An analytic solution to three-dimensional problem of transient contact dynamics is developed, and a generalized Galin’s theorem is proved. Based on the theorem, contact displacements can be determined analytically wh...An analytic solution to three-dimensional problem of transient contact dynamics is developed, and a generalized Galin’s theorem is proved. Based on the theorem, contact displacements can be determined analytically when the given contact stresses are some quite general functions; in contrast to this, one can readily evaluate the corresponding contact stresses in analytic version when some quite general displacements are prescribed. The quite general form mentioned above means the prescribed quantities are any polynomials of x and y and any transient function of time. Numerical results for the contact displacements-time variation dearly demonstrate the effect of inertia induced by the dynamic stress.展开更多
The transient response to longitudinal impact of flexible rods with Hertz contact is closely related to the extent of deformations with different impact parameters. By means of LS-DYNA, for different radius and differ...The transient response to longitudinal impact of flexible rods with Hertz contact is closely related to the extent of deformations with different impact parameters. By means of LS-DYNA, for different radius and different speeds, the longitudinal impact of a hammer with a rounded end on a drill rod is numerically simulated in this article. Simulations demonstrate that there is an obvious dif-ference between analytical solution and numerical solution on condition of short curvature radius. In the circumstance contact pressure increases, the boundary of the yield zone exceeds that of the contact zone, and the significant plastic deformation reduces the intensity of contact pressure pulse. Contact force-time curves in loading and unloading phases shift down. The numerical solution is in good agree-ment with analytical solution on condition of large curvature radius and impact speeds. The deforma-tion of yield region is constrained by the surrounding elastic region and no significant plastic deforma-tion appears.展开更多
Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep...Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy （DLTS）, we study the deep levels in CdS/CdTe thin film solar cells with Te：Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at Ev＋0.128~eV, originates from the vacancy of Cd （VCd. The electron trap E1, found at Ec-0.178~eV, is considered to be correlated with the interstitial Cui= in CdTe.展开更多
We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 104...We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 1045 mm. We applied a new analysis method for the steam state equation to analyze the molar quantity change in steam over the course of the experiment and determined the transient steam variation. We also investigated the influence of flow rates and temperatures ofcooling water on the efficiency ofsteam condensation. Our experimental results show that appropriate increasing of the cooling water flow rate can significantly accelerate the steam condensation. We achieved a rapid increase in the total volumetric heat transfer coefficient by increasing the flow rate of cooling water, which indicated a higher thermal convection between the steam and the cooling water with higher flow rates. We found that the temperature ofcooling water did not play an important role on steam condensation. This method was confirmed to be effective for rapid recovering ofsteam.展开更多
文摘An analytic solution to three-dimensional problem of transient contact dynamics is developed, and a generalized Galin’s theorem is proved. Based on the theorem, contact displacements can be determined analytically when the given contact stresses are some quite general functions; in contrast to this, one can readily evaluate the corresponding contact stresses in analytic version when some quite general displacements are prescribed. The quite general form mentioned above means the prescribed quantities are any polynomials of x and y and any transient function of time. Numerical results for the contact displacements-time variation dearly demonstrate the effect of inertia induced by the dynamic stress.
基金supported by the National Natural Science Foundation of China (No. 50475056)
文摘The transient response to longitudinal impact of flexible rods with Hertz contact is closely related to the extent of deformations with different impact parameters. By means of LS-DYNA, for different radius and different speeds, the longitudinal impact of a hammer with a rounded end on a drill rod is numerically simulated in this article. Simulations demonstrate that there is an obvious dif-ference between analytical solution and numerical solution on condition of short curvature radius. In the circumstance contact pressure increases, the boundary of the yield zone exceeds that of the contact zone, and the significant plastic deformation reduces the intensity of contact pressure pulse. Contact force-time curves in loading and unloading phases shift down. The numerical solution is in good agree-ment with analytical solution on condition of large curvature radius and impact speeds. The deforma-tion of yield region is constrained by the surrounding elastic region and no significant plastic deforma-tion appears.
基金supported by the National Natural Science Foundation of China (Grant No. 60506004)the National High Technology Research and Development Program of China (Grant No. 2003AA513010)
文摘Deep levels in Cds/CdTe thin film solar cells have a potent influence on the electrical property of these devices. As an essential layer in the solar cell device structure, back contact is believed to induce some deep defects in the CdTe thin film. With the help of deep level transient spectroscopy （DLTS）, we study the deep levels in CdS/CdTe thin film solar cells with Te：Cu back contact. One hole trap and one electron trap are observed. The hole trap H1, localized at Ev＋0.128~eV, originates from the vacancy of Cd （VCd. The electron trap E1, found at Ec-0.178~eV, is considered to be correlated with the interstitial Cui= in CdTe.
文摘We conducted a transient experimental investigation of steam–water direct contact condensation in the absence of noncondensible gas in a laboratory-scale column with the inner diameter of 325 mm and the height of 1045 mm. We applied a new analysis method for the steam state equation to analyze the molar quantity change in steam over the course of the experiment and determined the transient steam variation. We also investigated the influence of flow rates and temperatures ofcooling water on the efficiency ofsteam condensation. Our experimental results show that appropriate increasing of the cooling water flow rate can significantly accelerate the steam condensation. We achieved a rapid increase in the total volumetric heat transfer coefficient by increasing the flow rate of cooling water, which indicated a higher thermal convection between the steam and the cooling water with higher flow rates. We found that the temperature ofcooling water did not play an important role on steam condensation. This method was confirmed to be effective for rapid recovering ofsteam.
