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Radiosensitization mechanism of riboflavin in vitro

Science China(Life Sciences) 2002年第4期45卷 344-351页

作者：刘官树赵芳高建国陈志龙李雨蔡建明姚思德陆长元孟祥顺张黎明 laboratory of Radiation Chemistry Shanghai Institute of Nuclear Research Chinese Academy of Sciences Shanghai China laboratory of Radiation Medicine The Second Military Medical University Shanghai China laboratory of Toxicon & Pharmacy The Second Military Medical University Shanghai China

Riboflavin, suggested to be a radiosensitizer, was studied in murine thymocytes and human hepatoma L02 cell line in vitro with MTT method and fluorescence microscopy. When the murine thymocytes treated with 5-400 μmol/L riboflavin were irradiated by 5 Gy 60Co γ ionizing radiation, the low concentration groups, i.e. treated with 5-50 μmol/L riboflavin, showed a different surviving fractions-time relating correlation compared with the high concentration groups, i.e. treated with 100-400 μmol/L riboflavin. The former had a high survival level at the end of irradiation, but which, after 4-h incubation, decreased rapidly to a low level. On the contrary, the high concentration groups showed a low survival level at the end of irradiation, and a poor correlation was found between the surviving fraction and the incubation time, after 4 h a little difference was observed. The results of fluorescence microscopy indicated that under low concentration conditions, the riboflavin localized mainly in nucleus (both perinuclear area and inside of nuclear membrane), while under high concentration conditions, intensive riboflavin also localized around cytoplasmic membranes. Thus we can conclude: the riboflavin had radiosensitivity effect on DNA under low concentration conditions, and enhanced the damage to cytoplasmic membrane under high concentration conditions. Also the most effective concentration of riboflavin can be evaluated to be approximate 100 μmol/L.

关键词： riboflavin, murine thymocyte, L02 cell, MTT method, fluorescence microscopy, radiosensitization.

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Control of Magnetic Particle Size in Ferrofluid and Its Effect on Rheological Properties

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Chinese Journal of Mechanical Engineering 2022年第3期35卷 227-235页

作者： Siyu Chen Decai Li State Key laboratory of Tribology Tsinghua UniversityBeijing 100084China

Rheological properties are the theoretical basis and the key to common problems in ferrofluid applications,therefore they are expected to be adjustable to satisfy different technical requirements through altering the microstructure of ferrofluid during the process of *** this paper,Four ferrofluid samples with different magnetic particle size were prepared by controlling the concentration of precursor solution during co-precipitation process and the rheological properties of these samples were *** samples exhibited field-controlled rheological *** magnetic field would enhance the formation of microstructures,resulting in an increase of *** with the increase of shear rate,microstructures tended to be destroyed,causing viscosity to *** were two opposing mechanisms of the influence of precursor solution *** one hand,the reduction of the precursor solution concentration would produce primary magnetic particles of smaller *** on the other hand,the surfactant became insufficient to completely coat the magnetic particles because of an increased specific surface area,causing the magnetic particles to aggregate and form secondary clustering structures which strongly enhanced the magnetoviscous effect and weakened the viscoelastic effect.

关键词： Ferrofluid Rheology Magnetoviscous effect Viscoelastic effect

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Interfacial characteristics and properties of a low-clad-ratio AA4045/AA3003 cladding billet fabricated by semi-continuous casting

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International Journal of Minerals,Metallurgy and Materials 2016年第9期23卷 1097-1103页

作者： Xing Han Hai-tao Zhang Bo Shao Lei Li Ke Qin Jian-zhong Cui Key laboratory of Electromagnetic Processing of Materials(Ministry of Education) Northeastern University

A low-clad-ratio AA4045/AA3003 cladding billet was fabricated using a semi-continuous casting process and was subsequently extruded indirectly into a cladding pipe. The temperature distribution near the interface was measured. The microstructures, elemental distribution, Vickers hardness around the bonding interface, and the interfacial shear strength were examined. The results showed that the interface temperature rebounded when AA4045 melt contacted the supporting layer. The two alloys bonded well, with few defects, via the diffusion of Si and Mn in the temperature range from 569℃ to 632℃. The mean shear strength of the bonding interface was 82.3 MPa, which was greater than that of AA3003（75.8 MPa）, indicating that the two alloys bonded with each other metallurgically via elemental interdiffusion. Moreover, no relative slip occurred between the two alloys during the extrusion process.

关键词： aluminum alloys metal cladding casting interdiffusion interfaces

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Unlocking the secrets behind liquid superlubricity:A state-ofthe-art review on phenomena and mechanisms

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Friction 2022年第8期10卷 1137-1165页

作者： Tianyi HAN Shuowen ZHANG Chenhui ZHANG State Key laboratory of Tribology Tsinghua UniversityBeijing 100084China

Superlubricity,the state of ultralow friction between two sliding surfaces,has become a frontier subject in ***,a state-of-the-art review of the phenomena and mechanisms of liquid superlubricity are presented based on our ten-year research,to unlock the secrets behind liquid superlubricity,a major approach to achieve *** overview of the discovery of liquid superlubricity materials is presented from five different categories,including water and acid-based solutions,hydrated materials,ionic liquids(ILs),two-dimensional(2D)materials as lubricant additives,and oil-based lubricants,to show the hydrodynamic and hydration contributions to liquid *** review also discusses four methods to further expand superlubricity by solving the challenge of lubricants that have a high load-carrying capacity with a low shear resistance,including enhancing the hydration contribution by strengthening the hydration strength of lubricants,designing friction surfaces with higher negative surface charge densities,simultaneously combining hydration and hydrodynamic contribution,and using 2D materials(e.g.,graphene and black phosphorus)to separate the contact of ***,uniform mechanisms of liquid superlubricity have been summarized for different liquid lubricants at the boundary,mixed,and hydrodynamic lubrication *** the best of our knowledge,almost all the immense progresses of the exciting topic,superlubricity,since the first theoretical prediction in the early 1990s,focus on uniform superlubricity *** review aims to guide the research direction of liquid superlubricity in the future and to further expand liquid superlubricity,whether in a theoretical research or engineering applications,ultimately enabling a sustainable state of ultra-low friction and ultra-low wear as well as transformative improvements in the efficiency of mechanical systems and human bodies.

关键词： liquid superlubricity hydrodynamic lubrication hydration lubrication surface potential surface forces

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The evolution of microstructure and mechanical properties during high-speed direct-chill casting in different Al–Mg_2Si in situ composites

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International Journal of Minerals,Metallurgy and Materials 2018年第9期25卷 1080-1089页

作者： Dong-tao Wang Hai-tao Zhang Lei Li Hai-lin Wu Ke Qin Jian-zhong Cui Key laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern University

The effect of high-speed direct-chill(DC) casting on the microstructure and mechanical properties of Al–Mg_2Si in situ composites and AA6061 alloy was investigated. The microstructural evolution of the Al–Mg_2Si composites and AA6061 alloy was examined by optical microscopy, field-emission scanning electron microscopy(FE-SEM) and transmission electron microscopy(TEM). The results revealed that an increase of the casting speed substantially refined the primary Mg_2Si particles(from 28 to 12 μm), the spacing of eutectic Mg_2Si(from 3 to 0.5 μm), and the grains of AA6061 alloy(from 102 to 22 μm). The morphology of the eutectic Mg_2Si transformed from lamellar to rod-like and fibrous with increasing casting speed. The tensile tests showed that the yield strength, tensile strength, and elongation improved at higher casting speeds because of refinement of the Mg_2Si phase and the grains in the Al–Mg_2Si composites and the AA6061 alloy. High-speed DC casting is demonstrated to be an effective method to improve the mechanical properties of Al–Mg_2Si composites and AA6061 alloy billets.

关键词： Al–Mg2Si in situ composite casting speed grain size primary Mg2Si mechanical property

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Failure Pressure Analysis of Corroded Moderate-to-High Strength Pipelines

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China Ocean Engineering 2016年第1期30卷 69-82页

作者：苏晨亮李昕周晶 State Key laboratory of Coastal and Offshore Engineering Dalian University of Technology

Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods.

关键词： steel pipeline stress-based criteria failure pressure effect of corrosion width

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Longshore Currents over Barred Beach with Mild Slope

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China Ocean Engineering 2016年第2期30卷 193-204页

作者：王彦邹志利 State Key laboratory of Coastal and Offshore Engineering Dalian University of Technology

The laboratory experiment and numerical simulations of wave-driven longshore currents by random waves on barred beaches with slopes of 1：100 and 1：40 were conducted to investigate the bimodal feature of mean longshore currents,with emphasis on the location and ratio of two peaks of longshore *** location and ratio of two peaks are controlled by the sand *** influences of wave heights and beach slopes on the longshore currents are *** simulations were also performed to compute the measured velocity profile,with the emphasis on the effect of lateral mixing,bottom friction and surface rollers on numerical results.

关键词： barred beach bimodal feature second peak modeling

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A Piston-Type Active Absorbing Wavemaker System with Delay Compensation

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China Ocean Engineering 2015年第6期29卷 917-924页

作者：杨洪齐李木国柳淑学张群王静 State Key laboratory of Coastal and Offshore Engineering Dalian University of Technology

Physical model tests with highly reflective structures often encounter a problem of multiple reflections between the structures and the wavemaker. This paper presents a piston-type active absorbing wavemaker system which can absorb most of the reflections. Based on the first-order wavemaker theory, a frequency domain absorption transfer function is modeled. Its time realization can be achieved by designing an IIR digital filter, which is used to control the absorbing wavemaker system. In a real system, time delays often exist in the wave making process. Thus a delay compensation term to the transfer function is proposed. Experimental results show that the system performs well for both regular and irregular waves with periods from 0.6 s to 2.0 s, and the absorption capability is larger than 96.5% at target wave fields.

关键词： wavemaker active absorption IIR digital filter time delay

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Investigation on the Radial Micro-motion about Piston of Axial Piston Pump

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Chinese Journal of Mechanical Engineering 2013年第2期26卷 325-333页

作者： XU Bing ZHANG Junhui YANG Huayong ZHANG Bin State Key laboratory of Fluid Power Transmission and Control Zhejiang University

The limit working parameters and service life of axial piston pump are determined by the carrying ability and lubrication characteristic of its key friction pairs. Therefore, the design and optimization of the key friction pairs are always a key and difficult problem in the research on axial piston pump. In the traditional research on piston/cylinder pair, the assembly relationship of piston and cylinder bore is simplified into ideal cylindrical pair, which can not be used to analyze the influences of radial micro-motion of piston on the distribution characteristics of oil-film thickness and pressure in details. In this paper, based on the lubrication theory of the oil film, a numerical simulation model is built, taking the influences of roughness, elastic deformation of piston and pressure-viscosity effect into consideration. With the simulation model, the dynamic characteristics of the radial micro-motion and pressure distribution are analyzed, and the relationships between radial micro-motion and carrying ability, lubrication condition, and abrasion are discussed. Furthermore, a model pump for pressure distribution measurement of oil film between piston and cylinder bore is designed. The comparison of simulation and experimental results of pressure distribution shows that the simulation model has high accuracy. The experiment and simulation results demonstrate that the pressure distribution has peak values that are much higher than the boundary pressure in the piston chamber due to the radial micro-motion, and the abrasion of piston takes place mainly on the hand close to piston ball. In addition, improvement of manufacturing roundness and straightness of piston and cylinder bore is helpful to improve the carrying ability of piston/cylinder pair. The proposed research provides references for designing piston/cylinder pair, and helps to prolong the service life of axial piston pump.

关键词： axial piston pump piston/cylinder pair micro motion carrying ability

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Hydrodynamic Interactions of Three Barges in Close Proximity in A Floatover Installation

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China Ocean Engineering 2016年第3期30卷 343-358页

作者：许鑫李欣杨建民肖龙飞 State Key laboratory of Ocean Engineering Shanghai Jiao Tong University

The hydrodynamics of side-by-side barges are much more complex than those of a single barge in waves because of wave shielding, viscous effects and water resonance in the gap. In the present study, hydrodynamic coefficients in the frequency domain were calculated for both the system of multiple bodies and the isolated body using both low-order and higher-order boundary-element methods with different element numbers. In these calculations, the damping-lid method was used to modify the free-surface boundary conditions in the gap and to make the hydrodynamic results more reasonable. Then far-field, mid-field and near-field methods were used to calculate wave-drift forces for both the multi-body system and the isolated body. The results show that the higher-order method has faster convergence speed than the low-order method for the multi-body case. Comparison of different methods of computing drift force showed that mid-field and far-field methods have better convergence than the near-field method. In addition, corresponding model tests were performed in the Deepwater Offshore Basin at Shanghai Jiao Tong University. Comparison between numerical and experimental results showed good agreement.

关键词： multi-body side-by-side hydrodynamic interaction floatover

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