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Track dynamic behavior at rail welds at high speed

Acta Mechanica Sinica 2010年第3期26卷 449-465页

作者： Guangwen xiao Xinbiao xiao jun guo Zefeng Wen Xuesong Jin State Key Laboratory of Traction Power Southwest Jiaotong University 610031 Chengdu China

As a vehicle passing through a track with different weld irregularities, the dynamic performance of track com- ponents is investigated in detail by using a coupled vehi- cle-track model. In the model, the vehicle is modeled as a multi-body system with 35 degrees of freedom, and a Timoshenko beam is used to model the rails which are dis- cretely supported by sleepers. In the track model, the sleepers are modeled as rigid bodies accounting for their vertical, lat- eral and rolling motions and assumed to move backward at a constant speed to simulate the vehicle running along the track at the same speed. In the study of the coupled vehicle and track dynamics, the Hertizian contact theory and the theory proposed by Shen-Hedrick-Elkins are, respectively, used to calculate normal and creep forces between the wheel and the rails. In the calculation of the normal forces, the coefficient of the normal contact stiffness is determined by transient contact condition of the wheel and rail surface. In the calcu- lation of the creepages, the lateral, roll-over motions of the rail and the fact that the relative velocity between the wheel and rail in their common normal direction is equal to zero are simultaneously taken into account. The motion equations of the vehicle and track are solved by means of an explicit integration method, in which the rail weld irregularities are modeled as local track vertical deviations described by some ideal cosine functions. The effects of the train speed, the axle load, the wavelength and depth of the irregularities, and the weld center position in a sleeper span on the wheel-rail impact loading are analyzed. The numerical results obtained are greatly useful in the tolerance design of welded rail pro- file irregularity caused by hand-grinding after rail welding and track maintenances.

关键词： Rail weld. Irregularity. Vehicle-trackcouplingdynamics

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A spherical cavity expansion model for penetration of ogival-nosed projectiles into concrete targets with shear-dilatancy

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Acta Mechanica Sinica 2011年第6期27卷 1001-1012页

作者： Tao He He-Ming Wen xiao-jun guo CAS Key Laboratory for Mechanical Behavior and Design of Materials University of Science and Technology of China 230027 Hefei China

A dynamic spherical cavity-expansion penetration model is suggested herein to predict the penetration and perforation of concrete targets struck normally by ogivalnosed *** dilatancy as well as compressibility of the material in comminuted region are considered in the paper by introducing a dilatant-kinematic relation.A procedure is first presented to compute the radial stress at the cavity surface and then a numerical method is used to calculate the results of penetration and perforation with friction being taken into *** influences of various target parameters such as shear strength,bulk modulus,density,Poisson＇s ratio and tensile strength on the depth of penetration are *** is shown that the model predictions are in good agreement with available experimental *** is also shown that the shear strength plays a dominant role in the target resistance to penetration.

关键词： Spherical cavity expansion Shear dilatancy Ogival-nosed projectile Concrete target Penetration Perforation

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Immobilization and Properties of Lipase from Candida rugosa on Electrospun Nanofibrous Membranes with Biomimetic Phospholipid Moities

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Chemical Research in Chinese Universities 2008年第2期24卷 231-237页

作者： HUANG xiao-jun YU An-guo GE Dan XU Zhi-kang Institute of Polymer Science Key Laboratory of Macromolecular Synthesis and Functionalization of Ministry of Education State Key Laboratory of Chemical Engineering Zhejiang University Hangzhou 310027 P. R. China

Reported here is a protocol to fabricate a biocatalyst with high enzyme loading and activity retention, from the conjugation of electrospun nanofibrous membrane having biomimetic phospholipid moiety and lipase. To improve the catalytic efficiency and activity of the immobilized enzyme, poly（acrylonitrile-co-2-methacryloyloxyethyl phosphorylcholine）s（PANCMPCs） were, respectively, electrospun into nanofibrous membranes with a mean diameter of 90 nm, as a support for enzyme immobilization. Lipase from Candida rugosa was immobilized on these nanofibrous membranes by adsorption. Properties of immobilized lipase on PANCMPC nanofibrous membranes were compared with those of the lipase immobilized on the polyacrylonitrile（PAN） nanofibrous and sheet membranes, respectively. Effective enzyme loading on the nanofibrous membranes was achieved up to 22.0 mg/g, which was over 10 times that on the sheet membrane. The activity retention of immobilized lipase increased from 56.4% to 76.8% with an increase in phospholipid moiety from 0 to 9.6%（molar fraction） in the nanofibrous membrane. Kinetic parameter Km was also determined for free and immobilized lipase. The Km value of the immobilized lipase on the nanofibrous membrane was obviously lower than that on the sheet membrane. The optimum pH was 7.7 for free lipase, but shifted to 8.3-8.5 for immobilized lipases. The optimum temperature was determined to be 35 ℃ for the free enzyme, but 42-44℃ for the immobilized ones, respectively. In addition, the thermal stability, reusability, and storage stability of the immobilized lipase were obviously improved compared to the free one.

关键词： Biomimetic polymer Nanofibrous membrane Electrospinning Enzyme immobilization Lipase

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Ligand Exchange of Colloidal ZnO Nanocrystals from the High Temperature and Nonaqueous Approach

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Nano-Micro Letters 2013年第4期5卷 274-280页

作者： jun Luo Xingliang Dai Sai Bai Yizheng Jin Zhizhen Ye xiao jun guo State Key Laboratory of Silicon Materials Department of Materials Science and Engineering Zhejiang University Cyrus Tang Center for Sensor Materials and Applications Zhejiang University Center for Chemistry of High-Performance and Novel Materials Zhejiang University Department of Electronic Engineering Shanghai Jiao Tong University

Colloidal zinc oxide(ZnO) nanocrystals generated from the high temperature and nonaqueous approache are attractive for use in solution-processed electrical and optoelectronic devices. However, the asprepared colloidal ZnO nanocrystals by this approach are generally capped by ligands with long alkyl-chains,which is disadvantage for solution-processed devices due to hindering charge transport. Here we demonstrate an effective ligand exchange process for the colloidal ZnO nanocrystals from the high temperature and nonaqueous approach by using n-butylamine. The ligand exchange process was carefully characterized. The thin films based on colloidal ZnO nanocrystals after ligand exchange exhibited dramatically enhanced UV photoconductivity.

关键词： ZnO Nanoparticles Ligand exchange Thin films Photoconductivity

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Distribution of oxide inclusions in H13 castings under super-gravity field with multi-stage rotation speeds

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Journal of Iron and Steel Research International 2024年第1期31卷 121-133页

作者： Shao-ying Li xiao-jun Xi Xing-ming Zhao Han-jie guo Jing guo School of Metallurgical and Ecological Engineering University of Science and Technology Beijing(USTB)Beijing100083China Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials Beijing100083China Beijing Beiye Functional Materials Corporation Beijing100192China Shandong Tianwu Forming Technology Co. Ltd.Liaocheng252024ShandongChina

The 42 kg industrial H13 castings were prepared by different super-gravity fields with multi-rotation speeds,and the distribution of oxide inclusions in the castings was *** addition,the inward movement Reynolds number and inward movement time of oxide inclusions as well as the solidification time of molten steel at different positions in the castings were calculated to clarify the removal mechanism of oxide inclusions in super-gravity *** results show that the large size(i.e.,greater than 10μm)oxide inclusions are mainly concentrated in the inner and outer parts of the super-gravity castings with constant rotation speed(500 r min^(-1))and five-stage rotation speeds(500,600,750,850,and 950 r min^(-1)),respectively,while there are no large oxide inclusions in the super-gravity castings with three-stage rotation speeds(500,600,and 750 r min^(-1)).Although an increase in the particle size of inclusion and the rotation speed in super-gravity field is conducive to the increase in the inward movement Reynolds number of oxide inclusions and reduction in the inward movement time of oxide inclusions,it will reduce the local solidification time of molten *** the range of the rotation speed studied,the super-gravity field with three-stage rotation speeds has the best effect on the removal of inclusions in H13 molten steel.

关键词： Distribution Oxide inclusion H13 casting Super-gravity field Rotation speed

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Apoptosis in oncology

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Cell Research 2001年第1期11卷 1-7页

作者： FAN xiao QIANG, YA jun guo (International Joint Cancer Institute, The Second Military Medical University, Shanghai 200423, China) International Joint Cancer Institute The Second Military Medical University Shanghai China

Apoptosis is a complex process involving a large array of genes and mutation of any of these genes may lead to malignancy formation. Re-acquirement of FasL by tumor cells may enable them to evade the surveillance of immune system and thus contributes to the growth of tumor. Apart from traditional therapies, inducing apoptosis of tumor cell by new methods employing death receptor ligands and making use of Fas counterattack is also being developed.

关键词： Apoptosis mitochondria death receptor death receptor ligand tumor therapy.

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A Facile Photo-cross-linking Method for Polymer Gate Dielectrics and Their Applications in Fully Solution Processed Low Voltage Organic Field-effect Transistors on Plastic Substrate

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Chinese Journal of Polymer Science 2018年第8期36卷 918-924页

作者： Ying Liu Jia-Qing Zhao Wen-Jian Sun Yu-Kun Huang Su-Jie Chen xiao-jun guo Qing Zhang Shanghai Key Laboratory of Electrical Insulation and Thermal Aging Department of Polymer Science and EngineeringSchool of Chemistry and Chemical EngineeringShanghai Jiao Tong University Department of Electronic Engineering School of Electronic Information and Electrical EngineeringShanghai Jiao Tong University

A simple and effective photochemical method was developed for cross-linking of polymer gate dielectrics. Laborious synthetic processes for functionalizing polymer dielectrics with photo-cross-linkable groups were avoided. The photo-cross-linker, BBP-4, was added into host polymers by simple solution blending process, which was capable of abstracting hydrogen atoms from polymers containing active C--H groups upon exposure to ultraviolet （UV） radiation. The cross-linking can be completed with a relatively long wavelength UV light （365 nm）. The approach has been applied to methacrylate and styrenic polymers such as commercial poly（methylmethacrylate）（PMMA）, poly（iso-butylmethacrylate）（PiBMA） and poly（4-methylstyrene）（PMS）. The cross-linked networks enhanced dielectric properties and solvent resistance of the thin films. The bottom-gate organic field-effect transistors （OFETs） through all solution processes on plastic substrate were fabricated. The OFET devices showed low voltage operation and steep subthreshold swing at relatively small gate dielectric capacitance.

关键词： Organic field-effect transistors Solution processed Polymer dielectric Cross-linking Photochemistry

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Development review and the prospect of oil shale in-situ catalysis conversion technology

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Petroleum Science 2024年第2期21卷 1385-1395页

作者： Li Wang Chen-Hao Gao Rui-Ying Xiong xiao-jun Zhang Ji-Xiang guo The Unconventional Oil and Gas Institute China University of Petroleum-BeijingBeijing102200China

As an unconventional resource, oil shale possesses abundant reserves and significant potential for industrial applications. The rational and efficient development of oil shale resources holds immense importance in reducing national energy demand. In-situ catalytic technology, characterized by its high efficiency, low pollution, and minimal energy consumption, represents a key direction for future oil shale development. This paper provides a comprehensive review of research progress in in-situ oil shale mining technology, oil shale pyrolysis catalysts, the pyrolysis mechanism of kerogen, and the compatibility of different heating processes and catalysts. Furthermore, the paper proposes future research directions and prospects for oil shale in-situ catalytic technology, including reservoir modification, highefficiency catalyst synthesis, injection processes, and high-efficiency heating technology. These insights serve as valuable technical references for the advancement of oil shale in-situ catalytic technology.

关键词： Oil shale In-situ catalytic technology Pyrolysis catalyst Kerogen pyrolysis mechanism

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P-and SV-wave dispersion and attenuation in saturated microcracked porous rock with aligned penny-shaped fractures

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Petroleum Science 2024年第1期21卷 143-161页

作者： Sheng-Qing Li Wen-Hao Wang Yuan-Da Su jun-Xin guo xiao-Ming Tang School of Geosciences China University of Petroleum(East China)Qingdao 266580ShandongChina Laoshan National Laboratory Qingdao 266071ShangdongChina Guangdong Provincial Key Laboratory of Geophysical High-resolution Imaging Technology Southern University of Science and TechnologyShenzhen 518055GuangdongChina Department of Earth and Space Sciences Southern University of Science and TechnologyShenzhen 518055GuangdongChina

P-and SV-wave dispersion and attenuation have been extensively investigated in saturated poroelastic media with aligned ***,there are few existing models that incorporate the multiple wave attenuation mechanisms from the microscopic scale to the macroscopic ***,in this work,we developed a unified model to incorporate the wave attenuation mechanisms at different scales,which includes the microscopic squirt flow between the microcracks and pores,the mesoscopic wave-induced fluid flow between fractures and background(FB-WIFF),and the macroscopic Biot's global flow and elastic scattering(ES)from the *** Tang's modified Biot's theory and the mixed-boundary conditions,we derived the exact frequency-dependent solutions of the scattering problem for a single penny-shaped fracture with oblique incident P-and *** then developed theoretical models for a set of aligned fractures and randomly oriented fractures using the Foldy *** results indicated that microcrack squirt flow considerably influences the dispersion and attenuation of P-and SV-wave *** coupling effects of microcrack squirt flow with the FB-WIFF and ES of fractures cause much higher velocity dispersion and attenuation for P waves than for SV *** oriented fractures substantially reduce the attenuation caused by the FB-WIFF and ES,particularly for the ES attenuation of SV *** a comparison with existing models in the limiting cases and previous experimental measurements,we validated our model.

关键词： Aligned fractures P-and SV-wave Dispersion and attenuation Microcracked porous background FB-WIFF Elastic scattering Squirt flow

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On the Monge–Kantorovich Mass Transfer Problem in Higher Dimensions

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Acta Mathematica Sinica,English Series 2024年第8期40卷 1989-2004页

作者： xiao jun LU School of Mathematics Southeast UniversityNanjing 210096P.R.China

This paper mainly investigates the approximation of a global maximizer of the Monge–Kantorovich mass transfer problem in higher dimensions through the approach of nonlinear partial differential equations with Dirichlet *** an approximation mechanism,the primal maximization problem can be transformed into a sequence of minimization *** applying the systematic canonical duality theory,one is able to derive a sequence of analytic solutions for the minimization *** the final analysis,the convergence of the sequence to an analytical global maximizer of the primal Monge–Kantorovich problem will be demonstrated.

关键词： Monge-Kantorovich mass transfer singular variational problem canonical duality theory

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