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The Perturbed Problem on the Boussinesq System of Rayleigh-Bénard Convection

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Acta Mathematicae Applicatae Sinica 2014年第1期30卷 75-88页

作者： jian-guo shi Shu WANG Ke WANG Feng-ying HE College of Applied Sciences Beijing University of Technology Department of Mathematics Huanghuai University Zhoukou Vocational and Technical College

In this paper,the infinite Prandtl number limit of Rayleigh-B′enard convection is *** well prepared initial data,the convergence of solutions in L∞（0,t;H2（G）） is rigorously justified by analysis of asymptotic ex... 详细信息

关键词： infinite Prandtl number limit Rayleigh-B^nard convection boussinesq system asymptotic expansions iterative techniques

Suppression of low-frequency ultrasound broadband vibration using star-shaped single-phase metamaterials

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Defence Technology（防务技术） 2024年第4期34卷 217-224页

作者： Rui Zhao jian Zheng Jin guo Yunbo shi Hengzhen Feng Jun Tang Jun Liu Science and Technology on Electronic Test&Measurement Laboratory North University of ChinaTaiyuan 030051ShanxiChina School of Mechatronical Engineering Beijing Institute of TechnologyBeijing 100081China

In order to suppress the low-frequency ultrasound vibration in the broadband range of 20 k Hz—100 k Hz,this paper proposes and discusses an acoustic metamaterial with low-frequency ultrasound vibration attenuation properties,which is configured by hybrid arc and sharp-angle convergent star-shaped *** effect of the dispersion relation and the bandgap characteristic for the scatterers in star-shaped are simulated and *** target bandgap width is extended by optimizing the geometry parameters of arc and sharp-angle convergent *** proposed metamaterial configured by optimized hybrid lattices exhibits remarkable broad bandgap characteristics by bandgap complementarity,and the simulation results verify a 99%vibration attenuation amplitude can be obtained in the frequency of20 k Hz—100 k *** the fabrication of the proposed hybrid configurational star-shaped metamaterial by 3D printing technique,the transmission loss experiments are performed,and the experimental results indicate that the fabricated metamaterial has the characteristics of broadband vibration attenuation and an amplitude greater than 85%attenuation for the target *** results demonstrate that the hybrid configurational star-shaped metamaterials can effectively widen the bandgap and realize high efficiency attenuation,which has capability for the vibration attenuation in the application of highprecise equipment.

关键词： Star-shaped metamaterials Broadband Vibration attenuation Low-frequency ultrasound vibration Transmission loss

Dynamically updated digital twin for prognostics and health management:Application in permanent magnet synchronous motor

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Chinese Journal of Aeronautics 2024年第6期37卷 244-261页

作者： Haoyu guo Shaoping WANG jian shi Tengfei MA Giorgio GUGLIERI Rujun JIA Fausto LIZZIO School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China Tianmushan Laboratory Hangzhou 310023China Department of Mechanical and Aerospace Engineering Polytechnic University of TurinTurin 10129Italy Beihang Ningbo Research Institute Ningbo 315800China

Current research on Digital Twin(DT)based Prognostics and Health Management(PHM)focuses on establishment of DT through integration of real-time data from various sources to facilitate comprehensive product monitoring and health ***,there still exist gaps in the seamless integration of DT and PHM,as well as in the development of DT multi-field coupling modeling and its dynamic update *** the product experiences long-period degradation under load spectrum,it is challenging to describe the dynamic evolution of the health status and degradation progression *** addition,DT update algorithms are difficult to be integrated simultaneously by current *** paper proposes an innovative dual loop DT based PHM framework,in which the first loop establishes the basic dynamic DT with multi-filed coupling,and the second loop implements the PHM and the abnormal detection to provide the interaction between the dual loops through updating *** proposed method pays attention to the internal state changes with degradation and interactive mapping with dynamic parameter ***,the Independence Principle for the abnormal detection is proposed to refine the theory of *** at the first loop focus on accurate modeling of multi-field coupling,while the events at the second loop focus on real-time occurrence of anomalies and the product degradation *** interaction and collaboration between different loop models are also ***,the Permanent Magnet Synchronous Motor(PMSM)is used to verify the proposed *** results show that the modeling method proposed can accurately track the lifecycle performance changes of the entity and carry out remaining life prediction and health management effectively.

关键词： Digital Twin(DT) Dynamic Update Independence Principle Multi-field Coupling Permanent Magnet Synchronous Motor(PMSM) Prognostics and Health Management(PHM)

Understanding the Thermal Impedance of Silicone Rubber/Hexagonal Boron Nitride Composites as Thermal Interface Materials

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Chinese Journal of Polymer Science 2024年第3期42卷 352-363,I0008页

作者： Yuan Ji shi-Da Han Hong Wu Shao-Yun guo Feng-Shun Zhang jian-Hui Qiu The State Key Laboratory of Polymer Materials Engineering Sichuan Provincial Engineering Laboratory of Plastic/Rubber Complex Processing TechnologyPolymer Research InstituteSichuan UniversityChengdu 610065China Institute of Chemical Materials China Academy of Engineering PhysicsMianyang 621900China Department of Mechanical Engineering Faculty of Systems Science and TechnologyAkita Prefectural UniversityAkita 015-0055Japan

Silicone rubber(SR) composites are most widely used as thermal interface materials(TIMs) for electronics heat dissipation. Thermal impedance as the main bottleneck limiting the performance of TIMs is usually neglected. Herein, the thermal impedance of SR composites loaded with different levels of hexagonal boron nitride(h-BN) as TIMs was elaborated for the first time by the ASTM D 5470 standard test and finite element analysis. It was found that elastic modulus and surface roughness of SR composites increased with the increase of h-BN content, indicating that the conformity was reduced. When the assembly pressure was 0.69 MPa, there existed an optimal h-BN content at which the contact resistance was minimum(0.39 K·cm^(2)·W^(-1)). Although the decreased bond line thickness(BLT) by increasing the assembly pressure was beneficial to reduce the thermal impedance, the proper assembly pressure should be selected to prevent the warpage of the contact surfaces and the increase in contact resistance, according to the compression properties of the SR composites. This study provides valuable insights into fabrication of high-performance TIMs for modern electronic device applications.

关键词： Thermal interface materials Hexagonal boron nitride Thermal impedance Surfaces

A novel thermally-stable single-phase phosphor Ca2InTaO6:Dy3+ for NUV-excited white LEDs

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Journal of Rare Earths 2024年第10期42卷 1855-1864页

作者： jian Hu Ruirui Cui Jun Zhang Peng Linghu Youzhen shi Xiang guo Key Laboratory of Micro-Nano-Electronics and Software Technology of Guizhou Province College of Big Data and Information EngineeringGuizhou University College of Computer and Information Engineering Guizhou University of Commerce

The work focuses on the utilization of the conventional solid-state sintering procedure to synthesize white phosphors Ca2InTaO6:xDy3+（0.02≤x≤0.12）.Utilizing X-ray diffraction,the phase structure of samples was examined,and the crystal structure was refined using the Rietveld method.A scanning electron microscope was used to analyze the microstructure of ***-principles calculations confirm that the indirect bandgap of Ca2InTaO6is 3.786 eV,The luminous properties and energy transfer mechanism of Ca2InTaO6:xDy3+were studied using photoluminescence ***4F9/2→6H13/2transition of Dy3+ions is responsible for the greatest emission peak,which was measured at 575 *** to research,the lifespan falls as the concentration of Dy3+doping amount rises because of frequent interaction and ene rgy transfer between Dy3+*** correlated color temperature of the WLEDs packaged with Ca2InTaO6:0.08Dy3+is 4677 K and CIE 1931 chromaticity coordinates are（0.3578,0.3831）.Meantime,the phosphor also shows outstanding te mperature stability property,which maintains 83.8% of its initial emission intensity at 450 K（activation energy of 0.1467 eV）.The W-LEDs retain their performance for 100 min when powered at 3.4 V voltage and 600 mA current,demonstrating the packed W-LEDs' sustaine d operation at high temperatures.

关键词： Ca2InTaO6:Dy3+ phosphors Photoluminescence Rare earths Thermal imaging Thermal stability W-LEDs

Harnessing data using symbolic regression methods for discovering novel paradigms in physics

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Science China(Physics,Mechanics & Astronomy) 2024年第6期67卷 1-11页

作者： jianyang guo Wan-jian Yin College of Energy Soochow Institute for Energy and Materials Innovations(SIEMIS)Jiangsu Provincial Key Laboratory for Advanced Carbon Materials and Wearable Energy TechnologiesSoochow UniversitySuzhou 215006China Shanghai Qi Zhi Institute Shanghai 200232China Light Industry Institute of Electrochemical Power Sources Soochow UniversitySuzhou 215006China

In recent years,machine-learning methods have profoundly impacted research in the interdisciplinary fields of ***,most machine-learning models lack interpretability,and physicists doubt the credibility of their conclusions because they cannot be combined with prior physical ***,this review focuses on symbolic regression,which is an interpretable machine-learning ***,the relevant concepts of machine learning are introduced in conjunction with ***,we provide an overview of symbolic regression ***,the recent directions for the application of symbolic regression methods in different subfields of physics are outlined,and an overview of the ways in which the applications of symbolic regression have evolved in the realm of physics is *** major aim of this review is to introduce the basic principles of symbolic regression and explain its applications in the field of physics.

关键词： machine learning genetic programming symbolic regression

Effective utilization of dolomitic lead-zinc waste rock by replacing dolomite as flux in iron ore sintering process

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Journal of Iron and Steel Research International 2024年第8期31卷 1861-1872页

作者： Xin Wang Cong-cong Yang jian Pan De-qing Zhu Zheng-qi guo Guang-hui Xia shi-juan Qu School of Minerals Processing and Bioengineering Central South UniversityChangsha 410083HunanChina Low-Carbon and Hydrogen Metallurgy Research Center Central South UniversityChangsha 410083HunanChina

With increasingly stringent environmental protection policies,cost-effective and value-added treatment of massive lead-zinc waste rock(LZWR)generated from the preconcentration process has attracted substantial attention.A type of dolomitic LZWR with 18 wt.%MgO,27 wt.%CaO,0.29 wt.%Zn and 1.43 wt.%S was used as a replacement flux in the iron ore sintering *** sinter pot tests were carried out based on an industrial ore *** results show that replacing 0%-60%of dolomite with LZWR does not adversely affect the sintering productivity,fuel consumption rate,and the quality of the sinter products,while the Zn and S elements contained in LZWR can be effectively removed with the residual Zn and S contents of the resultant sinter products being less than 0.02 and 0.055 wt.%,***,substituting LZWR for dolomite as a flux inevitably increases the SO_(2) concentration in the sintering flue gas due to its high sulfur *** the processing capacity of the sintering flue gas desulfurization system,the replacement ratio of dolomite can reach 40%,equal to LZWR consumption of 24.3 kg per ton of *** SO_(2) in sintering flue gas can be recovered to produce(NH_(4))_(2)SO_(4) or HSO_(4),while the volatilized Zn collected into the zinc-containing dust can be subsequently recycled by the rotary hearth furnace ***,it is technologically and economically feasible to use the LZWR as a replacement flux in the iron ore sintering process,providing a new way for the safe,large-scale and low-cost treatment of LZWR.

关键词： Lead Zinc waste rock Dolomite Sintering Flue gas Sinter product

Diffractive neural networks with improved expressive power for gray-scale image classification

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Photonics Research 2024年第6期12卷 1159-1166页

作者： MINJIA ZHENG WENZHE LIU LEI shi jian ZI State Key Laboratory of Surface Physics Key Laboratory of Micro-and Nano-Photonic Structures(Ministry of Education)and Department of PhysicsFudan UniversityShanghai 200433China Institute for Nanoelectronic Devices and Quantum Computing Fudan UniversityShanghai 200433China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China Shanghai Research Center for Quantum Sciences Shanghai 210315China

In order to harness diffractive neural networks(DNNs)for tasks that better align with real-world computer vision requirements,the incorporation of gray scale is ***,DNNs are not powerful enough to accomplish gray-scale image processing tasks due to limitations in their expressive *** our work,we elucidate the relationship between the improvement in the expressive power of DNNs and the increase in the number of phase modulation layers,as well as the optimization of the Fresnel number,which can describe the diffraction *** demonstrate this point,we numerically trained a double-layer DNN,addressing the prerequisites for intensitybased gray-scale image ***,we experimentally constructed this double-layer DNN based on digital micromirror devices and spatial light modulators,achieving eight-level intensity-based gray-scale image classification for the MNIST and Fashion-MNIST data *** optical system achieved the maximum accuracies of 95.10%and 80.61%,respectively.

关键词： process mirror limitations

Reduction behavior of iron ore powder by high-volatile coal in thermogravimetric-gas chromatographic and kinetic analysis

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Journal of Iron and Steel Research International 2024年第1期31卷 92-107页

作者： Rui-meng shi Qi-yuan Mi Bin Li Xiao shi Chong Zou Jing guo Han-jie guo School of Metallurgical Engineering Xi’an University of Architecture and TechnologyXi’an710055ShaanxiChina China International Engineering Consulting Corporation Beijing100048China School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing100083China

The reduction behavior of iron ore powder by high-volatile coal was investigated,and its kinetic mechanism was *** effect of volatiles in coal on the reduction reaction of iron ore was compared by utilizing a Xinjiang lignite with a high volatile content and its pyrolysis carbon produced by high-temperature pyrolysis to remove volatiles,serving as a *** mass loss and gas composition of the samples during the reduction process were detected using thermo-gravimetric analysis and gas chromatography,and the morphological changes of iron ore powder were observed through scanning electron *** kinetic parameters of the iron oxide reduction reaction were calculated by the Flynn-Ozawa-Wall method,and the kinetic mechanism of volatile participation in the iron oxide reduction reaction was determined through the Coats-Redfern *** results indicate that the coupling effect between the high-volatile coal pyrolysis and reduction reactions occurs during the second stage of the entire coupling process,which corresponds to the late stage of coal pyrolysis with a substantial release of H_(2)and *** volatiles in coal actively participated in the reduction reaction,reducing the initiation temperature of the reaction by around 200℃.The reduction of iron oxides by high-volatile coal was jointly promoted by the"hydrogen cycle"and"carbon cycle",resulting in a higher reduction extent and metallization rate at the end of the *** high-volatile coal was used as the reductant,the average activation energy for the entire process was 76.5 kJ/mol,a significant decrease compared to the employment of pyrolysis carbon without volatiles as the reductant(1167 kJ/mol).

关键词： Direct reduction High-volatile coal Volatile Kinetics Reduction mechanism