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Since the discovery of piezoelectricity in poly(vinylidene fluoride) (PVDF) 50 years ago, ferroelectric polymers have established their own areas for research and applications due to their unique properties in comparison to single crystals and inorganics. PVDF is a semicrystalline polymer that can crystallize into five different polymorphs. Among them, the polar β-phase is the most interesting one for electroactive properties because it has the highest dipolar moment and the highest piezoelectric response. In the early days, the β-PVDF was typically produced by melt processing, limiting its form to free-standing films. The rapid development of flexible electronics, however, highly requires β-PVDF fabricated from solutions under mild conditions. The objective of this perspective is to summarize the effective methods to produce β-PVDF from solution, to present the approaches for enhancing the electroactive properties through morphological controls, and to discuss the applications of PVDF-based ferroelectric polymers in flexible electronics. In addition, current challenges that may impede the further development of this field are pointed out. [ABSTRACT FROM AUTHOR]

A self-starting process mean monitoring scheme is needed in applications with short production runs or processes subject to degradation. The major challenge in implementing a self-starting monitoring scheme is that there exists little or no historical in-control data to accurately estimate in-control process parameters. In this paper, we propose a new Bayesian self-starting monitoring scheme to detect on-line whether a process mean has exceeded a pre-determined critical threshold. We assume the process is subject to various types of random drift and random jumps prior to exceeding a critical threshold. In comparison with existing self-starting Bayesian schemes in the literature, our model is more flexible in capturing various types of trends and requires less knowledge of process parameters. In addition, the proposed monitoring scheme is much more computationally efficient, rendering it much more applicable for numerous practical situations where model parameter information is limited and timely detection of a critical event is crucial. Numerical studies based on simulated signals and several real data sets are used to evaluate the performance of the proposed method and compare with existing methods in the literature. The proposed method is shown to be less sensitive to parameter misspecification, more flexible in capturing various trends in the data, and much more computationally efficient. [ABSTRACT FROM AUTHOR]

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]

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]

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]