• 한국전기전자재료학회논문지
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• 제32권4호
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• pp.287-295
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• 2019

Privacy films are typically manufactured by combining black resin and transparent louver-shaped patterns. The use of black resin results in excellent light-shielding. However, black resin can reduce the transmittance of privacy films at the front viewing angle. In this study, we applied $SiO_2/SiON$ multi-layer thin films on a privacy film to maintain transmittance at the front viewing angle and improve light-shielding at the side viewing angle. We determined the optimum combination of thicknesses of the $SiO_2/SiON$ multi-layer stacks to increase the overall transmittance; the light shielding could be maximized at the side viewing angle.

• 한국전자파학회논문지
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• 제27권12호
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• pp.1036-1043
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• 2016

본 논문에서는 위상배열 안테나를 활용해 다중 경로 효과에 의한 공항정밀접근레이다의 고각 정확도 열화에 관하여 분석을 수행하였다. 공항의 활주로 주변에 설치되는 정밀접근레이다는 고정 환경인 활주로면의 영향을 지속적으로 받게 된다. 본 논문에서는 활주로면에 의한 다중 경로 효과에 따른 정밀접근레이다 고각 정확도 열화에 관하여, 배열 안테나의 합/차 패턴 분석 및 이를 통한 모노펄스 기울기를 계산하여 분석하였다. 또한, 본 논문에서는 이러한 고각 정확도 열화를 최소화하기 위해 모노펄스용 차 패턴을 고각 정확도 개선에 적합한 형태로 최적화하였다. 최종적으로 최적화된 배열 안테나 차 패턴을 적용한 후 지면 반사 영향성이 고려된 모노펄스 기울기를 계산하여 고각 정확도 개선 정도를 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.198-201
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• 2003

The multi-action forging process is one of developing directions of forging technologies. In this study, the multi-action die is designed and developed by the screws mechanism and the forging simulation is conducted by using plasticine to investigate the optimum conditions for the design of the screws. The results show the design variables are optimum when the diameter is 30 mm and the screw angle is $60^{\circ}$ for the upper screw rod and the outer diameter is 60 mm and the screw angle is $23.4^{\circ}$ for the lower screw tube. It makes the relative velocity between the upper punch and the die to be two to one, which is the expected condition. The material flow of the plasticine forgings is uniform. Therefore, it is feasible to use the screw set as the multi-action mechanism for controlling the movement of the multi-action forging die set.

• 제어로봇시스템학회논문지
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• 제16권3호
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• pp.233-238
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• 2010

This paper describes a multi-mobile robot system with fuzzy rule based structure in collision avoidance. Collision avoidance is an important function to perform a given task collaboratively and cooperatively in multi-mobile robot environments. So the important but challenging problem is handled in this paper. Considered obstacles for collision avoidance between multi mobile robots are static, dynamic, or both of them at the same time. Using the fuzzy rule based structure, distance and angle from a robot to obstacles are described as fuzzy linguistic values and steering angle for the robot are updated from the collision environments. As a result, the multi-mobile robot can modify a global path from a robot itself to its own target. In addition, avoiding collision with static or dynamic obstacles for the robot system can be achieved. Simulation based experimental results are given to show usefulness of this method.

• Steel and Composite Structures
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• 제36권1호
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• pp.87-101
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• 2020

A multi-scale epoxy/CNT/fiberglass annular sector plate is studied in this paper in the view of determining nonlinear forced vibration characteristics. A 3D Mori-Tanaka model is employed for evaluating multi-scale material properties. Thus, all of glass fibers are assumed to have uni-direction alignment and CNTs have random diffusion. The geometry of annular sector plate can be described based on the open angle and the value of inner/outer radius. In order to solve governing equations and derive exact forced vibration curves for the multi-scale annular sector, Jacobi elliptic functions are used. Obtained results demonstrate the significance of CNT distribution, geometric nonlinearity, applied force, fiberglass volume, open angle and fiber directions on forced vibration characteristics of multi-scale annular sector plates.

• International Journal of Fluid Machinery and Systems
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• 제3권2호
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• pp.150-159
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• 2010

Laidback fan shaped film-cooling hole is formulated numerically and optimized with the help of three-dimensional numerical analysis, surrogate methods, and the multi-objective evolutionary algorithm. As Pareto optimal front produces a set of optimal solutions, the trends of objective functions with design variables are predicted by hybrid multi-objective evolutionary algorithm. The problem is defined by four geometric design variables, the injection angle of the hole, the lateral expansion angle of the diffuser, the forward expansion angle of the hole, and the ratio of the length to the diameter of the hole, to maximize the film-cooling effectiveness compromising with the aerodynamic loss. The objective function values are numerically evaluated through Reynolds- averaged Navier-Stokes analysis at the designs that are selected through the Latin hypercube sampling method. Using these numerical simulation results, the Response Surface Approximation model are constructed for each objective function and a hybrid multi-objective evolutionary algorithm is applied to obtain the Pareto optimal front. The clustered points from Pareto optimal front were evaluated by flow analysis. These designs give enhanced objective function values in comparison with the experimental designs.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1178-1183
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• 2008

This paper is about a study of atomizing characteristics of a Multi-Nozzle, which is an important part in a flooding water mist system for extinguishing fires broke out in ships. Comparing the results of experiments for the Single-Nozzle to that of numerical analyses, characteristics of a Multi-Nozzle can be found out. In situation of a Single-Nozzle’s, the atomizing angle was $34^{\circ}$. And in situation of Multi-Nozzle that combined with 5 single-nozzles, the atomizing angle increase to $125^{\circ}$. The effective area is 3.7 times of the former. The quality factor will reduce, if the diameter of the atomizing region of the nozzle reduces. Although the atomizing angle is reduced because of the atomizing property, the value of SMD still shows a good result.

• 한국분무공학회지
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• 제16권4호
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• pp.201-209
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• 2011

Optimum engine performance is obtained when the spray characteristics is well matched to the geometry of a combustion chamber. Among many parameters governing the combustion performance in internal combustion engine, fuel supply characteristics and atomization are important performance factors. Therefore, spray characteristics of high pressure multi-hole injector has been studied experimentally. An experimental test system has been made to operate high pressure injection system and to visualize spray behavior. Spray visualization has been performed to analyze spray formation, spray cone angle, bent angle and penetration length. Spray interaction with piston has been analyzed with various injector installation angle, injection pressure and ambient pressure. Test results show that penetration length is greatly influenced by the injection pressure. Penetration length is decreased as ambient pressure increased. Spray cone angle is increased as injection pressure and ambient pressure increased. However, bent angle is not influenced by the change of injection pressure and ambient pressure. Spray cone angle distribution map is plotted using the experimental data. Fuel movement around the spark-plug has been enforced as increasing injector installation angle.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 춘계학술대회 논문집(Proceeding of the KOSME 2000 Spring Annual Meeting)
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• pp.153-158
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• 2000

Flow visualization and PIV measurements were conducted to investigate the flow characteristics of multi-channel with inclination angle. The water flow seeded with tiny vegetable powder as tracers revealed details of flow field. The PIV measurement to acquire multi-point velocity data simulatneously was carried out at three space of plates for 5, 10, and 15mm with variation of inlet flow rates of $0.25m^3/h$ and <$0.5m^3/h.$ Experiment results show that space of plates acts a significant role in separating process.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.170-173
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• 2004

When the data from the artificial satellite is analyzed, recent years it is perceived to vegetation index using BRF(Bi-directional Reflectance Factor) of the observation target. To make the BRF models, it is important to measure the 3D structure of the observation target actually. In this study, it is proposed to the observation technique by using multi-angle stereo pair image, and shown the observation result in grassland area. Also, our team has been operating the radio controlled helicopter which can fly over the tall forest canopy and it can be equipped the measurement system.