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The accumulation of insulator surface contamination is closely related to the distribution of flow field around the insulator. In order to study the unevenness of the insulator surface contamination, a three-unit lxy-160 insulator is selected. Based on the principle of fluid mechanics, the fluid movement state on the insulator surface is determined by the calculation of Reynolds number and boundary layer, then the flow field distribution around the insulator is obtained. On this basis, the artificial contamination test and numerical simulation are carried out to study the characteristics of contamination uneven distribution on the insulator surface. The results show that when the wind speed is 3–7 m/s and the particle diameter is 1–60 µm, there is obvious boundary layer separation phenomenon, and the flow state before the separation point is laminar, while the flow state behind the separation point is turbulent. From top to bottom, the degree of accumulation on each insulator is different, and the contamination on the windward and leeward sides are unevenly distributed in a fan shape. The increment of wind speed as well as particle diameter will aggravate the unevenness of the contamination.

The fault model of the inter-turn short circuit of the dry air-core reactor is first analysed in this study, by which an online monitoring method of the reactor inter-turn insulation fault is proposed by using the change of the power angle. In order to achieve high-precision measurement, the fundamental harmonic separation algorithm improved by Hanning windowed interpolation method can effectively reduce the error of power angle measurement caused by frequency fluctuation and harmonic interference. By comparing it with the power angle measurement errors of fast Fourier transform (FFT) and Hanning window interpolation FFT, the algorithm is verified. The sensitivity and stability of the equipment are verified by the experiment of simulating and eliminating the fault in the initial stage of the inter-turn short circuit. At the same time, an online monitoring system for inter-turn insulation fault of dry-type air-core reactor based on this method is designed, including field monitoring device, the intelligent electronic device of the dry air-core reactor and expert software. The method and monitoring device proposed in this study enables the fault to be accurately monitored in the early stage, which is of great significance for the safe operation of the reactor.

The conductor-loosened fault of the transmission line caused by its own mechanical load, breeze vibration, and galloping will gradually worsen by the passage of time and even lead to a series of irreversible accidents such as conductor breakage and tower fall. In order to detect the loosened conductors as soon as possible and minimize the possible damages, a detection method for the loosened conductor based on the vision sensor is proposed. First, the conductor images are captured by the image acquisition system, using the inspection robot, and then, the energy gradient algorithm with guided filtering (GEG) is performed to highlight the foreground and strengthen the hierarchy, so that the conductor area can be obtained by the Otsu threshold segmentation. Second, the surface contour of the conductor is extracted, filtered, and numbered. Finally, according to the arrangement characteristics of the outermost Al-strands of the conductor, we established a conductor-loosened model that includes the analysis of the four feature quantities of contour length $D$ , direction angle $\theta $ , curvature $W$ , and spacing $T$ and the thinning process based on the step-vertical limit (SVL) to judge the conductor fault and locate the loosened strands. We analyze the performance of the technology by tests, and the results demonstrate that the proposed method can quickly detect the conductor-loosened fault and achieve good performance.

Icicles generated on the insulator sheds will constantly shorten the insulating gap distance between adjacent sheds as growth, thereby inducing significant decrease in electrical insulation of the insulators, icicle bridging even threatening the operating security of power systems. In order to evaluate whether the ice-covered insulator needs to deicing or the icicles bring in potential dangers, a study on detection and condition assessment of icicle bridging for ice-covered suspension glass insulator by image analysis is proposed in this article. First, the initial icicles regions are obtained by the local variation threshold segmentation algorithm based on the optimized texture energy image. Second, the insulator sheds are segmented and extracted based on the normalized color difference operator, and then the complete icicles regions are obtained through the image difference and postprocessing. Finally, the icicle length is calculated by finding its smallest axis-parallel enclosing rectangle, and two adjacent insulator sheds spacing which is calculated by ellipse fitting is used as bridging threshold, so the condition of icicle bridging can be defined as the safe, observation, and danger. The results demonstrate that the icicles can be effectively enhanced and accurately segmented by the presented method in this article, and the icicle bridging condition of ice-covered insulator can be assessed with average detection accuracy of 92.2% and average time consumption of 3.910 s, by which the safe operation of ice-covered insulator can be monitored and guaranteed.

As one of the important antivibration fittings in transmission lines, the damper’s accurate location, the quick detection of damper rust defect, and the timely remedial measures are all of great significance to ensure the reliable transmission of electric energy. Considering the background complexity of the damper image and harmfulness of its rust defect, a method for identifying the rust status of damper based on image processing is proposed in this article. First, the damper image acquired by the image acquisition device is grayed, and the feature enhancement of the damper region is completed by the local difference processing, the edge strength mapping based on the anisotropic Gaussian kernel directional derivative and the image fusion, and so on. Second, the segmentation of damper is completed by the threshold segmentation and the morphological treatment. Finally, the rust parameters of the damper area, which are the rusty area ratio (RAR) and the color shade index (CSI) are presented, by which the identification of the rust status can be defined as the rust-free, slight rust, medium rust, and severe rust. The results show that the segmentation and accurate identification of the rusted dampers can be completed by the proposed method. The total identification rate of the rusted dampers can reach 93% even under the complex background. The method is new and effective for identifying the rust status of damper.

CRISPR-Cas9 has become a versatile tool for genome editing and regulation, and strategies to effectively control its activity have attracted much attention. RNAi, also a gene-regulating tool, is used as another mechanism by which eukaryotes resist the invasion of foreign genetic material. Methods: In this study, we analyzed the quantitative inhibition of the CRISPR system by using artificial miRNAs (amiRNAs) combined with the RNAi enhancer enoxacin to improve the targeting specificity of the CRISPR system. Furthermore, we examined the feasibility of improving the efficiency of gene editing and regulation by blocking the effects of natural intracellular miRNAs on sgRNAs. Results: amiRNAs targeting the sgRNA were used to control its expression, and the small molecule drug denoxacin was utilized to enhance this effect, especially in the presence of Cas9. amiRNA/enoxacin inhibited CRISPR-mediated gene editing and regulation both in vitro and in vivo and could tune sgRNA-targeting specificity. Furthermore, CRISPR efficiency was increased by blocking the effects of endogenous miRNAs. Conclusion: Our study provides an efficient molecular switch for conditional regulation of CRISPR activities in mammalian cells and also presents potentially useful approaches for solving current key issues of off-target effects and low targeting efficiency.

Background: Bladder cancer (BC) is one of the most common malignancies world-wide with high morbidity and mortality. Long noncoding RNAs (lncRNAs) are thought to play a critical role in cancer development. LncRNA NRON, a repressor of activated T-cell nuclear factor (NFAT), has been shown to be dysregulated in many cancer types. However, the clinical significance and molecular mechanism of NRON in bladder cancer is still unknown. Methods: The expression levels of NRON in BC tissues and cell lines were tested by RT-qPCR. Survival analysis was performed to detect the correlation between NRON expression and clinical outcomes in patients with BC. The biological role of NRON in BC cells proliferation and metastasis was examined in vitro and in vivo. Results: The expression of NRON was significantly upregulated in BC specimens and cell lines compared with paired adjacent normal tissues and normal cell lines. The upregulation of NRON in bladder cancer patients was significantly associated with the depth of bladder tumor invasion and poor prognosis. Knockdown of NRON inhibited BC cells proliferation, migration, invasion and tumorigenicity. Furthermore, NRON promoted epithelial-mesenchymal transition (EMT) progression, and NRON-induced EZH2 expression contributed to this process. Conclusion: In conclusion, our results suggested that NRON acted as an oncogene and tumor biomarker for BC.

N6-methyladenosine (m6A) RNA modification is the most common internal mRNA modification in mammals and has been reported to play a key role in gene expression regulation. In this study, we detected a high level of m6A methylation of the PLOD2 3′-untranslated regions (3′UTR) in renal cell carcinoma (RCC). Furthermore, we found that the high expression level of PLOD2 was a prognostic indicator for patients with RCC. A dm6ACRISPR demethylation system was performed to accurately and specifically demethylate 3′UTR of PLOD2 and caused an inactivation of PLOD2 expression. Furthermore, we also performed many in vitro experiments to confirm that PLOD2 exerted tumor promoter effects by promoting tumor proliferation and migration. In conclusion, PLOD2 mRNA demethylated by dCas13b-ALKBH5 might provide a new light on the treatment for RCC.

The vibration between the spacers of bundle conductors may cause the conductors to collide with each other, thereby damaging the conductors and the spacers, even resulting in adhesion. The main function of the spacers is to limit the relative movement between the bundle conductors, but it still exists. In order to find out the potential dangers caused by the movement and prevent adhesion among four or multibundle conductors, a measurement method of space distance among bundle conductors is presented in this paper. First, the images of bundle conductors are obtained by installing cameras on the optimum position of tower, which are segmented by the maximum interclass variance method after preprocess, and the axis of conductors can be obtained by the skeleton extraction. Second, the image coordinates of each point on the axis are transformed into the world coordinates by camera calibration, and these points are fit by least-squares method to get the conductor function. Then, the actual transmission conductor model can be reconstructed according to the fitting function, conductor diameter, and spacers. Finally, calculating the distance between two bundle conductors, the minimum distance can be obtained. We analyze the performance of the technology by a series of experiments ; the results demonstrate that the proposed method can measure the space distance with an average relative error of 2%–4%. The running status of the bundle conductors can be monitored based on the presented method in this paper, by which the safe operation of transmission lines can be guaranteed.

Icicle will cause serious distortion of insulator electric field, weaken its voltage strength, and easily cause insulator flashover. Previous studies have shown that the longer the length of icicles on insulator, the greater the possibility of electric flashover. Then, it is of great theoretical significance and practical value to study the image identification technology of icicle length of iced insulators. Firstly, the growth mechanism and structural characteristics of insulator icicles are discussed in this paper, and the image acquisition method of iced insulator is discussed. Secondly, the methods of saliency detection and color feature analysis are used to extract the region of icicle and insulator sheds respectively, then, the icicle structure on insulator is obtained by the difference calculation of above two images. Meanwhile, the pixel curve of the iced insulator image is processed by Fourier transform, and the reference size of insulators icicle is obtained by calculating the length of the shed spacing. Finally, a practical case about iced insulators in substations is analyzed in detail, which proves the effectiveness of the method proposed in this paper.

The thermal de-icing by Joule effect is a mostly valid way to prevent transmission-lines from the severe ice storm. A model was put forward to simulate the critical ice-melting current on iced conductor. Based on this model, the value of critical ice-melting current was calculated with various parameters, some of which were ignored in the earlier literatures, such as ice-layer heat conductivity, wind attack angle, and icing section shape. The results of the experiment and simulation show that the critical ice-melting current increase with wind speed, wind attack angle, and ice-layer heat conductivity, but decrease rapidly with ambient temperature and liquid water content. Moreover, the maximum difference between the results of simulation and experiment is about 9%, thus this model can be employed to estimate the engineering parameters in practical thermal de-icing projects.

Hydrophobicity of the composite insulators is a parameter which is closely related to the insulation properties. In order to determine whether the insulator in the transmission line needs to be withdrawn, it is necessary to objectively and accurately determine the hydrophobicity grade of the composite insulator. The study on hydrophobicity detection of composite insulators of transmission lines by image analysis is proposed in this paper, by which the hydrophobicity of composite insulators can be measured timely. The grayscale, median filtering, and histogram equalization of the hydrophobic images are fulfilled sequentially, and the water drops (or water marks) region is segmented by binary large object analysis and four parameters related to water repellency are extracted. In addition, the improved support vector machine algorithm is adopted to calculate the hydrophobicity of composite insulators. The results show that seven typical hydrophobic levels of insulators can be recognized by the proposed hydrophobicity detection method whose accuracy is more than 91%.

Rationale: The p53 gene is a well-known tumor suppressor, and its mutation often contributes to the occurrence and development of tumors. Due to the diversity and complexity of p53 mutations, there is still no effective p53 gene therapy. In this study, we designed and constructed an aptazyme switch that could effectively sense cellular wild-type p53 protein and regulate downstream gene function flexibly. The application of this artificial device in combination with Cre-LoxP and dCas9-VP64 tools achieved a precisely targeted killing effect on tumor cells. Methods: The affinity of the aptamer to p53 protein was verified by SPR. p53 aptazyme and gene circuits were chemically synthesized. The function of the gene circuit was detected by cell proliferation assay, apoptosis assay and Western blot. The nude mouse transplantation tumor experiment was used to evaluate the inhibitory effect of gene circuits on tumor cells in vivo. Results: The results of the SPR experiment showed that the p53 aptamer RNA sequence had a robust binding effect with p53 protein. The p53 aptazyme could efficiently sense wild-type p53 protein and initiate self-cleavage in cells. The Cre-p53 aptazyme gene circuit and dCas9-VP64/sgRNA mediated gene circuit designed based on p53 aptazyme significantly inhibited the growth and promoted the apoptosis of wild-type p53-deficient cancer cells in vitro. In addition, the gene circuits also had a significant inhibitory effect on tumors in vivo. Conclusion: The study developed a novel and efficient ribozyme switch for p53-specific recognition and provided a modular strategy for aptazyme binding to cellular proteins. In addition, the p53 aptazyme successfully inhibited tumor growth through a combined application with other synthetic biological tools, providing a new perspective for cancer therapy.

Optogenetic systems have been increasingly investigated in the field of biomedicine. Previous studies had found the inhibitory effect of the light-inducible genetic circuits on cancer cell growth. In our study, we applied an AND logic gates to the light-inducible genetic circuits to inhibit the cancer cells more specifically. The circuit would only be activated in the presence of both the human telomerase reverse transcriptase (hTERT) and the human uroplakin II (hUPII) promoter. The activated logic gate led to the expression of the p53 or E-cadherin protein, which could inhibit the biological function of tumor cells. In addition, we split the dCas9 protein to reduce the size of the synthetic circuit compared to the full-length dCas9. This light-inducible system provides a potential therapeutic strategy for future bladder cancer.

Gas Insulated Switchgear (GIS) is a complete set of switchgear, such as circuit breaker, disconnector, bus bar, which enclosed in a metal shell filled with SF 6 gas grounding. The presence of internal metal particles will cause partial discharge of GIS, leading to insulation breakdown. The main purpose of this paper is to study the particle movement rules of different shapes and sizes based on different types of voltage, so as to determine a kind of fault map. The fault map is used to estimate the shape and size of the metal particles that cause GIS partial discharge. Based on this purpose, the movement of metal particles under the action of high voltage AC, DC and pulse signals are simulated by electric field simulation and mechanical analysis. The results show that there is no regularity in the movement of particles under AC and DC, but there is regularity in the movement of particles under pulse voltage. Different types and sizes of particles have different trajectories. The movement height of particles is directly proportional to the length of particles, the applied voltage and inversely proportional to the half diameter of particles.

To evaluate the aging state of composite insulating materials quickly and accurately, this paper proposes a method based on polarization/depolarization current method. High polymer epoxy is selected as the research object. The UV aging test is performed on epoxy materials, and the polarization/depolarization current method is used to detect the aging state of the materials. Through the analysis of the polarization and depolarization current curve, the initial value, stable value and turning time of polarization and depolarization current are extracted as the characteristics of the aging state of the epoxy material. Comparing the polarization/depolarization current curves and their characteristic values of materials with different aging degrees, it can be found that the initial value, stable value and turning time of polarization and depolarization current are closely related to the aging degree of materials in the polarization and depolarization stages. The results show the more serious the aging of epoxy materials, the greater the polarization and depolarization current. The results show that the polarization / depolarization current method can effectively evaluate the aging characteristics of composite insulator.

In this article, an online monitoring technology applied to transmission line towers is proposed to overcome the problems that the foundation deformation is difficult to find in the mining area, river, hillside, and other special areas. The measurement of the stress or the strain caused by the tower foundation deformation are rarely issued, though the tower status can be possibly assessed by the stress or the strain. A new online monitoring technology of tower foundation deformation of transmission lines is developed which consists of three parts. In the first part, the stress or the strain of the key elements is effectively analyzed under the different deformations such as foundation settlement, inclination, and side-slip with the tower finite element model built and the wind load and ice load applied on the tower. In the second part, the experimental platform of tower stress tests is set up, and the internal relations between the stress variation and the tower foundation deformation are determined. In the third part, the online monitoring technology of tower foundation deformation of transmission lines is developed based on fiber Bragg grating stress sensor and successfully applied in Jibei power grid in China. The results show that all the monitored stresses fluctuating with the wind speed are small in case that the condition of tower foundation is normal; on the contrary, the corresponding stresses will change greatly.

In order to reduce the damages of transmission line icing, an effective ice accretion forecasting can be used to guide the de-icing work. The ice accretion on transmission lines varies slowly over time, and the icing data series is characteristic of timing sequence and autocorrelation. Time-series analysis is suitable for analysing the similar data series, and fireworks algorithm (FA) is used to determine the autoregressive order and the moving average order of time-series analysis. Then a short-term ice accretion forecasting for transmission lines with modified time-series analysis by FA is built. The ice accretion experiments were done in artificial icing laboratory. The results show that the modified time-series analysis model by the FA has higher accuracy than another five models, whose relative errors are

The icing on transmission line conductor usually causes accidents such as conductor galloping, conductor breaking, line tripping, and even network paralyzing, which could bring serious threats to the safe operation of the power system. The conductor icing shape not only has a great influence on the estimate to melting ice time or melting ice current, but also directly affects the mechanical calculation of conductor galloping. Therefore, it is paramount to determine the conductor icing shape. Many available artificial measurements are inaccurate and even ineffective enough in some cases. This paper proposes a novel online technology for measuring icing shape on transmission line conductor based on vision and force sensors. The proposed technique consists of three parts, namely, the online device based on vision and force sensors, the communication network, and the monitoring center. The images of the iced conductor are captured from two cameras, and the processing algorithms are used to extract the average diameters of the iced conductor. The equivalent cross-sectional area is also obtained by the force sensors and a built-in mechanics model. The icing shape description algorithm is proposed to accurately represent the icing shape. We thoroughly analyze the performance of the technology by a series of experiments under artificial icing simulations and natural conditions. The experimental results demonstrate that the proposed method can measure the icing shapes with the overlap ratio of greater than 0.85. In addition, the proposed measuring technology shows satisfactory results on the field tests carried out on operating transmission lines.

The traditional treatment for cancer is lack of specificity and efficacy. Modular synthetic regulatory RNAs, such as inhibitive RNA (iRNA) and active RNA (aRNA), may overcome these limitations. Here, we synthesize a new iRNA to bind the upstream activating sequence (UAS) of a minimal promoter that drives expression of artificial miRNAs (amiRNAs) targeting MYC, which represses the binding interaction between UAS and GAL4 fusion protein (GAL4-VP64) in GAL4/UAS system. The aRNA driven by a tumor-specific mutant human telomerase reverse transcriptase (hTERT) promoter is created to interact with iRNA to expose UAS again in bladder cancer. Without the aRNA, mRNA and protein levels of MYC, cell growth, cell apoptosis and cell migration were no significance in two bladder cancer cell lines, T24 and 5637, and human foreskin fibroblast (HFF) cells. The aRNA significantly inhibited the expression of MYC in mRNA and protein levels, as well as the proliferation and migration of the cancer cells, but not in HFF cells. These results indicated that regulatory RNAs selectively controlled the expression of amiRNAs and ultimately suppress the progression of bladder cancer cells without affecting normal cells. Synthetic regulatory RNAs might be a selective therapeutic approach for bladder cancer.

In double-tensural fully compliant bistable mechanisms (DTBMs), all of the compliant segments are loaded in tension when deflected, thus the problems associated with buckling are avoided. Because the stiffening of the compliant segments due to tensile loads plays an important role in achieving the bistable behaviors, it is critical to capture the relevant geometric nonlinearities when modeling DTBMs. Based on the beam constraint model (BCM) and the chained beam constraint model (CBCM), two kinetostatic models are developed for DTBMs in this work: Model I models both of the tensural segments using BCM, while Model II models the shorter tensural segment using BCM and the longer tensural segment using CBCM with two BCM elements. The two models well predict the bistability and the kinetostatic behaviors of a DTBM as compared to the finite element results. Although Model II is a little more complicated than Model I, it improves the modeling accuracy, especially at the negative stiffness region of the kinetostatic curve.

The high-voltage direct current (HVDC) and HV alternating current (HVAC) hybrid transmission lines in the same corridor is an effective way to enhance the power transmission capacity of the corridor and save land resource. The transmission lines parameters such as the corridor width, the height of transmission lines, and electromagnetic environment can be analysed and optimised by the calculation of the hybrid ion-flow field. In this study, nodal discontinuous Galerkin time-domain method is for the first time applied to the calculation of the hybrid ion-flow field. Furthermore, corona interactions between the HVDC and HVAC lines are considered in the process of numerical solution. Compared with measured results and previous methods, the proposed approach is verified to be able to obtain wiggle-free numerical solution with significantly reducing the computational burden, and meanwhile, the calculation precision is increased greatly. The ground-level electric field and ion current density of the hybrid lines in time domain are analysed, and then the time-domain characteristic is explored. Finally, the ion-flow fields of the hybrid ±800 kV DC/500 kV AC transmission lines in parallel and on the same tower have been made a comparative analysis and optimisation, which provide theoretical basis for real hybrid towers design.

The current therapies for treating tumors are lacking in efficacy and specificity. Synthetic biology principles may bring some new possible methods for curing cancer. Here we present a synthetic logic circuit based on the CRISPR/Cas9 system. The CRISPR/Cas9 technology has been applied in many biological fields, including cancer research. In this study, the expression of Cas9 nuclease was controlled indirectly by an enhanced hTERT promoter using the GAL4/upstream activating sequence (UAS) binding system. Cas9 was driven by 5XUAS, single guide RNA (sgRNA) was used to target mutant or wild-type HRAS, and the fusion gene GAL4-P65 was driven by the enhanced hTERT promoter. The system was tested in bladder cancer cells (T24 and 5637) and the results showed that the enhanced hTERT promoter could drive the expression of GAL4-P65 in these bladder cancer cell lines. Then all these devices were packed into lentivirus and the results of quantitative real-time PCR showed that the mRNA expression level of HRAS was selectively inhibited in the T24 and 5637 cells. The results of functional experiments suggested that the proliferation, cell migration and invasion were selectively suppressed, and that the apoptosis rate was increased in bladder cancer cells but not in human foreskin fibroblasts (HFF). In conclusion, we successfully constructed an enhanced hTERT promoter-driven CRISPR/Cas9 system and data showed that it could selectively suppress the progression of bladder cancer cells.

In this paper, we present a vibration-based transmission tower structural health monitoring system consisting of two parts that identifies structural changes in towers. An accelerometer group realizes vibration response acquisition at different positions and reduces the risk of data loss by data compression technology. A solar cell provides the power supply. An analyser receives the data from the acceleration sensor group and calculates the transmission tower natural frequencies, and the change in the structure is determined based on natural frequencies. Then, the data are sent to the monitoring center. Furthermore, analysis of the vibration signal and the calculation method of natural frequencies are proposed. The response and natural frequencies of vibration at different wind speeds are analysed by time-domain signal, power spectral density (PSD), root mean square (RMS) and short-time Fouier transform (STFT). The natural frequency identification of the overall structure by the stochastic subspace identification (SSI) method reveals that the number of natural frequencies that can be calculated at different wind speeds is different, but the 2nd, 3rd and 4th natural frequencies can be excited. Finally, the system was tested on a 110 kV experimental transmission line. After 18 h of experimentation, the natural frequency of the overall structure of the transmission tower was determined before and after the tower leg was lifted. The results show that before and after the tower leg is lifted, the natural frequencies of each order exhibit obvious changes, and the differences in the average values can be used as the basis for judging the structural changes of the tower.

Circular RNAs (circRNAs), one kind of non-coding RNA, have been reported as critical regulators for modulating gene expression in cancer. In this study, microarray analysis was used to screen circRNA expression profiles of bladder cancer (BC) 5637 cells, T24 cells and normal control SV-HUC-1 cells. The data from the microarray showed that hsa_circ_0075828 (named circCASC15) was most highly expressed in 5637 and T24 cells. circCASC15 was highly expressed in BC tissues and cells. Overexpression of circCASC15 was closely associated with BC tumor stage and promoted cell proliferation significantly in vitro and in vivo. Mechanistically, circCASC15 could act as miR-1224-5p sponge to activate the expression of CREB1 to promote cell proliferation in BC. In short, circCASC15 promotes cell proliferation in BC, which might be a new molecular target for BC diagnosis and therapy. [BMB Reports 2020; 53(2): 82-87].

Insulator flashover caused by atmospheric icing is a serious accident with high frequency, which seriously influences the security of the power system in icing areas. Therefore, it is of great theoretical significance and engineering value to carry out research on risk prediction technology of icing flashover. Firstly, in this paper, the main influencing factors of icing flashover of insulators are analyzed, and the morphological characteristics of iced insulators are deeply studied, such as icing type, icing amount, icicle length and bridging state, insulator pollution, etc. Secondly, the monitoring methods of iced insulator are analyzed and compared, and the results show that the image monitoring technology has obvious advantages in icing flashover prediction. More importantly, the current research progress and technical difficulties of image recognition technology for icing flashover parameters are discussed. Finally, the research prospect of flashover risk prediction model for iced insulator is introduced based on deduction method and machine learning algorithm.

The ion-flow field is a coupled problem, the numerical analysis of which is achieved by iterative solution of Poisson’s equation and current continuity equation. In this study, a highly stable method for solving the ion-flow field is proposed. The solution domain and the boundary are redefined by imposing the absorbing boundary conditions, which ensures the efficiency and stability of iterative method. The Poisson's equation and current continuity equation are solved simultaneously through the new second order iterative method. The Poisson's equation increases the boundary constraints for the electric field, which improves calculation accuracy. In order to prevent the oscillations in simulation of current continuity equation, an upwind discontinuous Galerkin method is used, which relaxes the continuity requirement at interelement boundaries. The present approach is verified to be suitable for the simulation of the ion-flow problem from the HVDC transmission lines by compared with experimental results and previous methods.

Both practices and experiments have shown that the thermal conductivity of icing has an obvious influence on ice-melting process, but it is ignored by most of the existing models which set the simulation parameter as a constant. In this paper, an experimental study is conducted to investigate the thermal conductivity for overhead transmission line icing. Based on the test data in artificial icing laboratory, a quadratic equation of thermal conductivity and icing density is presented. And then, the equation of icing thermal conductivity is employed to simulate the critical ice-melting current and ice-melting time. The results of the experiment and simulation show that the thermal conductivity can improve the prediction accuracy in thermal de-icing projects, with the mean error of 4% and 14%, respectively.

Designing an outdoor insulation-appropriate material architecture with superior surface weatherability, hydrophobicity transfer, and electrical and mechanical properties would play an essential role in enhancing the security operations of power systems. In this work, a cycloaliphatic epoxy resin (CEP) was modified with organofluorine and organosilicon to introduce functional groups to improve its surface properties. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectral analysis showed that these functional groups were successfully introduced into the modified CEP. The characteristics of the modified CEP were assessed in terms of weather resistance, mechanical properties and hydrophobicity. The results show that the modified CEP composite surface integrates the complementary characteristics of multiple components, thereby greatly improving the surface impact toughness, hydrophobicity and weatherability. The hydrophobicity migration of the new composite was tested. The results show that a large number of hydrophobic groups (Si−CH3) migrate to the sample surface, causing self-healing of hydrophobicity, which helps prevent pollution flashover. In addition, electric insulation tests were conducted on modified CEPs with different contents of micro-nanometre fillers without affecting the mechanical properties of the composite system. The test results revealed the best combination of inorganic fillers to improve the insulation performance. The micromorphology and mechanism of interaction between the CEP-based composite and nanoparticles were analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), thermally stimulated depolarization current (TSDC) and broadband dielectric spectroscopy. This work provides an invaluable guideline for the design of outdoor insulation composite materials.

The capacitive method is considered to be a suitable icing-detection technology, but the lack of fundamental parameters restricts the development of icing-detection sensors. In this paper, an artificial icing laboratory, a capacitive sensor, and some simulation conductors have been designed for obtaining the artificial icing samples. Subsequently, the same characteristic values of artificial icing have been measured by an LCR device, under a selected frequency. This research found that the value of the icing dielectric constant closely correlated with its density, internal sublayer, and the test temperature. Finally, a fitting formula has been presented for calculating the relative dielectric constant, which may provide some important reference value for the design of icing-detection sensors.

Background: Renal cell carcinoma (RCC) accounts for more than 90% of cancers in the kidney. RCC is often asymptomatic, as a result people with RCC generally have advanced disease by the time it is discovered and has a poor prognosis compared to other cancers. Therefore, it is necessary to explore its pathogenesis and identify some reliable prognostic biomarker of RCC. miRNAs are emerging as important players in the development and progression of RCC. miR-31-5p has been reported to act as a tumor suppressor in hepatocellular carcinoma (HCC). The aim of this study is to determine the detailed molecular mechanism of miR-31-5p in the progression of RCC and to investigate its potential clinical value. Methods: In this study, RT-qPCR, EdU assay, CCK-8 assay, wound scratch assay, transwell assay, flow cytometry assay and cell cycle assay were performed to detect miR-31-5p expression and its functions in RCC. Moreover, 42 formalin-fixed paraffin-embedded (FFPE) RCC samples were used to analyze the relationship between miR-31-5p expression and patients’ overall survival. Finally, luciferase reporter assay, RT-qPCR assay and western blot were used to explore the association between miR-31-5p and its potential targets. Results: miR-31-5p was significantly down-regulated in RCC tissues and RCC cell lines compared with paired adjacent normal tissues and normal cell lines. miR-31-5p downregulation was associated with poor prognosis in RCC patients. Overexpression of miR-31-5p inhibited RCC cell proliferation, migration and invasion and cell cycle. Conversely, down-regulation of miR-31-5p promoted cell proliferation, migration and invasion. Furthermore, cyclin-dependent kinasec1 (CDK1), a key player in cell cycle regulation, was identified as a functional target of miR-31-5p. Conclusions: Our results suggest that miR-31-5p serves as a tumor suppressor in RCC and is expected to be a molecular biomarker for poor prognosis of RCC.

The intelligent fault diagnosis of power transformer is the main link to promote the development of smart grids, but the traditional single intelligent diagnosis algorithms cannot process the huge amount of the incomplete fault information of the transformers effectively, resulting in low accuracy of fault diagnosis. Therefore, combining the dissolved gas analysis (DGA) technology, a transformer fault diagnosis method based on Gray Wolf Optimization algorithm (GWO) optimized hybrid kernel extreme learning machine is proposed in this paper. Firstly, based on Mercer's theorem, a hybrid kernel extreme learning machine model is constructed by combining the local radial basis kernel function and the global polynomial kernel function. Secondly, the parameters of hybrid kernel function can be optimized by the GWO algorithm. Meanwhile, the Logistic chaotic map is used to generate the initial population parameters of the GWO algorithm, which makes the distribution of initial population parameters as evenly as possible to avoid adverse effect of convergence speed and the optimization results. The results show that the presented algorithm in this paper improves the accuracy of transformers fault diagnosis compared with the BP neural network and the extreme learning machine algorithm, which has the strong learning ability and generalization performance.

In view of the settlement problem of transmission tower foundation, the excitation device is used to generate impulse excitation, and the transmission tower vibrates under impulse excitation. The vibration characteristics of transmission towers under impulse excitation are experimentally measured. In this paper, the conductor spanning 105m at Xi'an Polytechnic University are measured and analyzed. Firstly, the excitation device, acceleration sensor and condition monitoring device are installed on the transmission tower. Secondly, the excitation device generates impulse excitation, and the acceleration sensor collects the impulse response of the tower in real time. Then, the settlement of the tower is simulated manually. Finally, the natural frequencies of the transmission tower under impulse excitation before and after settlement are extracted by modal analysis, and the relationship between the natural frequencies of each mode is analyzed. A set of complete on-line monitoring system for transmission tower settlement is established, and the online monitoring of transmission towers is realized.

The power equipment is an important component of the power system, which will seriously threat the stability of power system when the heat fault occurs during its running. An integrated system has been designed in this paper directed against the characteristics of thermal fault, which can implement the functionality of temperature acquisition, realtime display and fault warning. The real-time temperature can be stably collected via wireless transmission, low-power technology and so on. The dynamic threshold algorithm based on beta distribution is used to eliminate the singularity data that potential introduced in the process of data transmission or acquisition. The development trend of the equipment temperature can be predicted by means of the temperature prediction model established through the process neural network. The experimental results show that the system can effectively measure and display the temperature of power equipment and predict the development of temperature trend, which has higher precision.

The traditional HTV silicone rubber composite insulators are widely used in power transmission lines at home and abroad due to their excellent hydrophobicity and hydrophobicity. However, with the development of UHV, more and more transmission lines need to cross strong ultraviolet radiation, strong wind sand and bird pecking regions. In this kind of bad climate regions, it is very easy to cause the decline of the external insulation performance of traditional HTV silicone rubber insulators and the damage of materials. Aiming at this situation and combining with the ultraviolet radiation characteristics of high altitude area, UCV is used as ultraviolet light source, and the high polymer composite insulators with strong resistance to ultraviolet, climate and stable mechanical properties provided by the global energy economic institute are selected as the research object. The purpose is to study the aging characteristics of new composite insulators in the high ultraviolet radiation area of the Northwest Plateau. The results show that under the continuous irradiation of UCV short wave ultraviolet light, the tensile strength and hardness of the epoxy material are much higher than that of the silicone rubber. It has better toughness and has reached the purpose of bird proof and tread resistance. However, hydrophobicity is slightly less than silicone rubber material, but compared with traditional epoxy materials, it has made considerable progress to meet outdoor operation requirements.

In this paper., a broken strands detection method by vibration signal analyzing is proposed. The change of dynamic response of ACSR's structure reflected the change of ACSR's structure. Broken strands monitoring system., composed of acceleration sensor., condition monitoring device and monitoring center., is designed in this paper. Further., modal experiment is carried out. We use the shaker to provide a vibration range 10 Hz to 100 Hz making the ACSR vibrated. The vibration acceleration signal is processed by filtering., PSD analysis and frequency response function analysis. The results show that the natural frequencies of conductor decreases obviously after breaking a strand. Some of the natural frequencies which changed more obviously decreased by 4.8%., meaning that it is feasible to detected broken strands by natural frequencies. (Abstract)

In this paper, a new algorithm based on a combined neural network is proposed to improve salient object detection in the complex images. It consists of two main steps. The first step, an objective function which is optimized on a multi-layer graph structure is constructed to diffuse saliency from borders to salient objects, aiming to roughly estimate the location and extent salient objects of an image, meanwhile, color attribute is adopted to rapidly find a set of object-related regions in the image. The second step, establish a combined neural network with Region Net and Local-Global Net. Region Net is adopted to efficiently generate the salient map with the sharp object boundary. Then Local-Global Net based on multi-scale spatial context is proposed to provide strongly reliable multi-scale contextual information, and thus achieves an optimized performance. Experimental results and comparison analysis demonstrate that the proposed algorithm is more effective and superior than most low-level oriented prior methods in terms of precision recall curves, F-measure and mean absolute errors.

Transmission lines are affected by Aeolian vibration, which causes strands to break and eventually causes an entire line to break. In this paper, a method for monitoring strand breaking based on modal identification is proposed. First, the natural frequency variation of a conductor caused by strand breakage is analyzed, and a modal experiment of the LGJ-95/15 conductor is conducted. The measurement results show that the natural frequencies of the conductor decrease with an increasing number of broken strands. Next, a monitoring system incorporating a fiber Bragg grating (FBG)-based accelerometer is designed in detail. The FBG sensor is mounted on the conductor to measure the vibration signal. A wind speed sensor is used to measure the wind speed signal and is installed on the tower. An analyzer is also installed on the tower to calculate the natural frequencies, and the data are sent to the monitoring center via 3G. Finally, a monitoring system is tested on a 110 kV experimental transmission line, and the short-time Fourier transform (STFT) method and stochastic subspace identification (SSI) method are used to identify the natural frequencies of the conductor vibration. The experimental results show that SSI analysis provides a higher precision than does STFT and can extract the natural frequency under various wind speeds as an effective basis for discriminating between broken strands.

In view of the settlement problem of transmission tower foundation, the vibration characteristics of transmission towers under wind force are measured experimentally. In this paper, the 110 kV cat head transmission tower of Xi&rsquo, an Polytechnic University is measured and analyzed. Firstly, the acceleration sensor and meteorological sensor are installed on the tower to collect the vibration response and environment parameters of the tower in real time. Then, an experiment platform is built to simulate the tower settlement, and the vibration response of the tower after settlement is measured in time. Finally, the low-order modal frequencies of the transmission tower before and after settlement under wind force load are extracted by stochastic subspace identification (SSI), and the relationship between modal frequencies of different modes is analyzed via temperature correction. By comparison and analysis, it is obvious that the X-direction modal frequencies before and after settlement under natural wind load are changed, and the change rate increases with the increase of settlement displacement, which can be used as effective evidence for judging the settlement of transmission tower foundation.

The vibration of ice-shedding on overhead transmission lines will result in serious damage to tower-line system. In order to reveal the effect law of the different time parameter on the jump height of iced overhead lines after ice shedding, the conductor-insulator coupled finite element model was established, and the additional force method was employed to simulate the process of ice-shedding from overhead transmission lines, then the values of jump height were obtained for simultaneous total-span ice-shedding, unzipping ice-shedding, and assembling ice-shedding. Results from this study showed that, the difference between numerical simulation result and formula calculation result was negligible for simultaneous total-span ice-shedding. The dynamic response of unzipping ice-shedding is close to static unloading when the velocity was lower than 20m/s, the jump height was far less than calculated value by empirical formula, but the jump height of unzipping ice-shedding is close to simultaneous total-span ice-shedding effect when the velocity of ice-shedding is higher than 50m/s. The minimum jump height occurs when ΔT=T/2 for one-span assembling ice-shedding; and the maximum jump height occurs when ΔT=T/8, which may slightly greater than simultaneous total-span ice-shedding because of conductor coupling effect.

Icing on transmission line is a major risk factor for the safety of the power system. Therefore, it is necessary to research on online monitoring system and prediction model of icing. At present, there are many kinds of the icing prediction models are based on micro meteorological conditions, but the errors of the prediction are caused by the time-varying characteristics of the meteorological conditions and the error accumulation. On account of icing growth is a time accumulation process, this paper presents a new transmission line icing short-term forecast model based on improved time series analysis of fireworks algorithm, and by using icing accumulation, the error caused by meteorological parameters can be reduced to a minimum level. Finally, the model is verified and analyzed by simulating transmission line icing on the simulation platform for power system micro climate simulating, the short-term forecasting average absolute error of the model is 1.34%. Moreover, using the icing field monitoring data on Guizhou Grid, the mean error of this prediction model is 2.67%, which is much better than the conventional models.