• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.343-348
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• 1986

An optical interference method was developed for measuring rapidly growing and evaporating liquid condensate films (e.g., Na$_{2}$SO$_{4}$, $K_{2}$SO$_{4}$) on solid surface exposed to flowing combustion product gases at film thicknesses well below the onset of complications due to run-off. To develop this optical system, this study investigated the optical parameters (e.g., polarization state, incident angle, target roughness, etc.) Trends for the Na$_{2}$SO$_{4}$(l) and $K_{2}$SO$_{4}$(l) deposition rates as a function of target temperature using this optical measuring system agree with the theoretical prediction of the vapor deposition. This study was able to extend the experimental range for vapor plus condensed phase transport and deposition. While previously unable to measure the evaporation rates interferometrically, these rates are estimated from the results of the investigation of polarization states.

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.5
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• pp.35-45
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• 1981

An asymptotic solution of electromagnetic waves scattered by a right-angled dielectric wedge for plane wave incidence is obtained. Scattered fields are constructed by waves reflected and refracted from dielectric interfaces (geometric-optical fields) and a cylindrical wave diffracted from the edge. The edge diffracted field is obtained by adding a correction to the edge diffraction of physical optics approximation, where the correction field is calculated by solving a dual series equation amenable to simple numerical calculation. Validity of this result is assured by two limits of relative dielectric constant $\varepsilon$ of the wedge. The total asymptotic field calculated results in a Rawlins' Neumann series solution for small $\varepsilon$, and the edge diffraction pattern is shown to approach that of a perfectly conducting wedge for large $\varepsilon$. Calculated field patterns are presented and the accuracy of physical optics approximation is discussed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.4
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• pp.153-159
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• 2011

The MUSIC (MUltiple SIgnal Classification) method estimates the directions of arrival (DOAs) of the signals impinging on a sensor array based on the fact that the noise subspace is orthogonal to the signal subspace. In the conventional MUSIC, an estimate of the basis for the noise subspace is obtained by eigendecomposing the sample matrix, which is computationally expensive. In this paper, we present a simple DOA estimation method which finds an estimate of the signal subspace basis directly from the columns of the sample matrix from which the noise power components are removed. DOA estimates are obtained by searching for minimum points of a cost function which is defined using the estimated signal subspace basis. The minimum points are efficiently found through the Brent method which employs parabolic interpolation. Simulation shows that the simple estimation method virtually has the same performance as the complex conventional method based on the eigendecomposition.

• Journal of Broadcast Engineering
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• v.25 no.4
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• pp.598-608
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• 2020

In this paper, we propose a color correction technique for images acquired through a multi-view camera system for acquiring a 3D model. It is assumed that the 3D volume is captured indoors, and the position and intensity of the light is constant over time. 8 multi-view cameras are used, and converging toward the center of the space, so even if the lighting is constant, the intensity and angle of light entering each camera may be different. Therefore, a color optimization function is applied to a color correction chart taken from all cameras, and a color conversion matrix defining a relationship between the obtained 8 images is calculated. Using this, the images of all cameras are corrected based on the standard color correction chart. This paper proposed a color correction method to minimize the color difference between cameras when acquiring an image using 8 cameras of 3D objects, and experimentally proved that the color difference between images is reduced when it is restored to a 3D image.

• Journal of the Korean Society of Marine Environment & Safety
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• v.10 no.1 s.20
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• pp.1-7
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• 2004

RADARSAT is one of many possible data sources that can play an important role in marine surveillance including ship detection because radar sensors have the two primary advantages: all-weather and day or night imaging. However, atmospheric effects on SAR imaging can not be bypassed and any remote sensing image has various geometric distortions, In this study, radiometric and geometric calibrations for RADARSAT/SAT data are tried using SGX products georeferenced as level 1. Even comparison of the near vs. far range sections of the same images requires such calibration Radiometric calibration is performed by compensating for effects of local illuminated area and incidence angle on the local backscatter, Conversion method of the pixel DNs to beta nought and sigma nought is also investigated. Finally, automatic geometric calibration based on the 4 pixels from the header file is compared to a marine chart. The errors for latitude and longitude directions are 300m and 260m, respectively. It can be concluded that the error extent is acceptable for an application to open sea and can be calibrated using a ground control point.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.12
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• pp.59-67
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• 1998

In this paper, a rigorous three-dimensional Monte Carlo approach to simulate the sputter yield as a function of the incident ion energy and the incident angle as well as the atomic ejection distribution of the target is presented. The sputter yield of the target atom (Cu, Al) has been calculated for the different species of the incident atoms with the incident energy range of 10 eV ~ 100 KeV, which coincides with the previously reported experimental results. According to the simulation results, the calculated sputter yield tends to increase with the amount of the energy of the incident atoms. Our simulation revealed that the maximum sputter yield can be obtained for the incident atom with 10 KeV for the heavy ion, while the maximum sputter yield for the light ion is for the incident atoms with an energy less than 1 KeV. The sputter yield increases with angle of incidence and seems to have the maximum value at 68$^{\circ}$. For angular distributions of the sputtered particle, the atoms in the direction normal to the surface increase with angle of incidence. Furthermore, we has conducted the parallel computation on CRAY T3E supercomputer and built a GUI(Graphic User Interface) system running the sputter simulator.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.607-614
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• 2023

Clear overlapping of the bilateral epicondyle and proper separation of the elbow joint are crucial for obtaining accurate lateral general radiographs of the elbow. However, due to the complex anatomical structure of the elbow, achieving optimal positioning is challenging, leading to the need for repeated x-ray examinations. Therefore, the purpose of this study was to investigate the angle of the forearm in patients where accurate lateral images of the elbow joint can't be obtained after vertical incidence using a styrofoam device during elbow joint lateral x-ray imaging. Twenty patients were enrolled in our study following the established protocol. First, a vertical x-ray at an angle of 0° between the forearm and the table was taken (control group). Here, if the lateral image of the elbow joint was deemed inadequate, the forearm angle was adjusted using custom-made styrofoam supports with 5° and 10° inclinations (experimental groups). For the evaluation method, two assessors utilized a 5-point Likert scale to assess the images. The reliability of the assessments was analyzed using Cronbach's alpha coefficient. As a result, patients with inadequate overlap of the bilateral epicondyle and separation of the elbow joint in the initial examination (control group) were able to obtain the best images when setting a 10° angle between the forearm and the table. The subjective evaluation was 1.6 ± 0.8 points at 0°, 2.7 ± 0.8 points at 5°, and 4.4 ± 1.3 points at 10°, respectively. The reliability analysis for the angles of 0°, 5°, and 10° yielded Cronbach's alpha values of 0.867, 0.697, and 0.922, respectively. In conclusion, when it is not possible to obtain accurate images using the conventional position and X-ray beam direction, it is considered that by initially acquiring images with an angle of 10° between the forearm and the table, and gradually decreasing the angle while obtaining images, it would be possible to achieve the optimal image while reducing the number of repeat examinations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.1
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• pp.11-21
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• 2020

This paper deals with the impact of a GNSS (Global Navigation Satellite System) antenna radome on the PCV (Phase Center Variations) and the estimated kinematic coordinates. For the Trimble and Leica antennas, specially set up CORS (Continuously Operation Reference Stations) in Korea, the PCC (Phase Center Corrections) were calculated and compared for NONE, SCIS, SCIT, and TZGD radome from the PCV model published by the IGS (International GNSS Services). The results revealed that the PCC differences compared to the NONE were limited to about 1mm in the horizontal component while those of the vertical direction ranged from a few millimeters to a maximum of 7mm. Among the radomes of which PCV were compared, the SCIT had the most significant influence on the vertical component, and its GPS (Global Positioning System) L2 and L2 PCC (Phase Center Corrections) had opposite direction. As a result of comparing the kinematic coordinates estimated by the baseline processing of 7 CORSs with an application of the PCV models of the various radomes, the SCIS which was actually installed at CORS in Korea showed 3.4mm bias, the most substantial impact on the ellipsoidal height estimation whereas the SCIT model resulted in relatively small biases.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.198-198
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• 2015

전기변색재료는 전압을 인가하였을 때 전계방향에 따라 가역적으로 색이 변화하는 재료를 말한다. 스마트윈도우용 전기 변색재료는 지속적으로 전기를 가해줄 필요 없이 한번 변색되면 색이 지속되는 특징을 가지므로 에너지 효율적으로 우수하여 태양열 차단 창호나 디스플레이 분야에 응용될 것으로 기대된다. 이러한 전기 변색재료에는 산화형 전기 변색 재료, 환원형 전기 변색 재료가 있는데 이중 가장 널리 연구되고 있는 재료는 환원형 전기변색재료이다. 대표적인 재료로 $WO_3$가 쓰이는 데 이는 전기 변색적 특성이 우수하고 또한 내구성이 다른 재료에 비해 우수하다는 장점 때문이다. 그러나, 상용화를 위해서는 내구성의 개선이 요구되고 있다. 한편, $TiO_2$는 안정성이 매우 뛰어나지만 전기변색적 특성이 $WO_3$에 비해 낮은 점이 지적되고 있다. 이러한 $WO_3$ 및 $TiO_2$ 박막은 스퍼터링 또는 sol-gel법 등으로 제작되고 있는데, 일반적으로 스퍼터링의 경우 치밀한 박막이 형성되기 때문에 Porous 한 박막을 얻기 힘들다. 따라서 본 연구에서는 기판에 입사하는 스퍼터 입자들의 각도를 조절하여 shadowing 효과로 인해 박막의 구조가 porous해지는 Glancing angle deposition을 도입하였다. 이러한 증착법을 이용하여 $WO_3$와 $TiO_2$를 각도를 조절하여 증착하고 $TiO_2$와 $WO_3$ 박막의 특성을 비교하여 본다. 두께 300 nm를 가지는 $WO_3$ 및 $TiO_2$ 박막은 GLAD RF 마그네트론 스퍼터링법을 이용하여 Corning glass(corning E-2000)기판 위에 증착하였다. 기판 입사 각도는 $0^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$로 증착하였고 직경 3 in의 $TiO_2$, $WO_3$ 타겟을 사용하였다. 또한 스퍼터링 파워는 400 W, 작업압력 1.0 Pa, 그리고 스퍼터링 가스는 O2/Ar+O2 유량 10%에서 30%로 증착을 상온에서 진행하였다. 전기화학적 특성을 평가하기 위하여 $TiO_2$ 및 $WO_3$ 박막을 100 nm 두께의 ITO/glass 위에서 증착하였다. 박막의 미세구조는 XRD와 SEM을 통해 확인하였고, 전기화학적 특성은 Ar 분위기의 Glove box안에서 parstat 2273을 통해 측정하였다. 전해질은 1 M $LiPF_6/PC$로 진행하였고, 대향 전극는 Pt전극을, 참고 전극은 칼로멜 전극을 사용하였다. Potential 범위는 2 V에서 4 V로 진행하였고, scan rate는 50 mV/s로 측정하였다. 투과도는 UV/VIS spectrometer로 측정하였다. 전기변색 특성의 상관관계 및 에 대해서는 학회 당일 발표할 예정이다.

• The Journal of the Korea Contents Association
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• v.19 no.4
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• pp.368-380
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• 2019

This study proposes a method to evaluate the performance of a detector by analyzing the dynamic step wedge and histogram according to the change of the tube voltage and sensitivity when using the Automatic Exposure Control (AEC). The performance of a detector was evaluated by measuring X-ray quality, Entrance Surface Dose (ESD), tube current, dynamic range corresponding to detector sensitivities of S200, S400, S800, S1000 per tube voltage of 60, 70, 81, 90 kVp. As a results, all of the qualities satisfied the acceptance criteria, and the Entrance Surface Dose and tube current were decreased stage by stage as sensitivity was set higher. In the dynamic step wedge, the observable dynamic range has also increased as tube voltage became higher. The histogram showed the quantization separation phenomena as the tube voltage was set higher. The higher the sensitivity, the more the underflow and overflow occurred in which the amount of information on both ends of the histogram was lost. In conclusion, the deterioration in the performance of the detector was found to be insufficient to realize the change of the tube voltage and sensitivity when using the Automatic Exposure Control, and it is useful to use dynamic step wedge and histogram in evaluating detector performance evaluation.