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The Mechanism of kIH in delayed Hydride Cracking of Zr-2.5wt% Nb at 150 ℃

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材料科学与工程学报 2000年第Z2期20卷 854-858页

作者： d.yan department of Chemical and Materials Engineering University of AlbertaEdmonton Alberta Canada T6G 2G6

This work studies the KIH mechanism of delayed hydride cracking (dHC) in Zr-2.5wt% Nb alloys. A modified experimental method was developed, in which specimens are fatigued between consecutive experiments, and a constant load instead of a decreasing load is used in each experiment. The hydride clusters formed and fractured at the crack tip during different experiments are thus separated and studied individually. A new R-curve phenomenon that characterizes the resistance to dHC was observed. KIH is thus more rigorously defined. Based on the measurement of the critical hydride cluster length at different K1, the threshold phenomenon of KIH is explained.

关键词： instead of crack tip used in

高压断路器SF_6电弧电流零区动态特征和衰减行为的研究综述

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中国电机工程学报 2015年第8期35卷 2059-2072页

作者：王伟宗荣命哲 yan J d 吴翊仲林林电力设备电气绝缘国家重点实验室(西安交通大学) 陕西省西安市710049 英国利物浦大学电机工程与电子系

高压SF6断路器开断故障电流的成功与否与电弧在电流零区的动态特征和衰减行为紧密相关,涉及到一个介质状态从导电到绝缘转变的过程,包含大量的基础科学问题。电弧现象是一个多物理场相互耦合变化的复杂过程,其研究涉及的学科领域广,交... 详细信息

高压SF6断路器开断故障电流的成功与否与电弧在电流零区的动态特征和衰减行为紧密相关,涉及到一个介质状态从导电到绝缘转变的过程,包含大量的基础科学问题。电弧现象是一个多物理场相互耦合变化的复杂过程,其研究涉及的学科领域广,交叉性强。由于实验和理论研究中存在的困难,目前对SF6电弧电流零区动态衰减特性的了解尚不完善清晰;相关研究属于电器研究领域的难点之一,是定量预测断路器开断性能的技术瓶颈。以高压断路器SF6电弧为对象,从理论研究、实验测试层面以及宏观、微观角度,综述了国内外高压断路器SF6电弧等离子体特性,特别是非平衡态下电弧电流零区动态特征和衰减行为的研究进展,并对未来的研究工作进行了展望。

关键词：高压断路器 SF6电弧等离子体物性参数电流零区动态特性衰减行为

Large eddy simulation study of 3d wind field in a complex mountainous area under different boundary conditions

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第7期25卷 541-556页

作者： yan LI Lei yan Xuhui HE School of Civil Engineering Central South UniversityChangsha410075China National Engineering Research Center for High-speed Railway Construction Changsha410075China Hunan Provincial Key Laboratory for disaster Prevention and Mitigation of Rail Transit Engineering Structures Changsha410075China

Large eddy simulations generally are used to predict 3d wind field characteristics in complex mountainous *** simulation boundary conditions,such as the height and length of the computational domain or the characteristics of inflow turbulence,can significantly impact the quality of *** this study,we examined these boundary conditions within the context of the mountainous terrain around a long-span cable-stayed bridge using a wind tunnel *** sizes of computational domains and turbulent incoming wind velocities were used in large eddy *** results show that when the height of the computational domain is five times greater than the height of the terrain model,there is minimal influence from the top wall on the wind field characteristics in this complex mountainous *** the length of the wake region of the computational domain has negligible effects on the wind *** in the inlet boundary reduces the length of the wake region on a leeward hill with a low slope,but has less impact on the mean wind velocity of steep hills.

关键词： Large eddy simulation(LES) Spectral representation method Recycling method High mountainous canyon Wind characteristics Atmospheric boundary layer Computational domain

Electromagnetic characteristic analysis and design of a linear motor used for ultra-high-speed EMS maglev train

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Science China(Technological Sciences) 2024年第6期67卷 1957-1973页

作者： GAO Han SHI TingNa GAO XinMai LEI yanXiao yan dong GUO Liyan yan yan College of Electrical Engineering Zhejiang UniversityHangzhou310027China Zhejiang University Advanced Electrical Equipment Innovation Center Hangzhou311107China State Key Laboratory of High-speed Maglev Transportation Technology Qingdao266100China CRRC Qingdao Sifang Co.Ltd. Qingdao266111China

The operating speed of the commercial electromagnetic suspension(EMS)maglev train has been over 430 km/h,making it the fastest means of land *** the increasing demands of people traveling,it is necessary to further improve the operating speed of maglev *** to examine whether the existing EMS system can meet the requirements of ultra-highspeed operation(more than 600 km/h),the electromagnetic characteristics of an EMS linear motor under the operating speed of 600–1000 km/h fed by a square-wave voltage supply is investigated in this ***,an electromagnetic field model of the EMS system under the square-wave voltage supply is established to investigate its electromagnetic performance,e.g.,the characteristics of phase current,the magnetic flux density,and the electromagnetic ***,the relationship between the harmonic components of the air-gap magnetic flux density and electromagnetic force is investigated using the two-dimensional fast Fourier transform(2d-FFT)to reveal the mechanism of electromagnetic force ***,to address the issues of excessive armature current density and significant electromagnetic force ripple,the linear motor is re-designed by enlarging the stator slot area and reshaping the mover's main magnetic ***,the Taguchi method is used to further improve the electromagnetic characteristics of the linear electric ***,the effectiveness of the proposed optimal design is validated by the finite-element analysis(FEA)based co-simulation.

关键词： ultra-high-speed maglev transportation electromagnetic suspension(EMS) linear motor electromagnetic force ripple suppression

Topology Optimization of Two Fluid Heat Transfer Problems for Heat Exchanger design

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Computer Modeling in Engineering & Sciences 2024年第8期140卷 1949-1974页

作者： Kun yan Yunyu Wang Jun yan School of Chemical Engineering Dalian University of TechnologyDalian116024China Jianghuai Advanced Technology Center Hefei230000China State Key Laboratory of Structural Analysis for Industrial Equipment Department of Engineering MechanicsInternational Research Center for Computational MechanicsDalian University of TechnologyDalian116024China

Topology optimization of thermal-fluid coupling problems has received widespread *** article proposes a novel topology optimization method for laminar two-fluid heat exchanger *** proposed method utilizes an artificial density field to create two permeability interpolation functions that exhibit opposing trends,ensuring separation between the two fluid ***,a Gaussian function is employed to construct an interpolation function for the thermal conductivity ***,a computational program has been developed on the OpenFOAM platform for the topology optimization of two-fluid heat *** program leverages parallel computing,significantly reducing the time required for the topology optimization *** enhance computational speed and reduce the number of constraint conditions,we replaced the conventional pressure drop constraint condition in the optimization problem with a pressure inlet/outlet boundary *** 3d optimization results demonstrate the characteristic features of a surface structure,providing valuable guidance for designing heat exchangers that achieve high heat exchange efficiency while minimizing excessive pressure *** the same time,a new structure appears in large-scale topology optimization,which proves the effectiveness and stability of the topology optimization program written in this paper in large-scale calculation.

关键词： Topology optimization two fluid heat exchanger OpenFOAM large scale

Rational surface charge engineering of haloalkane dehalogenase for boosting the enzymatic performance in organic solvent solutions

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Chinese Journal of Chemical Engineering 2024年第1期65卷 276-285页

作者： Yin Wu yan Sun department of Biochemical Engineering School of Chemical Engineering and Technology and Key Laboratory of Systems Bioengineering and Frontiers Science Center for Synthetic Biology(Ministry of Education)Tianjin UniversityTianjin 300350China

Biocatalysis in organic solvents(OSs)has numerous important applications,but native enzymes in OSs often exhibit limited catalytic ***,we proposed a computation-aided surface charge engineering strategy to improve the catalytic performance of haloalkane dehalogenase dhaA in OSs based on the energetic analysis of substrate binding to the dhaA *** variants with enhanced OS resistance were obtained by replacing negative charged residues on the surface with positive charged residue(Arg).Particularly,a four-substitution variant E16R/E93R/E121R/E257R exhibited the best catalytic performance(five-fold improvement in OS resistance and seven-fold half-life increase in 40%(vol)dimethylsulfoxide).As a result,the overall catalytic performance of the variant could be at least 26 times higher than the wild-type *** spectroscopy and molecular dynamics simulation studies revealed that the residue substitution mainly enhanced OS resistance from four aspects:(a)improved the overall structural stability,(b)increased the hydrophobicity of the local microenvironment around the catalytic triad,(c)enriched the hydrophobic substrate around the enzyme molecule,and(d)lowered the contact frequency between OS molecules and the catalytic *** findings validate that computationaided surface charge engineering is an effective and ingenious rational strategy for tailoring enzyme performance in OSs.

关键词： Surface charge engineering Organic solvent resistance Molecular dynamics simulation Haloalkane dehalogenase

Towards direct superlubricity and superlow wear via amino modification of polyhydroxy alcohol solutions

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Friction 2024年第9期12卷 1980-1990页

作者： Qiang MA Chengpeng yan Rui yan Xin XU Haifeng WANG State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi'an 710072China Chongqing Innovation Center Northwestern Polytechnical UniversityChongqing 401135China Research&development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518063China

Friction remains as the primary mode of energy dissipation and components wear,and achieving superlubricity shows high promise in energy conservation and lifetime wear *** results in this work demonstrate that direct superlubricity combined with superlow wear can be realized for steel/Si_(3)N_(4)contacts on engineering scale when polyhydroxy alcohol solution was selectively modified by amino *** direct superlubricity occurs because 3-amino-1,2-propanediol molecules at the friction interface could be induced to rotate and adsorb vertically on the friction surface,forming in-situ thick and dense molecular films to passivate the asperity ***,amino modification is also conducive to improving the lubrication state from boundary to mixed lubrication regime by strengthening the intermolecular hydrogen bonding interaction,presenting enhanced load-bearing capability and reduced direct solid asperity ***,direct superlow average friction of 0.01 combined with superlow wear are achieved *** design principle of direct superlubricity and superlow wear in this work indeed offers an effective strategy to fundamentally improve energy efficiency and provide lifetime wear protection for moving mechanical assemblies.

关键词： direct superlubricity amino modification molecular layer superlow wear

Recent progress in diagnostic imaging and therapeutics of osteosarcoma based on multifunctional nanoparticles

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Science China Chemistry 2024年第9期67卷 2864-2889页

作者： Xueke yan danmin Lin dingyuan yan dong Wang Huifang Su department of Orthopaedic Surgery The First Affiliated Hospital of Zhengzhou UniversityZhengzhou 450052China Center for AIE Research College of Materials Science and EngineeringShenzhen UniversityShenzhen 518060China

Osteosarcoma is one of the most common primary bone malignancies,mainly occurring in children and *** diagnosis imaging methods for osteosarcoma contain X-ray,computed tomography and magnetic resonance imaging,and traditional therapy protocols are surgical resection and ***,these strategies are complicated and *** imaging methods,despite their maturity,have drawbacks that prevent them from showing more *** is more,the prognosis for patients with osteosarcoma remains unsatisfactory due to side effects of chemotherapy,as well as incomplete surgical removal of the *** compensate for the shortcomings of traditional imaging and treatment strategies for osteosarcoma,various types of nanoparticles have been designed and synthesized to selectively target osteosarcoma cells without toxic side effects on healthy *** the same time,these nanoparticle-based technologies can integrate the imaging and treatment of *** review summarizes the application of nanotechnology in the imaging and treatment of osteosarcoma in recent years,and finally discusses the challenges and development prospects,aiming to provide ideas for future research.

关键词： osteosarcoma nanotechnology imaging diagnosis therapy

Preparation and characterization of pH-responsive metal-polyphenol structure coated nanoparticles

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Food Science and Human Wellness 2024年第3期13卷 1303-1310页

作者： Qile Xia yan Liang Ailing Cao yan Cao Luyun Cai Key Laboratory of Post-Harvest Handling of Fruits Food Science InstituteZhejiang Academy of Agricultural SciencesHangzhou 310021China Ningbo Research Institute College of Biosystems Engineering and Food ScienceZhejiang UniversityNingbo 315100China School of Biological and Chemical Engineering Zhejiang Engineering Research Center for Intelligent Marine Ranch EquipmentNingboTech UniversityNingbo 315100China College of Food Science and Engineering Bohai UniversityJinzhou 121013China Hangzhou Customs district Hangzhou 310007China

In this paper,tannic acid(TA)and Fe~(3+)were added to form a layer of metal-polyphenol network structure on the surface of the nanoparticles which were fabricated by zein and carbon quantum dots(CQds)encapsulating phlorotannins(PTN).pH-Responsive nanoparticles were prepared successfully(zein-PTN-CQds-Fe-~Ⅲ).Further,the formation of composite nanoparticles was confirmed by a series of characterization *** zeta-potential and Fourier transform infrared spectroscopy data proved that electrostatic interaction and hydrogen bonding are dominant forces to form *** encapsulation efficiency(EE)revealed that metal-polyphenol network structure could improve the EE of *** analysis and differential scanning calorimetry experiment indicated the thermal stability of zein-PTN-CQds-Fe~Ⅲnanoparticles increased because of metal-polyphenol network *** pH-responsive nanoparticles greatly increased the release rate of active substances and achieved targeted release.

关键词： Metal Phlorotannins Nanoparticles pH-Responsive Characterization