• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.557-563
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• 2018

Coincidence summing correction effects are known to be greater as the efficiency of the detector increases and as the distance between the source and the detector increases. A point source($^{60}Co$) was used to vary the distance in the direction of the detector's center axis and in the radial direction to obtain the P/T ratio for Coincidence summing correction calibration. In this study, values for coincidence summing corrected calibration of the values in the central and radial directions were applied to the mixed volume source(450 ml CRM source) to compare the overall peak efficiency change according to P/T with Geant4. In addition, the efficiency obtained from the mapping method is applied to the seaweed, a marine sample, and the compatibility of the P/T ratio with the detector and sample very dose together. The efficiency corrected to 1,836 keV was applied to the energy zone affected by the efficiency of 500 keV and the relative error of the measured and corrected values was well matcched by the 3.2 % peak efficiency correction. As with 450 mL CRM source, the larger the volume, the lower the P/T ratio was by ${\pm}5%$. This is due to the increased scattering of gamma-rays emitted as the source becomes farther away from the detector, and this change in P/T has been confirmed to affect the Coincidence summing corrected peak efficiency.

• Journal of the Korean Society of Radiology
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• v.15 no.6
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• pp.821-831
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• 2021

In order to calibrate energy and efficiency using the PENELOPE Code, a PENELOPE simulation was performed using a volume source. Here, we want to verify peak efficiency and usefulness by performing simultaneous measurement and correction. calculate the coincident sum correction for all volumes, first subdivide the volumes of the cylinder and the four Marinelli beakers into three heights again. Therefore, the simultaneous measurement correction coefficient in three areas and the simultaneous measurement correction coefficient for the entire volume source are calculated as output. At low energies, the j value for each source volume (50-300 ml) is small and increases significantly in the high energy range. Simulation results showed good agreement within 2.5% for all source volumes except for 50 ml and 300 ml, which were up to 4%. This means that the correction for the simultaneous measurement effect during measurement is effective. In addition. Based on this, it can be confirmed that there is an advantage to improve the detection efficiency when measuring various sources and environmental samples.

• Journal of Radiation Protection and Research
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• v.30 no.3
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• pp.107-112
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• 2005

Cascade summing occurs when two gamma-rays emitted in the decay of a single nucleus both deposit energy in a detector. The effect may cause systematic errors that can reach levels of more than ten percent for some radionuclides. A method for estimation of the effect of these coincidences was developed. It is based on direct computation of the effect by means of peak to total ratio measured for the place around the detector. It has been shown that the P/T ratio for the given energy in the working space around the detector may not be a constant value and must use its mean value. Some results from a peak to total calibration study in the presence of scattering materials are also given.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1370-1374
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• 2009

국지강수로 발생하는 홍수사상을 예측하기 위해서 국내외적으로 레이더 강수량을 활용하고자 하는 연구가 많이 진행되고 있다. 레이더 강수량을 이용하는 주된 목적은 레이더 강수량이 제공하는 강수량의 공간 분포를 최대한 활용하여 단기홍수를 효과적으로 예측하자는데 있다. 레이더 강수량이 강수의 시공간적 특성을 잘 묘사할 수 있는 반면에 강우량에 대한 신뢰성은 의문에 여지가 있다. 이를 위해 다양한 방법을 통해 강우량을 보정하고자 하는 연구가 진행되고 있으나 시공간적 정보를 손실시키지 않고 동시에 강우량의 편차를 보정하는 기술의 발전은 그다지 만족스럽지 않다. 일반적으로 사용되는 지상강수와 지상강수지점의 해당하는 레이더 강수량의 비율을 일괄적으로 모든 격자에 적용하는 GR 공식이 주로 이용되고 있다. 이런 경우 레이더 자료의 공간적 정보의 손실되는 단점이 있다. 이러한 점을 보완하기 위해서 조건부합성 방법이라는 기법을 이용하여 레이더강수의 공간적 특성을 그대로 유지하면서 지점강수량 수준의 분산을 회복하도록 모형을 구성하여 이용하고 있다. 조건부합성 방법에서는 일반적으로 크리깅 방법을 통해 레이더강수와 지점강수량을 공간 분포시켜 사용하게 되는데 이런 경우 Variogram을 추정하는 데 있어서 어려움이 있다. 본 연구에서는 이러한 점을 보완하고자 지점강수량 및 레이더강수량에 대해서 공간분포를 실시할 수 있는 Harmonic Spline기법, Nearest Neighbor기법 등 다양한 Interpolation 기법을 활용한 새로운 조건부합성 기법을 개발하였다. 이를 국내 레이더 강수자료에 적용하여 모형에 대한 신뢰성 및 적합성을 평가하였다.

• Proceedings of the KSRS Conference
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• 2008.03a
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• pp.3-6
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• 2008

본 논문에서는 레일형 GB-SAR의 단점을 극복하고자 차량에 원형레일을 탑재하여 신속한 기동을 확보하고 합성구경의 길이를 늘리며 영상영역을 확장한 Arc-SAR의 설계안을 제시한다. 하드웨어 측면에서 살펴보면, 밴형 차량의 상부에 원형레일을 설치하고 마이크로파 송, 수신 안테나를 탑재한 후 레일 위를 1mm 이내의 정밀도로 이동시키며, 자료를 획득하게 된다. 이때 안테나에 연결된 동축 케이블은 차량 내부의 송, 수신장치에 연결되는데 RF대역에서 완벽히 작동하는 슬립링이 없기 때문에 내부 송, 수신 장치를 턴 테이블위에 장착하여 외부 안테나의 이동과 동일한 각도로 회전하여, 동축 케이블의 꼬임을 방지하게 된다. 송, 수신 장치의 구성은 벡터 네트워크 분석기를 기반으로 마이크로파 앰프, 마이크로파 스위치로 구성되며, 통합 제어 소프트웨어를 통해 외부 안테나의 이동과 함께 제어된다. 한편, Arc-SAR 영상의 구현은 원형레일을 따라 얻어지는 합성구경의 기하학적인 특수성을 감안하여 최초로 시도될 것이다. 이 시스템은 RTK-GPS를 장착하여 지반변형 모니터링 시 차량 이동 오차를 최소화 하고자 하며, 이외에 고정형 산란체를 이용하여 차량 이동 오차를 보정하고자 한다. 또한 AWS (Automatic Weather System)을 장착하여 위상의 대기보정을 동시에 수행할 것이다. 이 시스템은 차량 탑재에 의한 기동성의 확보로 침수나 침하 등 긴급 재난 지역에 즉각적인 대응이 가능하며, 대형 구조물의 주기적인 변형 모니터링 등에 활용성이 클 것이다.

• Journal of Internet Computing and Services
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• v.18 no.5
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• pp.17-22
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• 2017

In a MPC coding using excitation source of voiced and unvoiced, it would be a distortion of speech waveform. This is caused by normalization of synthesis speech waveform of voiced in the process of restoration the multi-pulses of representation section. This paper present PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) used V/UV/S( Voiced / Unvoiced / Silence ) switching, position compensation in a multi-pulses each pitch interval and Unvoiced approximate-synthesis by using specific frequency in order to reduce distortion of synthesis waveform. Also, I was implemented that the PCFBD-MPC( Position Compensation Frequency Band Division-Multi Pulse Coding ) system and evaluate the SNRseg of PCFBD-MPC in coding condition of 8kbps. As a result, SNRseg of PCFBD-MPC was 13.4dB for female voice and 13.8dB for male voice respectively. In the future, I will study the evaluation of the sound quality of 8kbps speech coding method that simultaneously compensation the amplitude and position of multi-pulse source. These methods are expected to be applied to a method of speech coding using sound source in a low bit rate such as a cellular phone or a smart phone.

• Proceedings of the Korea Contents Association Conference
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• 2011.05a
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• pp.419-420
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• 2011

본 논문의 목적은 실시간 인터렉티브가 가능한 3D 입체영상의 구현 방법에 있다. 기존의 입체영상 구현 방식의 광학적이며 하드웨어적인 한계범위를 실시간 구현을 통해 보정해 보는 것과 동시에 색합성을 통한 기초적 입체영상 방법을 실험해봄으로써 입체영상의 제작방법만이 아닌, 상호작용을 통한 입체깊이감의 구현이라는 새로운 기능성을 탐구해 보고자 함에 근본 목적이 있다. 이를 위해 사용된 영상구현시스템은 Max/Msp/Jitter를 사용하였으며, 실질적으로 입체감의 깊이감있는 재현을 위한 실험으로는 피터 위머(Peter Wimmer)가 제안한 애너그리프 합성방법을 사용해 보았다.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.531-539
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• 2023

Self-absorption is the most important factor affecting the accuracy of gamma spectroscopy measurements in environmental samples. In particular, it is affected by other factors such as the chemical composition of the sample, geometric shape, thickness, density, atomic number, distance between the sample and detector, energy of the emitted gamma photon, and humidity coefficient or percentage in the sample. To test the calibration method, a 450 ml CRM standard source (9 nuclide) Marinelli beaker was used. Five soil samples among environmental samples were measured by density by applying the corrected values. Therefore, it can be seen that the self-absorption value is more effective for somewhat large and low photon energy. In the case of environmental samples, it was confirmed that the overall energy peak efficiency through self-absorption of the source greatly depends on the density of the sample.

• Smart Media Journal
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• v.4 no.1
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• pp.9-15
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• 2015

Nonverbal communications such as eye gazing, posture, and gestures send forceful messages. In regard to nonverbal communication, eye gazing is one of the most strong forms that an individual can use. However, lack of mutual gazing occurs when we use video conferencing system. The displacement between locations of the eyes and a camera gets in the way of eye contact. The lack of eye gazing can give unapproachable and unpleasant feeling. In this paper, we propose an eye gazing correction for video conferencing. We use two cameras installed at the top and the bottom of the television. The captured two images are rendered with 2D warping at virtual position. We implement view morphing to the detected face, and synthesize the face and the warped image. The result shows that eye gazing is corrected and correctly preserved and the image was synthesized seamlessly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.239-249
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• 2012

Recently, the virtual view generation method using depth data is employed to support the advanced stereoscopic and auto-stereoscopic displays. Although depth data is invisible to user at 3D video rendering, its accuracy is very important since it determines the quality of generated virtual view image. Many works are related to such depth enhancement exploiting a time-of-flight (TOF) camera. In this paper, we propose a fast 3D scene capturing system using one TOF camera at center and two high-resolution cameras at both sides. Since we need two depth data for both color cameras, we obtain two views' depth data from the center using the 3D warping technique. Holes in warped depth maps are filled by referring to the surrounded background depth values. In order to reduce mismatches of object boundaries between the depth and color images, we used the joint bilateral filter on the warped depth data. Finally, using two color images and depth maps, we generated 10 additional intermediate images. To realize fast capturing system, we implemented the proposed system using multi-threading technique. Experimental results show that the proposed capturing system captured two viewpoints' color and depth videos in real-time and generated 10 additional views at 7 fps.