• 전기의세계
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• 제22권2호
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• pp.40-44
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• 1973

A method for obtaining state equation for nonlinear time-varying RLC networks is presented. The nonlinear time-varying RLC elements are decomposed by using Murata method to formulate nonlinear state equation. A nonlinear time-varying RLC network containing twin tunnel diode is solved as an example. In consequence of solving the examjple, simple methods are presented for revising the original network model so that the formulation of state equation is simplified.

• 대한전기학회논문지
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• 제37권1호
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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.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.766-776
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• 2015

It is well known that series arc faults in Low Voltage DC (LVDC) distribution system occur at unintended points of discontinuity within an electrical circuit. These faults can make circuit breakers not respond timely due to low fault current. It, therefore, is needed to detect the series fault for protecting circuits from electrical fires. This paper proposes a novel scheme to detect the series arc fault using Wavelet Singular Value Decomposition (WSVD) and state diagram. In this paper, the fault detector developed is designed by using three criterion factors based on the RMS value of Singular value of Approximation (SA), Sum of the absolute value of Detail (SD), and state diagram. LVDC distribution system including AC/DC and DC/DC converter is modeled to verify the proposed scheme using ElectroMagnetic Transient Program (EMTP) software. EMTP/MODELS is also utilized to implement the series arc model and WSVD. Simulation results according to various conditions clearly show the effectiveness of the proposed scheme.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권1호
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• pp.145-164
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• 2014

Network virtualization provides a promising tool to allow multiple heterogeneous virtual networks to run on a shared substrate network simultaneously. A long-standing challenge in network virtualization is the Virtual Network Embedding (VNE) problem: how to embed virtual networks onto specific physical nodes and links in the substrate network effectively. Recent research presents several heuristic algorithms that only consider single topological attribute of networks, which may lead to decreased utilization of resources. In this paper, we introduce six complementary characteristics that reflect different topological attributes, and propose three topology-aware VNE algorithms by leveraging the respective advantages of different characteristics. In addition, a new KS-core decomposition algorithm based on two characteristics is devised to better disentangle the hierarchical topological structure of virtual networks. Due to the overall consideration of topological attributes of substrate and virtual networks by using multiple characteristics, our study better coordinates node and link embedding. Extensive simulations demonstrate that our proposed algorithms improve the long-term average revenue, acceptance ratio, and revenue/cost ratio compared to previous algorithms.

• 자원리싸이클링
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• 제14권2호
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• pp.28-32
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• 2005

화합물반도체 제조 공정에서 발생하는 GaAs scrap으로부터 열분해법을 이용하여 갈륨을 회수하기 위한 기초 실험으로 200 g/batch 규모의 진공 열분해 실험을 수행하였고, 이 결과를 이용하여 30 kg/batch 용량의 Packed Tower가 부착된 열분해 장치를 제작하였다. 기초실험 결과 GaAs의 열분해속도는 온도가 높아짐에 따라 커지지만, 특히 1000$^{\circ}C 이상에서는 갈륨의 증기압 또는 증가하므로 갈륨의 회수율이 낮아지는 것을 알 수 있었다. 노 내 압력이 2~2.5${\times}10^{-2} mmHg일 때 1000~1050$^{\circ}C에서 가장 좋은 결과를 보였고, 이때 89% 정도의 갈륨 회수율을 나타내었다. GaAs의 열분해 시 비소의 분압은 온도가 높아짐에 따라 증가하고 융점인 1237$^{\circ}C를 전환점으로 온도는 낮아져도 증기압은 높은 이력현상(Hysteresis)을 보이는데, 이와 같은 특성을 이용하여 산업 생산에 적용한 열분해장치 제작에서는 반응기 위에 충진탑을 설치하였다. 그 결과, 열분해 반응기 내의 온도가 융점 이상의 고온에서도 99% 정도의 높은 회수율을 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제20권12호
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• pp.1493-1500
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• 1999

The electronic transitions from the ground state to low-lying excited states of CF₃OH have been investigated using high level ab initio quantum mechanical techniques. Also the possible photodissociation procedures of CF₃OH have been considered. The highest level employed in this study is TZP CCSD(T) level of theory. The possible four low-lying excited states can result by the excitation of the lone pair electron (n) in oxygen to σ$^*$ molecular orbital in C-O or O-H bond. The vertical transition (n → σ$^*$) energy is predicted to be 220.5 kcal/mol (130 nm) at TZ2P CISD level to theory. The bond dissociation energies of CF₃OH to CF₃O +H and CF₃+OH have been predicted to be 119.5 kcal/mol and 114.1 kcal/mol, respectively, at TZP CCSD level of theory. In addition, the transition state for the unimolecular decomposition of CF₃OH into CF₂O + HF has been examined. The activation energy and energy separation for this decomposition have been computed to be 43.6kcal/mol and 5.0 kcal/mol including zero-point vibrational energy corrections at TZP CCSD(T) level of theory.ed phenols were also estimated.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1507-1517
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• 2023

Centrifugal pumps are a crucial part of nuclear power plants, and their dependable and safe operation is crucial to the security of the entire facility. Cavitation will cause the centrifugal pump to violently vibration with the large number of vacuoles generated, which not only affect the hydraulic performance of the centrifugal pump but also cause structural damage to the impeller, seriously affecting the operational safety of nuclear power plants. A closed cavitation test bench of a centrifugal pump is constructed, and a method for precisely identifying the cavitation state is proposed based on Complementary Ensemble Empirical Mode Decomposition (CEEMD) and Deep Residual Shrinkage Network (DRSN). First, we compared the cavitation sensitivity of pressure fluctuation, vibration, and liquid-borne noise and decomposed the liquid-borne noise by CEEMD to capture cavitation characteristics. The decomposition results are sent into a 12-layer deep residual shrinkage network (DRSN) for cavitation identification training. The results demonstrate that the liquid-borne noise signal is the most cavitation-sensitive signal, and the accuracy of CEEMD-DRSN to identify cavitation at different stages of centrifugal pumps arrives at 94.61%

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.55-60
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• 1986

Conditions for achieving noninteraction in nonlinear multivariable systems via the decomposition of state space are well established. The main contribution of this paper is to present a Standard Decomposed System (SDS). The SDS is similar to the decomposed system of Isidorl, Krener, Gori-Giorgi, and Monaco but has a finer structure. The finer structure parallels the one used by Gilbert for linear systems. A weaker form of noninteraction, based on input-output behaviour, is decoupling. Some connections between decomposition and decoupling are also established.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제26권1호
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• pp.1-22
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• 2022

A tandem queue that consists of nodes with buffers of finite capacity and general blocking scheme is considered. The service time distribution of each node is exponential whose rate depends on the state of the node. The blocking scheme at a node may be different from that of other nodes. An approximation method for the system based on decomposition method is presented. The effectiveness of the method is investigated numerically.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.791-793
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• 2009

Hydrogen has been recognized of the energy source for the future, in terms of the most environmentally acceptable energy source. A pressurized fluidized bed reactor made of carbon steel with 0.076 m I.D. and 1.0 m in height was employed for the thermocatalytic decomposition of methane to produce amount of $CO_2$ - free hydrogen with validity from a commercial point of view. The fluidized bed was proposed for withdrawing of product carbons from the reactor continuously. The methane decomposition rate with the carbon black N330 catalyst was rapidly reached a quasi-steady state and remained for several hour. The methane thermocatalytic decomposition reaction was carried out at the temperature range of 850 - 950 $^{\circ}C$, methane gas velocity of 2.0 $U_{mf}$ and the operating pressure of 1.0 -3.0 bar. Effect of operating parameters such as reaction temperature, pressure on the reaction rates was investigated and predicted the effect of a change in conditions on a chemical equilibrium thermodynamically, according to Le Chatelier's principle.