Limites e possibilidades do programa nacional de alimentação escolar enquanto estratégia de promoção da segurança alimentar e nutricional no municipio de Macaíba/RN

This dissertation aims to understand the importance of the National School Feeding as a strategy for ensuring the promotion of food and nutrition security in the municipality of Macaíba / RN, taking into account the implementation of the Law School Feeding, 11,947, 2009. The program was extended to all public basic education, youth and adults, in addition to ensuring that 30% of transfers from FNDE, were intended for the purchase of products from family farms. The survey was conducted with 160 students from public schools and farmers nesting Quilombo dos Palmares II, who produce on their land vegetables, fruits and cereals for their own consumption, for sale in local markets, in addition to providing for PNAE. The reciprocity between neighbors, such as mutual aid and sharing of common goods was noticeable in this group of farmers, since it was necessary to meet weekly deliveries of products to schools. As students, we applied a test of acceptability in two schools located in rural and in urban areas, to learn the opinion of ourselves in relation to school food consumed. It was concluded that to be most effective program in the region, there must be a better match in school menus, so that it can be attractive to students and to ensure greater use of fresh food, the main ingredient of same, practice of nutrition education in schools, to teach students the importance of food to health. In relation to local management, noted the need for adjustments bureaucratic as hiring staff for the departments, in order to be more agile in releasing payments to farmers, in addition to hiring assistants general services for schools, one Since the cooks exert dual role, the cooking while being responsible for cleaning the entire school environment. Government investments in the rural sector would be extremely valuable for farmers, since they need financial resources to purchase inputs, irrigation projects for gardens, availability of land for planting, transportation to facilitate the delivery of its products to schools and technical assistance more frequently

Uma fonte chaveada de 50kW com correção de fator de potência para alimentação de uma tocha de plasma Indutiva utilizando técnicas de controle digital

This work deals with the development of an experimental study on a power supply of high frequency that provides the toch plasmica to be implemented in PLASPETRO project, which consists of two static converters developed by using Insulated Gate Bipolar Transistor (IGBT). The drivers used to control these keys are triggered by Digital Signal Processor (DSP) through optical fibers to reduce problems with electromagnetic interference (EMI). The first stage consists of a pre-regulator in the form of an AC to DC converter with three-phase boost power factor correction which is the main theme of this work, while the second is the source of high frequency itself. A series-resonant inverter consists of four (4) cell inverters operating in a frequency around 115 kHz each one in soft switching mode, alternating itself to supply the load (plasma torch) an alternating current with a frequency of 450 kHz. The first stage has the function of providing the series-resonant inverter a DC voltage, with the value controlled from the power supply provided by the electrical system of the utility, and correct the power factor of the system as a whole. This level of DC bus voltage at the output of the first stage will be used to control the power transferred by the inverter to the load, and it may vary from 550 VDC to a maximum of 800 VDC. To control the voltage level of DC bus driver used a proportional integral (PI) controller and to achieve the unity power factor it was used two other proportional integral currents controllers. Computational simulations were performed to assist in sizing and forecasting performance. All the control and communications needed to stage supervisory were implemented on a DSP

Caracterização de superfícies seletivas de freqüência e de antenas fractais para aplicações em redes sem fio

This work aims to investigate the behavior of fractal elements in planar microstrip structures. In particular, microstrip antennas and frequency selective surfaces (FSSs) had changed its conventional elements to fractal shapes. For microstrip antennas, was used as the radiating element of Minkowski fractal. The feeding method used was microstrip line. Some prototypes were built and the analysis revealed the possibility of miniaturization of structures, besides the multiband behavior, provided by the fractal element. In particular, the Minkowski fractal antenna level 3 was used to exploit the multiband feature, enabling simultaneous operation of two commercial tracks (Wi-Fi and WiMAX) regulated by ANATEL. After, we investigated the effect of switches that have been placed on the at the pre-fractal edges of radiating element. For the FSSs, the fractal used to elements of FSSs was Dürer s pentagon. Some prototypes were built and measured. The results showed a multiband behavior of the structure provided by fractal geometry. Then, a parametric analysis allowed the analysis of the variation of periodicity on the electromagnetic behavior of FSS, and its bandwidth and quality factor. For numerical and experimental characterization of the structures discussed was used, respectively, the commercial software Ansoft DesignerTM and a vector network analyzer, Agilent N5230A model

Análise do comportamento e crescimento do camarão branco Litopenaeus vannamei (Boone, 1931) em diferentes substratos inconsolidados

The aim of this study was to test the sediment preference of L. vannamei shrimp. It was observed shrimp visit frequency, swimming and burying behaviour at different sediment compositions for 24h. Juvenile (0.93 ± 0.29g) and sub-adult shrimps (10.0 ± 1.18g) were obtained from the aquaculture station at Universidade Federal Rural do Semi-Árido UFERSA, and held in a plastic tank (water volume 500 L) supplied with aerated water and kept at constant temperature, pH, and salinity. Shrimp was fed by commercial shrimp dry food. The experimental substrates were composed by A: medium sand + thick sand + very thick sand + gravel; B: very fine sand + fine sand; and C: silt + clay. Thus, six different substrate combinations were tested: A, B, C, A+B, A+C, B+C. To test preference, it was used a cylindrical tank (40 l) divided into six differently substrate compartments. A single shrimp was introduced each tank and the frequency at which this shrimp visited each compartment was recorded over a 24h study period. It was tested 54 shrimp (18 sub-adult males, 18 subadult females and 18 juveniles). For each trial, sediment and water were changed to avoid pheromones and residues influence. Shrimp were weighted and sub-adults were divided by sex: males present petasma and females present thelycum. Data were collected on the experimental day at 19:30; 20:30; 00:30; 1:30; 05:30; 06:30; 13:30 and 14:30 h. At each time point, shrimp were observed for 20-min periods, in which we noted down which compartment the shrimp was occupying at 2-min intervals. Thus, for each period we had eleven observations (88 observations per day). For observations at night, it was used dim red light that did not affect shrimp behaviour. At each 20-min period, it was observed visit frequency in each substrate, if shrimp was burred or not or if it was swimming. There was not significant difference between light and dark burry activity for females. Swimming activity was significantly higher at night, mainly at 00:30 and 01:30 h. All L. vannamei shrimp showed preference for sediment B. This animal presents cyclic activity, spends the day light period buried and swims at night

Ecologia alimentar e reprodutiva da piaba-do-rabo-amarelo, Astyanax cf. lacustris (Reinhardt, 1874) (Osteichthyes: Characidae) na Lagoa do Piató, Assu, Rio Grande do Norte, Brasil

The feeding habits and biological aspects of the reproductive cycle of two-spot astyanax, Astyanax cf. lacustris (Reinhardt, 1874) were investigated. Fish samples were captured on a monthly basis, using gillnets of 4 cm mesh size, from the Piató Lake, Assu, Rio Grande do Norte, during the period of September, 2006 to August, 2007. Physico-chemical parameters, such as, temperature, electrical conductivity and dissolved oxygen of the lake were registered. The monthly values of rainfall also were obtained. The 360 individuals captured, were measured, weighed, dissected, and stomach weight and the stage of gonadal maturity were registered. The stomach contents analyses were carried out based on volumetric method, points, frequency of occurrence and applying the Index of Relative Importance. The degrees of repletion of the stomachs were determined besides the Index of Repletion relating to feeding activity variations and frequency of ingestion with limnological parameters and rainfall. The food items identified were separated into distinct groups according to their origin. Sex ratio and Gonadosomatic Relation of females were verified to determine the spawning period and fecundity. The physico-chemical parameters presented the following annual mean values: temperature = 28.8ºC, electrical conductivity = 992.5 µS.cm-1; dissolved oxygen = 4.9 mg.L-1 during the study period. The annual mean of the rainfall was 63.5 mm. The results indicate that this species present an omnivorous feeding habit with a tendency towards insectivory, with an increase in feeding activity during the dry season. The aquatic oxygen to interfere very importance in the feeding activity than the others factors physico-chemicals of water and rainfall. There was a predominance of females, with a sex proportion of 1M:7F. The macroscopic characteristics of the ovaries and testicles revealed four stages of gonadal development: immature, maturing, mature and spent. A temporal variation was observed for the gonadal development of males and females. There was reproductive activity through out the year, with peaks in the months of February, April and June to correspond with the rain of precipitation of the region. The mean fecundity was 7.681 mature oocytes, varying from 4.476 to 12.036, with mean of 7.681. There was positive relation between fecundity and body mass. Condition Factor is not an efficient indicator of the reproductive period of this species. The species A. cf. lacustris is an opportunist and is well adapted to the conditions of the semi-arid Caatinga Biome

Influência da alimentação sobre os níveis de retinol do leite caprino

The caprine milk is a product of high biological value and high digestibility. Due to these characteristics it is quite used by newly born children that are not breastfed or that are intolerant to the bovine milk. The vitamin deficiency is a public health problem in underdeveloped areas as the Northeast of Brazil and where areas the caprine ones adapt very well. The present study was led to analyze the influence of the feeding in the vitamin levels in the caprine milk. The animals used were the races Saanen and Murciana, divided in three groups. The first group with 38 animals of race Saanen and the second with 30 animals of race Murciana were, fed with concentrated and voluminous. A third group with 20 animals of the race Saanen was fed exclusively with voluminous. The four group was added with 10. 000 UI of retinol palmitato, administered directly, like capsule, in the mouth of animal. Parallel it was verified the level of retinol of milk in the beginning and final of the sucked, in the goats of the second group (race Murciana n =30). The retinol of caprine milk was determined through the system of liquid cromatografia of high efficiency (HPLC). The retinol levels in the studied groups were respectively: first (38. 5 ± 12. 7 μg/100ml), second (40. 5 ± 9. 7 μg/100ml); third, with 20 animals of race Saanen fed exclusively with voluminous (23. 1 ± 6. 7 μg/100ml) and in the group a, suplementation with 10. 000 UI of retinol palmitato (43,7 ± 18,8 μg/100ml) before, and (61,9 ± 26,9 μg/100ml) after the supplementation. It was not found significant difference between the averages from animals of the first and second group, that were fed with the same concentrate diet and voluminous, showing that the retinol levels in the milk of these two races are equivalent. Already in the animals of the first and third group that they were fed with different diets, in those which diet was just voluminous, a drastic reduction was verified in the retinol levels. In relation to the retinol of the milk in different moments from the same sucked, it was observed in the beginning of the breast-feeding (22. 6 ± 9. 8 μg/100ml) and at the end of the sucked (49. 6 ± 14. 7μg/100ml), being the difference between the averages, statistically significant (p < 0,0001). Already in the animals that were supplemented, a significant increase was observed in the retinol concentration, being obtained a medium response of 41,85%

Estudos analíticos dos grafoelementos do eletroencefalograma em sono: fusos do sono, ondas agudas do vértex e o gradiente de freqüência e amplitude, como indicadores de comprometimento neurológico na criança

Innumerable studies have focused been reported on the sleep spindles (SS), Sharp Vertex Waves (SVW) and REM, NREM Sleep as indicators interpreting EEG patterns in children. However, Frequency and Amplitud Gradient (FAG) is rarely cited sleep parameter in children,that occurs during NREM Sleep. It was first described by Slater and Torres, in 1979, but has not been routinely evaluated in EEG reports. The aim of this study was to assess the absence of SS, SVW and FAG, as an indication of neurological compromise in children. The sample consisted of 1014 EEGs of children referred to the Clinical Neurophysiology Laboratory, Hospital Universitário de Brasília (HUB), from January 1997 to March 2003, with ages ranging from 3 months to 12 years old, obtained in spontaneous sleep or induced by choral hydrate. The study was transversal and analytical, in which, visual analysis of EEG traces was perfumed individually and independently by two electroencephalographers without prior knowledge of the EEG study or neurological findings. After EEG selection, the investigators analyzed the medical reports in order to define and correlate neurological pattern was classified according to the presence or absence of neurological compromise, as Normal Neurological Pattern (NNP), and Altered Neurological Pattern (ANP) respectively. From the visual analysis of the EEG(s), it was possible to characterize 6 parameters: 1- FAG present (64,1%); 2- FAG absent (35,9%); 3 - normal SS (87,9%); 4 - altered SS s (12,1%); 5 - normal SVW s (95,7%); 6 - altered SVW s (4,3%). The prevalence of well-formed FAG is found in the 3 months to 5 years age group in the children with NNF. FAG was totally absent from the age of 10 years. When comparing the three sleep graphielements, it was observed that SVW and SS were predominant in children with NNF. However, FAG absent was more prevalent in the ANF than in altered SS an SVW. The statistical analysis showed that there is a strong association of FAG absent, with isolated alteration, in ANF patients, in that the prevalence ratio was 6,60. The association becomes stronger when FAG absent + altered SS(s) is considered (RP= 6,68). Chi-square test, corrected by Yates technique, showed a highly significant relation for FAG ρ= 0,00000001, for error X of 5%, or else the 95% confidence interval (ρ<0,05). Thus, the FAG absent were more expressive in ANF patient than altered SS(s) and SVW(s). The association becomes stronger in order to establish a prognostic relation, when the FAG is combined with the SS. The results os this study allow us to affirm that the FAG, when absent at ages ranging from 3 months to 5 years , is an indication of neurological compromise. FAG is an age-dependent EEG parameter and incorporated systematically, in the interpretation criteria of the EEG of children s sleep, not only in the maturational point of view, but also neurological disturbances with encephalic compromise

Avaliação das condições higiênico-sanitárias da produção de refeições à base de carne da alimentação escolar no município de Natal-RN

The National School Nutrition Program is the oldest program in the country directed at food and nutrition safety. Its aims are to offer nutritional food as a supplement to students of public and philanthropic schools. Studying school nutrition transcends the investigation as a purely social program, given that it reaches the fields of public health, nutrition and food, using a wide variety of approaches. Thus, it is characterized by a multidisciplinary study, where the disciplines work side by side in distinct aspects of a single problem. Aim: This study aims to assess hygiene practices during the preparation of meat-based meals in public schools in the city of Natal, Brazil. Methods: A list was applied at 27 schools to identify the procedures of good food preparation practices. In addition, cooking and meal distribution temperature were measured and a microbiological analysis of the final preparation and of the water used in preparing it was performed. For microbiological analyses of the food, we analyzed coliforms at 45°C, coliforms at 35°C and Enterococcus, and for the water, we analyzed thermotolerant coliforms and total coliforms, using the methods recommended by APHA, 1995. Results: Most of the schools did not meet the required standards in all the variables related to good food preparation practices, except for the time spent preparing the meat, in which 89% were within the norm. Cooking temperature of the meals was within the standard; however, the temperature at distribution and the time spent dispensing the meals were inadequate. Of the 27 schools, 22 (81.5%) showed the presence of coliforms at 35° C in at least one meal sample and 18 (66.7%) had values above the recommended limit for coliforms at 45°C. The presence of E. coli was identified in 6.1% of the samples analyzed. The presence of Enterococcus was not found at any of the schools. With respect to the water, the North district of the city was the only one that did not meet the standards for the two indicators evaluated. The contamination found was not associated with the hygiene or food storage problems observed. Conclusions: The results show that the hygiene-sanitary conditions of meat-based public school meals were unsatisfactory, demonstrating the need for improvements in the production process to preserve the health of the student population. Multidisciplinarity: Researchers from the areas of food microbiology, nutrition, public health and statistics took part in this study, a decisive factor for characterizing the research as multidisciplinary

Qualidade nutricional dos cardápios em escolas públicas e alcance às metas do programa nacional de alimentação escolar em município do nordeste brasileiro

O Programa Nacional de Alimentação Escolar tem como objetivo atender as necessidades nutricionais dos alunos durante sua permanência em sala de aula, contribuindo para o crescimento, o desenvolvimento, o rendimento escolar e a formação de hábitos alimentares saudáveis. Diante da relevância social e considerando os princípios do direito humano da alimentação adequada e da segurança alimentar, é fundamental o monitoramento da execução e consecução das metas nutricionais estabelecidas pelo programa. Desta forma, este estudo teve como objetivos analisar a qualidade nutricional dos cardápios ofertados em escolas públicas de um município rural do Nordeste brasileiro, quanto à composição nutricional, custo com gêneros alimentícios, nível de adesão dos escolares às refeições oferecidas e atendimento às recomendações nutricionais do Programa Nacional de Alimentação Escolar. Foi desenvolvido estudo transversal, realizado com 473 escolares, em Nísia Floresta, município do Estado do Rio Grande do Norte. A frequência de consumo semanal da alimentação escolar foi analisado segundo o padrão adotado por Sturion et al., que classifica o nível de adesão em: efetiva (quatro a cinco dias), média (dois a três dias) e baixa (um dia). Analisou-se 64 preparações da alimentação escolar, eleitas de forma aleatória por conglomerado, avaliadas quanto à energia, macronutrientes e micronutrientes (vitaminas A e C, ferro, zinco, magnésio e cálcio). Utilizaram-se como parâmetros as recomendações nutricionais estabelecidas pelo programa (2009), para atender 20% das necessidades nutricionais diárias, considerando as faixas etárias de 6 a 10, 11 a 15 e 16 a 18 anos. Calculou-se o custo das preparações servidas com base na licitação realizada no município. A associação entre adesão e extratos etários foi investigada utilizando a análise de correlação. A energia oferecida pelos cardápios foi inferior a recomendação em até 50%. As refeições atingiram, em média, 249,34 kcal (±64,43). Observaram-se preparações com inadequação dos macronutrientes e micronutrientes, exceto para proteínas (102,3%) e lipídios (100,1%), na faixa etária ix de 6 a 10 anos. O custo das preparações foi R$ 0,53 (±0,16), sendo provenientes 56,6% de recursos federais e 43,4% da contrapartida municipal, com essencialidade de recursos municipais no provimento do custo. Quanto à adesão, 93,9% dos escolares informaram consumir os lanches. Para o nível de adesão, obtiveram-se: 67,2% efetiva, 21,8% média e 4,9% baixa. Foi encontrada associação significativa entre as variáveis adesão e idade (χ2 = 89,36; GL=6; P < 0,001), sendo a baixa adesão encontrada, sobretudo, na faixa de 16 aos 18 anos. Os cardápios ofertados não atingem as metas do Programa Nacional de Alimentação Escolar, favorecendo a insegurança alimentar, especialmente aos adolescentes. Portanto, há necessidade de reformulações, planejamento, e implantação de refeições diferenciadas e adequadas às distintas faixas e factíveis de execução

Freqüência e etiologia das dermatomicoses em pacientes atendidos no Hospital Giselda Trigueiro, Natal, RN

Dermatomycoses are fungal infections that attack the skin, hair and nails, in addition to the mucosal and cutaneous-mucosal zones. Objective: Observe the frequency of dermatomycoses, identify etiological agents and establish an association between the results and sex. Age, collection site, time and lesion location. Methods: Between February, 2002 and December, 2004, samples were collected from patients at Giselda Trigueiro Hospital in Natal, Brazil, by lesion scraping and hair removal, following 70% alcohol disinfection, and submitted to direct and culture examination. Results: Of the 817 lesions collected, 325 (39.8%) were fungus positive, with the hair collection site yielding the highest number of positive results (65.8%) and the scalp and hair representing the most frequent lesion sites (65.9%). Negative results occurred mainly in the lower limbs (78.6%). Of the species identified, 55.9% were yeasts, 41.6% dermatophytes and 2.5% Fusarium spp. Non-albicans Candida was the most isolated yeast (43.3%), mainly in females (61.7%) over the age of 40 years (56.4%). T. rubrum was the most isolated dermatophyte (67.9%),notably in males (59.2%) in the 0-20 age group (44.7%). With respect to collection site, 73.9% of the dermatophytes were present in the skin and 61.1% of the yeasts in the nails. When assessing the collection site, the inguinocrural regional was 22.6% positive for dermatophytes, and the nails and hands, 41.8% for yeasts. Conclusions: The results obtained verified that: most of the positive lesions were found in the hair, whereas skin and nail lesions yielded more negative results; T. rubrum was the most isolated dermatophyte and non-albicans candida the most commonly found yeast; positivity was greater in males in the 0-20 year age group at the skin site and in the inguinocrural region, while yeasts were more frequent in females in the over-40 age group at the nail sites

Eça de Queiroz e a cozinha burguesa: literatura e alimentação

Using literature to discuss the topic of food, proper bourgeois cuisine, was the purpose of this work. As a corpus, we use one of the works of Eça de Queiroz, The City and the Mountains. Served as theoretical references the Claude Levi-Strauss s concept of universal culinary and the Jean Claude Fischler s concept of specific culinary who understands food as a cultural system which includes representations, beliefs and practices of a specific group. After the initial reading of the novel and construction of a file containing general information of the work, categories designed for elaboration of a material for analysis were these: work, characters, food, intellectuals and geographies. We realized the culinary as an epicenter for understanding the culture of a specific group: in this case, the bourgeois. We proposed a quaternary model for systematizing it: this bourgeois cuisine highlights the technique, has affection for what is rare and/or expensive but still consume it with temperance, establishing a new relationship with the use of time and, finally, it is the one that opens the ritual that involves frequent restaurants and cafes. The exercise of thinking the bourgeois cuisine through the literature suggests that the art may work on increase the comprehensive capabilities of nutritionists, professionals who deal with a complex object in your practice: the food

O concreto e o simbólico no cotidiano da educação em saúde: práticas, representações e processo identitário dos agentes comunitários de saúde de João Pessoa PB

The present study is about an etnographic research based on the Theory of Social Representation and its complementary approach, the Theory of Central Core based on the bourdiesianos concepts of field and habitus , concerning that these concepts, articulated to the constructed social representation, may contribute to the study of social identities. Its aim is to acknowledge which identity references community health agents (CHA), agents from Community Health Agent Program (CHAP) and Family Health Program (FHP) from João Pessoa PB and which social representation is constructed by them towards health education. The study had the participation of 119 CHAs, from which 90,3 % were female and 9,7% were male. Since the identity is also built by the representation of others towards the group, 63 professionals of the FHP group (16 nurses, 16 nursing assistents, 12 doctors, 9 dentists, 6 dentistry office assistents, 4 coordinators, 1 psicologist and 1 receptionist) and 1 nurse from CHAP took part of the study, oficial documents from the Health Ministry were analyzed, verbal information from its representatives were also taken into consideration, as well as reports from the many benefitiaries of the CHA, CHAP and FHP. For data collecting, we used the combination of (a) Direct Observation and Participant Observation of the functioning micro-areas of the CHA at the Family Health Units, and the Union of the Agents; (b) Free-Association of words and expressions to stimulate the CHA , Health Education and Health ; (c) Questionnaire; (d) Interviews. The interviews were submitted to a thematic analysis of its topic. The free-association was analyzed taking in consideration the vèrgesiana proposal (a combination of the frequency and average order of evocation) which treatment enabled the identification of the central and peripheral systems of social representation towards health education and the community health agent. A test of central refutation, associated to the analysis of the indicated evocations as the most important, provided empirical evidence of social representation towards health education as orientation , prevention and hygiene , as well as the identity of CHA as supervisor , friend , help , important , and the link between the community and the Family Health Staff. Other professionals from CHAP, FHP and the Health Ministry share all of these representational contents, especially the concepts of friend and link , also shared by the community. A habitus towards the community health agents was identified, as a representation based on trust and friendship, which gives the professional a great importance towards the daily inconsistencies faced by the community

Processo de alimentação do Sistema de Informação do HiperDia: Estudo de Caso no município de Natal/RN

Although the records indicate the involvement of the City Christmas in the feeding system HiperDia, a survey conducted by the Health Ministry in 2004 found that the number of entries made in Natal was well below estimate. In order to understand the functioning of HiperDia, we performed this study to analyze the actions taken by the professionals involved in power system HiperDia in Natal / RN. The research has developed into a quantitative perspective, with the design of exploratory case study conducted in the health services that integrate the various levels of the organization who are directly involved with the process of system power HiperDia in Natal / RN , represented here by SMS, health districts and the Family Health Units in the period from August to October 2008.Study participants were 110 professionals, including nurses, physicians, operators, administrator and a coordinator. The survey results showed that feeding HiperDia in Natal was maintained mainly by health professionals and operators. Activities include carrying out the state registration, monitoring, and updating of data transfer routines. They report that the difficulties in the process of feeding data are related to the work of teams and / or lack of structure of the Program of Hypertension and Diabetes (HA and DM), the discontinuity of federal investments in improving the HiperDia and lack of training. We can see then that the process of feeding system on Christmas HiperDia therefore is developing the three levels (SMS, districts and health units), however is not matching the expectations established by MS, considering that the gaps the flow of information are undermining the end result of this process

Conversor CC/CA de alta freqüência baseado em inversores ressonantes com comutação seqüencial para excitação de uma tocha indutiva a plasma térmico

This work describes the study, the analysis, the project methodology and the constructive details of a high frequency DC/AC resonant series converter using sequential commutation techniques for the excitation of an inductive coupled thermal plasma torch. The aim of this thesis is to show the new modulation technique potentialities and to present a technological option for the high-frequency electronic power converters development. The resonant converter operates at 50 kW output power under a 400 kHz frequency and it is constituted by inverter cells using ultra-fast IGBT devices. In order to minimize the turn-off losses, the inverter cells operates in a ZVS mode referred by a modified PLL loop that maintains this condition stable, despite the load variations. The sequential pulse gating command strategy used it allows to operate the IGBT devices on its maximum power limits using the derating and destressing current scheme, as well as it propitiates a frequency multiplication of the inverters set. The output converter is connected to a series resonant circuit constituted by the applicator ICTP torch, a compensation capacitor and an impedance matching RF transformer. At the final, are presented the experimental results and the many tests achieved in laboratory as form to validate the proposed new technique

Análise de superfícies seletivas de freqüência para aplicações em ondas milimétricas

This work consists in the development of a theoretical and numerical analysis for frequency selective surfaces (FSS) structures with conducting patch elements, such as rectangular patches, thin dipoles and cross dipoles, on anisotropic dielectric substrates. The analysis is developed for millimeter wave band applications. The analytical formulation is developed in the spectral domain, by using a rigorous technique known as equivalent transmission line method, or immitance approach. The numerical analysis is completed through the use of the Galerkin's technique in the Fourier transform domain, using entire-domain basis functions. In the last decades, several sophisticated analytical techniques have been developed for FSS structure applications. Within these applications, it can be emphasized the use of FSS structures on reflecting antennas and bandpass radomes. In the analysis, the scattered fields of the FSS geometry are related to the surface induced currents on the conducting patches. After the formulation of the scattering problem, the numerical solution is obtained by using the moment method. The choice of the basis functions plays a very important role in the numerical efficiency of the numerical method, once they should provide a very good approximation to the real current distributions on the FSS analyzed structure. Thereafter, the dyadic Green's function components are obtained in order to evaluate the basis functions unknown coefficients. To accomplish that, the Galerkin's numerical technique is used. Completing the formulation, the incident fields are determined through the incident potential, and as a consequence the FSS transmission and reflection characteristics are determined, as function of the resonant frequency and structural parameters. The main objective of this work was to analyze FSS structures with conducting patch elements, such as thin dipoles, cross dipoles and rectangular patches, on anisotropic dielectric substrates, for high frequency applications. Therefore, numerical results for the FSS structure main characteristics were obtained in the millimeter wave bando Some of these FSS characteristics are the resonant