1,721,058 research outputs found
Wave energy converter: a brief review of WECs technology and some aspects of oscillating wave column converter design
No full textOcean waves are a huge, largely unexploited energy resource, and the potential for extracting energy from waves is great. Research in this area is driven by the need to meet renewable energy targets, but is relatively immature compared to other renewable energy technologies.
This brief review introduces some device types that represent current wave energy converter (WEC) technology. The possible power take-off systems are identified.
The review is followed by a consideration of some of the design strategies to enhance the efficiency of an oscillating wave column-type WECs.
The considered oscillating wave column (OWC) is a relatively novel multi-chamber technology that need a lot of investigations, starting from fluid-dynamic, up to power electric converter
Finite element modeling and characterization of lead-free solder joints fatigue life during power cycling of surface mounting power devices
No full textIn this work it is developed a numerical model for thermo-mechanical fatigue of SMD chip solder joints in power converters that can be useful for reliability prediction. By this model the thermo-mechanical stress–strain distribution in the structure is studied by means of Finite Elements (FE) method and operational life of the solder joints can be calculated.
As a case study the estimation of the fatigue life of lead-free solder joints in SO8-packaged power MOSFETs is investigated. A stress bench for power cycling was set up to tune the developed FE model by experimental results and dynamic thermal measurements are reported. Results obtained by either simply applying the Coffin–Manson law or also accounting for creep, depending on cycle period, are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Temperature-dependent reverse-bias stress of normally-off GaN power FETs
No full textWe show results of temperature-dependent reverse-bias step-stressing of normally-off high-power GaN
FETs. In the range 250–350 K, the stress voltage at which the FETs fail catastrophically does not show a
clear temperature dependence, while some correlation is observed with the initial leakage current value.
Our results, consistent with other published reports, point to the activation of a deep gate-to-drain leakage
path as the responsible for fatal device degradation at large values of the drain–gate reverse bias
Parallel-connected bidirectional converters for avionic applications
No full textThis paper proposes a fully FPGA controlled Bi-Directional Converter (BDC) for avionic applications. The dissertation starts with an overview of the proposed converter, followed by the description and the mathematical analysis of the Dual Active Bridge (DAB) topology. Then, the control laws for both single and parallel modes are presented. In particular, the discussion on the paralleling of power converters with current sharing is the main contribution of this study. Simulations and experimental evaluations that illustrate the behavior of the BDC unit are given throughout all the specific sections
Review of oscillating water column converters
Full text linkOcean waves are a huge, largely unexploited energy resource and the potential for extracting energy from waves is great. Research in this area is driven by the need to meet renewable energy targets, but it is relatively immature compared to other renewable energy technologies. This review introduces some device types that represent the state of the art of Oscillating Water Column (OWC) technology, a kind of Wave Energy Converter (WEC). Unlike other works in literature, typically limited to specific aspects of WECs, in this paper will be pursued a system wide perspective, from the sea waves to the grid connection
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Design aspects for a robust snubberless power converter with Si and SiC Power MOSFETs
No full textA number of harsh-environment high-reliability applications are undergoing substantial electrification. The converters operating in such systems need to be designed to meet both
stringent performance and reliability requirements. This work focuses on a dc-dc converter for novel avionic applications and considers both new semiconductor technologies and the
application of design techniques to ensure that robustness is maximized and stress levels minimized. In this respect, close attention is paid to the thermal management and an approach
for the heatsink design aided by finite element modeling is shown
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