A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a ...A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.展开更多
Automatic Vehicle Identification (AVI) in real time is becoming an urgent necessity due to rapid increase in the number of vehicles on roads. The Radio Frequency Identification (RFID) Technology can be used for vehicl...Automatic Vehicle Identification (AVI) in real time is becoming an urgent necessity due to rapid increase in the number of vehicles on roads. The Radio Frequency Identification (RFID) Technology can be used for vehicle identification to gather information in real-time from roads by getting the vehicles location from RFID readers placed in the vehicle. This paper focuses on designing the Public Vehicle Location System (PVLS). The proposed structure consists of passive RFID tags placed at various locations on the chosen route, RFID reader on the Bus, wireless communication with a PC and commanding software (RFID reader and database structure), also PVLS applications and website. The designed system controls, manages and monitors the performance of RFID readers. It also filters and stores the information in an appropriate format so that it could be used without difficulty in the application system and website. The system implemented by using RFID is placed in the Bus which is programmed by Visual C# 2008 with Compact .Net Framework.展开更多
The development of experimental facilities for rail vehicle testing at the NRCCentre for Surface Transportation Technology is being complemented byanalytic studies. The purpose of this effort has been to gain insight ...The development of experimental facilities for rail vehicle testing at the NRCCentre for Surface Transportation Technology is being complemented byanalytic studies. The purpose of this effort has been to gain insight into thedynamics of rail vehicles in order to guide the development of the Curved TrackSimulator (CTS) and to establish an analytic framework for the design andinterpretation of tests to be conducted on the CTS. The work described hererepresents an initial effort towarde meeting these objectives.Parametric study results using linear model of freight truck on the CTSshowed that (a) increasing roller radius increases critical speed (b) increasingthe wheel initial cone angle will decrease the hunting speed (c) increasing theroller cant increases hunting speed (d) decrowning of the wheelset on the rollerewill not effect the hunting speed but induces longitudinal destabilzing horizontalforces at the contact and (e) lozenging of wheelset on the rollers induces a yawmoment and the hunting speed decreases with increasing wheelset yaw angle.展开更多
In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pear...In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pearl River Estuary （Delft3D） has been applied to the study of the physical hydrography of Hong Kong waters and its relationship with algal bloom transport patterns in the dry and wet seasons. The general 3D hydrodynamic circulation and salinity structure in the partially-mixed estuary are presented. Extensive numerical surface drogue tracking experiments are performed for algal blooms that are initiated in the Mirs Bay under different seasonal, wind and tidal conditions. The probability of bloom impact on the Victoria Harbour and nearby urban coastal waters is estimated. The computations show that： i） In the wet season （May - August）, algal blooms initiated in the Mirs Bay will move in a clockwise direction out of the bay, and be transported away from Hong Kong due to SW monsoon winds which drive the SW to NE coastal current; ii） In the dry season （November- April）, algal blooms initiated in the northeast Mirs Bay will move in an anti-clockwise direction and be carried away into southern waters due to the NE to SW coastal current driven by the NE monsoon winds; the bloom typically flows past the east edge of the Victoria Harbeur and nearby waters. Finally, the role of hydrodynamic transport in an important episodic event -- the spring 1998 massive red tide -- is quantitatively examined. It is shown that the strong NE to E wind during late March to early April, coupled with the diurnal tide at the beginning of April, significantly increased the probability of bloom transport into the Port Shelter and East Lamma Channel, resulting in the massive fish kill. The results provide a basis for risk assessment of harmful algal bloom （HAB） impact on urban coastal waters around the Victoria Habour.展开更多
文摘A precipitation enhancement operation using an aircraft was conducted from 1415 to 1549 LST 14 March 2000 in Shaanxi Province. The NOAA-14 satellite data received at 1535 LST soon after the cloud seeding shows that a vivid cloud track appears on the satellite image. The length, average width and maximum width of the cloud track are 301 km, 8.3 and 11 km, respectively. Using a three-dimensional numerical model of transport and diffusion of seeding material within stratiform clouds, the spatial concentration distribution characteristics of seeding material at different times, especially at the satellite receiving time, are simulated. The model results at the satellite receiving time are compared with the features of the cloud track. The transported position of the cloud seeding material coincides with the position of the track. The width, shape and extent of diffusion of the cloud seeding material are similar to that of the cloud track. The spatial variation of width is consistent with that of the track. The simulated length of each segment of the seeding line accords with the length of every segment of the track. Each segment of the cloud track corresponds to the transport and diffusion of each segment of the seeding line. These results suggest that the cloud track is the direct physical reflection of cloud seeding at the cloud top. The comparison demonstrates that the numerical model of transport and diffusion can simulate the main characteristics of transport and diffusion of seeding material, and the simulated results are sound and trustworthy. The area, volume, vidth, depth, and lateral diffusive rate corresponding to concentrations 1, 4, and 10 L-1are simulated in order to understand the variations of influencing range.
文摘Automatic Vehicle Identification (AVI) in real time is becoming an urgent necessity due to rapid increase in the number of vehicles on roads. The Radio Frequency Identification (RFID) Technology can be used for vehicle identification to gather information in real-time from roads by getting the vehicles location from RFID readers placed in the vehicle. This paper focuses on designing the Public Vehicle Location System (PVLS). The proposed structure consists of passive RFID tags placed at various locations on the chosen route, RFID reader on the Bus, wireless communication with a PC and commanding software (RFID reader and database structure), also PVLS applications and website. The designed system controls, manages and monitors the performance of RFID readers. It also filters and stores the information in an appropriate format so that it could be used without difficulty in the application system and website. The system implemented by using RFID is placed in the Bus which is programmed by Visual C# 2008 with Compact .Net Framework.
文摘The development of experimental facilities for rail vehicle testing at the NRCCentre for Surface Transportation Technology is being complemented byanalytic studies. The purpose of this effort has been to gain insight into thedynamics of rail vehicles in order to guide the development of the Curved TrackSimulator (CTS) and to establish an analytic framework for the design andinterpretation of tests to be conducted on the CTS. The work described hererepresents an initial effort towarde meeting these objectives.Parametric study results using linear model of freight truck on the CTSshowed that (a) increasing roller radius increases critical speed (b) increasingthe wheel initial cone angle will decrease the hunting speed (c) increasing theroller cant increases hunting speed (d) decrowning of the wheelset on the rollerewill not effect the hunting speed but induces longitudinal destabilzing horizontalforces at the contact and (e) lozenging of wheelset on the rollers induces a yawmoment and the hunting speed decreases with increasing wheelset yaw angle.
基金This study was supported by a Hong Kong Research Grants Council Group Research Project (RGC//HKU1/02C) ,and partially by a grantfromthe University Grants Committee of the Hong Kong Special Administrative Region,China(Project No. AoE/P-04/04 and P-04/02) tothe Area of Excellencein Marine Environment Research andInnovativeTechnology (MERIT)
文摘In sub-tropical coastal waters around Hong Kong, algal blooms and red tides are usually first sighted in the Mirs Bay, in the eastern waters of Hong Kong. A calibrated three-dimensional hydrodynamic model for the Pearl River Estuary （Delft3D） has been applied to the study of the physical hydrography of Hong Kong waters and its relationship with algal bloom transport patterns in the dry and wet seasons. The general 3D hydrodynamic circulation and salinity structure in the partially-mixed estuary are presented. Extensive numerical surface drogue tracking experiments are performed for algal blooms that are initiated in the Mirs Bay under different seasonal, wind and tidal conditions. The probability of bloom impact on the Victoria Harbour and nearby urban coastal waters is estimated. The computations show that： i） In the wet season （May - August）, algal blooms initiated in the Mirs Bay will move in a clockwise direction out of the bay, and be transported away from Hong Kong due to SW monsoon winds which drive the SW to NE coastal current; ii） In the dry season （November- April）, algal blooms initiated in the northeast Mirs Bay will move in an anti-clockwise direction and be carried away into southern waters due to the NE to SW coastal current driven by the NE monsoon winds; the bloom typically flows past the east edge of the Victoria Harbeur and nearby waters. Finally, the role of hydrodynamic transport in an important episodic event -- the spring 1998 massive red tide -- is quantitatively examined. It is shown that the strong NE to E wind during late March to early April, coupled with the diurnal tide at the beginning of April, significantly increased the probability of bloom transport into the Port Shelter and East Lamma Channel, resulting in the massive fish kill. The results provide a basis for risk assessment of harmful algal bloom （HAB） impact on urban coastal waters around the Victoria Habour.
