A-IFSs in image processing. We propose a new image magnification algorithm using A-IFSs. This algorithm is characterized by its simplicity and its efficiency

Synchrotron Emission from Hot Accretion Flows and the Cosmic Microwave Background Anisotropy

Current estimates of number counts of radio sources in the frequency range where the most sensitive Cosmic Microwave Background (CMB) experiments are carried out significantly under-represent sources with strongly inverted spectra. Hot accretion flows around supermassive black holes in the nuclei of nearby galaxies are expected to produce inverted radio spectra by thermal synchrotron emission. We calculate the temperature fluctuations and power spectra of these sources in the Planck Surveyor 30 GHz energy channel, where their emission is expected to peak. We find that their potential contribution is generally comparable to the instrumental noise, and approaches the CMB anisotropy level at small angular scales. Forthcoming CMB missions, which will provide a large statistical sample of inverted-spectra sources, will be crucial for determining the distribution of hot accretion flows in nearby quiescent galactic nuclei. Detection of these sources in different frequency channels will help constrain their spectral characteristics, hence their physical properties.Comment: 10 pages, 4 figures, accepted for publication in Ap

Quantum Phase Transition and Berry Phase in an Extended Dicke Model

We investigate quantum phase transitions, quantum criticality, and Berry phase for the ground state of an ensemble of non-interacting two-level atoms embedded in a non-linear optical medium, coupled to a single-mode quantized electromagnetic field. The optical medium is pumped externally through a classical electric field, so that there is a degenerate parametric amplification effect, which strongly modifies the field dynamics without affecting the atomic sector. Through a semiclassical description the different phases of this extended Dicke model are described. The quantum phase transition is characterized with the expectation values of some observables of the system as well as the Berry phase and its first derivative, where such quantities serve as order parameters. It is remarkable that the model allows the control of the quantum criticality through a suitable choice of the parameters of the non-linear optical medium, which could make possible the use of a low intensity laser to access the superradiant region experimentally.Comment: 7 pages, 4 figures, submitted to The European Physical Journal