The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are...The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are studied for the response of a Timoshenko beam supported by a nonlinear foundation. The nonlinear Pasternak foundation is assumed to be cubic. Therefore, the effects of the shear deformable beams and the shear deformation of foundations are considered at the same time. The Galerkin method is utilized for discretizing the nonlinear partial dif- ferential governing equations of the forced vibration. The dynamic responses of Timoshenko beams are determined via the fourth-order Runge-Kutta method. Moreover, the effects of different truncation terms on the dynamic responses of a Timoshenko beam resting on a complex foundation are discussed. The numerical investigations shows that the dynamic response of Timoshenko beams supported by elastic foundations needs super high-order modes. Furthermore, the system parameters are compared to determine the dependence of the convergences of the Galerkin method.展开更多
The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the ...The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the two coupled governing equations of pore-water and pore-air pressures into an equivalent set of partial differential equations （PDFs）, which are easily solved by the Laplace transform method. Then, the pore-water pressure, pore-air pressure, and soil settlement are obtained in the Laplace domain. The Crump method is adopted to perform the inverse Laplace transform in order to obtain the semi-analytical solutions in the time domain. It is shown that the proposed solutions are more applicable to various types of boundary conditions and agree well with the existing solutions from the literature. Several numerical examples are provided to investigate the consolidation behavior of an unsaturated single-layer soil with single, double, mixed, and semi-permeable drainage boundaries. The changes in the pore-air and pore-water pres- sures and the soil settlement with the time factor at different values of the semi-permeable drainage boundary parameters are illustrated. In addition, parametric studies are con- ducted on the pore-air and pore-water pressures at different ratios （the air permeability coefficient to the water permeability coefficient） and depths.展开更多
Carbothermal reduction and nitridation （CRN） of zircon （ ZrSiO4 ） permits obtaining diffbrent composites of oxides and nitrides such as ZrO2 -Si2N2O and ZrN - Si3N4. The effects tf technological parameters （ carb...Carbothermal reduction and nitridation （CRN） of zircon （ ZrSiO4 ） permits obtaining diffbrent composites of oxides and nitrides such as ZrO2 -Si2N2O and ZrN - Si3N4. The effects tf technological parameters （ carbon source, reaction temperature, and carbon con.tent ） on the reaction rate and product phase composition of CRN of zircon were investigated by TGA and XRD. The resuhs show that： （1） carbon source is an important factor for a rapid reaction, and actiwtted carbon is chosen as the carbon source considering the expect products and reaction rate ; （ 2 ） reaction tetnperature has vital effect on reaction rate and product. In, case of carbon content above 20% , the zircon phase and m-ZrO2 phase decrease with increasing temperature, while the ZF7N8O4 phase increases firstly and then decreases, and the ZrN phase increases continually; （3） different carbon contents result in different reaction products. The higher the carbon content, the lower the starting temperature for the CRN of zircon.展开更多
Effects of electrolytes on the oxidation of carbon fibreswere investigated by ion chromatography and cyclic vol-tammogram measurement.The results indicate that theconcentration of nitrate ion decreases with increase o...Effects of electrolytes on the oxidation of carbon fibreswere investigated by ion chromatography and cyclic vol-tammogram measurement.The results indicate that theconcentration of nitrate ion decreases with increase oftreatment time,and the concentration of phosphate ionkeeps a constant in the process of electrochemical oxida-tion.Nitrate ions have more effective electrochemical ox-idation ability than other anions.The mechanism of elec-trochemical oxidation of carbon fibres was suggested.展开更多
The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had sm...The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had smooth surfaces. The morphology of the whiskers were studied by means of SEM and TEM. The AlN whiskers were grown via vapor-solid (VS) mechanism.展开更多
目的:检测大蒜多糖对大鼠嗜铬瘤细胞株(pheochromocytom a cells,PC12)增殖的影响和对经过氧化氢(H2O2)诱导损伤的PC12细胞的保护作用。方法:应用四氮唑蓝(MTT)比色法检测大蒜多糖对细胞增殖的影响;建立H2O2致PC12细胞损伤模型,于倒置...目的:检测大蒜多糖对大鼠嗜铬瘤细胞株(pheochromocytom a cells,PC12)增殖的影响和对经过氧化氢(H2O2)诱导损伤的PC12细胞的保护作用。方法:应用四氮唑蓝(MTT)比色法检测大蒜多糖对细胞增殖的影响;建立H2O2致PC12细胞损伤模型,于倒置相差显微镜下观察细胞形态的变化;化学比色法测定乳酸脱氢酶(LDH)释放量及细胞内和细胞培养上清液中丙二醛(MDA)含量和超氧化物歧化酶(SOD)的活性。结果:大蒜多糖各剂量组均能显著提高正常PC12细胞的存活数,大蒜多糖各剂量组均能有效对抗由25μmol/L H2O2引起的细胞存活率下降和细胞凋亡,可明显改善细胞形态的衰变,显著降低LDH释放量和细胞培养液及细胞内的MDA含量,提高SOD活性。结论:大蒜多糖促进正常PC12细胞增殖;且对H2O2诱导PC12细胞损伤具有保护作用,其作用机制可能与提高PC12细胞的抗氧化能力有关。展开更多
基金supported by the State Key Program of National Natural Science Foundation of China (10932006 and 11232009)Innovation Program of Shanghai Municipal Education Commission (12YZ028)
文摘The present paper investigates the dynamic response of finite Timoshenko beams resting on a sixparameter foundation subjected to a moving load. It is for the first time that the Galerkin method and its convergence are studied for the response of a Timoshenko beam supported by a nonlinear foundation. The nonlinear Pasternak foundation is assumed to be cubic. Therefore, the effects of the shear deformable beams and the shear deformation of foundations are considered at the same time. The Galerkin method is utilized for discretizing the nonlinear partial dif- ferential governing equations of the forced vibration. The dynamic responses of Timoshenko beams are determined via the fourth-order Runge-Kutta method. Moreover, the effects of different truncation terms on the dynamic responses of a Timoshenko beam resting on a complex foundation are discussed. The numerical investigations shows that the dynamic response of Timoshenko beams supported by elastic foundations needs super high-order modes. Furthermore, the system parameters are compared to determine the dependence of the convergences of the Galerkin method.
基金Project supported by the National Natural Science Foundation of China(Nos.41630633 and11672172)
文摘The semi-analytical solutions to Fredlund and Hasan＇s one-dimensional （1D） consolidation for unsaturated soils with a semi-permeable drainage boundary are pre- seated. Two variables are introduced to transform the two coupled governing equations of pore-water and pore-air pressures into an equivalent set of partial differential equations （PDFs）, which are easily solved by the Laplace transform method. Then, the pore-water pressure, pore-air pressure, and soil settlement are obtained in the Laplace domain. The Crump method is adopted to perform the inverse Laplace transform in order to obtain the semi-analytical solutions in the time domain. It is shown that the proposed solutions are more applicable to various types of boundary conditions and agree well with the existing solutions from the literature. Several numerical examples are provided to investigate the consolidation behavior of an unsaturated single-layer soil with single, double, mixed, and semi-permeable drainage boundaries. The changes in the pore-air and pore-water pres- sures and the soil settlement with the time factor at different values of the semi-permeable drainage boundary parameters are illustrated. In addition, parametric studies are con- ducted on the pore-air and pore-water pressures at different ratios （the air permeability coefficient to the water permeability coefficient） and depths.
基金the Natural Science Foundation of The Education Department of Henan Province,No.2011B430011the SRTP of Henan University of Science and Technology
文摘Carbothermal reduction and nitridation （CRN） of zircon （ ZrSiO4 ） permits obtaining diffbrent composites of oxides and nitrides such as ZrO2 -Si2N2O and ZrN - Si3N4. The effects tf technological parameters （ carbon source, reaction temperature, and carbon con.tent ） on the reaction rate and product phase composition of CRN of zircon were investigated by TGA and XRD. The resuhs show that： （1） carbon source is an important factor for a rapid reaction, and actiwtted carbon is chosen as the carbon source considering the expect products and reaction rate ; （ 2 ） reaction tetnperature has vital effect on reaction rate and product. In, case of carbon content above 20% , the zircon phase and m-ZrO2 phase decrease with increasing temperature, while the ZF7N8O4 phase increases firstly and then decreases, and the ZrN phase increases continually; （3） different carbon contents result in different reaction products. The higher the carbon content, the lower the starting temperature for the CRN of zircon.
文摘Effects of electrolytes on the oxidation of carbon fibreswere investigated by ion chromatography and cyclic vol-tammogram measurement.The results indicate that theconcentration of nitrate ion decreases with increase oftreatment time,and the concentration of phosphate ionkeeps a constant in the process of electrochemical oxida-tion.Nitrate ions have more effective electrochemical ox-idation ability than other anions.The mechanism of elec-trochemical oxidation of carbon fibres was suggested.
文摘The aluminum nitride whiskers were synthesized by the nitridation of Al/AlN powders in a flowing nitrogen atmosphere. The whiskers were about 0. 5祄 in diameter and 10~20祄 in length, and they were straight and had smooth surfaces. The morphology of the whiskers were studied by means of SEM and TEM. The AlN whiskers were grown via vapor-solid (VS) mechanism.
文摘目的:检测大蒜多糖对大鼠嗜铬瘤细胞株(pheochromocytom a cells,PC12)增殖的影响和对经过氧化氢(H2O2)诱导损伤的PC12细胞的保护作用。方法:应用四氮唑蓝(MTT)比色法检测大蒜多糖对细胞增殖的影响;建立H2O2致PC12细胞损伤模型,于倒置相差显微镜下观察细胞形态的变化;化学比色法测定乳酸脱氢酶(LDH)释放量及细胞内和细胞培养上清液中丙二醛(MDA)含量和超氧化物歧化酶(SOD)的活性。结果:大蒜多糖各剂量组均能显著提高正常PC12细胞的存活数,大蒜多糖各剂量组均能有效对抗由25μmol/L H2O2引起的细胞存活率下降和细胞凋亡,可明显改善细胞形态的衰变,显著降低LDH释放量和细胞培养液及细胞内的MDA含量,提高SOD活性。结论:大蒜多糖促进正常PC12细胞增殖;且对H2O2诱导PC12细胞损伤具有保护作用,其作用机制可能与提高PC12细胞的抗氧化能力有关。
