• Journal of electromagnetic engineering and science
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• 제17권4호
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• pp.169-177
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• 2017

The role of electromagnetic (EM) waves in magnetic fusion plasma-ranging from radio frequency (RF) to microwaves-has been extremely important, and understanding of EM wave propagation and related technology in this field has significantly advanced magnetic fusion plasma research. Auxiliary heating and current drive systems, aided by various forms of high-power RF and microwave sources, have contributed to achieving the required steady-state operation of plasmas with high temperatures (i.e., up to approximately 10 keV; 1 eV=10000 K) that are suitable for future fusion reactors. Here, various resonance values and cut-off characteristics of wave propagation in plasmas with a nonuniform magnetic field are used to optimize the efficiency of heating and current drive systems. In diagnostic applications, passive emissions and active sources in this frequency range are used to measure plasma parameters and dynamics; in particular, measurements of electron cyclotron emissions (ECEs) provide profile information regarding electron temperature. Recent developments in state-of-the-art 2D microwave imaging systems that measure fluctuations in electron temperature and density are largely based on ECE. The scattering process, phase delays, reflection/diffraction, and the polarization of actively launched EM waves provide us with the physics of magnetohydrodynamic instabilities and transport physics.

• 천문학회보
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• 제36권2호
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• pp.126.2-126.2
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• 2011

MIRIS(Multipurpose InfraRed Imaging System)는 과학기술위성 3호의 주 탑재체이며 2012년 하반기 발사예정이다. MIRIS 우주관측 카메라는 0.9-2.0 ${\mu}m$ 영역에서 3.67 deg. x 3.67 deg. FOV로 우리 은하평면 survey 관측과 우주배경복사(CIB) 관측을 수행할 것이다. 현재 MIRIS는 비행모델 개발 마무리 단계에 있으며, 검교정 시험, 열-진공 시험, 진동 시험 등을 수행하고 나면 2011년 말 위성 본체와의 조립을 진행할 것이다. 망원경이 복사냉각(Passive Cooling)을 통해 200K 이하로 냉각되면, dewar에 설치된 소형 냉각기를 가동하여 적외선 센서를 90K 정도로 냉각한다. MIRIS 우주관측카메라에는 PICNIC($256{\times}256$ pixel) 센서를 사용하였고, 상온과 냉각된 상태에서의 노이즈 특성을 측정하였다. PICNIC 센서와 dewar내부를 냉각하기 위해 RICOR사의 K-508 micro stirling cooler를 사용하는데, cooler가 동작하면서 전자부에 영향을 주어 주된 잡음으로 나타남을 확인하였다. Cooler에서 발생하는 잡음을 최소화 하기위해 fanout B/D와 LVPS 부분을 개선하였으며, 본 발표에서는 잡음 측정 결과에 대해 논의 하고자 한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.604-609
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• 2002

The passive microwave remote sensing has progressed considerably in recent years. Important earth surface parameters are detected and monitored by airborne and space born radiometers. However the spatial resolution of real aperture measurements is constrained by the antenna aperture size available on orbiting platforms and on the ground. The inverse problem technique is researched in order to improve the spatial resolution of microwave scanning radiometer. We solve a two-dimensional (surface) temperature-imaging problem with a major intention to develop high-resolution methods. In this paper, the scenario for estimation of both radiometer point spread function (PSF) and target configuration is explained. The PSF of the radiometer is assumed to be unknown and estimated from the observations. The configuration and brightness temperature of targets are also estimated. To do this, we deal with the parametric modeling of observation scenario. The performance of developed algorithms is illustrated on two-dimensional experimental data obtained by the water vapor radiometer.

• 대한원격탐사학회지
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• 제19권1호
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• pp.53-59
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• 2003

The passive microwave remote sensing has progressed considerably in recent years Important earth surface parameters are detected and monitored by airborne and space born radiometers. However the spatial resolution of real aperture measurements is constrained by the antenna aperture size available on orbiting platforms and on the ground. The inverse problem technique is researched in order to improve the spatial resolution of microwave scanning radiometer. We solve a two-dimensional (surface) temperature-imaging problem with a major intention to develop high-resolution methods. In this paper, the scenario for estimation of both radiometer point spread function (PSF) and target configuration is explained. The PSF of the radiometer is assumed to be unknown and estimated from the observations. The configuration and brightness temperature of targets are also estimated. To do this, we deal with the parametric modeling of observation scenario. The performance of developed algorithms is illustrated on two-dimensional experimental data obtained by the water vapor radiometer.

• Investigative Magnetic Resonance Imaging
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• 제17권3호
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• pp.169-180
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• 2013

목적 : 본 연구는 신경망의 인과성을 이해하기 위해 사용되는 방법인 뇌경두개자기자극기 (TMS)를 기능자기공명영상(fMRI) 내에서 동시에 시행하기 위한 적합성을 평가하는데 그 목적이 있다. 대상 및 방법 : TMS 코일을 지지할 수 있도록 비자성의 특징을 갖는 물질인 Polyetherether Keton (PEEK)을 이용하여 홀더를 제작하였다. 컴퓨터 시뮬레이션을 이용하여 MR 스캐너 안에서의 TMS 코일의 위치와 방향에 따른 자기장의 분포를 계산하였다. 또한, TMS 자극시 발생할 수 있는 영상 왜곡을 최소화하면서 fMRI영상을 획득하기 위하여 볼륨과 볼륨 획득 사이 간극 동안 TMS 자극을 가하는 기법을 제안하였다. 결과 : 컴퓨터 시뮬레이션을 통해서 코일 중심의 자기장은 코일에서 거리가 멀어질수록 급격하게 감소함을 확인하였다. 팬텀실험을 통해 fMRI 자극제시는 볼륨간 시간 간격을 100 ms정도 수준에서도 영상 왜곡을 줄이는데 문제가 없음을 확인하였다. 운동 과제 수행과 TMS로 운동 중추 자극시 각각의 뇌반응 분석 연구를 통해 fMRI 측정 중 TMS가 가능함을 확인하였다. 결론 : 본 연구를 통해 fMRI 환경 내에서 관심 영역에 TMS를 가함으로써 뇌 기능의 인과적 연결성 연구를 할 수 있는 기본 도구를 확립하게 되었다.

• 천문학회보
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• 제42권2호
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• pp.87.3-88
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• 2017

한국천문연구원은 차세대소형위성 1호의 근적외선 영상분광기 NISS (Near-infrared Imaging Spectrometer for Star formation history) 탑재체를 개발하여 2017년 6월 30일에 최종 비행모델을 납품하였고, 이 발표는 탑재체 NISS 구조체의 비행모델 개발 결과를 보고한다. NISS는 0.9 - 2.5um (R~20) 근적외선 파장에서 관측을 해야 하기 때문에, 구조체의 배경잡음을 없애기 위해서 200K까지 passive cooling으로 냉각되며, H2RG 검출기는 소형 냉동기에 의해 약 88K에서 운영된다. NISS 구조체의 passive cooling을 효율적으로 수행하기 위해서 방열판, Kevlar 지지대, MLI, 표면제어용 필름 등을 조립하였고, 실제 지상 시험을 통해서 그 성능을 확인하였다. NISS 구조체는 최종 시스템 조립 과정에서 전자부 하네스 조립을 함께 수행했으며, 온도 모니터링 센서를 부착하고 소형 냉동기 피드백 온도를 반복 시험을 통해서 결정하였다. NISS 구조체는 미러 및 렌즈를 지지하는 광기계부를 함께 포함하기 때문에 발사 및 우주환경에서 광학 성능을 유지하기 위한 설계를 거쳐서 제작 되었으며, 최종 시스템 검교정 시험, 진동 및 열진공 시험을 통해서 그 성능을 확인하였다. NISS를 탑재한 차세대소형위성 1호는 2018년 상반기에 미국의 Falcon 9 발사체에 실려서 발사될 예정이다.

• Journal of Korean Neurosurgical Society
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• 제66권5호
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• pp.511-524
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• 2023

Objective : This animal model aimed to compare the rat group that received brain irradiation and did not receive additional treatment (only saline) and the rat group that underwent brain irradiation and received Granulocyte colony stimulating factor (G-CSF) treatment. In addition, the effects of G-CSF on brain functions were examined by magnetic resonance (MR) imaging and histopathologically. Methods : This study used 24 female Wistar albino rats. Drug administration (saline or G-CSF) was started at the beginning of the study and continued for 15 days after whole-brain radiotherapy (WBRT). WBRT was given on day 7 of the start of the study. At the end of 15 days, the behavioral tests, including the three-chamber sociability test, open field test, and passive avoidance learning test, were done. After the behavioral test, the animals performed the MR spectroscopy procedure. At the end of the study, cervical dislocation was applied to all animals. Results : G-CSF treatment positively affected the results of the three-chamber sociability test, open-space test and passive avoidance learning test, cornu Ammonis (CA) 1, CA3, and Purkinje neuron counts, and the brain levels of brain-derived neurotrophic factor and postsynaptic density protein-95. However, G-CSF treatment reduced the glial fibrillary acidic protein immunostaining index and brain levels of malondialdehyde, tumor necrosis factor-alpha, nuclear factor kappa-B, and lactate. In addition, on MR spectroscopy, G-CSF had a reversible effect on brain lactate levels. Conclusion : In this first designed brain irradiation animal model, which evaluated G-CSF effects, we observed that G-CSF had reparative, neuroprotective and anti-neurodegenerative effects and had increased neurotrophic factor expression, neuronal counts, and morphology changes. In addition, G-CSF had a proven lactate-lowering effect in MR spectroscopy and brain materials.

• 한국습지학회지
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• 제18권2호
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• pp.132-147
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• 2016

동아시아 지역의 위성 토양수분 데이터 활용을 위해 Soil Moisture Ocean Salinity (SMOS) 위성에 탑재된 Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) 센서와 Global Change Observation Mission-Water (GCOM-W1) 위성에 탑재된 Advanced Microwave Scanning Radiometer 2 (AMSR2) 센서 기반 토양수분 데이터를 자료동화 데이터인 Global Land Data Assimilation System (GLDAS)를 기준 값으로 Cumulative Distribution Function (CDF) 기법과 회귀식을 활용하여 보정하는 연구를 수행하였다. 동아시아 지역에서 발생하는 전파간섭의 영향을 고려하여 토양수분 산출에 적합하다고 판단되는 Radio Frequency Interference (RFI), Data Quality indeX (DQX) 한계값과, 합성일수를 제시하였다. 보완된 위성 토양수분 데이터를 지점 토양수분 데이터와 비교한 결과 상관계수가 평균 27%, 11% 증가하였고, Root Mean Square Deviation (RMSD, 평균제곱근 편차)는 평균 61%, 57% 감소하였다. 추가적으로, 보정된 위성데이터를 GLDAS 토양수분 데이터와 비교했을 때, 보정된 MIRAS 및 AMSR2 데이터는 한반도의 80% 및 90%의 지역에서 상관계수가 증가하였으며, 한반도 전역에서 RMSD가 감소하였다. 본 연구를 통해 향후 MIRAS 및 AMSR2 위성 데이터를 융합하여 각 위성의 토양수분 데이터를 보완 할 수 있는 가능성을 제시하였다.

• 대한인간공학회지
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• 제34권6호
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• pp.583-595
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• 2015

Objective: The purpose of this study was to determine the reliability of lower limb joint angles computed with the software ImageJ during jumping movements. Background: Kinematics is the study of bodies in motion without regard to the forces or torques that may produce the motion. The most common method for collecting motion data uses an imaging and motion-caption system to record the 2D or 3D coordinates of markers attached to a moving object, followed by manual or automatic digitizing software. Above all, passive optical motion capture systems (e.g. Vicon system) have been regarded as the gold standards for collecting motion data. On the other hand, ImageJ is used widely for an image analysis as free software, and can collect the 2D coordinates of markers. Although much research has been carried out into the utilizations of the ImageJ software, little is known about their reliability. Method: Seven healthy female students participated as the subject in this study. Seventeen reflective markers were attached on the right and left lower limbs to measure two and three-dimensional joint angular motions. Jump performance was recorded by ten-vicon camera systems (250Hz) and one digital video camera (240Hz). The joint angles of the ankle and knee joints were calculated using 2D (ImageJ) and 3D (Vicon-MX) motion data, respectively. Results: Pearson's correlation coefficients between the two methods were calculated, and significance tests were conducted (${\alpha}=1%$). Correlation coefficients between the two were over 0.98. In Vicon-MX and ImageJ, there is no systematic error by examination of the validity using the Bland-Altman method, and all data are in the 95% limits of agreement. Conclusion: In this study, correlation coefficients are generally high, and the regression line is near the identical line. Therefore, it is considered that motion analysis using ImageJ is a useful tool for evaluation of human movements in various research areas. Application: This result can be utilized as a practical tool to analyze human performance in various fields.

• 천문학회보
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• 제35권1호
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• pp.39.2-39.2
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• 2010

In this paper, I present the domestic development of near infrared camera systems for the ground telescope and the space satellite. These systems are the first infrared instruments made for astronomical observation in Korea. KASINICS (KASI Near Infrared Camera System) was developed to be installed on the 1.8m telescope of the Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. KASINICS is equipped with a $512{\times}512$ InSb array enable L band observations as well as J, H, and Ks bands. The field-of-view of the array is $3.3'{\times}3.3'$ with a resolution of 0.39"/pixel. It employs an Offner relay optical system providing a cold stop to eliminate thermal background emission from the telescope structures. From the test observation, limiting magnitudes are J=17.6, H=17.5, Ks=16.1 and L(narrow)=10.0 mag at a signal-to-noise ratio of 10 in an integration time of 100 s. MIRIS (Multi-purpose InfraRed Imaging System) is the main payload of the STSAT-3 in Korea. MIRIS Space Observation Camera (SOC) covers the observation wavelength from $0.9{\mu}m$ to $2.0{\mu}m$ with a wide field of view $3.67^{\circ}{\times}3.67^{\circ}$. The PICNIC HgCdTe detector in a cold box is cooled down below 100K by a micro Stirling cooler of which cooling capacity is 220mW at 77K. MIRIS SOC adopts passive cooling technique to chill the telescope below 200K by pointing to the deep space (3K). The cooling mechanism employs a radiator, a Winston cone baffle, a thermal shield, MLI of 30 layers, and GFRP pipe support in the system. Opto-mechanical analysis was made in order to estimate and compensate possible stresses from the thermal contraction of mounting parts at cryogenic temperatures. Finite Element Analysis (FEA) of mechanical structure was also conducted to ensure safety and stability in launching environments and in orbit. MIRIS SOC will mainly perform the Galactic plane survey with narrow band filters (Pa $\alpha$ and Pa $\alpha$ continuum) and CIB (Cosmic Infrared Background) observation with wide band filters (I and H) driven by a cryogenic stepping motor.