The evolutionary process and structural characteristics of the atmospheric circulation and synoptic situation which caused the record heavy rainfall with a precipitation amount of 550 mm in Hat Yai, Thailand from 20 t...The evolutionary process and structural characteristics of the atmospheric circulation and synoptic situation which caused the record heavy rainfall with a precipitation amount of 550 mm in Hat Yai, Thailand from 20 to 23 November 2000 is studied. In the study, the modern three dimensional observational data were collected as completely as possible, and detailed analyses were made. It is revealed that the cold surges of the Asian winter monsoon that originate from Siberia can arrive at the lower latitudes, including South Thailand, Malaysia, Indonesia, cause strong heavy rainfall there, and interact with weather systems in the near-equatorial regions of the Southern Hemisphere. This is strongly supported by Chinese scientist's original finding in 1930s. The strong convective cloud clusters in the above areas are generated by the direct influence of the cold surges, and are related with the South China Sea disturbances in the lower troposphere. The maximum of the convergence of total moisture flux near South Thailand in the situation under study implies that the water vapour supply is abundant and very favorable to the occurrence of the heavy rainfall. The release of latent heat enhances the Hadley Circulation also. The feedback of the strong severe weather on climate indeed exists, and there are pronounced interactions between the multi-scale systems and between both hemispheres.展开更多
This paper describes the measurement of contact pressure in the context of wheel–terrain interaction as affected by wheel load and tire inflation pressure when fusion of the wavelet transform with the back-propagatio...This paper describes the measurement of contact pressure in the context of wheel–terrain interaction as affected by wheel load and tire inflation pressure when fusion of the wavelet transform with the back-propagation(BP)neural network is applied to construct the wavelet neural network contact pressure prediction model.To this aim,a controlled soil bin testing facility equipped with single-wheel tester was utilized while three levels of velocity,three levels of slippage and three levels of wheel load were applied.Using image processing technique,contact area values were determined which were subsequently used for quantification of contact pressure.Performances of the different predictor models incorporated of various mother wavelets were evaluated using standard statistical evaluation criteria.Root mean square error and coefficient of determination values of 0.1382 and 0.9864 achieved by the optimal wavelet neural network are better than that of BP neural network.The proposed tool typifies a high learning speed,enhanced predicting accuracy,and strong robustness.展开更多
Background: Human African trypanosomiasis (HAT) occurs in three historical foci in the Central African Republic. Objective: To describe the morbi-mortality of childhood HAT in rural Central African Republic with the a...Background: Human African trypanosomiasis (HAT) occurs in three historical foci in the Central African Republic. Objective: To describe the morbi-mortality of childhood HAT in rural Central African Republic with the aim of early management. Methods: Descriptive and analytic cross-sectional study conducted from January 1, 2017 to March 30, 2018 at Nola prefectural hospital. This study was included all children seen as outpatients and/or hospitalized in the pediatric wards, in whom the diagnosis of HAT was confirmed. Statistical analysis was performed using Epi-info software. Results: Forty children were included from Bilolo (60%), Nola (30%) and Salo (10%). The sex ratio was 0.66 with a median age of 8.65 ± 12.48 years. Fever (82.5%), nocturnal insomnia (75%), daytime somnolence (67.5%), headache (65%), polyarthralgia (62.5%), convulsions 52.5% (n = 21), tremor (27.5%), trypanidism (7.5%) and delirium (2.5%) were the main functional signs. Examination signs were adenopathy (52.5%), paresthesia (30%), decreased cutaneous-abdominal reflexes (25%) and osteoarticular reflexes (17.5%), hyperesthesia (20%), extrapyramidal hypertonia (15%) and depression (2.5%). The children were in the lymphatic-blood phase in 65% of cases, and meningoencephalitis in 35%. Pentamidine was administered in 65% of cases. Four children died and 6 had neurological sequelae. There was an association between age under 5, Bilolo’s focus, the children’s history and the severity of the disease. Age under 5, gender, household, children’s activity, history and occurrence of sequelae were also associated. Conclusion: HAT remains a permanent threat to Central African children. Any clinical presentation combining long-term infectious signs and unexplained neurological or neuropsychological disorders must be treated with caution.展开更多
重力恢复与气候实验(gravity recovery and climate experiment,GRACE)卫星已成为观测冰盖质量变化的主要手段之一,但不同机构发布的GRACE数据在估计格陵兰冰盖质量变化上存在较大差异,在研究长期变化趋势时会产生很大不一致性。针对此...重力恢复与气候实验(gravity recovery and climate experiment,GRACE)卫星已成为观测冰盖质量变化的主要手段之一,但不同机构发布的GRACE数据在估计格陵兰冰盖质量变化上存在较大差异,在研究长期变化趋势时会产生很大不一致性。针对此问题,先分析了用不同GRACE数据估算的格陵兰冰盖质量变化数据之间的差异,再用三角帽(three-cornered hat,TCH)方法对其进行不确定性分析,并通过数据融合消除了不同数据间的不一致性。展开更多
Microwave Radiometer Imager(MWRI) is a key payload of China’s second generation polar meteorological satellite, i.e., Fengyun-3 series(FY-3). Up to now, 5 satellites including FY-3A(2008), FY-3B(2010), FY-3C(2013), F...Microwave Radiometer Imager(MWRI) is a key payload of China’s second generation polar meteorological satellite, i.e., Fengyun-3 series(FY-3). Up to now, 5 satellites including FY-3A(2008), FY-3B(2010), FY-3C(2013), FY-3D(2018), and FY-3E(2021) have been launched successfully to provide multiwavelength, all-weather, and global data for decades. Much progress has been made on the calibration of MWRI and a recalibrated MWRI brightness temperature(BT) product(V2) was recently released. This study thoroughly evaluates the accuracy of this new product from FY-3B, 3C, and 3D by using the simultaneous collocated Global Precipitation Measurement(GPM)Microwave Imager(GMI) measurements as a reference. The results show that the mean biases(MBEs) of the BT between MWRI and GMI are generally less than 0.5 K and the root mean squares(RMSs) between them are less than1.5 K. The previous notable ascending and descending difference of the MWRI has disappeared. This indicates that the new MWRI recalibration procedure is very effective in removing potential errors associated with the emission of the hot-load reflector. Analysis of the dependence of MBE on the latitude and earth scene temperature shows that MBE decreases with decreasing latitude over ocean. Furthermore, MBE over ocean decreases linearly with increasing scene temperature for almost all channels, whereas this does not occur over land. A linear regression fitting is then used to modify MWRI, which can reduce the MBE over ocean to be within 0.2 K. The standard deviation of error of GMI, FY-3B, and FY-3D MWRI BT data derived by using the three-cornered hat method(TCH) shows that GMI has the best overall performance over ocean except at 10.65 GHz where its standard deviation of error is slightly larger than that of FY-3D. Over land, the standard deviation of error of FY-3D is the lowest at almost all channels except at 89V. MWRI onboard FY-3 series satellites would serve as an important passive microwave radiometer member of the constellation to monitor key surface and at展开更多
基金The other authors are grateful for the support from the China National Science Foundation(Grant No.40233027)
文摘The evolutionary process and structural characteristics of the atmospheric circulation and synoptic situation which caused the record heavy rainfall with a precipitation amount of 550 mm in Hat Yai, Thailand from 20 to 23 November 2000 is studied. In the study, the modern three dimensional observational data were collected as completely as possible, and detailed analyses were made. It is revealed that the cold surges of the Asian winter monsoon that originate from Siberia can arrive at the lower latitudes, including South Thailand, Malaysia, Indonesia, cause strong heavy rainfall there, and interact with weather systems in the near-equatorial regions of the Southern Hemisphere. This is strongly supported by Chinese scientist's original finding in 1930s. The strong convective cloud clusters in the above areas are generated by the direct influence of the cold surges, and are related with the South China Sea disturbances in the lower troposphere. The maximum of the convergence of total moisture flux near South Thailand in the situation under study implies that the water vapour supply is abundant and very favorable to the occurrence of the heavy rainfall. The release of latent heat enhances the Hadley Circulation also. The feedback of the strong severe weather on climate indeed exists, and there are pronounced interactions between the multi-scale systems and between both hemispheres.
文摘This paper describes the measurement of contact pressure in the context of wheel–terrain interaction as affected by wheel load and tire inflation pressure when fusion of the wavelet transform with the back-propagation(BP)neural network is applied to construct the wavelet neural network contact pressure prediction model.To this aim,a controlled soil bin testing facility equipped with single-wheel tester was utilized while three levels of velocity,three levels of slippage and three levels of wheel load were applied.Using image processing technique,contact area values were determined which were subsequently used for quantification of contact pressure.Performances of the different predictor models incorporated of various mother wavelets were evaluated using standard statistical evaluation criteria.Root mean square error and coefficient of determination values of 0.1382 and 0.9864 achieved by the optimal wavelet neural network are better than that of BP neural network.The proposed tool typifies a high learning speed,enhanced predicting accuracy,and strong robustness.
文摘Background: Human African trypanosomiasis (HAT) occurs in three historical foci in the Central African Republic. Objective: To describe the morbi-mortality of childhood HAT in rural Central African Republic with the aim of early management. Methods: Descriptive and analytic cross-sectional study conducted from January 1, 2017 to March 30, 2018 at Nola prefectural hospital. This study was included all children seen as outpatients and/or hospitalized in the pediatric wards, in whom the diagnosis of HAT was confirmed. Statistical analysis was performed using Epi-info software. Results: Forty children were included from Bilolo (60%), Nola (30%) and Salo (10%). The sex ratio was 0.66 with a median age of 8.65 ± 12.48 years. Fever (82.5%), nocturnal insomnia (75%), daytime somnolence (67.5%), headache (65%), polyarthralgia (62.5%), convulsions 52.5% (n = 21), tremor (27.5%), trypanidism (7.5%) and delirium (2.5%) were the main functional signs. Examination signs were adenopathy (52.5%), paresthesia (30%), decreased cutaneous-abdominal reflexes (25%) and osteoarticular reflexes (17.5%), hyperesthesia (20%), extrapyramidal hypertonia (15%) and depression (2.5%). The children were in the lymphatic-blood phase in 65% of cases, and meningoencephalitis in 35%. Pentamidine was administered in 65% of cases. Four children died and 6 had neurological sequelae. There was an association between age under 5, Bilolo’s focus, the children’s history and the severity of the disease. Age under 5, gender, household, children’s activity, history and occurrence of sequelae were also associated. Conclusion: HAT remains a permanent threat to Central African children. Any clinical presentation combining long-term infectious signs and unexplained neurological or neuropsychological disorders must be treated with caution.
基金National Natural Science Foundation of China (42030608 and 42075079)。
文摘Microwave Radiometer Imager(MWRI) is a key payload of China’s second generation polar meteorological satellite, i.e., Fengyun-3 series(FY-3). Up to now, 5 satellites including FY-3A(2008), FY-3B(2010), FY-3C(2013), FY-3D(2018), and FY-3E(2021) have been launched successfully to provide multiwavelength, all-weather, and global data for decades. Much progress has been made on the calibration of MWRI and a recalibrated MWRI brightness temperature(BT) product(V2) was recently released. This study thoroughly evaluates the accuracy of this new product from FY-3B, 3C, and 3D by using the simultaneous collocated Global Precipitation Measurement(GPM)Microwave Imager(GMI) measurements as a reference. The results show that the mean biases(MBEs) of the BT between MWRI and GMI are generally less than 0.5 K and the root mean squares(RMSs) between them are less than1.5 K. The previous notable ascending and descending difference of the MWRI has disappeared. This indicates that the new MWRI recalibration procedure is very effective in removing potential errors associated with the emission of the hot-load reflector. Analysis of the dependence of MBE on the latitude and earth scene temperature shows that MBE decreases with decreasing latitude over ocean. Furthermore, MBE over ocean decreases linearly with increasing scene temperature for almost all channels, whereas this does not occur over land. A linear regression fitting is then used to modify MWRI, which can reduce the MBE over ocean to be within 0.2 K. The standard deviation of error of GMI, FY-3B, and FY-3D MWRI BT data derived by using the three-cornered hat method(TCH) shows that GMI has the best overall performance over ocean except at 10.65 GHz where its standard deviation of error is slightly larger than that of FY-3D. Over land, the standard deviation of error of FY-3D is the lowest at almost all channels except at 89V. MWRI onboard FY-3 series satellites would serve as an important passive microwave radiometer member of the constellation to monitor key surface and at
