• Progress in Medical Physics
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• v.24 no.3
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• pp.191-197
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• 2013

Upon radiation treatment, it is the important factor to monitor the patient's motion during radiation irradiated, since it can determine whether the treatment is successful. Thus, we have developed the system in which the patient's motion is monitored in real time and moving treatment position can be automatically corrected during radiation irradiation. We have developed the patient's position monitoring system in which the patient's position is three dimensionally identified by using two CCD cameras which are orthogonal located around the isocenter. This system uses the image pattern matching technique using a normalized cross-correlation method. We have developed the system in which trigger signal for beam on and off is generated by quantitatively analyzing the changes in a treatment position through delivery of the images taken from CCD cameras to the computer and the motor of moving couch can be controlled. This system was able to automatically correct a patient's position with the resolution of 0.5 mm or less.

• Journal of Astronomy and Space Sciences
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• v.22 no.1
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• pp.1-12
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• 2005

The Korean VLBI Network (KVN) will open a new field of research in astronomy, geodesy and earth science using the newest three Elm radio telescopes. This will expand our ability to look at the Universe in the millimeter regime. Imaging capability of radio interferometry is highly dependent upon the antenna configuration, source size, declination and the shape of target. In this paper, imaging simulations are carried out with the KVN system configuration. Five test images were used which were a point source, multi-point sources, a uniform sphere with two different sizes compared to the synthesis beam of the KVN and a Very Large Array (VLA) image of Cygnus A. The declination for the full time simulation was set as +60 degrees and the observation time range was -6 to +6 hours around transit. Simulations have been done at 22GHz, one of the KVN observation frequency. All these simulations and data reductions have been run with the Astronomical Image Processing System (AIPS) software package. As the KVN array has a resolution of about 6 mas (milli arcsecond) at 220Hz, in case of model source being approximately the beam size or smaller, the ratio of peak intensity over RMS shows about 10000:1 and 5000:1. The other case in which model source is larger than the beam size, this ratio shows very low range of about 115:1 and 34:1. This is due to the lack of short baselines and the small number of antenna. We compare the coordinates of the model images with those of the cleaned images. The result shows mostly perfect correspondence except in the case of the 12mas uniform sphere. Therefore, the main astronomical targets for the KVN will be the compact sources and the KVN will have an excellent performance in the astrometry for these sources.

• Korean Journal of Remote Sensing
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• v.39 no.5_4
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• pp.1135-1144
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• 2023

Many agricultural reservoirs in South Korea, constructed before 1970, have become aging facilities. The majority of small-scale reservoirs lack measurement systems to ascertain basic specifications and water levels, classifying them as unmeasured reservoirs. Furthermore, continuous sedimentation within the reservoirs and industrial development-induced water quality deterioration lead to reduced water supply capacity and changes in reservoir morphology. This study utilized Light Detection And Ranging (LiDAR) sensors, which provide elevation information and allow for the characterization of surface features, to construct high-resolution Digital Surface Model (DSM) and Digital Elevation Model (DEM) data of reservoir facilities. Additionally, bathymetric measurements based on multibeam echosounders were conducted to propose an updated approach for determining reservoir capacity. Drone-based LiDAR was employed to generate DSM and DEM data with a spatial resolution of 50 cm, enabling the display of elevations of hydraulic structures, such as embankments, spillways, and intake channels. Furthermore, using drone-based hyperspectral imagery, Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were calculated to detect water bodies and verify differences from existing reservoir boundaries. The constructed high-resolution DEM data were integrated with bathymetric measurements to create underwater contour maps, which were used to generate a Triangulated Irregular Network (TIN). The TIN was utilized to calculate the inundation area and volume of the reservoir, yielding results highly consistent with basic specifications. Considering areas that were not surveyed due to underwater vegetation, it is anticipated that this data will be valuable for future updates of reservoir capacity information.

• Journal of the Korean Society of Radiology
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• v.17 no.6
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• pp.985-991
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• 2023

A tissue-equivalent phantom is necessary for quality control of hyperthermia therapy. However, since there is no phantom for this purpose, phantoms made from agar are being used in various studies. The tissue-equivalent properties of the agar phantom were confirmed by comparison with the tissue-equivalent material bolus in this study. CT images of the agar phantom and bolus were acquired, and tissue equivalent characteristics were analyzed with image analysis and dose calculation using a computerized radiation therapy planning system. The average pixel value was 96.960±10.999 in bolus, 108.559±8.233 in 3% agar phantom, and 111.844±8.651 in 4% agar phantom. Using the SSD technique, 100 cGy was prescribed at a depth of 1.5 cm and 6 MV X -ray was set to irradiated to 10x10 cm2, and the absorbed dose according to depth was calculated from the central axis of the beam. The intraclass correlation coefficient of dose distribution of bolus, 3% agar phantom, and 4% agar phantom was 0.979 (p<.001, 95%CI .957-.991). The density (g/cm3) at the point where the absorbed dose was calculated was 0.990±0.020 at the bolus, 1.018±0.020 at the 3% agar phantom, and 1.035±0.024 at the 4% agar phantom. In this study, the internal density distribution and uniformity of the agar phantom were confirmed to be appropriate as a tissue equivalent material by analysis of CT images and a computerized radiation therapy planning system.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.4 s.31
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• pp.35-43
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• 2004

Multibeam Echosounder system is the latest technology of a hydrographic survey utilized in producing an electronic nautical chart, obtaining a DEM with high precision, making a moving image by Swath surveying a wide area. As a fundamental study for improving the precision of MBES, we compared and analyzed measurements of DGPS and Motion sensor, and studied for the dynamic characteristics of vessel's movements. DGPS was installed in front and in the rear and on both side or the vessel and surveyed. The receiving precision of surveyed GPS results was obtained to the satisfactory extent that was possible to valuate the accuracy of Motion sensor as 0.0016$^{\circ}$ of the roll value and 0.0009$^{\circ}$ of the pitch value. The relationship between the values of heading, pitch, and roll in Motion sensor and the data of DGPS was proportional correlation. In addition, it is considered that deviations by elements like rapid turning and vibration of the vessel will be occurred, although the correlation of each deviation according to each amount or change is proportional. It is suitable that GPS installs in the central line of the vessel that is less affected than other places by waving because the amount of change in the tide level obtained from GPS survey and the value of heave are similar with the values taken by Motion sensor, and the velocity of GPS is different from installed places. The accuracy of the final result from MBES could be affected by the values of gyro and Motion sensor inputted to MBES processor because there were intervals of 15s and 13s of receiving time in gyro and Motion sensor respectively compared with the real-time measurements of DGPS.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.59-59
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• 2003

목적 : 환자의 호흡에 의한 움직임 및 부정확한 환자 자세 setup 때문에 3 차원 전신 정위 방사선치료,3 차원 입체조형 방사선치료 IMRT와 같은 방사선 치료기술에서 병소에 대한 정확한 표적 위치측정은 매우 어려운 실정이다. 그러므로 본 연구는 방사선 치료시 환자의 움직임을 최대한 고정시켜 줄 수 있으며 환자 자세에 대한 setup 오차를 감소시키고 환자 전신에 산재한 병소의 위치를 좌표화할 수 있는 전신 정위 프레임 제작과 제작한 프레임에 대한 고정효과 및 재현성을 나타내는 환자 자세의 setup 오차를 평가하는데 있다. 재료 및 방법 : 자체 제작한 전신 정위 프레임 구조는 CT 영상 촬영 가능성에 중점을 두고 병소 표적의 좌표실현 및 환자체형에 따른 다양성 그리고 프레임에 대한 견고성 및 안정성 확인에 초점화하여 제작하였다. 이렇게 제작된 전신 정위 프레임에 대한 방사선 투과율 측정 실험과 CCTV 카메라와 DVR(Digital Video Recorder)를 이용해 환자 자세 변화에 대한 영상을 획득하여 matlab으로 구현한 오차분석용 프로그램으로 환자 외부자세에 대한 오차 비교 평가하고 CT 촬영에 의한 가상표적 위치측정 실험을 수행하였다. 또 한 고정벨트 추가 사용으로 인한 환자의 고정효과 정도를 살펴보았다. 결과 : 제작된 전신 정위 프레임에 대한 방사선 투과율은 마그네트론 10, 21 MeV의 에너지에서 95, 96% 의 투과율이 측정되었고 30 $^{\circ}$. 60 。각도의 경사로 빔이 전달될 때는 90.3, 94.4% 가 측정되었다. CCTV 카메라를 이용하여 흉부 및 복부의 움직임을 촬영한 영상을 Matlab프로그램으로 구현한 오차분석 프로그램을 적용한 결과, 환자 자세에 대한 오차의 평균값은 흉부의 lateral 방향에서는 3.63$\pm$1.4 mm, AP 방향에서는 2.1$\pm$0.82 mm이었다. 그리고 복부의 later의 방향에서는 7.0$\pm$2.1 mm, AP 방향에서는 6.5$\pm$2.2 mm 이었다. 또한 표적 위치측정을 위해서 환자의 피부에 임의의 가상표적을 부착하고 CT 촬영한 영상결과, 프레임으로 가상표 적에 대한 위치를 정확히 파악할 수 있었다. 결론 : 제작된 프레임을 적용하여 방사선투과율 측정실험, 환자 외부자세에 대한 오차 측정실험, 가상표적 위치측정 실험 등을 수행하였다. 환자 외부자세에 대한 오차 측정실험 경우, 더 많은 Volunteer를 적용하여 보다 정확한 오차 측정실험이 수행되어야 할 것이며 정확한 표적 위치 측정실험을 위해서 내부 마커를 삽입한 환자를 적용한 임상실험이 수행되어야 할 것이다. 또한 위치결정에서 획득한 좌표값의 정확성을 알아보기 위해서 팬톰을 이용한 방사선조사 실험이 추후에 실행되어져야 할 것이다. 그리고 제작된 프레임에 Rotating X선 시스템과 내부 장기의 움직임을 계량화하고 PTV에서의 최적 여유폭을 설정함으로써 정위 방사선수술 및 3 차원 업체 방사선치료에 대한 병소 위치측정과 환자의 자세에 대한 setup 오차측정 결정에 도움이 될 수 있을 것이라고 사료된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.1
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• pp.20-25
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• 2012

The COMS, which is a multi-purposed satellite that provide the oceanic measurement data and meterological image data, is operating since 2010. Ka-band satellite communication transponder in COMS gets the MSM function that can provide the required multi-beam and transmits the multi-mode signal with high data rate. The phase noise of COMS communication transponder can be increased because of several local oscillators for MSM function and the utilization of Ka-band frequency. The phase noise affects the performance for the multi-mode and high rate data based- transmission method, it is not possible to recover the transmission data in system with the high system phase noise. In this paper, the phase noise of COMS was measured and the effects of the measured phase noise are analysed and evaluated in the viewpoint of the noise bandwidth of transmission system, Also the transmission performances for multi-mode and high rate data are evaluated in the presence of COMS phase noise.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.184-192
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• 2006

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the $16{\times}16$ array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and honeycomb cores, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that this antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of $5^{\circ}$ and $5^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna will be applicable to the wideband SAR system.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.156-156
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• 1999

자성박막에 존재하는 자기구역의 형상 및 동력학은, 자성박막의 학문적 연구와 응용기술 개발의 핵심을 제공하는 매우 중요한 분야의 하나로서, 최근 크게 관심이 고조되고 있다. 본 연구에서는 차세대 광자기 재질로 각광받고 있는 Co/Pd 다층박막에서의 자기구역 형상 및 자기구역 동력학을 연구하였다. 전자빔 진공증착 시스템을 사용하여, Co 층의 두께와 Pd층의 두께, 그리고 전체 층수가 변화하는 일련의 Co/Pd 다층박막 시료를 제작하였다. 제작된 모든 시료가 명목두께에 대하여 4%의 정밀도로 제작되었음을 확인하였고, 제작된 시료의 자기 및 광자기 성질은 자기이력곡선 등을 측정하였다. 또한 고성능 광자기 Kerr 현미경 시스템을 이용하여 자성박막에 존재하는 자기구역의 형상 및 자기구역 동력학을 관찰하였다. 이 장비는 1,000배의 배율에서 0.3$\mu\textrm{m}$의 공간분해능을 가지며 실시간 자기구역 영상을 CCD 카메라를 통해 컴퓨터에 저장함으로써, 자지구역 거동현상을 관찰할 수 있다. 자성다층박막에 존재하는 자기구역의 형상을 이론적으로 예측하기 위하여, 다층박막 구조에서의 정자기 에너지를 일반적으로 계산할 수 있는 이론을 유도하였다. 이 이론을 통해 다층박막의 자성층의 두께가 두꺼워짐에 따라, 자기구역의 형상이 단일 자기구역 형상에서 줄무늬 자기구역 형상으로 천이함을 예측할 수 있었고, 이러한 지구구역 천이현상을 Co-Pd 다층박막의 자화역전현상을 연구하였고, 새로운 자구동력학 정량분석기술을 개발하여 Co/Pd 다층박막에 적용함으로써 자화역전의 자구벽 이동속도와 핵형성 확률을 각각 정량적으로 구하였다. 이러한 관찰 및 분석기술을 통하여, Co/Pd 다층박막의 층구조에 따라 대조적인 자화역전현상이 존재함을 관찰하였다. 이러한 대조적인 자화역전현상을 결정짓는 요인을 연구하기 위해서 나노자성학이온을 이용한 자화역전현상을 결정짓는 요인을 연구하기 위해서 나노자성학이온을 이용한 자화역전모델을 개발하였으며, 이를 통하여 자성박막의 거시적 자기성질에 의해 이러한 대조적인 자화역전모델을 개발하였으며, 이를 통하여 자성박막의 거시적 자기성지에 의해 이러한 대조적인 자화역전현상이 결정될 수 있음을 설명하였다. 또한, 미시적 자기이력곡선 측정을 통하여 자성박막구조에 따른 국소적인 구조불균일성을 관찰하였고, 이러한 구조불균일성 또한 대조적인 자화역전현상을 결정하는 큰 요인임을 논의하였다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.2
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• pp.72-78
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• 2021

This paper proposes a wide-band dual-polarization stacked patch array antenna for satellite SAR system applications. The array antenna was designed for loss minimization and wide-band characteristics to enhance the performance of the SAR system and optimize it for active return loss in applications to active phased arrays. The fabricated array antenna showed a performance of 19.26%/19.79% fractional bandwidth within the -10 dB reference level of the active return loss and showed loss characteristics of 0.797 dB/0.799 dB averaged within the operational frequency for both H/V-polarization cases. The pattern performance was verified by comparing the measured patterns with the calculated patterns obtained by the array factor.