• 한국공작기계학회논문집
• /
• 제10권1호
• /
• pp.36-42
• /
• 2001

In this paper, PSD(Position Sensitive Detector) sensor system that estimates position for moving objects in 2D plane is developed. PSD sensor is used to measure the position the position of and incidence light in real-time. To get the position of light source of moving target, a new parameter calibration algorithm and neural network technique are proposed and applied. Real-time position measurements of the mobile robot with light source is examined to validate the proposed method. It is shown that the proposed technique provides accurate position estimation of the moving object.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2004년도 추계학술대회논문집
• /
• pp.1032-1035
• /
• 2004

Pressure distribution is measured by way microphones to identify noise sources in the space. For example, beam-forming method or acoustic holography use phase information to identify the source. Therefore, the phase is significant information to correctly identify the source position. However, due to the microphone characteristics and measuring systems, measured signals always have errors, which make the identification difficult. Therefore, phase calibration of microphones is needed. Duct and speaker systems are generally used as calibrators. Acoustic characteristics of the calibrator are, of course, functions of many Parameters of the system: i.e. duct size, frequency, and microphone spacing. In this paper, design parameters which effect on the performance and size of the calibrators are considered. Then the parameters would be applied to design and real product of the phase-calibrator.

• Nuclear Medicine and Molecular Imaging
• /
• 제42권1호
• /
• pp.61-69
• /
• 2008

목적: 일반적인 바늘구멍 조준기를 사용한 SPECT 시스템은 피사체를 확대시킬 수 있다는 장점이 있어 설치류와 같은 소동물 영상을 얻기에 적합하다. 그러나 몇 가지 기하학적 오차는 영상의 해상도를 크게 저하시킬 수 있으므로 이를 보정해주는 기법이 필요하다. 본 연구에서는 바늘구멍 조준기를 장착한 삼중 헤드 SPECT 시스템에서 간단한 기하학적 보정기법을 개발하고 이를 모형과 몇몇 설치류 영상에 대해 적용하여 기하학적 보정 효과를 검증하였다. 대상 및 방법: Trionix사의 TRIAD XLT9 SPECT시스템에 1.0 mm의 입구를 갖는 바늘구멍 조준기를 장착하고 실험하였다. 회전각도에 의존하는 기하학적 오차를 측정하기 위해 중앙에 위치시킨 점선원의 영상을 얻었다. 무게중심을 구하는 방법으로 점선원의 중심 위치를 찾아주었고 이 중심 위치를 이용하여 기하학적 오차를 보정하였다. 또한 입력해준 회전 반경과 실제 회전 반경의 차이를 보정하기 위해 종축 방향으로 서로 떨어져 있는 두 개의 점선원 영상을 얻었다. 기하학적 오차의 보정 기법을 검증하기 위해 점선원을 보정 전, 후에 각각 재구성하여 이를 비교하였다. 또한 열소반점 초소형 모형 및 몇몇 설치류 영상에 대해 SPECT 영상을 얻어 보정 효과를 검증하였다. 결과: 보정 전 기울어진 도넛 모양으로 보이던 점선원의 재구성 영상이 보정 후 완벽한 구 모양으로 얻어졌고 축방향의 해상도 역시 개선되었다. 열소반점 모형과 설치류 영상에서도 매우 높은 해상도의 영상을 얻을 수 있었다. 결론: 기하학적 오차에 의한 영상 왜곡 및 해상도의 저하 현상이 이 연구에서 개발된 하나 또는 두 개의 점선원을 이용한 간단한 보정 기법에 의해 크게 보정되었다.

• Journal of Radiation Protection and Research
• /
• 제43권4호
• /
• pp.137-142
• /
• 2018

Background: Gamma-ray detectors having a thin window of a material with low atomic number can increase the true coincidence summing effects for radionuclides emitting X-rays or gamma-rays. This effect can make efficiency calibration or spectrum analysis more complicated. In this study, a Cu shield was tested as an X-ray filter to neglect the true coincidence summing effect by X-rays and gamma-rays in gamma-ray spectrometry, in order to simplify gamma-ray energy spectrum analysis. Materials and Methods: A Cu shield was designed and applied to an n-type high-purity germanium detector having an $X-{\gamma}$ summing effect during efficiency calibration. This was tested using a commercial, certified mixed gamma-ray source. The feasibility of a Cu shield was evaluated by comparing efficiency calibration results with and without the shield. Results and Discussion: In this study, the thickness of a Cu shield needed to avoid true coincidence summing effects due to $X-{\gamma}$ was tested and determined to be 1 mm, considering the detection efficiency desired for higher energy. As a result, the accuracy of the detection efficiency calibration was improved by more than 13% by reducing $X-{\gamma}$ summing. Conclusion: The $X-{\gamma}$ summing effect should be considered, along with ${\gamma}-{\gamma}$ summing, when a detection efficiency calibration is implemented and appropriate shielding material can be useful for simplifying analysis of the gamma-ray energy spectra.

• Nuclear Engineering and Technology
• /
• 제47권7호
• /
• pp.939-944
• /
• 2015

The calibration methods of neutron-measuring devices such as the neutron survey meter have advantages and disadvantages. To compare the calibration factors obtained by the shadow cone method and semi-empirical method, 10 neutron survey meters of five different types were used in this study. This experiment was performed at the Korea Atomic Energy Research Institute (KAERI; Daejeon, South Korea), and the calibration neutron fields were constructed using a $^{252}Californium$ ($^{252}Cf$) neutron source, which was positioned in the center of the neutron irradiation room. The neutron spectra of the calibration neutron fields were measured by a europium-activated lithium iodide scintillator in combination with KAERI's Bonner sphere system. When the shadow cone method was used, 10 single moderator-based survey meters exhibited a smaller calibration factor by as much as 3.1-9.3% than that of the semi-empirical method. This finding indicates that neutron survey meters underestimated the scattered neutrons and attenuated neutrons (i.e., the total scatter corrections). This underestimation of the calibration factor was attributed to the fact that single moderator-based survey meters have an under-ambient dose equivalent response in the thermal or thermal-dominant neutron field. As a result, when the shadow cone method is used for a single moderator-based survey meter, an additional correction and the International Organization for Standardization standard 8529-2 for room-scattered neutrons should be considered.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2007년도 학술발표회 논문집
• /
• pp.454-458
• /
• 2007

Nonpoint source (NPS) pollution is a serious problem causing the degradation of soil and water quality. Concentrated overland flow is the primary transport mechanism for a large amount of NPS pollutants from hillslope areas to downslope areas in a watershed. In this study, a soil erosion model, nLS model, to identify transitional overland flow regions (i.e., ephemeral gully head areas) was developed using the kinematic wave overland flow theory. Spatial data, including digital elevation models (DEMs), soil, and landcover, were used in the GIS-based model algorithm. The model was calibrated and validated using gully head locations in a large agricultural watershed, which were identified using 1-m aerial photography. The model performance was better than two previous approaches; the overall accuracy of the nLS model was 72 % to 87 % in one calibration subwatershed and the mean overall accuracy was 75 to 89 % in four validation subwatersheds, showing that the model well predicted potential transitional erosion areas at different watersheds. However, the user accuracy in calibration and validation was still low. To improve the user accuracy and study the effects of DEM resolution, finer resolution DEMs may be preferred because DEM grid is strongly sensitive to estimating model parameters. Information gained from this study can improve assessing soil erosion process due to concentrated overland flow as well as analyze the effect of microtopographic landscapes, such as riparian buffer areas, in NPS control.

• 한국물환경학회지
• /
• 제30권2호
• /
• pp.159-165
• /
• 2014

Vegetative Filter Strip (VFS) is one of effective Best Management Practices (BMPs) to prevent sediment-laden water problem, is installed at the edge of source area such agricultural area so that sediment occurred in source area is trapped by VFS before it flow into stream or river. Appropriate scale of it needs to be simulated before it is installed, considering various field conditions. In this study, a model using VFSMOD-w model and Genetic Algorithm to determine effective VFS length was developed, it is available to calibrate input parameter related to source area sediment yield through thousands of VFSMOD-w simulations. Useful DBs, moreover, are stored in the model so that very specific input parameters can be used with reasonable values. Compared simulated values to observed data values for calibration, R2 and Nash-Stucliffe model efficiency coefficient were 0.74 and 0.65 in flow comparison, and 0.89 and 0.79 in sediment comparison. The model determined 1.0 m of Filter Length, 0.18 of Filter Slope, and 0.2 cm of Filter Media Spacing to reduce 80% of sediment by VFS. The model has not only Auto-Calibration module also DBs for specific input parameters, thus, the model is expected to be used for effective VFS scale.

• Nuclear Engineering and Technology
• /
• 제54권11호
• /
• pp.4220-4225
• /
• 2022

Monte Carlo (MC) simulations are increasingly being used as an alternative or supplement to the gamma spectrometric method in determining the full energy peak efficiency (FEPE) necessary for radionuclide identification and quantification. The MC method is more advantageous than the experimental method in terms of both cost and time. Experimental calibration with standard sources is difficult, especially for specimens with unusually shaped geometries. However, with MC, efficiency values can be obtained by modeling the geometry as desired without using any calibration source. Modeling the detector with the correct parameters is critical in the MC method. These parameters given to the user by the manufacturer are especially the dimensions of the crystal and its front edge, the thickness of the dead layer, dimensions, and materials of the detector components. This study aimed to investigate the effect of the front edge geometry of the detector crystal on efficiency, so the effect of rounded and sharp modeled front edges on the FEPE was investigated for <300 keV with three different HPGe detectors in point and volume source geometries using PHITS MC code. All results showed that the crystal should be modeled as a rounded edge, especially for gamma-ray energies below 100 keV.

• 한국광학회지
• /
• 제16권4호
• /
• pp.361-365
• /
• 2005

표면거칠기가 큰 가공면의 표면형상을 비접촉 고속 측정 하기 위해 고안된 점광원 절대간섭계는 점광원의 위치가 시스템 변수로 정의된다. 시스템 오차인 점광원의 위치 오차가 측정 결과에 미치는 영향을 분석하며, 이를 보정하기 위해 CCD 카메라를 이용한 보정법을 제안한다. 제안된 방법을 검증하기 위해 기준면을 측정하여 측정 정밀도의 향상을 확인하며, 이를 거친 표면형상의 특징을 가진 칩모듈 측정에 적용하였다. 측정 결과 기존의 촉침식 측정기와 $50mm{\time}50mm$의 영역에서 $9.8{\mu}m$의 측정 차이를 보임을 확인하였다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제15권1호
• /
• pp.96-100
• /
• 2015

Adaptive background gain calibration loop for multi-lane serial links is proposed. In order to detect and cancel gain mismatches between lanes, a single digital loop using a ${\sum}{\Delta}$ ADC is employed, which provides a real-time adaptation of gain variations and is shared among all lanes to reduce power and area. Evaluation result showed that gain mismatches between lanes were well calibrated and tracked, resulting in timing budget at $10^{-6}$ BER increased from 0.261 UI to 0.363 UI with stable loop convergence.