Search

In this paper the accelerated aging experiments of oil-paper insulation are carried out to simulate the oil-paper aging process under normal thermal aging process. On the basis of the results of accelerated aging experiments, how the deviation degree of aging status change under the same aging factors is studied, and a method to calculate the failure probability due to the loss of mechanical strength of the insulation is put forward. This paper presents an approach for economic assessment on insulation diagnosis through accelerated aging experiments. The foundation of this approach for economic assessment on insulation diagnosis is to establish condition simulation method of triple relationships between condition status, aging time and failure probability according to data from accelerated aging experiments. The conclusions are made that the economic and technical factors can affect the optimum life cycle cost of each maintenance strategy, which consequently affects the economic feasibility of condition-based maintenance strategies. [ABSTRACT FROM AUTHOR]

Introduction: Red blood cell distribution width (RDW), a measure of heterogeneity in the size of circulating red blood cells, is predictive of adverse outcomes in a variety of diseases. We assessed the prognostic value of RDW in patients with atherosclerotic cardiovascular disease (ASCVD). Methods: We studied 7,849 patients (69±11 years, 65% male) referred to the noninvasive vascular laboratories at Mayo Clinic from January 2005 to March 2013 with follow up through March 2018. Baseline RDW, comorbidities, and mortality were obtained from the electronic health record (EHR). ASCVD phenotypes, namely, abdominal aortic aneurysm (AAA), cerebrovascular disease (CVD), coronary heart disease (CHD), and peripheral artery disease (PAD), were ascertained by validated electronic phenotyping algorithms that included ICD-9-CM and CPT codes, lab values, and medications. Extended multivariable Cox regression models that included a time-dependent coefficient were used to examine changes in the association between RDW and mortality over time. Results: The median RDW was 13.5 (1.3)%, and was highest in PAD patients 13.7 (1.6)%. During the mean follow up of 7.7 years, 1,900 patients (24.2%) died (Table). In Cox models stratified by ASCVD subtypes, with adjustment for age, sex and comorbidities, RDW was independently associated with mortality in all four ASCVD phenotypes. For a unit increase in RDW, impact on mortality was greatest within the first 3 years following the baseline measurement (p-value; AAA 0.02, PAD, CVD, and CHD <0.001), attenuated thereafter and was not significant beyond 5 years (Table). Conclusions: RDW is an independent predictor of near-term mortality across the spectrum of ASCVD and may be useful for prognostication. [ABSTRACT FROM AUTHOR]

Introduction: We investigated the predictive power of a machine learning (ML) algorithm for 5-year mortality in patients with atherosclerotic cardiovascular disease (ASCVD). Candidate features included clinical variables from the electronic health record (EHR) as well as self-reported health and lifestyle data. Methods: The study cohort included 4,689 patients (66±11 years, 62% male) with ASCVD enrolled in the Vascular Disease Biorepository, which recruits patients referred to noninvasive vascular evaluation at Mayo Clinic, Rochester, MN. Clinical variables including comorbidities, lab measurements, and medication use were obtained from the EHR using validated electronic phenotyping algorithms. Information regarding social habits, physical activity levels, and personal health was obtained from a survey filled by the participants. Mortality was ascertained from the national death index. Clinical variables (n=52) and self-reported variables related to health and lifestyle habits (n=48) were added as individual features to reinforcement learning trees (RLT), a sparse decision tree algorithm, to construct the prediction model. We assessed the impact of each feature on prediction accuracy by applying feature selection and computing variable importance (VI). Results: Features with trivial VI that made no contribution to prediction were excluded. A model with 15 features had an area under the ROC curve (AUC) of 0.82 [95% CI 0.79 - 0.83] in the test set. Among the top 10 predictors of 5-year mortality, 6 were self-reported health variables (Table) , including outlook on personal health, limitations on routine daily activities, and physical activity levels. Conclusions: A ML approach had robust discrimination (AUC 0.82) in predicting 5-year mortality in patients with ASCVD. Self-reported health variables were among the top predictive features in the final model. [ABSTRACT FROM AUTHOR]

In this paper, the design method of dc capacitor bushing core has been studied. According to the derived epoxy/paper composite life model, the bushing core design methods are proposed based on the life of materials, which can make a more reasonable electric field distribution within bushing core. By adjusting the size of plates, the insulation life of innermost and outermost of the bushing core is made to be equivalent, resulting in more efficiency in usage of insulation material. Taking 800 kV dry bushing for example, the optimization size is designed. An iterative algorithm is used to optimize the design of the bushing core to minimize the volume of bushing core, while meeting the maximum designed withstand field strength under the ac and dc voltage. [ABSTRACT FROM AUTHOR]

The outstanding problems of water injection wells in an oilfield in Bohai are high injection pressure and shorter validity acidification. Combining the geologic feature of reservoir and the waterflooding development history, the subjects were systematically studied, such as the compatibility of mixed fresh water and polymer-contained sewage, the components of suspended matters, the micro-structures and molecular size of HPAM, the compatibility of injection water and cores, etc. Researches show that suspended solids jam is the main damage forms. Suspended matters are main the flocculation products of the produced polymer with the wastewater treating agents and Ca2+, Mg2+ bivalent cationic, etc. Secondly, they also contain the precipitation of formation fines and produced polymer. Meanwhile, the suspended matters include a few precipitation of CaCO³ and Fe-CO3. In the early time, serious water sensitivity happened caused by fresh water injection. Rigid granules like CaCO3 and FeCO3, the precipitation of mixed fresh and produced water for reservoir flooding, intensified the obstruction level of formation in wellbore area nearby, the flocculating-deposition of produced polymer and other products blocked the deep area of formation, which were the main reasons for the poor waterflood effect and less effective acidification. [ABSTRACT FROM AUTHOR]