Internal insulation condition identification for high-voltage capacitor voltage transformers based on possibilistic fuzzy clustering

The internal insulation condition of capacitor voltage transformers (CVTs) is a key influence factor that affects their measurement performance and safe operation. However, the internal insulation would age along with long-time operation and degrade due to environmental factors, and once the insulation degradation grows, serious damage and even explosion may happen in CVTs; hence, it is necessary to monitor the internal insulation condition of CVTs, and the fault type and fault degree need to be identified. In this paper, a data-driven internal insulation condition identification method for CVTs is proposed. Both the amplitude and phase of the output voltage of CVTs are collected, and then, recognition models based on the combination of the output voltages and distribution topology of CVTs in substations are built. A possibilistic fuzzy clustering method is used to monitor the internal insulation condition of CVTs, and different types and different degrees of insulation faults could be identified effectively. Finally, the proposed method is verified in several cases; not only the preset typical faults in the method could be identified effectively but also the faults beyond the preset faults could be diagnosed

Detection and attribution of nitrogen runoff trend in China's croplands

Reliable detection and attribution of changes in nitrogen (N) runoff from croplands are essential for designing efficient, sustainable N management strategies for future. Despite the recognition that excess N runoff poses a risk of aquatic eutrophication, large-scale, spatially detailed N runoff trends and their drivers remain poorly understood in China. Based on data comprising 535 site-years from 100 sites across China's croplands, we developed a data-driven upscaling model and a new simplified attribution approach to detect and attribute N runoff trends during the period of 1990–2012. Our results show that N runoff has increased by 46% for rice paddy fields and 31% for upland areas since 1990. However, we acknowledge that the upscaling model is subject to large uncertainties (20% and 40% as coefficient of variation of N runoff, respectively). At national scale, increased fertilizer application was identified as the most likely driver of the N runoff trend, while decreased irrigation levels offset to some extent the impact of fertilization increases. In southern China, the increasing trend of upland N runoff can be attributed to the growth in N runoff rates. Our results suggested that increased SOM led to the N runoff rate growth for uplands, but led to a decline for rice paddy fields. In combination, these results imply that improving management approaches for both N fertilizer use and irrigation is urgently required for mitigating agricultural N runoff in China

Microstructural study on multilayer [FeTaN/TaN] 5 films

Abstract The microstructure of [FeTaN/TaN

The Effect of Roughness on the Nonlinear Flow in a Single Fracture with Sudden Aperture Change

AbstractAbrupt changes in aperture (sudden expansion and contraction) are commonly seen in naturally occurred or artificial single fractures. The relevant research mainly focuses on the changes in fluid properties caused by the sudden expansion of the aperture in smooth parallel fractures. To investigate the effects of roughness on the nonlinear flow properties in a single rough fracture with abruptly aperture change (SF-AC), the flow characteristics of the fractures under different Reynolds numbers Re (50~2000) are simulated by the turbulence k-ε steady-state modulus with the Naiver-Stokes equation. The results show that, in a rough SF-AC, the growth of the eddy and the flow path deflection of the mainstream zone are more obvious than those in a smooth SF-AC, and the discrepancies between the rough and smooth SF-ACs become even more obvious when the relative roughness and/or Re values become greater. The increase of the fracture roughness leads to the generation of more local eddies on the rough SF-ACs and enhances the flow path deflection in the sudden expansion fracture. The number of eddies increases with Re, and the size of eddy area increases linearly with Re at first. When Re reaches a value of 300-500, the growth rate of the eddy size slows down and then stabilizes. Groundwater flow in a rough SF-AC follows a clearly visible nonlinear (or non-Darcy) flow law other than the linear Darcy’s law. The Forchheimer equation fits the hydraulic gradient-velocity (J-v) better than the linear Darcy’s law. The corresponding critical Re value at which the nonlinear flow starts to dominate in a rough SF-AC is around 300~500

Pore structure characterization of Chang-7 tight sandstone using MICP combined with N2GA techniques and its geological control factors

Understanding the pore networks of unconventional tight reservoirs such as tight sandstones and shales is crucial for extracting oil/gas from such reservoirs. Mercury injection capillary pressure (MICP) and N(2) gas adsorption (N(2)GA) are performed to evaluate pore structure of Chang-7 tight sandstone. Thin section observation, scanning electron microscope, grain size analysis, mineral composition analysis, and porosity measurement are applied to investigate geological control factors of pore structure. Grain size is positively correlated with detrital mineral content and grain size standard deviation while negatively related to clay content. Detrital mineral content and grain size are positively correlated with porosity, pore throat radius and withdrawal efficiency and negatively related to capillary pressure and pore-to-throat size ratio; while interstitial material is negatively correlated with above mentioned factors. Well sorted sediments with high debris usually possess strong compaction resistance to preserve original pores. Although many inter-crystalline pores are produced in clay minerals, this type of pores is not the most important contributor to porosity. Besides this, pore shape determined by N(2)GA hysteresis loop is consistent with SEM observation on clay inter-crystalline pores while BJH pore volume is positively related with clay content, suggesting N(2)GA is suitable for describing clay inter-crystalline pores in tight sandstones

Is occupation a good predictor of self-rated health in China?

China's rapidly changing economic landscape has led to widening social inequalities. Occupational status in terms of occupational type and prestige may reflect these socio-structural shifts of social position and be more predictive of self-rated health status than income and education, which may only reflect more gradual acquisitions of social status over time. The goals of this study were to understand the role of occupational status in predicting self-rated health, which is well known to be associated with long-term mortality, as well as compare the occupational status to the other major socioeconomic indicators of income and education.Data from the 2010 baseline surveys of the China Family Panel Studies, which utilized multi-stage probability sampling with implicit stratification was used. Logistic regression was used to examine the relationship of various socioeconomic indicators (i.e. occupational status, income, and education) with self-rated health as the primary outcome of interest. A series of models considered the associations of occupational category or occupational prestige with self-rated health.The final sample consisted of 14,367 employed adults aged 18-60, which was nationally representative of working adults in China. We found that occupation was not a major predictor of self-rated health in China when age, ethnicity, location, marital status, physical and mental health status were controlled for, with the exception of women working in lower grade management and professional jobs (OR = 1.82, 95% CI: 1.03-3.22). In comparison, income followed by education exhibited greater association with self-rated health. The highest income group had the least probability to report poor health (In men: OR = 0.30, 95% CI: 0.21-0.43. In women: OR = 0.44, 95% CI: 0.26-0.73). People educated with junior high school had better self-rated health than those with primary and below education level (In men: OR = 0.62, 95% CI: 0.50-0.75. In women: OR = 0.53, 95% CI: 0.42-0.68). Income, education and occupation were correlated with each other.Within the context of rapid societal changes in China, income and its implications for greater healthcare access and benefits had the greatest association with self-rated health followed by education. Occupational status was not associated. Occupational categories and prestige should be better adapted to reflect China's unique sociopolitical and historical context

Universal Relationship between Mass Flux and Properties of Layered Heterogeneity on the Contaminant-Flushing Process

To remove contaminants from a layered heterogeneous porous system where the flow direction is parallel to the horizontal layering, the flushing front may advance faster in one layer than the other, resulting in a significant vertical concentration gradient across the layer interface. This gradient leads to mass exchange between the layers due to the vertical dispersive transport. Such a mass exchange phenomenon can greatly alter the mass (and heat if the temperature is a concern) distribution in a multi-layer porous media system but has never been investigated before in a quantitative manner. In this study, high-resolution finite-element numerical models have been employed to investigate how transport properties affect contaminant transport during flushing, using a two-layer system as an example. The results showed that the porosity and retardation factor play similar roles in affecting mass flux across the interface. Increasing the porosity (or retardation factor) of one layer with a faster flushing velocity would decrease the total mass flux across the interface of the layers, while increasing the porosity (or retardation factor) of the layer with a slower flushing velocity played an adverse influence. Furthermore, increasing the transverse dispersivity of any layer increased the mass flux across the interface of the two layers. However, changes in the transverse dispersivity did not affect the spatial range (or gap along the flow direction) in which significant vertical mass flux occurs. This study has important implications for managing contaminant remediation in layered aquifers