• ETRI Journal
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• 제43권3호
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• pp.377-388
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• 2021

Owing to the difficulties associated with conducting millimeter-wave (mmWave) field measurements, especially in high-speed train (HST) environments, most propagation channels for mmWave HST have been studied using methods based on simulation rather than measurement. In this study, considering a linear cell layout in which base stations are installed along a railway, measurements were performed at 28 GHz with a speed up to 170 km/h in two prevalent HST scenarios: viaduct and tunnel scenarios. By observing the channel impulse responses, we could identify single- and double-bounced multipath components (MPCs) caused by railway static structures such as overhead line equipment. These MPCs affect the delay spread and Doppler characteristics significantly. Moreover, we observed distinct path loss behaviors for the two scenarios, although both are considered line-of-sight (LoS) scenarios. In the tunnel scenario, the path loss exponent (PLE) is 1.3 owing to the waveguide effect, which indicates that the path loss is almost constant with respect to distance. However, the LoS PLE in the viaduct scenario is 2.46, which is slightly higher than the free-space loss.

• 대한건축학회논문집:구조계
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• 제35권11호
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• pp.137-146
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• 2019

Recently, the Near-Surface-Mounting method using Fiber reinforced polymer (FRP) has been developed and applied to the reinforcement of many concrete structural members. However, as a part of the fire resistance design, there is a lack of research related to fire insulation for the areas reinforced with FRP. In case of NSM reinforcement, there is a difference in the transferred temperature from the external surface to the groove corresponding to the location of the groove where the FRP is embedded, and the effect of this should be reflected in the fireproof insulation design. Therefore, in this study, after forming grooves for surface embedding in concrete blocks, fireproof insulation reinforcement was performed using Calcium Silicate (CS) fireproof board and an experiment to evaluate the temperature transfer was performed. By observing the temperature at these groove positions, the reduction of temperature transfer according to fireproof insulation detail was studied. As a result, when the NSM-FRP is properly fire-insulated using the CS-based fireproof board, the epoxy inside the groove does not reach its glass transition temperature until the external temperature reaches $800^{\circ}C$.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.489-494
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• 2020

The Law method is observing the temporal bone. There are two types of methods: the double angle method, which manipulates the center ray angle of the tube twice, and the single angle method, which manipulates once. The purpose is to increase the reproducibility of the image by making vertical incidence by making an assistive device using a 3D printer. Two assistive devices with a wedge-shaped 8.5 × 10 × 2.3 cm, an inclined surface of 7.5 cm, and an inclination angle of 15° were fabricated. Assistive devices can be combined with each other in the form of grooves, and PLA (Poly Lactic Acid) is used as a material. In the first experiment, 10 examiners operated the tube 15° in the caudad direction and 15° in the anterior direction, and measured it with a protractor to conduct a reproducibility experiment. Second, two examiners acquired vertically incidence images using the existing law method and assistive devices, and measured the distance between each measurement point to evaluate the reproducibility. The tube center ray angle reproducibility experiment was not statistically significant, but the angle difference was up to 9° between examiners. The reproducibility experiment of radiographic images was not statistically significant with the conventional method, and the method using an assistive device was statistically significant. Therefore, regardless of skill level, an image capable of securing reproducibility, which is the advantage of vertical incidence, could be obtained.

• Journal of Astronomy and Space Sciences
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• 제38권1호
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• pp.45-53
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• 2021

GLONASS, a satellite navigation system developed in Russia since 1976, is defunct and orbits in an unstable attitude. The satellites in these problems are not managed and there is no precise information, which can increase the risk of collisions with other space objects. In this study, detailed attitude dynamic have to be analyzed through photometry data, which requires spin period and spin axis. The light curve data is obtained by observing through the photometer at the Graz station and the power spectrum is calculated to obtain the cycle of the satellite. The geometric relationship between observer and sun is analyzed for GLONASS-50 satellite. The box-wing model is applied to obtain the phase reflection of the satellite and obtain the Irradiation of the satellite through this information. In Light Curve and Irradiation, the spin axis is calculated for each peak points with the distance square minimum technique. The spin axis of the GLONASS-50 satellite is RA = 116°, Dec = 92°.

• 대한임베디드공학회논문지
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• 제18권4호
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• pp.185-194
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• 2023

Currently, drones are used in various fields such as transportation, agriculture and military. Especially, drones for military use are developed and utilized in many ways such as reconnaissance and bombing to minimize one's own damages. Nevertheless, they are developed as new weapons of modern types, so it is difficult to use them together with existing weapons. In this study, a drone program for effective bombing of mortar, which is often used in modern warfare, is developed. In mortar, a forward soldier comprehends the location of enemy for its distance and altitude, input them in data computer of launching angle, and applies the result value to cannon to launch. However, the existing method has low accuracy of bombing because observing shall be done within 1km from the target, and measuring accurate direction and velocity of the wind is difficult. Whereas, in the program of this study, the location of target, GPS, direction and velocity of the wind, and altitude are measured through drone. Each digit is used to calculate bombing specification for optimal bombing through the calculating formula of launching angle. In addition, when specifications are input in the program, the calculation is done automatically, so that it can be used in various mortars and shells. With the use of the program in this study, the location of enemy can be comprehended, and bombing specifications can be calculated quickly. It also enables the intensity of the wind to be applied for accurate bombing.

• 한국수소및신에너지학회논문집
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• 제33권2호
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• pp.158-163
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• 2022

The test method on the Type II high-pressure hydrogen storage tanks made of the metal wire hoop winding is a complex and high risk. Also closeup on the tank being test is difficult. In this study, we studied a mechanical test method for a high-pressure hydrogen tanks. This method must be simple, risk-free and possible to observe the change in microscopic behavior of a metal wire on a liner. As the results, it was possible to observe the microscopic behavior on the metal wire by the mechanical test method. Also, a simple and risk-free test was possible compared to the conventional test method for high pressure hydrogen tanks.

• 한국컴퓨터정보학회논문지
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• 제20권1호
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• pp.153-161
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• 2015

본 논문에서는 연속 촬영 이미지를 이용한 실험용 쥐의 운동 능력 평가 시스탬을 제안한다. 의학이나 수의학 분야에서는 인류의 양질의 삶을 위해 mouse를 이용한 동물실험을 실시하고 있다. 특히 실험용 쥐(mouse)를 이용한 실험 중에는 인위적인 부상(injury)을 만들고, 다양한 처치를 통하여 그 부상에서 회복되는 정도를 측정하는 실험을 많이 하고 있다. 이러한 실험에서 그 동안의 전통적인 운동량 측정 방법은 사람이 직접 관찰하는 방법으로 이루어지고 있었다. 제안한 시스템은 실험용 쥐에 대한 움직임을 정해진 단위 시간동안 연속 촬영을 실시하고, 이 연속 촬영된 이미지에서 mouse의 외곽선을 point cloud로 추출한다. 추출된 point cloud를 이용하여 mouse의 몸통에 대한 내부 외곽선(interior contour line)을 다시 추출한 후, 이를 이용하여 그 중심점을 구하고, 이들 중심점들을 연결하여 거리를 계산하여 누적함으로써 mouse가 단위 시간동안 이동한 총 거리를 자동 계산하도록 하는 시스템을 설계하고 구현한다.

• 대기
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• 제16권1호
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• pp.19-31
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• 2006

The purpose of this study is to develop the statistical model to predict sea level pressure of typhoon period in south coast of the Korean Peninsula. Seven typhoons, which struck south coast of the Korean Peninsula, are selected for this study, and the data for analysis include the central pressure and location of typhoon, and sea level pressure and location of 19 observing site. Models employed in this study are the first order regression, the second order regression and the neural network. The dependent variable of each model is a 3-hr interval sea level pressure at each station. The cause variables are the central pressure of typhoon, distance between typhoon center and observing site, and sea level pressure of 3 hrs before, whereas the indicative variable reveals whether it is before or after typhoon passing. The data are classified into two groups - one is the full data obtained during typhoon period and the other is the data that sea level pressure is less than 1000 hPa. The stepwise selection method is used in the regression model while the node number is selected in the neural network by the Schwarz's Bayesian Criterion. The performance of each model is compared in terms of the root-mean square error. It turns out that the neural network shows better performance than other models, and the case using the full data produces similar or better results than the case using the other data.

• 대한토목학회논문집
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• 제3권4호
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• pp.123-131
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• 1983

일반측량방법(一般測量方法)에 있어서, 높은 정도(精度)를 얻기 위해서는 오차요소(誤差要素)들을 최소한(最小限)으로 줄이는 것이 큰 과제(課題)이다. 또한 사진측량(寫眞測量)에서도 기준점측량(基準點測量) 성과(成果)는 결과(結果)값에 큰 영향(影響)을 주며, 촬영거리(撮影距離)가 먼 경우(境遇) 요구정도(要求精度)에 미치지 못하는 경우가 많다. 이에 본연구(本硏究)에서는 각관측(角觀測)과 사진측량이론(寫眞測量理論)을 조합(組合)함으로써, 오직 theodolite만의 각측정(角測定)으로 높은 정도(精度)의 삼차원(三次元) 좌표(座標)값을 얻을 수 있는 방법(方法)을 제시(提示)하였으며, 그 효용성(效用性)을 밝혔다. 본방법(本方法)의 주(主)된 장점(長點)은 오직 theodolite만이 측정(測定)을 위해 요구(要求)되며, 간단히 계산(計算)된다는 점(點)이다.

• 한국측량학회지
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• 제35권5호
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• pp.365-374
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• 2017

SAR (Synthetic Aperture Radar) is an effective tool for monitoring areas damaged by disasters. Full PolSAR (Polarimetric SAR) enhances SAR's capabilities by providing specific scattering mechanisms. Thus, full PolSAR data have been widely used to analyze the situation when disasters occur. To interpret full PolSAR data, model-based decomposition methods are frequently used due to its easy physical interpretation of PolSAR data and computational efficiency. However, these methods present problems. One of the key problems is the overestimation of the volume scattering component. To minimize the volume scattering component, the OA (Orientation Angle) compensation method is widely utilized. This paper shows that the effect of the OA compensation was analyzed over landslide affected areas. In this paper, the OA compensation is applied by using the OA estimated from the maximum relative Hellinger distance. We conducted an experiment using two full polarimetric ALOS/PALSAR (Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar)-2 data collected over Mocoa, Colombia which was seriously damaged by the 2017 Mocoa landslide. After OA compensation, the experimental results showed volume scattering power decreased, while the double-bounce and surface scattering power increased. Particularly, significant changes were noted in urban areas. In addition, after OA compensation, the separability of the double-bounce and surface scattering components are improved over the damaged building areas. Furthermore, changes in the OA can discriminate visually between the damaged building areas and undamaged areas. In conclusion, we demonstrated that the effect of OA compensation improved the influence of the double-bounce and surface scattering components, and OA changes can be useful for detecting damaged building areas.