• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.433-439
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• 1996

노심 외각에 설치되어 노심 외각으로 누설되는 중성자를 검출하여 노심내의 출력 변화를 지시해 주는 노외계측기(Excore Detector)는 운전중 노심의 변화를 정확히 감지하도록 정기적으로 교정되어져야 한다. 노외계측기는 노내계측기(Incore Detector)를 통하여 측정되어진 축방향 출력편차(Axial Offset)를 이용하여 교정하고 있다. 기존의 방법은 노내계측기로 최소한 4회 노심 출력을 측정하여 최소자승법(Least Square Method)으로 상수들을 구한후 노외계측기를 교정한다. 여기서 소개되는 단순 노외계측기 교정법은 노내계측기로 2회 측정되어진 자료들을 이용하는 2점 교정법과 1회 측정되어진 자료들을 이용하는 1점 교정법으로, 계측기 반응상수(Detector Response Factor)를 계산한후 교정되어진 노외계측기의 출력편차를 측정값과 비교하였다. 위의 두가지 방법을 고리 3호기 9주기, 10주기에 적용하여 노심 운전영역(~$\pm$10%)에서 2점 교정법은 최대 1.40 %, 1점 교정법은 최대 0.63 %의 오차를 보여주고 있다. 단순 노외계측기 교정법은 노심출력을 1회 또는 2회 측정하므로 교정시간을 줄이고 제어봉의 사용을 억제하여 방사성 폐기물을 감소시키는 효과와 기존의 교정 방법과 같은 정확성을 기대할수 있다.

• Progress in Medical Physics
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• v.15 no.4
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• pp.192-196
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• 2004

The activity of Ir-192 sources for high dose rate (HDR) Brachytherapy in Korea were measured by using the well-type chamber and using the calibration Jig with the Farmer-type ionization chamber to compare the manufacturer certificated source strength which is supplied with each new Ir-192 source. The activity of two different source models used in six hospitals were measured. The range of measured activities to the manufacturer's suggested ones was -2.40% to +3.31% for the calibration Jig and -3.12% to 0.00% for the well-type chamber system. The source strength values given by the manufacturer for the 6 sources were within ${\pm}5%$ for the two different measuring equipment. Our results demonstrate that well-type chamber as wall as Farmer-type chamber system are appropriate system for the routine source calibration procedures in HDR brachytherapy. Whenever a new source is installed to use in clinics, a source calibration should be carried out.

• The Journal of Korean Society for Radiation Therapy
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• v.28 no.2
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• pp.109-121
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• 2016

To verify the accuracy of the image guided radiotherapy using ExacTrac 6D couch, the error values in six directions are randomly assigned and corrected and then the corrected values were compared with CBCT image to check the accurateness of ExacTrac. The therapy coordination values in the Rando head Phantom were moved in the directions of X, Y and Z as the translation group and they were moved in the directions of pitch, roll and yaw as the rotation group. The corrected values were moved in 6 directions with the combined and mutual reactions. The Z corrected value ranges from 1mm to 23mm. In the analysis of errors between CBCT image of the phantom which is corrected with therapy coordinate and 3D/3D matching error value, the rotation group showed higher error value than the translation group. In the distribution of dose for the error value of the therapy coordinate corrected with CBCT, the restricted value of dosage for the normal organs in two groups meet the prescription dose. In terms of PHI and PCI values which are the dose homogeneity of the cancerous tissue, the rotation group showed a little higher in the low dose distribution range. This study is designed to verify the accuracy of ExacTrac 6D couch using CBCT. It showed that in terms of the error value in the simple movement, it showed the comparatively accurate correction capability but in the movement when the angle is put in the couch, it showed the inaccurate correction values. So, if the body of the patient is likely to have a lot of changes in the direction of rotation or there is a lot of errors in the pitch, roll and yaw in ExacTrac correction, it is better to conduct the CBCT guided image to correct the therapy coordinate in order to minimize any side effects.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.254-261
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• 2009

This study suggested that the table of CT-simulator and the laser alignment system using diagnostic CT scanner have an efficient method for improvement in alignment between the planned target center of traverse image with CT scanner. It was conducted on the daily QA when presented in the AAPM TG66 with correcting the laser alignment system using geometric trigonometric functions and investigated the effectiveness of correction methods as compared with those before and after correction. Before correction error was 3.82mm between the planned target center of image, the table longitudinal axis was twisted with 0.436o. The laser alignment system using geometric trigonometric functions in after correction was satisfied with tolerance limits of ${\pm}2mm$ when occurred about 0.7mm in errors between the planned target center. The table correction to satisfy the geometric accuracy is very inefficient over against the time and economic loss as well as technical limits in the case of application as only radiation therapy associated with CT-simulator with diagnostic CT scanner in use. But, the method which corrects the laser alignment system is economic and relatively simple with possibility of getting well geometric accuracy and we suppose that it is efficient method for applying in the clinic.

• Journal of Radiation Protection and Research
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• v.33 no.2
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• pp.47-51
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• 2008

Objective: This study analyzed errors due to rotation or tilt of the magnetic resonance (MR) imaging indicator during image acquisition for a stereotactic radiosurgery. The error correction procedure of a commercially available stereotactic neurosurgery treatment planning program has been verified. Materials and Methods: Software virtual phantoms were built with stereotactic images generated by a commercial programming language, Interactive Data Language (version 5.5). The thickness of an image slice was 0.5 mm, pixel size was $0.5{\times}0.5mm$, field of view was 256 mm, and image resolution was $512{\times}512$. The images were generated under the DICOM 3.0 standard in order to be used with Leksell GammaPlan$^{(R)}$. For the verification of the rotation error correction function of Leksell GammaPlan$^{(R)}$, 45 measurement points were arranged in five axial planes. On each axial plane, there were nine measurement points along a square of length 100 mm. The center of the square was located on the z-axis and a measurement point was on the z-axis, too. Five axial planes were placed at z=-50.0, -30.0, 0.0, 30.0, 50.0 mm, respectively. The virtual phantom was rotated by $3^{\circ}$ around one of x, y, and z-axis. It was also rotated by $3^{\circ}$ around two axes of x, y, and z-axis, and rotated by $3^{\circ}$ along all three axes. The errors in the position of rotated measurement points were measured with Leksell GammaPlan$^{(R)}$ and the correction function was verified. Results: The image registration errors of the virtual phantom images was $0.1{\pm}0.1mm$ and it was within the requirement of stereotactic images. The maximum theoretical errors in position of measurement points were 2.6 mm for a rotation around one axis, 3.7 mm for a rotation around two axes, and 4.5 mm for a rotation around three axes. The measured errors in position was $0.1{\pm}0.1mm$ for a rotation around single axis, $0.2{\pm}0.2mm$ for double and triple axes. These small errors verified that the rotation error correction function of Leksell GammaPlan$^{(R)}$ is working fine. Conclusion: A virtual phantom was built to verify software functions of stereotactic neurosurgery treatment planning program. The error correction function of a commercial treatment planning program worked within nominal error range. The virtual phantom of this study can be applied in many other fields to verify various functions of treatment planning programs.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2000.11a
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• pp.463-466
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• 2000

SAR imaging 시스템 전파환경에서 목표물의 정보를 성공적으로 추출해 내기 위해서는 반사된 신호를 수신할 때 Coherent detection이 필수적이다. 수신시 Incoherent detection은 복소 위상오차 형태로 나타나서 실제 목표물의 영상에 심각한 Degradation을 야기시켜 치명적인 결과를 초래하게된다. 본 논문에서는 하나의 목표물에서 수신되는 신호를 파동방정식으로부터 모델링하고 모델링된 신호의 각 주파수대의 조합에 의해 전체 수신신호로부터 위상오차의 기울기를 유도한다. 더욱더 정확한 위상오차를 추정하기 위해 추정된 위상오차로부터 수신신호에 포함된 오차를 제거하고, 오차가 제거된 신호의 대역폭을 추정한다. 추정된 대역폭에 맞도록 알고리즘에 재 적용시켜 교정되지 못한 오차를 추정해 나간다. 이때 반복적인 위상오차 제거기법을 적용하고 Iteration의 종료를 자동으로 결정하기 위해 지능형 대역폭 추정 기법을 제시한다. 컴퓨터의 모의 실험에서, 위상오차를 포함한 수신 신호로부터 알고리즘을 적용하여 오차를 제거하고,, Wavefront Reconstruction 기법에 적용시켜 알고리즘의 성능을 영상으로 확인한다.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.117-125
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• 2005

Generally, the inertial navigation and guidance unit uses AF(Analog-to-Frequency) converters which convert analog signals into frequency signals to enhance a measurement accuracy of gyroscope and accelerometer outputs. The confidence level of AF converter is guaranteed by a prudential decision of calibration procedure and a performance of periodic calibration test. In this paper, we focus on the synchronous charge balance type AF converter which has a separate positive or negative current input and its calibration method is described. The calibration tests are classified into the scale factor error calibration and the bias calibration. These tests are automatically performed by the calibration program.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.229-236
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• 2017

In general, an error budget of monopulse radar is proposed by manufacturer who assuming that all of external enviromental error resources such as multipath, glint, dynamic lag variation are removed. So until now, a measurement uncertainty of monopulse radar can be discussed including external enviromental error resources. In this paper, it is described that which kinds of error resource can effect on monopulse radar measurement uncertainty for different target property. To prove it experimentally, at first a simulation result is described assuming that all of external enviromental error resources are removed. It only includes receiver thermal noise. And then, monopulse radar measurement uncertainty estimation results tracking on calibration target which is fixed on specific position, calibration sphere which is moving slowly, weapon systems firing test which is moving fast are described quantitativly. All of these targets have different dynamic property.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2341-2349
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• 2015

The commonly used Goldschmidt's floating-point divider algorithm performs two multiplications in one iteration. In this paper, a tentative error corrected K'th Goldschmidt's floating-point number divider algorithm which performs K times multiplications in one iteration is proposed. Since the number of multiplications performed by the proposed algorithm is dependent on the input values, the average number of multiplications per an operation in single precision and double precision divider is derived from many reciprocal tables with varying sizes. In addition, an error correction algorithm, which consists of one multiplication and a decision, to get exact result in divider is proposed. Since the proposed algorithm only performs the multiplications until the error gets smaller than a given value, it can be used to improve the performance of a divider unit. Also, it can be used to construct optimized approximate reciprocal tables.

• Progress in Medical Physics
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• v.12 no.2
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• pp.141-146
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• 2001

It is well known that assurance of the radiation therapy needs for an accuracy of $\pm$ 5 % in the delivery of an absorbed dose to target volume. Therefore, the dose evaluation of brachytherapy source and/or linear accelerate beam must be a stability with accuracy. In an advanced country, they recommended to use the radioactive check source for reference air ionization chamber for a stable response of radiation field chamber. In this experiments, the radioactive source Sr-90 and PR-05 air ionization chamber were used for standard source and reference ion chamber. The response of reference ion chamber showed as an 1.000$\pm$ 0.010 uncertainty for 10 years long and the evaliuation f dose discrepancy of clinical field ion chamber showed as 0.997 $\pm$0.011 in a $^{60}$ Co brachytherapy soruce. In our experiments, we can assuarance the long halflife standard source is reliable to preserve the calibration factor of reference chamber in stability.