2,047 research outputs found

    Graduate Catalog of Studies, 2023-2024

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    Graduate Catalog of Studies, 2023-2024

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    Undergraduate Catalog of Studies, 2022-2023

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    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    A survey on reconfigurable intelligent surfaces: wireless communication perspective

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    Using reconfigurable intelligent surfaces (RISs) to improve the coverage and the data rate of future wireless networks is a viable option. These surfaces are constituted of a significant number of passive and nearly passive components that interact with incident signals in a smart way, such as by reflecting them, to increase the wireless system's performance as a result of which the notion of a smart radio environment comes to fruition. In this survey, a study review of RIS-assisted wireless communication is supplied starting with the principles of RIS which include the hardware architecture, the control mechanisms, and the discussions of previously held views about the channel model and pathloss; then the performance analysis considering different performance parameters, analytical approaches and metrics are presented to describe the RIS-assisted wireless network performance improvements. Despite its enormous promise, RIS confronts new hurdles in integrating into wireless networks efficiently due to its passive nature. Consequently, the channel estimation for, both full and nearly passive RIS and the RIS deployments are compared under various wireless communication models and for single and multi-users. Lastly, the challenges and potential future study areas for the RIS aided wireless communication systems are proposed

    Digital materials design of solid oxide fuel cell anodes

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    This PhD-Thesis was presented to the Faculty of Science and Medicine of the University of Fribourg (Switzerland) in consideration for the award of the academic grade of Doctor of Philosophy in Physics (Thesis No: 5369). The doctorate was mainly pursued at the Institute of Computational Physics ICP at Zurich University of Applied Sciences ZHAW in Winterthur, Switzerland PhD Presentation: https://zhaw.mediaspace.cast.switch.ch/mediashare/d430305eb29a01af/media/t/0_8py1hjfn GeoDict User Meeting 2021 Presentation: https://www.youtube.com/watch?v=AIROVKq5yocThe storage and efficient conversion of energy is one of the key issues for a successful transition to renewable energies. Solid oxide cell (SOC) technology is a promising solution for the conversion of electrical energy to storable chemical energy (power-to-gas) in the solid oxide electrolysis cell (SOEC) mode, and for the on-demand supply of electrical energy using synthetic gas or biogas (or natural gas) as input in the solid oxide fuel cell (SOFC) mode. To significantly improve on the unavoidable degradation of state-of-the-art anodes like Ni-YSZ, we elaborate on new nickel-free electrode concepts, which are based on mixed ionic and electronic conductors (MIEC) like doped ceria and perovskite (e.g., titanate) materials. However, the anode performance is governed by complex physico-chemical processes including transport of gas in the pores, transport of ions and electrons in both solid phases and fuel oxidation reaction on the surface of the MIECs, which are not yet fully understood. Hence, there are numerous conflicting requirements and lack of knowledge complicating the development and optimization process. These challenges are addressed in this thesis in two ways. First, a Digital Materials Design (DMD) framework for the systematic and model-based optimization of MIEC SOC-electrodes is elaborated. In our DMD approach we combine stochastic microstructure modeling, virtual testing of 3D microstructures and a multiscale-multiphysics electrode model to explore the available design space by performing parametric studies. The basis for the DMD process is a set of fabricated solid oxide cells. Their real microstructures are reconstructed using FIB-SEM tomography. Stochastic digital microstructure twins with matching microstructure properties are then constructed for each real structure using a pluri-Gaussian method. On that basis, the microstructure can be virtually varied for a large parameter space in a realistic way. The real and subsequently the virtual 3D structures need to be characterized quantitatively by means of image analysis and numerical simulations. Hence, a standardized and automated microstructure characterization has been developed, which enables the fast determination of an extensive set of microstructure properties relevant for SOC electrodes. Moreover, specific microstructure properties like the ‘composite conductivity’ crucial for novel composite MIEC electrodes are introduced and discussed. A multiphysics continuum simulation model is then used to predict the impact of the microstructure variation on the electrode performance, using the previously determined microstructure properties as an input. In addition, the kinetic reaction parameters of the model are calibrated to the experimental performance characterizations of the cells (e.g., EIS results). This model-based performance prediction enables to establish the relationship between materials choices and compositions, fabrication parameters, microstructure properties and cell-performance. Due to the integration of stochastic modeling (pluri-Gaussian method) and its combination with automated characterization and model-based performance prediction, the number of the involved 3D microstructures can be significantly increased. This approach is thus capable to explore a much larger design space than it would be possible with experimental methods only. On this basis, design guidelines for the fabrication of electrodes with improved performances can be provided, which closes the loop of this iterative workflow. This DMD workflow is made available for the research community by the release of two software apps for the standardized microstructure characterization and stochastic microstructure modeling for SOC electrodes. Detailed information on these methodologies is also provided by the corresponding publications. Second, this DMD workflow is applied for the optimization of titanate based LSCT-CGO SOFC-anodes with a noble metal catalyst impregnation. Based on the performance and microstructure characterization of fabricated cells, several DMD studies are performed. Thereof, design guidelines for titanate-CGO anodes are provided including different microstructure design concepts and parameter specifications like appropriate material compositions and porosity. Moreover, the new opportunities as well as the current limitations of these nickel-free electrodes are discussed in great detail

    CMFRI Annual Report 2022 केंद्रीय समुद्री मात्स्यिकी अनुसंधान संस्थान वार्षिक प्रतिवेदन 2022

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    In 2022, the total marine fish landings along the coast of India’s mainland were approximately 3.49 million tonnes, indicating a 14.53% increase compared to 2021. The year saw a significant rise of 28.02% in fish landings compared to the pandemic-affected year of 2020. However, despite these improvements, the 2022 estimate was 2.0% lower than the pre-COVID year of 2019. Among the coastal states, Tamil Nadu secured the highest position with 7.22 lakh tonnes of fish landings, followed by Karnataka with 6.95 lakh tonnes and Kerala with 6.87 lakh tonnes. Gujarat, which had previously held the top rankings, dropped to fourth place with 5.03 lakh tonnes. These four states, namely Tamil Nadu, Karnataka, Kerala, and Gujarat accounted for 20.69%, 19.90%, 19.68%, and 14.40% of the national total, respectively. Except for Odisha and Gujarat, all states witnessed an increase in fish landings compared to 2021

    Efficiency and Sustainability of the Distributed Renewable Hybrid Power Systems Based on the Energy Internet, Blockchain Technology and Smart Contracts-Volume II

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    The climate changes that are becoming visible today are a challenge for the global research community. In this context, renewable energy sources, fuel cell systems, and other energy generating sources must be optimally combined and connected to the grid system using advanced energy transaction methods. As this reprint presents the latest solutions in the implementation of fuel cell and renewable energy in mobile and stationary applications, such as hybrid and microgrid power systems based on the Energy Internet, Blockchain technology, and smart contracts, we hope that they will be of interest to readers working in the related fields mentioned above
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