This paper shows that versatile stand-alone photovoltaic (PV) systems still demand on at least one battery inverter with improved characteristics of robustness and efficiency, which can be achieved using multilevel topologies. A compilation of the most common topologies of multilevel converters is presented, and it shows which ones are best suitable to implement inverters for stand-alone applications in the range of a few kilowatts. As an example, a prototype of 3 kVA was implemented, and peak efficiency of 96.0% was achieved.Index Terms-Multilevel inverter, renewable energy (RE), stand-alone photovoltaic (PV) system.

This study presents the analysis, design and experimental evaluation of a high-voltage gain dc-dc converter applied to photovoltaic (PV) systems. A PV module rated at 17 V is connected to the input side, whereas the converter is responsible for stepping the voltage up to 311 V with the achievement of maximum power point tracking (MPPT). An experimental prototype rated at 100 W is implemented, which does not employ electrolytic capacitors, thus increasing the useful life of the arrangement and also allowing the incorporation of the converter to the PV module. Prominent advantages of the topology are low cost and simplicity in terms of the MPPT algorithm and the system implementation, which are mandatory characteristics for renewable energy applications.

Introduction Odontoid diameter in some individuals may not be large enough to accommodate two 3.5-mm cortical screws for anterior odontoid fracture fixation. The study was performed to evaluate, in a Brazilian population, the diameter of the odontoid process and the feasibility of using two 3.5-mm cortical screws for anterior odontoid fracture fixation. Materials and methods Computed tomographic (CT) scans of 88 adult patients (aged 18-78 years) were analyzed; 40 patients (45%) were male (mean age: 43.08 years) and 48 (55%) were female (mean age: 43.39 years). The minimum external and internal anteroposterior and transverse diameters of the odontoid process on sagittal and coronal planes were measured on CT multiplanar reconstructions of the cervical spine. Results The mean value of the minimum external anteroposterior diameter was 10.83 ± 1.08 and 7.53 ± 1.10 mm for the minimum internal anteroposterior diameter. The mean value of the minimum external transverse diameter was 9.19 ± 0.91 and 6.07 ± 1.08 mm for the minimum internal transverse diameter. The mean AP diameter was significantly larger than the mean transverse diameter; 57 (65%) individuals had the minimum external transverse diameter [9.0 mm that would allow the insertion of two 3.5-mm cortical screws with tapping, and five (6%) individuals had the minimum internal transverse diameter [8.0 mm that would allow the insertion of two 3.5-mm cortical screws without tapping. Conclusions The insertion of two 3.5-mm cortical screws was possible for anterior fixation of odontoid fracture in 57 (65%) individuals of our study, and there was no statistical difference between males and females.

OBJETIVO: avaliação epidemiológica de pacientes com diagnóstico de lesão medular internados para reabilitação na enfermaria do Centro de Reabilitação e Readaptação Dr. Henrique Santillo (CRER) em Goiânia, Goiás. MÉTODOS: estudo epidemiológico retrospectivo baseado na coleta de dados dos prontuários médicos dos pacientes internados no período de Março de 2007 a Março de 2009. RESULTADOS: foram avaliados 208 pacientes, com predomínio do sexo masculino (78,85%) e idade média de 35,3 anos. O déficit neurológico mais prevalente foi paraplegia (64,90%), sendo 54,33% dos pacientes classificados como ASIA A (lesão completa) de acordo com a classificação da American Spinal Injury Association (ASIA). O tempo médio de lesão até a admissão no CRER foi de 129,7 dias, e o tempo médio de internação para reabilitação destes pacientes foi de 44,9 dias. A principal etiologia da lesão medular foi traumática, sendo 44,70% representadas por acidente de trânsito. A complicação mais comum na internação foi infecção do trato urinário. CONCLUSÃO: os dados epidemiológicos de pacientes com lesão medular, admitidos no CRER para reabilitação, se mostraram em conformidade com dados já descritos na literatura, demonstrando cada vez mais a importância da divulgação e realização de campanhas de prevenção do trauma raquimedular. Assim como a necessidade do encaminhamento precoce destes pacientes ao centro de reabilitação, uma vez que a grande maioria é jovem, com sequelas neurológicas graves e altamente incapacitantes.

This paper presents a design, mathematical modeling, simulation results and laboratory implementation of a 300W high gain dc-dc boost converter with a coupled inductor, to step up the 24V of a battery bank to 311Vdc, aiming to supply residential loads with dc voltage in an off-grid PV system. The converter can supply most of the residential ac loads which input stage is a single-phase rectifier. Laboratory tests with the 300W converter supplying electronic lights, mobile charger and audio-video system ac showed the viability of the proposed idea.