• Journal of Korean Society of Environmental Engineers
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• v.27 no.1
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• pp.85-92
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• 2005

The performance of a novel fermentation process, adopting a sludge blanket type configuration for higher hydrolysis/acidogenesis of the municipal primary sludge, was investigated under batch and semi-continuous conditions with various pH and temperature conditions. This acid elutriation slurry reactor provided higher system performance with a short HRT (5 days) and higher acidogenic effluent quality under pH 9 and thermophilic ($55^{\circ}C$) conditions. The hydrolysis of the sludge was revealed to be significantly dependent on seasonal effects for sludge characteristics but with little impact on acidogenesis. Based on the rainy season at the optimum conditions, VFA production and recovery fraction ($VFA_{COD}/COD$) were $0.18\;g\;VFA_{COD}\;g^{-1}\;VSS_{COD}$ and 63%. As byproducts, nitrogen and phosphorus releasing were $0.006\;g\;N\;g^{-1}\;VSS_{COD}$ and $0.003\;g\;P\;g^{-1}\;VSS_{COD}$, respectively. For the mass balance in a full-scale plant($Q=158,880\;m^3\;day^{-1}$) based on the rainy season, the VFA and non-VFA(as COD) production were $3,110\;kg\;VFA_{COD}\;day^{-1}$ and $1,800\;kg\;COD\;day^{-1}$, resulting in an increase of organics of $31\;mg\;COD\;L^{-1}$ and $20\;mg\;VFA_{COD}\;L^{-1}$ and nutrients of $0.7\;mg\;N\;L^{-1}$ and $0.3\;mg\;P\;L^{-1}$ in the influent sewage. The economical benefit from this process application was estimated to be about $67 per $1,000m^3$ of sewage except for energy requirements and also, better benefits can be expected during the dry season. Also, the results revealed that the process has various additional advantages such as pathogen-free stabilized solids production, excellent solids control and economical benefits.

• Journal of Life Science
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• v.27 no.10
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• pp.1145-1151
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• 2017

In this study, we report on a simple, efficient method for obtaining penicillin G amidase (PGA) from recombinant Escherichia coli using a formulation mixed with detergent and lysozyme. Research was conducted on the extraction efficiency of PGA from the periplasmic space in cells in terms of the type of detergent, detergent concentration, pH, reaction time, and temperature of permeabilization. The extraction yield of PGA in the formulated surfactant/lysozyme treatment was increased by approximately (55-65 U/ml) in comparison with that in the single surfactant treatment. The released PGA solution was concentrated and exchanged with buffer using an ultrafiltration (U/F) system. The yields of diatomite filtration, membrane filtration (M/F), and U/F were 69.7%, 93.8%, and 77.3%, respectively. A total of 212 KU of PGA was recovered. At the 25-L culture scale, the overall yield of extraction using the mixed surfactant/lysozyme method was 49.2%. The specific activity of extracted PGA was 11 U/mg in protein. The concentrated PGA solution was immobilized on microporous silica beads without further purification of PGA. The total immobilization yield of PGA on the resin was 48.7%, while the enzyme activity was 101 U/g. The immobilized PGA was successfully used to produce 6-APA from penicillin G. Our results indicated that a simple extraction method from periplasmic space in E. coli may be used for the commercial scale production of ${\beta}-lactam$ antibiotics using immobilized PGA.

• Journal of the Korean Society of Radiology
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• v.13 no.5
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• pp.819-824
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• 2019

In this study, we proposed a method for identifying isotopes generated from high-energy proton $^{nat}Pb$(p,xn) nuclear reactions through the difference of gamma rays generated through nuclear reactions using different proton energies. The experiment was performed by using a high energy proton generated from a 100 MeV proton linear accelerator of the Korea Atomic Energy Research Institute. Gamma rays generated by various nuclides generated through proton nuclear reactions were measured using a gamma-ray spectroscopy system composed of HPGe detectors. Gamma-ray standard sources were used for accurate energy calibration and efficiency measurements of HPGe gamma-ray detectors. For the proposed method, 100 and 60 MeV proton energy beams were used for the same natural lead samples. This method was found to be very effective in identifying nuclides produced by comparing gamma rays generated from the same sample with each other. The results of this study are expected to be very effective in obtaining other proton nuclear reaction results in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.1
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• pp.28-31
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• 2015

Electromotive forces (EMF) are generated by electrical equipment and engine shafting with a number of reasons. The shaft and bearing which is insulated by lubricating oil acts as a condenser, being able to store this EMFs. The electromotive force on the hull and shaft, with very few exceptions, has anode voltage on it. Electrical spark of the anode voltage on the shaft may lead to corrosion. Hence, in order to prevent ship's shaft and propeller corrosion, shaft grounding system are installed and operated. The shaft EMF voltage measurement methods was measured using 24bit 2 channels A/D converter of NI company and Labview software. 1 channel was propeller shaft's voltage and the other was M/E engine rpm gauge. In this paper, the generated electromotive force was analyzed and modeled with result of the analysis. As a result, the main shaft's electromotive force was in direct proportion to the main engine's revolution. However, over the specific R.P.M., it was reduced gradually. In addition, higher electromotive force on the shaft was identified during engine's ahead direction than the astern direction. The generated electromotive force is only minor compared to the shaft grounding system.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.209.1-209.1
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• 2012

TUS(Tracking Ultraviolet Setup)는 5x1019 eV 이상의 초고에너지 우주선의 스펙트럼과 그 기원, 그리고 고층대기 극한방전 현상(TLE) 관측을 위한 우주망원경이다. 위성 Lomonosov의 탑재체로 2013년에 발사예정에 있으며 지구로부터 550km 상공에서 지구를 돌며 3년 이상 임무를 수행할 예정이다. TUS는 크게 반사경과 Detector Module 두 부분으로 나뉜다. 7개의 육각형 프레넬 거울을 이용한 $2m^2$ 크기의 반사경과 256개의 PMT(Photo Multiplier Tube)로 구성된 Detector Module을 이용하여 지구 대기에서 초고에너지 우주선에 의해 발생하는 UV fluorescence와 Cherenkov light를 관측한다. TUS Detector Module의 한 부분인 Pinhole Camera는 본 연구단의 기술로 직접 개발한 탑재체로서 TUS 반사경을 통하지 않고 두개의 $8{\times}8$ 어레이 MAPMT (Multi Anode PMT)가 직접 지구를 바라보며 고층대기 극한방전 현상을 관측한다. Pinhole camera는 TUS의 시야각을 포괄하는 넓은 시야각을 가지고 있으며 빠른 트리거 시스템으로 고층대기 극한 방전 현상을 관측하며, 이 방전현상과 TUS가 관측하는 초고에너지 우주선과의 상관 관계를 연구한다. 현재 TUS 및 Pinhole Camera는 러시아에서 조립되어 우주환경 인증 시험 및 인터페이스 테스트가 진행되고 있다. 본 발표에서는 TUS와 Pinhole Camera를 소개하고 현재까지의 진행상황 및 테스트 결과에 대해 보고하고자 한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.301-301
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• 2011

최근 고밀도 메모리 반도체의 재료와 빠른 응답을 요구하는 나노입자를 이용한 비휘발성 메모리 소자의 제작에 대한 연구가 활발히 진행되고 있다. 그에 따른 기존의 플래쉬 메모리가 가지는 문제점을 개선하기 위해서 균일하고 규칙적으로 분포하는 새로운 나노소재의 개발과 비휘발성, 고속 동작, 고집적도, 저전력 소자의 공정기술이 요구되고 있다. 또한 부유게이트에 축적되는 저장되는 전하량을 증가시키기 위한 새로운 소자구조 개발이 필요하다. 한편, 실리 사이드 계열의 나노입자는 금속 나노입자와 달리 현 실리콘 기반의 반도체 공정에서 장점을 가지고 있다. 따라서 본 연구에서는 화합물 중에서 비휘발성 메모리 장치의 전기적 특성을 향상 시킬 수 있는 실리사이드 계열의 바나듐 실리사이드(V3Si) 박막을 열처리 과정을 통하여 수 nm 크기의 나노입자로 제작하였다. 소자의 제작은 p-Si기판에 실리콘산화막 터널층(5 nm 두께)을 건식 산화법으로 성장 후, 바나듐 실리사이드 금속박막을 RF 마그네트론 스퍼터 시스템을 이용하여 4~6 nm 두께로 터널 베리어 위에 증착하고, 그 위에 초고진공 마그네트론 스퍼터링을 이용하여 SiO2 컨트롤 산화막층 (20 nm)을 형성시켰다. 여기서 V3Si 나노입자 형성을 위해 급속 열처리법으로 질소 분위기에서 800$^{\circ}C$로 5초 동안 열처리하여 하였으며, 마지막으로 열 기화 시스템을 통하여 알루미늄 전극(직경 200 ${\mu}m$, 두께 200 nm)을 증착하여 소자를 제작하였다. 제작된 구조는 금속 산화막 반도체구조를 가지는 나노 부유게이트 커패시터이며, 제작된 시편은 투사전자현미경을 이용하여 나노입자의 크기와 균일성을 확인했다. 소자의 전기적인 측정을 E4980A capacitor parameter analyzer와 Agilent 81104A pulse pattern generator system을 이용한 전기용량-전압 측정을 통해 전하저장 효과 및 메모리 동작 특성들을 분석하고, 열처리 조건에 따라 형성되는 V3Si 의 조성을 엑스선 광전자 분광법을 이용하여 확인하였다.

• The Journal of Engineering Geology
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• v.21 no.2
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• pp.163-178
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• 2011

A test borehole was drilled in the Cheongwon area to investigate the relationship between geochemical environment and the natural occurrence of radioactive materials (uranium and Rn-222) in borehole groundwater. The borehole encountered mainly biotite schist and biotite granite, with minor porphyritic granite and basic dykes. Six groundwater samples were collected at different depths in the borehole using the double-packed system. The groundwater pH ranges from 5.66 to 8.34, and the chemical type of the groundwater is Ca-$HCO_3$. The contents of uranium and Rn-222 in the groundwater are 0.03-683 ppb and 1,290-7,600 pCi/L, respectively. The contents of uranium and thorium in the rocks within the borehole are 0.51-23.4 ppm and 0.89-62.6 ppm, respectively. Microscope observations of the rock core and analyses by electron probe microanalyzer (EPMA) show that most of the radioactive elements occur in the biotite schist, within accessory minerals such as monazite and limenite in biotite, and in feldspar and quartz. The high uranium content of groundwater at depths of -50 to -70 m is due to groundwater chemistry (weakly alkaline pH, an oxidizing environment, and high concentrations of bicarbonate). The origin of Rn-222 could be determined by analyzing noble gas isotopes (e.g., $^3He/^4He$ and $^4He/^{20}Ne$).

• Journal of the Society of Cosmetic Scientists of Korea
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• v.47 no.2
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• pp.155-161
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• 2021

This study was attempted to investigate natural materials with antimicrobial activity and to apply as natural preservatives in cosmetics. The disc diffusion method was used to search for nine species of natural antibacterial material for three species of skin pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa) and Candida albicans. As a result of measuring the size of inhibition zone, Rhus Semialata gall (Gallnut) extract, Oak vinegar, and ε-polylysine were showed strongest antibacterial activities (> 10 mm). The Minimum Bactericidal Concentration (MBC) of gallnut and oak vinegar ranged from 10 to 20 mg/mL and from 20 to 40 mg/mL against five human skin pathogens. The MBC of ε-polylysine ranged from 0.5 to 2 mg/mL in fungus. The synergic effect of gallnut extract/oak vinegar mixture and gallnut extract/ε-polylysine mixture were evaluated by checkerboard test. Compared to when used alone, the MBC of gallnut extract/oak vinegar mixture were at 4 times lower concentration against E. coli, C. albicans, and A. brasiliensis. Also Furthermore, the MBC of gallnut extract/ε-polylysine mixture were at 4 times lower concentration against C. albicans and A. brasiliensis. It was confirmed that the combination of gallnut extract with oak vinegar or ε-polylysine resulted in synergistic antibacterial effect against three human skin pathogens. Thus, it is expected that gallnut extract and natural product mixture can not only demonstrate antibacterial synergies, but also be applied in cosmetics as a natural preservative system with a wide antibacterial spectrum.

• Journal of Animal Environmental Science
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• v.16 no.2
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• pp.99-108
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• 2010

The principal objective of this study was to investigate the cooling effects of geothermal heat pump system (GHPS) in farrowing house. A total of 96 sows were allocated to 2 pig housings (GHPS and conventional housing) with 48 for four weeks in summer season. During the experimental period of four weeks, the highest outside temperature observed was approximately $34.1^{\circ}C$, GHPS decrease indoor temperature of pig housing up to $30.9^{\circ}C$, but conventional pig housing was similar to outside temperature. Dust concentrations (maximum 61.4%) of particulate matter less than $10{\mu}m$ (PM 10) in GHPS-housing were lower than the conventional housing. GHPS showed no signigicant difference in carbon dioxide emission, whereas the ammonia gas concentration was significantly decreased in GHPS-housing compared to that of conventional housing. Sows in GHPS-housing showed significantly lower respiratory rate than those of the control group. GHPS did not affect hormone level, litter size and birth weight, but weaning weight of piglets was influenced by GHPS. Feed consumption of sows was significantly increased in GHPS-housing compared to the conventional hosing. These results suggest that GHPS decrease dust concentration, ammonia gas emission and indoor temperature of pig housing and may affect performance in sows and weaned piglets.

• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.33-44
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• 2009

Water curtain of an underground LPG storage cavern is a facility to prevent leakage of high pressure gases, for which groundwater should flow freely towards the cavern and groundwater level also must be stably maintained. In this study, in order to evaluate qualities of seepage water and surrounding groundwater of an underground LPG storage cavern in Yeosu, 4 rounds of samplings, field measurements and laboratory analyses (February, May, August, October of 2007) were conducted. According to field measurements, pH was weak acidic to neutral but it gradually increased with time. Electrical conductivity (EC) of groundwater near a salt stack showed very high values between 10.47 and 38.50 mS/cm. Dissolved oxygen (DO) showed a very wide range of 0.20~8.74 mg/L and a mean of oxidation-reduction potential (ORP) was 159 mV, which indicated an oxidized condition. Levels of $Fe^{2+}$ and $Mn^{2+}$ were mostly less than 3 mg/L. All of seepage waters showed a Na-Cl type while only groundwater near the salt stack showed a Na-Cl type with a high total dissolved solid. The other groundwaters exhibited typical $Ca-HCO_3$ types. Levels of aerobic bacteria were mostly very high (573-39,520 CFU/mL). Based on the analyses of these hydrochemistry and biological characteristics, it is concluded that there are no particular problems in groundwater and seepage water, which not causing a trouble in the cavern operation. However, both for control of bio-clogging and for sustainable operation of the water curtain system, a regular hydrochemical and microbiological monitoring is required for the seepage water and surrounding groundwater.