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Timoshenko beam model for chiral materials

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Acta Mechanica Sinica 2018年第3期34卷 549-560页

作者： T.y.Ma y.n.Wang L.yuan J.S.Wang Q.H.Qin Department of Mechanics Tianjin University School of Engineering Deakin University Research School of Engineering Australian National University

natural and artificial chiral materials such as deoxyribonucleic acid （DnA）, chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a Timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. The governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton＇s principle. The static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. This study is helpful not only for understanding the mechanical behavior of chiral materials such as DnA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

关键词： Timoshenko beam model Chiral material Chirality Deflection Microrotation

Quality assessment and hydrogeochemical characteristics of groundwater in Agastheeswaram taluk, Kanyakumari district, Tamil nadu, India

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Chinese Journal Of Geochemistry 2014年第3期33卷 221-235页

作者： Srinivas y Hudson Oliver D Stanley Raj A Chandrasekar n Centre for GeoTechnology Manonmaniam Sundaranar University Vel Tech Dr. RR & Dr. SR Technical University Avadi Chennai

The present study investigates the hydrogeochemical characteristics of groundwater quality in Agastheeswaram taluk of Kanyakumari district, Tamil nadu, India. A total of 69 groundwater samples were collected during pre- and post-monsoon periods of 2011–2012. The groundwater quality assessment has been carried out by evaluating the physicochemical parameters such as pH, EC, TDS, HCO3-, Cl-, SO42-, Ca2+, Mg2+, na+ and K+ for both the seasons. Based on these parameters, groundwater has been assessed in favor of its suitability for drinking and irrigation purpose. Dominant cations for both the seasons are in the order of na+ > Ca2+ > Mg2+ > K+ while the dominant anions for post monsoon and pre monsoon have the trends of Cl- > HCO3- > SO42- and HCO3- > Cl- > SO42-, respectively. Analytical results observed from various indices reveal that the groundwater quality is fairly good in some places. Analytical results of few samples show that they are severely polluted and incidentally found to be near the coasts, estuaries and salt pans in the study area. The Gibbs plot indicates that the majority of groundwater samples fall in rock dominant region, which indicates rock water interaction in the study area. The United States salinity(USSL) diagram shows that the groundwater is free from sodium hazards but the salinity hazard varies from low to very high throughout the study area. This reveals that the groundwater is moderately suitable for agricultural activities. The observed chemical variations in pre-monsoon and post-monsoon seasons may be the effect to rock-water interactions, ion-exchange reactions, and runoff of fertilizers from the surrounding agricultural lands.

关键词：地下水质量评价地下水水质水文特性马里印度水岩相互作用物理化学参数研究区域

RELATIOnSHIP AMOnG EVAPORATIOn FLUX OF GROUnDWATER, DEPTH OF WATER TABLE AnD nEGATIVE PRESSURE HEAD In BARE SOIL

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Journal of Hydrodynamics 2000年第4期12卷 52-58页

作者： Qian, J.Z. Zhu, X.y. Zhou, n.Q. Li, G.y. Dep. of Earth Sci. Nanjing Univ. Nanjing 210093 China

Evaporation of ground water is a part of moisture circulation in the field. And it is a main natural form in which water transmits from the ground water to the soil water and atmosphere water. According to the simulated experiments, we study the relationship among the evaporation, depth of groundwater table and negative pressure. By theoretical analysis of the experimental results, the main conclusions are drawn as follows. There are two abrupt points in every Q-H curve. The locations of the abrupt points are separately in step with the height of top of the capillary fringe and the height of maximal capillary rise in the soil section. When the depth of water table H is small, the evaporation flux of ground water is large. While the depth of water table exceeds the maximal capillary rise of media in vadose zone, the capillary rise breaks up and evaporation flux of groundwater is small. The water content ratio in ground surface tends to be zero and the surface of soil tends to be drought. These conclusions show that the maximal capillary rise of media in vadose zone is an important value in regulating rational depth of ground water to reduce the evaporation of ground water and to increase effective quantity of water resources. In the meantime, these conclusions are of important theoretical and practical significance to reduce the evaporation of ground water, to prevent and cure the salinization of soil, and to make full use of and protect water resources in the northern plains in China.

关键词： Capillarity Evaporation Soils

TRIBOLOGICAL AnD HIGH SPEED TURnInG PERFORMAnCE In Ti_(1-x)Al_(x)n COATInGS PREPARED By CLOSE-FIELD UnBALAnCED MAGnETROn SPUTTERInG

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Acta Metallurgica Sinica(English Letters) 2005年第3期18卷 254-260页

作者： P.W.Shum M.Escursell T.H.Wong K.y.Li Z.F.Zhou y.G.Shen Advanced Coatings Applied Research Laboratory(ACARL) Department of Manufacturi ng Engineering and Engineering ManagementCity University of Hong KongKowloonHong KongChina

Titanium-aluminium-nitride(Ti_(1-x)Al_(x)n)coatings were deposited by close-field un balanced magnetron sputtering on M42 steel substrates and WC-6wt%Co inserts at 450℃.The tribological behavior was analyzed by sliding against steel and WC-6wt%Co balls,while the turning performance was evaluated by a conventional tu rning machine at high cutting speeds without using *** the tribological tests,the formation of transfer layer and the variations of hardness of the co atings played an important role for sliding against steel *** the coating s sliding against WC-6wt%Co balls,the Ti-Al-n coatings showed a similar frictio n coefficient,but the Tin coating exhibited a lower *** difference could be explained by the tri-oxidation wear *** the turning tests,a super ior cutting performance of the coating was found at x=0.45,which endured 38 min utes before the tool flank wear reached the maximum value of 0.3mm,whereas only 20 minutes were endured for the Tin *** excellent performance of the c oatings in the turning tests could be explained by the enhanced mechanical prope rties and oxidation/diffusion resistance of the coatings.

关键词： hardness Ti-Al-n coating tribology turning test wear test

Phytotoxicity of cadmium on protein, proline and antioxidant enzyme activities in growing Arachis hypogaea L. seedlings

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Journal of Environmental Sciences 2008年第2期20卷 199-206页

作者： n Dinakar P C nagajyothi S Suresh y Udaykiran T Damodharam Department of Environmental Sciences Sri Venkateswara UniversityTirupatiAndhra Pradesh-517 502India.

Phytotoxicity of cadmium on growing Arachis hypogaea L. seedlings was studied. Seeds were exposed to 25, 50, and 100 μmol/L CdCl2 concentrations, for a period of 10, 15, 20 and 25 d. The extent of damage to chlorophyll, protein, proline, nitrate and nitrite reductase, antioxidant enzyme activity in leaves and roots were evaluated after 10 d of cadmium stress. The higher concentration of cadmium （100 μmol/L） resulted （leaves and roots） total chlorophyll 91.01%, protein 79.51%, 83.61%, nitrate reductase 79.39%, 80.72% and nitrite reductase 77.07%, 75.88% activity decreased with increase in cadmium concentrations and exposure periods. Cadmium caused significant changes in the activity of antioxidative enzymes. Contrastingly Cd treated plant tissues showed an increase in proline 159.87%, 239.6%, gluthion reductase （GR） 337.72%, 306.14%, superoxide disumutase （SOD） 688.56%, 381.72%, ascorbate peroxidase （APX） 226.47%, 252.14%, peroxidase （POD） 72.19%, 60.29% and catalase （CAT） 228.96%, 214.74% as compared to control. Cadmium stress caused a significant increase in the rate of SOD activity in leaves and roots of plant species. Results show the crop A. hypogaea is highly sensitive even at very low cadmium concentrations.

关键词： toxicological effects cadmium protein proline antioxidant enzymes

Magnetohydrodynamic flows tuning in a conduit with multiple channels under a magnetic field applied perpendicular to the plane of flow

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Journal of Hydrodynamics 2017年第2期29卷 332-343页

作者： y.Luo C.n.Kim M.Q.Zhu Department of Mechanical Engineering Graduate SchoolKyung Hee UniversityYong-inKorea Department of Mechanical Engineering College of EngineeringKyung Hee UniversityYong-inKorea

In this study, three-dimensional liquid-metal magnetohydrodynamic flows in a conduit with multiple channels under a uniform magnetic field are numerically investigated. The geometry of the conduit is of a four-parallel-channels system including one inflow channel and three outflow channels. The liquid-metal flows into the inflow channel, then turns through 180° in the transi- tion segment, finally flows into three different outflow channels. This kind of channel system can induce counter flow and co-flow, which is rarely investigated before though the conceptual designs of duct flow in the blanket have suggested this type of flow. A structured grid system is chosen after a series of mesh independence tests in the present study. The axial velocity in the side layer near the first partitioning wall, located between the inflow channel and the first outflow channel, is the highest with the lowest electric potential formed therein. The pressure almost linearly decreases in the main flow direction, except in the transition segment. Moreover, the pressure gradient in the first outflow channel is the largest among the three outflow channels. The interdependency of the current, fluid velocity, pressure, electric potential is examined in order to describe the electromagnetic characteristics of the liquid-metal flows.

关键词： Liquid-metal magnetohydrodynamics multiple channels

Asymptotics for filtration of polydisperse suspension with small impurities

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Applied Mathematics and Mechanics(English Edition) 2021年第1期42卷 109-126页

作者： L.I.KUZMInA y.V.OSIPOV T.n.GORBUnOVA Department of Applied Mathematics National Research University Higher School of EconomicsMoscow 101000Russia Department of Applied Mathematics Moscow State University of Civil Engineering(National Research University)Moscow 129337Russia

A model for deep bed filtration of a polydisperse suspension with small impurities in a porous medium is *** suspended particles move with the same velocity as the carrier water and get blocked in the pore throats due to the size-exclusion mechanism of particle retention.A solution of the model in the form of a traveling wave is *** global exact solution for a multiparticle filtration with one high concentration and several low concentrations of suspended particles is obtained in an explicit *** analytic solutions for a bidisperse suspension with large and small particles are *** profiles of the retained small particles change monotony with *** global asymptotics for the filtration of a polydisperse suspension with small kinetic rates is constructed in the whole filtration zone.

关键词： deep bed filtration suspension colloid porous medium particle size distribution analytical model

Microstructural characteristics and mechanical properties of the hot extruded Mg-Zn-y.nd alloys

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Journal of Materials Science & Technology 2021年第1期60卷 44-55页

作者： B.n.Du Z.y.Hu L.y.Sheng D.K.Xu y.X.Qiao B.J.Wang J.Wang y.F.Zheng T.F.Xi Shenzhen Institute Peking UniversityShenzhen 518057China Key Laboratory of nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Jiangsu University of Science and Technology Zhenjiang 212003China Shenzhen yezhan Electronics Co. LtdShenzhen 518110China

A new type of Mg-Zn-y.nd alloy for degradable orthopedic implants was *** the present study,the Zn and y content was adjusted and their influences on the microstructures and mechanical behaviors were discussed in *** results showed that the as-extruded Mg-Zn-y.nd alloys are mainly composed of fine dynamic recrystallized grains(DRXed grains),la rge unDRXed grains and linearly distributed secondary *** cha nge of Zn content exerts little influence on the grain structure of the extruded Mg-Zn-y.nd alloy,while the increase of y content would hinder the dynamic recrystallization process and the growth of the DRXed grains,thus the size and volume fraction of the equiaxed DRXed grains *** tensile and compressive properties are very little affected by Zn content because of the similar grain *** y content increases,the tensile yield strength(TyS) and ultimate strength(TUS) increase while the elongation decreases,this is caused by a combined strengthening effect of grain refinement,texture,precipitation and *** compressive yield strength(CyS) and ultimate strength(CUS) of Mg-Zn-y.nd alloy with diffe rent y content exhibit a similar tendency as the tensile test.

关键词： Mg-Zn-y.nd alloy Microstructure Tensile properties Compressive properties Basal texture Twin

FORMATIOn OF Fe-n COMPOUnDS By LASER nITRIDATIOn In An ATMOSPHERIC AMBIEnT

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Acta Metallurgica Sinica(English Letters) 2003年第2期16卷 139-144页

作者： y.L.y.ng F.J.Sun D.Zhang College of Science Northeastern UniversityShenyang 110004ChinaCollege of ScienceNortheastern UniversityShenyang 110004ChinaCollege of ScienceNortheastern UniversityShenyang 110004China

The formation of Fe-n compounds by laser nitriding in an atmospheric ambient was reported. By CW-CO2 laser irradiation on pure ferrite iron in the atmospheric ambient, Fe-n compounds (including Fe2n, .Fe3AT and Fe4n) are formed as a result of a laser-enhanced and temperature-enhanced reactions. The samples were analyzed with X-ray diffraction. It is found that the laser power density, scanning speed and nitrogen temperature are the main factors influencing the formation of Fe-n compounds. nitrogen can be activated by pre-heating at some temperature. nitrogen activation and sample surface melting by CW-CO2 laser greatly enhance the reaction between the sample surface and nitrogen beam. After annealing at 500℃for 3h, some Fe2n and Fe3n converted into more stable Fe4n.

关键词： laser nitriding nitride Fe-n compound