• Journal of Radiation Protection and Research
• /
• 제19권2호
• /
• pp.147-156
• /
• 1994

환경감마선량 변동을 감시하기 위해 한국원자력연구소 부지 주변에 온라인 감마선량 감시망을 구성하였다. 모니터링 포스트에 설치된 전리함 검출기에 의해 측정된 자료는 무선전송 방식으로 중앙동제소에 전송되어 실시간으로 감시된다. 무선전송 방식은 자료의 전송, 처리 및 저장에 신뢰도가 높고 경제적이었다. 감시시스템은 급격한 선량증가시 조기경보체제와 연결할 수 있게 하였다.

• 전기학회논문지
• /
• 제59권5호
• /
• pp.996-1000
• /
• 2010

In order to apply VLC (visible light communication) in harsh environment of nuclear power plant in-containment building, the high luminance LEDs, which are key components of the VLC system, have been gamma irradiated at the dose rate of 4 kGy/h during 72 hours up to a total dose of 288 kGy. The radiation induced coloration effect in the high luminance LED bulb made of acryl or plastic material was observed. In the VLC wireless data transmission experiment using the high luminance LEDs irradiated by high dose rate gamma-ray, the radiation induced coloration effect of the high luminance LED bulb extended the communication distance compared to non-irradiated LEDs.

• Nuclear Engineering and Technology
• /
• 제38권4호
• /
• pp.383-390
• /
• 2006

Having its roots in medical applications, industrial gamma ray CT has opened up new roads far investigating and modeling industrial processes. Using a line of research related to industrial gamma ray CT, the authors set up a system of single source and detector gamma transmission tomography for wood timber and a packed bed phantom. The hardware of the CT system consists of two servo motors, a data logger, a computer, a radiation source and a radiation detector. One motor simultaneously moves the source and the detector for a parallel beam scanning, whereas the other motor rotates the scan table at a preset projection angle. The image is reconstructed from the measured projections by the filtered back projection method. The phantom was designed to simulate a cross section of a packed bed with a void. The radiation source was 20mCi of Cs-137 and the detector was a 1 inch $\times$ 1 inch NaI (TI) scintillator shielded by a lead collimator. The experimental gamma ray CT image has sufficient resolution to reveal air holes and the density distribution inside the phantom. The system could possibly be applied to a packed bed column or a pipe flow in a petrochemical plant.

• Current Optics and Photonics
• /
• 제4권1호
• /
• pp.1-8
• /
• 2020

We research a system of compressed-sensing computational ghost imaging (CSCGI) based on the intensity fluctuation brought by turbulence. In this system, we used the gamma-gamma intensity-fluctuation model, which is commonly used in transmission systems, to simulate the CSCGI system. By setting proper values of the parameters such as transmission distance, refractive-index structure parameter, and sampling rates, the peak signal-to-noise ratio (PSNR) performance and bit-error rate (BER) performance are obtained to evaluate the imaging quality, which provides a theoretical model to further research the ghost-imaging algorithm.

• 방사선산업학회지
• /
• 제7권2_3호
• /
• pp.115-119
• /
• 2013

The density profile measurement technology by gamma transmission has been widely used to diagnose processes in the field of refinery and petrochemical industry. This technology can reveal a clue and position of abnormal phenomenon of industrial processes during their operation. In this paper, the feasibility of the gamma transmission technology for detecting changes in the amount of fluid in a distillation column was evaluated by using Monte Carlo simulations. The simulations assumed that $^{60}Co$ (1.17, 1.33 MeV) sources and NaI (Tl) detectors (${\Phi}5{\times}5cm$) are located in opposite sides of a column and it concurrently moves in vertical direction. To determine the dependency of a spatial resolution on aperture size of a collimator, the simulation model for a tray in a column were simulated with the aperture sizes of 1 and 2 cm. The thickness of the high density area including a tray and fluid was 7.6 cm in the simulation. The spatial resolution of the tray was 8.2 and 8.5 cm, respectively. As a result, it was revealed that the conventional density profile measurement technique is not able to show the deviation of liquid level on a tray in a column.

• 열처리공학회지
• /
• 제19권5호
• /
• pp.249-256
• /
• 2006

Structural studies have been performed on precipitation hardening found in $L1_2$ ordered ${\gamma}^{\prime}-Ni_3(Al,Ti)$ alloys using transmission electron microscopy. A uniform solid solution of ${\gamma}^{\prime}-L1_2$ ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The ${\gamma}^{\prime}$ phase hardens appreciably by the fine precipitation of disordered ${\gamma}$. The shape of ${\gamma}$ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the ${\gamma}$ precipitates are perfectly coherent with the matrix ${\gamma}^{\prime}$ as long as the ${\gamma}$-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the ${\gamma}/{\gamma}^{\prime}$ interface followed by the step formation at the dislocations. The ${\gamma}$ precipitates become globular after the loss of coherency. The strength of ${\gamma}^{\prime}-Ni_3(Al,Ti)$ increases over the temperature range of experiment by the precipitation of fine ${\gamma}$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature.

• Journal of Ceramic Processing Research
• /
• 제20권4호
• /
• pp.363-371
• /
• 2019

In this study, physical properties of normal concrete, magnetite concrete, EAF concrete, and EAF concrete with added iron powder were evaluated and a feasibility of radiation shielding is also evaluated through irradiation tests against X-rays and gamma-rays. While the unit weight of EAF concrete (3.21 t/㎥) appeared lower than that of magnetite concrete (3.50 t/㎥), the results in compressive strength of EAF concrete were greater than those in magnetite and normal concrete. While the radiation transmission rate of normal concrete reaches 26.0% in the X-ray irradiation test, only 6.0% and 9.0% of transmission rate were observed in magnetite concrete and linear relationship with unit volume weight and radiation shielding. In the gamma-ray irradiation test, the performance of EAF and magnetite concretes appeared to be similar. Through the results on the excellent physical properties and radiation shielding performance a potential applicability of EAF concrete to radiation shielding was verified.

• Journal of electromagnetic engineering and science
• /
• 제10권4호
• /
• pp.270-275
• /
• 2010

In a conventional opportunistic transmit (COT) cooperative relaying system, only the relays that receive signal-to-noise ratio (SNR) from the source and that exceed the threshold transmit to the destination. The COT system, however, only considers the SNR of the source-relay (S-R) path regardless that the SNR of the relay-destination (R-D) path is the opportunistic transmission condition. For that reason, it is not guaranteed that all the transmitted signals from relays exceed the threshold at the destination. Therefore we propose a double opportunistic transmit (DOT) cooperative relaying system - when both of the received SNR from a source and from a destination exceed the threshold, the relay transmits to the destination. It is shown that the proposed DOT system reduces power consumption by 6.9, 20.9, 32.4, and 41.4 % for K =3, 5, 7, and 9, respectively under the given condition of $P_{out}=1{\times}10^{-3}$ and $\overline{\gamma}_{SR}/\Gamma_{SR}$=30 dB, compared to the COT system. We noticed that the performance of the DOT system is superior to that of the COT system for the identical number of active transmit relays under the same condition of the normalized average SNR of $\overline{\gamma}_{RD}/\Gamma_{RD}$.

• 열처리공학회지
• /
• 제22권1호
• /
• pp.8-15
• /
• 2009

Structural studies have been performed on precipitation hardening found in $Ni_{3}Al$ based ordered alloys using transmission electron microscopy (TEM). Tilt experiments by the weak-beam method were made to obtain some information concerning the cross slip mechanism of the superlattice dislocation. The strength of ${\gamma}'-Ni_3$(Al,Ti) increases over the temperature range of experiment by the precipitation of fine $\gamma$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature. Over the whole temperature range, the interaction between dislocation and $\gamma$ precipitates is attractive. On the temperature range of 773 K to 973 K, the dislocations in ${\gamma}'$ matrix move on (111) primary slip plane. When the applied stress is removed, the dislocations make cross slip into (010) plane, while those in $\gamma$ precipitates remain on the (111) primary slip plane. The increase of high temperature strength in ${\gamma}'-Ni_3$(Al,Ti) containing $\gamma$ precipitates is due to the restraint of cross slip of dislocations from (111) to (010) by the dispersion of disordered $\gamma$ particles.

• 분석과학
• /
• 제6권5호
• /
• pp.515-520
• /
• 1993

Rene 80 주조블레이드가 고온에서 사용중인 사용 온도에 의해 ${\gamma}^{\prime}$이라는 석출물이 기지(${\gamma}^{\prime}$) 내에서 생성되기 때문에 고온강도는 그 석출물에 좌우된다. 즉, 석출물의 격자상수는 기지의 격자상수보다 크기 때문에 석출물이 생성되거나 성장할 때에 ${\gamma}-{\gamma}^{\prime}$ 격자어긋남(lattice misfit)에 의해 전위가 발생한다고 일반적으로 알려져 있다. 이러한 격자어긋남은 석출물(${\gamma}^{\prime}$)의 크기가 클수록 원형${\rightarrow}$사각형${\rightarrow}$판상형으로 바뀌어 가면서 증가한다. 따라서 본 연구에서는 이러한 격자어긋남의 양을 주사투과전자현미경에서 수렴성 빔전자 회절(CBED)을 사용하여 측정하여, 석출물과 인접한 기지의 전위밀도의 증가가 기지 내에서 석출물이 생성하고 성장함에 따른 격자어긋남이 원인인가를 관찰하였다.