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Full-parameter omnidirectional transformation optical devices

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National Science Review 2024年第3期11卷 92-99页

作者： Yuan Gao Yu Luo Jingjing Zhang Zhengjie Huang Bin Zheng Hongsheng Chen Dexin Ye Interdisciplinary Center for Quantum Information State Key Laboratory of Extreme Photonics and InstrumentationZJU-Hangzhou Global Scientific and Technological Innovation CenterZhejiang University School of Electrical and Electronic Engineering Nanyang Technological University CNRS-InternationalNTU-Thales Research Alliance Nanyang Technological University Institute of Electromagnetic Space Southeast University state Key Laboratory of Millimeter Waves Southeast University International Joint Innovation Center The Electromagnetics Academy at Zhejiang University Zhejiang University Key Laboratory of Advanced Micro/Nano Electronic Devices&Smart Systems of Zhejiang Jinhua Institute of Zhejiang UniversityZhejiang University Shaoxing Institute of Zhejiang university Zhejiang University

Transformation optics(TO) provides an unprecedented technique to control electromagnetic(EM) waves by engineering the constitutive parameters of the surrounding medium through a proper spatial transformation. In general, ideal transformation optical devices require simultaneous electric and magnetic responses along all three dimensions. To ease the practical implementation, previous studies usually made use of reduced parameters or other simplified approaches, which inevitably introduce extra reflection or unwanted phase shift. Up to today, experimental realizations of full-parameter transformation optical devices in free space are still quite limited. Here, a general design strategy is proposed to solve this *** a specific example, a full-parameter spatial-compression TO medium with constitutive parameters taking the diagonal form diag(a, a, 1/a) for the TM wave incidence was designed and realized experimentally. Such spatial-compression TO media were then applied to the implementation of an ideal omnidirectional invisibility cloak capable of concealing a large-scale object over a wide range of illumination angles. Both the simulation and experiment confirm that the cloak allows for nearly unity transmission of EM waves in the forward direction without introducing extra scattering or phase shift. This work constitutes an important stepping stone for future practical implementation of arbitrary full-parameter omnidirectional transformation optical devices.

关键词： transformation optical devices omnidirectional impedance matching full-parameter invisibility cloak

Temperature field characteristics of CF/PEEK thermoplastic composites formed by automated fiber placement using hot gas torch with slit structure nozzle

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Chinese Journal of Aeronautics 2024年第6期37卷 392-409页

作者： Ziang JIN Shouzheng SUN Sunil Chandrakant JOSHI Zhenyu HAN Hongya FU state Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China School of Mechanical and Aerospace Engineering Nanyang Technological UniversitySingapore 639798Singapore

In-situ consolidation forming of high-performance thermoplastic composites by Automated Fiber Placement(AFP)is of significant interest in *** the laying process,the heating temperature has a great influence on the quality of the formed components.A threedimensional heat transfer finite element model of Carbon Fiber(CF)/Polyether Ether Ketone(PEEK)heated by Slit Structure Nozzle Hot Gas Torch(SSNHGT)assisted AFP is *** influence of gas flow rate,heat transfer distance,and laying speed on heating temperature is *** results show that the overall temperature increases and then decreases as the gas flow rate *** the increase in heat transfer distance and laying speed,the overall temperature ***,the gas flow rate has the greatest influence on the temperature of CF/PEEK being heated,followed by the laying speed and finally the heat transfer ***,the model can also be extended to other fiber-reinforced polymer composites formed by hot gas torch assisted AFP,which can guide the optimization of process parameters for subsequent heating temperature control.

关键词： Fiber reinforced plastics Thermoplastics Heating temperature Automated fiber placement CF/PEEK

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A direct polymeric carbon nitride/tungsten oxide Z-scheme heterostructure for efficient photocatalytic hydrogen generation via reforming of plastics into value-added chemicals

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Rare Metals 2024年第8期43卷 3771-3783页

作者： Rui-Zhe Wang Zhi Lin Yi-Qing Wang Kai-Ni Zhang Ge-Hong Zhang Jie Zhang Samuel S.Mao Shao-Hua Shen International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi'an Jiaotong University School of Civil and Architecture Engineering Xi'an Technological University Department of Mechanical Engineering University of California at Berkeley

To promote charge transfer and separation for efficient photocatalysis,a direct Z-scheme heterostructure was constructed by coupling polymeric carbon nitride（PCN） and ***,the obtained PCN/WO3Z-scheme heterostructure could photocataly tic ally produce hydrogen and value-added chemicals（e.g.,formate and acetate） by reforming of plastic polylactic acid（PLA） in alkaline aqueous *** optimizing WO3contents and reaction conditions,the obtained PCN/WO3heterostructure exhibits much increased photocatalytic activity for PLA photoreforming under visible light,with hydrogen evolution rate reaching 402.90 μmol·g-1·h-1,which is 3.5 times that of *** is revealed that the Z-scheme charge transfer between PCN and WO3mainly contributes to the promoted charge separation and thus the improved photocatalytic ***,with h+and·OH experimentally evidenced as the predominant active species,a possible reaction pathway for the reforming of PLA into value-added chemicals（e.g.,formate and acetate）over PCN/WO3Z-scheme heterostructure is cleared by monitoring the reaction intermediates and *** work paves a carbon neutrality and scalable route toward the synergistical production of hydrogen and value-added chemicals by utilizing and recycling plastic waste.

关键词： Carbon nitride Z-scheme heterojunction Plastic waste conversion Photocatalytic H 2 production Value-added chemicals

Combining reinforcement learning with mathematical programming:An approach for optimal design of heat exchanger networks

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Chinese Journal of Chemical Engineering 2024年第5期69卷 63-71页

作者： Hui Tan Xiaodong Hong Zuwei Liao Jingyuan Sun Yao Yang Jingdai Wang Yongrong Yang state Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 310027China ZJU-Hangzhou Global Scientific and technological Innovation Center Hangzhou 311215China

Heat integration is important for energy-saving in the process *** is linked to the persistently challenging task of optimal design of heat exchanger networks(HEN).Due to the inherent highly nonconvex nonlinear and combinatorial nature of the HEN problem,it is not easy to find solutions of high quality for large-scale *** reinforcement learning(RL)method,which learns strategies through ongoing exploration and exploitation,reveals advantages in such ***,due to the complexity of the HEN design problem,the RL method for HEN should be dedicated and designed.A hybrid strategy combining RL with mathematical programming is proposed to take better advantage of both *** insightful state representation of the HEN structure as well as a customized reward function is introduced.A Q-learning algorithm is applied to update the HEN structure using theε-greedy *** results are obtained from three literature cases of different scales.

关键词： Heat exchanger network Reinforcement learning Mathematical programming Process design

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An efficient molten-salt electro-deoxidation strategy enabling fast-kinetics and long-life aluminum-selenium batteries

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SusMat 2024年第1期4卷 126-139页

作者： Jiguo Tu Zheng Huang Cheng Chang Haiping Lei Shuai Wang Shuqiang Jiao state Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijingChina School of Chemistry Chemical Engineering and BiotechnologyNanyang Technological UniversitySingaporeSingapore School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijingChina School of Electrical and Electronic Engineering Nanyang Technological UniversitySingaporeSingapore

Aluminum-selenium(Al-Se)batteries have been considered as one of the most promising energy storage systems owing to their high capacity,energy density,and cost effectiveness,but Se falls challenges in addressing the shuttle effect of soluble intermediate product and sluggish reaction kinetics in the solid-solid conversion process during ***,we propose an unprecedented design concept for fabricating uniform Se/C hollow microspheres with controllable morphologies through low-temperature electro-deoxidation in neutral NaCl-AlCl_(3) molten salt *** Se/C hollow microspheres are demonstrated to hold a favorable hollow structure for hosting Se,which can not only suppress the dissolution of soluble intermediate products into the electrolyte,thereby maintaining the structural integrity and maximizing Se utilization of the active material,but also promote the electrical/ionic conductivity,thus facilitating the rapid reaction kinetics during ***,the as-prepared Se/C hollow microspheres exhibit a high reversible capacity of 720.1 mAh g^(−1)at 500 mA g^(−1).Even at the high current density of 1000 mA g^(−1),Se/C delivers a high discharge capacity of 564.0 mAh g^(−1),long-term stability over 1100 cycles and high Coulombic efficiency of 98.6%.This present work provides valuable insights into short-process recovery of advanced Se-containingmaterials and value-added utilization for energy storage.

关键词： aluminum-ion batteries hollow Se/C microspheres long-term cycling stability lowtemperature electro-deoxidation NaCl-AlCl_(3)molten salt

Global output feedback regulation of time-varying nonlinear systems via the dual-gain method

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Science China(Information Sciences) 2024年第5期67卷 333-334页

作者： Xian-Long YIN Zong-Yao SUN Changyun WEN Institute of Automation Qufu Normal University School of Electrical and Electronic Engineering Nanyang Technological University

Notably, owing to the limited information available, the problem of output feedback stabilization/regulation for nonlinear systems has been explored based on state *** addition, the sensors accounting for state measurement could fail to detect the system states accurately due to the limitations of manufacturing techniques and instruments.

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Optimizing FeCoNiCrTi high-entropy alloy with hydrogen pumping effect to boost de/hydrogenation performance of magnesium hydride

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Rare Metals 2024年第7期43卷 3273-3285页

作者： Meng-Chen Song Fu-Ying Wu Yi-Qun Jiang Xiu-Zhen Wang Hu Zhao Li-Xin Chen Liu-Ting Zhang School of Energy and Power Instrumental Analysis CenterJiangsu University of Science and Technology Max Planck Institute for Iron Research School of Mechanical and Aerospace Engineering Nanyang Technological University state Key Laboratory of Silicon Materials Department of Materials Science and EngineeringZhejiang University

The exploration of efficient,long-lived and cost-effective transition metal catalysts is highly desirable for the practical hydrogen storage of magnesium hydride（MgH2） in sustainable energy ***,FeCoNiCrTi high-entropy alloy（HEA） nanosheets were prepared via a facile wet chemical ball milling strategy and they were introduced into MgH2to boost the hydrogen storage *** refined HEA exhibited superior catalytic activity on *** contrast to additive-free MgH2,the initial desorption temperature of the constructed MgH2-HEA composite was reduced from 330.0 to 198.5℃ and a remarkable 51% reduction in the dehydrogenation activation energy was ***,the MgH2-HEA composite only required one-twentieth time of that consumed by pure MgH2to absorb 5.0 wt% of H2at 225℃.The synergy between the "hydrogen pumping" effect of Mg2Ni/Mg2NiH4and Mg2Co/Mg2CoH5couples,as well as the good dispersion of Fe,Cr and Ti on the surface of MgH2contributed to the enhanced de/hydrogenation performance of the MgH2-HEA *** study furnishes important steering for the design and fabrication of multiple transition metal catalysts and may push the commercial application of magnesium-based hydrides one step forward.

关键词： Hydrogen storage Magnesium hydride High-entropy alloys Catalysis

Hierarchical vectorization for facial images

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Computational Visual Media 2024年第1期10卷 97-118页

作者： Qian Fu Linlin Liu Fei Hou Ying He School of Computer Science and Engineering Nanyang Technological University639798SingaporeSingapore Data61 Commonwealth Scientific and Industrial Research OrganisationSydney2015Australia Interdisciplinary Graduate School Nanyang Technological University and Alibaba Group639798SingaporeSingapore state Key Laboratory of Computer Science Institute of SoftwareChinese Academy of SciencesBeijing100190China university of Chinese Academy of Sciences Beijing100049China

The explosive growth of social media means portrait editing and retouching are in high *** portraits are commonly captured and stored as raster images,editing raster images is non-trivial and requires the user to be highly *** at developing intuitive and easy-to-use portrait editing tools,we propose a novel vectorization method that can automatically convert raster images into a 3-tier hierarchical *** base layer consists of a set of sparse diffusion curves(DCs)which characterize salient geometric features and low-frequency colors,providing a means for semantic color transfer and facial expression *** middle level encodes specular highlights and shadows as large,editable Poisson regions(PRs)and allows the user to directly adjust illumination by tuning the strength and changing the shapes of *** top level contains two types of pixel-sized PRs for high-frequency residuals and fine details such as pimples and *** train a deep generative model that can produce high-frequency residuals *** to the inherent meaning in vector primitives,editing portraits becomes easy and *** particular,our method supports color transfer,facial expression editing,highlight and shadow editing,and automatic *** quantitatively evaluate the results,we extend the commonly used FLIP metric(which measures color and feature differences between two images)to consider *** new metric,illumination-sensitive FLIP,can effectively capture salient changes in color transfer results,and is more consistent with human perception than FLIP and other quality measures for portrait *** evaluate our method on the FFHQR dataset and show it to be effective for common portrait editing tasks,such as retouching,light editing,color transfer,and expression editing.

关键词： face editing vectorization Poisson editing color transfer illumination editing expression editing

Enhanced thermoelectric and mechanical properties of Bi_(0.5)Sb_(1.5)Te_(3) alloy with dispersed yttrium oxide ceramic nanoparticles

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Rare Metals 2024年第4期43卷 1758-1768页

作者： Cun-Cheng Li Ming-Wei Zhang Ji-Wu Xin Lei Wei Wen-Yu Zhao School of Materials Science and Engineering Shandong University of TechnologyZibo255000China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore639798Singapore state Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan430070China

Reducing thermal conductivity while avoiding adverse interfacial reactions during sintering is crucial for improving the thermoelectric performance of Bi_(2)Te_(3)based *** ceramic nanoparticles are good candidates for achieving this *** this study,we designed and prepared a series of p-type Bi_(0.5)Sb_(1.5)Te_(3)nanocomposites decorated with Y_(2)O_(3)ceramic nanoparticles via ball-milling dispersion and spark-plasma *** to the chemical stability of the ceramics,no traces of atomic doping or interfacial reactions were *** measurements revealed that the Y_(2)O_(3)nanoparticles distributed along the grain boundaries acted as energy-dependent carrier-filtering centers to improve the scattering parameter and Seebeck coefficient,contributing to the elevated power factor even with a decreased electrical ***,the incorporated Y_(2)O_(3)nanoparticles and various defect structures they induced effectively strengthened the phonon scattering and suppressed the lattice thermal ***,a peak figure of merit(ZT)of 1.23 at 313 K was achieved for 0.4%Y_(2)O_(3)/Bi_(0.5)Sb_(1.5)Te_(3),which is 13%higher than that of the *** addition,the Vickers hardness of the composite material was 35%higher than that of the *** study demonstrates the effectiveness of ceramic nanoparticles in synergistic ally improving the thermoelectric and mechanical properties,which may be further extended to other thermoelectric systems.

关键词： Bi_(0.5)Sb_(1.5)Te_3 alloy Y_(2)O_(3) ceramic nanoparticles Microstructures Thermoelectric performance Mechanical properties

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