• 제어로봇시스템학회논문지
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• 제13권4호
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• pp.315-319
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• 2007

A technique to model plasma processes was presented. This was accomplished by combining the backpropagation neural network (BPNN) and genetic algorithm (GA). Particularly, the GA was used to optimize five training factor effects by balancing the training and test errors. The technique was evaluated with the plasma etch data, characterized by a face-centered Box Wilson experiment. The etch outputs modeled include Al etch rate, AI selectivity, DC bias, and silica profile angle. Scanning electron microscope was used to quantify the etch outputs. For comparison, the etch outputs were modeled in a conventional fashion. GABPNN models demonstrated a considerable improvement of more than 25% for all etch outputs only but he DC bias. About 40% improvements were even achieved for the profile angle and AI etch rate. The improvements demonstrate that the presented technique is effective to improving BPNN prediction performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.339-341
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• 2006

This paper proposes a method of container position measurement using automatic landing system that is estimated by a laser range finder. In the most of container position measurement methods, CCD cameras or laser scanners have been used to get the source data. However those sensors are not only weak for disturbances, for examples, the light, fog, and rain, but also the system cost is high. When the spreader arrives the goal position, it is still swung by inertia or by wind effect. In this paper, the spreader swung data have been used to find the container position. The laser range finder is equipped in the front side of spreader. It can measure distance and relative position between spreader and container. This laser range finder can be rotated as desired by a motor. And a tilt sensor is equipped on the spreader to measure spreader sway. We estimate the relative position information between the spreader and a container using the laser range finder and tilt sensor through the geometrical analysis.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2002년도 춘계 학술대회논문집
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• pp.88-93
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• 2002

In the present research, a parametric study of aerodynamic characteristics for multi-element airfoils is performed. The major geometric parameters of interest are the gap distance between airfoils and relative deflection angle of slat/flap. The present results are mainly obtained by using inviscid flow calculation, and the aerodynamic characteristics are focused on the surface pressure distribution and the lifts. The results of the present research may be used as not only qualitative data but also quantitative data for small angle of attack flows, where the viscous effect does not play major role in terms of surface pressure distribution and lifts. A further research in this subject including viscous calculation and more geometric parameters is to be performed in the future.

• 한국전자파학회논문지
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• 제28권10호
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• pp.825-831
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• 2017

실제 레이다가 운용되는 환경에서 발생되는 클러터는 비균질성(heterogeneous)의 특성을 갖는 동시에 바이스태틱 레이다나 모노스태틱 non-sidelooking 레이다 구조인 경우는 클러터의 비정상성(nonstationary) 특성도 갖는다. 이러한 특성에 의해서 클러터 신호를 추정하는데 필요한 IID(Independent Identically Distributed) secondary 데이터 개수에 제약이 따르므로 클러터 억제 성능이 저하된다. 본 논문에서는 바이스태틱 레이다 환경에서 Cell under test에 대한 사전정보만을 이용하여 클러터 신호를 추정함으로써 secondary 데이터 없이 클러터를 억제하는 알고리즘을 제시한다. 바이스태틱 클러터의 angle-Doppler 스펙트럼 상에서 구조 분석을 통해 사전정보로 부터 클러터를 추정하는 것이 가능함을 보이고, 고유치 해석에 의해 클러터 억제 과정을 제시한다. 마지막으로 시뮬레이션을 통해 제시하는 클러터 억제 알고리즘의 성능을 보인다.

• 대한원격탐사학회지
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• 제22권2호
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• pp.111-121
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• 2006

분광각(Spectral Angle)을 이용한 분류는 같은 종류의 지표 대상물의 분광 특성이 대기 및 지형적인 영향으로 인해 원점을 기준으로 유사한 분광각을 가지며, 선형적인 분포 모양을 가진다는 가정에 기초한 분류 방식이다. 최근 분광각을 이용한 무감독 분류에 대한 연구가 활발히 이루어지고 있으나, 하이퍼스펙트럴 데이터의 특성을 반영한 효과적인 무감독 분류에 대한 연구는 미진한 상태이다 본 연구는 하이퍼스펙트럴 영상 분류에 있어서 기존 무감독 분광각 분류(USAC, Unsupervised Spectral Angle Classification) 연구에서 나타난 문제점들을 보완한 반복최적화 무감독 분광각 분류(ISOUSAC, Iterative Self-Organizing USAC) 기법을 제안하고 있다. 이를 위해, 무감독 분광각 분류에 적합한 각 분할(Angle Range Division) 기법을 적용하여 군집 초기 중심을 설정하였고, 군집 중심 계산에 있어서 각 중심을 이용하였다. 뿐만 아니라 병합(Merge)과 분할(Split)를 통한 유동적인 군집 분석을 수행하였다. 결과를 통해, 제안된 알고리즘이 기존의 기법보다 수행 시간뿐 아니라 시각적, 정량적인 면에서 우수한 결과를 도출하였으며, 분광각을 이용한 군집 유효성 지수(Validity Index)를 제안함으로써 기존의 무감독 분광각 분류와 정량적 비교를 수행하였다.

• 전기의세계
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• 제19권2호
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• pp.12-17
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• 1970

In the design of electrical equipment insulation, it is customary to place pressboard and other insulating material at right angle to the electrical discharge path, which is based on the insulation tests performed on equipment under various conditions such as types of insulation, applied voltage and other unique situations. Since electrical equipment manufacturing started only recently, there is a scarcity of available data on insulation problems, which make it difficult for the design engineers. The author untook this study to provide such analytical design data for various conditions based on the experiment conducted on the equipment being manufactured, thus reducing possible errors in the process.

• 수산해양교육연구
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• 제21권1호
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• pp.59-67
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• 2009

It is necessary for navigator to understand sufficiently maneuverabilities based on experiences and the data which were gotten from several tests of the ship when he maneuver his vessel. By the way most navigators used to rely on his experiences or feelings only maneuvering ship. But when he encounters situations he did not experience before he may be in difficulties. So navigator must get both experiences and data based on experimental results. In this paper author performs several tests such as turning test, Zig-zag test and spiral test to provide informations of maneuverabilities for navigators. The obtained results are as follows: There occurs almost no difference in size of the turning circle by the changes of ship's speeds. The scale of the turning circle was decreased exponentially when the rudder angle was increased. The maneuverabilities is better turning to starboard side than to port side. Maneuverabilities are more effective when the rudder is used to small angle than to large angle. As a result of spiral test course stability was comparatively seemed to be good.

• 제어로봇시스템학회논문지
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• 제18권3호
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• pp.243-250
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• 2012

This paper proposes a 3D map-building algorithm using one LRF (Laser Range Finder) while a mobile robot is navigating on the slanted surface. There are several researches on 3D map buildings using the LRF. However most of them are performing the map building only on the flat surface. While a mobile robot is moving on the slanted surface, the view angle of LRF is dynamically changing, which makes it very difficult to build the 3D map using encoder data. To cope with this dynamic change of the view angle in build 3D map, IMU and balance filters are fused to correct the unstable encoder data in this research. Through the real navigation experiments, it is verified that the fusion of multiple sensors are properly performed to correct the slope angle of the slanted surface. The effectiveness of the balance filter are also checked through the hill climbing navigations.

• Journal of Astronomy and Space Sciences
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• 제37권4호
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• 대한원격탐사학회지
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• 제38권1호
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• pp.111-126
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• 2022

Land use and land cover (LULC) mapping is an important factor in geospatial analysis. Although highly precise ground-based LULC monitoring is possible, it is time consuming and costly. Conversely, because the synthetic aperture radar (SAR) sensor is an all-weather sensor with high resolution, it could replace field-based LULC monitoring systems with low cost and less time requirement. Thus, LULC is one of the major areas in SAR applications. We developed a LULC model using only KOMPSAT-5 single co-polarized data and digital elevation model (DEM) data. Twelve HH-polarized images and 18 VV-polarized images were collected, and two HH-polarized images and four VV-polarized images were selected for the model testing. To train the LULC model, we applied the conditional generative adversarial network (cGAN) method. We used U-Net combined with the residual unit (ResUNet) model to generate the cGAN method. When analyzing the training history at 1732 epochs, the ResUNet model showed a maximum overall accuracy (OA) of 93.89 and a Kappa coefficient of 0.91. The model exhibited high performance in the test datasets with an OA greater than 90. The model accurately distinguished water body areas and showed lower accuracy in wetlands than in the other LULC types. The effect of the DEM on the accuracy of LULC was analyzed. When assessing the accuracy with respect to the incidence angle, owing to the radar shadow caused by the side-looking system of the SAR sensor, the OA tended to decrease as the incidence angle increased. This study is the first to use only KOMPSAT-5 single co-polarized data and deep learning methods to demonstrate the possibility of high-performance LULC monitoring. This study contributes to Earth surface monitoring and the development of deep learning approaches using the KOMPSAT-5 data.