• Journal of Radiation Protection and Research
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• 제25권1호
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• pp.31-36
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• 2000

방사선치료시 환자자세의 변화에 따라 방사선조사영역이 불일치하게 되어 주변의 정상조직에 불필요한 방사선조사가 생길수 있다. 본 연구에서는 골반부위 방사선 치료환자를 대상으로 Elecrtronic portal imaging device(EPID)로 고정기구를 사용한 방사선조사영역의 영상을 획득하여 고정기구사용에 따른 조사영역변화에 대한 오차를 분석하고자 한다 충남대학교병원 치료방사서과에서 1998년 8월부터 1999년 8월까지 21명의 골반부위 방사선치료환자를 대상으로 하였다. 환자들은 모두 앙와위자세를 유지하면서 치료를 받았고 고정기구를 사용하지 않은 11명과 고정기구를 사용한 10명으로 각각 나누어서 연구를 실행하였다 고정기구는 스터로폼을 이용하였다. 전체 치료과 정중 EPID를 이용하여 전면조사시 x(right-left)축, y(longitudinal)방향을, 측면조사는 z축(vertical) y축(longitudinal)방향을 대상으로 영상을 얻었다. 전체 치료과정중 얻은 영상들을 모의치료시 촬영한 기준필름과 matching기법을 이용하여 오차를 측정하였다. 고정기구를 사용하지 않은 11명 환자의 전면 조사영역의 경우 x축, y축으로의 평균이동값은 각각 0.19 mm, 0.48 mm이었고 계통이동과 우연이동은 평균이동으로부터 표준편차가 x축, y축으로 각각 2.38 mm, 2.19 mm와 1.92 mm, 1.29 mm이었다. 측면조사영역에서 z축, y축으혹의 평균이동값은 각각 -3.61 mm, 2.07 mm이었고 계통이동과 우연이동은 표준편차가 z축, y축므로 각각 3.20 mm, 2.29 mm와 2.73 mm, 1.62 mm이었다. 한편 고정기구를 사용란 10명 환자의 전면 조사영역에서 x축, y축으로의 평균이동값은 각각 0.71 mm, -1.07 mm이었고 계통이동과 우연이동은 표준편차가 x축, y축으로 각각 1.80 mm, 2.26 mm와 1.56 mm, 1.27 mm이었다. 측면조사영역에서 z축, y축으로의 평균이동값은 각각 -1.76 mm 1.08 mm 이었고 계통이동과 우연이동은 평균이동으로부터 표준편차가 x축, y축으로 각각 1.87 mm 2.83 mm와 1.68 mrn, 1.65 mm이었다. 본 연구에서는 고정기구를 사용한 환자군의 조사영역의 오차는 고정기구를 사용하지 않은 환자군의 조사영역의 오차에 비해 약간 감소됨을 확인할 수 있었다. 그리고 두그룹간의 우연오차는 감소하고 계통오차는 크게 변화하지 않는 경향을 보였다. 그러므로 골반부위 방사선 치료사 고정기구를 사용함으로써 방사선 조사영역에 대한 오차유발의 원인을 줄일 수 있을 것으로 생각된다.

• 치과방사선
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• 제29권2호
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• pp.417-422
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• 1999

Purpose : The aim of this study was to assess the validity of standard deviation of gray scale histogram in digital subtraction radiography as a test parameter for superimposition error. Materials and Methods : Twenty periapical radiographs were used as baseline images and they were copied to exclude the influence of exposure geomety and contrast differences. These subsequent images were linearly displaced by 0.1-0.5 mm in the x-. y- and xy-directions, rotated by 0.5-3° and distorted by angular contraction of 1-5° in x- and y-axis before subtraction. The standard deviations of gray levels in the subtraction images were obtained and paired t-tests were performed. Pearson correlation coefficients(r) were calculated between the standard deviations and the superimposition errors. Results : Linear displacement showed high correlation coefficients of 0.997, 0.997 and 0.995 in x-. y- and xy-axis respectively. Statistically significant different standard deviation existed among all linearly displaced groups(p<0.05). Distortion showed relatively low correlation coefficients of 0.982 and 0.959 in x- and y-axis. The standard deviations between the two distortion groups were statistically significant different(p<0.05). Conclusion : Standard deviation of gray level distribution in digital subtraction images is satisfactory but not perfect similarity measure to assess the superimposition errors.

• 한국방사선학회논문지
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• 제14권6호
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• pp.811-817
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• 2020

본 연구의 목적은 손목관절 CT 검사에서 환자 자세를 X-축, Y-축으로 변화시키고 CT 검사장치의 channel 변화에 따른 MTF 평가를 하는 것이다. CT 장치와 손목 팬텀을 이용하여 isocenter를 중심으로 X-축으로 0(일치), 5, 10, 15 cm 이동시켜 검사하고, Z-축은 반시계 방향으로 -20°, -40° 회전하여 검사하였다. 검사는 16, -40, 64 channel을 이용하여 channel 별 차이가 있는지도 확인하고자 하였다. 검사한 영상은 자뼈와 좌우측 노뼈의 MTF 값을 측정하여 비교하였다. isocenter를 중심으로 X-축으로 이동시킨 실험에서 이동 거리가 커질수록 MTF 값은 감소하였고, 이때 MTF 값은 channel과는 무관한 것으로 확인되었다. Z-축에서 반시계 방향으로 -20°, -40° 손목관절을 회전시킨 실험에서 회전정도와 MTF는 무관한 것으로 확인되었다. 또한 channel과도 무관하였다. 결론적으로 손목관절 CT 검사에서 손목은 X-축 방향으로 이동을 최대한 억제시키고, Z-축으로의 회전은 검사 대상자의 환경에 따라 변화하여도 영상의 MTF에는 큰 영향을 주지 않을 것이라 사료된다.

• 수산해양기술연구
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• 제58권4호
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• pp.289-298
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• 2022

Sea anchor for fishery is commonly used in jigging fishery and purse seine. The study of sea anchor was studied for improvement of opening efficiency and drag by changing the type of shape and the diameter of vent. However, standard specification of sea anchor is not set and has not been studied for underwater stability. Therefore, this study aimed to improve underwater stability of sea anchor by changing a vent diameter and weight of sinker. The experiment was conducted in flume water tank. The experiment model of sea anchor was made from actual model of sea anchor which is used in fishery by similarity law. The model of sea anchor was designed to different types of vent diameter and weight of sinker in different current speed. The value of movement of side to side (X-axis), drag of sea anchor (Y-axis) and movement of up and down (Z-axis) was measured for 30 seconds. Each value of X, Y, Z-axis was analyzed through t-test and ANOVA analysis to verify that each value had a significant difference according to the difference compositions. There was correlation between the movement of X-axis and Z-axis. The drag of sea anchor was stronger as the current speed increased. However, the larger the vent diameter, the weaker the drag. From the result of the standard deviation, the movement of X-axis was inversely proportional to the vent diameter. However, movement of Z-axis was larger as the weight of sinker was the heaviest or lightest from the result of the standard deviation. These results suggest that the sea anchor should be combined with proper size of the vent diameter and the weight of sinker to improve the stability.

• 한국정밀공학회지
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• 제30권1호
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• pp.77-84
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• 2013

Most research on the inkjet printing technology has focused on the development of inkjet head itself, and of process, not on the landing accuracy of the droplets to a target. Thus, this paper presents the modeling and experimental verification on the static landing accuracy and precision of the droplets from the magnetostrictive inkjet head. A simple model based on the angle deviation of a nozzle tip and on a distance to a substrate is considered, assuming that there is no ambient effect. The angle deviation of the nozzle tip is determined by using its digital image with the aid of a pixel calculation program, and the distance to the substrate is set to 1 mm. Three experiments have planned and preformed. The first experiment is to collect the initial data for the landing distribution of the droplets. The second experiment is to collect the repeatability data of the stage used. Then, these data are used to rederive the equation for the final landing position of the droplet. The final experiment is to verify the equation and to show the calibration results. The respective landing accuracy of the droplet after calibration on the x-axis and on y axis has improved from $338.51{\mu}m$ and $-133.63{\mu}m$ to $7.06{\mu}m$ and $13.11{\mu}m$. The respective percent improvement on the x-axis and on y axis reaches about 98 and about 90. The respective landing precision of the droplet after calibration on the x-axis and on y axis has improved from ${\pm}182.6{\mu}m$ and ${\pm}182.88{\mu}m$ to ${\pm}24.64{\mu}m$ and ${\pm}42.76{\mu}m$. The respective percent improvement on the x-axis and on y axis reaches about 87 and about 77.

• 한국기계가공학회지
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• 제8권3호
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• pp.1-6
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• 2009

This paper presents a geometrical error compensation of tool alignment for sharp edge bite on B axis controlled machine. In precision micro patterning, bite alignment is crucial parameter for machined surface. To decrease bite alignment error, plus tilted bite from B axis center is touched to reference work piece(pin gauge) and checked the deviation from original position. Same process is repeated for maximum touch deviation value. From this touched position value, wheel alignment error in X axis and Z axis can be calculated on B axis center. Experimental results show that this compensation method is efficient to correct sharp edge bite alignment.

• Journal of Biosystems Engineering
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• 제24권1호
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• pp.41-50
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• 1999

This study aims at detecting the three dimensional gripping points for the transplanting robot system to grip in the process of developing transplanting robot system, which is one of the automation systems for transplanting tissue culture. The stereo vision system equipped with two cameras has been used to detect the gripping points of the plant stem. The method for matching the plants of the image information which came from two cameras was to measure the total numbers of pixels, leaves, and the heights of the plants. The gripping points were detected near the roots after extracting the stem parts by the standard deviation of the X axis according to the Y axis. The performance test of the developed program showed that the detecting errors of the gripping points were 0∼1mm for X axis and 1∼2mm for Y & Z axis. The mean running time of the program was about 3 seconds.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.447-450
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• 2003

This paper concerns on application of active magnetic bearing(AMB) system to levitate the elevation axis of an electro-optical sight mounted on moving vehicles. In such a system. it is desirable to retain the elevation axis within the predetermined air-gap while the vehicle is moving. A disturbance compensation control is proposed to reduce the base motion response. In the consideration of the uncertainty of the system model, a filtered-x least-mean-square(FXLMS) algorithm is used to estimate adaptively the frequency response function of the feedforward control which cancels disturbance responses. The frequency response function is fitted to an optimal feedforward control. Experimental results demonstrate that the proposed control reduces the air-gap deviation to 27.7% that by feedback control alone.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1712-1719
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• 2003

This paper concerns on application of active magnetic bearing(AMB) system to levitate the elevation axis of an electro-optical sight mounted on moving vehicles. In such a system, it is desirable to retain the elevation axis within the predetermined air-gap while the vehicle is moving. An optimal base acceleration feedforward control is proposed to reduce the base motion response. In the consideration of the uncertainty of the system model, a filtered-x least-mean-square(FXLMS) algorithm is used to estimate the frequency response function of the feedforward control which cancels base motions. The frequency response function is fitted to an optimal feedforward control. Experimental results demonstrate that the proposed control reduces the air-gap deviation to 27.7% that by feedback control alone.

• 한국기계가공학회지
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• 제6권3호
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• pp.53-57
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• 2007

This paper presents a geometrical error compensation of tool alignment for B axis controlled machine. In precision machining, tool alignment is crucial parameter for machined surface. To decrease tool alignment error, plus tilted tool from B axis center is touched to reference work piece and checked the deviation from original position. Same process is performed in minus tilt. Comparing these 2 touch positions, wheel alignment error in X axis and Z axis can be calculated on B axis center. Experimental results show that this compensation method is efficient to correct tool alignment.