Modelo 2,5D de predição de propagação para ambientes interiores utilizando o método do traçado de raios

A 2.5D ray-tracing propagation model is proposed to predict radio loss in indoor environment. Specifically, we opted for the Shooting and Bouncing Rays (SBR) method, together with the Geometrieal Theory of Diffrartion (GTD). Besides the line-of-sight propagation (LOS), we consider that the radio waves may experience reflection, refraction, and diffraction (NLOS). In the Shooting and Bouncing Rays (SBR) method, the transmitter antenna launches a bundle of rays that may or may not reach the receiver. Considering the transmitting antenna as a point, the rays will start to launch from this position and can reach the receiver either directly or after reflections, refractions, diffractions, or even after any combination of the previous effects. To model the environment, a database is built to record geometrical characteristics and information on the constituent materials of the scenario. The database works independently of the simulation program, allowing robustness and flexibility to model other seenarios. Each propagation mechanism is treated separately. In line-of-sight propagation, the main contribution to the received signal comes from the direct ray, while reflected, refracted, and diffracted signal dominate when the line-of-sight is blocked. For this case, the transmitted signal reaches the receiver through more than one path, resulting in a multipath fading. The transmitting channel of a mobile system is simulated by moving either the transmitter or the receiver around the environment. The validity of the method is verified through simulations and measurements. The computed path losses are compared with the measured values at 1.8 GHz ftequency. The results were obtained for the main corridor and room classes adjacent to it. A reasonable agreement is observed. The numerical predictions are also compared with published data at 900 MHz and 2.44 GHz frequencies showing good convergence

Fraturas e caminhos ótimos na rede de Barabasi-Albert

Following the study of Andrade et al. (2009) on regular square lattices, here we investigate the problem of optimal path cracks (OPC) in Complex Networks. In this problem we associate to each site a determined energy. The optimum path is defined as the one among all possible paths that crosses the system which has the minimum cost, namely the sum of the energies along the path. Once the optimum path is determined, at each step, one blocks its site with highest energy, and then a new optimal path is calculated. This procedure is repeated until there is a set of blocked sites forming a macroscopic fracture which connects the opposite sides of the system. The method is applied to a lattice of size L and the density of removed sites is computed. As observed in the work by Andrade et al. (2009), the fractured system studied here also presents different behaviors depending on the level of disorder, namely weak, moderated and strong disorder intensities. In the regime of weak and moderated disorder, while the density of removed sites in the system does not depend of the size L in the case of regular lattices, in the regime of high disorder the density becomes substantially dependent on L. We did the same type of study for Complex Networks. In this case, each new site is connected with m previous ones. As in the previous work, we observe that the density of removed sites presents a similar behavior. Moreover, a new result is obtained, i.e., we analyze the dependency of the disorder with the attachment parameter m

O ensino da língua portuguesa na televisão: uma análise através do programa afinando a língua

The present dissertation aims to an approach of the teaching of Portuguese language on television, trying to find how possible is the contribution of this communication media in the sense to give a higher classroom dynamism and to excite the students for that subject. The TV show Afinando a Língua (roughly, putting the language in tune ), a Canal Futura feature, have as one of these main purpose be shown on the classrooms as a tool that could enlarge the possibilities of a subject often took as particularly difficult. Blocked by the traditional grammatical teaching, the Portuguese lessons have been for years pictured as hermetic and far from the Brazilian speakers reality. So, people create myths around the language that earns adjectives as complicate and inaccessible and that Brazilians can t speak the Portuguese really good, because it only happens in Portugal, the original country of the language. These myths start exactly because the teaching orientation take their basis only on the standard language, in fact just one of the language variations by the way, anywhere in the world dictated by ancestral rules, once produced in Portugal. The regular school don t accept the Portuguese variation as a natural fact for a huge country as Brazil, with almost 190 million people, regarding it as a wrong way of talking. The repression that follows the students from the early school days make them repel the language supposedly learned at school. In fact, they normally face it as something unfamiliar, different from the language that they have use to learn at home, from the family and neighbors Instead of giving new possibilities for the language learning, the television, a powerful audiovisual device, only reinforces the idea that everyone, in any life situation, should talk the standard Portuguese, turning its back to the learning acquired much earlier that any person reach the school. This conservative attitude brings almost no changes, between the shows that try to teach the idiom and the traditional Portuguese lessons, wasting valuable tools that could lead to the possibility to open the classroom to the outside world, and to the wider knowledge of the differences from each Brazilian region culture, a positive attitude that could much enlarge the cultural and linguistic students universe