Modeling of the Partial Discharge Process in a Liquid Dielectric: Effect of Applied Voltage, Gap Distance, and Electrode Type

The partial discharge (PD) process in liquid dielectrics is influenced by several factors. Although the PD current contains the information representing the discharge process during the PD event, it is difficult to determine the detailed dynamics of what is happening in the bulk of the liquid. In this paper, a microscopic model describing the dynamics of the charge carriers is implemented. The model consists of drift-diffusion equations of electrons, positive and negative ions coupled with Poisson’s equation. The stochastic feature of PD events is included in the equation. First the model is validated through comparison between the calculated PD current and experimental data. Then experiments are conducted to study the effects of the amplitude of the applied voltage, gap distance and electrode type on the PD process. The PD currents under each condition are recorded. Simulations based on the model have been conducted to analyze the dynamics of the PD events under each condition, and thus explain the mechanism of how these factors influence the PD events. The space charge generated in the PD process is revealed as the main reason affecting the microscopic process of the PD events

Research on Comparison of the Maximum Dynamic Shear Modulus Test

AbstractDynamic soil modulus and damping ratio are the two basic parameters to describe dynamic deformation characteristics of the soil. There are three ways to obtain soil dynamics parameters i.e. field test, laboratory test, and calculating empirical. Silt loam samples were collected from Dongying area in this study. In order to get the maximum dynamic shear modulus, the following methods were adopted. The shear wave velocity was tested in field using single-hole method, and the maximum dynamic shear modulus capacity was obtained based on the calculation result of the shear wave velocity. The paper compared the results obtained by three methods and got some useful conclusions. The maximum dynamic shear modulus value calculated by field test was close to the corresponding value from the laboratory dynamic triaxial test, while the value obtained from the empirical formula was significantly lower. However, as the theory, method and collation of data for two kinds of tests were different, their test results were not exactly the same

A Smart Online Over-Voltage Monitoring and Identification System

This paper proposes a complete and effective smart over-voltage monitoring and identification system. In recent years, smart grids are of the greatest interest in power system research. One of the main features of smart grid is their self-healing, which can continuously carry out online self-evaluation, discover existing faults, and correct them immediately. The over-voltage smart monitoring-identification-suppression systems play a key role in the construction of self-healing grids. In this paper, eight kinds of common over-voltage are discussed and analyzed. The S-transform algorithm is used to extract features of over-voltage. Aiming at the main features of each kind of over-voltage, six different characteristic quantities are proposed. A well designed fuzzy expert system and a support vector machine are employed as the classifiers to build a two-step identification model. The accuracy of the identification system is verified by field records. Results show that this system is feasible and promising for real applications.National Basic Research Program of China (973 Program) (2009CB724504)National 111 Project of China (B08036

Y27, a novel derivative of 4-hydroxyquinoline-3-formamide, prevents the development of murine systemic lupus erythematosus-like diseases in MRL/lpr autoimmune mice and BDF1 hybrid mice

INTRODUCTION: Naturally occurring CD4(+)CD25(+ )regulatory T (Treg) cells are central to the maintenance of peripheral tolerance. Impaired activity and/or a lower frequency of these cells lead to systemic lupus erythematosus (SLE). Manipulating the number or activity of Treg cells is to be a promising strategy in treating it and other autoimmune diseases. We have examined the effects of Y27, a novel derivative of 4-hydroxyquinoline-3-formamide, on SLE-like symptoms in MRL/lpr autoimmune mice and BDF1 hybrid mice. Whether the beneficial effect of Y27 involves modulation of CD4(+)CD25(+ )Treg cells has also been investigated. METHODS: Female MRL/lpr mice that spontaneously develop lupus were treated orally by gavage with Y27 for 10 weeks, starting at 10 weeks of age. BDF1 mice developed a chronic graft-versus-host disease (GVHD) by two weekly intravenous injections of parental female DBA/2 splenic lymphocytes, characterized by immunocomplex-mediated glomerulonephritis resembling SLE. Y27 was administered to chronic GVHD mice for 12 weeks. Nephritic symptoms were monitored and the percentage of CD4(+)CD25(+)FoxP3(+ )Treg peripheral blood leukocyte was detected with mouse regulatory T cell staining kit by flowcytometry. Purified CD4(+)CD25(+ )Tregs were assessed for immune suppressive activity using the mixed lymphocyte reaction. RESULTS: The life-span of MRL/lpr mice treated with Y27 for 10 weeks was significantly prolonged, proteinuria and renal lesion severity were ameliorated, and blood urea nitrogen, triglyceride and serum anti-double-stranded DNA antibodies were decreased. Similar results were found in chronic GVHD mice. Administration of Y27 had little impact on percentage of the peripheral blood lymphocyte CD4(+)CD25(+)Foxp3(+ )Treg cells in both groups of mice. In contrast, the suppressive capacity of CD4(+)CD25(+ )Treg cells in splenocytes was markedly augmented in Y27-treated mice ex vivo. CONCLUSIONS: Experimental evidence of the protect effects of Y27 against autoimmune nephritis has been shown. The mechanism may involve enhancement of the suppressive capacity of CD4(+)CD25(+ )Treg cells

A 33-year NPP monitoring study in southwest China by the fusion of multi-source remote sensing and station data

Knowledge of regional net primary productivity (NPP) is important for the systematic understanding of the global carbon cycle. In this study, multi-source data were employed to conduct a 33-year regional NPP study in southwest China, at a 1-km scale. A multi-sensor fusion framework was applied to obtain a new normalized difference vegetation index (NDVI) time series from 1982 to 2014, combining the respective advantages of the different remote sensing datasets. As another key parameter for NPP modeling, the total solar radiation was calculated by the improved Yang hybrid model (YHM), using meteorological station data. The verification described in this paper proved the feasibility of all the applied data processes, and a greatly improved accuracy was obtained for the NPP calculated with the final processed NDVI. The spatio-temporal analysis results indicated that 68.07% of the study area showed an increasing NPP trend over the past three decades. Significant heterogeneity was found in the correlation between NPP and precipitation at a monthly scale, specifically, the negative correlation in the growing season and the positive correlation in the dry season. The lagged positive correlation in the growing season and no lag in the dry season indicated the important impact of precipitation on NPP.Comment: 20 pages, 11 figure

Autophagy is involved in oligodendroglial precursor-mediated clearance of amyloid peptide

BACKGROUND: Accumulation of β-amyloid peptides is an important hallmark of Alzheimer\u27s disease (AD). Tremendous efforts have been directed to elucidate the mechanisms of β-amyloid peptides degradation and develop strategies to remove β-amyloid accumulation. In this study, we demonstrated that a subpopulation of oligodendroglial precursor cells, also called NG2 cells, were a new cell type that can clear β-amyloid peptides in the AD transgene mice and in NG2 cell line. RESULTS: NG2 cells were recruited and clustered around the amyloid plaque in the APPswe/PS1dE9 mice, which is Alzheimer\u27s disease mouse model. In vitro, NG2 cell line and primary NG2 cells engulfed β-amyloid peptides through the mechanisms of endocytosis in a time dependent manner. Endocytosis is divided into pinocytosis and phagocytosis. Aβ(42) internalization by NG2 cells was mediated by actin-dependent macropinocytosis. The presence of β-amyloid peptides stimulated the autophagic pathway in NG2 cells. Once inside the cells, the β-amyloid peptides in NG2 cells were transported to lysosomes and degraded by autophagy. CONCLUSIONS: Our findings suggest that NG2 cells are a new cell type that can clear β-amyloid peptides through endocytosis and autophagy

Electrical Circuit Flashover Model of Polluted Insulators under AC Voltage Based on the Arc Root Voltage Gradient Criterion

In order to study the flashover mechanism of polluted insulators under AC voltage, a new arc propagation criterion which is based on an arc root voltage gradient is proposed. This criterion can explain the variation of the arc root voltage gradient in the arc propagation process. Based on this criterion, a new distributed parameter electrical circuit flashover model of polluted insulators is presented. The arc channel is considered as an equivalent distributed parameter circuit model instead of using the arc voltage-gradient equation. The parameters of the arc model are obtained from the electromagnetic field distribution of the arc and the gas discharge theories. The arc root is considered as parallel paths including the polluted layer. The variation of the voltage on the arc root is related to the capability of arc propagation. This model takes the microscopic mechanism of arc root ionization into consideration, which can improve the accuracy of the flashover model. The results obtained from the presented model are in good agreement with other mathematical and experimental results.National Basic Research Program of China (973 Program) (2009CB724507)National 111 Project of China (B08036

Copper metabolism and hepatocellular carcinoma: current insights

Copper is an essential trace element that acts as a cofactor in various enzyme active sites in the human body. It participates in numerous life activities, including lipid metabolism, energy metabolism, and neurotransmitter synthesis. The proposal of “Cuproptosis” has made copper metabolism-related pathways a research hotspot in the field of tumor therapy, which has attracted great attention. This review discusses the biological processes of copper uptake, transport, and storage in human cells. It highlights the mechanisms by which copper metabolism affects hepatocellular carcinogenesis and metastasis, including autophagy, apoptosis, vascular invasion, cuproptosis, and ferroptosis. Additionally, it summarizes the current clinical applications of copper metabolism-related drugs in antitumor therapy

Characterization on microstructure of interface and failure analysis of SiC fiber reinforced Ti-17 composites under tension load

From IOP Publishing via Jisc Publications RouterHistory: ppub 2021-05, open-access 2021-05-01Publication status: PublishedAbstract: In this study, the ultimate tensile strength of unidirectional SiC-fiber/Ti-17 composites was measured in the as-produced condition at room temperature. Fracture and interfacial reaction zone was characterized by using laser confocal microscopy, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy. Elemental distribution maps of the interfacial reaction layer and titanium matrix were quantitatively examined by electron probe micro-analyzer (EPMA). Micromechanical properties of SiC fiber and titanium matrix was inspected by Nano-indentation. The Fracture failure mechanisms was show that the key microstructural parameters which dominate damage initiation, damage growth and fracture behavior of the composites were explained in detail

Anthropogenic influence on 2018 summer persistent heavy and daily extreme rainfall in central western China

Anthropogenic forcing has reduced the probability of summer persistent heavy rainfall in central western China similar to 2018 by ~47%, but increased that of daily extremes by ~1.5 times, based on HadGEM3-GA6 ensembles