• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제25회 KOSCI SYMPOSIUM 논문집
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• pp.173-184
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• 2002

In order to evaluate the devolatilization models of pulverized coal, various devolatilization models are examined for the numerical analysis of Drop Tube Furnace.The results of analysis are compared with the experimental results. A numerical study was conducted to explore the sensitivities of the predictions to variation of the model parameters. It helps to elucidate the source of the discrepancies. Three different wall temperature conditions of the DTF, 1100, 1300 and $1500^{\circ}C$ were considered in this analysis. Two fuels are U.S.A. Alaska coal and Australia Drayton coal. The results of analysis with constant rate model, single kinetic rate model and two competing rate modes well presented fast volatile matter release in the early devolatilization. However, in the latter devolatilization they did not coincide with experimental results which presented tardy volatile matter release on account of pyrolysis of high molecular substance. On the other hand, the results of analysis with DAEM(Distribute Activation Energy Model) coincided with experiment al results in overall devolatilization.

• 한국자동차공학회논문집
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• 제19권6호
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• pp.76-81
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• 2011

Fossil fuel, the energy source of internal combustion engine automobiles, is limited in resource and has caused environmental issues for decades. Accordingly, automobile manufacturers from many countries around the world are developing or producing eco-friendly vehicles that utilize alternative sources of energy. These vehicles are equipped with many electronic and electrical components which operate on high voltage and/or large current that were not used in conventional combustion engine automobiles. In this paper, in order to analyze the electro-magnetic interference noise, electric vehicles and fuel cell electric vehicles are tested under the guidelines of KMVSS (Korean Motor Vehicle Safety Standards) as well as under test modes that are not stipulated under the guidelines.

• 한국항공우주학회지
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• 제34권8호
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• pp.79-86
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• 2006

액체로켓엔진에서 고주파 연소불안정을 제어하기 위하여 인젝터 길이 변화를 줄 수 있는 백홀 스월 인젝터를 분석하였다. 음향흡수자로서 백홀 인젝터의 효과를 분석하기위하여 백홀 인젝터는 1/4 파장 공명기로 해석하였다. 이론적 접근과 음향 실험의 결과로부터 가변적 변위를 갖는 백홀 스월 인젝터가 연소실의 불안정 모드를 감소시킴을 알 수 있었다. 실험적으로 감쇠율을 측정하여 감쇠효과를 측정하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.679-686
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• 2008

There has been an increasing demand of introducing innovative public transport modes meriting high flexibilities of a bus mode along with on-time accuracy and quality environment-friendliness of a rail mode, as it is considered to significantly contribute to reducing huge social expenditures on the traffic congestion and environmental pollution agenda, and to be an alternative solution to better the urban transport problems. In order to comply with the need, Seoul Municipal Government has recently decided to build up GRT system of a new concept in Nangok area in Seoul, the first in its kind in Korea. The concession has been awarded to Seoul Metro. This thesis will study and benchmark similar systems abroad under operation, and further review necessary requirements overall which would secure full readiness for the operation of Nangok GRT system.

• 대한금속재료학회지
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• 제49권10호
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• pp.754-759
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• 2011

In this study, the interlaminar fracture behaviors of laminated GFRP composites were investigated, and the results could be used for damage tolerance design based on fracture mechanics. Three types of laminated GFRP composites that can be used as high voltage insulating materials in magnet systems were fabricated in order to study the interlaminar fracture behavior according to the molding process. The values of interlaminar fracture toughness for the VPI, prepreg, and HPL laminate were $1.9MPa{\cdot}^{1/2}$, $1.7MPa{\cdot}^{1/2}$, and $2.2MPa{\cdot}^{1/2}$, respectively. HPL laminate showed the best fracture resistance. The failure modes of HPL and VPI were similar to that of an adhesive joint, and prepreg laminates showed partial cohesive failure mode due to internal voids.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.155-164
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• 2004

In order for studying pressure-coupled dynamic responses of droplet vaporization, open-loop experiment of an isolated droplet vaporization exposed to pressure perturbations in stagnant gaseous environment is numerically conducted, Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous nitrogen. Results show that wave instability in view of pressure-coupled vaporization response seems more susceptible at higher pressures and higher wave frequencies. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Augmentation of perturbation frequency also enhances amplification due to the reduction of phase differences between pressure perturbation and surface temperature fluctuation.

• Geomechanics and Engineering
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• 제33권5호
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• pp.427-437
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• 2023

The objective of this work is to study the wave propagation of an FGM plate via a new integral inverse shear model with temperature-dependent material properties. In this contribution, a new model based on a high-order theory field of displacement is included by introducing indeterminate integral variables and inverse co-tangential functions for the presentation of shear stress. The temperature-dependent properties of the FGM plate are assumed mixture of metal and ceramic, and its properties change by the power functions of the thickness of the plate. By applying Hamilton's principle, general formulas of wave propagation were obtained to plot the phase velocity curves and wave modes of the FGM plate with simply supported edges. The effects of the temperature and volume fraction by distributions on wave propagation of the FGM plate are investigated in detail. The results of the dispersion and the phase velocity curves of the propagation wave in the functionally graded plate are compared with previous research.

• 한국정밀공학회지
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• 제10권4호
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• pp.163-169
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• 1993

A flexible manipulator can move in the high speed even with the small driving torque. The dymanic equations of flexible manipulator which include 2 vibrational modes are derived using the clamped-free boundary condition. Simulation results of the 6th order model are well matched with experimental results. The hub angle of the flexible mainpulator can be controlled without vibration of the beam by the feedback of both hub angle and strain. The overshoot of the hub angle in the step response is reduced without sacrificing the rise time using the cycloidal function instead of the step function as the referenmce input.

• 방송공학회논문지
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• 제13권4호
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• pp.501-515
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• 2008

최근에 고품질 이동 멀티미디어 서비스에 대한 사용자의 요구가 증대되고, 계층 변조 전송 기법을 통하여 추가적인 전송 대역폭을 확보할 수 있게 됨에 따라 스케일러블 비디오 부호화(Scalable Video Coding)를 이용하여 기존의 T-DMB(Terrestrial DMB)의 화질을 개선한 고품질 지상파 DMB(Advanced Terrestrial DMB) 서비스를 제공하기 위한 연구가 활발히 진행되고 있다. 그러나 T-DMB와 AT-DMB의 호환적인 서비스를 지원하는 SVC 계층 부호기는 매우 복잡한 구조를 갖게 되므로, 조기 서비스 도입을 위하여 부호기의 복잡도 감소에 대한 연구가 요구된다. 본 논문에서는 기존의 T-DMB와 호환성을 갖는 공간 확장성 SVC 부호기에서 매크로블록 계층의 부호화 모드 제한을 통한 고속 부호화 모드 결정 기법을 제안한다. 제안된 기법은 매크로블록 계층의 부호화 모드 결정 함수의 구조 분석을 통한 기저 계층과 향상 계층, 그리고 계층 간에 사용되는 부호화 모드의 통계적 특성에 기초한다. 모의실험을 통하여, 제안된 기법이 우수한 성능을 유지하면서, 수행시간을 크게 단축시킬 수 있는 호환적인 부호기를 얻을 수 있음을 보인다.

• Journal of Power Electronics
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• 제15권5호
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• pp.1329-1337
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• 2015

By placing distributed generation power sources beside a big nonlinear load, these sources can be used as a power quality enhancer, while injecting some active power to the network. In this paper, a new scheme to use the distributed generation power source in both operation modes is presented. In this scheme, a fuzzy controller is added to adjust the optimal set point of inverter between compensating mode and maximum active power injection mode, which works based on the harmonic content of the nonlinear load. As the high order current harmonics can be easily rejected using passive filters, the DG is used to compensate the low order harmonics of the load current. Multilevel transformerless cascade inverters are preferred in such utilization, as they have more flexibility in current/voltage waveform. The proposed scheme is simulated in MATLAB/SIMULINK to evaluate the circuit performance. Then, a 1kw single phase prototype of the circuit is used for experimental evaluation of the paper. Both simulative and experimental results prove that such a circuit can inject a well-controlled current with desired harmonics and THD, while having a smaller switching frequency and better efficiency, related to previous 3-phase inverter schemes in the literature.