• Asian-Australasian Journal of Animal Sciences
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• 제28권5호
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• pp.620-631
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• 2015

A total of 59 lactic acid bacteria (LAB) strains were isolated from corn stover silage. According to phenotypic and chemotaxonomic characteristics, 16S ribosomal DNA (rDNA) sequences and recA gene polymerase chain reaction amplification, these LAB isolates were identified as five species: Lactobacillus (L.) plantarum subsp. plantarum, Pediococcus pentosaceus, Enterococcus mundtii, Weissella cibaria and Leuconostoc pseudomesenteroides, respectively. Those strains were also screened for antimicrobial activity using a dual-culture agar plate assay. Based on excluding the effects of organic acids and hydrogen peroxide, two L. plantarum subsp. plantarum strains ZZU 203 and 204, which strongly inhibited Salmonella enterica ATCC $43971^T$, Micrococcus luteus ATCC $4698^T$ and Escherichia coli ATCC $11775^T$ were selected for further research on sensitivity of the antimicrobial substance to heat, pH and protease. Cell-free culture supernatants of the two strains exhibited strong heat stability (60 min at $100^{\circ}C$), but the antimicrobial activity was eliminated after treatment at $121^{\circ}C$ for 15 min. The antimicrobial substance remained active under acidic condition (pH 2.0 to 6.0), but became inactive under neutral and alkaline condition (pH 7.0 to 9.0). In addition, the antimicrobial activities of these two strains decreased remarkably after digestion by protease K. These results preliminarily suggest that the desirable antimicrobial activity of strains ZZU 203 and 204 is the result of the production of a bacteriocin-like substance, and these two strains with antimicrobial activity could be used as silage additives to inhibit proliferation of unwanted microorganism during ensiling and preserve nutrients of silage. The nature of the antimicrobial substances is being investigated in our laboratory.

• Journal of Welding and Joining
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• 제30권1호
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• pp.59-63
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• 2012

The spacer grid is one of the main structural components in a fuel assembly. It supports fuel rods, guides cooling water and maintains geometry from external impact load and cyclic stress by the vibration of nuclear fuel rod, it is necessary to have sufficient strength against dynamic external load and fatigue strength. In this study, the mechanical properties and fatigue characteristics of laser beam welded zircaloy thin sheet are examined. The material used in this study is a zirconium alloy with 0.66 mm of thickness. The fatigue strength under cyclic load was evaluated at stress ratio R=0.1. S-N curves are presented with statistical testing method recommend by JSME- S002 and compared with S-N curves at R.T. and $315^{\circ}C$. As a result of the experimental approach, the design guide of fatigue strength is proposed and the results obtained from this study are expected to be useful data for spacer gird design.

• 수산해양기술연구
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• 제48권2호
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• pp.137-146
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• 2012

Black porgy and fat greenling are commercially important fish species due to the continuously increasing demand in Korea. When estimating acoustically the fish length by a fish sizing echo sounder, it is of crucial importance to know the target strength (TS) to length dependence. In relation to these needs, the target strength experiments for live fishes were conducted in an acrylic salt water tank using two split-beam echo sounders operating at 70 and 120kHz. The target strength under well-controlled laboratory conditions was simultaneously measured with the swimming movement by digital video recording (DVR) system and analyzed as a function of fish length (L) and frequency (or wavelength ${\lambda}$). Equations of the form TS-alog (L)+blog (1)+c were derived for their TS-length dependence. The best fit regression of TS on fork length for black porgy was TS=20.62 log (L, m)-0.62 log (${\lambda}$, m)-30.68 ($r^2$=0.77). The best fit regression of TS on fork length for fat greenling was TS=12.06 log (L, m)-5.85 log (${\lambda}$, m)-22.15 ($r^2$=0.44).

• 한국구조물진단유지관리공학회 논문집
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• 제2권1호
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• pp.136-141
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• 1998

It is demanded to obtain the design data for bond length of the strengthening carbon fiber sheets. An objectives of this study is to provide preliminary data of rational strengthening design method which is adequate to current domestic status. The present experimental study was performed to evaluate flexural strengthening effects of steel reinforced concrete beams strengthened with carbon fiber sheets. Following conclusions can be extracted. It is revealed that the maximum load carrying capacity is increased up to 9% when the reinforced concrete beams were strengthened with 1-ply of carbon fiber sheet which is half-width of beam. The performance of reinforced concrete sections were improved due to the strengthening carbon fiber sheets on the tensile side of beams. It is believed that the strengthening length of carbon fiber sheets must be provided as (0.5l+3d) to secure the ductile capacity of above three for the flexural strengthening of reinforced concrete beams.

• 한국세라믹학회지
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• 제33권2호
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• pp.203-213
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• 1996

In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

• Radiation Oncology Journal
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• 제24권4호
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• pp.280-284
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• 2006

목 적: 원자력의학원에 설치되어 있는 MC50 사이클로트론에서 생성되는 중성자선의 의학적 이용을 위하여 생물학적 특성을 평가하고자 하였다. 대상 및 방법: 35 MeV 양성자를 15 mm 베릴륨 표적에 부딪혀서 생성된 중성자선에 대하여 물리적 방사선선량을 측정한 후 체외실험(in-vitro)을 하였다. EMT-6 세포주(cell line)를 이용하여 $0{\sim}5\;Gy$의 중성자선을 조사 후 생존분획(surviving fraction)을 구하였다. 또한 감마선의 효과를 피하기 위하여 납차폐를 한 후에 동일 조건에서 생존분획을 구하였다. 엑스선 실험에서는 0, 2, 5, 10, 15 Gy를 조사 후 생존분획을 측정하였다. 결 과: MC50의 중성자선은 조사야 $26{\times}26\;cm^2$, 전류 $10{\mu}A$, 깊이 2 cm에서 84%의 중성자와 16%의 감마선으로 구성되어 있었고, 총선량률은 9.25 cGy/min이었다. 엑스선을 이용하여 측정한 생존분획곡선은 선형이차함수모델 (linear quadratic model)을 적용하였을 때 ${\alpha}/{\beta}$비는 0.611 (${\alpha}=0.0204,\;{\beta}=0.0334,\;R^2=0.999$)이었다. 중성자선에 있어서 생존분획곡선은 저선량 영역에서 어깨영역(shoulder area)을 가지고 있었고, 모든 실험에서 선형이차함수모델에 잘 맞았다. ${\alpha}$의 평균값은 -0.315 (범위, $-0.254{\sim}-0.360$)였고, ${\beta}$값은 0.247 (범위, $0.220{\sim}0.262$)이었다. 납차폐를 하였을 때에도 생존분획곡선에서 어깨영역은 없어지지 않았다. 중성자선의 RBE (relative biological effectiveness) 값은 생존분획이 0.1일 때 $2.07{\sim}2.19$ 범위였고, 0.01일 때 $2.21{\sim}2.35$였다. 결 론: MC50에서 생성된 중성자선은 상당량의 감마선을 내포하고 있으며 이것이 생존분획곡선에서 어깨영역이 나타나는 데에 기여하였을 것이다. MC50의 중성자선의 RBE 값은 약 2.2였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.743-747
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• 2003

The improvement of luminance and luminous efficiency is the one of the most important part in AC-PDPs. To achieve high luminance and luminous efficiency, high VUV emission efficiency is needed. We measured the emission spectra of vacuum ultraviolet(VUV) and infrared(IR) rays in surface discharge AC-PDP with Ne-Xe mixture gas. The influence of Ne-Xe gas-mixture ratio on resonance state $Xe^{\ast}(3P_{1})$ and exited state $Xe^{\ast}(3P_{2})$ has been investigated. It is found that the intensity of VUV 147nm emission is proportional to that of the IR 828 nm emission, and the VUV 173nm emission is roughly proportional to that of the IR 823nm emission. The electron temperature and plasma density have been experimentally measured from the center of sustaining electrode gap by a micro Langmuir probe in AC-PDPs. The plasma density from the center of sustaining electrode gap are shown to be maximum value of $9{\times}10^{11}cm^{-3}$, where the electron temperature is about 1.6 eV in this experiment

• 콘크리트학회논문집
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• 제29권2호
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• pp.201-208
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• 2017

외부 보-기둥 접합부에서는 철근정착을 위해 갈고리철근 사용하고 있으며, 철근과밀배근 해소와 시공작업의 어려움으로 확대머리철근의 사용이 증가하고 있다. SD600 51 mm 확대머리철근을 사용할 경우 ACI318-14 및 KCI2012기준에서 사용을 제한하고 있다. 이번 연구에서는 외부 보-기둥 접합부 내에 고강도 대구경 철근의 확대머리 철근의 사용이 가능하도록 실험 60 MPa, 80 MPa 콘크리트강도로 제작된 실험체의 정착상세별 구조성능을 평가하였다. 모든 실험체에서는 보의 휨항복파괴가 발생하였으며, 실험체의 모멘트-변위 곡선에서 비슷한 양상을 보였다. 다른 실험체보다 갈고리가 한쪽방향으로 배근한 실험체에서는 갈고리철근 배근방향에 의해 전단저항능력이 달라지므로 3.5%변위비 이후에 부착응력 감소가 더 크게 나타났으며, 전단변형능력도 더 크게 나타났다. 실험체의 내진성능을 확인하기 위하여 ACI374.1-05기준과 비교하였으며, 실험결과 충분한 내진성능을 확보하였다. 이를 통하여 외부 보-기둥 접합부에서 SD600, 51 mm 확대머리철근의 사용이 가능한 것으로 판단된다.

• 콘크리트학회지
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• 제9권5호
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• pp.225-231
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• 1997

콘크리트 압축강도 및 전단스팬비의 변화에 의한 고강도 철근콘크리트 춤이 큰 보의 전단거동 및 내력특성을 파악하기 위한 실험적 연구를 하였다. 춤이 큰 보는 하중작용점과 하중지지점을 연결하는 사균열의 확대에 의해 취성전단파괴양상을 나타내었으며 하중작용점 하중 지지점의 콘크리트 압괴를동반하는 전단압축 및 전단인장파괴 형태로 최종파괴되었다. 전단스팬비가 감소함에 따라 사균열전단응력 및 최대전단응력은 크게 증가하였으며, ACI 및 CIRIA규준식은 부재의 최대전단응력을 비교적 정확하게 예측하고 있음을 파악하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.63-66
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• 2004

Transparent MgO thin films were deposited on glass substrates by electron beam evaporation of MgO (99.99%) under $O_2$ atmosphere at 150-250 $^{\circ}C$. These films were characterized for their useful properties such as thickness, transmission, and refractive index using ultraviolet / visible (UV/VIS) spectrophotometer, scanning electron microscopy (SEM), and Spectroscopic Ellipsometry. The thickness of MgO films were measured by alpha step instrument and found to be 600 nm to 1000 nm and are meeting the stoichiometry. The transmission spectrum of these films shows transmittance values ${\sim}$92%..