• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.1013-1018
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• 2003

This paper deals with the secondary excited induction generator applied to random energy input generation system. As it is preferred to stabilize the output voltage and frequency in the constant level, microcomputer controlled inverter connected to the secondary windings supplies the secondary current with slip frequency. For testing the appropriateness of this paper, the input torque simulator, which generate the statistically varied wave power input torque in the laboratory to drive the secondary excited induction generator, are constructed. The experimental and numerical results show the advantage of secondary excited induction generator system for the random input wave generation system.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.4
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• pp.403-413
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• 2007

As rock bolts become one of the main support systems in tunnels and underground structures, the integrity of the rock bolts affects the safety of these types of structures. The purpose of this study is the evaluation of rock bolt integrity using Fourier and wavelet transforms of the guided ultrasonic waves. After five rock bolt specimens with various defect ratios are embedded into a large scale concrete block, guided waves are generated by a PZT (lead zirconate titanate) element and measured by an acoustic emission (AE) sensor. The captured signals are analyzed in the frequency domain using the Fourier transform, and in the time-frequency domain using the wavelet transform based on a Gabor wavelet. The spectrum obtained from the Fourier transform shows that a portion of high frequency contents increases with increase in the defect ratio. Peak values in the time-frequency domain represent the interval of travel time of each echo. The energy velocities of the guided waves increase with the defect ratio. This study shows that the spectrum ratio and the energy velocity may be indicators fur the evaluation of rock bolt integrity.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.2
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• pp.1-13
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• 2012

Seismic fragility functions are derived for probabilistic evaluation of seismic control performance of energy dissipation devices installed in reinforced concrete structures. Displacement-dependent dampers are added to the nonlinear single-degree-of-freedom systems with different natural periods and hysteretic characteristics of which stiffness and strength has uncertainty. Nonlinear time history analysis is conducted for those SDOF systems and the result is processed statistically to obtain seismic fragility functions in the form of log normal distribution. Variation of seismic fragility functions for different parameters of SDOF systems and dampers are investigated and the seismic control performance is assessed probabilistically.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.120-123
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• 2009

건물에서 에너지손실이 큰 창호에 대해 최저소비효율기준 및 에너지소비효율 등급기준(안) 도입을 통해 지속가능한 고효율 창호의 보급 활성화 촉진과 관련 산업의 기술 및 산업력 향상을 적극적으로 유도할 필요가 있다. 이에 본 연구에서는 창호의 에너지 효율화를 위하여 고효율기자재(고기밀성 단열창호)로 인증받은 약 100여개 제품과 기타 제품에 대하여 창호 유형별 기밀 및 단열성능의 조사 분석을 통하여 창호 관련 제도 개정에 기초자료로 활용 에너지절약과 기후변화협약 관련 건물부문의 구체적 실천 대응방안으로 활용하고자 한다.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.121-129
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• 2010

Through this paper, we studied on the basic concept of vibration-induced power generation for urban infrastructures. Since the travelling of automobiles on the bridge cause vibration, it is possible to convert the vibration energy into green-electric energy by utilizing magnetic induction technology. In this paper we define the concept of green-bridge vibration power generation system which contains the concept of magnetic induction technology and propose a vibration power generation device for converting the bridge vibration energy into the electric energy. Also, an experiment was held by applying the vibration power generator on a real bridge. The results showed the applicability and effectiveness of the vibration power generator.

• Journal of Internet Computing and Services
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• v.17 no.2
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• pp.11-17
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• 2016

In this paper, the optimum weight of the algorithm based on the cross information-potential with the delta functions (CIPD) is derived and its robustness against impulsive noise is studied. From the analysis of the behavior of optimum weight, it is revealed that the magnitude controlling operation for input plays the main role of keeping optimum weight of CIPD stable from the impulsive noise. The simulation results show that the steady state weight of CIPD is equivalent to that of MSE criterion. Also in the simulation environment of impulsive noise, unlike the LMS algorithm based on MSE, the steady state weight of CIPD is shown to be kept stable.

• Computational Structural Engineering
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• v.11 no.1
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• pp.191-204
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• 1998

The general formulation for free vibration and stability analysis of unsymmetric thin-wared space frames is presented in case where the shear deformation effects are neglected. The kinetic and total potential energies are derived by applying the extended virtual work principle, introducing displacement parameters defined at the arbitrarily chosen axis and including warping deformation and second order terms of finite semitangential rotations. In formulating the finite element procedure, cubic Hermitian polynomials are utilized as shape functions of the two node space frame element. Mass, elastic stiffness, and geometric stiffness matrices for the unsymmetric thin-walled section are evaluated, and load-correction stiffness matrices for off-axis distributed loadings are considered. In order to illustrate the accuracy and practical usefulness of this formulation, finite element solutions for the free vibration and stability problems of thin-walled beam-columns and space frames are presented and compared with available solutions.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.2267-2268
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• 2008

에너지 문제가 국제적인 이슈로 떠오르고 있는 가운데 열에너지와 전기에너지 사이의 에너지 변환 현상, 즉 열전효과를 이용한 열전발전은 최근 여러 국가에서 연구가 활발히 진행 중이다. 경사기능성 재료(FGM)란 기존의 물질들에 경사적인 특성 변화를 주어 새로운 물질로 탄생시킨 개념으로, 이 논문에서는 그동안 발표된 열전변환재료들의 열전변환특성을 이용하여 경사기능성재료를 구성하여 보았다. 또한 구성한 경사기능성재료와 단일재료를 이용하여 기본적인 열전발전회로에 적용시켜, 변환효율을 계산하여 보았다. 시뮬레이션 결과를 이용하여 경사기능성 열전변환재료와 단일 물질의 변환 효율을 비교하였으며, 경사기능성 열전변환재료가 단일 열전변환재료보다 뛰어난 성능을 갖고 있음을 유도하였다.

• Membrane Journal
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• v.32 no.6
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• pp.411-426
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• 2022

Energy plays a significant role in modern lifestyle because of our extensive reliance over energy-operating devices. Therefore, there is a need for alternative and green energy resources that can fulfill the energy demand. For this, fuel cell (FCs) especially anion exchange membrane fuel cells (AEMFCs) have gained tremendous attention over the other (FCs) due to their fast reaction kinetics without using noble catalyst and allow to use of cheaper polymers with high performance. But lack of highly conductive, chemically, and mechanically stable anion exchange membrane (AEM) still main obstacle to the development of high performance AEMFCs. Therefore, graphene-based polymer composite membranes came into the existence as AEMs for the FCs. The exceptional properties of the graphene help to improve the performance of AEMs. Still, there are lot of challenges in the graphene derivatives based AEMs because of their high tendency of agglomeration in polymer matrix which reduced their potential. To overcome this issue surface modification of graphene derivatives is necessary to restrict their agglomeration and conserved their potential features that can help to improve the performance of AEM. Therefore, this review focus on the surface modification of graphene derivatives and their role in the fabrication of AEMs for the FCs.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.48-54
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• 2002

This paper is described the indirect induction heated boiler and induction heated hot air producer using the voltage-fed series resonant high-frequency inverter which can operate in the frequency range from 20 kHz to 50 kHz. A specially designed induction heater is composed of laminated stainless plates, which have many tiny holes and are interconnected by spot welding. This heater is inserted into the ceramic type vessel with external working coil. This working coil is connected to the inverter and turbulence fluid through this induction heater to moving fluid generates in the vessel. The operating performances of this unique appliance in next generation and its effectiveness are evaluated and discussed from a practical point of view.