• 한국자동차공학회논문집
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• 제13권2호
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• International Journal of Aeronautical and Space Sciences
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• 제7권1호
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• pp.106-117
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• 2006

The active vibration control of composite shell structure has been performed with the optimized sensor/actuator system. For the design of sensor/actuator system, a method based on finite element technique is developed. The nine-node Mindlin shell element has been used for modeling the integrated system of laminated composite shell with PVDF sensor/actuator. The distributed selective modal sensor/actuator system is established to prevent the effect of spillover. Electrode patterns and lamination angles of sensor/actuator are optimized using genetic algorithm. Continuous electrode patterns are discretized according to finite element mesh, and orientation angle is encoded into discrete values using binary string. Sensor is designed to minimize the observation spillover, and actuator is designed to minimize the system energy of the control modes under a given initial condition. Modal sensor/actuator for the first and the second mode vibration control of singly curved cantilevered composite shell structure are designed with the method developed on the finite element method and optimization. For verification, the experimental test of the active vibration control is performed for the composite shell structure. Discrete LQG method is used as a control law.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2006년도 학술대회
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• pp.307-312
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• 2006

Protection to the multimedia contents is inevitable to ensure that only authorized users be able to access the protected contents for consumption. Since protection mechanisms need to be designed efficiently by exploiting the type of the contents, we propose a protection scheme for the video bitstream encoded by Scalable Video Coding (SVC) technique. Our scheme exploits the property of SVC in which a video is encoded into spatial, temporal, and quality scalability layers. By applying our proposed protection scheme to the appropriate scalability layers we can effectively control the SVC contents completely or partially. Each layer can be flexibly protected with different encryption keys or even with different encryption algorithms. The algorithms that are used to protect each layer are described by the standardized protection description tool, which is the MPEG-21 Intellectual Property Management and Protection (IPMP) Components. In this paper, we present the design of the proposed layered SVC protection scheme, its implementation and experimental results. The experiment result shows that the proposed layered SVC protection scheme is very effective and can easily be applied.

• 인터넷정보학회논문지
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• 제18권6호
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• pp.15-23
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• 2017

Wireless power transmission (WPT) for wireless charging is currently attracting much attention as a promising approach to miniaturize batteries and increase the maximum total range of an electric vehicle. The main advantage of the laser power beam (LPB) approach is its high power transmission efficiency (PTE) over long distance. In this paper, we present the design of a laser power beam based WPT system, which has a best WPT channel selection technique at the receiver end when multiple power transmitters and single power receiver are operated simultaneously. The transmitters send their transmission channel information via optically modulated laser pulses. The receiver uses the received signal strength indicator and digitized data to choose an optimum power transmission path. We modeled a vertical multi-junction photovoltaic cell array, and conducted an experiment and simulation to test the feasibility of this system. From the experimental result, the standard deviation between the mathematical model and the measured values of normalized energy distribution is 0.0052. The error between the mathematical model and measured values are acceptable, thus the validity of the model is verified.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.113-115
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• 2001

In order to design the power appratus such ac bus bar, the current carrying ampacity should be determined, Since it is limited by maxium operating temperature, it is very important to predict temperature-rise on it. The main causes to raise temperature are joule's loss in the current carrying conductor and induced circulating and eddy current in the tank. The heat transfer is divided into convection and radiation on boundary, determining convection heat transfer coefficient is not easy. This paper propose a new technique that can be used to estimate the temperature rise in the extra high voltage bus bar. The heat transfer coefficient is analytically calculated by applying Nusselt Number depending on temperature as well as model geometry. The analytic method which use heat transfer coefficient is coupled with finite element method. The temperature distribution in the bus bar by the proposed method shows good agreement with experimental data.

• 설비공학논문집
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• 제20권2호
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• pp.144-153
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• 2008

A numerical analysis has been carried out to examine the flow characteristics and the collection efficiency for fine particles in a cyclone using Computational Fluid Dynamics (CFD) technique. The cyclone with the cylinder diameter of 60 mm has been considered for the investigation of the particle collection in a relatively smaller cyclone with somewhat higher inlet air velocities. Fundamental air flow patterns for different inlet velocities have been calculated and then the motions of particles of different sizes have been obtained. The calculated collection efficiencies for fine particles are compared with the experimental results, which shows a good agreement. The current result can be used for the design of cyclones with high collection efficiency.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.225-234
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• 2014

Wall-thinned defects caused by accelerated corrosion due to fluid flow in the inner pipe appear in many structures of the secondary systems in nuclear power plants (NPPs) and are a major factor in degrading the integrity of pipes. Wall-thinned defects need to be managed not only when the NPP is under maintenance but also when the NPP is in normal operation. To this end, a test technique was developed in this study to detect such wall-thinned defects based on the temperature difference on the surface of a hot pipe using infrared (IR) thermography and a cooling device. Finite element analysis (FEA) was conducted to examine the tendency and experimental conditions for the cooling experiment. Based on the FEA results, the equipment was configured before the cooling experiment was conducted. The IR camera was then used to detect defects in the inner pipe of the pipe specimen that had artificially induced defects. The IR thermography developed in this study is expected to help resolve the issues related to the limitations of non-destructive inspection techniques that are currently conducted for NPP secondary systems and is expected to be very useful on the NPPs site.

• Macromolecular Research
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• 제17권6호
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• pp.411-416
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• 2009

The color stabilization of antimicrobial blends was studied by using poly(hexamethylene guanidine) phosphate (PHMG) as a highly efficient biocidal and nontoxic agent. The Taguchi method was used to determine the optimum conditions for the blending of PHMG in polypropylene (PP) matrix. To improve the yellowing phenomena, two kinds of stabilizer were used together: tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)](IN1010) from phenol and tris(2,4-di-t-butylphenylphosphite) (IF168) from phosphorus. According to blend composition and mixing condition, six factors were chosen, with five levels being set for each factor. The orthogonal array was selected as the most suitable for fabricating the experimental design, L25, with 6 columns and 25 variations. The-smaller-the-better was used as an optimization criterion. The optimum conditions for these parameters were 10 phr for PHMG, 2 phr for IN1010, 1 phr for IF168, 10 min for mixing time, $210^{\circ}C$ for mixing temperature, and 30 rpm for rotation speed. Under these conditions, the yellowness index of the blend was 1.52. The processibility of the blends was investigated by Advanced Rheometric Expansion System (ARES). The blend with 0.5 w% PHMG content, diluted with PP, exhibited an antimicrobial characteristic in the shake flask method.

• 대한전자공학회논문지TC
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• 제45권2호
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• pp.83-91
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• 2008

전력선 통신을 이용한 MH(메탈핼라이드) 램프용 조광제어시스템을 구성하기 위하여, 전력선 모뎀 및 MH 램프용 전자식 안정기를 설계하고, 안정기가 전력선 채널에 미치는 영향을 분석하였다. 전력선이 통신채널로써 사용될시 채널의 특성은 부하에 의하여 변화하게 되므로, 부하는 전력선 통신에 적합하도록 설계되어야 한다. 따라서 본 논문에서는 전력선 통신에 적합한 전자식 안정기를 제안하고, ASK와 FSK 두 종류의 전력선 모뎀을 설계하여 맨체스터 코드와 DS/SS 방식을 각각 적용하였다. 실험결과, DS/SS 방식이 적용된 FSK 전력선 모뎀이 가장 우수한 특성을 갖는 것으로 확인 되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.961-966
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• 2000

It is difficult to change or remedy concrete structure after hardened. It is usual to evaluate the quality of hardened concrete using several test method. This study was performed to make fundamental data that could be used to evaluate the quality of hardened concrete. This study is to estimate mix proportion of hardened concrete. Each elements of concrete needed different estimation methods. First, the cement that handled by the most important compounds measured by XRF(X-ray fluorecence) machine with scanning Ca-K${\alpha}$. Second, the coarse aggregate that divided by maximum size measured by the area comparison method that starts from the assumption of uniform distribution. Third, the fine aggregate measured by the weight comparison method that needs several prerequsite constants which concerned cement hydration reaction. Fourth, the water content would be estimated by expert system that has data base of design data, the contents of above estimation results, the characteristics of concrete strength. As the result of the above research, some conclusions are as follows. The cement estimation method resulted by reliability of mean 96.7%, standard deviation 3.92. The area comparison method resulted by reliability of mean 95.3%, standard deviation 2.08. The weight comparison method resulted by reliability of mean 93.3%, standard deviation 3.35.