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Surrogate models have been widely adopted for reliability analysis. The common approach is to construct a series of surrogates based on a training set and then pick out the best one with the highest accuracy as an approximation of the time-consuming limit state function. However, the traditional method increases the risk of adopting an inappropriate model and does not take full advantage of the data devoted to constructing different surrogates. Furthermore, obtaining more samples is very expensive and sometimes even impossible. Therefore, to save the cost of constructing the surrogate and improve the prediction accuracy, an ensemble strategy is proposed in this paper for efficiently analyzing the structural reliability. The values of the weights are obtained by a recursive process and the leave-one-out technique, in which the values are updated in each iteration until a given prediction accuracy is achieved. Besides, a learning function is used to guide the selection of the next sampling candidate. Because the learning function utilizes the uncertainty estimator of the surrogate to guide the design of experiments (DoE), to accurately calculate the uncertainty estimator of the ensemble of surrogates, the concept of weighted mean square error is proposed. After the high-quality ensemble of surrogates of the limit state function is available, the Monte Carlo method is employed to calculate the failure probabilities. The proposed method is evaluated by three analytic problems and one engineering problem. The results show that the proposed ensemble of surrogates has better prediction accuracy and robustness than the stand-alone surrogates and the existing ensemble techniques. [ABSTRACT FROM AUTHOR]

Background. Nosocomial EVD-related ventriculitis is a major complication and a significant cause of morbidity and mortality in critically ill neurological patients. Questions remain about best management of EVDs. The purpose of this study is to compare our incidence of ventriculitis to studies using different catheters and/or antibiotic coverage schemes and determine whether c-EVD with prolonged antibiotics given for the duration of drain placement is inferior to ac-EVD with pp-abx or ac-EVD with prolonged antibiotics for prevention of ventriculitis. Methods. A retrospective chart review of all patients who had EVDs placed from January 2010 through December 2015 at home institution was performed. Statistical analysis was performed using Fisher’s exact test to compare incidence of ventriculitis identified in other studies with that of home institution. Results. The study included 107 patients, 66 (61.7%) males and 41 (38.3%) females. Average age was 56 years ranging from 18 to 95 years. Average length of drain placement was 7.8 days ranging from 2 to 23 days. Average length of drain placement in infected drains was 13.3 days ranging from 11 to 15 days. There were 3 cases with positive CSF cultures (Staphylococcus haemolyticus and Staphylococcus epidermidis x 2). There were 2 cases with a CSF having a positive gram stain but failed to yield any bacterial growth on culture and did not meet predefined criteria. Conclusions. The c-EVD with prolonged antibiotics given for the duration of drain placement is not inferior to ac-EVD with pp-abx or ac-EVD with prolonged antibiotics for prevention of ventriculitis. The c-EVD with prolonged antibiotics is superior to c-EVD with pp-abx and conventional EVD without antibiotics for prevention of ventriculitis. Selection should include considerations for antibiotic stewardship and cost effectiveness. Future studies should also utilize clinical and CSF profile criteria in addition to positive CSF cultures for identifying ventriculitis to prevent line colonization from classification as ventriculitis in analysis. [ABSTRACT FROM AUTHOR]