• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.144-145
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• 2002

Stereotactic radiotherapy is required to irradiate a small tumor accurately. The radiotherapy showing improves when making an accidental error little boundlessly. It is performed according to treatment planning that is established by the outside landmark of head. At present, when stereotactic radiotherapy for a head is done, the Leksell Flame is fixed on the head, and positioning based on the point and so on which it is in that fixed implement is performed. However, there are problems on the method done at present in the point such as reappearance when the fractionated irradiation method in which the Leksell Flame is removed and installed at every treatment is done because there are landmarks outside the head. Landmarks in the skull were decided, and that precision was examined for the purpose of the improvement of the radiation therapeutic gain. Linac-graphy with longitudinal and lateral view were taken with 6 MV photon beams. A distance to base point inside the skull, each film measured the angle from a center of the small irradiation field, and comparison was done. From the results, a large accidental error wasn't seen as a result of the measurement by every film. Stereotactic radiotherapy for a head treatment had an accidental error of about several millimeters when treatment positioning was done. Therefore, it was thought that there was no problem about an accidental error to arise by putting a landmark in the skull. And, because an accidental error was easy to discover, we thought that modification could be done easily. It was suggested that a landmark in the skull on thus study were useful for improvement of stereotactic radiotherapy.

• 한국광학회:학술대회논문집
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• 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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• pp.96-97
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• 2001

A 110 mm diameter aspheric metal secondary mirror for a test model of an earth observation satellite camera was fabricated by ultra-precision single point diamond turning (SPDT) . Without a conventional polishing process, the surface texture of R$\sub$a/=2.8 nm, and the form error of R$\sub$a/=0.05 λ has been stably achieved In a laboratory condition. (omitted)

• 소성∙가공
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• 제22권7호
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• pp.383-388
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• 2013

Metal flow of the beam blank during H-beam rolling was examined in order to correlate the rolling defects with the beam blank configuration. For this purpose, H-beam rolling was performed on the beam blank where stainless steel bolts were inserted as the marker at the web and flange. The positional variation of the marker was monitored at each rolling pass, and the result was compared with the 3D FEM simulation employing the point tracking function. The simulation results were reasonably agreed with the experimental within the error of 0.5~1mm on both web and flange of the H-beam. It is anticipated that the 3D FEM simulation employing the point tracking function provides the guidance information on analyzing the correlation between the rolling defects and the beam blank configuration in H-beam rolling.

• 대한방사선치료학회지
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• 제29권2호
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• pp.53-64
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• 2017

목 적: 표적의 길이가 긴(length) 환자의 용적회전변조 방사선치료(V-MAT) 시 회전방향 오차의 크기에 따른 선량차이 경향을 $HexaPOD^{TM}$ evo RT system(6DoF couch)을 통해 알아보고 그 유용성을 평가하고자 하며, 이에 따른 회전오차 보정의 필요성을 제안하고자 한다. 대상 및 방법: 본원에서 치료를 받은 Esophagus cancer와 SCL을 포함한 Breast cancer 환자 중 HexaPOD 6DoF(Six-Degree of Freedom) couch를 사용한 10명을 대상으로 하였다. 6DoF couch를 이용하여 Rx(pitch), Ry(roll), Rz(yaw) 방향의 회전오차의 적용여부에 따른 선량차이를 알아보기 위하여 x, y, z축에 대한 자세오차를 확인하고, 자세 회전오차 값을 6DoF couch에 부여 임의의 오차를 발생시켜 변형된 선량계측 품질보증(Delivery Quality Assurance, DQA)을 시행, 점 선량과 감마값을 비교 분석하였다. 추가적으로 3cm의 직경에 5, 10, 15, 20 cm의 길이를 가진 각각의 표적의 치료계획에 회전오차의 크기를 $1^{\circ}$ 간격으로 적용한 후, 표적의 길이와 회전오차의 종류 및 크기에 따른 감마통과율의 변화양상을 확인했다. 결 과: 자세 회전오차가 적용된 경우의 점 선량과 감마통과율의 평균오차는 각각 Rx 방향에서 $2.50{\pm}1.11%$, $84.1{\pm}7.39%$, Ry 방향에서 $2.36{\pm}1.16%$, $81.0{\pm}8.49%$, Rz 방향에서 $2.35{\pm}1.10%$, $84.4{\pm}6.99%$를 나타냈다. 또한, 표적의 길이와 회전오차의 종류 및 크기에 따른 감마통과율 분석 결과 Ry 방향을 제외한 Rx와 Rz 방향에서 회전오차가 커질수록 감마통과율은 전반적으로 감소하는 경향을 보였으며, 특히 10 cm의 표적, Rz 방향으로 $2.5^{\circ}$ 회전오차가 부여된 경우에서 가장 낮은 감마통과율인 74.2 %를 나타냈다. 결 론: 표적의 길이가 긴 치료부위의 용적회전변조 방사선치료 시 회전오차의 보정은 필요하며, 6DoF couch의 사용은 환자자세의 재현성과 치료의 질적 효율을 높일 것으로 사료된다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.103-105
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• 2002

Whole body stereotactic radiosurgery (WBSRS) technique is believed to be useful for the metastatic lesions as well as relatively small primary tumors in the trunk. Unlike stereotactic radiosurgery to intracranial lesion, inherent limitation on immobilization of whole body makes it difficult to achieve the reliable setup reproducibility. For this reason, it is essential to develop an objective and quantitative method of evaluating setup error for WBSRS. An evaluation technique using image registration has been developed for this purpose. Point pair image registrations with WBSRS frame coordinates were performed between two sets of CT images acquired before each treatment. Positional displacements could be determined by means of volumetric planning target volume (PTV) comparison between the reference and the registered image sets. Twenty eight sets of CT images from 19 WBSRS patients treated in Asan Medical Center have been analyzed by this method for determination of setup random error of each treatment. It is objective and clinically useful to analyze setup error quantitatively by image registration technique with WBSRS frame coordinates.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.838-841
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• 2000

To improve the accuracy of products and improve the product quality, we need to enhance the machining accuracy of the machine tools. To this point of view, measurement and inspection of finished part as well as error analysis of machine tools has been studied for last several decades. OMM(On the Machine Measurement) has been issued to alternate with CMM, pointing out disadvantages of high expenses and lots of setting time in CMM. In this paper, we study 1) the spherical surface manufacturing by volumetric error compensation of machine tool, 2) the system development of OMM without detaching work piece from a bed of machine tool after working. 3) the generation of the finished part profile by On the machine measurement. Furthermore, the output of OMM is compared with that of CMM, and verified the feasibility of the measurement system.

• Current Optics and Photonics
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• 제8권1호
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• pp.38-44
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• 2024

Under the influence of atmospheric turbulence, a star's point image will shake back and forth erratically, and after exposure the originally small star point will spread into a huge spot, which will affect the ground calibration of the star sensor. To analyze the impact of atmospheric turbulence on the positioning accuracy of the star's center of mass, this paper simulates the atmospheric turbulence phase screen using a method based on a sparse spectrum. It is added to the static-star-simulation device to study the transmission characteristics of atmospheric turbulence in star-point simulation, and to analyze the changes in star points under different atmospheric refractive-index structural constants. The simulation results show that the structure function of the atmospheric turbulence phase screen simulated by the sparse spectral method has an average error of 6.8% compared to the theoretical value, while the classical Fourier-transform method can have an error of up to 23% at low frequencies. By including a simulation in which the phase screen would cause errors in the center-of-mass position of the star point, 100 consecutive images are selected and the average drift variance is obtained for each turbulence scenario; The stronger the turbulence, the larger the drift variance. This study can provide a basis for subsequent improvement of the ground-calibration accuracy of a star sensitizer, and for analyzing and evaluating the effect of atmospheric turbulence on the beam.

• 한국정보통신학회논문지
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• 제10권5호
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• pp.890-896
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• 2006

GPS 측량은 Multi-path 오차가 발생하기 때문에 도심지역이나 숲이 있는 항공사진에서는 지상기준점을 잡기 위해 GPS측량이 어렵다. 본 논문은 소규모 지역에서 3차원 정사사진 구현을 위한 GPS와 EDM의 적용에 관한 연구이다. 삼각점에서 연구대상지역에 대한 기준점을 내린 다음 EDM으로 정밀삼각측량으로 지상기준점을 선정하였다. 그리고 항공사진을 정사투영사진으로 변환하기 위해 획득된 지상기준점을 적용하였다. 그리고 연구대상지역에 대하여 항공정사사진을 이용한 3차원 모델링을 구현하여 향 후 추진될 3차원 GIS 구축을 위한 항공사진의 활용방안에 대해서 연구하였다. Multi-path 오차로 기인하는 GPS수신이 어려운 지점을 EDM을 이용하여 영상에서 균등히 분포된 지상기준점의 획득이 가능하였고 3차원 공간정보 자료구축에서 가장 기본이 되는 소규모 지역에서 항공사진의 활용이 가능할 것으로 판단되었다.

• 전기학회논문지
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• 제64권4호
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• pp.573-577
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• 2015

In this paper, we propose a signal processing board suitable for a semi-active laser tracking to detect an optical signal generated from the laser target designator by applying an analog trigger signal, the quadrant photodetector and a high speed ADC(analog-digital converter) sampling technique. We improved the stability by applying the averaging method to minimize the measurement error of a gaussian pulse. To evaluate the performances of the proposed methods, we implemented a prototype board and performed experiments. As a result, we implemented a frequency counter with an error 14.9ns in 50ms. PRF error code has a stability of less than 1.5% compared to the NATO standard. Applying the three point averaging method to ADC sampling, the stability of 28% in X-axis and 22% in Y-axis than one point sampling was improved.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.76-83
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• 2000

A measurement technique of a sea height of burst is introduced for a proximate test using the image recognition of video cameras. In the burst of fuse on the ocean, the burst center of fuse, the sea surface level and the height of calibration poles are measured by the process of image obtained from cameras. Finally, the height of burst of fuse can be computed by Hough transform algorithm. The error compensation algorithms are proposed to eliminate the errors caused by camera level and environmental parameters. As a result of experiment, it has been proved that the proposed measurement system shows the recognition of the center point of the burst image with ${\pm}$0.5m error.