A quantitative risk assessment （QRA） based on leak detection criteria （LDC） for the design of a proposed subsea oil export pipeline is presented in this paper. The objective of this QRA/LDC study was to determine ...A quantitative risk assessment （QRA） based on leak detection criteria （LDC） for the design of a proposed subsea oil export pipeline is presented in this paper. The objective of this QRA/LDC study was to determine if current leak detection methodologies were sufficient, based on QRA results, while excluding the use of statistical leak detection; if not, an appropriate LDC for the leak detection system would need to be established. The famous UK PARLOC database was used for the calculation of pipeline failure rates, and the software POSVCM from MMS was used for oil spill simulations. QRA results revealed that the installation of a statistically based leak detection system （LDS） can significantly reduce time to leak detection, thereby mitigating the consequences of leakage. A sound LDC has been defined based on QRA study results and comments from various LDS vendors to assist the emergency response team （ERT） to quickly identify and locate leakage and employ the most effective measures to contain damage.展开更多
The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing ...The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study.展开更多
Fabry-Perot Interferometer(FPI) has been used widely for wind measurements of the middle and upper atmosphere.To date, most of FPIs have been based on full-closed circular fringe, which needs 15–25 min to obtain a gr...Fabry-Perot Interferometer(FPI) has been used widely for wind measurements of the middle and upper atmosphere.To date, most of FPIs have been based on full-closed circular fringe, which needs 15–25 min to obtain a group of wind velocity(zonal and meridional). However, it is hard to improve the temporal resolution because full-closed circular fringe in several directions cannot be easily imaged onto the same Charge-Coupled Device(CCD) with enough airglow intensity. In this paper, a data processing method is proposed for non-full circular fringe of FPI, which can support CCD with enough area of observations in several directions simultaneously. The method is focused on the center determination of non-full fringe. It includes radial cross-section, peak coordinate determination, and center calculation. Based on the calculated center, the fringe is annular summed. Then its radius is determined subsequently using Gaussian fitting. Finally, the wind is retrieved from the fringe radius. For validation, fringes from two ground-based FPIs were used, which are deployed in Kelan(38.71°N, 111.58°E) and Xinglong(40.40°N, 117.59°E) in China. The results retrieved from non-full fringes of FPIs were compared with that from full-closed circular fringe. The averaged wind deviation between them demonstrates reasonable difference with 5.38 ms^-(1) for 892.0 nm airglow emission, 5.81 ms^-(1) for 630.0 nm emission, and 3.03 ms^-(1) for 557.7 nm emission. Besides, wind results of Xinglong FPI are compared roughly with measurements of meteor radar which is deployed in Ming Tombs of Beijing(40.3°N,116.2°E). Good agreement demonstrates that this method is robust enough for FPI wind retrieval of mesosphere and thermosphere.展开更多
文摘A quantitative risk assessment （QRA） based on leak detection criteria （LDC） for the design of a proposed subsea oil export pipeline is presented in this paper. The objective of this QRA/LDC study was to determine if current leak detection methodologies were sufficient, based on QRA results, while excluding the use of statistical leak detection; if not, an appropriate LDC for the leak detection system would need to be established. The famous UK PARLOC database was used for the calculation of pipeline failure rates, and the software POSVCM from MMS was used for oil spill simulations. QRA results revealed that the installation of a statistically based leak detection system （LDS） can significantly reduce time to leak detection, thereby mitigating the consequences of leakage. A sound LDC has been defined based on QRA study results and comments from various LDS vendors to assist the emergency response team （ERT） to quickly identify and locate leakage and employ the most effective measures to contain damage.
基金supported by the National High Technology Research and Development Program of China (2013 AA09A505)
文摘The altimeter normalized radar cross section(NRCS) has been used to retrieve the sea surface wind speed for decades, and more than a dozen of wind speed retrieval algorithms have been proposed. Despite the continuing efforts to improve the wind speed measurements, a bias dependence on wave state persists in all wind algorithms. On the basis of recent evidence that short waves are essentially modulated by local winds and much less affected by wave state, we proposed a physics-based approach to retrieve the wind speed from the dual-frequency difference in terms of the mean square slope of short waves. A collocated dataset of coincident altimeter/buoy measurements were used to develop and validate the approach. Validation against buoy measurements indicates that the approach is almost unbiased and has an overall root mean square error of 1.24 m s-1, which is 5.3% lower than the single-parameter algorithm in operational use(Witter and Chelton, 1991) and 2.4% lower than another dual-frequency approach(Chen et al., 2002). Furthermore, the results indicate that the new approach significantly improves the wave-dependent bias compared to the single-parameter algorithm. The capacity of altimeter to retrieve sea surface wind speed appears to be limited for the case of winds below 3 m s-1. The validity of the approach at high winds needs to be further examined in the future study.
基金supported by National Space Science Center (Xinglong FPI data)Institute of Geology and Geophysics (meteor radar data)Beijing Municipal Science and Technology Commission (Grant No. Z151100003615001)
文摘Fabry-Perot Interferometer(FPI) has been used widely for wind measurements of the middle and upper atmosphere.To date, most of FPIs have been based on full-closed circular fringe, which needs 15–25 min to obtain a group of wind velocity(zonal and meridional). However, it is hard to improve the temporal resolution because full-closed circular fringe in several directions cannot be easily imaged onto the same Charge-Coupled Device(CCD) with enough airglow intensity. In this paper, a data processing method is proposed for non-full circular fringe of FPI, which can support CCD with enough area of observations in several directions simultaneously. The method is focused on the center determination of non-full fringe. It includes radial cross-section, peak coordinate determination, and center calculation. Based on the calculated center, the fringe is annular summed. Then its radius is determined subsequently using Gaussian fitting. Finally, the wind is retrieved from the fringe radius. For validation, fringes from two ground-based FPIs were used, which are deployed in Kelan(38.71°N, 111.58°E) and Xinglong(40.40°N, 117.59°E) in China. The results retrieved from non-full fringes of FPIs were compared with that from full-closed circular fringe. The averaged wind deviation between them demonstrates reasonable difference with 5.38 ms^-(1) for 892.0 nm airglow emission, 5.81 ms^-(1) for 630.0 nm emission, and 3.03 ms^-(1) for 557.7 nm emission. Besides, wind results of Xinglong FPI are compared roughly with measurements of meteor radar which is deployed in Ming Tombs of Beijing(40.3°N,116.2°E). Good agreement demonstrates that this method is robust enough for FPI wind retrieval of mesosphere and thermosphere.
