• 한국방사선학회논문지
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• 제18권2호
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• pp.65-71
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• 2024

소동물용 양전자방출단층촬영기기(positron emission tomography, PET)의 고분해능과 고민감도를 달성하기 위해 매우 가늘고 긴 섬광 픽셀을 사용하여 검출기를 구성한다. 이러한 섬광 픽셀의 구조로 인해 시스템의 관심 시야 외곽에서 공간분해능 저하 현상이 발생한다. 이를 해결하기 위해 반응 깊이를 측정하여 공간분해능을 향상시키고, 준블록 섬광체를 사용하여 민감도를 향상시킬 수 있는 검출기를 설계하였다. 12.6 mm x 12.6 mm x 3 mm 크기의 준블록 섬광체를 네 층으로 배열하고, 모든 옆면에 광센서를 배치하여 감마선과 섬광체가 상호작용하여 발생된 빛을 수집하도록 설계하였다. 설계한 검출기의 성능 평가를 위해 DETECT2000 시뮬레이션을 수행하였다. 각 층별 섬광체 내에서 1.3 mm부터 11.3 mm까지 1 mm 간격으로 감마선 이벤트를 발생시켜 평면 영상을 획득하였다. 11 x 11 배열의 평면 영상에서 각 위치별 공간분해능과 피크 간 거리를 측정하였다. 측정된 공간분해능의 평균은 0.25 mm였으며, 피크 간 거리의 평균은 1.0 mm였다. 이를 통해 모든 위치가 서로 분리됨을 확인할 수 있었다. 또한 모든 층은 빛의 신호가 서로 분리되어 측정되므로 감마선과 상호작용한 섬광체의 층을 완벽히 분리해낼 수 있었다. 설계한 검출기를 소동물용 PET 시스템의 검출기로 사용할 경우, 우수한 공간분해능과 민감도를 달성하여 영상의 질을 향상시킬 수 있을 것으로 판단된다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(4)
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• pp.73-76
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• 2000

A Scene Based Technique(SBT) that corrects linear array infrared detector's nonuniformity is proposed. Basically, this technique dispenses with using temperature references on a linear array infrared detector. To correct the nonuniformity of infrared images, we use three methods. Firstly, we detect bad channels by using the information which is cumulated all the same line pixels. Secondly, a variable window method is applied to compensate more accurately. Thirdly, an adaptive method which updates gain and offset coefficient is used only on a stationary region. These results are demonstrated on a computer simulation with various images. As a result, the nonuniformity is corrected completely, so that images are enhanced and PSNR(peak signal to noise ratio) is improved much.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.86-89
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• 1999

In this paper, we propose a new architecture of the fast symbol timing synchronization system which has some shared hardware blocks in order to reduce the hardware complexity. The proposed system consists of received power detector, correlation power detector using shared complex moving adders, and 2-step peak detector. Our system has detected FFT starting point within three Symbols using first two reference symbols of the frame in wireless ATM system. The new architecture was designed and simulated using VHDL. Our proposed architecture also detects a correct symbol timing synchronization within three symbols under a multi-path fading channel.

• ETRI Journal
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• 제27권4호
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• pp.377-384
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• 2005

We investigate near-infrared light (NIR) propagation in a model of an adult head using an extensive Monte Carlo (MC) simulation. The adult head model is a four-layered slab which consists of a surface layer, a cerebrospinal fluid layer, a gray-matter layer, and a white-matter layer. We study the effects of a refractive index mismatch on the model, calculating the intensity of detected light, mean flight time, and partial mean flight time of each layer for various refractive indices of the cerebrospinal fluid layer as functions of source-detector spacing. The Monte Carlo simulation shows that the refractive index mismatch presents very rich results including rapidly decaying intensity of detected light and a peak and cross-over in the partial mean flight time with source-detector spacing. We also investigate spatial sensitivity profiles at various source-detector spacings, discussing the index mismatch effect on the model.

• 한국환경보건학회지
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• 제27권1호
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• pp.88-92
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• 2001

The simultaneous analytical method for 37 residual pesticides was developed by a gas chromatography with $^{63}$ Ni electron capture detector. Pesticides added in soybean sample were extracted with 70% acetone in water and methylene chloride in oder, and then cleaned up via open-column apparatus packed with florisil and alumina N. The Ultra-2 fused capillary column was used to separate the products. The resolution between the last isomeric peak of cypermethrin (56.398 min) and the first isomeric peak of flucythrinate (56.421 min) was not satisfactory and the last isomeric peak of fenvalerate(58.783 min) and the first isomeric peak of fluvalinate(58.835 min) was overlapped. Except for $\alpha$-BHC, dichlofluanid, captan, and captafol, most recoveries were showed over 70%.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.459-460
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• 2008

In this paper, a 10Gbps clock and data recovery circuit is designed in $0.18{\mu}m$ CMOS technology. The circuit incorporates a multiphase LC oscillator, a quarter-rate Bang-Bang phase detector, a charge pump and a second order loop filter. The simulation results show that the designed circuit has a peak-to-peak clock jitter of 4.2ps and a peak-to-peak recovered data jitter of 8ps while consuming about 80mW from a 1.8V supply.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.197-198
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• 2007

In this paper, a 10Gbps Clock and Data Recovery circuit is designed in $0.18{\mu}m$ CMOS Technology. The circuit incorporates a multiphase LC oscillator, a quarter-rate Bang-Bang phase detector, a Charge Pump and a second order loop filter. The simulation results show that the designed circuit has a peak-to-peak clock jitter of 4.1ps and a peak-to-peak recovered data jitter of 8ps while consuming about 44mW from a 1.8V supply.

• Journal of Radiation Protection and Research
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• 제43권2호
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• pp.75-84
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• 2018

Background: Gamma-ray spectrometry helps in radiation shielding problems and different applications of radioisotopes. Experimental arrangements including broad beam geometries are widely used. The aim is to investigate and evaluate the ${\gamma}-ray$ spectra via attenuation by environmental materials. Materials and Methods: The photo peak to nominated parts in the ${\gamma}-ray$ spectra and the attenuation coefficients ${\mu}_b/{\rho}$ from broad beam geometries are measured for the materials water, soil, sand and cement at the energies 0.662, 1.25, and 1.332 MeV with a $3{^{\prime}^{\prime}}{\times}3{^{\prime}^{\prime}}$ NaI(Tl) detector. Results and Discussion: The ${\gamma}-ray$ spectra vary according to changes in the effective atomic number $Z_{eff}$ of the attenuator, the photon energy and the solid angle. The peak to total ratios are the most sensitive parts to variations in the experimental conditions and overturn in the region 0.663 MeV to 1.332 MeV. This is indicated as inversion trend. The results are discussed in view of $Z_{eff}$ and the experimental conditions. The intensity build-up is larger at the lower energy and larger scattering angles in agreement with Klein-Nishina formula and other results. The build-up factor B is$${\sim_=}$$1 at high ${\gamma}-energies$ and small scattering angles. Conclusion: The sensitivity to material characteristics decrease gradually from peak: to total, to Compton valley, to Compton plateau ratios. Rigorous collimation is necessary at small energies. Cement, of the largest $Z_{eff}$, is characterized by the maximum broad beam mass attenuation coefficients ${\mu}_b/{\rho}$. The obtained results provide information to decide for the suitable experimental set-up based on aim of the work.

• 대한디지털의료영상학회논문지
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• 제8권1호
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• pp.27-32
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• 2006

The rapid development in digital acquisition technology in radiography has not been accompanied by information regarding optimum radiolographic technique for use with an amorphus silicon flat panel detector. The purpose of our study was to compared imaging characteristics and image quality of an amorphus silicon flat panel detectors for digital chest radiography. All examinations were performed by using an amorphus silicon flat panel detector. Chest radiographs of an chest phantom were obtained with peak kilovoltage values of 60$\sim$150 kVp. Published data ell the effect of x-ray beam energy on imaging characteristics and image qualify when using an amorphus silicon flat panel detector. It is important that radiographers are aware of optimum kVp selection for an amorphus silicon flat panel detector system, particularly for the commonly performed chest examination.

• 한국방사선학회논문지
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• 제9권2호
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• pp.73-77
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• 2015

검출기의 자세한 구조를 알고자 CT 스캐닝을 하였으며 크리스털 형상과 사층에 관한 세부적인 구조를 전산모사 계산법을 이용해 재현하였다. 낮은 에너지의 감마선에 대한 피크 효율이 거리가 작아질수록 감소, 보다 높은 에너지(400 keV) 아상에서의 전체 효율성은 검출기 코어를 조정함으로써 불확도를 줄일 수 있었다. PENELOPE 계산법을 이용해 얻은 공간적 의존성 사이에 적절한 일치점이 달성되었음을 확인 하였다. 이는 크리스털 코어, 모서리와 크리스털 코어의 라운딩을 설명해 주는 매개변수들을 조정함으로써 달성되었다.