Attitude stability of artificial satellites subject to gravity gradient torque

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Some orbital characteristics of lunar artificial satellites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Artificial satellites orbits in 2:1 resonance: GPS constellation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A DOE based approach for the design of RBF artificial neural networks applied to prediction of surface roughness in AISI 52100 hardened Steel turning

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Sub-Optimal Orbital Maneuvers for Artificial Satellites

The determination of a specific orbit and the procedure to calculate orbital maneuvers of artificial satellites are problems of extreme importance in the study of orbital mechanics. Therefore, the transferring problem of a spaceship from one orbit to another, and the attention due to this subject has in increased during the last years. Many applications can be found in several space activities, for example, to put a satellite in a geostationary orbit, to change the position of a spaceship, to maintain a specific satellite's orbit, in the design of an interplanetary mission, and others. The Brazilian Satellite SCD-1 (Data Collecting Satellite) will be used as example in this paper. It is the first satellite developed entirely in Brazil, and it remains in operation to this date. SCD-1 was designed, developed, built, and tested by Brazilian scientists, engineers, and technicians working at INPE (National Institute for Space Research, and in Brazilian Industries. During the lifetime, it might be necessary do some complementary maneuvers, being this one either an orbital transferring, or just to make periodical corrections. The purpose of transferring problem is to change the position, velocity and the satellite's mass to a new pre determined state. This transfer can be totally linked (in the case of "Rendezvous") or partially free (free time, free final velocity, etc). In the global case, the direction, the orientation and the magnitude of the thrust to be applied must be chosen, respecting the equipment's limit. In order to make this transferring, either sub-optimal or optimal maneuvers may be used. In the present study, only the sub-optimal will be shown. Hence, this method will simplify the direction of thrust application, to allow a fast calculation that may be used in real time, with a very fast processing. The thrust application direction to be applied will be assumed small and constant, and the purpose of this paper is to find the time interval that the thrust is applied. This paper is basically divided into three parts: during the first one the sub-optimal maneuver is explained and detailed, the second presents the Satellite SCD-1, and finally the last part shows the results using the sub-optimal maneuver applied to the Brazilian Satellite.

Wear Particle Classifier System Based on an Artificial Neural Network

This paper describes a method of identifying morphological attributes that classify wear particles in relation to the wear process from which they originate and permit the automatic identification without human expertise. The method is based on the use of Multi Layer Perceptron (MLP) for analysis of specific types of microscopic wear particles. The classification of the wear particles was performed according to their morphological attributes of size and aspect ratio, among others. (C) 2010 Journal of Mechanical Engineering. All rights reserved.

Artificial neural networks and clustering techniques applied in the reconfiguration of distribution systems

One objective of the feeder reconfiguration problem in distribution systems is to minimize the power losses for a specific load. For this problem, mathematical modeling is a nonlinear mixed integer problem that is generally hard to solve. This paper proposes an algorithm based on artificial neural network theory. In this context, clustering techniques to determine the best training set for a single neural network with generalization ability are also presented. The proposed methodology was employed for solving two electrical systems and presented good results. Moreover, the methodology can be employed for large-scale systems in real-time environment.

Artificial neural networks for load flow and external equivalents studies

In this paper an artificial neural network (ANN) based methodology is proposed for (a) solving the basic load flow, (b) solving the load flow considering the reactive power limits of generation (PV) buses, (c) determining a good quality load flow starting point for ill-conditioned systems, and (d) computing static external equivalent circuits. An analysis of the input data required as well as the ANN architecture is presented. A multilayer perceptron trained with the Levenberg-Marquardt second order method is used. The proposed methodology was tested with the IEEE 30- and 57-bus, and an ill-conditioned 11-bus system. Normal operating conditions (base case) and several contingency situations including different load and generation scenarios have been considered. Simulation results show the excellent performance of the ANN for solving problems (a)-(d). (C) 2010 Elsevier B.V. All rights reserved.

Inteligência artificial e teoria de resolução de problemas

Este artigo é uma tentativa de delinear as principais características da pesquisa numa nova área de estudos a chamada Inteligência Artificial (AI). Os itens 1 e 2 constituem um rápido histórico da AI e seus pressupostos básicos. O item 3 trata da teoria de resolução de problemas, desenvolvida por A. Newell e H. Simon. O item 4 procura mostrar a relevância da AI para a Filosofia, em especial para a filosofia da Mente e para a Teoria do Conhecimento.

Robots, intencionalidade e inteligência artificial

O artigo aborda problemas filosóficos relativos à natureza da intencionalidade e da representação mental. A primeira parte apresenta um breve histórico dos problemas, percorrendo rapidamente alguns episódios da filosofia clássica e da filosofia contemporânea. A segunda parte examina o Chinese Room Argument (Argumento do Quarto do Chinês) formulado por J. Searle. A terceira parte desenvolve alguns argumentos visando mostrar a inadequação do modelo funcionalista de mente na construção de robots. A conclusão (quarta parte) aponta algumas alternativas ao modelo funcionalista tradicional, como, por exemplo, o conexionismo.

Umidificação e aquecimento do gás inalado durante ventilação artificial com baixo fluxo e fluxo mínimo de gases frescos

JUSTIFICATIVA E OBJETIVOS: em pacientes sob intubação traqueal ou traqueostomia, a umidificação e o aquecimento do gás inalado são necessários para a prevenção de lesões no sistema respiratório, conseqüentes ao contato do gás frio e seco com as vias aéreas. O objetivo da pesquisa foi avaliar o efeito do sistema respiratório circular com absorvedor de dióxido de carbono do aparelho de anestesia Cícero da Dräger, quanto à capacidade de aquecimento e umidificação dos gases inalados, utilizando-se fluxo baixo (1 L.min-1) ou mínimo (0,5 L.min-1) de gases frescos. MÉTODO: O estudo aleatório foi realizado em 24 pacientes, estado físico ASA I, com idades entre 18 e 65 anos, submetidos à anestesia geral, utilizando-se a Estação de Trabalho Cícero da Dräger (Alemanha), para realização de cirurgias abdominais, os quais foram distribuídos aleatoriamente em dois grupos: grupo de Baixo Fluxo (BF), no qual foi administrado 0,5 L.min-1 de oxigênio e 0,5 L.min-1 de óxido nitroso e fluxo mínimo (FM), administrando-se somente oxigênio a 0,5 L.min-1. Os atributos estudados foram temperatura, umidade relativa e absoluta da sala de operação e do gás no sistema inspiratório. RESULTADOS: Os valores da temperatura, umidade relativa e umidade absoluta no sistema inspiratório na saída do aparelho de anestesia e junto ao tubo traqueal não apresentaram diferença significante entre os grupos, mas aumentaram ao longo do tempo nos dois grupos (BF e FM), havendo influência da temperatura da sala de operação sobre a temperatura do gás inalado, nos dois grupos estudados. Níveis de umidade e temperatura próximos dos ideais foram alcançados, nos dois grupos, a partir de 90 minutos. CONCLUSÕES: Não há diferença significante da umidade e temperatura do gás inalado utilizando-se baixo fluxo e fluxo mínimo de gases frescos.

Artificial oocyte activation using calcium ionophore in ICSI cycles with spermatozoa from different sources

The present study evaluated the effect of artificial oocyte activation (AOA) with calcium ionophore A23187 oil intracytoplasmic sperm injection (ICSI) cycles using spermatozoa from different sources. The 314 cycles evaluated were divided into three groups according to sperm origin, the ejaculated group (n = 92), the epididymal group (n = 82). and the testicular roup (n = 140). Each group was further split into experimental subgroups, depending oil whether or no AOA was performed. In additions the cycles of women younger than 36 years were evaluated separately. For each experimental group, ICSI outcomes were compared between subgroups. No significant difference was observed between subgroups for all sperm origin groups. When evaluating only the cycles of women younger than 36 years of age, AOA increased the percentage of high-quality embryos (74.5 versus 53.0%. P = 0.011) and the implantation rate (19.3 versus 10.5%, P = 0.0025) when it was used with ejaculated spermatozoa, and the percentage of high-quality embryos (64.4 versus 50.3%, P = 0.006) when epididymal spermatozoa were used. These results may suggest that both sperm maturity and oocyte quality play a role in oocyte activation. However. this study is to be continued to confirm these findings.

Artificial oocyte activation with calcium ionophore A23187 in intracytoplasmic sperm injection cycles using surgically retrieved spermatozoa

Objective: To evaluate the effect of artificial oocyte activation (AOA) on intracytoplasmic sperm injection (ICSI) cycles using surgically retrieved sperm.Design: Laboratory study.Setting: Fertility/assisted fertilization center.Patient(s): Couples undergoing surgical sperm retrieval for ICSI (n = 204).Intervention(s): Application of calcium ionophore A23187 for AOA.Main Outcome Measure(s): Cycles were divided into experimental groups according to the origin of the sperm used for injection and the type of azoospermia: [1] testicular sperm aspiration in nonobstructive-azoospermic patients (TESA-NOA group, n = 58), [2] TESA in obstructive-azoospermic patients (TESA-OA group, n = 48), [3] and percutaneous epididymal sperm aspiration in obstructive-azoospermic patients (PESA-OA, n = 98). For each experimental group, cycles where AOA was applied (subgroup: activation) were compared with cycles in which AOA was not applied (Subgroup: control). The fertilization, high-quality embryo, implantation, and pregnancy rates were compared among the subgroups.Result(s): For patients undergoing TESA, AOA did not improve ICSI outcomes for either type of azoospermia. However, for cases in which the injected sperm were retrieved from the epididymis, a statistically significantly increased rate of high-quality embryos was observed with AOA.Conclusion(s): Artificial oocyte activation may improve ICSI outcomes in azoospermic patients when epididymal, but not testicular spermatozoa, are injected. (Fertil Steril (R) 2009;92:131-6. (C)2009 by American Society for Reproductive Medicine.)

Factors affecting conception rates following artificial insemination or embryo transfer in lactating holstein cows

The objective of this study was to evaluate the factors that may affect conception rates (CR) following artificial insemination (AI) or embryo transfer (ET) in lactating Holstein cows. Estrous cycling cows producing 33.1 +/- 7.2 kg of milk/d received PGF(2 alpha) injections and were assigned randomly to 1 of 2 groups (AI or ET). Cows detected in estrus (n = 387) between 48 and 96 h after the PGF2a injection received AI (n = 227) 12 h after detection of estrus or ET (n = 160) 6 to 8 d later (1 fresh embryo, grade 1 or 2, produced from nonlactating cows). Pregnancy was diagnosed at 28 and 42 d after estrus, and embryonic loss occurred when a cow was pregnant on d 28 but not pregnant on d 42. Ovulation, conception, and embryonic loss were analyzed by a logistic model to evaluate the effects of covariates [days in milk (DIM), milk yield, body temperature (BT) at d 7 and 14 post-AI, and serum concentration of progesterone (P4) at d 7 and 14 post-AI] on the probability of success. The first analysis included all cows that were detected in estrus. The CR of AI and ET were different on d 28 (AI, 32.6% vs. ET, 49.4%) and 42 (AI, 29.1% vs. ET, 38.8%) and were negatively influenced by high BT (d 7) and DIM. The second analysis included only cows with a corpus luteum on d 7. Ovulation rate was 84.8% and was only negatively affected by DIM. Conception rates of AI and ET were different on d 28 (AI, 37.9% vs. ET, 59.4%) and 42 (AI, 33.8% vs. ET, 46.6%) and were negatively influenced by high BT (d 7). The third analysis included only ovulating cows that were 7 d postestrus. Conception rates of AI and ET were different on d 28 (AI, 37.5% vs. ET, 63.2%) and 42 (AI, 31.7% vs. ET, 51.7%) and were negatively influenced by high BT (d 7). There was a positive effect of serum concentration of P4 and a negative effect of milk production on the probability of conception for the AI group but not for the ET group. The fourth analysis was embryonic loss (AI, 10.8% vs. ET, 21.5%). The transfer of fresh embryos is an important tool to increase the probability of conception of lactating Holstein cows because it can bypass the negative effects of milk production and low P4 on the early embryo. The superiority of ET vs. AI is more evident in high-producing cows. High BT measured on d 7 had a negative effect on CR and embryonic retention.