The need for interval appendicectomy (I.A) after successful conservative management of appendiceal mass has recently been questioned.Furthermore,emergency appendicectomy for appendiceal mass is increasingly performed ...The need for interval appendicectomy (I.A) after successful conservative management of appendiceal mass has recently been questioned.Furthermore,emergency appendicectomy for appendiceal mass is increasingly performed with equal success and safety to that performed in non-mass forming acute appendicitis.There is an increasing volume of evidence-although mostly retrospective-that if traditional conservative management is adopted,there is no need for routine I.A except for a small number of patients who continue to develop recurrent symptoms.On the other hand,the routine adoption of emergency laparoscopic appendicectomy (LA) in patients presenting with appendiceal mass obviates the need for a second admission and an operation for I.A with a considerable complication rate.It also abolishes misdiagnoses and deals promptly with any unexpected ileo-cecal pathology.Moreover,it may prove to be more cost-effective than conservative treatment even without I.A due to a much shorter hospital stay and a shorter period of intravenous antibiotic administration.If emergency LA is to become the standard of care for appendiceal mass,I.A will certainly become 'something' of the past.展开更多
In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and cost minimum is introduced in this paper. The estimation of syst...In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and cost minimum is introduced in this paper. The estimation of system reliability is presented by using two-parameter Weibull distributions. The parameters are estimated by using Weibull probability statistical analysis and the practical operational data. Then, the maintenance optimization model isformulated where the objective function is to minimize the expected schedule maintenance cost in a time unit. The results of numerical example show that the proposed model could scheme the optimal maintenance intervals for the considered system when the parameters are given. This research has certain significance in theoryand engineering practice.展开更多
This paper proposed a method of optimal economic life interval evaluation of transformer, thus providing scientific support for power system planning and reconstruction. First, obtaining the transformer failure rate b...This paper proposed a method of optimal economic life interval evaluation of transformer, thus providing scientific support for power system planning and reconstruction. First, obtaining the transformer failure rate by using Levenberg-Marquardt based least squares algorithm on the consumption that transformer failure mode meets three-parameters Weibull distribution. Second, calculating operation cost and failure cost of transformer during its life cycle on the basis of transformer failure rate. Then, acquiring the optimal economic life interval of transformer through life cycle minimal average annual cost based on the theory of interval analysis. Finally, the proposed method is proved to be effective by applying to some real transformers.展开更多
文摘The need for interval appendicectomy (I.A) after successful conservative management of appendiceal mass has recently been questioned.Furthermore,emergency appendicectomy for appendiceal mass is increasingly performed with equal success and safety to that performed in non-mass forming acute appendicitis.There is an increasing volume of evidence-although mostly retrospective-that if traditional conservative management is adopted,there is no need for routine I.A except for a small number of patients who continue to develop recurrent symptoms.On the other hand,the routine adoption of emergency laparoscopic appendicectomy (LA) in patients presenting with appendiceal mass obviates the need for a second admission and an operation for I.A with a considerable complication rate.It also abolishes misdiagnoses and deals promptly with any unexpected ileo-cecal pathology.Moreover,it may prove to be more cost-effective than conservative treatment even without I.A due to a much shorter hospital stay and a shorter period of intravenous antibiotic administration.If emergency LA is to become the standard of care for appendiceal mass,I.A will certainly become 'something' of the past.
文摘In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and cost minimum is introduced in this paper. The estimation of system reliability is presented by using two-parameter Weibull distributions. The parameters are estimated by using Weibull probability statistical analysis and the practical operational data. Then, the maintenance optimization model isformulated where the objective function is to minimize the expected schedule maintenance cost in a time unit. The results of numerical example show that the proposed model could scheme the optimal maintenance intervals for the considered system when the parameters are given. This research has certain significance in theoryand engineering practice.
文摘This paper proposed a method of optimal economic life interval evaluation of transformer, thus providing scientific support for power system planning and reconstruction. First, obtaining the transformer failure rate by using Levenberg-Marquardt based least squares algorithm on the consumption that transformer failure mode meets three-parameters Weibull distribution. Second, calculating operation cost and failure cost of transformer during its life cycle on the basis of transformer failure rate. Then, acquiring the optimal economic life interval of transformer through life cycle minimal average annual cost based on the theory of interval analysis. Finally, the proposed method is proved to be effective by applying to some real transformers.
