• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1052-1060
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• 2023

The airborne radiation monitoring has been used in geophysics for more than forty years and now it also has its important role in emergency monitoring. The aircraft background and the cosmic gamma-rays contribute to the measured gamma spectrum on the aircraft board. This adverse effect should be eliminated before the data processing. The paper describes two semiparametric methods to estimate the full spectrum aircraft background and cosmic gamma-ray contribution from spectra measured at altitudes where terrestrial contribution is negligible. The methods only assume to know possible peak positions in spectra and their full width at half maximum, that can be easily obtained e.g. from terrestrial measurement. The methods were applied to real experimental data acquired on Mi-17 and Bell 412 helicopter boards. The IRIS airborne gamma-ray spectrometer, with 4×4 L NaI(Tl) crystals, produced by Pico Envirotec Inc., Canada, was used on helicopters' boards. To obtain valid estimate of the aircraft background and the cosmic contribution, the measurements over sea and large water areas were carried out. However, the satisfactory results over inland were also achieved comparing with those acquired over large water areas.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.21 no.4
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• pp.543-558
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• 2023

Currently, Japan is undertaking a nationwide project to measure and map radioactive contamination around Fukushima, as part of the efforts to restore normalcy following the nuclear accident. The Japan Atomic Energy Agency (JAEA) manages the Fukushima Environmental Safety Center, located approximately 20 km north of the Fukushima Daiichi nuclear power plant in Minamisōma City, Fukushima Prefecture. In collaboration with the JAEA, this study involved conducting comparison experiments and analyses with radiation detectors in high radiation environments, a challenging task in Korean environments. Environmental radiation surveys were conducted using three types of detectors: CZT, NaI(Tl), and LaBr₃(Ce), across two contaminated areas. Dose rate values were converted using dose rate conversion factors for each detector type, and dose rate maps were subsequently created and compared. The detectors yielded similar results, demonstrating their feasibility and reliability in high radiation environments. The findings of this study are expected to be a crucial reference for enhancing the verification and supplementation of procedures and methods in future radiation measurements and mobile surveys in high-radiation environments, using these three types of radiation instruments.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.4
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• pp.380-388
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• 2024

This study investigated the sexual maturation of the marbled flounder Pseudopleuronectes yokohamae, a commercially important flatfish species, through monthly sampling from the coastal waters of Pohang in the East Sea of Korea in 2022. We analyzed monthly changes in total length (TL), gonadosomatic index, maturity stage, and 50%, 75%, and 97.5% group maturity based on visual assessments and histological analysis of the gonads. The spawning period was determined to be from December to May. The TL at 50% maturity was 26.4 cm for females and 24.8 cm for males. These findings provide a basis for developing resource management strategies for Pleuronectidae.

• Analytical Science and Technology
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• v.10 no.6
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• pp.395-402
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• 1997

The comparison study between EPA method 3050 and the test method offered by Ministry of Environment in Korea was performed to investigate a matrix effect on extraction. In this study, 12 inorganic priority pollutants(Cd, Cr, Cu, Pb, Ni, Zn, As, Sb, Se, Hg, Be, Tl) were spiked to the sludges and estuary sediment samples. The extracts were analyzed by AAS, HG-AAS, and ICP/MS. Results were discussed in terms of recoveries, relative standard deviations, and the method detection limits. Mean recovery of the elements except As, Sb, and Se was 93% when the procedure of EPA method was applied. The Korean extraction method, however. showed a significant matrix effect to give very poor recoveries.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05d
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• pp.840-843
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• 2002

본 논문에서는 전송계층에서의 안전한 통신을 위한 사실상의 표준으로서 자리를 잡고 있는 Secure Sockets Layer(SSL)와 Transport Layer Security(TLS)의 Handshake 프로토콜 취약성을 평가하기 위한 평가 도구를 제안한다. SSL/TLS Handshake 프로토콜 고유의 취약성과는 달리 구현 제품들에서의 문제점으로 인하여 보안성이 결여될 수 있다. 현재 SSL/TLS를 구현한 제품들이 다양하게 구현되어 있으나 구현과정에서 벤더나 프로그래머에 따라 SSL/TLS Handshake 프로토콜 고유의 취약성들이 다르게 표출될 수 있으므로 본 논문에서는 이들 구현제품들의 문제점으로 인한 보안성 결여를 평가하기 위한 도구를 개발한다.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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• pp.77-84
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• 1992

In the most of acoustic system with low flow rate and low pressure level, one-dimensional, linear modeling techniques are used very well. At low frequency, the tube is modeled as inertia element and cavity as capacitance element, and to extend the range of frequency normal mode oscillators are represented. Bond graph modelling techniques are proposed to predict TL (Transmission Loss) and time response which is impossible by transfer matrix in muffler system. A simple acoustic filter which consists of several tubes and cawities is analyzed in both time and frequency domain.

• Journal of the Korean Chemical Society
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• v.6 no.2
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• pp.155-157
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• 1962

A tiny dust found at the balcony of the Institute indicated about 8,0000 counts per minute by T.G.C.-2 Geiger-Muller tube (1.8mg/$cm^2$ window-thickness) at the distance of 2cm from the window. The main fission fragments, as identified by the present analysis, are 12.5day Ba-140 and 33.1 day Ce-141. The gamma energies were determined using $2"{\times}2"$ NaI(Tl) scintillation detector connected to RCL-256 channel pulse heigt analyzer. The beta energies were evaluated by Feather plot.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.503-506
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• 1999

Recently, as increasing population of internet, the larger one of required facts is solution for access speed, that transmission performance. ADSL system can provide the best application to resident in low cost, flexible approach. In this paper, for DMT line code that is one of ADSL modulation/demodulation signal processing methods, transmission performance and characteristic are discussed as studies and analysis through computer simulation using MATLAB. We made results with practising simulation using parameters based on ANSI standard Tl .413 Iusse2.

• Journal of radiological science and technology
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• v.36 no.4
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• pp.291-297
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• 2013

This study is aimed to evaluate the effect of $T_{1/2}$ upon count rates in the analysis of dynamic scan using NaI (Tl) scintillation camera, and suggest a new quality control method with this effects. We producted a point source with $^{99m}TcO_4^-$ of 18.5 to 185 MBq in the 2 mL syringes, and acquired 30 frames of dynamic images with 10 to 60 seconds each using Infinia gamma camera (GE, USA). In the second experiment, 90 frames of dynamic images were acquired from 74 MBq point source by 5 gamma cameras (Infinia 2, Forte 2, Argus 1). There were not significant differences in average count rates of the sources with 18.5 to 92.5 MBq in the analysis of 10 to 60 seconds/frame with 10 seconds interval in the first experiment (p>0.05). But there were significantly low average count rates with the sources over 111 MBq activity at 60 seconds/frame (p<0.01). According to the second analysis results of linear regression by count rates of 5 gamma cameras those were acquired during 90 minutes, counting efficiency of fourth gamma camera was most low as 0.0064%, and gradient and coefficient of variation was high as 0.0042 and 0.229 each. We could not find abnormal fluctuation in $x^2$ test with count rates (p>0.02), and we could find the homogeneity of variance in Levene's F-test among the gamma cameras (p>0.05). At the correlation analysis, there was only correlation between counting efficiency and gradient as significant negative correlation (r=-0.90, p<0.05). Lastly, according to the results of calculation of $T_{1/2}$ error from change of gradient with -0.25% to +0.25%, if $T_{1/2}$ is relatively long, or gradient is high, the error increase relationally. When estimate the value of 4th camera which has highest gradient from the above mentioned result, we could not see $T_{1/2}$ error within 60 minutes at that value. In conclusion, it is necessary for the scintillation gamma camera in medical field to manage hard for the quality of radiation measurement. Especially, we found a tendency that count rate changes over time at this study, and we proved that it can effect $T_{1/2}$. And also, there is need of appropriate phantoms and the method of quality management like this study, because there are not any advice or limitation degrees for domestic medical purpose scintillation camera.

• The Korean Journal of Nuclear Medicine
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• v.25 no.2
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• pp.165-176
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• 1991

The purpose of this study was to assess the ability of quantitative Tl-201 tomography to identify and localize coronary artery disease (CAD). The study population consisted of 41 patients (31 males, 10 females; mean age $55{\pm}7$ yr) including 14 with prior myocardial infarction who underwent both exercise Tl-201 myocardium SPECT and coronary angiography for the evaluation of chest pain. From the short axis and vertical long axis tomograms, stress extent polar maps were generated by Cedars-Sinai Medical Center program, and the % stress defect extent (SDE) was quantified for each coronary artery territory. For the purpose of this study, the coronary circulation was divided into 6 arterial segments, and the "myocardial ischemic score" (MIS) was calculated from the coronary angiogram. Sensitivity for the detection of CAD ($\geq50%$ coronary stenosis by angiography) by angiography) by stress extent polar map was 95% in single vessel disease, and 100% in double and triple vessel deseases. Overall sensitivity was 97%. Sensitivity and specificity for the detection of individual diseased vessels were, respectively, 87% and 90% for the left anterior descending artery (LAD), 36% and 93% for the left circumflex artery (LCX), and 71% and 70% for the right coronary artery (RCA). Concordance for the detection of individual diseased vessels between the coronary angiography and stress polar map was fair for the LAD (kappa=0.70), and RCA (kappa=0.41) lesions, whereas it was poor for the LCX lesions (kappa : 0.32). There were siginificant correlations between the MIS and SDE in LAD (rs=0.56, p=0.0027), and RCA territory (rs=0.60, p=0.0094). No significant correlation was found in LCX territory. When total vascular territories were combined, there was a significant correlation between the MIS and SDE (rs=0.42, p=0.0116). In conclusion, the quantitative analysis of Tl-201 tomograms appears to be accurate for determining the presence and location of CAD.