The theoretical statistical model of sea clutter is a key issue for maritime surveillance. In recent years, the statistical model of sea clutter has attracted much attention to design the detector well. Meanwhile, the...The theoretical statistical model of sea clutter is a key issue for maritime surveillance. In recent years, the statistical model of sea clutter has attracted much attention to design the detector well. Meanwhile, the circular scanning synthetic aperture radar(SAR) has been applied to wide surveillance of the sea surface.Therefore, the paper analyzes the validity of available sea clutter models for range Doppler images from different scan angles for moderate sea state in the medium grazing angle. The parameter estimation method for different distribution models employs the method of logarithmic cumulant(MoLC) based on Mellin transform uniformly. By the analysis of the fitting performance between the histogram of real data and the amplitude probability density function(PDF) of empirical distribution models and the goodness-of-fit(GoF) test for real data from different scan angles, it is indicated the generalized K(GK) distribution with generalized Gamma texture distribution can fit the sea clutter well for different scan angles in the medium grazing angle.展开更多
The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wi...The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wind field,a potential extension of dual-frequency(C-band and Ku-band)polarimetric measurements is investigated for both low and very high wind speeds,from 5 to 45 m s^-1.Based on the geophysical model functions of C-band and Ku-band,the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath,especially in nadir area,with the wind direction root-mean-square error(RMSE)less than 12?in the wind speed range of 5–25 m s^-1.Furthermore,the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval,with the wind speed retrieval accuracy better than 2 m s^-1 for all wind conditions(0–45 m s^-1).For extreme winds,the C-band HH backscatter coefficients modeled by CMOD5.N(H)and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector.This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields,and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s^-1).Thus,to improve the wind retrieval for all wind conditions,the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam,and C-band horizontal and Ku-band vertical polarization in outer beam,can be used to measure ocean winds.This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer.展开更多
目的分析儿童重症监护病房(PICU)内按基线氧合指数(OI)诊断中度和重度儿童急性呼吸窘迫综合征(PARDS)婴幼儿的临床特点和预后差异。方法对"肺表面活性物质治疗婴幼儿中重度ARDS疗效分析"研究所建立的临床数据库资料进行二次...目的分析儿童重症监护病房(PICU)内按基线氧合指数(OI)诊断中度和重度儿童急性呼吸窘迫综合征(PARDS)婴幼儿的临床特点和预后差异。方法对"肺表面活性物质治疗婴幼儿中重度ARDS疗效分析"研究所建立的临床数据库资料进行二次分析。回顾性比较2016年12月至2021年12月收住中国14家三级甲等医院PICU的101例按基线OI诊断的中度和重度PARDS婴幼儿在一般情况、基础疾病、OI、机械通气、肺表面活性物质应用、预后等临床资料方面的差异。结果101例患儿中,中度和重度PARDS患儿分别为55例(54.5%)和46例(45.5%)。重度组男性比例(50.0%比72.7%,P=0.019)及小儿危重病例评分[72(68,78)分比76(70,80)分,P=0.019]均显著低于中度组,而年龄、体重、致PARDS病因、基础疾病等两组比较差异无统计学意义(P>0.05)。重度组患儿高频呼吸机使用率显著高于中度组(34.8%比10.9%,P=0.004),但肺表面活性物质使用情况、液体负荷及肺部并发症比较差异无统计学意义(P>0.05)。重度组患儿24 h OI改善程度[0.26±0.33比0.04±0.34,P=0.001]和72 h OI改善程度[0.34(-0.04,0.62)比0.15(-0.14,0.42),P=0.029]均显著优于中度组,但两组患儿间的病死率、确诊PARDS后住院时间和呼吸机治疗时间等比较差异无统计学意义(P>0.05)。结论在有创机械通气的中度和重度PARDS婴幼儿中,按基线OI诊断的重度PARDS患儿治疗早期氧合改善优于中度患儿,也更可能接受高频通气治疗。基线OI并不能敏感区分此类患儿预后,并非此类患儿PARDS分度的理想指标。展开更多
基金supported by the National Natural Science Foundation of China(61621005 61671352)+2 种基金the Key Laboratory of Cognitive Radio and Information Processing,Ministry of Education(Guilin University of Electronic Technology)(CRKL160206)the Innovational Foundation of Shanghai Academy of Space Technology(SAST2016027SAST2016033)
文摘The theoretical statistical model of sea clutter is a key issue for maritime surveillance. In recent years, the statistical model of sea clutter has attracted much attention to design the detector well. Meanwhile, the circular scanning synthetic aperture radar(SAR) has been applied to wide surveillance of the sea surface.Therefore, the paper analyzes the validity of available sea clutter models for range Doppler images from different scan angles for moderate sea state in the medium grazing angle. The parameter estimation method for different distribution models employs the method of logarithmic cumulant(MoLC) based on Mellin transform uniformly. By the analysis of the fitting performance between the histogram of real data and the amplitude probability density function(PDF) of empirical distribution models and the goodness-of-fit(GoF) test for real data from different scan angles, it is indicated the generalized K(GK) distribution with generalized Gamma texture distribution can fit the sea clutter well for different scan angles in the medium grazing angle.
基金supported by the National Key R&D Program of China (No. 2016YFC1401006)the National Natural Science Foundation of China (Nos. 51279186, 51479183 and 41676169)+2 种基金the National Program on Key Basic Research Project (No. 2011CB013704)the 111 Project (No. B14028)the Marine and Fishery Information Center Project of Jiangsu Province (No. SJC2014 110338)
文摘The wind retrieval performance of HY-2 A scanning scatterometer operating at Ku-band in HH and VV polarizations has been well evaluated in the wind speed range of 0–25 m s^-1.In order to obtain more accurate ocean wind field,a potential extension of dual-frequency(C-band and Ku-band)polarimetric measurements is investigated for both low and very high wind speeds,from 5 to 45 m s^-1.Based on the geophysical model functions of C-band and Ku-band,the simulation results show that the polarimetric measurements of Ku-band can improve the wind vector retrieval over the entire scatterometer swath,especially in nadir area,with the wind direction root-mean-square error(RMSE)less than 12?in the wind speed range of 5–25 m s^-1.Furthermore,the results also show that C-band cross-polarization plays a very important role in improving the wind speed retrieval,with the wind speed retrieval accuracy better than 2 m s^-1 for all wind conditions(0–45 m s^-1).For extreme winds,the C-band HH backscatter coefficients modeled by CMOD5.N(H)and the ocean co-polarization ratio model at large incidence are used to retrieve sea surface wind vector.This result reveals that there is a big decrease of wind direction retrieval RMSE for extreme wind fields,and the retrieved result of C-band HH polarization is nearly the same as that of C-band VV polarization for low-to-high wind speed(5–25 m s^-1).Thus,to improve the wind retrieval for all wind conditions,the dual-frequency polarimetric scatterometer with C-band and Ku-band horizontal polarization in inner beam,and C-band horizontal and Ku-band vertical polarization in outer beam,can be used to measure ocean winds.This study will contribute to the wind retrieval with merged satellites data and the future spaceborne scatterometer.
文摘目的分析儿童重症监护病房(PICU)内按基线氧合指数(OI)诊断中度和重度儿童急性呼吸窘迫综合征(PARDS)婴幼儿的临床特点和预后差异。方法对"肺表面活性物质治疗婴幼儿中重度ARDS疗效分析"研究所建立的临床数据库资料进行二次分析。回顾性比较2016年12月至2021年12月收住中国14家三级甲等医院PICU的101例按基线OI诊断的中度和重度PARDS婴幼儿在一般情况、基础疾病、OI、机械通气、肺表面活性物质应用、预后等临床资料方面的差异。结果101例患儿中,中度和重度PARDS患儿分别为55例(54.5%)和46例(45.5%)。重度组男性比例(50.0%比72.7%,P=0.019)及小儿危重病例评分[72(68,78)分比76(70,80)分,P=0.019]均显著低于中度组,而年龄、体重、致PARDS病因、基础疾病等两组比较差异无统计学意义(P>0.05)。重度组患儿高频呼吸机使用率显著高于中度组(34.8%比10.9%,P=0.004),但肺表面活性物质使用情况、液体负荷及肺部并发症比较差异无统计学意义(P>0.05)。重度组患儿24 h OI改善程度[0.26±0.33比0.04±0.34,P=0.001]和72 h OI改善程度[0.34(-0.04,0.62)比0.15(-0.14,0.42),P=0.029]均显著优于中度组,但两组患儿间的病死率、确诊PARDS后住院时间和呼吸机治疗时间等比较差异无统计学意义(P>0.05)。结论在有创机械通气的中度和重度PARDS婴幼儿中,按基线OI诊断的重度PARDS患儿治疗早期氧合改善优于中度患儿,也更可能接受高频通气治疗。基线OI并不能敏感区分此类患儿预后,并非此类患儿PARDS分度的理想指标。
