High-speed sliding often leads to catastrophic landslides,many of which,in the initial sliding phase before disintegration,experience a friction-induced thermal pressurization effect in the bottom shear band,accelerat...High-speed sliding often leads to catastrophic landslides,many of which,in the initial sliding phase before disintegration,experience a friction-induced thermal pressurization effect in the bottom shear band,accelerating the movement of the overlying sliding mass.To quantitatively investigate this complex multiphysical phenomenon,we established a set of equations that describe the variations in temperature and excess pore pressure within the shear band,as well as the conservation of momentum equation for the overlying sliding mass.With a simplified landslide model,we investigated the variations of temperature and excess pore pressure within the shear band and their impacts on the velocity of the overlying sliding mass.On this basis,we studied the impact of seven key parameters on the maximum temperature and excess pore pressure in the shear band,as well as the impact on the velocity of the overlying sliding mass.The simulation results of the standard model show that the temperature and excess pore pressure in the shear band are significantly higher than those in the adjacent areas,and reach the maximum values in the center.Within a few seconds after the start,the maximum excess pore pressure in the shear zone is close to the initial stress,and the shear strength loss rate exceeds 90%.The thermal pressurization mechanism significantly increases the velocity of the overlying sliding mass.The results of parameter sensitivity analysis show that the thermal expansion coefficient has the most significant impact on the temperature and excess pore pressure in the shear band,and the sliding surface dip angle has the most significant impact on the velocity of the overlying sliding mass.The results of this study are of great significance for clarifying the mechanism of thermal pressurization-induced high-speed sliding.展开更多
In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impeller...In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impellers. KHX impeller is an efficient axial flow impeller, which provides large onflow diffusivity and low shear force. In this work, the KHX impeller was applied in a lower-shear bioreactor and the performance of this reactor was evaluated and compared with that of the PBTD impeller. The experimental results show that the KHX impeller can disperse gas at lower power consumption and gives greater gas–liquid volumetric mass transfer coefficients than PBTD at the same power consumption. An empirical correlation for evaluating the mass transfer coefficient of the KHX impeller in the bioreactor is presented to provide reference for its industrial application.展开更多
The influence of the dispersion and uncertainty of the dynamic shear wave velocity and Poisson＇s ratio of soil in a hard rock site was investigated on the seismic response of reactor building structure. The analysis ...The influence of the dispersion and uncertainty of the dynamic shear wave velocity and Poisson＇s ratio of soil in a hard rock site was investigated on the seismic response of reactor building structure. The analysis is performed by considering the soil-structure interaction effects and based on the model of the reactor building in a typical pressurized water reactor nuclear power plant （NPP）. The numerical results show that for the typical floor selected, while the relative increment ratio of the dynamic shear wave velocity varies from -30% to 30% compared to the basis of 1 930 m/s, the relative variation of the horizontal response spectra peak value lies in the scope of ±10% for the internal structure, and the relative variation of the frequency corresponding to the spectra peak is 0.0% in most cases. The relative variation of the vertical response spectra peak value lies in the scope of - 10% to 22%, and the relative variation of the frequency corresponding to the Spectra peak lies in the scope of - 22% to 4%. The analysis indicates that the dynamic shear wave velocity and the Poisson＇s ratio of the rock would affect the seismic response of structure and the soil-structure interaction effects should be considered in seismic analysis and design of NPP even for a hard rock site.展开更多
An approach to measure a high-dynamic two-dimensional(2 D) temperature field using a high-speed quadriwave lateral shearing interferometer(QWLSI) is proposed. The detailed theoretical derivation to express the wavefro...An approach to measure a high-dynamic two-dimensional(2 D) temperature field using a high-speed quadriwave lateral shearing interferometer(QWLSI) is proposed. The detailed theoretical derivation to express the wavefront reconstruct principle of the proposed method is presented. The comparison experiment with thermocouples shows that the temperature field measurement using QWLSI has a precision of ±0.5 °C. An experiment for measuring the highdynamic temperature field generated by an electrical heater is carried out. A 200 frame rate temperature field video with 512 × 512 resolution is obtained finally. Experimental results show that the temperature field measurement system using a QWLSI has the advantage of high sensitivity and high resolution.展开更多
High-speed machining(HSM) has been studied for several decades and has potential application in various industries, including the automobile and aerospace industries. However,the underlying mechanisms of HSM have not ...High-speed machining(HSM) has been studied for several decades and has potential application in various industries, including the automobile and aerospace industries. However,the underlying mechanisms of HSM have not been formally reviewed thus far. This article focuses on the solid mechanics framework of adiabatic shear band(ASB) onset and material metallurgical microstructural evolutions in HSM. The ASB onset is described using partial differential systems. Several factors in HSM were considered in the systems, and the ASB onset conditions were obtained by solving these systems or applying the perturbation method to the systems. With increasing machining speed, an ASB can be depressed and further eliminated by shock pressure. The damage observed in HSM exhibits common features. Equiaxed fine grains produced by dynamic recrystallization widely cause damage to ductile materials, and amorphization is the common microstructural evolution in brittle materials. Based on previous studies, potential mechanisms for the phenomena in HSM are proposed. These include the thickness variation of the white layer of ductile materials. These proposed mechanisms would be beneficial to deeply understanding the various phenomena in HSM.展开更多
A 500 kV high-voltage AC fault current limiter(FCL)based on a high coupled split reactor(HCSR)is pro-posed by the National key R&D project team.Low impedance under normal conditions and high impedance under short-...A 500 kV high-voltage AC fault current limiter(FCL)based on a high coupled split reactor(HCSR)is pro-posed by the National key R&D project team.Low impedance under normal conditions and high impedance under short-circuit conditions are accomplished by the cooperation of HCSR and high-speed switches.High-speed switches play an important role in current limiting processes,thus interruption characteristics of the high-speed switch in the 500 kV FCL are studied in this paper.The simulation model of the FCL and the external equivalent power grid are established.The short-circuit current and recovery voltage characteristics of the high-speed switch in FCL are simulated.The results show that maximum DC component of the short-circuit current of the high-speed switch reaches 91%,the maximum peak value is 118 kA,and the longest arcing time is 14.8 ms.There is a discontinuity in the curve of the short-circuit current peak and arcing time as a function of the short-circuit occurrence time;the peak recovery voltage of a single break of the high-speed switch has a maximum value of 87.5 kV under a three-phase ungrounded short-circuit condition,and the rate of rise of recovery voltage is o.22 kV/s.The recovery voltage peak shows a period change with the short-circuit occurrence time,and the period is 10 ms.The effects of the shunt capacitor value and short-circuit ground resistance on the recovery voltage of high-speed switching are also studied.The research can be used for reference by R&D personnel and testersof500kVFCLs.Index Terms-Fault current limiter(FCL),high coupled split reactor(HCSR),high-speed switch,interruption characteristics,short circuit current.展开更多
基金financed by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(No.SKLGP2023K022)the Natural Science Foundation of Hubei Province(No.2022CFA011).
文摘High-speed sliding often leads to catastrophic landslides,many of which,in the initial sliding phase before disintegration,experience a friction-induced thermal pressurization effect in the bottom shear band,accelerating the movement of the overlying sliding mass.To quantitatively investigate this complex multiphysical phenomenon,we established a set of equations that describe the variations in temperature and excess pore pressure within the shear band,as well as the conservation of momentum equation for the overlying sliding mass.With a simplified landslide model,we investigated the variations of temperature and excess pore pressure within the shear band and their impacts on the velocity of the overlying sliding mass.On this basis,we studied the impact of seven key parameters on the maximum temperature and excess pore pressure in the shear band,as well as the impact on the velocity of the overlying sliding mass.The simulation results of the standard model show that the temperature and excess pore pressure in the shear band are significantly higher than those in the adjacent areas,and reach the maximum values in the center.Within a few seconds after the start,the maximum excess pore pressure in the shear zone is close to the initial stress,and the shear strength loss rate exceeds 90%.The thermal pressurization mechanism significantly increases the velocity of the overlying sliding mass.The results of parameter sensitivity analysis show that the thermal expansion coefficient has the most significant impact on the temperature and excess pore pressure in the shear band,and the sliding surface dip angle has the most significant impact on the velocity of the overlying sliding mass.The results of this study are of great significance for clarifying the mechanism of thermal pressurization-induced high-speed sliding.
基金Supported by the National Basic Research Program of China(2010CB630904)the National Natural Science Foundation of China(21276004,20990224)+1 种基金the National Natural Science Fund for Distinguished Young Scholars(21025627)the National High Technology Research and Development Program of China(2012AA061503)
文摘In our previous work, a low-shear stirred bioreactor was explored. With a pitched blade turbine impeller downflow(PBTD) used, the shear stress generated is high compared with that in some low shear axial flow impellers. KHX impeller is an efficient axial flow impeller, which provides large onflow diffusivity and low shear force. In this work, the KHX impeller was applied in a lower-shear bioreactor and the performance of this reactor was evaluated and compared with that of the PBTD impeller. The experimental results show that the KHX impeller can disperse gas at lower power consumption and gives greater gas–liquid volumetric mass transfer coefficients than PBTD at the same power consumption. An empirical correlation for evaluating the mass transfer coefficient of the KHX impeller in the bioreactor is presented to provide reference for its industrial application.
基金SUPPORTED BY NATIONAL NATURAL SCIENCE FOUNDATION FOR DISTINGUISHED YOUNG SCHOLARS OF CHINA (NO. 50425824).
文摘The influence of the dispersion and uncertainty of the dynamic shear wave velocity and Poisson＇s ratio of soil in a hard rock site was investigated on the seismic response of reactor building structure. The analysis is performed by considering the soil-structure interaction effects and based on the model of the reactor building in a typical pressurized water reactor nuclear power plant （NPP）. The numerical results show that for the typical floor selected, while the relative increment ratio of the dynamic shear wave velocity varies from -30% to 30% compared to the basis of 1 930 m/s, the relative variation of the horizontal response spectra peak value lies in the scope of ±10% for the internal structure, and the relative variation of the frequency corresponding to the spectra peak is 0.0% in most cases. The relative variation of the vertical response spectra peak value lies in the scope of - 10% to 22%, and the relative variation of the frequency corresponding to the Spectra peak lies in the scope of - 22% to 4%. The analysis indicates that the dynamic shear wave velocity and the Poisson＇s ratio of the rock would affect the seismic response of structure and the soil-structure interaction effects should be considered in seismic analysis and design of NPP even for a hard rock site.
基金supported by the National Natural Science Foundation of China(No.11603024)
文摘An approach to measure a high-dynamic two-dimensional(2 D) temperature field using a high-speed quadriwave lateral shearing interferometer(QWLSI) is proposed. The detailed theoretical derivation to express the wavefront reconstruct principle of the proposed method is presented. The comparison experiment with thermocouples shows that the temperature field measurement using QWLSI has a precision of ±0.5 °C. An experiment for measuring the highdynamic temperature field generated by an electrical heater is carried out. A 200 frame rate temperature field video with 512 × 512 resolution is obtained finally. Experimental results show that the temperature field measurement system using a QWLSI has the advantage of high sensitivity and high resolution.
基金support of the Shenzhen Science and Technology Innovation Commission under Project Numbers KQTD20190929172505711,JSGG20210420091802007, and JCYJ20210324115413036Guangdong Provincial Department of Science and Technology under Project Number K22333004。
文摘High-speed machining(HSM) has been studied for several decades and has potential application in various industries, including the automobile and aerospace industries. However,the underlying mechanisms of HSM have not been formally reviewed thus far. This article focuses on the solid mechanics framework of adiabatic shear band(ASB) onset and material metallurgical microstructural evolutions in HSM. The ASB onset is described using partial differential systems. Several factors in HSM were considered in the systems, and the ASB onset conditions were obtained by solving these systems or applying the perturbation method to the systems. With increasing machining speed, an ASB can be depressed and further eliminated by shock pressure. The damage observed in HSM exhibits common features. Equiaxed fine grains produced by dynamic recrystallization widely cause damage to ductile materials, and amorphization is the common microstructural evolution in brittle materials. Based on previous studies, potential mechanisms for the phenomena in HSM are proposed. These include the thickness variation of the white layer of ductile materials. These proposed mechanisms would be beneficial to deeply understanding the various phenomena in HSM.
基金supported by the National Key R&D Program of China(2018YFB0904300)。
文摘A 500 kV high-voltage AC fault current limiter(FCL)based on a high coupled split reactor(HCSR)is pro-posed by the National key R&D project team.Low impedance under normal conditions and high impedance under short-circuit conditions are accomplished by the cooperation of HCSR and high-speed switches.High-speed switches play an important role in current limiting processes,thus interruption characteristics of the high-speed switch in the 500 kV FCL are studied in this paper.The simulation model of the FCL and the external equivalent power grid are established.The short-circuit current and recovery voltage characteristics of the high-speed switch in FCL are simulated.The results show that maximum DC component of the short-circuit current of the high-speed switch reaches 91%,the maximum peak value is 118 kA,and the longest arcing time is 14.8 ms.There is a discontinuity in the curve of the short-circuit current peak and arcing time as a function of the short-circuit occurrence time;the peak recovery voltage of a single break of the high-speed switch has a maximum value of 87.5 kV under a three-phase ungrounded short-circuit condition,and the rate of rise of recovery voltage is o.22 kV/s.The recovery voltage peak shows a period change with the short-circuit occurrence time,and the period is 10 ms.The effects of the shunt capacitor value and short-circuit ground resistance on the recovery voltage of high-speed switching are also studied.The research can be used for reference by R&D personnel and testersof500kVFCLs.Index Terms-Fault current limiter(FCL),high coupled split reactor(HCSR),high-speed switch,interruption characteristics,short circuit current.
