932 research outputs found

    Analysis and implementation of the Buck-Boost Modified Series Forward converter applied to photovoltaic systems

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    The mismatching phenomenon is one of the main issues in photovoltaic (PV) applications. It could reduce the generated power of a string when a PV panel has different performances from the other PV panels connected to the same string. Distributed Maximum Power Point Tracking (DMPPT) architectures are one of the most promising solutions to overcome the drawbacks associated with mismatching phenomena in PV applications. In this kind of architectures, a DC-DC module integrated converter (MIC) manages each PV panel, isolating it from the rest of the PV panels, for harvesting the maximum available power from the Sun. Due to the high number of DCDC converters used in a grid-tied PV installation, the most desired MIC requirements are high efficiency, low cost and the capability of voltage step-up and step-down. This paper proposes the Buck-Boost Modified Forward (BBMSF) converter as a good candidate to be applied in DMPPT architectures. A complete analysis of the BBMSF converter is carried out, including the steady-state analysis as well as the small signal analysis in continuous conduction mode. The main advantages of the BBMSF converter are its step-up and step-down voltage transfer function; a higher simplicity, since it only includes a single controlled switch; the soft switching characteristics in all the diodes and MOSFET, reaching in some cases ZVS and ZCS, and yielding high efficiencies; the use of an autotransformer, with better performances than a typical Forward transformer; and the good dynamic performance, like the Forward converter ones. The theoretical analyses are validated through the experimental results in a 225 W BBMSF prototype designed and built under the requirements of a 100 kW grid-tied PV installation, achieving an efficiency up to 93.6%.This work has been supported by the Ministry of Economy and Competitiveness and FEDER funds through the research project "Storage and Energy Management for Hybrid Electric Vehicles based on Fuel Cell, Battery and Supercapacitors" - ELECTRICAR-AG- (DPI2014-53685-C2-1-R)

    Analysis, design, and implementation of the AFZ converter applied to photovoltaic systems

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    Grid-tied photovoltaic (PV) installations with Distributed Maximum Power Point Tracking (DMPPT) architectures include a DC-DC Module Integrated Converter (MIC) for managing each PV panel, isolating it from the others, reducing the mismatching effect and maximizing the harvested power. In this paper, the Autotransformer Forward converter with type-Zeta resonant reset (AFZ) is proposed as a DMPPT architecture’s MIC candidate. The main characteristics of the AFZ converter are the high versatility due to its voltage step-up and step-down capability; the use of an optimized autotransformer with only two windings, reducing the complexity and power losses of this component; the good dynamic performances, like the Forward converter ones; the low number of components and the simplicity and high feasibility associated to the use of just one active switch. Besides, soft switching transitions are achieved thanks to the autotransformer type-Zeta resonant reset. The steady-state theoretical analysis, considering the effect of the autotransformer leakage inductance, is presented. The converter is also studied in the frequency domain, obtaining the small-signal transfer functions. A design procedure based on the requirements of a 100 kW grid-tied photovoltaic installation is described, yielding in a 225 W prototype with efficiencies up to 95.6 %. Experimental results validate the theoretical analysis.This work was supported in part by the Spanish Ministry of Economy and Competitiveness and FEDER funds through the research project “Storage and Energy Management for Hybrid Electric Vehicles based on Fuel Cell, Battery and Supercapacitors” ELECTRICAR-AG under Grant DPI2014-53685-C2-1-R, in part by the research project CONEXPOT under Grant DPI2017-84572-C2-2-R, and in part by the research project EPIIOT under Grant DPI2017-88062-R

    Analysis and implementation of the autotransformer forward-flyback converter applied to photovoltaic systems

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    The Distributed Maximum Power Point Tracking (DMPPT) architecture is employed to overcome the mismatching phenomena in grid-tied photovoltaic (PV) installations. In this kind of architecture, a DC-DC module integrated converter (MIC) manages each PV panel. Thanks to the DC-DC converters, the differences between PV panels do not influence others, maximizing the amount of harvested power. The MIC requirements to make this kind of solutions profitable are voltage step-down and step-up capability, low cost and high efficiency. This paper analyses the Autotransformer Forward-Flyback (AFF) converter. This converter is considered as a MIC candidate for fulfilling the requirements above. The study of the AFF converter includes the steady-state analysis and the small signal analysis in continuous conduction mode. The advantages of the AFF converter are the capability of voltage step-down and step-up; the simplicity since it only includes a single controlled switch; the use of an autotransformer; good dynamic performances and the soft switching characteristics in all the diodes. The paper includes a detailed AFF converter step-by-step design procedure, applied to 100 kW grid-tied PV installation, in which the effect of shadows has been considered. A 225 W AFF converter prototype validates the theoretical analyses, achieving an efficiency up to 94.5%.This work has been supported by the Ministry of Economy and Competitiveness and FEDER funds through the research project "Storage and Energy Management for Hybrid Electric Vehicles based on Fuel Cell, Battery and Supercapacitors" - ELECTRICAR-AG- (DPI2014-53685-C2-1-R

    Comparative Study of Infliximab Versus Adalimumab in Refractory Uveitis Due to Behçet's Disease: National Multicenter Study of 177 Cases

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    Objective: To compare the efficacy of infliximab (IFX) versus adalimumab (ADA) as a first-line biologic drug over 1 year of treatment in a large series of patients with refractory uveitis due to Behçet's disease (BD). Methods: We conducted an open-label multicenter study of IFX versus ADA for BD-related uveitis refractory to conventional nonbiologic treatment. IFX or ADA was chosen as the first-line biologic agent based on physician and patient agreement. Patients received 3-5 mg/kg intravenous IFX at 0, 2, and 6 weeks and every 4-8 weeks thereafter, or 40 mg subcutaneous ADA every other week without a loading dose. Ocular parameters were compared between the 2 groups. Results: The study included 177 patients (316 affected eyes), of whom 103 received IFX and 74 received ADA. There were no significant baseline differences between treatment groups in main demographic features, previous therapy, or ocular sign severity. After 1 year of therapy, we observed an improvement in all ocular parameters in both groups. However, patients receiving ADA had significantly better outcomes in some parameters, including improvement in anterior chamber inflammation (92.31% versus 78.18% for IFX; P = 0.06), improvement in vitritis (93.33% versus 78.95% for IFX; P = 0.04), and best-corrected visual acuity (mean ± SD 0.81 ± 0.26 versus 0.67 ± 0.34 for IFX; P = 0.001). A nonsignificant difference was seen for macular thickness (mean ± SD 250.62 ± 36.85 for ADA versus 264.89 ± 59.74 for IFX; P = 0.15), and improvement in retinal vasculitis was similar between the 2 groups (95% for ADA versus 97% for IFX; P = 0.28). The drug retention rate was higher in the ADA group (95.24% versus 84.95% for IFX; P = 0.042). Conclusion: Although both IFX and ADA are efficacious in refractory BD-related uveitis, ADA appears to be associated with better outcomes than IFX after 1 year of follow-up

    Task-induced deactivation from rest extends beyond the default mode brain network

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    Activity decreases, or deactivations, of midline and parietal cortical brain regions are routinely observed in human functional neuroimaging studies that compare periods of task-based cognitive performance with passive states, such as rest. It is now widely held that such task-induced deactivations index a highly organized"default-mode network" (DMN): a large-scale brain system whose discovery has had broad implications in the study of human brain function and behavior. In this work, we show that common task-induced deactivations from rest also occur outside of the DMN as a function of increased task demand. Fifty healthy adult subjects performed two distinct functional magnetic resonance imaging tasks that were designed to reliably map deactivations from a resting baseline. As primary findings, increases in task demand consistently modulated the regional anatomy of DMN deactivation. At high levels of task demand, robust deactivation was observed in non-DMN regions, most notably, the posterior insular cortex. Deactivation of this region was directly implicated in a performance-based analysis of experienced task difficulty. Together, these findings suggest that task-induced deactivations from rest are not limited to the DMN and extend to brain regions typically associated with integrative sensory and interoceptive processes

    Percepción del personal de enfermería ante la rotación en los servicios de hospitalización

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    Objetivo. Determinar la percepción del personal de enfermería ante la rotación en los servicios de hospitalización en una institución de salud de cuarto nivel. Materiales y Métodos. La presente investigación es de carácter cuantitativo de tipo descriptivo de corte transversal, se trabajó con una muestra de 142 profesionales y auxiliares de enfermería que cumplieron los criterios de inclusión; para la recolección de la información se utilizó el instrumento actitud del personal de enfermería ante el proceso administrativo de rotación por los servicios hospitalarios. Resultados. Los sentimientos negativos que surgieron de la encuesta realizada al personal de enfermería fue la ansiedad con un 26%, contrario a esto  el personal identifica ventajas  con  la rotación que  permiten el crecimiento profesional, no interfiere en la relación enfermera-paciente, mejora su experiencia y genera nuevas habilidades. Conclusión. El personal de enfermería percibe que rotar por otro servicio genera experiencias para el fortalecimiento de la profesión situación, así mismo la rotación, es considerada una forma de adquirir nuevas habilidades y destrezas, que probablemente en el servicio donde se esté actualmente no se generen.PALABRAS CLAVE: Personal de enfermería, ansiedad, motivación, relaciones enfermero-paciente.Perception of nurses to the rotation in patient services ABSTRACTObjective: Determine the perception of nurses to the rotation in patient services in a fourth level health institution. Materials and Methods: This is a quantitative descriptive cross-sectional research, we worked with a sample of 142 professionals and nursing assistants who met the inclusion criteria; for data collection was used an attitude of nurse’s instrument face to the administrative process of rotation for hospital services. Results: Negative feelings that emerged from the survey nurses anxiety was 26%, contrary to this the staff identifies advantages with the rotation that allow professional growth, does not interfere in the nurse-patient relationship, improve your experience and generates new skills. Conclusion. Nurses perceived that to rotate by another service generates experiences to strength the status profession, likewise rotation, is considered a way to acquire new skills, probably in the service where it is currently not generated. KEYWORDS: Nurse, anxiety, motivation, nurse-patient relationships. Percepção de enfermeiros para os serviços de internamento rotação RESUMOObjetivo: Determinar a percepção de enfermeiros para os serviços de internamento de rotação em um quarto nível instituição de saúde. Materiais e Métodos: Esta pesquisa é de natureza quantitativa transversal descritivo, trabalhamos com uma amostra de 142 profissionais e auxiliares de enfermagem que preencheram os critérios de inclusão; para coleta de dados atitude instrumento de enfermeiros foi utilizado no processo administrativo de rotação dos serviços hospitalares. Resultados: Os sentimentos negativos que surgiram a partir da ansiedade enfermeiros da pesquisa foi de 26%, contrariamente a essa rotação de pessoal identifica vantagens que permitem o crescimento profissional, não interfere na relação enfermeiro-paciente, melhorar a sua experiência e gera novas habilidades. Conclusão: Enfermeiros percebidos a rodar por outro serviço gera experiências para fortalecer a profissão de status, de igual modo rotação, é considerado uma forma de adquirir novas habilidades, provavelmente no serviço em que actualmente não é gerado. PALAVRAS-CHAVE: relações enfermeiros, ansiedade, motivação, enfermeiro-paciente.

    Neural correlates of moral sensitivity in obsessive-compulsive disorder

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    Context: heightened moral sensitivity seems to characterize patients with obsessive-compulsive disorder (OCD). Recent advances in social cognitive neuroscience suggest that a compelling relationship may exist between this disorder-relevant processing bias and the functional activity of brain regions implicated in OCD. Objective: to test the hypothesis that patients with OCD demonstrate an increased response of relevant ventromedial prefrontal and orbitofrontal cortex regions in a functional magnetic resonance imaging study of difficult moral decision making. Design: case-control cross-sectional study. Setting: hospital referral OCD unit and magnetic resonance imaging facility. Participants: seventy-three patients with OCD (42 men and 31 women) and 73 control participants matched for age, sex, and education level. Main outcome measures: functional magnetic resonance imaging activation maps representing significant changes in blood oxygenation level-dependent signal in response to 24 hypothetical moral dilemma vs nondilemma task vignettes and additional activation maps representing significant linear associations between patients' brain responses and symptom severity ratings. Results: in both groups, moral dilemma led to robust activation of frontal and temporoparietal brain regions. Supporting predictions, patients with OCD demonstrated significantly increased activation of the ventral frontal cortex, particularly of the medial orbitofrontal cortex. In addition, the left dorsolateral prefrontal cortex and left middle temporal gyrus were more robustly activated in patients with OCD. These results were unexplained by group differences in comorbid affective symptoms. Patients' global illness severity predicted the relative magnitude of orbitofrontal-striatal activation. The severity of 'harm/checking' symptoms and 'sexual/religious' obsessions predicted the magnitude of posterior temporal and amygdala-paralimbic activation, respectively. Conclusions: the neural correlates of moral sensitivity in patients with OCD partly coincide with brain regions that are of general interest to pathophysiologic models of this disorder. In particular, these findings suggest that the orbitofrontal cortex together with the left dorsolateral prefrontal cortex may be relevant for understanding the link between neurobiological processes and certain maladaptive cognitions in OCD

    Anti-TNF-a therapy in patients with refractory uveitis due to Behçet's disease: a 1-year follow-up study of 124 patients

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    Objective: The aim of this study was to assess the efficacy of anti-TNF-α therapy in refractory uveitis due to Behçet's disease (BD). Methods: We performed a multicentre study of 124 patients with BD uveitis refractory to conventional treatment including high-dose corticosteroids and at least one standard immunosuppressive agent. Patients were treated for at least 12 months with infliximab (IFX) (3-5 mg/kg at 0, 2 and 6 weeks and then every 4-8 weeks) or adalimumab (ADA) (usually 40 mg every 2 weeks). The main outcome measures were degree of anterior and posterior chamber inflammation, visual acuity, macular thickness and immunosuppression load. Results: Sixty-eight men and 56 women (221 affected eyes) were studied. The mean age was 38.6 years (s.d. 10.4). HLA-B51 was positive in 66.1% of patients and uveitis was bilateral in 78.2%. IFX was the first biologic agent in 77 cases (62%) and ADA was first in 47 (38%). In most cases anti-TNF-α drugs were used in combination with conventional immunosuppressive drugs. At the onset of anti-TNF-α therapy, anterior chamber and vitreous inflammation was observed in 57% and 64.4% of patients, respectively. In both conditions the damage decreased significantly after 1 year. At baseline, 50 patients (80 eyes) had macular thickening [optical coherence tomography (OCT) >250 μm] and 35 (49 eyes) had cystoid macular oedema (OCT>300 μm) that improved from 420 μm (s.d. 119.5) at baseline to 271 μm (s.d. 45.6) at month 12 (P < 0.01). The best-corrected visual acuity and the suppression load also showed significant improvement. After 1 year of follow-up, 67.7% of patients were inactive. Biologic therapy was well tolerated in most cases. Conclusion: Anti-TNF-α therapy is effective and relatively safe in refractory BD uveitis.This work was partially supported by the RETICS Program [RD12/0009/0013 (RIER)] from the Instituto de Salud Carlos III (ISCIII), Madrid, Spain.Medicin
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