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

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

The mob as tumor suppressor (mats1) gene is required for growth control in developing zebrafish embryos

The mob as tumor suppressor (mats) family genes are highly conserved in evolution. The Drosophila mats gene functions in the Hippo signaling pathway to control tissue growth by regulating cell proliferation and apoptosis. However, nothing is known about whether matsfamily genes are required for the normal development of vertebrates. Here we report that zebrafish has three mats family genes. Expression of mats1 is maternally activated and continues during embryogenesis. Through a morpholino-based knockdown approach, we found that mats1 is required for normal embryonic development. Reduction of mats 1 function caused developmental delay, a phenotype similar to that of Drosophila mats homozygous mutants. Both cell proliferation and apoptosis were defective in mats1 morphant embryos. Moreover, mats1 morphant cells exhibited a growth advantage in chimeric embryos, similar to mats mutant cells in mosaic tissues in Drosophila. Therefore mats1 plays a critical role in regulating cell proliferation and apoptosis during early development in zebrafish, and the role of matsfamily genes in growth regulation is conserved in both invertebrates and vertebrates. This work shows that zebrafish can be a good model organism for further analysis of Hippo signaling pathway.Developmental BiologySCI(E)PubMed2ARTICLE4525-5335

The Role of Tumour Metabolism in Cisplatin Resistance

Cisplatin is a chemotherapy drug commonly used in cancer treatment. Tumour cells are more sensitive to cisplatin than normal cells. Cisplatin exerts an antitumour effect by interfering with DNA replication and transcription processes. However, the drug-resistance properties of tumour cells often cause loss of cisplatin efficacy and failure of chemotherapy, leading to tumour progression. Owing to the large amounts of energy and compounds required by tumour cells, metabolic reprogramming plays an important part in the occurrence and development of tumours. The interplay between DNA damage repair and metabolism also has an effect on cisplatin resistance; the molecular changes to glucose metabolism, amino acid metabolism, lipid metabolism, and other metabolic pathways affect the cisplatin resistance of tumour cells. Here, we review the mechanism of action of cisplatin, the mechanism of resistance to cisplatin, the role of metabolic remodelling in tumorigenesis and development, and the effects of common metabolic pathways on cisplatin resistance

Research on Thermosensitive Coatings for Thermal Runaway Warning in Energy Storage Power Station

[Introduction] Lithium iron phosphate battery storage power plants are an important basis for new power systems to consume large-scale new energy, however, the thermal runaway of battery cells seriously threatens the operational safety of storage power plants. It is important to conduct real-time monitoring and scientific warning of local overheating in storage power plants. [Method] In this work, a thermal microcapsule with the ability to sense overheating temperature and produce colour changes was prepared and added in appropriate amounts to an epoxy resin matrix to form a composite insulating material with the characteristics of sensing external overheating temperature fields. [Result] Test results show that the colour of the prepared thermosensitive microcapsule/epoxy insulating temperature indication coating can change sensitively with external temperature changes, with a sudden colour change occurring at around 60 °C. When the doping mass fraction of the thermosensitive microcapsules is 0.25%, the insulation strength and dielectric properties of the composite coating are comparable to those of the pure epoxy resin material, maintaining good intrinsic electrical properties. [Conclusion] The thermosensitive colour-changing composite insulation coating proposed in the study can visibly change the temperature of the external local overheating state, providing a new technical route for the application of thermal runaway warning in energy storage power plants, which has certain engineering application value

Different effect of quenching temperature on Fe1+σTe0.5Se0.5 and β-FeSe

In this work, we have demonstrated a different effect on Fe1+σTe0.5Se0.5 and β-FeSe by changing the quenching temperature. Tc is clearly reduced in Fe1+σTe0.5Se0.5 after increasing the quenching temperature from 300 °C to 500 °C, while that of β-FeSe is almost unchanged. Structure refinement indicates that after quenched at 500 °C, FeTe4 tetrahedron exhibits an expansion with the stretched Fe-Te bond, together with the increased amount of interstitial iron. These particular changes on structure are believed to be responsible for the suppression of superconductivity in Fe1+σTe0.5Se0.5

A Defect Detection Method Based on BC-YOLO for Transmission Line Components in UAV Remote Sensing Images

Vibration dampers and insulators are important components of transmission lines, and it is therefore important for the normal operation of transmission lines to detect defects in these components in a timely manner. In this paper, we provide an automatic detection method for component defects through patrolling inspection by an unmanned aerial vehicle (UAV). We constructed a dataset of vibration dampers and insulators (DVDI) on transmission lines in images obtained by the UAV. It is difficult to detect defects in vibration dampers and insulators from UAV images, as these components and their defective parts are very small parts of the images, and the components vary greatly in terms of their shape and color and are easily confused with the background. In view of this, we use the end-to-end coordinate attention and bidirectional feature pyramid network “you only look once” (BC-YOLO) to detect component defects. To make the network focus on the features of vibration dampers and insulators rather than the complex backgrounds, we added the coordinate attention (CA) module to YOLOv5. CA encodes each channel separately along the vertical and horizontal directions, which allows the attention module to simultaneously capture remote spatial interactions with precise location information and helps the network locate targets of interest more accurately. In the multiscale feature fusion stage, different input features have different resolutions, and their contributions to the fused output features are usually unequal. However, PANet treats each input feature equally and simply sums them up without distinction. In this paper, we replace the original PANet feature fusion framework in YOLOv5 with a bidirectional feature pyramid network (BiFPN). BiFPN introduces learnable weights to learn the importance of different features, which can make the network focus more on the feature mapping that contributes more to the output features. To verify the effectiveness of our method, we conducted a test in DVDI, and its [email protected] reached 89.1%, a value 2.7% higher than for YOLOv5

Optimization and Experimental Study of the Semi-Closed Short-Gap Arc-Extinguishing Chamber Based on a Magnetohydrodynamics Model

The multi-chamber arc-extinguishing structure (MAS), which consists of a lot of semi-closed short-gap arc-extinguishing chambers (SSAC) in series, can be used in parallel gap lightning protection devices to improve the ability to extinguish power frequency follow current. The arc-extinguishing ability of single SSAC directly affects the arc-extinguishing performance of the whole MAS. Therefore, the arc-extinguishing performance of MAS can be improved by optimizing single SSACs. A two-dimensional model of the arc plasma in a SSAC is built based on the magneto-hydrodynamic (MHD) theory. The motion characteristics of an arc in the SSAC are simulated and analyzed. An optimization method of the SSAC structure is proposed. Finally, an impact test platform is built to verify the effectiveness of the optimized SSAC structure. Results show that the short-gap arc forms a high-speed airflow in the SSAC and the arc plasma sprays rapidly to the outlet until the arc is extinguished at its current zero-crossing point. The amplitude of airflow velocity in the optimized structure can be increased to about 8-fold the velocity in the basic structure. Experiments also show that the dissipation time of an arc in the optimized SSAC is 79.2 μs, which is much less than that in the original structure (422.4 μs)

Mixed Over-Voltage Decomposition Using Atomic Decompositions Based on a Damped Sinusoids Atom Dictionary

The main purpose of this paper is to establish a signal decomposition system aiming at mixed over-voltages in power systems. In an electric power system, over-voltage presents a great threat for the system safety. Analysis and identification of over-voltages is helpful to improve the stability and safety of power systems. Through statistical analysis of a collection of field over-voltage records, it was found that a kind of complicated signals created by mixing of multiple different over-voltages is difficult to identify correctly with current classification algorithms. In order to improve the classification and identification accuracy of over-voltages, a mixed over-voltage decomposition system based on the atomic decomposition and a damped sinusoid atom dictionary has been established. This decomposition system is optimized by using particle swarm optimization and the fast Fourier transform. Aiming at possible fault decomposition results during decomposition of the over-voltage signal, a double-atom decomposition algorithm is proposed in this paper. By taking three typical mixed over-voltages as examples, the validity of the algorithm is demonstrated