• The Transactions of the Korean Institute of Electrical Engineers
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• v.37 no.1
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• pp.1-9
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• 1988

This paper descibes a method for the state estimation in power systems with interconnected AC/DC system. The state values in interconnected AC/DC system are estimated using measurement values with the pseudo measurement so that the number of telemetering measurement can be reduced. Especially, the state values in AC system are estimated through hierarchical method after system decomposition including superposition bus was formed for the state estimation in large-scale power systems. The results of the application to the two model power systems show the dffectiveness of the presented algorithms.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2000.12a
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• pp.161-164
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• 2000

Recently efficient image coding using zerotree have been proposed. In these methods, the locations of nonzero wavelet coefficient are encoded with a tree structure, called zerotree, which can exploit the self-similarity of the wavelet pyramid decomposition across different scales. These are very especially in low bit rate image coding. In this paper, two zerotree image coding algorithm, EZW and SPHIT are briefly introduced, and a new zerotree searching scheme is proposed to emphasize the significance of a wavelet coefficient by its orientation as well as its scale.

• Wind and Structures
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• v.17 no.6
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• pp.609-627
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• 2013

The Yingxian wooden tower in China is currently the tallest wooden tower in the world. It was built in 1056 AD and is 65.86 m high. Field measurements of wind speed and wind-induced response of this tower are conducted. The wind characteristics, including the average wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale and velocity spectrum are investigated. The power spectral density and the root-mean-square wind-induced acceleration are analyzed. The structural modal parameters of this tower are identified with two different methods, including the Empirical Mode Decomposition (EMD) combined with the Random Decrement Technique (RDT) and Hilbert transform technique, and the stochastic subspace identification (SSI) method. Results show that strong wind is coming predominantly from the West-South of the tower which is in the same direction as the inclination of the structure. The Von Karman spectrum can describe the spectrum of wind speed well. Wind-induced torsional vibration obviously occurs in this tower. The natural frequencies identified by EMD, RDT and Hilbert Transform are close to those identified by SSI method, but there is obvious difference between the identified damping ratios for the first two modes.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.17 no.2
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• pp.1-10
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• 2021

Lithium-ion batteries with high energy density, long cycle life and other advantages, have been widely used to energy storage systems(ESS). But as ESS fires frequently occur, the safety concern has become the main obstacle that hinders the large-scale applications of lithium-ion batteries. Especially, thermal runaway is the key scientific problem in battery safety research. Therefore, in this study, we performed a numerical analysis on the thermal runaway phenomenon of NCM111, NCM523 and NCM622 batteries using a two-dimensional analysis model. The results show that the two-dimensional simulation results are generally matched with three-dimensional simulation. Also, In the case of NCM111 with a low Ni content in the temperature range used in this study, thermal runaway phenomenon does occurred very slowly, but as the Ni content is increased, the thermal runaway phenomenon occurs rapidly and the thermal stability tends to be decreased. And, in NCM523 and NCM622 batteries, chain reactions occur almost simultaneously, but in the case of NCM111 battery, it is found that after the SEI(Solid Electrolyte Interface) layer decomposition reaction, the cathode-electrolyte reaction is appeared sequentially. After that, the anodic decomposition reaction is increased and leads to the thermal runaway reaction.

• Clean Technology
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• v.17 no.3
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• pp.250-258
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• 2011

Thermal plasma has been presented for the decomposition of perfluorocompounds (PFCs) which are extensively used in the semiconductor manufacturing and display industry. We developed pilot-scale equipment to investigate the large scale treatment of PFCs and called it a "thermal plasma scrubber". PFCs such as $CF_4$, $C_2F_6$, $SF_6$, and $NF_3$ used in experiments were diluted with $N_2$. There were two different types of experiment setup related to the water spray direction inside the thermal plasma scrubber. The first type was that the water was sprayed directly into the gas outlet located at the exit of the reaction section. The second type was that the water was sprayed on the wall of the quenching section. More effective decomposition took place when the water was sprayed on the quenching section wall. For $C_2F_6$, $SF_6$, and $NF_3$ the maximum destruction and removal efficiency was nearly 100%, and for $CF_4$ was up to 93%.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.681-690
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• 1999

본 논문에서는 요소를 사용하지 않은 수치해석기법인 무요소법 중에서 다중해상도(multi-resolution)특성이 내재되어 있는 Reproducing Kernel Particle Method (RKPM)의 이중스케일 분해기법을 사용하여 RKPM의 형상함수를 상단성분과 하단성분으로 분리하고 이를 3차원 선형탄성해석과정에 적용하여 von Mises 응력장의 상·하단성분을 유도하였다. 유도된 응력장의 상단성분을 이용하여 후처리과정을 거치지 않고도 응력의 고변화도 부위를 손쉽게 파악할 수 있는 기법을 개발하였으며 이를 이용한 효율적인 적응적 세분화기법의 적용가능성을 연구하였다. 대표적인 2차원 및 3차원 응력집중 문제에 적용하여 응력집중부위를 파악하고 간단한 적응적 세분화과정에 따른 절점추가를 통하여 해의 정도 향상을 파악해 본 결과, 본 연구에서 개발된 기법이 응력집중부위를 정확히 판정할 수 있었으며 효율적인 적응적 세분화기법의 유용한 도구로서 활용될 수 있음을 검증하였다.

• Journal of Information Processing Systems
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• v.13 no.6
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• pp.1628-1639
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• 2017

The combination texture feature extraction approach for texture image retrieval is proposed in this paper. Two kinds of low level texture features were combined in the approach. One of them was extracted from singular value decomposition (SVD) based dual-tree complex wavelet transform (DTCWT) coefficients, and the other one was extracted from multi-scale local binary patterns (LBPs). The fusion features of SVD based multi-directional wavelet features and multi-scale LBP features have short dimensions of feature vector. The comparing experiments are conducted on Brodatz and Vistex datasets. According to the experimental results, the proposed method has a relatively better performance in aspect of retrieval accuracy and time complexity upon the existing methods.

• Korean Management Science Review
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• v.15 no.1
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• pp.33-47
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• 1998

The facility location problem considered here is to determine facility location sites under future's uncertain demand. The objective of this paper is to propose a solution method and algorithm for a two-stage stochastic facility location problem. utilizing the Benders decomposition method. As a two-stage stochastic facility location problem is a large-scale and complex to solve, it is usually attempted to use a mean value problem rather than using a stochastic problem. Thus, the other objective is to study the relative error of objective function values between a stochastic problem and a mean value problem. The simulation result shows that the relative error of objective function values between two problems is relatively small, when a feasibility constraint is added to a facility location model.

• Structural Engineering and Mechanics
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• v.39 no.6
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• pp.813-831
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• 2011

This paper presents an efficient version of Hilbert-Huang transform for nonlinear non-stationary systems analyses. An ensemble empirical mode decomposition (EEMD) is introduced to alleviate the problem of mode mixing between intrinsic mode functions (IMFs) decomposed by EMD. Yet the problem has not been fully resolved when a signal of a similar scale resides in different IMF components. Instead of using a trial and error method to select the "best" outcome generated by EEMD, a hybrid algorithm based on EEMD and EMD is proposed for multi-mode signal processing. The developed approach comprises the steps from a bandpass filter design for regrouping modes of the IMFs obtained from EEMD, to the mode extraction using EMD, and to the assessment of each mode in the marginal spectrum. A simulated two-mode signal is tested to demonstrate the efficiency and robustness of the approach, showing average relative errors all equal to 1.46% for various noise levels added to the signal. The developed approach is also applied to a real bridge structure, showing more reliable results than the pure EMD. Discussions on the mode determination are offered to explain the connection between modegrouping form on the one hand, and mode-grouping performance on the other.

• Ocean Systems Engineering
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• v.6 no.3
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• pp.217-231
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• 2016

This paper presents a new approach for underwater image analysis using the bi-dimensional empirical mode decomposition (BEMD) technique and the phase congruency information. The BEMD algorithm, fully unsupervised, it is mainly applied to texture extraction and image filtering, which are widely recognized as a difficult and challenging machine vision problem. The phase information is the very stability feature of image. Recent developments in analysis methods on the phase congruency information have received large attention by the image researchers. In this paper, the proposed method is called the EP model that inherits the advantages of the first two algorithms, so this model is suitable for processing underwater image. Moreover, the receiver operating characteristic (ROC) curve is presented in this paper to solve the problem that the threshold is greatly affected by personal experience when underwater image edge detection is performed using the EP model. The EP images are computed using combinations of the Canny detector parameters, and the binaryzation image results are generated accordingly. The ideal EP edge feature extractive maps are estimated using correspondence threshold which is optimized by ROC analysis. The experimental results show that the proposed algorithm is able to avoid the operation error caused by manual setting of the detection threshold, and to adaptively set the image feature detection threshold. The proposed method has been proved to be accuracy and effectiveness by the underwater image processing examples.