• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.203-216
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• 1994

The laboratory methods for compaction of soil (KSF 2312) and for moisture of soil (KSF 2306) in combination with the soil density in place by the sand-cone method (KSF 2311) are generally used for compaction control of soils. However, these methods have limitations in number of test and in accuracy. ]n addition, they are time-consuming. Therefore, they are not adequate for speedy control of embankment compaction in a project with huge amount of earthwork. The RI (Radioisotope) gauges for measurement of soil density and/or of soil moisture are widely used for the compaction control of soils in many countries. But in Korea, they have had a limited usage and available informations for uses of RI gauges are insufficient. Therefore, this study promotes efficient and safe use of RI gauges in geotechnical engineering. In this paper, fundamental aspects such as the priciples of RI gauges, gauge inspection techniques and the applicability and limitations of RI gauges for field usage were reviewed. And a new calibration curves suitable for the Korean soils were suggested.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.537-537
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• 2013

Cyclotron-accelerated ion beams are used for various researches, such as nuclear physics, nuclear chemistry, biotechnology, and material sciences including radio-isotope production. Recently considerable applications are asked to the cyclotron development undertaken to meet user requirements of various ions'energies, intensities, and their pulsed beams. For instance, a cocktail beam acceleration technique rapidly changing the ion species and energies was developed to irradiating integrated circuit chips. Also a chopping system in a cyclotron injection line is considered for producing a pulsed ion beam with a relatively long period compared with that generated by the resonance frequency. For the research in neutron time-of-flight measurement, a single-pulsed beam with a repetition interval of the order of mili-seconds or longer is necessary to have a good resolution and to remove background events. In this paper a feasibility of pulsed beam with an external ion source is simulated by adopting a combination system of a chopper accompanying with a bunching stage in the injection line and an additional chopper after the exit of the cyclotron in order to produce beam pulses with a range of $1{\mu}s{\sim}1ms$ periods from a resonance RF cycle. The pulseperiod will be adjusted by chopping the number of beam bunches from the injected pulses in the injection line. However, the longer pulses will have reduced number of beam pulses and sacrificed beam currents. Because the beam users need an intense single pulsed beam, a careful tuning of the acceleration phase and a high-intense external ion source are necessary to achieve an intense single-pulsed beam from the cyclotron. It is essential to strictly match the acceleration phase of injected beams in the central region of the cyclotron to improve its efficiency. An effect of space charge at each pulse from the ion source will be also considered.

• Journal of the Korean Society of Groundwater Environment
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• v.1 no.1
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• pp.6-9
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• 1994

Previously reported Ar/N$_2$ratios in groundwater have been measured by single ion monitoring (Barnes et al., 1975; Vogel et al., 1981; Mariotti et al., 1988). The detector geometry and flared flight tube in VG Optima isotopic ratio mass spectrometer appeared to be fortuitously aligned for the simultaneous measurement of Ar/N$_2$ratios. Method development included mechanical adjustments to optimize the mass spectrometer for Ar/N$_2$ratio measurements followed by development of a preparation system for the extraction of air-saturated water samples. Samples containing known Ar/N$_2$ratios were used to assess accuracy and precision, and to test the applicability of methods for measurements of aqueous Ar/N$_2$ratios. The results indicated that the prepared air-saturated water samples were almost identical to the predicted Ar/N$_2$ratios (p ＜0.001). Groundwater samples were collected from on-going research sites, Shelton and Grand Island, Nebraska. Samples from the Grand Island sludge injection site form a lower boundary for worldwide reported Ar/N$_2$ratios. These lower Ar/N$_2$ratios can be explained by the production of nitrogen gas from this site, where denitrification was reported previously.

• BMB Reports
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• v.43 no.11
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• pp.761-765
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• 2010

Salivary testosterone levels in Korean adults were quantitatively measured for the first time by liquid chromatography-electrospray-tandem mass spectrometry (LC ESI MS/MS). Salivary testosterone was separated on a multiple reaction monitoring (MRM) chromatogram within 7 min. The LC ESI MS/MS assay was validated over the linearity range of 0.01-2.00 ng/ml (r=0.99987) using testosterone-$d_3$ as an internal standard. The lower limit of quantification (LOQ) was 0.01 ng/ml. The intra- and inter-assay precisions were 1.54% to 4.09% and 0.96% to 4.29%, respectively. The mean recovery was 93.32% (range 88.43-98.05%). The validated assay was then applied to measure the salivary testosterone levels of Korean adults. In men, the salivary testosterone level collected between 9：00-11：00 am was approximately 2.8 times higher than that in women (P < 0.0001). Salivary testosterone levels in both sexes negatively correlated with age. The present assay would also be useful in measuring salivary testosterone levels in clinical laboratories.

• Journal of radiological science and technology
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• v.43 no.5
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• pp.375-382
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• 2020

PET/CT is a medical equipment that detects 0.511 MeV of gamma rays. The radiation workers are inevitably exposed to ionizing radiation in the process of handling the isotope. Accordingly, PET/CT workers use syringe shields made of lead and tungsten to protect their hands. However, lead and tungsten are known to generate very high scattering particles by interacting with gamma rays. Therefore, in this study, we tried to find out the effect on the scattering particles emitted from the syringe shield. In the experiment, first, the exposure dose to the hand (Rod phantom) was evaluated according to the metal material (lead, tungsten, iron, stainless steel) using Monte Carlo simulation. The exposure dose was compared according to whether or not plastic is attached. Second, the exposure dose of scattering particles was measured using a dosimeter and lead. As a result of the experiment, the shielding rate of plastics using the Monte Carlo simulation showed the largest difference in dose of about 40 % in lead, and the lowest in iron, about 15 %. As a result of the dosimeter test, when the plastic tape was wound on lead, it was found that the reduction rate was about 15 %, 28 %, and 39 % depending on the thickness. Based on the above results, it was found that 0.511 MeV of gamma ray interacts with the shielding tool to emit scattered rays and has a very large effect on radiation exposure. However, it was considered that the scattering particles could be sufficiently removed with plastics with a low atomic number. From now on, when using high-energy radiation, the shielding tool and the skin should not be in direct contact, and should be covered with a material with a low atomic number.

• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.837-846
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• 2014

A lead slowing down spectrometer (LSDS) is under development for analysis of isotopic fissile material contents in pyro-processed material, or spent fuel. Many current commercial fissile assay technologies have a limitation in accurate and direct assay of fissile content. However, LSDS is very sensitive in distinguishing fissile fission signals from each isotope. A neutron spectrum analysis was conducted in the spectrometer and the energy resolution was investigated from 0.1eV to 100keV. The spectrum was well shaped in the slowing down energy. The resolution was enough to obtain each fissile from 0.2eV to 1keV. The detector existence in the lead will disturb the source neutron spectrum. It causes a change in resolution and peak amplitude. The intense source neutron production was designed for ~E12 n's/sec to overcome spent fuel background. The detection sensitivity of U238 and Th232 fission chamber was investigated. The first and second layer detectors increase detection efficiency. Thorium also has a threshold property to detect the fast fission neutrons from fissile fission. However, the detection of Th232 is about 76% of that of U238. A linear detection model was set up over the slowing down neutron energy to obtain each fissile material content. The isotopic fissile assay using LSDS is applicable for the optimum design of spent fuel storage to maximize burnup credit and quality assurance of the recycled nuclear material for safety and economics. LSDS technology will contribute to the transparency and credibility of pyro-process using spent fuel, as internationally demanded.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.29 no.1
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• pp.33-41
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• 2007

Bone scan using radioactive isotope can be more effective than conventional X-ray radiograph for finding jaw lesion because it takes an image of the physiologic change of bone. This study is designed to show how available bone scan is able to diagnose jaw lesion better than simple X-ray and CT, as well as to determine a basis of diagnosis for jaw lesion using bone scan. The 77 patients, visiting the Oral & Maxillofacial Surgery, Department of Dankook University Hospital from January 2002. to August 2005. who were diagnosed histopathologically with postoperative malignant tumor, osteomyelitis, and bone infiltrative benign disease. Preoperative X-ray, CT, bone scan were taken and were compared with histopathologic finding. Also to compare specificty of each lesion in bone scan, bone density was measured to compare. The results were as follows. 1. Among the 25 cases of oral malignant tumor of bony invasion, a positive diagnosis associated with histopathologic evaluation, 22 cases(88%) in bone scan, 14 cases(56%) in CT image, and 10 cases40%) in simple X-ray. 2. Among the 31 cases of osteomyelitis, a positive diagnosis associated with histopathologic evaluation, 30 cases(97%) in bone scan, 23 cases(74%) in CT image, and 19 cases(61%) in simple X-ray. 3. Among the 11cases of bone infiltrative benign disease, a positive diagnosis associated with histopathologic evaluation, 11 cases(100%) in bone scan, 10 cases(91%) in CT image, and 6 cases(55%) in simple X-ray. 4. Measurement of bone density in each group showed no statistical significant difference between malignant tumor and osteomyelitis as well as benign bone disease. But, a statistical significance was seen between osteomyelitis and benign bone disease. From this results, bone scan are more sensitive than simple X-ray and CT image in jaw lesion diagnosis, but specificity shows no significant difference. Therefore, it should be suggested that evaluation of bone scan must be carrying out in reference to final histopathologic diagnosis.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1263-1268
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• 2018

Three different ice core samples from Antarctica were analyzed to identify activity concentrations of radioactive isotopes. Tracking migration of radioactive isotopes to Antarctica can provide a key clue to understand global environmental changes caused by radiation exposures because the Antarctic ice cores can preserve unique characteristics of various environmental conditions. We are particularly interested in the $^{137}Cs$ nucleus, because it is closely related to radiation exposure from nuclear power plant accidents and nuclear bomb tests. With its half life of $30.17{\pm}0.03$ years, $^{137}Cs$ can also be used to assess the age of sedimentation occurring after around the year 1945. We selected three ice core samples, called Tarn8, Styx27, and H25, from different time periods; the Tarn8 sample is known to be from earlier than ~ 1000 AD, the Styx27 sample is approximately from the year 1945, and the H25 sample is from the year 2012. Radioactive isotope measurements of the ice core samples were performed using a 100% HPGe detector at Cheongpyeong Underground Radiation Laboratory (CURL). We measured the activity of $^{137}Cs$ in the H25 sample to be $0.98{\pm}0.82mBq/kg$. Although the activity has a large uncertainty mainly due to the limited sample quantity, the $^{137}Cs$ isotopes in the Antarctic ice core were measured for the first time in Korea.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.176-189
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• 2019

This paper presents a feasibility study for producing the medical isotope $^{99m}Tc$ using the hazardous and currently wasted radioisotope $^{99}Tc$. This can be achieved with the nuclear resonance fluorescence (NRF) phenomenon, which has recently been made applicable due to high-intensity laser Compton scattering (LCS) photons. In this work, 21 NRF energy states of $^{99}Tc$ have been identified as potential contributors to the photo-production of $^{99m}Tc$ and their NRF cross-sections are evaluated by using the single particle estimate model and the ENSDF data library. The evaluated cross sections are scaled using known measurement data for improved accuracy. The maximum LCS photon energy is adjusted in a way to cover all the significant excited states that may contribute to $^{99m}Tc$ generation. An energy recovery LINAC system is considered as the LCS photon source and the LCS gamma spectrum is optimized by adjusting the electron energy to maximize $^{99m}Tc$ photo-production. The NRF reaction rate for $^{99m}Tc$ is first optimized without considering the photon attenuations such as photo-atomic interactions and self-shielding due to the NRF resonance itself. The change in energy spectrum and intensity due to the photo-atomic reactions has been quantified using the MCNP6 code and then the NRF self-shielding effect was considered to obtain the spectrums that include all the attenuation factors. Simulations show that when a $^{99}Tc$ target is irradiated at an intensity of the order $10^{17}{\gamma}/s$ for 30 h, 2.01 Ci of $^{99m}Tc$ can be produced.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1393-1398
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• 2018

In conventional single-photon emission computed tomography (SPECT), only the photoelectric events in the detectors are used for image reconstruction. However, if the $^{131}I$ isotope, which emits high-energy radiations (364, 637, and 723 keV), is used in nuclear medicine, both photoelectric and Compton scattering events can be used for image reconstruction. The purpose of our work is to perform simulations for Compton SPECT by using the Geant4 application for tomographic emission (GATE). The performance of Compton SPECT is evaluated and compared with that of conventional SPECT. The Compton SPECT unit has an area of $12cm{\times}12cm$ with four gantry heads. Each head is composed of a 2-cm tungsten collimator and a $40{\times}40$ array of CdZnTe (CZT) crystals with a $3{\times}3mm^2$ area and a 6-mm thickness. Compton SPECT can use not only the photoelectric effect but also the Compton scattering effect for image reconstruction. The correct sequential order of the interactions used for image reconstruction is determined using the angular resolution measurement (ARM) method and the energies deposited in each detector. In all the results of simulations using spherical volume sources of various diameters, the reconstructed images of Compton SPECT show higher signal-to-noise ratios (SNRs) without degradation of the image resolution when compared to those of conventional SPECT because the effective count for image reconstruction is higher. For a Derenzo-like phantom, the reconstructed images for different modalities are compared by visual inspection and by using their projected histograms in the X-direction of the reconstructed images.