• Journal of Electrical Engineering and Technology
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• v.8 no.3
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• pp.499-506
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• 2013

The accurate estimation of a fault location is desired in distance protection schemes for transmission lines in order to selectively deactivate a faulted line. However, a typical method to estimate a fault location by calculating impedances with voltages and currents at relaying points may have errors due to various factors such as the mutual impedances of lines, fault impedances, or effects of parallel circuits. The proposed algorithm in this paper begins by extracting the fundamental phasor of the positive sequence currents from the three phase currents. The second-order difference of the phasor is then calculated based on the fundamental phasor of positive sequence currents. The traveling times of the waves generated by a fault are derived from the second-order difference of the phasor. Finally, the distance from the relaying point to the fault is estimated using the traveling times. To analyze the performance of the algorithm, a power system with EHV(Extra High Voltage) untransposed double-circuit transmission lines is modeled and simulated under various fault conditions, such as several fault types, fault locations, and fault inception angles. The results of the simulations show that the proposed algorithm has the capability to estimate the fault locations with high speed and accuracy.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.526-533
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• 2015

A new algorithm is proposed for the estimation of equivalent grid impedance at the point of common coupling of a grid-tie inverter output. The estimated impedance parameter can be used for the improvement of the performance and the stability of the distributed generation system. The estimation error is inevitable in the conventional estimation method because of the axis rotation due to PLL. In the conventional estimation error, the d-q voltage and current are used for the calculation of the impedance with active and reactive current injections. Conversely, in the proposed algorithm, the negative sequence current is injected, and then the negative sequence voltage is measured for the impedance estimation. As the positive and negative sequence current controller is independent and the PLL is based on the positive sequence component only, the estimation of the equivalent impedance can be achieved with high accuracy. Simulation and experimental results are compared to validate the proposed algorithm.

• Journal of applied mathematics & informatics
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• v.12 no.1_2
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• pp.299-305
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• 2003

The central limit theorems are obtained for stationary linear processes of the form Xt = (equation omitted), where {$\varepsilon$t} is a strictly stationary sequence of random variables which are either linearly positive quad-rant dependent or associated and {aj} is a sequence of .eat numbers with (equation omitted).

• Kyungpook Mathematical Journal
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• v.51 no.3
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• pp.345-352
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• 2011

In this article we introduce the fuzzy real valued double sequence spaces $_2{\ell}^F$ (p) where p = ($p_{nk}$) is a double sequence of bounded strictly positive numbers. We study their different properties like completeness, solidness, symmetricity, convergence free etc. We prove some inclusion results also.

• Journal of applied mathematics & informatics
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• v.32 no.3_4
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• pp.331-341
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• 2014

In this article we introduce the sequence spaces $_2c^I_0(f,p)$, $_2c^I(f,p)$ and $_2l^I_{\infty}(f,p)$ for a modulus function f, where $p=(p_k)$ is a sequence of positive reals and study some of the properties of these spaces.

• Journal of Microbiology and Biotechnology
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• v.8 no.4
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• pp.310-317
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• 1998

Peptide synthetases are large multifunctional enzyme complexes that catalyze the nonribosomal synthesis of a structurally diverse family of peptide antibiotics. These enzymes are composed of functionally independent domains with independent enzymatic activities. Their specific linkage order of domains forms the protein template that defines the sequence of the incorporated amino acids. Within each domain, several motifs of highly conserved sequences have been identified from the sequence alignment of the various peptide synthetases ［30］. Taking advantage of the conserved nucleotide sequence of Core 1 and Core 2, we designed PCR primers to amplify the peptide synthetase genes from three different gram-positive bacterial strains. Nucleotide sequence analysis of the amplified PCR products from those three strains showed significant homology to various peptide synthetase genes, suggesting that the PCR products are parts of peptide synthetase genes. Therefore, this rapid and efficient PCR technique can be used for the isolation of peptide synthetase genes from various strains.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.283-290
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• 2022

This study proposes a voltage control scheme in a synchronous reference frame to improve the dynamic characteristics of double-conversion UPSs. UPSs need to control positive and negative sequence voltage, so that positive and negative sequence extractors are generally used to obtain each sequence of the voltage and current. Voltage and current controllers for each sequence are implemented. However, the extractor causes considerable delay, and the delay restricts the control performance, especially for the current controller. To improve the dynamics of the current controller, the proposed scheme adopts a unified current controller without separating positive and negative sequences. By using discrete-time current controller, the control bandwidth can be extended significantly so that negative sequence current can be controlled. To enhance the performance, an additional feed-forward technique for output voltage regulation is proposed. The validity of the proposed controller is verified by experiments.

• Bulletin of the Korean Mathematical Society
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• v.38 no.2
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• pp.231-236
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• 2001

In this note we construct a sequence of Picard iterates suitable for the approximation of solutions of K-positive definite operator equations in arbitrary real Banach spaces. Explicit error estimate is obtained and convergence is shown to be as fast as a geometric progression.

• Journal of Microbiology and Biotechnology
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• v.3 no.2
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• pp.86-90
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• 1993

CMCase positive clones were screened from Cellulomonas sp. YE-5 and named pCE1, pCE2 and pCE3. Among the positive clones pCE1 was used for this study, because it has the smallest insert and the highest CMCase activity among the 3 clones, and its nucleotide sequence was determined. The CMCase gene in pCE1 was composed of 1071 bp of nucleotides coding 357 amino acids. Computer analysis showed that the pCE1 has 65% sequence homology with the endoglucanase from Cellulomonas fimi.

• Bulletin of the Korean Mathematical Society
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• v.40 no.4
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• pp.603-611
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• 2003

In this paper we extend the definition of K-positive definite operators from linear to Frechet differentiable operators. Under this setting, we derive from the inverse function theorem a local existence and approximation results corresponding to those of Theorems land 2 of the authors [8], in an arbitrary real Banach space. Furthermore, an asymptotically K-positive definite operator is introduced and a simplified iteration sequence which converges to the unique solution of an asymptotically K-positive definite operator equation is constructed.