• Journal of the East Asian Society of Dietary Life
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• v.8 no.4
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• pp.412-421
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• 1998

Physicochemical and microbiological properties of red beans, soybeans, barleys, and corns irradiated by gamma-ray at 1.2 kGy, 10.1 kGy, or 30.5 kGy were investigated. Moisture content and crude lipid content of the irradiated cereals showed no significant difference from the nonirradiated group. TBA values of corns irradiated at 30.5 kGy increased. Gamma irradiation reduced the numbers of mesophilic and psychrotrophic bacteria in the cereals. Yeasts and molds were reduced below detection levels even at 1.2 kGy dose-irradiation. There was no significant difference in reducing sugars between the irradiated cereals and the nonirradiated ones except corns. Stachyose, raffinose, and sucrose of soy beans and sucrose of barleys increased by 30.5 kGy dose-irradiation. Loss of riboflavin content of the irradiated samples was not observed except red beans irradiated at 30.5 kGy. In Hunter's color, b value of the red bean powder increased but L value of the soybean powder decreased by the Irradiation. L, a, and b values of the barley powder slightly increased under 30.5 kGy dose-irradiation and b value of the corn powder decreased under 10.1 or 30.5 kGy-dose irradiation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.778-779
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• 2016

In This paper, We designed the scintillation detector for measuring radiation signals in units of pixels for a radiation source that is distributed in the space. And we carried out a study to design a radiation imaging by the module for obtaining the detection signal. For measuring radiation distribution we configure a radiation detector combining CsI(Tl) scintillator and a photodiode. In addition, its performance was verified via gamma irradiation test.

• Journal of Sensor Science and Technology
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• v.18 no.5
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• pp.402-407
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• 2009

In this study, plastic optical fiber sensors which can measure thermal neutron dose in a mixed neutron-gamma field are developed and characterized. Using $^{252}Cf$ and $^{60}Co$ sources, the scintillators suitable for thermal neutron detection, are tested and the scintillating lights generated from a plastic optical fiber sensor in the Kyoto University Critical Assembly (kuca) core are measured. Also, the distributions of thermal neutron and gamma-ray are measured in a mixed field as a function of the distance from the center of the reactor core at KUCA and the distribution of thermal neutron is obtained using a subtraction method. Sensitivity of the fiber-optic radiation sensor system is about 0.49 V/mW according to power of the KUCA core and its relative error is about 1.2 %.

• Nuclear Engineering and Technology
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• v.52 no.5
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• pp.1029-1035
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• 2020

The detector suffers from pulse pileup by overlapping of the signals when it was used in high radiation fields. The pulse pileup deteriorates the energy spectrum and causes count losses due to random co-incidences, which might not resolve within the resolving time of the detection system. In this study, it is aimed to propose a new pulse pileup correction method. The proposed method is to correct the start point of the pileup pulse. The parameters are obtained from the fitted exponential curve using the peak point of the previous pulse and the start point of the pileup pulse. The amplitude at the corrected start point of the pileup pulse can be estimated by the peak time of the pileup pulse. The system is composed of a NaI (Tl) scintillation crystal, a photomultiplier tube, and an oscilloscope. A 61 μCi ¹³⁷Cs check-source was placed at a distance of 3 cm, 5 cm, and 10 cm, respectively. The gamma energy spectra for the radioisotope of ¹³⁷Cs were obtained to verify the proposed method. As a result, the correction of the pulse pileup through the proposed method shows a remarkable improvement of FWHM at 662 keV by 29, 39, and 7%, respectively.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2564-2571
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• 2022

SiPMs are generally coupled into whole columns in gamma energy spectrum measurement, but the relationship between the distribution of whole SiPM columns and the energy resolution of the measured energy spectra is rarely reported. In this work, ∅ 3 × 3 inch NaI scintillator is placed on an 8 × 8 SiPM array, and the energy resolution of the ¹³⁷Cs peak at 662 keV corresponding to the γ-ray is selected as a reference. Each SiPM is switched to explore the influence of the number of SiPM arrays, distribution position, and reflective layer on the energy resolution of SiPMs. Results show that without coupling, the energy resolution is greatly improved when the number of SiPMs ranges from 4 to 32. However, after 32 slices (the area covered by SiPMs relative to the scintillator reaches 25.9%), the improvement in energy resolution and total pulse count is not obvious. In addition, the position of SiPMs relative to the scintillator does not exert much impact on the energy resolution. Results also indicate that by adding a reflective film (ESR), the energy resolution of the tested group increases by 10.38% on average. This work can provide a reference for the design and application of miniaturized SiPM gamma spectrometers.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.559-563
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• 2015

Monitor of All-sky X-ray Image (MAXI) is a Japanese X-ray all-sky surveyer mounted on the International Space Station (ISS). It has been scanning the whole sky since 2009 during every 92-minute ISS rotation. X-ray transients are quickly found by the real-time nova-search program. As a result, MAXI has issued 133 Astronomer's Telegrams and 44 Gamma-ray burst Coordinated Networks so far. MAXI has discovered six new black holes (BH) in 4.5 years. Long-term behaviors of the MAXI BHs can be classified into two types by their outbursts; a fast-rise exponential-decay type and a fast-rise flat-top one. The slit camera is suitable for accumulating data over a long time. MAXI issued a 37-month catalog containing 500 sources above a ~0.6 mCrab detection limit at 4-10 keV in the region ${\mid}{b}{\mid}$ > $10^{\circ}$. The SSC instrument utilizing an X-ray CCD has detected diffuse soft X-rays extending over a large solid angle, such as the Cygnus super bubble. MAXI/SSC has also detcted a Ne emission line from the rapid soft X-ray nova MAXI J0158-744. The overall shapes of outbursts in Be X-ray binaries (BeXRB) are precisely observed with MAXI/GSC. BeXRB have two kinds of outbursts, a normal outburst and a giant one. The peak dates of the subsequent giant outbursts of A0535+26 repeated with a different period than the orbital one. The Be stellar disk is considered to either have a precession motion or a distorted shape. The long-term behaviors of low-mass X-ray binaries (LMXB) containing weakly magnetized neutron stars are investigated. Transient LMXBs (Aql X-1 and 4U 1608-52) repeated outbursts every 200-1000 days, which is understood by the limit-cycle of hydrogen ionization states in the outer accretion disk. A third state (very dim state) in Aql X-1 and 4U 1608-52 was interpreted as the propeller effect in the unified picture of LMXB. Cir X-1 is a peculiar source in the sense that its long-term behavior is not like typical LMXBs. The luminosity sometimes decreases suddenly at periastron. It might be explained by the stripping of the outer accretion disk by a clumpy stellar wind. MAXI observed 64 large flares from 22 active stars (RS CVns, dMe stars, Argol types, young stellar objects) over 4 years. The total energies are $10^{34}-10^{36}$ erg $s^{-1}$. Since MAXI can measure the spectrum (temperature and emission measure), we can estimate the size of the plasma and the magnetic fields. The size sometimes exceeds the size of the star. The magnetic field is in the range of 10-100 gauss, which is a typical value for solar flares.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.1024-1030
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• 2015

Safety and security system have been internationally enhanced in a field of shipping logistics. Accordingly, techniques for safety and security have been studied steadily. The need of portable radiation detection device is increasing by the search of the container is enhanced. In this paper, we propose a study to improve the life of the system and the realization of portable radiation detection device based on Cortex-A9. Configuration of a portable radiation detection device is configured largely to an analog board and the digital platform and the sensor module. The power used in each stage of the analog board is varied. Uses a switching regulator to use various power supply thereby to generate an error result and cause the switching noise. It is proposed to reduce the power consumption reducing technique for the study.

• Korean Journal of Food Science and Technology
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• v.42 no.2
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• pp.136-141
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• 2010

This study attempted to determine whether Photostimulated Luminescence (PSL) is applicable for the detection of post-irradiated foods by measuring the PSL photon counts of unirradiated and irradiated dried spices and herbs. A total of 19 dried spices and herbs was irradiated with a $^{60}Co$ $\gamma$-ray source at 1, 5 and 10 kGy followed by measurement of PSL photon. The photon counts of unirradiated samples below 700 correspond to negative. Fifteen samples irradiated over 1 kGy showed photon counts of more than 5,000, indicating irradiation treatment. Intermediate counts (photon count 700-5,000) were observed in irradiated white/black pepper, nutmeg and cinnamon bark at 10 kGy. These results suggest that it is possible to detect whether dried spices and herbs were irradiated by analyzing PSL, with the exception of white/black pepper, nutmeg and cinnamon bark. Irradiated white/black pepper, nutmeg and cinnamon bark containing low levels of minerals were not sensitive to PSL. Therefore, further investigation is sugguested to be performed by Thermoluminescence (TL) analysis or another validated or standardized method.

• Clean Technology
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• v.22 no.2
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• pp.122-131
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• 2016

Caesium radioisotopes, ¹³⁴Cs and ¹³⁷Cs which come from the atmospheric nuclear tests and discharges from nuclear power plants, are very important to study artificial radioactivity. In this work, in order to lower the minimum detection activity (MDA) we investigated environmental radioactivity according to the Environment Measurement Laboratory procedure by ¹³⁷Cs and ¹³⁴Cs which is similar to chemical and environmental behaviors of ¹³⁷Cs. The environmental soils in high mountain areas near nuclear power plant were collected, and an Ammonium Molybdophosphate (AMP) precipitation method, which showed high selectivity toward Cs⁺ ions, was applied to chemically extract and concentrate Caesium radioisotopes. Radioactivity was estimated by a gamma-ray spectrometry. In gamma energy spectrum, with an increasing of ⁴⁰K radioactivity, it increased the MDA of ¹³⁴Cs and ¹³⁷Cs. Therefore, if the natural radionuclides were removed from the soil samples, the MDA of Caesium may be reduced, and the contents of ¹³⁷Cs of in the environmental soils can effectively be estimated. In the standard soil sample of Korea Institute of Nuclear Safety, radioactivity of ⁴⁰K was removed more than 84% on average, and the MDA of ¹³⁴Cs was reduced 2 times. The content of ¹³⁷Cs was recovered over 84%. On the other hand, in environmental soils, AMP precipitation method showed removal ratio of ⁴⁰K up to 180 times, which reduced the MDA about 5 times smaller than those of Direct method. ¹³⁷Cs recovery ratio showed from 54.54% to 70.06%. When considering the MDA and recovery ratio, AMP precipitation method is effective for detection of Caesium radioisotopes in low concentration.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2729-2735
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• 2013

Safety and security system have been internationally enhanced in a field of shipping logistics. Accordingly, techniques for safety and security have been studied steadily. The need of portable radiation detection device is increasing by the search of the container is enhanced. In this paper, we propose to study on the application of the temperature compensation algorithm to the platform to improve the accuracy and the realization of portable radiation detection device based on Cortex-A9. Analog board deforms signal output from the sensor. And Cortex-A9 platform analyzes the signal received and displays the results. Additionally we use the temperature compensation algorithm and thereby we ca look the same results even if the temperature changes.