Avaliação dos modelos de predição de propagação para telefonia móvel celular na cidade do Natal

The development of wireless telecommunication in the last years has been great. It has been taking academics to conceive new ideas and techniques. Their aims are to increase the capacity and the quality of the system s services. Cells that are smaller every time, frequencies that are every time higher and environments that get more and more complex, all those facts deserve more accurate models the propagation prediction techniques are inserted in this context and results with a merger of error that is compatible with the next generations of communication systems. The objective of this Work is to present results of a propagation measurement campaign, aiming at pointing the characteristics of the mobile systems covering in the city of Natal (state of Rio Grande do Norte, Brazil). A mobile laboratory was set up, using the infra-structure available and frequently used by ANATEL. The measures were taken in three different areas: one characterized by high buildings, high relief, presence of trees and towers of different highs. These areas covered the city s central zone, a suburban / rural zone and a section of coast surrounded by sand dunes. It is important to highlight that the analysis was made taking into consideration the actual reality of cellular systems with covering ranges by reduced cells, with the intent of causing greater re-use of frequencies and greater capacity of telephone traffic. The predominance of telephone traffic by cell in the city of Natal occurs within a range inferior to 3 (three) km from the Radio-Base Station. The frequency band used was 800 MHz, corresponding to the control channels of the respective sites, which adopt the FSK modulation technique. This Dissertation starts by presenting a general vision of the models used for predicting propagation. Then, there is a description of the methodology used in the measuring, which were done using the same channels of control of the cellular system. The results obtained were compared with many existing prediction models, and some adaptations were developed by using regression techniques trying to obtain the most optimized solutions. Furthermore, according to regulations from the old Brazilian Holding Telebrás, a minimum covering of 90% of a determined previously area, in 90% of the time, must be obeyed when implanting cellular systems. For such value to be reached, considerations and studies involving the specific environment that is being covered are important. The objective of this work is contribute to this aspect

Construção, calibração e análise de desempenho de um piranômetro de baixo custo, baseado no modelo Kimball-Hobbs

In this work a pyrometer using the classic model of Kimball-Hobbs was developed, tested and calibrated. The solar radiation is verified through the temperature difference between the sensible elements covered by absorbing (black) and reflecting (white) pigmentations of the incoming radiation. The photoacoustic technique was used to optimize the choice of the pigments. Methodologies associated with linearity, thermo-variation, sensibility, response time and distance are also presented. To correctly classify the results, the international standard ISO 9060 as well as indicative parameters of World Meteorological Organization (WMO) are used. In addition a system of data acquisition of two channels with 12 bits, constructed during the this time, was used to measure the global solar radiation on the ground by the pyrometer and also by another pyrometer certified in the case of Keep & zonen. The results statistically show, through the hypothesis test presented here, that both equipments find population average with 95% of correctness

Análise da indução de fluxo de ar por convecção livre em chaminé solar

Experiments were performed to study the effect of surface properties of a vertical channel heated by a source of thermal radiation to induce air flow through convection. Two channels (solar chimney prototype) were built with glass plates, forming a structure of truncated pyramidal geometry. We considered two surface finishes: transparent and opaque. Each stack was mounted on a base of thermal energy absorber with a central opening for passage of air, and subjected to heating by a radiant source comprises a bank of incandescent bulbs and were performed field tests. Thermocouples were fixed on the bases and on the walls of chimneys and then connected to a data acquisition system in computer. The air flow within the chimney, the speed and temperature were measured using a hot wire anemometer. Five experiments were performed for each stack in which convective flows were recorded with values ranging from 17 m³ / h and 22 m³ / h and air flow velocities ranging from 0.38 m / s and 0.56 m / s for the laboratory tests and air velocities between 0.6 m/s and 1.1m/s and convective airflows between 650 m³/h and 1150 m³/h for the field tests. The test data were compared to those obtained by semi-empirical equations, which are valid for air flow induced into channels and simulated data from 1st Thermodynamics equation. It was found that the chimney with transparent walls induced more intense convective flows than the chimney with matte finish. Based on the results obtained can be proposed for the implementation of prototype to exhaust fumes, mists, gases, vapors, mists and dusts in industrial environments, to help promote ventilation and air renewal in built environments and for drying materials, fruits and seeds

Efeito do ácido lático sobre as características microbiológicas, físico-químicas e sensoriais na carne do sol

The dried beef is a food traditionally eaten by Northeastern and has an extensive trade in the city of Natal-RN. It is usually produced in an empirical manner, without any standardization in production. Characterized as partially dehydrated meat product, so that the activity of water present is not sufficient to prevent microbial growth, degradation or the production of microbial toxins. The guarantee that the market dried beef is to provide a quality product hygienic, microbiological, physicochemical and sensory stable and adequate for the safety and consumer satisfaction, which has been increasingly attracted to food with natural preservatives. Thus, the meat industries are replacing the current seasonings and natural preservatives for similar, with it without affecting the shelf life of products. Lactic acid has been used to meet these requirements. In this sense, this study aimed to evaluate the effect of lactic acid on the physico-chemical, microbiological and sensory, besides knowing the consumer profile of dried meat of the City of Natal / RN. The results demonstrated that the use of lactic acid in concentrations of 1% and 2% during the processing of dried meat, had statistically significant effect (p < 0.05) on the physico-chemical (pH and water activity) and consequently reduced the microbial count does not alter the taste of the new product developed. Regarding the results on the consumer profile, it was found that the majority of respondents (71.75%) did not observe the presence of the stamp of the Federal Inspection Service (SIF) to buy this meat food that 81.55% of consumers check the hygiene conditions of the site and handlers, however, a large proportion of respondents not concerned with the guarantee of origin of typical regional products featuring a hazard to food safety for consumers of the city of Natal-RN

Avaliação de indicadores de impactos ambientais no perímetro irrigado Cruzeta-Região semi-árida do RN

Environmental impacts are defined as the processes of social and ecological changes caused by nuisance ambient. In agriculture are diverse, and the intensive use of land and inappropriate agricultural practices causes negative effect on the environment besides affecting crop productivity and quality of life of man. So this study was objective to analyze parameters indicators of environmental impacts in the Cruzeta the Discrict Irrigation. During the period July 2007 to March 2008 samples were collected in lot 01 and 02 of the irrigation district. The monitoring was conducted in four sampling points, three (3) located in the irrigation channels and 1 (one) located in a cacimbão. Were monitored pH, CE, STD, SS, NO3-, OD, DT, PST, RAS, CT, Ca+2, Mg+2, Na+ and K+ and heavy metals. Analysis was performed, soil fertility, determining the infiltration rate, moisture content of soil and flow measurement. The results showed that the parameters considered most effective in evaluating the indicators of environmental impacts were: Suspended solid, turbidity, dissolved oxygen and Coliform termotelerantes. The concentrations of nitrate were below the limit established by CONAMA (2005). High levels of STD were found in the point P4. The risk of salinity in cacimbão Lot 02, the water was classified as Class II, or medium risk of salinity in the remaining points was classified as Class I. The iron and aluminum were found high concentrations in four sampling points independent of the dry or rainy. On the ground, found high levels of phosphorus in both samples collected in the batch 01, as the lot 02. The pH levels found in samples of soil, the soil can be classified as neutral and moderate alkalinity. The high infiltration rate obtained in the tests performed in lots 01 and 02 indicated the high permeability of soil at these points