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Correlation versus dissipation in a non-Hermitian Anderson impurity model

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Physical Review B 2025年第12期111卷 125157-125157页

作者： Kazuki Yamamoto Masaya Nakagawa Norio Kawakami Department of Physics Tokyo Institute of Technology Meguro Tokyo 152-8551 Japan Department of Physics University of Tokyo Hongo Tokyo 113-0033 Japan Fundamental Quantum Science Program TRIP Headquarters RIKEN Wako 351-0198 Japan Department of Physics Ritsumeikan University Kusatsu Shiga 525-8577 Japan Department of Materials Engineering Science Osaka University Toyonaka Osaka 560-8531 Japan

We analyze the competition between strong correlations and dissipation in quantum impurity systems from the Kondo regime to the valence fluctuation regime by developing a slave-boson theory for a non-Hermitian Anderson impurity model with one-body loss. Notably, in the non-Hermitian Kondo regime, strong correlations qualitatively change the nature of dissipation through renormalization effects, where the effective one-body loss is suppressed and emergent many-body dissipation characterized by the complex-valued hybridization is generated. We unveil the mechanism of a dissipative quantum phase transition of the Kondo state on the basis of this renormalization effect, which counterintuitively enhances the lifetime of the impurity against loss. We also find a crossover from the non-Hermitian Kondo regime to the valence fluctuation regime dominated by one-body dissipation. Our results can be tested in a wide variety of setups such as quantum dots coupled to electronic leads and quantum point contacts in ultracold Fermi gases.

关键词： Bosons

Rational Self-Supported Electrode Design with Optimized Ion Migration and Gas Diffusion for Efficient Anion Exchange Membrane Water Electrolyzer

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SSRN 2024年

作者： Ning, Minghui Wang, Yu Wu, Libo Zhang, Fanghao Yuan, Chuqing Song, Shaowei Yu, Luo Wang, Dezhi Chen, Shuo Ren, Zhifeng University of Houston HoustonTX77204 United States Materials Science and Engineering Program and TcSUH University of Houston HoustonTX77204 United States Department of Chemistry and TcSUH University of Houston HoustonTX77204 United States

The ion migration and gas diffusion are two of the most critical topics in water electrolysis. Many self-supported electrodes (SSEs) exhibit efficient performance in fundamental research studies due to their excellent gas diffusion. However, such performance is not guaranteed in large-scale electrolyzers due to the extremely large ion migration resistance of these SSEs. Here we find that a commercial SSE (Ni foam) exhibits efficient performance in fundamental research but performs poorly in an anion exchange membrane water electrolyzer (AEMWE). Further investigations reveal that the poor performance of the AEMWE originates from the large ion migration resistance caused by the long OH− migration distance within the SSE. After its design is optimized to minimize the ion migration resistance and enhance gas diffusion efficiency, the AEMWE is found to deliver a current density of 1 A/cm2 at 1.778 V in 1 M KOH at 65 °C. A triple-cell stack is further assembled and found to reach 1 A/cm2 at 5.464 V and to exhibit excellent stability over 216 h in 1 M KOH. © 2024, The Authors. All rights reserved.

关键词： Potassium hydroxide

An Economical and Efficient Helium Recovery System for Vibration-Sensitive Applications

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arXiv

arXiv 2024年

作者： Yin, Zhiyuan Bi, Liya Shi, Yueqing Li, Shaowei Department of Chemistry and Biochemistry University of California La Jolla San DiegoCA92093-0309 United States Program in Materials Science and Engineering University of California La Jolla San DiegoCA92093-0418 United States

We present the design of a helium liquefaction system tailored to efficiently recover helium vapor from either an individual or a small cluster of vibration-sensitive cryogenic instruments. This design prioritizes a compact footprint, mitigating potential contamination sources such as gas bags and oil-lubricated compressors while maximizing the recovery rate by capturing both the boil-offs during normal operation and refilling process of the bath cryostat. We demonstrated its performance by applying it to a commercial low-temperature scanning probe microscope. It features a > 94% recovery rate and induces negligible vibrational noise to the microscope. Due to its adaptability, affordability, compact size, and suitability for homemade setups, we foresee that our design can be utilized across a wide range of experimental measurements where liquid helium is used as the cryogen. © 2024, CC BY.

关键词： Gas compressors

Biodegradable Pbat/Pla Blend Films Incorporated with Turmeric and Cinnamomum Powder: A Potential Alternative for Active Food Packaging

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SSRN 2023年

作者： de Castro, Layara L.R.L. Abreu, Iago R. Braz, Cristiano J.F. Rodrigues, Samara C.S. dos Araújo, Regilda S.R.M. Folkersma, Rudy de Carvalho, Laura H. Barbosa, Renata Alves, Tatianny S. Graduate Program in Materials Science and Engineering Federal University of Piauí Teresina64.049-550 Brazil Department of Physics Federal Institute of Education Science and Technology of Piauí Teresina Central Campus Teresina64.000-040 Brazil Department of Nutrition Federal University of Piauí Teresina64.049-550 Brazil NHL Stenden University of Applied Sciences Groningen9727 Netherlands Graduate Program in Materials Science and Engineering Federal University of Campina Grande PI TeresinaCEP: 58.100-000 Brazil

Active packaging made from biodegradable polymers and natural additives appears as an ecological alternative. In addition to having antioxidant activity and enhancing food preservation, it allows mitigating the negative impacts caused by improper disposal. This study pursued to produce biodegradable films based on a polymer blend PBAT/PLA (Ecovio®) using the flat extrusion method. The films were prepared with the incorporation of 5 wt% of powdered turmeric or cinnamon as natural additives. The films obtained, and those reprocessed twice, were characterized in terms of colorimetric, UV light transmittance, water contact angle, water vapor permeability, morphology, mechanical properties, and antioxidant activity. Cinnamon reduced the UV light transmittance and made a surface more hydrophobic. Reprocessing led to greater elongation and maximum load, associated with increased dispersion and distribution, as evidenced in the morphological analysis. The films developed have significant potential for applications in active food packaging, with emphasis on cinnamon-additivated films. © 2023, The Authors. All rights reserved.

关键词： Biodegradable polymers

Experimental Validation of Full Geometry MCNP Model of the UFTR based on NAA

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Experimental Validation of Full Geometry MCNP Model of the U...

2020 IEEE Nuclear science Symposium and Medical Imaging Conference, NSS/MIC 2020

作者： Woldegiorgis, Surafel Nimmagadda, Jyothier Baciak, James The Nuclear Engineering Program The Department of Materials Science and Engineering The University of Florida GainesvilleFL32603 United States

ISBN: (纸本)9781728176932

The energy spectrum and spatial distribution of the neutron beam from a reactor is an essential component of designing experimentations utilizing the reactor as a radiation source. Obtaining such information requires the use of detailed MCNP model of the reactor and experimental validation procedures. After updating the MCNP model of the University of Florida Training Reactor (UFTR) to align it with the current core arrangement that uses low enriched uranium (LEU), both the radial neutron flux toward the beam ports and the energy spectrum at the reactor core were generated using the model. This was followed by experimental validations based on neutron activation analysis (NAA) by irradiating multiple activation foils. A constant ratio between MCNP and measured neutron flux values was obtained at multiple locations along the reactor's beam ports, showing that the model captures the spatial distribution of neutron flux profiles without a significant systematic error. The energy spectrum at the core was extracted using the Unfolding with MAXED and GRAVEL (UMG) software. The spectrum unfolded by both MAXED and GRAVEL algorithms display features expected in thermal reactor neutron energy distribution, i.e., thermal, fast or fission, and intermediate or slowing down regions. The thermal and epithermal neutron fluxes at the reactor core calculated from the spectrum unfolded by the MAXED n algorithm are 1. 56 ± 0. 12 × 1012 cm2s and 1. 98 ± 0. 01 × 1012 n sm2s, whereas the corresponding values calculated from the spectrum unfolded by the GRAVEL algorithm are 1. 50 ± 0. 12 × n 1012 n and 3. 74 ± 0. 21 × 1012. Following the cm2s cm2s experimental validation, the full geometry MCNP model of the reactor has been utilized for a neutron tomography research project and it will continue to benefit future projects using the reactor facility. © 2020 IEEE

关键词： Neutron flux

Porous Mesh Manifold for Enhanced Pool Boiling Performance

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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

High performance electronics are continuously demanding cooling of higher heat fluxes. Phase change cooling, including pool boiling, is a useful approach to address this challenge, however competition between liquid and vapor flows generally limit the heat fluxes that can be dissipated. Here a manifold structure formed from metallic mesh is introduced to control the disposition of liquid and vapor phases above a boiling surface enhanced with a porous structure. Copper mesh forms defined liquid flow paths using capillary action to guide and distribute liquid evenly over the heated surface and open channels to facilitate vapor escape. The manifold performance is characterized in pool boiling with water above a laser textured aluminum nitride heat dissipation surface with pin fin structures having heights of 110 µm and spacing of 30 µm with a heated area of 5 mm x 5 mm. Maximum heat flux of 490W/cm is reached with the manifold in the pool boiling configuration, representing a 64% increase over the porous surface alone. Maximum superheat found for the manifold is 36 K, which is 14 K higher than the porous surface without manifold. Factors limiting performance of the manifold are analyzed. Based on variation of manifold geometry and numerical simulation, the primary limitation to heat flux is found to be viscous resistance to liquid flow in the manifold mesh. The increased superheat is attributed to partial flooding of the boiling surface as indicated by reduction in superheat using external suction. Similar systems and structures for enhanced two-phase cooling are compared. © 2024, The Authors. All rights reserved.

关键词： Heat flux

Experimental Investigation and Validation of Strength-Based Topology and Fiber Path Optimization in Continuous Fiber Reinforced Composites

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SSRN 2024年

作者： Yap, Timothy He, Zhelong Wang, Zhichao Tamijani, Ali Tehrani, Mehran Department of Structural Engineering University of California San Diego La Jolla CA92093 United States Program in Materials Science and Engineering University of California San Diego La Jolla CA92093 United States State-Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University Changsha410082 China

Material Extrusion (ME) based Fused Filament Fabrication (FFF) excels with Continuous Carbon Fiber (CCF) reinforced filaments. This Additive Manufacturing (AM) technology allows for intricate parts to be made with topologies where fibers are aligned in directions that optimize strength and stiffness, albeit within certain manufacturing limitations. This study investigates the performance of strength-based optimization methods applied to two benchmark structural domains and loading scenarios. Two methods were used to concurrently design the topology and fiber paths: shape optimization using the level-set method, and topology optimization using both density-based Solid Orthotropic Material with Penalization (SOMP) and level-set methods. CCF filaments were printed to follow the post-processed fiber paths, and a discontinuous fiber reinforced filament was used to fill in the remaining gaps. The parts were then compression molded for full consolidation, followed by testing for their stiffness and strengths (failure loads). Finite Element Analysis (FEA) was used to simulate the stiffness and failures of the tested parts. FEA predicted stiffnesses, locations of failure, and failure loads with reasonable accuracy (less than 10% difference with experiment). A micro-computed tomography (µCT) examination of failed coupons showed that fiber flow (deviation from printed paths) during compression molding was a major source of error. In one case, a progressive damage failure model performed more accurately than a linear static simulation. Finally, comparing designs optimized for stiffness versus strength showed premature failures due to stress concentrations in stiffness-optimized designs. This study underscores the critical need for integrating proper optimization strategy with realistic AM constraints to enhance the performance and reliability of CFF reinforced AM parts. © 2024, The Authors. All rights reserved.

关键词： Finite element method

Recent advance in synthesis and application of heteroatom zeolites

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Chinese Chemical Letters 2021年第1期32卷 328-338页

作者： Tingting Pang Xuanyu Yang Chenyi Yuan Ahmed A.Elzatahry Abdulaziz Alghamdi Xing He Xiaowei Cheng Yonghui Deng School of Materials Science and Engineering University of Shanghai for Science and TechnologyShanghai 200093China Department of Chemistry Shanghai Key Laboratory of Molecular Catalysis and Innovative MaterialsFudan UniversityShanghai 200433China Materials Science and Technology Program College of Arts and SciencesQatar UniversityP.O.Box 2713DohaQatar Department of Chemistry College of ScienceKing Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia State Key Lab of Transducer Technology Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050China

Incorporation of heteroatoms into the framewo rk of zeolites has become a significant strategy to improve their performance in catalysis and adsorption,because the obtained heteroatom zeolites exhibit quite different properties from the conventional aluminosilicate zeolites in aspects of surface acidity,pore structures,particle size and so *** this review,the progress on the heteroatom zeolites including their synthesis and application is ***,the recent advance on the design and synthesis of different heteroatom zeolites is *** emphasis is placed on the introduction and comparison of three typical methods,including the direct synthesis,post synthesis and improved direct synthesis,for the traditional heteroatom zeolites(such as TS-1,Sn-MFI,Sn-β) and newly-reported heteroatom zeolites(such as W-MFI,Mo-MFI).According to their intrinsic characteristics,the application of heteroatom zeolites in diverse fields,such as production of fine chemicals,air pollution control and biomass conversion is then ***,the challenges and perspective on the future development of heteroatom zeolites in low-cost preparation and practical application are proposed.

关键词： Heteroatom zeolite Incorporation Tetrahedral coordination Research status Synthesis Application Prospective

Laser Processed Aluminum Nitride Structures for Enhanced Two-Phase Cooling

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SSRN 2024年

作者： Giglio, Roman Shattique, Muhammad Rubaiet Md. Dede, Ercan M. Narumanchi, Sreekant Asheghi, Mehdi Goodson, Kenneth E. Palko, James W. Department of Mechanical Engineering University of California MercedCA United States Materials and Biomaterials Science and Engineering Graduate Program University of California MercedCA United States Toyota Research Institute of North America Ann ArborMI United States National Renewable Energy Laboratory GoldenCO United States Department of Mechanical Engineering Stanford University StanfordCA United States

The demand for higher heat flux cooling is increasing as the use of power electronics continues to expand. Two-phase cooling approaches that are tightly integrated into electronic packages offer potential for high performance. Here we describe a method to produce microscale pillars directly in aluminum nitride using UV laser ablation that is compatible with existing substrates for power electronics packaging and offers high precision and short production time. The resulting structures show significantly enhanced performance in pool boiling compared to unmodified surfaces. Effectiveness in two-phase cooling is investigated in terms of critical heat flux, heat transfer coefficient, and thermal resistance. The micropillar structures achieve a maximum critical heat flux of 299 W/cm2 and heat transfer coefficients up to 20 W/cm2 K for cooled areas of 0.25 cm2 in deionized water. Performance is attributed to the effective capillary rewetting of the surface during boiling and increased surface area. Corrosion of the aluminum nitride surface by the water working fluid is observed and contributes to a slow degradation of the measured heat transfer coefficient. The potential for simple processing routes to allow tight integration of two-phase cooling of electronics more generally is considered. © 2024, The Authors. All rights reserved.

关键词： Heat flux