• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.270.2-270.2
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• 2013

직선운동하는 하전입자의 진행방향에 수직한 평면상에 서로 직교하는 전기장과 자기장을 걸어주면, 하전입자에는 전기장에 의한 힘 FE와 자기장과 속도 v에 의한 로렌츠력 $F_B=q(v{\times}B)$가 동시에 작용하게 된다. 이때 Wien 조건 FB=-FE를 만족하는 질량 mA과, 에너지 EA를 가지는 하전입자 A는 휘지 않고 직선운동을 계속하나, 하전입자 A와 다른 에너지 $E_B\;(=E_A+{\delta}E)$나 질량 $m_B\;(=m_A+{\delta}m)$을 가지는 하전입자는 휘게 되며, 그 휘는 정도는 ${\delta}E$나 ${\delta}m$에 비례하게 된다. 이 현상을 이용하여 다양한 종류의 에너지 또는 질량 분석기가 독일, 미국, 일본 등의 분석기기 선진국에서 개발되어 왔고, 전자현미경의 이미지 필터로도 활용되고 있으며, 통상 EXB 필터 또는 발명자의 이름을 딴 Wien 필터로 불리어지고 있다. $E{\times}B$ 필터는 일반적인 하전입자빔 렌즈와 다른 광학특성을 가지며, 지난 발표에서는 $E{\times}B$ 필터의 기본 궤도 방정식 및 다양한 2차 기하 수차 방정식의 유도과정 및 결과를 보여주었다. 본 발표에서는 EXB 필터의 전후에 배치시켜, 초점거리 등의 조정을 수행할 4극자와, $E{\times}B$ 필터에서 발생하는 2차 수차의 보정을 수행할 6극자의 광학특성의 계산 결과를 보여준다. 4극자-6극자-EXB필터-6극자-4극자 조합의 기본 광학궤도 계산 결과는 빔 다이어그램으로 보여준다. 6극자에 의해 수차를 줄여서 향상되는 에너지 분해능 값은 수치적으로 추정한다. 실제 제작이 된 각 부품의 외형 및 사진을 보여주어 에너지 필터의 제작 진행 상황을 보고한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11a
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• pp.527-530
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• 2003

본 논문에서는 제한요소가 많은 임베디드 환경에서의 실시간 Motion-JPEG 전송을 초점으로 하고 있으며, 현재에 얻어진 이미지와 이전의 이미지를 비교하여 움직임이 있는 부분의 블록만을 전송하는 시스템을 제안한다. 제안한 시스템에서는 처리시간과 처리 데이터 용량에서 이득을 얻기 위해 DCT 영역에서 두 영상을 블록 단위로 비교한다. 영상비교에 필요한 임계값 추출은 물체가 이미 지상에서 여러 픽셀과 블록에 연속적으로 존재하는 현상을 이용하여 계산된다. 비교 시 DCT 연산자체외 특징인 저주파로의 에너지 패킹현상을 이용하며 전체 DCT 계수들을 비교하지 않고 DC 성분을 포함한 일정 개수의 AC 성분만 사용한다.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.620-623
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• 2009

프레임 단위로 처리하는 카메라 영상 처리 기술에는 AWB, AE, AF 등이 있으며, AF는 고가의 초점제어 장치를 필요로 하기 때문에, AWB와 AE만이 모든 카메라에 기본적으로 탑재되는 핵심기능이다. ODM은 AWB나 AE 동작을 위해서 필요한 파라미터를 프레임 단위로 계산하는 하드웨어 모듈을 지칭한다. 본 논문에서는 R, G, B 평균값으로부터 밝기값을 연산하는 수식을 단순화하고, AE ODM과 AWB ODM을 통합하여, AE와 AWB에서 필요로 하는 모든 가산/제산 연산을 단 한 개의 가산기와 제산기를 이용하여 구현되는 ODM 구조를 제안한다. 제안한 ODM 구조 최소한의 연산자만을 사용하도록 구현되기 때문에, ISP를 내장하는 저가형 이미지 센서에 적합한 특성을 가진다.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.85-92
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• 2023

In this paper, we propose a method for automatically generating story-based abbreviated summaries from long-form dramas and movies. From the shooting stage, the basic premise was to compose a frame with illusion of depth considering the golden division as well as focus on the object of interest to focus the viewer's attention in terms of content delivery. To consider how to extract the appropriate frames for this purpose, we utilized elemental techniques that have been utilized in previous work on scene and shot detection, as well as work on identifying focus-related blur. After converting the videos shared on YouTube to frame-by-frame, we divided them into a entire frame and three partial regions for feature extraction, and calculated the results of applying Laplacian operator and FFT to each region to choose the FFT with relative consistency and robustness. By comparing the calculated values for the entire frame with the calculated values for the three regions, the target frames were selected based on the condition that relatively sharp regions could be identified. Based on the selected results, the final frames were extracted by combining the results of an offline change point detection method to ensure the continuity of the frames within the shot, and an edit decision list was constructed to produce an abbreviated summary of 62.77% of the footage with F1-Score of 75.9%

• Korean Journal of Optics and Photonics
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• v.9 no.2
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• pp.59-62
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• 1998

One dimensional inhomogeneous aperture modulation effects on the MTF of optical system was investigated. The lens undertest was a doublet made in Korea. It was 10 mm effective diameter, 87.8 mm effective focal length. The ray-fans and spot diagrams were caluculated and presented on the picture for on-axis and off-axis (field of view, 1$^{\circ}$ and 2$^{\circ}$). Aperture modulation was carried out by positioning a aperture modulator close contacted with the lens undertest. We bought two modulators from Edmud Company in U.S.A. One was linear type and the other was stepped type. The MTFs were measured on the best of focus for unmodulated apertue where the MTF has the largest value for 60 c/mm and were compared with one another. The MTFs of modulated apertures had a little lower values than the MTF of unmodulated aperture for on-axis but in the case off-axis, the values are highly improved as much as the wider field of view by modulating on the aperture.

• Journal of the Society of Disaster Information
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• v.8 no.2
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• pp.148-157
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• 2012

Recently, evacuation safety of building residents becomes the major concern, as the building has been higher and more complicated. Many high-rise multi use buildings are under construction in Korea. Required evacuation time using stairway is longer in high-rise buildings, moreover it is impossible for the disabled to evacuate by using stairway. For this reason the study on the effectiveness of using elevator for evacuation is being progressed. Elevator shaft flow coefficient is the major factor for the calculation of elevator piston effect. The results of this study can be used for the study of elevator piston effect as basic data. The flow coefficient simulation was performed using FLUENT, commercial CFD program. As a result of the flow coefficient simulation, the coefficient is 0.88 considering the safety factor. This result is verified that the result of experimental study, 0.86 is conservative.

• Korean Journal of Optics and Photonics
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• v.30 no.2
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• pp.48-58
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• 2019

We investigate the signal-to-noise ratios (SNRs) of time-domain (i.e. pulsed illumination) and frequency-domain (i.e. chirped illumination) photoacoustic signals measured by a spherically focused ultrasound transducer for spherical absorbers. The simulation results show that the time-domain photoacoustic SNR is higher than that of frequency-domain photoacoustic signals, as reported in the previous literature. We understand the reason for this SNR gap between the two measurement modes by analyzing photoacoustic-signal spectra, considering the incident beam energy controlled by the maximum permissible exposure. As the result of this approach, we find that filtering off the DC term in the chirped signal's spectrum improves frequency-domain photoacoustic SNRs by up to approximately 5 dB. In particular, it is observed that photoacoustic SNRs are highly sensitive to an upper-frequency value of frequency filtering functions, and the optimal upper-frequency values maximizing the SNR are different in time- and frequency-domain photoacoustic measurements.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.31-38
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• 2008

This paper deals with the nonlinear optimal control approach to helicopter maneuver problems using the indirect method. We apply a penalty function to the integral deviation from a prescribed trajectory to convert the system optimality to an unconstrained optimal control problem. The resultant two-point boundary value problem has been solved by using a multiple-shooting method. This paper focuses on the model selection strategies to resolve the problem of numerical instability and high wait time when a high fidelity model with rotor dynamics is applied. Four different types of helicopter models are identified, two of which are linear models with or without rotor models, as well as two models which include the nonlinear mathematical model for rotor in its formulation. The relative computation time and the number of function calls for each model are compared in order to provide a guideline for the selection of helicopter model.

• The Journal of the Acoustical Society of Korea
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• v.29 no.4
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• pp.258-264
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• 2010

In this paper, we propose an objective quality feature which is based on the human auditory system to measure vacuum cleaner noise. It is observed that some frequency bands are more sensitive to the human auditory system. Therefore, we divided the audible frequency range of vacuum cleaner noise into a number of frequency bands and the average energy of these bands was calculated. Among a number of average energies, an average energy of a frequency band was selected as the proposed feature. In order to test the performance of the proposed feature, fourteen vacuum cleaners were chosen and the noise was recorded in an anechoic-chamber. Then we performed subjective tests to obtain subjective scores of the noise data using the PCM (paired comparison method) and ACR (absolute category rating) subjective methods. The proposed objective quality feature shows high correlation with the subjective scores.

• Journal of Soil and Groundwater Environment
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• v.9 no.1
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• pp.79-86
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• 2004

Hydraulic conductivity along rock fracture is mainly dependent on fracture geometries such as orientation, aperture, roughness and connectivity. Therefore, it needs to consider fracture geometries sufficiently on a fracture model for a numerical analysis to calculate permeability coefficient in a fracture. This study performed new type of numerical analysis using a homogenization analysis method to calculate permeability coefficient accurately along single fractures with several fracture models that were considered fracture geometries as much as possible. First of all, fracture roughness and aperture variation due to normal stress applied on a fracture were directly measured under a confocal laser scaning microscope (CLSM). The acquired geometric data were used as input data to construct fracture models for the homogenization analysis (HA). Using the constructed fracture models, the homogenization analysis method can compute permeability coefficient with consideration of material properties both in microscale and in macroscale. The HA is a new type of perturbation theory developed to characterize the behavior of a micro inhomogeneous material with a periodic microstructure. It calculates micro scale permeability coefficient at homogeneous microscale, and then, computes a homogenized permeability coefficient (C-permeability coefficient) at macro scale. Therefore, it is possible to analyze accurate characteristics of permeability reflected with local effect of facture geometry. Several computations of the HA were conducted to prove validity of the HA results compared with the empirical equations of permeability in the previous studies using the constructed 2-D fracture models. The model can be classified into a parallel plate model that has fracture roughness and identical aperture along a fracture. According to the computation results, the conventional C-permeability coefficients have values in the range of the same order or difference of one order from the permeability coefficients calculated by an empirical equation. It means that the HA result is valid to calculate permeability coefficient along a fracture. However, it should be noted that C-permeability coefficient is more accurate result than the preexisting equations of permeability calculation, because the HA considers permeability characteristics of locally inhomogeneous fracture geometries and material properties both in microscale and macroscale.