Browsing by Author "Amaral, Ana"
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- A CMOS micro power switched-capacitor DC-DC step-up converter for indoor light energy harvesting applicationsPublication . Carvalho, Carlos Manuel Ferreira; Lavareda, Guilherme; Amaral, Ana; Carvalho, Carlos Nunes de; Paulino, Nuno Filipe Silva VeríssimoThis paper presents a micro power light energy harvesting system for indoor environments. Light energy is collected by amorphous silicon photovoltaic (a-Si:H PV) cells, processed by a switched capacitor (SC) voltage doubler circuit with maximum power point tracking (MPPT), and finally stored in a large capacitor. The MPPT fractional open circuit voltage (V-OC) technique is implemented by an asynchronous state machine (ASM) that creates and dynamically adjusts the clock frequency of the step-up SC circuit, matching the input impedance of the SC circuit to the maximum power point condition of the PV cells. The ASM has a separate local power supply to make it robust against load variations. In order to reduce the area occupied by the SC circuit, while maintaining an acceptable efficiency value, the SC circuit uses MOSFET capacitors with a charge sharing scheme for the bottom plate parasitic capacitors. The circuit occupies an area of 0.31 mm(2) in a 130 nm CMOS technology. The system was designed in order to work under realistic indoor light intensities. Experimental results show that the proposed system, using PV cells with an area of 14 cm(2), is capable of starting-up from a 0 V condition, with an irradiance of only 0.32 W/m(2). After starting-up, the system requires an irradiance of only 0.18 W/m(2) (18 mu W/cm(2)) to remain operating. The ASM circuit can operate correctly using a local power supply voltage of 453 mV, dissipating only 0.085 mu W. These values are, to the best of the authors' knowledge, the lowest reported in the literature. The maximum efficiency of the SC converter is 70.3 % for an input power of 48 mu W, which is comparable with reported values from circuits operating at similar power levels.
- Conducting indium oxide films on plastic substrates by plasma enhanced reactive thermal evaporationPublication . Vygranenko, Yuri; Fernandes, Miguel; Vieira, Manuela; Lavareda, Guilherme; CARVALHO, CARLOS; Brogueira, P.; Amaral, AnaThis work reports on low temperature deposition of conducing indium oxide films by a radio-frequency plasma enhanced reactive thermal evaporation (rf-PERTE) technique. The films were deposited on polyethylene terephthalate (PET) without intentional heating of the substrate and at elevated temperatures up to 150 degrees C. The material stoichiometry was accurately controlled by adjusting deposition conditions including the oxygen flow, process pressure, pumping speed, and RF-power. Besides, fine turning of the critical deposition parameters during the deposition was implemented by measuring the variation of film conductance in-situ. The film morphology was analyzed by scanning electron microscopy. Hall effect measurements were also performed to determine the relation between the deposition conditions and the electrical properties of the films. A resistivity of 4 x 10(-4) Omega-cm was reached under optimized deposition conditions. A 250 nm-thick coating with 16 Omega/sq sheet resistance shows an 82% peak value of transmittance in the visible spectral range.
- Efeitos da fisioterapia no tratamento das disfunções sexuais femininas: revisão sistemáticaPublication . Amaral, Ana; Silva, Patrícia; Coutinho, Maria IsabelIntrodução: As disfunções sexuais femininas abrangem diversas perturbações que causam alterações no desejo, na excitação, no orgasmo e/ou dor. A fisioterapia parece ter um papel crucial no tratamento destas disfunções, existindo diversas intervenções consoante as necessidades apresentadas. Objetivo: Estudar as intervenções fisioterapêuticas realizadas em mulheres com disfunção sexual e os seus efeitos na sintomatologia e na qualidade de vida e averiguar que estudos futuros serão relevantes para a prática clínica baseada em evidência na fisioterapia na saúde da mulher. Métodos: A revisão sistemática foi realizada de acordo com o protocolo PRISMA. Realizaram-se pesquisas nas bases de dados PubMed, Scielo, ScienceDirect, LILACS, PEDro e Web of Science com as palavras-chave sexual dysfunctions, dyspareunia, vaginismus, female sexual dysfuncion, physical therapy e physiotherapy. Incluíram-se estudos randomizados controlados com amostra constituída por mulheres com disfunção sexual, escritos em inglês, português ou espanhol e excluíram-se estudos sem intervenção fisioterapêutica, sem descrição de resultados ou eficácia do tratamento e com valor na escala PEDro inferior a 4. Resultados: Dos artigos identificados, 14 foram incluídos com informação relevante, sobretudo, relativamente a perturbações de dor génito-pélvica ou na penetração, verificando-se uma carência na evidência das restantes perturbações. Os estudos incluídos nesta revisão abordaram a fisioterapia multimodal, o biofeedback eletromiográfico, as ondas de choque, a laserterapia de baixa intensidade e o TENS. Os protocolos usados nos diferentes estudos de fisioterapia multimodal variam amplamente, no entanto a terapia manual, o treino dos músculos do pavimento pélvico e o biofeedback foram as intervenções mais prevalentes. A fisioterapêutica multimodal, o TENS e as ondas de choque têm bons resultados na melhoria da sintomatologia e da qualidade de vida da mulher. Conclusão: Os resultados suportam a eficácia das modalidades de fisioterapia como primeira linha de tratamento de disfunções sexuais femininas (dor génito-pélvica ou na penetração) sendo que a fisioterapia multimodal aparenta ter melhores resultados na sintomatologia e qualidade de vida. São necessários mais estudos nesta área, com tamanhos de amostras maiores. Seria igualmente importante, realizar-se estudos nas restantes disfunções sexuais femininas, para que se compreenda o papel da fisioterapia dentro de uma equipa multidisciplinar.
- Etchability dependence of InOx and ITO thin films by plasma enhanced reactive termal evaporation on structural properties and deposition conditionsPublication . Amaral, Ana; Lavareda, Guilherme; Carvalho, Carlos Nunes de; Andre, Vania; Vygranenko, Yuri; Fernandes, Miguel; Brogueira, PedroIndium oxide (InOx) and indium tin oxide (ITO) thin films were deposited on glass substrates by plasma enhanced reactive thermal evaporation (PERTE) at different substrate temperatures. The films were then submitted to two etching solutions with different chemical reactivity: i) HNO3 (6%), at room temperature; ii) HCl (35%): (40 °Be) FeCl3 (1:1), at 40 °C. The dependence of the etchability of the films on the structural and deposition conditions is discussed. Previously to etching, structural characterization was made. X-ray diffraction showed the appearance of a peak around 2θ=31° as the deposition temperature increases from room temperature to 190 °C, both for ITO and InOx. AFM surface topography and SEM micrographs of the deposited films are consistent with the structural properties suggested by X-ray spectra: as the deposition temperature increases, the surface changes from a finely grained structure to a material with a larger-sized grain or/and agglomerate structure of the order of 250-300 nm. The roughness Rq varies from 0.74 nm for the amorphous tissue to a maximum of 10.83 nm for the sample with the biggest crystalline grains. Raman spectra are also presented.
- Photoconductivity kinetics of indium sulfofluoride thin films starPublication . Vygranenko, Yuri; Fernandes, Miguel; Vieira, Manuela; Lavareda, Guilherme; CARVALHO, CARLOS; Brogueira, Pedro; Amaral, AnaIndium sulfofluoride is an amorphous wide-gap semiconductor exhibiting high sensitivity to UV radiation. This work reports on the kinetics of photoconductivity in indium sulfofluoride thin films along with their electrical and optical properties. The films were deposited by radio-frequency plasma-enhanced reactive thermal evaporation. The film characterization includes electrical, optical, and photoconductivity measurements. The films are highly transparent in the visible-infrared range due to an indirect bandgap of 2.8 eV. The spectral response measurements have revealed existence of the band tail states. The synthesized compound is highly resistive (similar to 200 M ohm-cm at 300 K) and exhibits extremely slow photocurrent relaxations. Photoconductivity kinetics was studied under various excitation conditions. A dependence of the photocurrent on the incident photon flux was also determined.