• 한국ITS학회 논문지
• /
• 제11권5호
• /
• pp.103-115
• /
• 2012

본 논문에서는 임펄스를 방사하기 위한 IR-UWB용 테이퍼 슬롯 안테나(Tapered Slot Antenna: TSA) 설계와 성능평가에 대해 연구하였다. UWB 대역에서 지향성 특성을 갖는 테이퍼 슬롯 안테나는 낮은 방사손실과, 임펄스 방사왜곡이 최소이어야 한다. 이를 위해 광대역 임피던스 변환기와 마이크로스트립-슬롯라인 천이부 구조를 갖는 테이퍼 슬롯 안테나 급전부를 설계하였다. 설계 및 제작된 테이퍼 슬롯 안테나는 전파 무반사실에서 방사패턴을 측정하였으며, 임펄스 방사에 따른 시간영역 특성을 평가하기 위해 펄스충실도 및 왜곡율 수식을 유도하였다. 제작된 테이퍼 슬롯 안테나의 임펄스 방사에 의한 펄스충실도는 ${\pm}30^{\circ}$ 빔폭 내에서 약 93% 이상의 양호한 결과를 얻었다.

• Nuclear Engineering and Technology
• /
• 제53권8호
• /
• pp.2646-2651
• /
• 2021

A rectangular-shaped PET system with an adjustable gantry (AGPET) has been developed for imaging small animals. The AGPET system employs a new depth of interaction (DOI) method using a depth dependent reflector patterns and a new digital time pickoff method based on the pulse reconstruction method. To evaluate the performance of the AGPET, timing resolution, intrinsic spatial resolution and point source images were acquired. The timing resolution and intrinsic spatial resolution were measured using two detector modules and Na-22 gamma source. The PET images were acquired in two field of view (FOV) sizes, 30 mm and 90 mm, to demonstrate the characteristic of the AGPET. As a result of in the experiment results, the timing resolution was 0.9 ns using the pulse reconstruction method based on the bi-exponential model. The intrinsic spatial resolution was an average of 1.7 mm and the spatial resolution of PET images after DOI correction was 2.08 mm and 2.25 mm at the centers of 30 mm and 90 mm FOV, respectively. The results show that the proposed AGPET system provided higher sensitivity and resolution for small animal imaging.

• 전자공학회논문지
• /
• 제50권8호
• /
• pp.299-307
• /
• 2013

본 논문에서는 임펄스 방사를 위한 UWB 안테나를 펄스 충실도 및 왜곡율 수식을 유도하고 적용하여 펄스 충실도가 개선된 안테나를 설계하는 방법에 대해 연구하였다. UWB 대역에서 지향성 특성을 갖는 안테나는 낮은 방사손실과, 임펄스 방사왜곡이 최소이어야 한다. 이를 위하여 광대역 임피던스 변환기와 마이크로스트립 슬롯라인 천이부 구조를 갖는 안테나 급전부를 설계하였다. 설계 및 제작된 UWB 안테나는 전파 무반사실에서 방사패턴을 측정하였다. 제작된 UWB 안테나의 임펄스 방사에 의한 펄스충실도는 ${\pm}30^{\circ}$ 빔폭내에서 93%이상의 개선된 결과를 얻었다.

• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.56-63
• /
• 2024

In high radiation fields, gamma cameras suffer from pulse pile-up, resulting in poor energy resolution, count losses, and image distortion. To overcome this problem, various methods have been introduced to reduce the size of the aperture or pixel, reject the pile-up events, and correct the pile-up events, but these technologies have limitations in terms of mechanical design and real-time processing. The purpose of this study is to develop a real-time gamma camera to evaluate the radioactive contamination in high radiation fields. The gamma camera is composed of a pinhole collimator, NaI(Tl) scintillator, position sensitive photomultiplier (PSPMT), signal processing board, and data acquisition (DAQ). The pulse pile-up is corrected in real-time with a field programmable gate array (FPGA) using the start time correction (STC) method. The STC method corrects the amplitude of the pile-up event by correcting the time at the start point of the pile-up event. The performance of the gamma camera was evaluated using a high dose rate ¹³⁷Cs source. For pulse pile-up ratios (PPRs) of 0.45 and 0.30, the energy resolution improved by 61.5 and 20.3%, respectively. In addition, the image artifacts in the ¹³⁷Cs radioisotope image due to pile-up were reduced.

• 한국정보통신학회:학술대회논문집
• /
• 한국정보통신학회 2012년도 춘계학술대회
• /
• pp.869-871
• /
• 2012

고도의 과학기술발전으로 인해 일상생활에서 전자기기의 사용이 급속도로 늘어가고 있다. 또한 태양의 흑점 폭발이나 북한의 핵폭탄, 원전 사고 등으로 인해 방사선에 대한 관심도가 증가하고 있다. 태양으로부터 방출되는 펄스형태의 방사선은 전자장비에 장애를 초래하며 특히 핵폭발 시 전달되는 고준위 펄스 방사선의 경우 전자부품에 오동작 및 불용상태로 까지 영향을 미칠 수 있다. 이러한 방사선 영향에 대한 연구는 국내외에서 다양하게 진행되고 있다. 본 논문에서는 이러한 전자 부품에 영향을 줄 수 있는 펄스방사선 탐지를 위해 Si 기반의 포토다이오드를 제작하고 이를 통해 펄스 입출력 신호에 대한 회로 시뮬레이션과 일반 광원을 이용한 출력 특성을 연구하였다. 본 연구의 결과는 고 에너지의 펄스 방사선 영향으로부터 전자회로를 보호하기 위한 추가적인 모듈의 입력 센서로 활용 될 수 있다.

• 전기학회논문지
• /
• 제59권9호
• /
• pp.1611-1614
• /
• 2010

The explosion of a nuclear weapon radiates a gamma-ray in the form of a transient pulse. If the gamma-ray introduces to semiconductor devices, much Electron-Hole Pairs(EHPs) are generated in depletion region of the devices[7]. as a consequence of that, high photocurrent is created and causes upset, latchup and burnout of semiconductor devices[8]. This phenomenon is known for Transient Radiation Effects on Electronics(TREE), also called dose-rate effects. In this paper 3D structure of inverter and NAND gate device was designed and transient pulse gamma-ray was modeled. So simulation for transient radiation effect on inverter and NAND gate was accomplished and mechanism for upset and latchup was analyzed.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.518-519
• /
• 2006

A connection between pulse-periodical laser radiation power and stability of liquid-metal contacts between powder particles during selective laser sintering (SLS) is determined based on analysis solving the problem of stability of liquid column in the gravity and capillary forces field. On the grounds of obtained relationships the optimization of pulse-periodical laser radiation power and SLS-process duration is realized, that allows to produce voluminous powder porous materials with pre-determined physical and mechanical properties and surface geometry. Results of metallographic investigations of powder porous materials of titanium powder produced with technological regimes calculated by means of obtained relationships are given in the work

• Nuclear Engineering and Technology
• /
• 제27권5호
• /
• pp.784-791
• /
• 1995

방사선계측에서는 방사선검출기(detector)로부터 나오는 pulse를 처리하는 데 있어서 pulse의 counting 손실이 발생한다. 이 손실을 최소화하거나 보상하기 위한 여러가지 방법들이 제시되어 왔으나, 아직도 절대적인 해답이 확립되지 않은 실정이다. 본 연구에서는 기 제시된 보상알고리즘들을 그 기능을 구현하는 전자회로와 함께 기술하고 특징을 분석하였다. 또한 본 연구를 통해 pulse의 counting손실을 보상하는 한가지 알고리즘 개선방향을 제시하였다.

• 전기학회논문지
• /
• 제62권4호
• /
• pp.517-522
• /
• 2013

The spurious electromagnetic radiation is generated due to the RF unbalanced current on a conductive cable connecting an electronic device to another. A metamaterial-based filtering geometry with frequency selectivity is suggested to reduce the radiation with a bandgap structure, where the right-handed inductance and capacitance stem from the transmission-like configuration between the cable and the metal protrusion, and the left-handed components come from the narrow cavities. The effect of the structure on the unbalanced current pulse and its spurious radiation is presented in the FDTD-method frame work.

• Journal of the Optical Society of Korea
• /
• 제13권1호
• /
• pp.86-91
• /
• 2009

The electrons injected into a laser wakefield undergo betatron oscillation and give rise to the emission of intense X-ray radiation. To investigate the generation conditions of the X-rays, the relativistic motion of an electron injected in an off-axis position has been simulated with wakefield profiles which are pre-calculated with a two-dimensional particle-in-cell code. The wakefield with a plasma density of $1.78{\times}10^{18}\;cm^{-3}$ is generated by the laser with an intensity of $1.37{\times}10^{18}\;W/cm^2$ and a pulse width of 30 fs. From the calculation of the single particle motion, the characteristics of the betatron radiation are investigated in the time domain. As the transverse injection position increases, the power and the duration time of the radiation increase, but the width of each pulse decreases.