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Jun Zou,Jiang, T.N.,Jae Bok Lee,Chang, S.H. IEEE 2010 IEEE transactions on electromagnetic compatibility Vol.52 No.1
<P>The evaluation of the electromagnetic field radiated by a lightning stroke is of essential importance for the study of the interaction between lightning electromagnetic fields and power lines, or other sensitive installations. A fast algorithm for calculating the fields generated by a vertical electric dipole over a lossy ground, which can be expressed by the well-known Sommerfeld integrals, is presented in this paper. The integrals are decomposed into two parts. One part can be calculated by a recursive analytical expression, and the other part can be evaluated numerically due to the fact that the extracted integrand damps rapidly with the help of the asymptotic extraction technology. A comparison with some approximate formulas is performed in detail with variable parameters, such as the soil parameters, the geometry, and the excitation frequency of dipole, which shows very good agreement as far as the lightning field is concerned. The technical merit of the proposed approach is its universality, which can be applied for arbitrary parameters, and its computing time is still competitive.</P>
Zou, Jun,Lee, Jae-bok,Li, JunJie,Chang, Sughun Emerald Group Publishing Limited 2011 Compel Vol.30 No.2
<B>Purpose</B> - The purpose of this paper is to present an original iterative nodal approach to calculate the fault current distribution on overhead lines. <B>Design/methodology/approach</B> - By changing the mutual couplings among different conductors into the equivalent voltage sources, node voltages are updated iteratively by using conventional nodal analysis with those additional sources until the convergence is achieved. <B>Findings</B> - The proposed algorithm can handle the complicated topology of a power transmission line and has no difficulties in taking all physical couplings into account. The fault current distribution calculated by this method is in good agreement with those published in the literature. Although the proposed approach is iterative, the CPU time needed is still reasonable compared to the direct solution approach. The memory requirement is low because the coefficient matrix is highly sparse for the nodal analysis of each iteration loop. <B>Originality/value</B> - The proposed approach can serve as an alternative in calculating the fault current because of its efficiency and ease of implementation.
Jun Zou,Huihui Gong,Tae-Jin Yang,Jinling Meng 한국작물학회 2009 Journal of crop science and biotechnology Vol.12 No.1
As a major part of most plant genomes, retrotransposons are distributed throughout the plant genome ubiquitously with high copy number and extensive heterogeneity. Various retrotransposon families with distinct structures differ in their distribution and roles among divergent plant species, due to the unforeseen transposition activities. Regulation of transposition is relatively complex and three factors such as maintaining structure for none- or cis- or trans-acting transposition, control by host genome and induction by biotic and abiotic stress may contribute altering its transposition activity. The important roles of retrotransposons to modify genome size, remodel genome structure, and displace gene functions in the plant genome have been proven by a growing number of research studies up to now, which indicates that retrotransposons are a great driving force in genome evolution. For this review, we summarized the latest theoretic and practical research progress on plant retrotransposons for their distribution, regulation of activity, the impact on the architecture of plant genomes, and put forward the future prospects. As a major part of most plant genomes, retrotransposons are distributed throughout the plant genome ubiquitously with high copy number and extensive heterogeneity. Various retrotransposon families with distinct structures differ in their distribution and roles among divergent plant species, due to the unforeseen transposition activities. Regulation of transposition is relatively complex and three factors such as maintaining structure for none- or cis- or trans-acting transposition, control by host genome and induction by biotic and abiotic stress may contribute altering its transposition activity. The important roles of retrotransposons to modify genome size, remodel genome structure, and displace gene functions in the plant genome have been proven by a growing number of research studies up to now, which indicates that retrotransposons are a great driving force in genome evolution. For this review, we summarized the latest theoretic and practical research progress on plant retrotransposons for their distribution, regulation of activity, the impact on the architecture of plant genomes, and put forward the future prospects.
Zou, Jun,Zhou, Chenglong,Li, Wenwen,Lee, Jae-bok,Chang, Sughun Emerald Group Publishing Limited 2013 Compel Vol.32 No.6
<B>Purpose</B> - The electromagnetic field radiated from a lightning channel is the excitation for analyzing the field-to-transmission line coupling problem. The purpose of this paper is to propose a novel efficient approach to evaluate the horizontal electric field of the lightning channel expressed by the generalized Sommerfeld integral. <B>Design/methodology/approach</B> - The asymptotic integral is extracted from the original one, which actually makes the Sommerfeld integral tail reach its convergence very quickly. To handle the sharp variance around k0, a closed-form integral, which is obtained by replacing the original kernel with an approximated function, is presented in detail. The numerical examples validated the proposed approach in the both frequency and time domain. <B>Findings</B> - The approach proposed in this paper has been validated by the comparison with results in other papers. The agreement among these results reaches very well, and the approach proposed in this paper is more efficient and easy to implement, especially for the calculation of the tail integral part. <B>Originality/value</B> - In accordance with the numerical experiments, the proposed approach can be served as a qualified candidate in terms of computational efficiency to evaluate the electromagnetic field generated by the lightning channel.
Jun Zou,Boyuan Zhang,Xuelong Du,Jaebok Lee,Munno Ju IEEE 2014 IEEE transactions on electromagnetic compatibility Vol.56 No.3
<P>An efficient approach to evaluate the radiated electromagnetic field of a lightning channel over a horizontally stratified conducting ground is proposed in this paper. The electromagnetic field component produced by a lightning channel, expressed in the form of generalized Sommerfeld integral (GSI) with a complicated integrand, is calculated along a newly proposed path in the complex plane. Due to the change of the integration path, the integrand in the GSI turns out to decay dramatically fast and without any oscillation at all. As explained in this paper, the larger horizontal distance will become the benefit to achieve a quicker convergence, which is just opposite to the case that the integration path is along the real axis. The validity of the proposed methodology is justified by the extensive comparison with the results in other publications. As a matter of fact, the methodology in this paper can be generalized to evaluate stratified conducting ground with any number of layers.</P>
Jun Zou,TaoBin Jin,WenWen Li,Jaebok Lee,Sughun Chang IEEE 2013 IEEE transactions on electromagnetic compatibility Vol.55 No.1
<P>The radiated horizontal electromagnetic field of a lightning channel acts as the excitation when the lightning-induced voltages on overhead lines are under study. To accelerate the calculation of the horizontal electric field of a lightning channel, a piecewise Hermite interpolation model is proposed, which exploits the distinct feature of the transmission line whose height keeps unchanged. In the piecewise Hermite interpolation model, the key technique is fast evaluating the derivative of the horizontal electric field expressed by the generalized Sommerfeld integral. In this paper, the moment technique is utilized to calculate the derivatives efficiently. As demonstrated in the numerical examples, the piecewise Hermite interpolation model can reach a high accuracy with a very low computation cost.</P>
Zou, Jun,Gong, Huihui,Yang, Tae-Jin,Meng, Jinling 한국작물학회 2009 Journal of crop science and biotechnology Vol.12 No.1
As a major part of most plant genomes, retrotransposons are distributed throughout the plant genome ubiquitously with high copy number and extensive heterogeneity. Various retrotransposon families with distinct structures differ in their distribution and roles among divergent plant species, due to unforeseen transposition activities. Regulation of transposition is relatively complex and three factors such as maintaining structure for none- or cis- or trans-acting transposition, being controlled by the host genome and induction by biotic and abiotic stress may contribute altering its transposition activity. The important roles of retrotransposons to modify genome size, remodel genome structure, and displace gene functions in the plant genome have been proven by a growing number of research studies till date, which indicates that retrotransposons are important driving force in genome evolution. For this review, we summarized the latest theoretic and practical research progresses on plant retrotransposons for their distribution, regulation of activity, the impact on the architecture of plant genomes, and put forward the future prospects.
Jun Zou,Mo Li,Jaebok Lee,Sughun Chang IEEE 2012 IEEE transactions on electromagnetic compatibility Vol.54 No.1
<P>A fast approach for evaluating the magnetic field in air generated by an underground conductor is proposed in this paper. By means of the asymptotic extraction technique, the magnetic field can be decomposed into two parts. One is the contribution from the asymptotic integrand, which can be calculated analytically; and the other can be expressed by a sum of the definite integral and the exponential integrals. Due to the fact that there is no improper integral involved, the approach proposed here is highly efficient. Meanwhile, the impact of the eddy current to the magnetic field is quantitatively analyzed. The proposed approach could be used in the electromagnetic environment assessment for underground power cable systems.</P>