• Progress in Superconductivity
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• v.10 no.1
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• pp.29-34
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• 2008

Magnesium diboride ($MgB_2$) is an inexpensive and simple superconductor. This material was first synthesized and its structure confirmed in 1953 but its superconducting properties were not discovered until 2001 when they caused great excitement. In this study, superconducting $MgB_2$ thin films on the r-$Al_{2}O_3$ substrates have been grown by the combination of radio frequency magnetron sputtering of B and thermal evaporation of Mg. The deposition conditions were varied by changing deposition rate. Before the co-deposition of Mg and B, the deposition rates of each element have been measured separately. The $MgB_2$ layers had 400nm in thickness and superconducting transition temperatures have been measured around $\sim$38.6K. Superconducting properties have been measured by PPMS, XRD, and SEM.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.520-520
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• 2009

Organic by-products derived from cellulose and lignin during organosolv pretreatments of yellow poplar wood (Liriodendron tulipifera) in the presence of $H_2SO_4$ and NaOH as catalysts, respectively, were subjected to various analyses to elucidate their effects on further performance of biological ethanol fermentation and provide preliminary data for the structure and utilization of organosolv lignin. Monomeric sugars amounted to ca. 2.2-7.7% in the organosoluble fraction of the organosolv pretreatment with $H_2SO_4$, while significantly low amount of sugars (0.2-0.3%) were determined in that of the organosolv pretreatment with NaOH. In case of addition of $H_2SO_4$ during organosolv pretreatment of biomass, a fermentation of the organosoluble fraction could be considered as an essential process to increase an efficiency of biomass utilization as well as yield of bioethanol. Precipitates, insoluble by-products in the solvent mixture, were also cficiency oed by diverse analytical methods and revealed that these were typically composed of a lignin moiety regardless of catalyst. According to the results of nuclear magnetic resonance (NMR), Fourier Tcinsform Infrared Spectroscopy (FT-IR) and Gel permeation chromatograp r (GPC), the main components of precipitates seem to be lignin polymers. However, their structures could be slightly modified during pretreatment and mixed with some carbohydrates by chemical bonds and/or physical associations.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.156-164
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• 2003

STS316L had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue behaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of STS316L weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characteristics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.1 no.1
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• pp.47-53
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• 2003

An electrochemical reduction technology which can reduce the decay heat, volume, and radioactivity of spent fuel by a factor of quarter through converting oxide type spent fuel to a metallic form in a molten salt was developed and tests in a scale of g (3- 40g $U_{3}O_{8}$ batch) have been carried out by Korea Atomic Energy Research Institute. In this research, the reaction apparatus in a scale of 5kg $U_{3}O_{8}$ batch was designed and manufactured for the mock-up test to obtain design data of the apparatus which will be used for the hot test in a scale of 20kg $U_{3}O_{8}$ batch. The electrochemical reduction behavior of $U_{3}O_{8}$ was analyzed regarding the operational factors and fresh $U_{3}O_{8}$ powder was metallized with a more than 99% yield verifying the process validity of electrochemical reduction process in a kg scale.

• 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.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.3
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• pp.24-30
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• 1993

The necessity of ultrasonic inspection to detect the cracks in turbine blade is being increased as the forced outage of nuclear power plants have been occurred due to blade failure in turbine components. However, the complex blade root geometry causes the ultrasonic inspection technique not to be established yet and much effort is required to set up a more reliable inspection. In this paper, the ultrasonic inspection technique for flaw detectability, skew angle effect, identification of flaw and geometric signal have been investigated with a test block and discussed the interpretation of ultrasonic signal through the acquisition and analysis of RF waveform. The experimental results show that the proper examination procedure can be established. It is required that the skew angle is essential to decrease the effect of signals from the complex blade geometry. The present results of this study can be applied to the site inspection without blade disassembly.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.35-41
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• 2012

This paper proposes a new methodology for the real-time on-line quality monitoring of biofuel processes through the integration of infrared spectroscopy and chemometrics. A method of Partial Least Squares (PLS) in Chemometrics is employed for quantitative analysis of key components in bioethanol products. After a number of preprocessing methods and variable importance in projection (VIP) are used, Savitzky-Golay method showed the best performance in terms of spectrum correction, noise reduction, and model maintenance. The proposed method allows us to economically forecast the concentration of multiple impurities encountered with the production of bioethanol. The proposed system is also accurate enough ($R^2$ > 0.99) to replace the laboratory analysis.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.297-301
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• 2012

Microbial fuel cell (MFC) is the major of bio-electrochemical system which can convert biomass spontaneously into electricity through the metabolic activity of the microorganisms. In this study, we used an activated sludge as a microbial inoculum and then investigated the feasibility of using dairy wastewater as a possible substrate for generating electricity in MFC. To examine the performance of MFC as power generator, the characteristics on cell potentials, power density, cyclic voltammetric analysis and sustainable power estimation were evaluated for dairy wastewater. The maximum power density of $40\;mW/m^2$was achieved when the dairy wastewater containing 2650 mg/L COD was used, leading to the removal of 88% of the COD. The results from this study demonstrate the feasibility of using MFC technology to generate electricity while simultaneously treating dairy wastewater effectively.

• Journal of Korean Society of societal Security
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• v.1 no.3
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• pp.69-76
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• 2008

The object of this study is to develop a tool for quantifying risks related to the rail transportation of hazardous commodities and to present mitigation measures. In this study, the Quantitative Risk Assessment (QRA) is used as a risk analysis tool. Based on the previous explosion history (Iri explosion) and consideration of its high risk, Iksan-si is selected as a model city. The result, expressed as average individual risk for exposed people with various distance, indicates that the model city is considered to be safe according to the nuclear energy standard. Also, the mitigation measures are provided since Societal risk of Iksan-si is set within ALARP. Risk reduction measures include rail car design, rail transportation operation, demage spread control as well as derail prevention and alternative routes for reducing accident frequencies. Finally, it is expected to achieve high level of public safety by appling the risk reduction measures.

• Journal of Korea Foundry Society
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• v.33 no.6
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• pp.233-241
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• 2013

Effect of Fe and Mn contents on the castability of Al-9wt%Si-xMg-yFe-zMn alloy has been studied. The alloy was composed of ${\alpha}$-Al phase, Al+eutectic Si phase, ${\beta}$-Al5FeSi compound and chinese script ${\alpha}$-$Al_{15}(Mn,Fe)_3Si_2$ compound. ${\beta}$-$Al_5FeSi$ and ${\alpha}$-$Al_{15}(Mn,Fe)_3Si_2$ compounds assumed to effect the fluidity and shrinkage behaviors of the alloy during solidification due to the crystallization of ${\alpha}$-$Al_{15}(Fe,Mn)_3Si_2$ and ${\beta}$-$Al_5FeSi$ compounds above eutectic temperature. As Fe and Mn contents of Al-9wt%Si-0.3wt%Mg system alloy increased from 0.15wt% to 0.6wt% and from 0.3wt% to 0.7wt%, fluidity of the alloy decreased by 5.7% and 3.3%, respectively. And as Mg content of Al-9wt%Si-0.45wt%Fe-0.5wt%Mn system alloy increased from 0.3wt% to 0.4wt%, fluidity of the alloy decreased by 8.6%. When Fe content of the alloy increased from 0.15wt% to 0.6wt%, macro shrinkage ratio decreased from 6.1% to 4.1%, and micro shrinkage ratio increased from 0.04% to 0.24%. Similarly, Mn content of the alloy increased from 0.3wt% to 0.7wt%, macro shrinkage ratio decreased from 6.0% to 4.5% and micro shrinkage ratio increased from 0.12% to 0.18%. Judging from the castability of the alloy, Al-9wt%Si-0.3wt%Mg alloy with low content of Fe and Mn, 0.1wt% Fe and 0.3wt% Mn, is recommendable.