Search

A family of double conversion three-phase uninterruptible power system with power factor correction and high-frequency transformer (HFT) isolation topologies is presented in this work. This might be an alternative compared to large conventional UPS systems that are based in bulky transformers that operates in the grid frequency. These systems are suitable for operation with line-to-line input voltages equal to 220-V or 380-V. For both input voltages, the proposed converter has almost the same efficiency processing the same output power. The three-phase HFT UPS used for further analysis is composed by single-phase chopper modules, one three-phase boost module, and one three-phase inverter. The relevant features are soft commutation of the controlled switches in the chopper stage, simple control strategy that can be implemented with well-known integrated circuits (IC), and the use of few batteries in series due to the same reference of the step-up stages. Principle of operation of the chosen system for experimental validation, implemented control strategy and experimental results obtained for a 15kVA prototype are presented.

In 1950 on Mount Zlatý kůň (‘Golden Horse’) in modern-day Czech Republic a system of caves was discovered. During many years of research in this area, human and animal osteological remains have been excavated, among which the most interesting ones were nine fragments of a female skull, now dated to ca. 43,000 yrs BP which are one of the earliest known anatomically modern humans in Eurasia. The aim of this research was to use purely digital techniques to: (1) to reconstruct the skull based on the 3D data of preserved fragments, (2) to approximate the probable appearance of the female it belonged to, and (3) to analyze the calculated shape of the reconstructed mandible and volume of the neurocranium in the context of similarities and differences with other representatives of the genus Homo. Computer techniques used in this research constitute a new, original approach to the problem of 3D analyses and may be useful primarily in bioarchaeological sciences, where metric analyses of the most valuable bone artifacts are often severely limited due to the incompleteness of the material available for research. The digital techniques presented here may also contribute significantly to the field of surgery, with the possibility of being adapted for applications in cranial prosthetics and post-traumatic reconstructive surgery.

RESUMO: A formação de cientistas é um investimento social de longo prazo, que colabora com a sociedade a partir da construção de conhecimentos científicos que podem ser aplicados na resolução de problemas urgentes. Formar cientistas exige que sejam mobilizadas variadas cadeias de atores sociais, não obstante, a literatura científica nos apresenta diversos relatos de experiência em todo o mundo e nas mais diferentes instituições, que auxiliam no desenvolvimento e na reflexão acerca da formação de cientistas. O presente estudo tem como objetivo analisar as principais estratégias de formação de cientistas apresentadas em tal literatura. Foi realizada uma revisão integrativa da literatura entre os anos de 2003 e 2022, acerca da formação de cientistas, identificando e compreendendo as experiências de formação de cientistas relatadas pelas autorias. Como resultado, as experiências de formação interdisciplinar, capacitação metodológica, internacionalização da formação, as atividades de gestão educacional e a curricularização da divulgação científica são apontadas como práticas formativas salutares a cientistas em formação.

The End of White World Supremacy: Black Internationalism and the Problem of the Color Line. by Roderick D. Bush. Philadelphia: Temple University Press, 2009. 258 pp. Barack Obama's historic election [...]

Abstract This article presents the development of a liquid-level sensor using fiber optic Bragg gratings (FBG). The sensor comprises a carbon-fiber-reinforced polymers (CFRP) diaphragm packaging an embedded FBG to measure strain. A mathematical analysis determines the FBG response to the pressure exerted by a liquid column over the packaged sensor. The experimental arrangement consists of an acrylic tube with a sensor at the bottom. FBG signals were acquired using a DI 410 optical interrogator manufactured by HBM. A finite element simulation with Ansys was performed to determine the most reposeful position from the FBG sensor. The experimental results show the analysis of eight repetitions of the water column ranging from 10 cm to 60 cm using 10 cm steps. The sensor showed a linear response, with a coefficient of determination of 0.999, and a sensitivity of 4.1 pm/cm; and the maximum standard deviation is 0.64 pm. Although water is used in the calibration process, other liquids could also be used, obtaining a different angular coefficient depending on the density of the liquid used.

Abstract The use of digital technologies in archaeological research has become considerably more widespread in recent years. While the earliest records of the use of electronic data in archaeology date from the 1950 and 1960s, the field has kept growing with the increasing interest in digital tools such as digital photography, three-dimensional imaging, GIS, virtual and artificial reality applications, CAD and facial reconstruction. Such digitization practices are used frequently for documenting, record keeping, and preserving and representing the data recovered from archaeological contexts, and are linked to other fields, such as cultural heritage studies and museology. Facial reconstruction is used to recreate the faces of individual from the past using their skeletal remains. It has been practiced for different reasons in the fields of forensics, anthropology, and archaeology. This study focuses on the facial reconstruction of a skull unearthed from Juliopolis. The reason for choosing this skull in this study is that it is the first and only known deformed skull dated to the Roman period in Anatolia. For the facial reconstruction application, authors created a 3D modelling of the skull by photogrammetry. Then, the missing parts of the skull are completed using the virtual donor library. The results are presented in different forms, as grayscale, in colour with eyes closed or open. Also, the type of deformation is demonstrated in the skull. This study adopts a digital process and is more strongly linked to data interpolation related to the external surface of the face. The prominent advantage of the methodology is being strongly supported by information obtained from computed tomography (CT) scans of living individuals, leaving a little room for the artistic issue in relation to the basic aspect resulting from the interpolation of data. The benefit of facial reconstruction is especially important since it is a way of preserving and presenting archaeological and anthropological data.

Introdução: O período de pandemia da COVID-19 trouxe uma série de alterações na rotina de estudantes universitários que apresenta elevado potencial de modificar os seus hábitos alimentares. Objetivo: Realizar uma revisão integrativa a respeito do consumo alimentar de universitários durante o período da pandemia da COVID-19. Materiais e Métodos: Para o levantamento dos dados foi adotada uma adaptação da estratégia PICO, artigos de março de 2020 a janeiro de 2023 das bases de dados da MEDLINE/PUBMED, LILACS, BVS e Google Scholar. Foram utilizados os seguintes descritores: “Consumo de Alimentos”, “Estudantes”, “Pandemia”, “Coronavírus”, “Eating”, “COVID-19”, “Pandemics”, “Students”, combinados entre si através do operador booleano “AND”. Resultados e Discussão: Ao final da seleção dos artigos, 10 compuseram esta revisão de literatura. O consumo alimentar de estudantes universitários brasileiros foi modificado durante o período da pandemia da COVID-19, tendo sido observado um aumento do consumo de alimentos processados/industrializados, fast food, açúcares simples, alimentos ricos em gorduras e uma diminuição do consumo de alimentos in natura, frutas e vegetais. Conclusão: Fatores característicos do período de pandemia, como isolamento social, sedentarismo, alta carga de estresse, ensino remoto emergencial e uso de aplicativos de delivery parecem ter contribuído negativamente na mudança de hábitos, diminuindo a qualidade da alimentação.

Over the past decade, distributed acoustic sensing has been utilized for structural health monitoring in various applications, owing to its continuous measurement capability in both time and space and its ability to deliver extensive data on the conditions of large structures using just a single optical cable. This work aims to evaluate the performance of distributed acoustic sensing for monitoring a multilayer structure on a laboratory scale. The proposed structure comprises four layers: a medium-density fiberboard and three rigid polyurethane foam slabs. Three different damages were emulated in the structure: two in the first layer of rigid polyurethane foam and another in the medium-density fiberboard layer. The results include the detection of the mechanical wave, comparing the response with point sensors used for reference, and evaluating how the measured signal behaves in time and frequency in the face of different damages in the multilayer structure. The tests demonstrate that evaluating signals in both time and frequency domains presents different characteristics for each condition analyzed. The supervised support vector machine classifier was used to automate the classification of these damages, achieving an accuracy of 93%. The combination of distributed acoustic sensing with this learning algorithm creates the condition for developing a smart tool for monitoring multilayer structures.

Abstract Here, we performed a systematic DFT study assisted by the workflow framework SimStack for the mechanical and thermodynamic properties of the clay mineral lizardite in pristine and six different types of O vacancies configurations. In most cases, the defect caused a structural phase transition in the lizardite from the trigonal (pristine) to the triclinic phase. The results show that oxygen vacancies in lizardite significantly reduce the lattice thermal conductivity, accompanied by an elastic moduli reduction and an anisotropy index increase. Through the P–V relation, an increase in compressibility was evidenced for vacancy configurations. Except for the vacancy with the same crystalline structure as pristine lizardite, the sound velocities of the other vacancy configurations produce a decrease in these velocities, and it is essential to highlight high values for the Grüneisen parameter. We emphasize the great relevance of the punctual-defects introduction, such as O vacancies, in lizardite, since this microstructural design is responsible for the decrease of the lattice thermal conductivity in comparison with the pristine system by decreasing the heat transfer ability, turning lizardite into a promising candidate for thermoelectric materials