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Chien-physics-informed neural networks for solving singularly perturbed boundary-layer problems

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Applied Mathematics and Mechanics(English Edition) 2024年第9期45卷 1467-1480页

作者： Long WANG lei zhang Guowei HE The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing 100049China

A physics-informed neural network(PINN)is a powerful tool for solving differential equations in solid and fluid ***,it suffers from singularly perturbed boundary-layer problems in which there exist sharp changes caused by a small perturbation parameter multiplying the highest-order *** this paper,we introduce Chien's composite expansion method into PINNs,and propose a novel architecture for the PINNs,namely,the Chien-PINN(C-PINN)*** novel PINN method is validated by singularly perturbed differential equations,and successfully solves the wellknown thin plate bending *** particular,no cumbersome matching conditions are needed for the C-PINN method,compared with the previous studies based on matched asymptotic expansions.

关键词： physics-informed neural network(PINN) singular perturbation boundarylayer problem composite asymptotic expansion

Multi-Scale-Matching neural networks for thin plate bending problem

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Theoretical & Applied Mechanics Letters 2024年第1期14卷 11-15页

作者： lei zhang Guowei He The State Key Laboratory of Nonlinear Mechanics Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China

Physics-informed neural networks are a useful machine learning method for solving differential equations,but encounter challenges in effectively learning thin boundary layers within singular perturbation *** resolve this issue,multi-scale-matching neural networks are proposed to solve the singular perturbation *** by matched asymptotic expansions,the solution is decomposed into inner solutions for small scales and outer solutions for large scales,corresponding to boundary layers and outer regions,***,to conform neural networks,we introduce exponential stretched variables in the boundary layers to avoid semiinfinite region *** results for the thin plate problem validate the proposed method.

关键词： Singular perturbation Physics-informed neural networks Boundary layer Machine learning

Self-Sustaining of Critical Park Microgrids Integrating Mobile Emergency Generators Subjective to Major Outage

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1441-1453页

作者： Quan Sui lei zhang School of Electrical and Information Engineering Zhengzhou UniversityZhengzhou 450001China School of Electrical and New Energy Three Gorges UniversityYichang 443002China

In the event of a major power outage,critical park microgrids(PMGs)could be self-sustaining if mobile emergency generators(MEGs)are stationed to share ***,the need for privacy protection and the value of flexible power support on minute-time scales have not been given enough *** address the problem,this paper proposes a new self-sustaining strategy for critical PMGs integrating ***,to promote the cooperation between PMG and MEG,a bi-level benefit distribution mechanism is designed,where the participants'multiple roles and contributions are identified,and good behaviors are also ***,to increase the alliance benefits,three loss coordination modes are presented to guide the power exchange at the minute level between the MEG and PMG,considering the volatility of renewable generation and *** this basis,a multi-time scale power-energy scheduling strategy is formulated via the alternating direction method of multipliers(ADMM)to coordinate the PMG and ***,a dimensionality reduction technology is designed to equivalently simplify the optimization problem to facilitate the adaptive-step-based ADMM *** studies indicate that the proposed strategy achieves the self-sustaining of PMGs integrating MEGs while increasing the economy by no less than 3.1%.

关键词： Distributed optimization loss coordination mode mobile emergency generator park microgrid power-energy self-sustaining privacy protection

Vitrification cryopreservation of ligaments based on zwitterionic betaine

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Chinese Journal of Chemical Engineering 2024年第8期72卷 1-9页

作者： Liming zhang Xinmeng Liu Haoyue Li lei zhang Department of Biochemical Engineering Frontier Science Center for Synthetic Biology and Key Laboratory of Systems Bioengineering(MOE)School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300350China Haihe Laboratory of Sustainable Chemical Transformations Tianjin 300192China

Ligament cryopreservation enables a prolonged shelf life of allogeneic ligament grafts,which is fundamentally important to ligament ***,conventional cryopreservation techniques fail to eliminate the damage caused by ice crystal growth and the toxicity of cryopreservation agents(CPAs).Here,we report a novel CPA vitrification formulation primarily composed of betaine for ligament *** optimization was conducted on the methods for vitrification and rewarming,as well as the loading and unloading conditions,based on the critical cooling rate(CCR),critical warming rate(CWR),and permeation properties of the *** biomechanical and histological level tests,we demonstrate the superior performance of our method in ligament *** 30 days of vitrification cryopreservation,parameters such as the Young's modulus,tensile stress,denaturation temperature,and glycosaminoglycans content of the ligament remained essentially *** work pioneers the application of ice-free cryopreservation for ligament and holds great potential for improving the long-term storage of ligament,providing valuable insights for future cryopreservation technique development.

关键词： Ligament Betaine Vitrification Cryopreservation

Polarization-driven multifunctional organohydrogels with strain sensitivity toward electromagnetic wave absorption

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Nano Research 2024年第6期17卷 5688-5697页

作者： Yunfei zhang lei zhang Bingqian Zhou Yishan Gao Baoliang zhang School of Chemistry and Chemical Engineering Northwestern Polytechnical UniversityXi’an 710072China Shaanxi Engineering and Research Center for Functional Polymers on Adsorption and Separation Sunresins New Materials Co.Ltd.Xi’an 710072China

Rapid advancements in flexible electronics and military applications necessitate high-performance electromagnetic wave(EMW)*** huge breakthroughs in achieving high-attenuation microwave absorption,conventional EMW absorbing materials have single function and ambiguous absorption ***,numerous gel-type absorbers are fabricated by introducing“regulators”into poly(acrylamide-co-acrylic acid)(P(AM-co-AA))networks through radical polymerization in a glycerol-water mixed *** dielectric constant and EMW absorption performance of the gels are precisely predicted by adjusting monomer concentration,the ratio of glycerol/water,and the content of the ***,A_(6)G_(20)T_(20)-2 exhibits promising absorption performance with a minimum reflection loss(RL_(min))of-33.8 dB at 12.4 *** effective absorption bandwidth(EAB)covers the entire X-band(8.2-12.4 GHz)at a thickness of 2.7 mm.A_(6)G_(20)T_(20)-2 also has sensitive deformation responses and excellent tensile strength,adhesiveness,self-healing and anti-freezing ***,this work not only provides insight into the polarization loss mechanism of the gels as the result of high correlation between EMW absorbing properties and molecular polarization,but also offers an important reference for developing functional protective materials because of the rich functionalities and efficient protective capabilities of the gels.

关键词： organohydrogels molecular polarization microwave absorption strain sensor

Characteristics of a pre-combustion plasma jet igniter

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Chinese Journal of Aeronautics 2024年第7期37卷 178-189页

作者： Jinlu YU Baowen zhang Yang YU Bingbing ZHAO lei zhang Aviation Engineering School Air Force Engineering UniversityXi’an 710038China Equipment Management and Unmanned Aerial Vehicle Engineering School Air Force Engineering UniversityXi’an 710038China

Plasma ignition technology has delivered good performance in the aerospace industry. In this study, a pre-combustion plasma jet igniter was designed, and its characteristics were examined from three aspects: the morphology, temperature, and discharge characteristics and process of ignition. Images of the OH distribution were obtained by using an OH Planar Laser-Induced Fluorescence(OH-PLIF) experimental system. Results have shown that the proposed plasma jet had a higher OH concentration, longer length, and larger area than those of a traditional igniter. The stability of discharge of the igniter was improved as the equivalence ratio φ was increased, and reducing gas flow reduced the pulsation of the plasma jet. When the input current was increased from 15A to 35 A, the highest average temperature increased from 5127 K to 7987 K. An increase in the equivalence ratio reduced the region of arc ionization, but expanded the regions of the core combustion reaction and the outer flame. Herein, this study has obtained a deep understanding of the jet and ignition law and developed a new idea for the application of plasma in the ignition field.A pre-combustion plasma jet igniter can significantly improve the efficiency of ignition and shorten the ignition process compared with a traditional igniter.

关键词： Pre-combustion plasma igniter Plasma Jet temperature field Ignition process Arc Flame

A Multiscale Model of Mass-Functionally Graded Beam-Fluid System Under Bending and Vibration Responses

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Acta Mechanica Solida Sinica 2024年第2期37卷 327-340页

作者： lei zhang Jianping Lin Jiaqing Jiang Guannan Wang Department of Civil Engineering Zhejiang University866 Yuhangtang RoadHangzhou310058China Center for Balance Architecture Zhejiang UniversityHangzhou310007China College of Civil Engineering Huaqiao UniversityXiamen361021China Key Laboratory for Intelligent Infrastructure and Monitoring of Fujian Province Huaqiao UniversityXiamen361021China Department of Engineering Mechanics Zhejiang UniversityHangzhou310027China

In this paper,a multiscale model is developed for the mass functionally graded(FG)beam-fluid system to investigate its static and dynamic responses based on 3D printed porous beam free vibration tests,which are determined by two *** the microstructural level,the gradient variation is realized by arbitrary distribution of matrix pores,and the effective moduli under specific distribution are obtained using the micromechanics homogenization *** the meantime,at the structural level,the mechanical responses of FG porous beams subjected to mass loading are considered in a static fluid ***,the explicit expressions of local finite-element(FE)expressions corresponding to the static and dynamic responses are given in the *** present results are validated against numerical and experimental results from the literature and mechanical tests of 3D printed structures,with good agreement generally obtained,giving credence to the present *** this basis,a comprehensive parametric study is carried out,with a particular focus on the effects of boundary conditions,fluid density,and slenderness ratio on the bending and vibration of FG beams with several different gradations.

关键词： 3D printed test Mass functionally graded beam-fluid system Multiscale model Local finite-element expressions Static bending Free vibration

Modulated-ISRJ rejection using online dictionary learning for synthetic aperture radar imagery

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Journal of Systems Engineering and Electronics 2024年第2期35卷 316-329页

作者： WEI Shaopeng zhang lei LU Jingyue LIU Hongwei College of Oceanography and Space Informatics China University of Petroleum(East China)Qingdao 266580China School of Electronics Engineering Xidian UniversityXi’an 710071China School of Electronics and Communication Engineering Shenzhen Campus of Sun Yat-sen UniversityGuangzhou 518107China School of Computer Science and Technology Xidian UniversityXi’an 710071China

In electromagnetic countermeasures circumstances,synthetic aperture radar(SAR)imagery usually suffers from severe quality degradation from modulated interrupt sampling repeater jamming(MISRJ),which usually owes considerable coherence with the SAR transmission waveform together with periodical modulation *** paper develops an MISRJ suppression algorithm for SAR imagery with online dictionary *** the algorithm,the jamming modulation temporal properties are exploited with extracting and sorting MISRJ slices using fast-time *** dictionary learning is followed to separate real signals from jamming *** the learned representation,time-varying MISRJs are suppressed *** simulated and real-measured SAR data are also used to confirm advantages in suppressing time-varying MISRJs over traditional methods.

关键词： synthetic aperture radar(SAR) modulated interrupt sampling jamming(MISRJ) online dictionary learning

Numerical Simulation Study on Influence of Equation of State on Internal Flow Field and Performance of S-CO_(2)Compressor

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Journal of Thermal Science 2024年第3期33卷 888-898页

作者： zhang lei YANG Zhenyu SUN Enhui zhang Qian AN Guangyao YUAN Wei Hebei Key Laboratory of Low Carbon and High Efficiency Power Generation Technology North China Electric Power UniversityBaoding071003China School of Energy Power&Mechanical EngineeringNorth China Electric Power UniversityBaoding071028China

The low power consumption of the near-critical compressor is the key factor for the high efficiency of supercritical CO_(2)Brayton *** the numerical simulation of the compressor,the rapid changes in the thermophysical properties of the CO_(2)near the critical point make it difficult to capture the condensation *** paper investigates the influence of fluid physical properties on the condensation ***,the differences in the physical properties of CO_(2)in the SRK EOS(equation of state),PR EOS,and SW EOS are ***,the simulation of nozzles and compressors were carried out and *** show that the condensation positions predicted by the three EOSs are basically the *** with SW EOS,the disparities between the maximum condensation mass fraction predicted by the PR and SRK EOSs is5.7%and 11.5%,and that of total pressure ratio is 0.3%and 3.8%,*** results show that PR EOS can be considered for numerical simulation in engineering *** its physical property calculation results are closer to the actual physical properties while the physical properties change more gently,it has considerable accuracy and numerical stability.

关键词： supercritical carbon dioxide equation of state centrifugal compressor numerical simulation condensation