为了提高综合城市管廊泄漏定位精度,构建了一种通过采用波达时差(time difference of arrival,TDOA)法实现的交叉定位的处理方法,依次在各个泄漏区域建立阵列后再采集得到两组空间发送的方位数据,通过交叉处理方式计算空间交点以实现定...为了提高综合城市管廊泄漏定位精度,构建了一种通过采用波达时差(time difference of arrival,TDOA)法实现的交叉定位的处理方法,依次在各个泄漏区域建立阵列后再采集得到两组空间发送的方位数据,通过交叉处理方式计算空间交点以实现定位的过程。依此方法定位泄漏点时,位于有效信号检测范围时需适当增加阵列布放间距,获得更高精度的定位效果。该研究易于实现,对管道泄漏定位领域具有很好的推广价值。展开更多
A simulation of suspended sediment movement relating to tidal and wave forcing during a winter monsoon in November 1983 in the Huanghai and East China Seas continental shelf is attempted by using the model describing ...A simulation of suspended sediment movement relating to tidal and wave forcing during a winter monsoon in November 1983 in the Huanghai and East China Seas continental shelf is attempted by using the model describing the cohesive/non-cohesive sediment resus-pension generated by interactions between currents and waves.model simulation showed that sediment concentration was increased by resuspension at shallow depths during the strong storm conditions due to high bottom stress interacted between currents and waves. This result is in general agreement with observations in horizontal distribution of suspended sediment distribution. At three current meter mooring positions off the southern Shandong Peninsula resuspension occurred only at a depth of 22 m,nearest coastal position and at deeper parts at depths of 51 and 80 m wave-current interaction effects were not significant. It has shown that the present model simulation demonstrated the capability of reproduction of suspended sediment movement under wintertime extreme event reasonably well.展开更多
Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking（RVD） for an unmanned spacecraft when the autonomous system is failure or for guiding the chaser docking with an unco...Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking（RVD） for an unmanned spacecraft when the autonomous system is failure or for guiding the chaser docking with an uncooperative target.The theoretical model for analyzing the handling qualities in teleoperation RVD process is established based on the previous studies conducted by National Aeronautics and Space Administration（NASA）.The predictive factor is introduced to describe the pilot＇s predictive ability in the teleoperation tasks with time delay,which interrelates with the skills of a pilot and the predictive assist approach used in the tasks such as the predictive display method.Based on the semi-physical simulation system in our laboratory,900 experiments at two levels of time delay are carried out by 18 volunteers for validating the established model.The experimental results demonstrate the correctness of the theoretical model and indicate that a skilled pilot has a predictive ability of approximately 0.9 in teleoperation RVD tasks.The theoretical analysis shows that the handling qualities are greatly affected by the time delay and the predictive factor,and it is impossible to achieve a teleoperation RVD task for the skilled pilot when the time delay is larger than 9.0 s.展开更多
BACKGROUND:The use of livers from nonviable fetuses is particularly attractive for its potential to solve the current limitations of organ availability for the pediatric recipient.Therefore,it is essential to study th...BACKGROUND:The use of livers from nonviable fetuses is particularly attractive for its potential to solve the current limitations of organ availability for the pediatric recipient.Therefore,it is essential to study the feasibility of orthotopic fetal liver transplantation.METHOD:We measured the hepatic and extra-hepatic anatomical structures of fetal and neonatal lambs and established an orthotopic liver transplantation model of the fetal lamb.RESULTS:Mean weight of the liver of fetal lambs at 142 to 145 days gestation was 34.75 g and the mean diameter of the portal vein was 3.03 mm,the supra-hepatic vena cava was 5.88 mm,and the infra-hepatic vena cava was 4.00 mm,which matched the corresponding sizes in neonatal lambs aged up to 2 weeks.Using standard surgical procedures we completed the vascular inosculation of fetal liver.However,all the newborn lamb recipients survived less than 24 hours.CONCLUSIONS:Orthotopic transplantation of the fetal liver is anatomically and technically feasible.However,perioperative issues need to be resolved prior to clinical application.展开更多
With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable meth...With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time （HRT）, temperature, and effluent recycling on the treatment efficiency of an anaerobic filter （AF） reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91 ℃ ; and three effluent recycling ratios of 1：1, 1：2, and 2：1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for NH4-N, 19% to 23% for NO3-N, and 12% to 22% for TE In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for NH4-N, 30% to 34% for NO3-N, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2：1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.展开更多
文摘为了提高综合城市管廊泄漏定位精度,构建了一种通过采用波达时差(time difference of arrival,TDOA)法实现的交叉定位的处理方法,依次在各个泄漏区域建立阵列后再采集得到两组空间发送的方位数据,通过交叉处理方式计算空间交点以实现定位的过程。依此方法定位泄漏点时,位于有效信号检测范围时需适当增加阵列布放间距,获得更高精度的定位效果。该研究易于实现,对管道泄漏定位领域具有很好的推广价值。
文摘A simulation of suspended sediment movement relating to tidal and wave forcing during a winter monsoon in November 1983 in the Huanghai and East China Seas continental shelf is attempted by using the model describing the cohesive/non-cohesive sediment resus-pension generated by interactions between currents and waves.model simulation showed that sediment concentration was increased by resuspension at shallow depths during the strong storm conditions due to high bottom stress interacted between currents and waves. This result is in general agreement with observations in horizontal distribution of suspended sediment distribution. At three current meter mooring positions off the southern Shandong Peninsula resuspension occurred only at a depth of 22 m,nearest coastal position and at deeper parts at depths of 51 and 80 m wave-current interaction effects were not significant. It has shown that the present model simulation demonstrated the capability of reproduction of suspended sediment movement under wintertime extreme event reasonably well.
文摘Teleoperation rendezvous and docking can be used as a backup for autonomous rendezvous and docking（RVD） for an unmanned spacecraft when the autonomous system is failure or for guiding the chaser docking with an uncooperative target.The theoretical model for analyzing the handling qualities in teleoperation RVD process is established based on the previous studies conducted by National Aeronautics and Space Administration（NASA）.The predictive factor is introduced to describe the pilot＇s predictive ability in the teleoperation tasks with time delay,which interrelates with the skills of a pilot and the predictive assist approach used in the tasks such as the predictive display method.Based on the semi-physical simulation system in our laboratory,900 experiments at two levels of time delay are carried out by 18 volunteers for validating the established model.The experimental results demonstrate the correctness of the theoretical model and indicate that a skilled pilot has a predictive ability of approximately 0.9 in teleoperation RVD tasks.The theoretical analysis shows that the handling qualities are greatly affected by the time delay and the predictive factor,and it is impossible to achieve a teleoperation RVD task for the skilled pilot when the time delay is larger than 9.0 s.
基金supported by a grant from the Science and Technology Commission of Shanghai Municipality(07-JC14045)
文摘BACKGROUND:The use of livers from nonviable fetuses is particularly attractive for its potential to solve the current limitations of organ availability for the pediatric recipient.Therefore,it is essential to study the feasibility of orthotopic fetal liver transplantation.METHOD:We measured the hepatic and extra-hepatic anatomical structures of fetal and neonatal lambs and established an orthotopic liver transplantation model of the fetal lamb.RESULTS:Mean weight of the liver of fetal lambs at 142 to 145 days gestation was 34.75 g and the mean diameter of the portal vein was 3.03 mm,the supra-hepatic vena cava was 5.88 mm,and the infra-hepatic vena cava was 4.00 mm,which matched the corresponding sizes in neonatal lambs aged up to 2 weeks.Using standard surgical procedures we completed the vascular inosculation of fetal liver.However,all the newborn lamb recipients survived less than 24 hours.CONCLUSIONS:Orthotopic transplantation of the fetal liver is anatomically and technically feasible.However,perioperative issues need to be resolved prior to clinical application.
基金supported by the National Natural Science Foundation of China(Grant No.51078074)the Key Project of the Chinese Ministry of Education(Grant No.308010)
文摘With rural population expansion and improvement of the socio-economic standard of living, treatment of rural domestic wastewater has rapidly become a major aspect of environmental concern. Selection of a suitable method for treatment of rural domestic wastewater depends on its efficiency, simplicity, and cost-effectiveness. This study investigated the effects of hydraulic retention time （HRT）, temperature, and effluent recycling on the treatment efficiency of an anaerobic filter （AF） reactor. The first round of experimental operations was run for three months with HRTs of one, two, and three days, temperatures of 18℃, 21℃, and 24℃, and no effluent recycling. The second round of experimental operations was conducted for another three months with HRTs of three and four days; temperatures of 30.67℃, 30.57℃, and 26.91 ℃ ; and three effluent recycling ratios of 1：1, 1：2, and 2：1. The first round of operations showed removal rates of 32% to 44% for COD, 30% to 35% for TN, 32% to 36% for NH4-N, 19% to 23% for NO3-N, and 12% to 22% for TE In the second round of operations, the removal rates varied from 75% to 81% for COD, 35% to 41% for TN, 31% to 39% for NH4-N, 30% to 34% for NO3-N, and 41% to 48% for TP. The average gas production rates were 6.72 L/d and 7.26 L/d for the first and second rounds of operations, respectively. The gas production rate increased in the second round of operations as a result of applied effluent recycling. The best removal efficiency was obtained for an optimum HRT of three days, a temperature of 30℃, and an effluent recycling ratio of 2：1. The results show that the removal efficiency of the AF reactor was affected by HRT, temperature, and effluent recycling.
