Three stochastic mathematical models for calculation of the reservoir flood regulation process, river course flood release, and flood risk rate under flood control were established based on the theory of stochastic di...Three stochastic mathematical models for calculation of the reservoir flood regulation process, river course flood release, and flood risk rate under flood control were established based on the theory of stochastic differential equations and features of flood control systems in the middle reach of the Huaihe River from Xixian to the Bengbu floodgate, comprehensively considering uncertain factors of hydrology, hydraulics, and engineering control. They were used to calculate the flood risk rate with flood regulation of five key reservoirs, including the Meishan, Xianghongdian, Nianyushan, Mozitan, and Foziling reservoirs in the middle reach of the Huaihe River under different flood frequencies, the flood risk rate with river course flood release under design and check floods for the trunk of the Huaihe River in conjunction with relevant flood storage areas, and the flood risk rate with operation of the Linhuaigang Project under design and check floods. The calculated results show that （l） the five reservoirs can withstand design floods, but the Xianghongdian and Foziling reservoirs will suffer overtopping accidents under check floods; （2） considering the service of flood storage areas under the design flood conditions of the Huaihe River, the mean flood risk rate with flood regulation of dykes and dams from Xixian to the Bengbu floodgate is about 0.2, and the trunk of the Huaihe River can generally withstand design floods; and （3） under a check flood with the flood return period of 1 000 years, the risk rate of overtopping accidents of the Linhuaigang Project is not larger than 0.15, indicating that it has a high flood regulation capacity. Through regulation and application of the flood control system of the Linhuigang Project, the Huaihe River Basin can withstand large floods, and the safety of the protected area can be ensured.展开更多
BACKGROUND Acute severe lower gastrointestinal bleeding(LGIB)is an uncommon but challenging complication of Crohn’s disease(CD).AIM To identify the predictors of acute severe LGIB and to evaluate the impact of acute ...BACKGROUND Acute severe lower gastrointestinal bleeding(LGIB)is an uncommon but challenging complication of Crohn’s disease(CD).AIM To identify the predictors of acute severe LGIB and to evaluate the impact of acute severe LGIB on the subsequent clinical course in CD patients.METHODS A retrospective inception cohort study was conducted in 75 CD patients with acute severe LGIB and 1359 CD patients without acute severe LGIB who were diagnosed between February 1991 and November 2019 at Asan Medical Center,a tertiary university hospital in Korea.Multivariable analysis with Cox proportional hazard regression was performed to identify the risk factors for acute severe LGIB.A matched analysis using 72 patients with bleeding and 267 matched patients without within the cohort was also conducted to investigate whether acute severe LGIB is a predictor of clinical outcomes of CD.RESULTS Multivariable Cox regression analysis revealed that early use of thiopurines[hazard ratio(HR):0.23,95%confidence interval(CI):0.12-0.48;P<0.001]and female sex(HR:0.51,95%CI:0.27-0.94;P=0.031)were significantly associated with a lower risk of acute severe LGIB.The cumulative risks of behavioral progression and intestinal resection were not significantly different between the two matched groups(P=0.139 and P=0.769,respectively).The hospitalization rate was higher in the bleeding group than in the matched non-bleeding group(22.1/100 vs 13.2/100 patient-years;P=0.012).However,if hospitalizations due to bleeding episodes were excluded from the analysis,the hospitalization rate was not significantly different between the bleeding group and the matched nonbleeding group(14.5/100 vs 13.2/100 patient-years;P=0.631).CONCLUSION Early use of thiopurines may reduce the risk of acute severe LGIB.History of acute severe LGIB may not have a significant prognostic value in patients with CD.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51139001)
文摘Three stochastic mathematical models for calculation of the reservoir flood regulation process, river course flood release, and flood risk rate under flood control were established based on the theory of stochastic differential equations and features of flood control systems in the middle reach of the Huaihe River from Xixian to the Bengbu floodgate, comprehensively considering uncertain factors of hydrology, hydraulics, and engineering control. They were used to calculate the flood risk rate with flood regulation of five key reservoirs, including the Meishan, Xianghongdian, Nianyushan, Mozitan, and Foziling reservoirs in the middle reach of the Huaihe River under different flood frequencies, the flood risk rate with river course flood release under design and check floods for the trunk of the Huaihe River in conjunction with relevant flood storage areas, and the flood risk rate with operation of the Linhuaigang Project under design and check floods. The calculated results show that （l） the five reservoirs can withstand design floods, but the Xianghongdian and Foziling reservoirs will suffer overtopping accidents under check floods; （2） considering the service of flood storage areas under the design flood conditions of the Huaihe River, the mean flood risk rate with flood regulation of dykes and dams from Xixian to the Bengbu floodgate is about 0.2, and the trunk of the Huaihe River can generally withstand design floods; and （3） under a check flood with the flood return period of 1 000 years, the risk rate of overtopping accidents of the Linhuaigang Project is not larger than 0.15, indicating that it has a high flood regulation capacity. Through regulation and application of the flood control system of the Linhuigang Project, the Huaihe River Basin can withstand large floods, and the safety of the protected area can be ensured.
文摘BACKGROUND Acute severe lower gastrointestinal bleeding(LGIB)is an uncommon but challenging complication of Crohn’s disease(CD).AIM To identify the predictors of acute severe LGIB and to evaluate the impact of acute severe LGIB on the subsequent clinical course in CD patients.METHODS A retrospective inception cohort study was conducted in 75 CD patients with acute severe LGIB and 1359 CD patients without acute severe LGIB who were diagnosed between February 1991 and November 2019 at Asan Medical Center,a tertiary university hospital in Korea.Multivariable analysis with Cox proportional hazard regression was performed to identify the risk factors for acute severe LGIB.A matched analysis using 72 patients with bleeding and 267 matched patients without within the cohort was also conducted to investigate whether acute severe LGIB is a predictor of clinical outcomes of CD.RESULTS Multivariable Cox regression analysis revealed that early use of thiopurines[hazard ratio(HR):0.23,95%confidence interval(CI):0.12-0.48;P<0.001]and female sex(HR:0.51,95%CI:0.27-0.94;P=0.031)were significantly associated with a lower risk of acute severe LGIB.The cumulative risks of behavioral progression and intestinal resection were not significantly different between the two matched groups(P=0.139 and P=0.769,respectively).The hospitalization rate was higher in the bleeding group than in the matched non-bleeding group(22.1/100 vs 13.2/100 patient-years;P=0.012).However,if hospitalizations due to bleeding episodes were excluded from the analysis,the hospitalization rate was not significantly different between the bleeding group and the matched nonbleeding group(14.5/100 vs 13.2/100 patient-years;P=0.631).CONCLUSION Early use of thiopurines may reduce the risk of acute severe LGIB.History of acute severe LGIB may not have a significant prognostic value in patients with CD.
