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With the development of extra-high voltage and ultra-high voltage transmission line in China, the reradiation interference generated by induced current on the surface of transmission steel tower becomes more serious to the radio station in the vicinity. In this paper, the calculation method for reradiation interference of transmission steel tower based on method of moment is analyzed. And in order to reduce the impedance matrix storage data in the memory space and the number of iterations in the calculation, the preprocessing of matrix sparse and diagonal norm precondition is presented to improve the performance of the conjugate gradient algorithm for the reradiation interference calculation. The reradiation interference of a standard 500 kV transmission steel tower is calculated using the improved conjugate gradient algorithm. And the results show that the algorithm enhances the convergence and stability after preprocessing and is suitable to calculate the reradiation interference of super-large metal truss structure target.

Abstract At high altitudes, the corona discharge around a conductor surface is severe, and the induced audible noise (AN) is irritating; this is due to the low air density at high altitudes. Therefore, AN has become a crucial limiting factor in the design of ac power lines of 500 kV or higher at high altitudes. An investigation of the spectral characteristics of AN should help provide a greater understanding of corona noise; however, only a few studies have investigated the spectral characteristics of AN in practical bundled conductors at high altitude. Therefore, it is difficult for power utility companies to select suitable conductors. In this study, the AN spectral characteristics of 6 × LGJ400, 6 × LGJ720, and 8 × LGJ500 bundled conductors were investigated using an ultra‐high‐voltage corona cage (8 × 8 × 35 m) in Xining, Qinghai Province (altitude: 2261 m). The AN equivalent A‐weighted level and the 1/3‐octave frequency characteristics of these three conductors were obtained, and the influence of the electric field (E‐field) on these characteristics was analysed. Subsequently, the relationship between the AN A‐weighted level and the 8‐kHz level was examined. We found that, with the increase of the E‐field, the low‐frequency components of AN level did not exhibit an obvious trend, but in the high‐frequency band (1.6–20 kHz), a clear positive correlation was observed between the spectrum level and E‐field strength. Among these three conductors, the 8 × LGJ500 conductor was the optimal conductor for reducing the AN levels at high altitude. The results obtained in this study can provide a data reference for the construction of high‐altitude ac power lines.

In this paper, a new algorithm for predicting per unit length (p.u.l) parasitic parameters of transmission line is proposed. In the twisted-wire pair (TWP), different rotation degrees correspond to different parasitic parameters, which brings difficulties to the solution of telegraph equation. At present, the mainstream method is to divide TWP and use the cascade theory to solve each segment as a parallel transmission line. Therefore, we propose to use the beetle swarm optimization (BSO) algorithm to optimize the weights of the back propagation neural network, use a certain sample to train the network. This algorithm is used to predict the p.u.l parameters of uniform and non-uniform TWP, and the finite-difference time-domain (FDTD) method is used to solve telegraph equation. Among them, the crosstalk value of the uniform TWP is compared with the simulation value in the CST to verify the effectiveness of the proposed algorithm; the non-uniform TWP performs 500 random generation calculations to give the maximum envelope value of the crosstalk.

With the development of ultrahigh-voltage transmission lines in China, the reradiation interference caused by the steel tower used in ultrahigh-voltage transmission becomes increasingly aggravating for nearby radio stations. In this paper, using the multilevel fast multipole algorithm, the reradiation interference of an ultrahigh-voltage transmission steel tower is investigated. Additionally, the reradiation interference characteristics of a transmission steel tower were investigated with various frequencies and azimuth angles of incidence wave. The results show that the frequency and the azimuth angle of incident wave are the impact factors for the reradiation interference of steel towers. It is better to use a detailed angle steel model for the truss structure of steel towers at high frequency, while a simplified structural model can be used at low frequency. Additionally, the diffraction at the edge of the angle steel has a great influence on the reradiation interference, particularly at high frequencies.

Background: Whether electromagnetic field (EMF) exposure affects the function of the cardiovascular system is under debate. The present study aimed to investigate the effects of 500 μT EMF exposure on the cardiovascular system in rats.Methods: Forty-eight-week-old male Sprague-Dawley rats were randomly divided into two groups: the sham group and the exposure group. During 24-week EMF exposure (20 h per day), the blood pressure and pulse rate were recorded every 4 weeks. Before sacrifice, electrocardiography, echocardiography, and cardiac catheterization analysis were conducted to evaluate the cardiac function. Meanwhile, hematoxylin-eosin (HE) staining, Western blot, and real-time polymerase chain reaction (PCR) were performed to identify morphological and molecular changes indicative of cardiac remodeling.Results: The heart rate, blood pressure, and pulse rate were not influenced by EMF exposure compared with the control group. In addition, HE staining showed no change in the morphology and arrangement of cardiomyocytes. Further, we found that the mRNA and protein levels of cardiac hypertrophy-related genes were not affected by EMF exposure. Finally, no significant difference was observed in cardiac function between the two groups by echocardiography and cardiac catheterization detection.Conclusion: The 24-week exposure to EMF at 500 μT did not have apparent effects on the cardiovascular system in rats, at least for the variables studied.

The effects of exposure to magnetic fields (MFs) at electric frequencies (50–60 Hz) on carcinogenicity are still in debate. Whether exposure to MFs affects the heart is also a debated issue. This study aimed to determine whether exposure to extremely low frequency MFs (ELF-MFs) induced DNA damage in cardiomyocytes both in vitro and in vivo. Human ventricular cardiomyocytes were exposed to 50 Hz ELF-MF at 100 µT for 1 h continuously or 75 min intermittently. The effects of the treatments were evaluated by DNA damage, redox status changes and relative signal molecular expression. Moreover, ten male Sprague-Dawley rats were exposed to a 50 Hz MF at 100 µT for 7 days, while another 10 rats were sham exposed. The protein levels of p53 and Hsp70 in heart tissue were analyzed by western blot. The results showed that exposure to ELF-MF did not induce DNA damage, changes to cell cycle distribution or increased reactive oxygen species level. No significant differences were detected in p53 and Hsp70 expression level between the ELF-MF and sham-exposure groups both in vitro and in vivo. All these data indicate that MFs at power-frequency may not cause DNA damage in cardiomyocytes. This article has an associated First Person interview with the first author of the paper.

Quenching and tempering are mostly employed to tune the mechanical properties of the high-carbon steels. In the present study, transmission electron microscopy (TEM) and selected area electron diffraction (SAED) are used to examine the microstructural evolution in quenched and tempered high carbon steels. In quenched specimens, the ω-Fe(C) phase is a common substructure in twinned martensite and its diffraction spots are located at 1/3 and 2/3 (21¯1)α-Fe positions along the [011]α-Fe zone axis (ZA). When specimens are in-situ heated in TEM, few additional diffraction spots are observed at 1/6, 3/6 and 5/6 (21¯1)α-Fe positions along the [011]α-Fe ZA. Moreover, martensite decomposes into a lamellar structure and ω-Fe(C) phase transforms into θ-Fe3C cementite during tempering. The TEM and electron diffraction analysis reveals that diffraction spots of θ-Fe3C cementite phase are located at 1/6, 2/6, 3/6, 4/6 and 5/6 (222¯)α-Fe and (21¯1)α-Fe along [112]α-Fe and [011]α-Fe ZAs. Furthermore, the orientation relationships between θ-Fe3C cementite and α-Fe are indexed as: [013]θ//[112]α-Fe, [001]θ//[011]α-Fe, [1¯13]θ//[111]α-Fe and [1¯02]θ//[131]α-Fe, which are related to the transformation of ω-Fe to θ-Fe3C cementite. The current study provides a baseline to understand the microstructural evolution in high carbon steels during heat treatment processes.

Based on the theory of multi-conductor transmission lines (MTL), this paper proposes a new method for predicting and suppressing crosstalk of twisted-wire pair (TWP). The per unit length (p.u.l) RLCG parameters change caused by the inconsistent cross-sectional shape of TWP, changes in parameters make it difficult to solve the telegraph equation. In this paper, the method of transmission lines cascade is used. TWP is divided into several segments, and p.u.l parameters of each segment are predicted. Compared with before method, we propose a higher precision algorithm--beetle swarm optimization (BSO) to optimize the weights of back-propagation (BP) neural network, which predict p.u.l parameters at each segment. On this basis, it is divided into two steps: 1) Use MTL frequency domain method combined with lines' terminal conditions to solve crosstalk and compare with CST simulation results; 2) Use the singular value decomposition (SVD) method to add matrix modules at both ends of lines for suppressing crosstalk. The results show that proposed method in this paper is consistent with the simulation, and the accuracy is higher than before. [ABSTRACT FROM AUTHOR]

This paper proposes a novel crosstalk prediction method between the triple-twisted strand (uniform and non-uniform) and the signal wire, that is, using back-propagation neural network optimized by the beetle antennae search algorithm based on chaotic disturbance mechanism (CDBAS-BPNN) to extract the per unit length (p.u.l) parameter matrix, and combined with the chain parameter method to obtain crosstalk. Firstly, the geometric model and cross-sectional model between the uniform triple-twisted strand and the signal wire are established, and the corresponding model between the non-uniform triple-twisted strand and the signal wire is obtained by the Monte Carlo (MC) method. Then, the beetle antennae search algorithm based on chaotic disturbance mechanism (CDBAS) and backpropagation neural network (BPNN) are combined to construct a new extraction network of the p.u.l parameter matrix, and the chain parameter method is combined to predict crosstalk. Finally, in the verification and analysis part of the numerical experiments, comparing the crosstalk results of CDBAS-BPNN, BAS-BPNN and Transmission Line Matrix (TLM) algorithms, it is verified that the proposed method has better accuracy for the prediction of the model. [ABSTRACT FROM AUTHOR]

Power electronic devices and electrical equipment produce a large quantity of radiated electromagnetic interference (EMI) in the working process. Electromagnetic field analysis method of the near-field and far-field of the antenna can be employed to separate the radiated interference noises. However, the method has low separation accuracy and requires a lot of time. A novel method based on joint approximate diagonalization algorithm (JADA) to separate the radiated EMI noise is proposed in this paper. Compared with the traditional independent component algorithm method, the accuracy is improved by 14% and the efficiency is increased by 30%. The common-differential mode mixed noise source is taken as the experimental object to demonstrate the effectiveness and simplicity of the proposed method. [ABSTRACT FROM AUTHOR]

The effects of high voltage electromagnetic fields (EMF) on populations of aphpids, leaf miners and snails associated with rapeseed under subtropical conditions were studied. A field study was conducted during the spring season of 2015, at Wuhan, China (30.59°N, 114.30E; 23.3 m asl). Plots with four different emission rates (0 kV, 5.2 kV, 26 kV and 39 kV) were established, each containing an EMF emission device located 2.6 m above the soil, Lipaphis erysimi aphid and Liriomyza brassicae leaf miner population densities were recorded at 10 d intervals throughout the cropping season. Aphids, leaf miners and snails infested all plots, but significantly higher population densities of all pests were observed in control plots. The plots with the highest emission rate (39 kV) had lower population densities of pests throughout the entire experiment. High voltage EMF may have the ability to suppress pests of rapeseed. However, much remains to be learned about the suitability and reliability of EMF for insect suppression. [ABSTRACT FROM AUTHOR]

A correction system for geomagnetic observation against interference from the UHVDC power line is developed. The system could offer accurate calculation of interference value and, thus, realize the real-time correction in the Z component observation of the geomagnetic field. Based on the 3-D current magnetic-field calculation model of the dc power line, in which the towers as points and the tower spans as line segments, the calculation equation of the pace current magnetic-field vector projected on the direction of the Z component vector is acquired to calculate the interference value from the power line. Using Microsoft Visual Basic 6.0, the system receives the values of imbalance current on the UHVDC power line and geomagnetic Z component observation through the PC serial port. Consequently the real-time calculation of interference value on the Z component from the power line is realized. Then, the actual geomagnetic observation curve is acquired. During the live debugging period of \pm 800~kV Xiangjiaba—Shanghai UHVDC power line, the high accuracy of the correction system is verified by the joint experiment of the current observation in converter stations and the indoor/infield geomagnetic observation. [ABSTRACT FROM PUBLISHER]

To adapt to the trend toward low-energy precision irrigation, the droplet distributions for two new prototype sprinklers, outside signal sprinkler (OS) and fluidic sprinkler (FS), were compared with impact sprinkler (IS). A laser precipitation monitor was used to measure the droplet distributions. Droplet size and velocity distributions were tested under four operating pressures for nozzles 1.5 m above the ground. For the operating pressures tested, the mean OS, FS and IS droplet diameters ranged from 0 to 3.4, 0 to 3.5, 0 to 4.0 mm, respectively. The mean OS and FS droplet velocities ranged from 0 to 6.3 m·s-1, whereas IS ranged from 0 to 6.3 m·s-1. Being gas-liquid fluidic sprinklers, droplet distributions of the OS and FS were similar, although not identical. IS mostly produced a 0.5 mm larger droplet diameter and a 0.5 m·s-1 greater velocity than OS and FS. A new empirical equation is proposed for determination of droplet size for OS and FS, which is sufficiently accurate and simple to use. Basic statistics for droplet size and velocity were performed on data obtained by the photographic methods. The mean droplet diameter (arithmetic, volumetric and median) decreased and the mean velocity increased in operating pressure for the three types of sprinkler.