Central bank digital currencies(CBDCs),which are legal tenders in digital form,are expected to reduce currency issuance and circulation costs and broaden the scope of monetary policy.In addition,these currencies may a...Central bank digital currencies(CBDCs),which are legal tenders in digital form,are expected to reduce currency issuance and circulation costs and broaden the scope of monetary policy.In addition,these currencies may also reduce consumers’need for conventional demand deposits,which,in turn,increases banks’loan provision costs because deposits require higher rates of return.We use a microeconomic banking model to investigate the effects of introducing an economy-wide,account-type CBDC on a bank’s loan supply and its failure risk.Given that a CBDC is expected to lower the cost of liquidity circulation and become a strong substitute for demand deposits,both the loan supply and the bank failure risk increase.These increases are countered by subsequent increases in the rates of return on term deposits and loans,which,in turn,reduce the loan supply and thus bank failure risk.These offsetting forces lead to no significant change in banking,as long as the rate of return on loans is below a certain threshold.However,once the rate is above the threshold,bank failure risk increases,thereby undermining banking stability.The problem is more pronounced when the degree of pass-through of funding costs to the loan rate is high and the profitability of a successful project is low.Our results imply that central banks wishing to introduce an economy-wide,account-type CBDC should first monitor yields on bank loans and consider policy measures that induce banks to maintain adequate liquidity reserve levels.展开更多
In single-or multi-infeed line-commutated converter-based high-voltage direct current(LCC-HVDC) systems, commutation failure(CF) induced by alternating current(AC) faults may lead to serious consequences. Considering ...In single-or multi-infeed line-commutated converter-based high-voltage direct current(LCC-HVDC) systems, commutation failure(CF) induced by alternating current(AC) faults may lead to serious consequences. Considering the randomness of fault occurrences, an accurate evaluation of the CF risk(CFR) from the system point of view becomes necessary in power system planning and operation. This paper first provides a definition of the CF severity(CFS) index corresponding to an AC fault. Then,on the basis of electromagnetic transient(EMT) simulation, an approach to calculate the CFS index considering the randomness of fault-occurrence time is presented. A novel equivalent-fault method is further put forward to make the EMT simulation scalable to calculate the CFS index in terms of a fault occurring in a large-scale receiving-end grid. Thereafter, the CFR index is introduced, which is defined as the sum of the products of the CFS index of each AC fault and the corresponding fault rate.Finally, the proposed method is verified on the modified IEEE 9-bus and modified IEEE 39-bus systems using PSCAD/EMTDC.展开更多
The objective of this prospective study of the risks of treatment failure in patients with drug-susceptible pulmonary tuberculosis (PTB) was to provide reference data to help develop a disease control strategy. Part...The objective of this prospective study of the risks of treatment failure in patients with drug-susceptible pulmonary tuberculosis (PTB) was to provide reference data to help develop a disease control strategy. Participants were recruited in eight provinces of China from October 2008 to December 2010. A total of 1447 patients with drug-susceptible PTB and older than 15 years of age were enrolled.展开更多
Objective To evaluate risk factors for postoperative acute renal failure requiring dialysis (ARF-D) after hear valve surgery. Methods Adult patients (age≤18 years) underwent valve surgery with preoperative serum crea...Objective To evaluate risk factors for postoperative acute renal failure requiring dialysis (ARF-D) after hear valve surgery. Methods Adult patients (age≤18 years) underwent valve surgery with preoperative serum creati nine 【 300 μmol / L were included between January 2005 and December 2008. Fifty patients developed ARF-D展开更多
In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage hap...In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning.展开更多
AIM:To investigate the long-term outcome of recipients and donors of adult-to-adult living-donor liver transplantation(AALDLT) for acute liver failure(ALF).METHODS:Between January 2005 and March 2010,170 living donor ...AIM:To investigate the long-term outcome of recipients and donors of adult-to-adult living-donor liver transplantation(AALDLT) for acute liver failure(ALF).METHODS:Between January 2005 and March 2010,170 living donor liver transplantations were performed at West China Hospital of Sichuan University.All living liver donor was voluntary and provided informed consent.Twenty ALF patients underwent AALDLT for rapid deterioration of liver function.ALF was defined based on the criteria of the American Association for the Study of Liver Diseases,including evidence of coagulation abnormality [international normalized ratio(INR) ≥ 1.5] and degree of mental alteration without pre-ex-isting cirrhosis and with an illness of < 26 wk duration.We reviewed the clinical indications,operative procedure and prognosis of AALDTL performed on patients with ALF and corresponding living donors.The potential factors of recipient with ALF and corresponding donor outcome were respectively investigated using multivariate analysis.Survival rates after operation were analyzed using the Kaplan-Meier method.Receiver operator characteristic(ROC) curve analysis was undertaken to identify the threshold of potential risk factors.RESULTS:The causes of ALF were hepatitis B(n = 18),drug-induced(n = 1) and indeterminate(n = 1).The score of the model for end-stage liver disease was 37.1 ± 8.6,and the waiting duration of recipients was 5 ± 4 d.The graft types included right lobe(n = 17) and dual graft(n = 3).The mean graft weight was 623.3 ± 111.3 g,which corresponded to graft-torecipient weight ratio of 0.95% ± 0.14%.The segment Ⅴor Ⅷ hepatic vein was reconstructed in 11 right-lobe grafts.The 1-year and 3-year recipient's survival and graft survival rates were 65%(13 of 20).Postoperative results of total bilirubin,INR and creatinine showed obvious improvements in the survived patients.However,the creatinine level of the deaths was increased postoperatively and became more aggravated compared with the level of the survived recipients.Multivariate analysis showed that waiting duration was independently correlated with increased mortality(P = 0.014).Furthermore,ROC curve revealed the cut-off value of waiting time was 5 d(P = 0.011,area under the curve = 0.791) for determining the mortality.The short-term creatinine level with different recipient's waiting duration was described.The recipients with waiting duration ≥ 5 d showed the worse renal function and higher mortality than those with waiting duration < 5 d(66.7% vs 9.1%,P = 0.017).In addition,all donors had no residual morbidity.Furthermore,univariate analysis did not show that short assessment time induced the high morbidity(P = 0.573).CONCLUSION:Timely AALDLT for patients with ALF greatly improves the recipient survival.However,further systemic review is needed to investigate the optimal treatment strategy for ALF.展开更多
Objectives Evaluation of patients with acute chest pain when they admitted is time-consuming. We prospectively investigated the role of bedside troponin T test for predicting the risk of death and acute heart failure ...Objectives Evaluation of patients with acute chest pain when they admitted is time-consuming. We prospectively investigated the role of bedside troponin T test for predicting the risk of death and acute heart failure of patients with acute chest pain.Methods and Results 502 consecutive patients with chest pain for less than 24 hours were determined by troponin T test at bedside and quantitative troponin I test in lab. For bedside troponin T tests, there were 160 patients in positive and 323 in negative. During 30 days of followed-up. Myocardial infarction evolved in 139 patients among 160 patients in positive troponin T test, only 7 patients in negative one. Acute heart failure occurred in 51 patients among the positive group, but 37 occurred it at negative group. The odds ratio of acute heart failure of positive group vs. negative group was 3.6. Patients died 39 in positive group, 15 in negative group, the all-cause death odds ratio of positive group vs. negative group was 6.7; 31 patients died with cardiac event in positive group, 5 in negative group only. Conclusions Bedside Troponin T test is a powerful and independent predictor of death and acute heart failure for patients with acute chest pain.展开更多
It is of great importance to establish the dam failure risk criteria for dam risk assessment and management. Presently, the F-N curve method is widely applied in practice, in which the F-N curves are used for establis...It is of great importance to establish the dam failure risk criteria for dam risk assessment and management. Presently, the F-N curve method is widely applied in practice, in which the F-N curves are used for establishing the criteria for separate risks caused by the dam failure in life, economy, environment, and society respectively. In this paper, in consideration of the overlying effect by two or more types of risk losses resulting from the dam failure at the same time, the F-N curved surface method is presented for establishing the integrated dam failure risk criteria. In this method, the named F-N curved surfaces are established, and by these curved surfaces, the acceptable, the allowable, and the unallowable integrated risk zones can be defined.展开更多
After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To redu...After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also analyzed.The experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,respectively.Among these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.展开更多
Background Acute kidney injury (AKI) is considered as a common and significant complication following abdominal aortic aneurysm (AAA) repair. This study aimed to assess the associated risk factors of AKI in the cr...Background Acute kidney injury (AKI) is considered as a common and significant complication following abdominal aortic aneurysm (AAA) repair. This study aimed to assess the associated risk factors of AKI in the critically ill patients undergoing AAA repair and to evaluate the appropriate AKI management in the specific population. Methods We retrospectively examined data from all critically ill patients undergoing AAA repairs at our institution from April 2007 to March 2012. Multivariable analysis was used to identify factors associated with postoperative AKI, which was defined by risk, injury, failure, loss and end-stage (RIFLE) kidney disease criteria. The goal-directed hemodynamic optimization (maintenance of optimal hemodynamics and neutral or negative fluid balance) and renal outcomes were also reviewed. Results Of the 71 patients enrolled, 32 (45.1%) developed AKI, with 30 (93.8%) cases diagnosed on admission to surgical intensive care unit (SICU). Risk factors for AKI were ruptured AAA (odds ratio (OR)=5.846, 95% confidence interval (CI): 1.346-25.390), intraoperative hypotension (OR=6.008, 95% CI: 1.176 to 30.683), and perioperative blood transfusion (OR=4.611, 95% CI: 1.307-16.276). Goal-directed hemodynamic optimization resulted in 75.0% complete and 18.8% partial renal recovery. Overall in-hospital mortality was 2.8%. AKI was associated with significantly increased length of stay ((136.9±24.5) hours vs. (70.4±11.3) hours) in Surgical Intensive Care Unit. Conclusions Critically ill patients undergoing AAA repair have a high incidence of AKI, which can be early recognized by RIFLE criteria. Rupture, hypotension, and blood transfusion are the significant associated risk factors. Application of goal-directed hemodynamic optimization in this cohort appeared to be effective in improving renal outcome.展开更多
This paper proposes a new method for power transmission risk assessment considering historical failure statistics of transmission systems and operation failure risks of system components.Component failure risks are in...This paper proposes a new method for power transmission risk assessment considering historical failure statistics of transmission systems and operation failure risks of system components.Component failure risks are integrated into the new method based on operational condition assessment of components using the support vector data description(SVDD)approach.The traditional outage probability model of transmission lines has been modified to build a new framework for power transmission system risk assessment.The proposed SVDD approach can provide a suitable mechanism to map component assessment grades to failure risks based on probabilistic behaviors of power system failures.Under the new method,both up-todate component failure risks and traditional system risk indices can be processed with the proposed outage model.As a result,component failure probabilities are not only related to historical statistic data but also operational data of components,and derived risk indices can reflect current operational conditions of components.In simulation studies,the SVDD approach is employed to evaluate component conditions and link such conditions to failure rates using up-to-date component operational data,including both on-line and off-line data of components.The IEEE 24-bus RTS-1979 system is used to demonstrate that component operational conditions can greatly affect the overall transmission system failure risks.展开更多
Check dams are widely used throughout the world to tackle soil and water lOSS.However,the ffequency of extreme rainfall events has increased owing to global climate change and the main structure of check dam is gradua...Check dams are widely used throughout the world to tackle soil and water lOSS.However,the ffequency of extreme rainfall events has increased owing to global climate change and the main structure of check dam is gradually aging.which lead to an increase in the failure risk ofcheck dams.Thus.it is necessary to carry out the study on failure risk diagnosis and assessment of check dams.In the study,machine learning algorithms(ML).including random forests(RF).support vector machine(SVM),and logistic regression(LR).were used to integrate the environmental and engineering factors and then assess the risk of check dam failure due to the“7.26”rainstorm on Iuly 26.2017,in the Chabagou watershed.10cated in the hilly—gully region of the Loess Plateau.China.To veri~the generalizability of the model in this study。these models were used for the Wangmaogou catchment north of the Loess Plateau.The accuracy assessment by the receiver operating Characteristic fROCl curve indicated that the RF model with an area under the ROC curve fAUCl greater than 0.89 was the most precise model and had a higher general—ization ability.In addition.the model dataset was relatively smalI and easy to obtain.which make the risk modeling of check dam failure in the study has the potential for application in other regions.In the RF model.each factor selected was confirmed to be important,and the importance values for engineering factors were generally higher than those for the environmental factors.The risk map of check dam failure in the RF modelindicated that 56.34%of check dams in the study area had very high and high risks of dam failure under high—intensity rainfall in 2017.Based on the importance of factors and the risk map of check dam failure.the prevention and control measures for reducing the risk of check dam failure and promoting the construction of check dam are proposed.These proposals provide a scientific basis for the reinforcement of check dams and the future layout of check dams in the Chinese Loess Plateau.展开更多
基金support from the National Research Foundation of Korea funded by the Ministry of Education(NRF-2020S1A5A8044620).
文摘Central bank digital currencies(CBDCs),which are legal tenders in digital form,are expected to reduce currency issuance and circulation costs and broaden the scope of monetary policy.In addition,these currencies may also reduce consumers’need for conventional demand deposits,which,in turn,increases banks’loan provision costs because deposits require higher rates of return.We use a microeconomic banking model to investigate the effects of introducing an economy-wide,account-type CBDC on a bank’s loan supply and its failure risk.Given that a CBDC is expected to lower the cost of liquidity circulation and become a strong substitute for demand deposits,both the loan supply and the bank failure risk increase.These increases are countered by subsequent increases in the rates of return on term deposits and loans,which,in turn,reduce the loan supply and thus bank failure risk.These offsetting forces lead to no significant change in banking,as long as the rate of return on loans is below a certain threshold.However,once the rate is above the threshold,bank failure risk increases,thereby undermining banking stability.The problem is more pronounced when the degree of pass-through of funding costs to the loan rate is high and the profitability of a successful project is low.Our results imply that central banks wishing to introduce an economy-wide,account-type CBDC should first monitor yields on bank loans and consider policy measures that induce banks to maintain adequate liquidity reserve levels.
基金supported by the National Key R&D Program of China(Grant No.2016YFB0900600)Technology Projects of State Grid Corporation of China(Grant No.52094017000W)
文摘In single-or multi-infeed line-commutated converter-based high-voltage direct current(LCC-HVDC) systems, commutation failure(CF) induced by alternating current(AC) faults may lead to serious consequences. Considering the randomness of fault occurrences, an accurate evaluation of the CF risk(CFR) from the system point of view becomes necessary in power system planning and operation. This paper first provides a definition of the CF severity(CFS) index corresponding to an AC fault. Then,on the basis of electromagnetic transient(EMT) simulation, an approach to calculate the CFS index considering the randomness of fault-occurrence time is presented. A novel equivalent-fault method is further put forward to make the EMT simulation scalable to calculate the CFS index in terms of a fault occurring in a large-scale receiving-end grid. Thereafter, the CFR index is introduced, which is defined as the sum of the products of the CFS index of each AC fault and the corresponding fault rate.Finally, the proposed method is verified on the modified IEEE 9-bus and modified IEEE 39-bus systems using PSCAD/EMTDC.
基金supported by the National Science and Technology Major Project of China(2008ZX10003-008-02)
文摘The objective of this prospective study of the risks of treatment failure in patients with drug-susceptible pulmonary tuberculosis (PTB) was to provide reference data to help develop a disease control strategy. Participants were recruited in eight provinces of China from October 2008 to December 2010. A total of 1447 patients with drug-susceptible PTB and older than 15 years of age were enrolled.
文摘Objective To evaluate risk factors for postoperative acute renal failure requiring dialysis (ARF-D) after hear valve surgery. Methods Adult patients (age≤18 years) underwent valve surgery with preoperative serum creati nine 【 300 μmol / L were included between January 2005 and December 2008. Fifty patients developed ARF-D
基金Supported by National Science and Technology Pillar Program in the Twelfth Five-Year Plan (No. 2011BAK06B02)National Basic Research Program of China ("973" Program, No. 2012CB026000)
文摘In petrochemical plant, the in-operation repairing is usually a repairing strategy with pressured inoperation repairing for avoiding huge economic losses caused by unplanned shutdown when some slight local leakage happens in pipes. This paper studies the effects of repairing strategies on the failure probability of the pipe systems in process industries based on the time-average fault tree approach, especially the in-operation repairing strategies including pressured in-operation repairing activities. The fault tree model can predict the effect of different repairing plans on the pipe failure probability, which is significant to the optimization of the repairing plans. At first pipes are distinguished into four states in this model, i.e., successive state, flaw state, leakage state and failure state. Then the fault tree approach, which is usually applied in the studies of dynamic equipment, is adopted to model the pipe failure. Moreover, the effect of pressured in-operation repairing is also considered in the model. In addition, this paper proposes a series of time-average parameters of the fault tree model, all of which are used to calculate node parameters of the fault tree model. At last, a practical case is calculated based on the fault tree model in a repairing activity of pipe thinning.
基金Supported by The National Natural Science Foundation of China,No. 30901720PhD Programs of Ministry of Education of China,No. 20090181120111
文摘AIM:To investigate the long-term outcome of recipients and donors of adult-to-adult living-donor liver transplantation(AALDLT) for acute liver failure(ALF).METHODS:Between January 2005 and March 2010,170 living donor liver transplantations were performed at West China Hospital of Sichuan University.All living liver donor was voluntary and provided informed consent.Twenty ALF patients underwent AALDLT for rapid deterioration of liver function.ALF was defined based on the criteria of the American Association for the Study of Liver Diseases,including evidence of coagulation abnormality [international normalized ratio(INR) ≥ 1.5] and degree of mental alteration without pre-ex-isting cirrhosis and with an illness of < 26 wk duration.We reviewed the clinical indications,operative procedure and prognosis of AALDTL performed on patients with ALF and corresponding living donors.The potential factors of recipient with ALF and corresponding donor outcome were respectively investigated using multivariate analysis.Survival rates after operation were analyzed using the Kaplan-Meier method.Receiver operator characteristic(ROC) curve analysis was undertaken to identify the threshold of potential risk factors.RESULTS:The causes of ALF were hepatitis B(n = 18),drug-induced(n = 1) and indeterminate(n = 1).The score of the model for end-stage liver disease was 37.1 ± 8.6,and the waiting duration of recipients was 5 ± 4 d.The graft types included right lobe(n = 17) and dual graft(n = 3).The mean graft weight was 623.3 ± 111.3 g,which corresponded to graft-torecipient weight ratio of 0.95% ± 0.14%.The segment Ⅴor Ⅷ hepatic vein was reconstructed in 11 right-lobe grafts.The 1-year and 3-year recipient's survival and graft survival rates were 65%(13 of 20).Postoperative results of total bilirubin,INR and creatinine showed obvious improvements in the survived patients.However,the creatinine level of the deaths was increased postoperatively and became more aggravated compared with the level of the survived recipients.Multivariate analysis showed that waiting duration was independently correlated with increased mortality(P = 0.014).Furthermore,ROC curve revealed the cut-off value of waiting time was 5 d(P = 0.011,area under the curve = 0.791) for determining the mortality.The short-term creatinine level with different recipient's waiting duration was described.The recipients with waiting duration ≥ 5 d showed the worse renal function and higher mortality than those with waiting duration < 5 d(66.7% vs 9.1%,P = 0.017).In addition,all donors had no residual morbidity.Furthermore,univariate analysis did not show that short assessment time induced the high morbidity(P = 0.573).CONCLUSION:Timely AALDLT for patients with ALF greatly improves the recipient survival.However,further systemic review is needed to investigate the optimal treatment strategy for ALF.
文摘Objectives Evaluation of patients with acute chest pain when they admitted is time-consuming. We prospectively investigated the role of bedside troponin T test for predicting the risk of death and acute heart failure of patients with acute chest pain.Methods and Results 502 consecutive patients with chest pain for less than 24 hours were determined by troponin T test at bedside and quantitative troponin I test in lab. For bedside troponin T tests, there were 160 patients in positive and 323 in negative. During 30 days of followed-up. Myocardial infarction evolved in 139 patients among 160 patients in positive troponin T test, only 7 patients in negative one. Acute heart failure occurred in 51 patients among the positive group, but 37 occurred it at negative group. The odds ratio of acute heart failure of positive group vs. negative group was 3.6. Patients died 39 in positive group, 15 in negative group, the all-cause death odds ratio of positive group vs. negative group was 6.7; 31 patients died with cardiac event in positive group, 5 in negative group only. Conclusions Bedside Troponin T test is a powerful and independent predictor of death and acute heart failure for patients with acute chest pain.
基金supported by the National Natural Science Foundation of China (Grant No. 50779009)
文摘It is of great importance to establish the dam failure risk criteria for dam risk assessment and management. Presently, the F-N curve method is widely applied in practice, in which the F-N curves are used for establishing the criteria for separate risks caused by the dam failure in life, economy, environment, and society respectively. In this paper, in consideration of the overlying effect by two or more types of risk losses resulting from the dam failure at the same time, the F-N curved surface method is presented for establishing the integrated dam failure risk criteria. In this method, the named F-N curved surfaces are established, and by these curved surfaces, the acceptable, the allowable, and the unallowable integrated risk zones can be defined.
基金supported by National Natural Science Foundation of China(No.U1834204)。
文摘After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also analyzed.The experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,respectively.Among these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.
文摘Background Acute kidney injury (AKI) is considered as a common and significant complication following abdominal aortic aneurysm (AAA) repair. This study aimed to assess the associated risk factors of AKI in the critically ill patients undergoing AAA repair and to evaluate the appropriate AKI management in the specific population. Methods We retrospectively examined data from all critically ill patients undergoing AAA repairs at our institution from April 2007 to March 2012. Multivariable analysis was used to identify factors associated with postoperative AKI, which was defined by risk, injury, failure, loss and end-stage (RIFLE) kidney disease criteria. The goal-directed hemodynamic optimization (maintenance of optimal hemodynamics and neutral or negative fluid balance) and renal outcomes were also reviewed. Results Of the 71 patients enrolled, 32 (45.1%) developed AKI, with 30 (93.8%) cases diagnosed on admission to surgical intensive care unit (SICU). Risk factors for AKI were ruptured AAA (odds ratio (OR)=5.846, 95% confidence interval (CI): 1.346-25.390), intraoperative hypotension (OR=6.008, 95% CI: 1.176 to 30.683), and perioperative blood transfusion (OR=4.611, 95% CI: 1.307-16.276). Goal-directed hemodynamic optimization resulted in 75.0% complete and 18.8% partial renal recovery. Overall in-hospital mortality was 2.8%. AKI was associated with significantly increased length of stay ((136.9±24.5) hours vs. (70.4±11.3) hours) in Surgical Intensive Care Unit. Conclusions Critically ill patients undergoing AAA repair have a high incidence of AKI, which can be early recognized by RIFLE criteria. Rupture, hypotension, and blood transfusion are the significant associated risk factors. Application of goal-directed hemodynamic optimization in this cohort appeared to be effective in improving renal outcome.
文摘This paper proposes a new method for power transmission risk assessment considering historical failure statistics of transmission systems and operation failure risks of system components.Component failure risks are integrated into the new method based on operational condition assessment of components using the support vector data description(SVDD)approach.The traditional outage probability model of transmission lines has been modified to build a new framework for power transmission system risk assessment.The proposed SVDD approach can provide a suitable mechanism to map component assessment grades to failure risks based on probabilistic behaviors of power system failures.Under the new method,both up-todate component failure risks and traditional system risk indices can be processed with the proposed outage model.As a result,component failure probabilities are not only related to historical statistic data but also operational data of components,and derived risk indices can reflect current operational conditions of components.In simulation studies,the SVDD approach is employed to evaluate component conditions and link such conditions to failure rates using up-to-date component operational data,including both on-line and off-line data of components.The IEEE 24-bus RTS-1979 system is used to demonstrate that component operational conditions can greatly affect the overall transmission system failure risks.
基金financial support was provided by National Natural Science Foundation of China(U2243213)Jianqiao Han reports financial support was provided by National Natural Science Foundation of China(42177327)Jianqiao Han reports financial support was provided by National Natural Science Foundation of China(U2243212).
文摘Check dams are widely used throughout the world to tackle soil and water lOSS.However,the ffequency of extreme rainfall events has increased owing to global climate change and the main structure of check dam is gradually aging.which lead to an increase in the failure risk ofcheck dams.Thus.it is necessary to carry out the study on failure risk diagnosis and assessment of check dams.In the study,machine learning algorithms(ML).including random forests(RF).support vector machine(SVM),and logistic regression(LR).were used to integrate the environmental and engineering factors and then assess the risk of check dam failure due to the“7.26”rainstorm on Iuly 26.2017,in the Chabagou watershed.10cated in the hilly—gully region of the Loess Plateau.China.To veri~the generalizability of the model in this study。these models were used for the Wangmaogou catchment north of the Loess Plateau.The accuracy assessment by the receiver operating Characteristic fROCl curve indicated that the RF model with an area under the ROC curve fAUCl greater than 0.89 was the most precise model and had a higher general—ization ability.In addition.the model dataset was relatively smalI and easy to obtain.which make the risk modeling of check dam failure in the study has the potential for application in other regions.In the RF model.each factor selected was confirmed to be important,and the importance values for engineering factors were generally higher than those for the environmental factors.The risk map of check dam failure in the RF modelindicated that 56.34%of check dams in the study area had very high and high risks of dam failure under high—intensity rainfall in 2017.Based on the importance of factors and the risk map of check dam failure.the prevention and control measures for reducing the risk of check dam failure and promoting the construction of check dam are proposed.These proposals provide a scientific basis for the reinforcement of check dams and the future layout of check dams in the Chinese Loess Plateau.