10 research outputs found

    Energy-efficient and Power-dense DC-DC Converters in Data Center and Electric Vehicle Applications Using Wide Bandgap Devices

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    The ever increasing demands in the energy conversion market propel power converters towards high efficiency and high power density. With fast development of data processing capability in the data center, the server will include more processors, memories, chipsets and hard drives than ever, which requires more efficient and compact power converters. Meanwhile, the energy-efficient and power-dense converters for the electric vehicle also result in longer driving range as well as more passengers and cargo capacities. DC-DC converters are indispensable power stages for both applications. In order to address the efficiency and density requirements of the DC-DC converters in these applications, several related research topics are discussed in this dissertation. For the DC-DC converter in the data center application, a LLC resonant converter based on the newly emerged GaN devices is developed to improve the efficiency over the traditional Si-based converter. The relationship between the critical device parameters and converter loss is established. A new perspective of extra winding loss due to the asymmetrical primary and secondary side current in LLC resonant converter is proposed. The extra winding loss is related to the critical device parameters as well. The GaN device benefits on device loss and transformer winding loss is analyzed. An improved LLC resonant converter design method considering the device loss and transformer winding loss is proposed. For the DC-DC converter in the electric vehicle application, an integrated DC-DC converter that combines the on-board charger DC-DC converter and drivetrain DC-DC converter is developed. The integrated DC-DC converter is considered to operate in different modes. The existing dual active bridge (DAB) DC-DC converter originally designed for the charger is proposed to operate in the drivetrain mode to improve the efficiency at the light load and high voltage step-up ratio conditions of the traditional drivetrain DC-DC converter. Design method and loss model are proposed for the integrated converter in the drivetrain mode. A scaled-down integrated DC-DC converter prototype is developed to verify the design and loss model

    Very High Frequency Galvanic Isolated Offline Power Supply

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    High Efficiency High Density 1 MHz 380–12 V DCX With Low FoM Devices

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    Controlled coupling of semiconductor quantum dots to optical micro-cavities

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    Propagation management for no-acknowledge HF communications links

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    The problems in the engineering of no-acknowledge HF links are reviewed with particular application to naval applications. Models for predicting the performance of the ionospheric path and techniques for measurement of channel quality are considered. Manual methods of propagation management are found to be limited by speed and accuracy in conducting measurements. Automation of the channel quality measurement process allowed observation of short term behaviour of the link for comparison with predictions. Long term behaviour tends toward the prediction but large deviations are found in the short term. Techniques for improving the estimates of the remote ionosphere were investigated. Updating predictions using a derived ionospheric index and the use of a backscatter sounder were attempted with limited success. Concepts for improvement in no-acknowledge links include networking between transmitting stations, modulation diversity and coding techniques, and development of 'intelligent receiving terminals with facilities for rapid selection of operating channels and overcoming unwanted signal interference. Recommendations for further work to investigate these concepts is presented

    NASA Tech Briefs, August 1996

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    Topics covered include: Graphics and Simulation; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Report

    Safety and Reliability - Safe Societies in a Changing World

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    The contributions cover a wide range of methodologies and application areas for safety and reliability that contribute to safe societies in a changing world. These methodologies and applications include: - foundations of risk and reliability assessment and management - mathematical methods in reliability and safety - risk assessment - risk management - system reliability - uncertainty analysis - digitalization and big data - prognostics and system health management - occupational safety - accident and incident modeling - maintenance modeling and applications - simulation for safety and reliability analysis - dynamic risk and barrier management - organizational factors and safety culture - human factors and human reliability - resilience engineering - structural reliability - natural hazards - security - economic analysis in risk managemen

    X Congreso Ibérico de Agroingeniería = X Congresso Ibérico de Agroengenharia : Libro de actas = Livro de atas

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    In 2017, the Food and Agriculture Organization (FAO) issued a report on the challenges that Agriculture is facing and will face into the 21st century, which can be summarized in one question: will we be able to sustainably and effectively feed everyone by 2050 and beyond, while meeting the additional demand for agricultural commodities due to non- food uses? Agricultural engineers can contribute in this process by releasing the biological and technical constraints on crop and animal productivity, reducing the contribution of the agricultural sector to environmental degradation, and enabling agricultural practices to adapt to environmental changes. To achieve optimal results for agribusiness and the society, the expertise of agricultural engineers must be integrated with expertise from other sciences: breakthrough technologies are needed for agricultural enterprises to meet the increasing list of standards and norms in the areas of energy, animal welfare, product quality, water, and volatile emissions. Recognition of trends in society and networking and participation in debates have thus become important activities for agricultural engineers. The Iberian Agroengineering Congress series brings together Spanish and Portuguese engineers, researchers, educators and practitioners to present and discuss innovations, trends, and solutions to the aforementioned challenges in the interdisciplinary field of Agricultural and Biosystems Engineering. This biennial congress, jointly organized by the Spanish Society of Agroengineering and the Specialized Section of Rural Engineering of the Sociedade de Ciências Agrárias de Portugal, has proven to be an excellent opportunity to network and discuss future developments. In its 10th edition, the Congress has been held from 3-6 September in Huesca (Spain), at the Escuela Politécnica Superior, located on the Huesca Campus of the University of Zaragoza. The topics of the Congress have included the main areas of Agricultural Engineering: mechanization; soils and water; animal production technology and aquaculture; rural constructions; energy; information technologies and process control; projects, environment, and territory; postharvest technology; and educational innovation in agroengineering. The Congress has received 123 participants, who have submitted 144 papers, 86 oral communications and 58 poster. 22 universities, 4 research centers and 8 companies/professional associations have been represented. The quality of the papers presented to the congress is endorsed not only by the long trajectory of the Iberian Agroengineering Congress, but also by the edition of a Special Issue of Agronomy journal (ISSN 2073-4395) entitled “Selected Papers form 10th Iberian Agroengineering Congress”
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