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Non-Hermitian Delocalization in a Two-Dimensional Photonic Quasicrystal

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Physical Review Letters 2024年第26期132卷 263801-263801页

作者： Zhaoyang Zhang Shun Liang Ismaël Septembre Jiawei Yu Yongping Huang Maochang Liu Yanpeng Zhang Min Xiao Guillaume Malpuech Dmitry Solnyshkov Key Laboratory for Physical Electronics and Devices of the Ministry of Education & Shaanxi Key Lab of Information Photonic Technique School of Electronic Science and Engineering Faculty of Electronics and Information PHOTON-N2 Université Clermont Auvergne CNRS Clermont INP F-63000 Clermont-Ferrand France International Research Center for Renewable Energy and State Key Laboratory of Multiphase Flow in Power Engineering Department of Physics National Laboratory of Solid State Microstructures and School of Physics 75231 Paris France

Theoretical and experimental studies suggest that both Hermitian and non-Hermitian quasicrystals show localization due to the fractal spectrum and to the transition to diffusive bands via exceptional points, respectively. Here, we present an experimental study of a dodecagonal photonic quasicrystal based on electromagnetically induced transparency in a Rb vapor cell. First, we observe the suppression of the wave packet expansion in the Hermitian case. We then discover a new regime, where increasing the non-Hermiticity leads to delocalization, demonstrating that the behavior in non-Hermitian quasicrystals is richer than previously thought.

关键词： Electromagnetically induced transparency Localization Photonics Non-Hermitian systems Quasicrystals

Efficient Charge Transfer at the Donor-Bridge-Acceptor Interface for Excellent Supercapacitors

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SSRN 2023年

作者： Yin, Baoyi Hao, Liang Li, Xiaogan Yang, Qi-Guo Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China School of Microelectronics Dalian University of Technology Dalian116024 China

The intrinsic electrochemical activity and active sites of the battery-like electrode in supercapacitors originate from efficient charge transfer at the interface. A seamless all-carbon graphdiyne layer on CoNi2S4 yolk-shell spheres (CoNi2S4/GDY YSSs) provides a unique structure of a flawless "donor–bridge–acceptor" interface, where Ni atoms and Co atoms serve as electron donors and acceptors, respectively, connected by the sp-C–Ni and sp-C–Co bonds as bridges. Importantly, this particular can facilitate effective electron transfer from the Ni atoms to the Co atoms, resulting in more interfacial Co2+ active sites. Additionally, the seamless all-carbon graphdiyne layer greatly enhances the structural and interfacial stabilities of CoNi2S4 yolk-shell spheres, effectively avoiding structural deterioration. Profiting from its structural merits, the CoNi2S4/GDY YSSs electrode delivers a considerable capacitance of 856 C/g at 1 A/g, along with exceptional rate capability (61.9% for 50-fold current density increase). Furthermore, an asymmetric supercapacitor with the CoNi2S4/GDY YSSs electrode cathode achieves a remarkable maximum energy density of 91.7 Wh/kg at a power density of 793 W/kg. Furthermore, the strategy proposed in this study has the potential to open up new pathways for the battery-like electrode design with realistic supercapacitor applications. © 2023, The Authors. All rights reserved.

关键词： Charge transfer

Best estimate plus uncertainty analysis of the China advanced large-scale PWR during LBLOCA scenarios

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International Journal of Advanced Nuclear Reactor Design and Technology 2020年 2卷 34-42页

作者： Chang, Yuhao Wang, Mingjun Zhang, Jing Tian, Wenxi Qiu, Suizheng Su, G.H. Department of Nuclear Science and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

China advanced large-scale Pressurized Water Reactor (PWR) implements series of passive safety systems to provide core cooling and decay heat removal in case of some unexpected accidents. The development of reactor best estimate system analysis codes has realized the transition from conservative safety analysis to Best Estimate plus Uncertainty (BEPU) analysis for the purpose of achieving more realistic results and digging larger safety margins. The BEPU analysis during Large Break Loss of Coolant Accident (LBLOCA) has been widely used for the licensing application of Nuclear power Plants (NPPs). In this paper, the BEPU analysis of China advanced large-scale PWR was performed under the conditions of LBLOCA scenarios employing RELAP5 code. The models of reactor coolant system with all the passive safety systems were established and the influence of uncertainties of important parameters on the Peak Cladding Temperature (PCT) was evaluated. The results show the obtained PTC (1314 K) through the BEPU analysis is far below the 10CFR50.46 PCT acceptance criteria (1477 K) in case of LBLOCA and is also lower than the conservative calculation value (1348 K), indicating a larger safety margin. This work provides a meaningful evaluation method for China advanced large-scale PWR safety assessment. © 2020 Xi'an Jiaotong University

关键词： Pressurized water reactors

Evaluation of R513A as an environmentally friendly alternative to R134a in spray cooling for laser surgery: Heat transfer performance and optimization

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International Journal of Thermal Sciences 2025年 215卷

作者： He, Zhi-Zhong Lin, Xiang-Wei Li, Chen-Xi Kong, Chen Shen, Lin-Xin Zhou, Zhi-Fu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Shaanxi Xi'an710049 China School of Future Technology Xi'an Jiaotong University Shaanxi Xi'an710049 China Xi'an Jiaotong University Health Science Center Shaanxi Xi'an710049 China

Spray cooling plays a pivotal role in mitigating thermal injuries to the epidermis during laser surgery. However, the widespread use of R134a, a refrigerant with a high global warming potential (GWP) of 1300, poses significant environmental concerns. In this study, R513A, a more environmental-friendly cryogen with a GWP of 573, is used to investigate the feasibility of replacing R134a and the effects of spray height, spurt duration, nozzle orifice diameter, and spray pressure on R513A spray cooling through a self-built open-loop spray system. Experimental results demonstrate that R513A exhibits superior cooling performance, achieving a minimum surface temperature (Tmin) 12 °C lower and a maximum heat flux (qmax) 27.5 % higher than R134a. Additionally, R513A offers a broader optimal spray height range (30–50 mm) in which Tmin is 4 °C and 13 °C lower than those at 20 mm and 10 mm, respectively. qmax in this range is 10 % and 16 % higher than those at 20 mm and 10 mm, respectively. While extending the spurt duration consumes more cryogen and prolongs the liquid film lifetime, the differences in Tmin and qmax are less than 4 °C and 10 kW/m2. With the nozzle orifice increasing from 0.6 mm to 1.0 mm, Tmin remains approximately −42 °C but qmax gradually increases by 6 kW/m2. Macroscopic analysis reveals that higher spray pressure induces a more dispersive spray, though this does not significantly improve cooling efficiency. To advance the understanding of R513A spray cooling dynamics, a dimensionless correlation was developed to predict the dynamic heat transfer coefficient across diverse conditions. This study not only highlights the potential of R513A as a sustainable alternative but also provides critical insights into optimizing spray cooling parameters for enhanced thermal management in laser surgery. © 2025 Elsevier Masson SAS

关键词： Chilling

Experimental Investigation on flow and Heat Transfer Characteristics of Helium in Rectangular Narrow Slit Channel

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SSRN 2024年

作者： Li, Changzhong Wang, Chenglong Sun, Yanyu Chen, Ronghua Tian, Wenxi Su, Guanghui Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering China Department of Nuclear Science and Technology Shaanxi Key Lab. of Advanced Nuclear Energy and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China China Nuclear Power Engineering Co. Ltd. Beijing100840 China

Helium is utilized as coolant in high temperature gas cooled reactors. Rectangular narrow slit channels are commonly present in the core. The flow and heat transfer properties of helium significantly affect the core temperature and flow distribution. This paper experimentally investigates the flow and heat transfer properties of high temperature helium in rectangular narrow slit channel. The Reynolds numbers ranged from 468 to 5327, the temperature ratio of wall to bulk from 0.91 to 1.22, the helium outlet temperature up to 944 K, and the maximum heat flux density up to 0.101 MW/m². In the experiment, the total and local convective heat transfer coefficients, along with the friction factors, are measured. Correlation equations for the Nusselt number and friction factor with respect to Reynolds number are derived. The primary findings are as below: the friction factors of helium in rectangular narrow slit channels are significantly larger than those calculated by current empirical correlations. In the turbulent zone, the measured local Nusselt numbers are in excellent accordance with the Gnielinski correlation;however, a significant discrepancy exists in the laminar zone. New flow heat transfer correlation equations are proposed on the bases of experimental data. Upon comparison, the total Nusselt numbers fall in the error of 10%, and almost all local Nusselt numbers and the friction factors fall in the error of 20%. © 2024, The Authors. All rights reserved.

关键词： Helium

Preliminary Conceptual Design with Neutronics and Thermal-Hydraulics Assessments of Fustar

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SSRN 2023年

作者： Zhou, Xingguang Zhang, Dalin Li, Xinyu Lv, Xindi Jiang, Dianqiang Tian, Wenxi Qiu, Suizheng State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Lab. of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi'an Jiaotong University Xi'An710049 China

The fluoride-salt-cooled high-temperature advanced reactor (FuSTAR) is an advanced small modular reactor, which aims to the electric supplement and clean heat production to western China. In this study, neutronics and thermal-hydraulics analysis are also carried out, and established the core layout and material ratio under the near-critical condition. The parameters of the designed core are evaluated quantitatively from various aspects. The results show that FuSTAR has sufficient shutdown depth, the equilibrium cycle is 3.24 years, and the discharge burnup depth is 106 GWd/MtU. The analysis of 1/6 core porous media shows that the peak fuel temperature under normal operating condition is 1009.3 K, which is far below the limit of 1573 K. Relevant design and analysis results can provide the reference for the subsequent small modular FHR design and construction. © 2023, The Authors. All rights reserved.

关键词： Computational fluid dynamics

Experimental Study of an Aluminum Based Three-Dimensional Thermosyphon Heat Sink with Microscale Enhancement Structure

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SSRN 2024年

作者： Yang, Xiaoping Bu, Shichao Jiang, Zhuye Zhou, Yao Sun, Zhen Zhang, Yonghai Wei, Jinjia School of Chemical Engineering and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Mobile Network and Mobile Multimedia Technology ZTE Corporation Hillsides China

Heat dissipation is a significant factor limiting the advancement of electronics. Currently, air cooling remains the most widely used method for heat dissipation due to the advantages of low-cost and easy-maintenance. However, the traditional air-cooling method based on all-solid heat sink fails to meet the fast development in thermal power of electronics because its limitation in area expansion by only solid fins. In this study, an aluminum based three-dimensional thermosyphon (3D-TS) coupling boiling-condensation heat transfer and forced air cooling is proposed to overcome the limitation of conventional air cooling methods. Meanwhile, micro pin-fins structure is used to enhance the boiling heat transfer as well as the performance of the 3D-TS. Using the environmentally friendly refrigerant R1233zd(E) as working fluid, the performance of the 3D-TS is experimentally studied and analyzed under different air volume flow rates. The results show that the total thermal resistance decreases firstly and then increases with the heating power, which is mainly dominated by the boiling mode on the substrate. Moreover, the micro pin-fins greatly enhances the boiling heat transfer on the substrate of the 3D-TS, which enables the 3D-TS to reach a minimum thermal resistance of 0.075 K/W and a maximum thermal dissipating power of 650 W with the temperature of the heating source below 85 °C. The 3D-TS proposed in this work is able to meet the cooling requirements of most high-performance chips. This paper provides valuable reference and guidance for the design and optimization of the phase-change devices. © 2024, The Authors. All rights reserved.

关键词： Aluminum

Performance Prediction and Geometry Optimization of Ejector in Pemfc System Using Coupled Cfd-Bpnn and Genetic Algorithm

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SSRN 2024年

作者： Pang, Zihui Han, Jiquan Feng, Jianmei Diao, Anna Yao, Yanchen Peng, Xueyuan School of Energy and Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China Shanghai Marine Diesel Engine Research Institute Shanghai Shanghai201108 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

The ejector is a promising hydrogen recirculation device in proton exchange membrane fuel cell (PEMFC) systems. However, the limited entrainment performance of the ejector at wide operating conditions hinders its development and widespread application in PEMFC systems. To address this challenge and design a high-performance ejector adapted to the wide power range of PEMFC systems, a backpropagation artificial neural network (BPNN) model with computational fluid dynamics (CFD) simulation data is developed. The sensitivity analysis of geometric parameters based on the CFD model reveals that the nozzle throat diameter (Dt) and the mixing chamber diameter (Dm) exert the most pronounced impact on the entrainment performance, with average influence rates of 24% and 57%, respectively. Furthermore, two advanced multi-objective genetic algorithms (LWGA and NSGA-II methods) are applied to improve ejector performance. The LWGA method proves effective in elevating the overall ejector performance, achieving a remarkable enhancement in entrainment performance of up to 7.9%. On the other hand, the NSGA-II method is favorable for expanding the operational power range of the ejector by 30%, as well as a 4.5% increase in overall ejector performance. This work provides a robust framework for designing and optimizing high-performance ejectors in high power PEMFC systems. © 2024, The Authors. All rights reserved.

关键词： Sensitivity analysis

Regulating Surface Terminals and Interlayer Structure of Ti3c2tx for Superior Nh3 Sensing

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SSRN 2024年

作者： Li, Jiazheng Li, Yanqiong Zeng, Wen Bai, Bofeng Ren, Shan College of Materials Science and Engineering Chongqing University Chongqing400030 China School of Electronic information & Electrical Engineering Chongqing University of Arts and Sciences Chongqing400030 China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an710049 China

MXene materials have exhibited potential in electrochemistry, particularly in gas sensing, due to their excellent conductivity, large specific surface area of layered materials, and unique functional groups. However, the gas sensing performance of intrinsic 2D MXene materials is often limited by their fluorine-containing terminals and interfacial structure. In this study, based on intrinsic Ti3C2Tx, we employed alkali treatment and annealing to prepare oxygen-rich Ti3C2(OH)x/Ti3C2Ox with expanded interlayer spacing, achieving enhanced gas sensing performance for NH3. By utilizing the intercalation effect of layered materials and the synergistic effect of regulating MXene unique surface terminations, the sensing materials prepared have achieved optimization of surface chemistry and structural. Compared to intrinsic Ti3C2Tx, the interlayer spacing of oxygen-rich Ti3C2(OH)x/Ti3C2Ox increased from 9.1 Å to 12.1 Å. The surface terminations of oxygen-rich Ti3C2(OH)x/Ti3C2Ox have been defluorinated and oxygenated. The maximum response value of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3 was 35.66, approximately twice that of the original Ti3C2Tx at an NH3 concentration of 200 ppm. DFT (Density functional theory) calculations and DRIFT (In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy) tests explained the interaction between the surface terminals and NH3, indicating good selectivity and sensitivity of oxygen-rich Ti3C2(OH)x/Ti3C2Ox to NH3. The results of this study demonstrate that the synergistic effects of surface chemistry and structural engineering are crucial for MXene to optimize the electrochemical performance, particularly the gas sensing performance. This provides a feasible approach for the performance optimization of intrinsic MXene materials. © 2024, The Authors. All rights reserved.

关键词： Oxygen