A 5GHz/1.8V CMOS Active Balun Integrated with LNA

The development of high performance monolithic RF front-ends requires innovative RF circuit design to make the best of a good technology. A fully differential approach is usually preferred, due to its well-known properties. Although the differential approach must be preserved inside the chip, there are cases where the input signal is single-ended such as RF image filters and IF filters in a RF receiver. In these situations, a stage able to convert single-ended into differential signals (balun) is needed. The most cited topology, which is capable of providing high gain, consists on a differential stage with one of the two inputs grounded. Unfortunately, this solution has some drawbacks when implemented monolithically. This work presents the design and simulated results of an innovative high-performance monolithic single to differential converter, which overcomes the limitations of the circuits.The integration of the monolithic active balun circuit with an LNA on a 0.18μm CMOS process is also reported. The circuits presented here are aimed at 802.11a. Section 2 describes the balun circuit and section 3 presents its performance when it is connected to a conventional single-ended LNA. Section 4 shows the simulated performance results focused at phase/amplitude balance and noise figure. Finally, the last section draws conclusions and future work.

A 5GHz1.8V Low Power CMOS Low-Noise Amplifier

Wireless local-area networks (WLANs) have been deployed as office and home communications infrastructures worldwide. The diversification of the standards, such as IEEE 802.11 series demands the design of RF front-ends. Low power consumption is one of the most important design concerns in the application of those technologies. To maintain competitive hardware costs, CMOS has been used since it is the best solution for low cost and high integration processing, allowing analog circuits to be mixed with digital ones. In the receiver chain, the low noise amplifier (LNA) is one of the most critical blocks in a transceiver design. The sensitivity is mainly determined by the LNA noise figure and gain. It interfaces with the pre-select filter and the mixer. Furthermore, since it is the first gain stage, care must be taken to provide accurate input match, low-noise figure, good linearity and a sufficient gain over a wide band of operation. Several CMOS LNAs have been reported during the last decade, showing that the most research has been done at 802.11/b and GSM standards (900-2400MHz spectrum) and more recently at 802.11/a (5GHz band). One of the more significant disadvantages of 802.11/b is that the frequency band is crowded and subject to interference from other technologies, as is 2.4GHz cordless phones and Bluetooth. As the demand for radio-frequency integrated circuits, operating at higher frequency bands, increases, the IEEE 802.11/a standard becomes a very attractive option to wireless communication system developers. This paper presents the design and implementation of a low power, low noise amplifier aimed at IEEE 802.11a for WLAN applications. It was designed to be integrated with an active balun and mixer, representing the first step toward a fully integrated monolithic WLAN receiver. All the required circuits are integrated at the same die and are powered by 1.8V supply source. Preliminary experimental results (S-parameters) are shown and promise excellent results. The LNA circuit design details are illustrated in Section 2. Spectre simulation results focused at gain, noise figure (NF) and input/output matching are presented in Section 3. Finally, conclusions and comparison with other recently reported LNAs are made in Section 4, followed by future work.

A hybrid MLS technique for room impulse response estimation

The measurement of room impulse response (RIR) when there are high background noise levels frequently means one must deal with very low signal-to-noise ratios (SNR). if such is the case, the measurement might yield unreliable results, even when synchronous averaging techniques are used. Furthermore, if there are non-linearities in the apparatus or system time variances, the final SNR can be severely degraded. The test signals used in RIR measurement are often disturbed by non-stationary ambient noise components. A novel approach based on the energy analysis of ambient noise - both in the time and in frequency - was considered. A modified maximum length sequence (MLS) measurement technique. referred to herein as the hybrid MLS technique, was developed for use in room acoustics. The technique consists of reducing the noise energy of the captured sequences before applying the averaging technique in order to improve the overall SNRs and frequency response accuracy. Experiments were conducted under real conditions with different types of underlying ambient noises. Results are shown and discussed. Advantages and disadvantages of the hybrid MLS technique over standard MLS technique are evaluated and discussed. Our findings show that the new technique leads to a significant increase in the overall SNR. (C) 2008 Elsevier Ltd. All rights reserved.

O Contributo do controlo interno na gestão de recursos humanos – estudo de caso

Dissertação apresentada no Instituto Superior de Contabilidade e Administração do Porto para a obtenção do Grau de Mestre em Auditoria ORIENTADOR: DOUTORA MARIA CLARA DIAS PINTO RIBEIRO

Os suportes de expressão como veículos promotores de aprendizagens no Ensino Pré-Escolar e no 1.º ciclo do Ensino Básico

Mestrado (PES II), Educação Pré-Escolar e Ensino do 1.º Ciclo do Ensino Básico, 26 de Junho de 2014, Universidade dos Açores.

A questão da língua na União Europeia – implicações sobre a liberdade de circulação de mercadorias

Dissertação apresentada ao Instituto Superior de Contabilidade e Administração do Porto para a obtenção do Grau de Mestre em Empreendedorismo e Internacionalização Orientada pela Mestre Maria Luísa Verdelho Alves

Formaldeyde exposure during animal macroscopic examination

Results of research work developed in anatomy and pathology laboratories have indicated that “macroscopic examination” is the task involving the highest exposure to formaldehyde. This is probably because precision and very good visibility are needed and, therefore, pathologists must lean over the specimen with consequent increase of proximity. With this research we aimed to know formaldehyde exposure in case of animal’s macroscopic examination. Three macroscopic examinations were considered and exposure assessment performed with photo ionization detection (PID) direct-reading equipment (with an 11.7 eV lamp) designated by First-Check, from Ion Science. Higher values of formaldehyde concentration (ceiling values) were register in each exam.

Mutation accumulation in Tetrahymena

Background - The rate and fitness effects of mutations are key in understanding the evolution of every species. Traditionally, these parameters are estimated in mutation accumulation experiments where replicate lines are propagated in conditions that allow mutations to randomly accumulate without the purging effect of natural selection. These experiments have been performed with many model organisms but we still lack empirical estimates of the rate and effects of mutation in the protists. Results - We performed a mutation accumulation (MA) experiment in Tetrahymena thermophila, a species that can reproduce sexually and asexually in nature, and measured both the mean decline and variance increase in fitness of 20 lines. The results obtained with T. thermophila were compared with T. pyriformis that is an obligate asexual species. We show that MA lines of T. thermophila go to extinction at a rate of 1.25 clonal extinctions per bottleneck. In contrast, populations of T. pyriformis show a much higher resistance to extinction. Variation in gene copy number is likely to be a key factor in explaining these results, and indeed we show that T. pyriformis has a higher mean copy number per cell than T. thermophila. From fitness measurements during the MA experiment, we infer a rate of mutation to copy number variation of 0.0333 per haploid MAC genome of T. thermophila and a mean effect against copy number variation of 0.16. A strong effect of population size in the rate of fitness decline was also found, consistent with the increased power of natural selection. Conclusions - The rate of clonal extinction measured for T. thermophila is characteristic of a mutational degradation and suggests that this species must undergo sexual reproduction to avoid the deleterious effects detected in the laboratory experiments. We also suggest that an increase in chromosomal copy number associated with the phenotypic assortment of amitotic divisions can provide an alternative mechanism to escape the deleterious effect of random chromosomal copy number variation in species like T. pyriformis that lack the resetting mechanism of sexual reproduction. Our results are relevant to the understanding of cell line longevity and senescence in ciliates.

A relação terapeuta-cliente: na perspectiva do cliente

O presente estudo resulta de uma crescente preocupação e percepção da importância da relação terapeuta-cliente e procura compreender a perspectiva do cliente e a forma como este sente e vive essa relação ao longo de todo o seu processo terapêutico. O estudo realizado, de natureza qualitativa e de carácter exploratório, visa sobretudo analisar a influência da relação terapeuta-cliente na perspectiva do cliente, identificar e descrever os fatores que a influenciam e perceber a mais-valia desta relação ao longo do processo terapêutico. Para tal, foram entrevistadas dezanove pessoas que estão a receber tratamento de terapia ocupacional. Para a recolha dos dados foi aplicada a entrevista semi-estruturada por se pretender um contributo mais envolvente, particularizado e subjetivo dos clientes. Através da realização do estudo e de acordo com a perspetiva dos clientes entrevistados, concluiu-se que a capacidade do terapeuta em construir e estabelecer um vínculo com o cliente ditará grande parte do sucesso ou insucesso do processo terapêutico. Porém, tão importante como formar e estabelecer um vínculo terapeuta-cliente é preciso ter a preocupação contínua de o manter sempre vivo e fortalecido. Para que tal aconteça, o terapeuta não pode menosprezar a experiência de vida e expectativas do cliente e deve assumir um papel de permanente preocupação e atenção a todas as transformações quotidianas pois estas influenciam o envolvimento do cliente nas suas atividades/ocupações e afetam a sua saúde e desempenho. O novo milénio requer dos profissionais de saúde em geral e dos terapeutas ocupacionais em particular, novas habilidades e competências. É fundamental adquirir a consciência de que os clientes são o centro de todo o processo terapêutico. É necessário ter uma visão holística e não fragmentada do cliente. É importante interagir com os clientes e permitir uma troca de conhecimento, entre o saber do cliente e o saber do terapeuta. Essa troca gera convergências, fortalece laços e o processo terapêutico avança. Nesse relacionamento, ambos aprendem, progridem e crescem.

An adaptive educational system for higher education

The main objective of an Adaptive System is to adequate its relation with the user (content presentation, navigation, interface, etc.) according to a predefined but updatable model of the user that reflects his objectives, preferences, knowledge and competences [Brusilovsky, 2001], [De Bra, 2004]. For Educational Adaptive Systems, the emphasis is placed on the student knowledge in the domain application and learning style, to allow him to reach the learning objectives proposed for his training [Chepegin, 2004]. In Educational AHS, the User Model (UM), or Student Model, has increased relevance: when the student reaches the objectives of the course, the system must be able to readapt, for example, to his knowledge [Brusilovsky, 2001]. Learning Styles are understood as something that intent to define models of how given person learns. Generally it is understood that each person has a Learning Style different and preferred with the objective of achieving better results. Some case studies have proposed that teachers should assess the learning styles of their students and adapt their classroom and methods to best fit each student's learning style [Kolb, 2005], [Martins, 2008]. The learning process must take into consideration the individual cognitive and emotional parts of the student. In summary each Student is unique so the Student personal progress must be monitored and teaching shoul not be not generalized and repetitive [Jonassen, 1991], [Martins, 2008]. The aim of this paper is to present an Educational Adaptive Hypermedia Tool based on Progressive Assessment.

Resiliência em idosos viúvos

Dissertação de Mestrado em Gerontologia Social

O programa de formação contínua em matemática para professores do 1º ciclo e a melhoria do ensino da matemática

Neste artigo apresento uma análise do Programa de Formação Contínua em Matemática, que se desenvolveu em Portugal de 2005 a 2011. Começo por abordar a formação de professores que ensinam Matemática, tendo por base resultados da investigação que serviram de suporte para a definição do Programa de Formação Contínua em Matemática (PFCM). Serão depois analisados os dados do PFCM em termos do envolvimento dos professores do 1.º ciclo a quem ele se destinava. Faz-se uma avaliação da formação a partir de testemunhos dos formandos inseridos nos relatórios institucionais e/ou nos seus portefólios, para concluir que as características da formação foram determinantes para o aumento da confiança dos professores envolvidos e, em consequência, para a melhoria da aprendizagem da Matemática dos nossos alunos. Por fim, referem-se os resultados do TIMSS 2011, que vêm corroborar a afirmação feita anteriormente. Uma ideia forte que se transmite é a de que a formação contínua de professores tem de ter uma estreita ligação com a prática letiva

Melhoria do processo de fabrico de esterilizadores

Mestrado em Engenharia Mecânica. Gestão de Processos e Operações.

Potenciar a consciência fonológica de crianças pré-escolares em contexto naturalístico

Dissertação apresentada à Escola Superior de Educação de Lisboa para obtenção de grau de mestre em Ciências da Educação Especialidade Intervenção Precoce

Práticas curriculares em jardim de infância com crianças com perturbações do espetro do autismo

Dissertação apresentada à Escola Superior de Educação de Lisboa para obtenção do grau de Mestre em Educação - Especialização em Educação Especial