通过中美交流互访、水资源研究现状调查和2007-2017年Web of Science中有关水资源领域的文献统计分析,对比了中美水资源研究在研究机构、经费来源、研究领域、代表性人物等方面在现阶段所存在的差异,归纳总结了中美水资源研究的最新进展...通过中美交流互访、水资源研究现状调查和2007-2017年Web of Science中有关水资源领域的文献统计分析,对比了中美水资源研究在研究机构、经费来源、研究领域、代表性人物等方面在现阶段所存在的差异,归纳总结了中美水资源研究的最新进展:总体上,中国从事水资源研究的人员和机构众多,研究领域更宽泛,中国水资源侧重江河水利规划、水资源的综合高效利用、快速变化条件下人类活动对水资源水环境的影响的研究;相对而言,美国从事水资源研究的人员和机构相对偏少,研究领域相对较新,研究尺度较大,学科交叉性强,相对更成熟,研究程度更高,往往从全球的角度来研究水,更加注重水法水权、水资源的评价、特殊水资源的规划与利用、水资源的保护、水资源的生态补偿、水资源的处理费用、与水有关的工程与环境相协调等综合研究领域.最后,本研究展望了中美双方在水资源研究领域的发展趋势及带给我们的启示.展开更多
The dimension number of the centralized Kalman filter (CKF) for the rapid transfer alignment (TA) is as high as 21 if the aircraft wing flexure motion is considered in the rapid TA. The 21-dimensional CKF brings the c...The dimension number of the centralized Kalman filter (CKF) for the rapid transfer alignment (TA) is as high as 21 if the aircraft wing flexure motion is considered in the rapid TA. The 21-dimensional CKF brings the calculation burden on the computer and the difficulty to meet a high filtering updating rate desired by rapid TA. The federated Kalman filter (FKF) for the rapid TA is proposed to solve the dilemma. The structure and the algorithm of the FKF, which can perform parallel computation and has less calculation burden, are designed.The wing flexure motion is modeled, and then the 12-order velocity matching local filter and the 15-order attitud ematching local filter are devised. Simulation results show that the proposed EKE for the rapid TA almost has the same performance as the CKF. Thus the calculation burden of the proposed FKF for the rapid TA is markedly decreased.展开更多
Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of res...Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of residual chlorine decay in water pipe has been developed, given the consumption of chlorine in reactions with chemicals in bulk water, bio films on pipe wall, in corrosion process, and the mass transport of chlorine from bulk water to pipe wall. Analytical methods of the flow path from water sources to the observed point and the water age of every observed node were proposed. Model is used to predict the decay of residual chlorine in an actual distribution system. Good agreement between calculated and measured values was obtained.展开更多
Diamond-like carbon(DLC)films were prepared on Si(100) substrates by ion implantation from an electron cyclotron resonance microwave plasma source.During the implantation,650W microwave power was used to produce disch...Diamond-like carbon(DLC)films were prepared on Si(100) substrates by ion implantation from an electron cyclotron resonance microwave plasma source.During the implantation,650W microwave power was used to produce discharge plasma with methane as working gas,and-20KV voltage pulses were applied to the substrate holder to accelerate ions in the plasma.Confocal Raman spectra confirmed the DLC characteristics of the films.Fourier-transform infrared characterization indicates that the DLC films were composed of sp^3 and sp^2 carbonbonded hydrogen.The hardness of the films was evaluated with a Nano Indenter-XP System.The result shows that the highest hardness valus was 14.6 GPa.The surface rms roughness of the films was as low as 0.104nm measured with an atomic force microscope.The friction coeffcient of the films was checked using a ball-on-disk microtribometer.The average friction coefficient is approximately 0.122.展开更多
From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental st...From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.展开更多
Haloacetic acids(HAAs) are formed during the chlorination of drinking water,which are harmful to people′s health due to their carcinogenic and mutagenic effects. In the present study,a detection method combining meth...Haloacetic acids(HAAs) are formed during the chlorination of drinking water,which are harmful to people′s health due to their carcinogenic and mutagenic effects. In the present study,a detection method combining methyl tert -butyl ether(MtBE) extraction with acid catalysis and gas chromatography coupled with an electron capture detector(GC/ECD) was developed for determining HAAs. The detection limit of this method(MDL) and relative standard deviation(RSD) were below 0.37 μg/L and 6.2%,respectively. The laboratory chlorination experiments were conducted with the purpose of investigating the influences of reaction time,temperature,UV_ 254 ,bromide and ammonia-nitrogen on the formation of HAAs. The results show that the formation amount of HAAs increases with increasing reaction time and temperature,respectively;and there exists a linear relationship between the formation of HAAs and UV_ 254 . The formation amount of HAAs decreases first and then increases as the bromide ion concentration increases,and adding NH +_4 is a possible way to control the formation of HAAs.展开更多
A high power continuous wave (CW) laser diode (LD) pumped acousto-optic Q-switched Nd:YVO4 laser is presented. A short pulse at the 1064 nm is obtained. With a repetition rate of 50 kHz,the maximum average output powe...A high power continuous wave (CW) laser diode (LD) pumped acousto-optic Q-switched Nd:YVO4 laser is presented. A short pulse at the 1064 nm is obtained. With a repetition rate of 50 kHz,the maximum average output power of 5.72 W is achieved. The optical conversion efficiency and the slope efficiency are up to 28% and 32.4% respectively. At the repetition rate of 10 kHz and the pulse width of 16.3ns, the maximum single pulse energy of 286 μJ and the peak power of 13kW are acquired. The laser can be used as a signal source in the free-space optical communication. The output signal agrees with the modulate signal well.展开更多
文摘通过中美交流互访、水资源研究现状调查和2007-2017年Web of Science中有关水资源领域的文献统计分析,对比了中美水资源研究在研究机构、经费来源、研究领域、代表性人物等方面在现阶段所存在的差异,归纳总结了中美水资源研究的最新进展:总体上,中国从事水资源研究的人员和机构众多,研究领域更宽泛,中国水资源侧重江河水利规划、水资源的综合高效利用、快速变化条件下人类活动对水资源水环境的影响的研究;相对而言,美国从事水资源研究的人员和机构相对偏少,研究领域相对较新,研究尺度较大,学科交叉性强,相对更成熟,研究程度更高,往往从全球的角度来研究水,更加注重水法水权、水资源的评价、特殊水资源的规划与利用、水资源的保护、水资源的生态补偿、水资源的处理费用、与水有关的工程与环境相协调等综合研究领域.最后,本研究展望了中美双方在水资源研究领域的发展趋势及带给我们的启示.
文摘The dimension number of the centralized Kalman filter (CKF) for the rapid transfer alignment (TA) is as high as 21 if the aircraft wing flexure motion is considered in the rapid TA. The 21-dimensional CKF brings the calculation burden on the computer and the difficulty to meet a high filtering updating rate desired by rapid TA. The federated Kalman filter (FKF) for the rapid TA is proposed to solve the dilemma. The structure and the algorithm of the FKF, which can perform parallel computation and has less calculation burden, are designed.The wing flexure motion is modeled, and then the 12-order velocity matching local filter and the 15-order attitud ematching local filter are devised. Simulation results show that the proposed EKE for the rapid TA almost has the same performance as the CKF. Thus the calculation burden of the proposed FKF for the rapid TA is markedly decreased.
基金TheNationalNaturalScienceFoundationofChina (No .5 96 780 18)
文摘Water quality within water distribution system may vary with both location and time. Water quality models are used to predict the spatial and temporal variation of water quality throughout water system. A model of residual chlorine decay in water pipe has been developed, given the consumption of chlorine in reactions with chemicals in bulk water, bio films on pipe wall, in corrosion process, and the mass transport of chlorine from bulk water to pipe wall. Analytical methods of the flow path from water sources to the observed point and the water age of every observed node were proposed. Model is used to predict the decay of residual chlorine in an actual distribution system. Good agreement between calculated and measured values was obtained.
文摘Diamond-like carbon(DLC)films were prepared on Si(100) substrates by ion implantation from an electron cyclotron resonance microwave plasma source.During the implantation,650W microwave power was used to produce discharge plasma with methane as working gas,and-20KV voltage pulses were applied to the substrate holder to accelerate ions in the plasma.Confocal Raman spectra confirmed the DLC characteristics of the films.Fourier-transform infrared characterization indicates that the DLC films were composed of sp^3 and sp^2 carbonbonded hydrogen.The hardness of the films was evaluated with a Nano Indenter-XP System.The result shows that the highest hardness valus was 14.6 GPa.The surface rms roughness of the films was as low as 0.104nm measured with an atomic force microscope.The friction coeffcient of the films was checked using a ball-on-disk microtribometer.The average friction coefficient is approximately 0.122.
基金This project is supported by National Natural Science Foundation of China (No.50175011).
文摘From the general formula for calculating the efficiency of planetary geartrains, the efficiency of the double crank ring-plate-type pin-cycloidal gear planetary drive isderived. To prove the theory, an experimental study has been conducted. The tested value of theefficiency of a sample set of the new-type drive in the experiment agrees with the calculated one.It shows that the new-type drive is of not merely high bearing capacity, but also quite highefficiency.
文摘Haloacetic acids(HAAs) are formed during the chlorination of drinking water,which are harmful to people′s health due to their carcinogenic and mutagenic effects. In the present study,a detection method combining methyl tert -butyl ether(MtBE) extraction with acid catalysis and gas chromatography coupled with an electron capture detector(GC/ECD) was developed for determining HAAs. The detection limit of this method(MDL) and relative standard deviation(RSD) were below 0.37 μg/L and 6.2%,respectively. The laboratory chlorination experiments were conducted with the purpose of investigating the influences of reaction time,temperature,UV_ 254 ,bromide and ammonia-nitrogen on the formation of HAAs. The results show that the formation amount of HAAs increases with increasing reaction time and temperature,respectively;and there exists a linear relationship between the formation of HAAs and UV_ 254 . The formation amount of HAAs decreases first and then increases as the bromide ion concentration increases,and adding NH +_4 is a possible way to control the formation of HAAs.
文摘A high power continuous wave (CW) laser diode (LD) pumped acousto-optic Q-switched Nd:YVO4 laser is presented. A short pulse at the 1064 nm is obtained. With a repetition rate of 50 kHz,the maximum average output power of 5.72 W is achieved. The optical conversion efficiency and the slope efficiency are up to 28% and 32.4% respectively. At the repetition rate of 10 kHz and the pulse width of 16.3ns, the maximum single pulse energy of 286 μJ and the peak power of 13kW are acquired. The laser can be used as a signal source in the free-space optical communication. The output signal agrees with the modulate signal well.
