• Journal of Korean Society for Atmospheric Environment
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• 제22권E1호
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• pp.35-43
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• 2006

Ambient particle size distributions of PCBs and their dry deposition fluxes were measured at a site in Seoul to quantify dry deposition fluxes of PCBs and size characteristics of PCBs in the air, and to estimate ambient concentrations of gaseous PCBs and dry deposition fluxes. The dry deposition plate was used to measure dry deposition fluxes of particulate mass and PCBs and a cascade impactor and rotary impactor were used to measure ambient particle size distributions for small ($D_p<9{\mu}m$) and large ($D_p>9{\mu}m$) particles, respectively. Six sample sets were collected from April to July 1999. The fluxes of particulate total PCBs (the sum of 43 congeners) ranged from 160 to $607ng\;m^{-2}day^{-1}$. The size distribution of total PCBs was bimodal with two peaks in small particle size ($D_p{\sim}0.6\;and\;6{\mu}m$, respectively) and, thus, mass concentration being dominant in small particles. The mean particulate PCBs concentration was $6.9{\mu}g$ PCBs/g. The concentrations of PCB homologues in the gas phase were estimated based on the particle/gas partition coefficient ($K_p$) with the measured values of particulate PCBs in this study and they were comparable to those observed in other previous studies. Dry deposition fluxes were estimated by calculating dry deposition velocities.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.169-182
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• 2014

High-performance research reactors require fuel that operates at high specific power to high fission density, but at relatively low temperatures. Research reactor fuels are designed for efficient heat rejection, and are composed of assemblies of thin-plates clad in aluminum alloy. The development of low-enriched fuels to replace high-enriched fuels for these reactors requires a substantially increased uranium density in the fuel to offset the decrease in enrichment. Very few fuel phases have been identified that have the required combination of very-high uranium density and stable fuel behavior at high burnup. U-Mo alloys represent the best known tradeoff in these properties. Testing of aluminum matrix U-Mo aluminum matrix dispersion fuel revealed a pattern of breakaway swelling behavior at intermediate burnup, related to the formation of a molybdenum stabilized high aluminum intermetallic phase that forms during irradiation. In the case of monolithic fuel, this issue was addressed by eliminating, as much as possible, the interfacial area between U-Mo and aluminum. Based on scoping irradiation test data, a fuel plate system composed of solid U-10Mo fuel meat, a zirconium diffusion barrier, and Al6061 cladding was selected for development. Developmental testing of this fuel system indicates that it meets core criteria for fuel qualification, including stable and predictable swelling behavior, mechanical integrity to high burnup, and geometric stability. In addition, the fuel exhibits robust behavior during power-cooling mismatch events under irradiation at high power.

• 한국식품저장유통학회지
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• 제21권5호
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• pp.676-687
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• 2014

본 연구에서는 천일염, 정제염, 해양심층수염을 사용하여 제조한 절임배추의 냉장저장($0^{\circ}C$) 중 품질변화 및 시판제품과의 품질특성을 비교 조사하였다. pH의 경우 저장기간 전반적으로 S, R, D 구가 CS, CR, CD 구에 비해 높았고, 적정산도는 저장기간 전반적으로 CS, CR, CD 구가 S, R, D 구에 비해 높았다. 수분함량은 저장기간이 경과할수록 삼투압 작용에 의하여 모든 실험군에서 감소하였고, 염도는 S, R, D 구가 2.0~2.6%로 CS, CR, CD 구(0.9~1.8%)에 비해 저장기간 동안 유의적으로 높았다. 총균수 및 유산균수는 CS, CR, CD 구가 저장 1주 이후부터 급격히 증가하여 저장기간 동안 S, R, D 구에 비해 유의적으로 높게 나타나 pH 및 적정산도의 변화에 영향을 주었다. 경도와 씸힘성의 경우 모든 실험군에서 저장기간이 경과함에 따라 감소하였고 저장기간 동안 해양심층수염으로 제조한 절임배추(D)의 경도가 다른 실험군에 비해 유의적으로 높게 나타났다. 유리아미노산 총량은 CD 구가 가장 높았고 D 구가 가장 낮았으며, 필수아미노산의 비율은 소금의 종류에 따른 큰 차이를 보이지 않았지만, 비필수아미노산의 비율은 해양심층수염으로 제조 된 시판제품이 가장 높았다. 유기산 총량은 CD 구가 가장 높았고 해양심층수염으로 제조한 D와 정제염으로 제조한 R 구가 가장 낮았다. 무기질 총함량의 경우에도 CD 구가 실험군 중 가장 높았고, D, S, R, CR, CS 순으로 낮게 나타났다. K와 Mg 함량은 해양심층수염으로 제조한 D 구가 실험군 중 가장 높았고, Na 함량은 CD구가 가장 높았다. 관능적 외관, 산미 및 전체적 기호도는 모든 실험군에서 저장기간이 경과함에 따라 감소하였으나 해양심층수염으로 제조한 절임배추(D)의 외관, 산미 및 전체적 기호도는 저장기간 동안 다른 실험군에 비해 유의적으로 높은 평가를 받았다. 즉, 해양심층수염으로 절임배추를 제조할 경우 천일염이나 정제염으로 절임한 배추에 비해 관능적으로 우수하고 무기질, 유기산 함량이 높은 양질의 절임배추를 제조할 수 있을 것으로 사료되었다.

• 해양환경안전학회지
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• 제27권6호
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• pp.875-882
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• 2021

통상적으로 직업소음에 의한 청력손실을 최소화하기 위해서는 작업자가 8시간 동안 85 dBA 이상 소음에 노출되지 않도록 권고하고 있다. 이번 연구에서는 실습선박에서 7종류의 담당업무별 작업자들의 소음노출레벨을 측정하였다. 항해 중, 24시간 동안 작업자의 위치하는 A특성등가소음레벨(L_Aeq,i)과 소음장소의 지속기간(h) 및 소음기여도(L_ex,24h,i)를 고려한 소음노출레벨(L_ex,24h)을 측정하였다. 그 결과, 갑판사관 그룹 L_ex,24h=56.1 dB, 갑판부원 그룹은 L_ex,24h=58.9 dB, 실습항해사들은 L_ex,24h=62.0 dB, 취사부원들은 L_ex,24h=64.3 dB, 실습기관사그룹은 L_ex,24h=91.1 dB, 기관사관 그룹은 L_ex,24h=91.1 dB, 그리고 기관부원 그룹은 L_ex,24h=95.1 dB를 나타내고 있다. 따라서 기관 업무를 담당하는 기관사들, 기관부원들 그리고 기관실습생들은 반드시 청력보호구를 착용해야함을 알 수 있었다. 소음이 심한 기관실에서 청력보호구를 착용한다면 기관사관그룹은 L_ex,24h=23.1 dB, 기관부원그룹은 L_ex,24h=24.4 dB 그리고 기관실습생들은 L_ex,24h=21.5 dB의 소음노출레벨을 줄일 수 있을 것으로 추정된다. 또한 실습생들의 거주구역인 제2 강의실 겸 식당구역에 바닥시공을 64 mm, A-60-class 뜬바닥 구조로 개선했다면 실습항해사들의 소음노출도는 L_ex,24h=4.3 dB, 실습기관사들은 L_ex,24h=1.8 dB 정도 추가적인 감소가 있었을 것이다.

• 한국어병학회지
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• 제20권2호
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• pp.109-117
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• 2007

본 연구에서는 국내 연구보고는 아직 없는 실정이나 양식터봇의 연쇄구균 병원체로 보고 된 바가 있는 제주 양식넙치에서 분리되는 γ 용혈성의 연쇄구균인 Streptococcus parauberis의 특성을 제시하고자 하였다. S. parauberis에 대한 분리균주의 탄소원을 기질로 이용하는 특성은 Annette and Collllins (1990)가 보고한 결과와 유사하였다.또한 분리된 균주들을 계통분류학적 분석 결과 Accesion number AY584477 하나의 그룹으로 묶였지만 S. iniae와는 다른 그룹으로 묶였다. 그러나 Collins가 Streptococcus iniae (X58306)와 S. parauberis (X89967)이 한 그룹으로 묶인다고 발표한 것과는 다른 결과를 나타냈다. 16S rRNA gene에 대한 염기서열 분석 결과는 S. parauberis (AY942572)와 98%이상의 상동성을 나타내어 S. parauberis로 동정하였다. S. parauberis는 S. uberis type Ⅱ로 분류되었으나 Williams and Collins (1990)에 의해서 S. parauberis라는 종명이 제시되었다. 이러한 결과로 볼 때 제주도 양식넙치의 연쇄구균증 병원체로 S. parauberis로 판단되나 이번 실험에서 감염실험이 수행되지 않아 앞으로 본 병원체에 대한 감염 실험과 병리학적인 연구가 필요하다고 사료되어진다.

• Journal of Plant Biotechnology
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• 제4권3호
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• pp.123-127
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• 2002

Herbicide tolerant rice (Oryza sativa L. cv. Ilpumbyeo) cell lines were selected from $\gamma$-ray-irradiated anther-derived cell cultures. The anther-derived cell clusters were small (300 to 400 ${\mu}{\textrm}{m}$ in diameter) and uniform ones that were screened by miracloth filtering. The cell suspensions were very efficient to plate one layer onto agar medium and to screen target cell lines. Herbicide tolerant cell lines were selected by 5 mg/L cyhalofop butyl (CHB) treatment by using the small cell suspensions on agar N6 medium containing 1 mg/L 2,4-D and 0.2 mg/L kinetin. Of the cell lines, one line (CHB-1) showed stable tolerance at 10 mg/L concentration after 6-month culture without herbicide suspension. Growth stability of CHB-1 was similar to that of control cell line on 10 mg/L CHB containing medium. In this experiment we established herbicide tolerant cell line selection system by using anther-derived uniform-cell suspensions with $\gamma$-ray-irradiation.

• 비파괴검사학회지
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• 제6권2호
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• pp.37-45
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• 1987

Speckle photography is a very useful method for measuring in-plane surface displacement. In its basic form, the object to be studied is illuminated with a divergent laser beam, and a double exposure photograph of the object is recorded, on a fine-grain film or plate, before and after the object is deformed, The magnitude and the direction of the displacement can then be obtained by measuring the spacing and the direction of the Young's fringe, which is produced by probing the developed negative with an unexpaned laser beam, and consists of a pattern of parallel equi-spaced dark bands. In this paper, a hybrid optical and electronic image processing is described-Young's fringe on the viewing screen is observed by a TV-camera and the 2-D video signal is converted from analog to digital and transfered to the computer where the spacing and direction of the fringes are calculated. Several examples of application show that the displacement magnitude and direction can be determined with an accuracy of $0.1{\mu}m\;and\;0.1^{\circ}$ respectively.

• 융복합기술연구소 논문집
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• 제1권2호
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• pp.6-15
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• 2011

This paper reports the design and fabrication of a micro-electro-mechanical-system(MEMS)-based electrostatic angular microactuator for a dual-stage servo. The proposed actuator employs a novel electrode pattern named "skewed electrode array(SEA)" scheme. It is shown that SEA has better linearity than a parallel plate type actuator and stronger force than a comb-drive based actuator. The moving and the fixed electrodes are arranged to make the driving force perpendicular to the rotating moment of arm. By changing the electrode overlap length, the magnitude of electrostatic force and stable displacement will be changed. In order to optimize the design, an electrostatic FE analysis was carried out and an empirical force model was established for SEA. A new assembly method which will allow the active electrodes to be located beneath the slider was developed. The active electrodes are connected by inner and outer rings lifted on the base substrate, and the inner and outer rings are connected to platform on which the slider locates. Electrostatic force between active electrodes and platform can be used for exiting out of plane modes, so this provides the possibility of the flying height control. A microactuator that can position the pico-slider over ${\pm}0.5{\mu}m$ using under 20 volts for a 2 kHz fine-tracking servo was designed and fabricated using SoG process.

• 대한기계학회논문집B
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• 제21권1호
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• pp.49-56
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• 1997

Heat-transfer enhancement is seeked through modifications of fin surface. Real life plate-fin heat exchangers have complex three-dimensional geometries. Fins can have arrays of dimples and are attached to rows of penetrating tubes. To isolate the effect of surface modification, we model the real flow by a two-dimensional channel flow with a dimple on one side. The flow is analysed by solving the incompressible Navier-Stokes equation by a finite volume method on a generalized boundary-fitted coordinate. Results show a trapped vortex inside the dimple for all cases computed. Local maximum of Nusselt number occurs near the downstream end of the dimple, due to such a vortex. Location of the vortex does not change with respect to the wall temperature change, but moved downstream when Reynolds number increases. This, together with the results that in all cases vortex core is somewhat downstream of the dimple center, suggests that the mean flow above continuously feeds the kinetic energy to the recirculating flow. Heat transfer enhancement and pressure losses are studied through analysing the relevant dimensionless parameters like, Nusselt number and friction factor. In all cases computed, dimpled channel flow experiences less pressure loss than two-dimensional Poiseuille flow.

• 한국소음진동공학회논문집
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• 제15권6호
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• pp.687-696
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• 2005

Acoustic power spectrum of the upstream and downstream sound field due to an isotropic frozen turbulent gust impinging on a cascade of flat plate airfoils are computed by using a analytic formulation derived from Smith's method, and Whitehead's LINSUB codes. A parametric study of the effects on sound power of the number of blades and turbulence length scale is performed with an emphasis on analyzing the characteristics of sound power spectrum. Through the comparison of the computed results of sound power, it is found that acoustic power spectrum from the 2-D cascade subject to a ingested turbulence can be categorized into two distinct regions. one is lower frequency region where some spectral components of turbulence do not contribute to the cut-on acoustic modes and therefore the effect of the cascade geometry is more dominant ; the other is higher frequency region where all of spectral components of turbulence make contributions to cut-on acoustic modes and thus acoustic power is approximately proportional to the blade number.