• 한국자동차공학회논문집
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• 제14권3호
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• pp.103-111
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• 2006

The spray behavior of direct-injection spark-ignition(DISI) engines is crucial for obtaining the required mixture distribution for optimal engine combustion. The spray characteristics of DISI engines are affected by many factors such as piston bowl shape, air flow, ambient temperature, injection pressure and fuel temperature. In this study, the effect of fuel temperature on the spray and combustion characteristics was partially investigated for the wall-guided system. The effect of fuel temperature on the fan spray characteristics was investigated in a steady flow rig embodied in a wind tunnel. The shadowgraphy and direct imaging methods were employed to visualize the spray development at different fuel temperatures. The microscopic characteristics of spray were investigated by the particle size measurements using a phase Doppler anemometry(PDA). The effect of injector temperature on the engine combustion characteristics during cold start and warming-up operating conditions was also investigated. Optical single cylinder DISI engine was used for the test, and the successive flame images captured by high speed camera, engine-out emissions and performance data have been analyzed. This could give the way of forming the stable mixture near the spark plug to achieve the stable combustion of DISI engine.

• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.50-56
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• 2010

$La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ (LSCF) powders with different particle sizes, synthesized through a citrate complexation method and a gel-casting technique, are used to fabricate porous LSCF cathodes with graded microstructures via tape casting. To create porous electrodes with desired porosity and pore structures, graphite and starch are used as pore former for different layers of the graded cathode. Examination of the microstructures of the as-prepared LSCF cathode using an SEM revealed that both grain size and porosity changed gradually from the catalytically active layer (near the electrodeelectrolyte interface) to the current collection layer (near the electrode-interconnect interface). Impedance analysis showed that a 3-layer LSCF cathode with graded microstructures exhibited much-improved performance compared to that of a single-layer LSCF cathode, corresponding to interfacial resistance of 0.053, 0.11, and 0.27 $\Omega{\cdot}cm^2$ at 800, 750, and $700^{\circ}C$ respectively.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.569-578
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• 2011

The $SiO_2$ membranes for polymer electrolyte membrane fuel cell (PEMFC) are preapared by electrospinning method. It leads to high porosity and surface area of membrane to accommodate the proton conducting materials. The composite membrane was prepared by impregnating of Nafion ionomer into the pores of electrospun $SiO_2$ membranes. The $SiO_2$:heteropolyacid (HPA) nano-particles as a inorganic proton conductor were prepared by microemulsion process and the particles are added to the Nafion ionomer. The characterization of the membranes was confirmed by field emission scanning electron microscope (FE-SEM), thermogravimetry analysis (TGA), and single cell performance test for PEMFC. The Nafion impregnated electrospun $SiO_2$ membrane showed good thermal stability, satisfactory mechanical properties and high proton conductivity. The addition of the $SiO_2$:HPA nano-particle improved proton conductivity of the composite membrane, which allow further extension for operation temperature in low humidity environments. The composite membrane exhibited a promising properties for the application in high temperature PEMFC.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 추계학술대회
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• pp.497-498
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• 2018

화재 현장은 정전과 연기와 유독가스로 인해 열영상카메라 및 제논탐조등으로도 전방 가시거리 1m를 확보하기 힘든 것이 현실이다. 화재현장의 연기입자를 분석해보면, 파장 $5{\mu}m$ 이하의 흰색 연기일지라도, 가시거리가 1미터 이상이 되면 기존의 열영상 카메라 등을 이용할 경우 전방시야 확보가 어렵다. 입자 파장 $5{\mu}m$ 이상의 검은 연기에는 화학소재와 가스, 물분자가 섞여 있어 단일 센서가 아닌 다양한 센서를 이용한 공간투과 센서 기술이 필요하다. 전방 안전시야 확보를 위해 연기투과 및 공간정보 가시화를 위한 라이다 센싱 기술이 필요하다. 본 논문에서는 32bit CPU코어 및 주변회로를 갖춘 정보처리 시스템의 인터페이스를 설계하였다. 또한 라이다 센서와의 인터페이스를 구현하고 이를 시뮬레이션 하였으며 이를 통해 향후 휴먼 증강 소방헬멧의 정보처리 시스템을 구현 가능한 인터페이스를 제공하였다.

• Advances in materials Research
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• 제3권3호
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• pp.139-149
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• 2014

Surface enhanced Raman Scattering (SERS) has attracted attention because the technique enables detection of various chemicals, even down to single molecular scale. Among the diverse candidates for SERS substrates, Au nanoparticles are considered promising due to their fine optical properties, chemical stability and ease of surface modification. Therefore, the fabrication and optical characterization of gold particles on solid supports is highly desirable. Such structures have potential as SERS substrates because the localized surface plasmon resonance of gold nanoparticles is very sensitive to combined molecules and environments. In addition, it is well-known that the properties of Au nanoparticles are strongly dependent on their shape. In this work, arrays of shape-controlled Au nanoparticles were fabricated to exploit their enhanced and reproducible optical properties. First, shape-controlled Au nanoparticles were prepared via seed mediated solution-phase synthesis, including spheres, octahedra, and rhombic dodecahedra. Then, these shape-controlled Au nanoparticles were arranged on a PDMS substrate, which was nanopatterned using soft lithography of poly styrene particles. The Au nanoparticles were selectively located in a pattern of hexagonal spheres. In addition, the shape-controlled Au nanoparticles were arranged in various sizes of PDMS nanopatterns, which can be easily controlled by manipulating the size of polystyrene particles. Finally, the optical properties of the fabricated Au nanoparticle arrays were characterized by measuring surface enhanced Raman spectra with 4-nitrobenezenethiol.

• The Journal of Advanced Prosthodontics
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• 제5권2호
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• pp.126-132
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• 2013

PURPOSE. Post surface conditioning is necessary to expose the glass fibers to enable bonding between fiber post and resin cement. The purpose of the present study was to evaluate the effect of different surface conditioning on tensile bond strength (TBS) of a glass fiber reinforced post to resin cement. MATERIALS AND METHODS. In this in vitro study, 40 extracted single canal central incisors were endodontically treated and post spaces were prepared. The teeth were divided into four groups according to the methods of post surface treatment (n=10): 1) Silanization after etching with 20% $H_2O_2$, 2) Silanization after airborne-particle abrasion, 3) Silanization, and 4) No conditioning (Control). Adhesive resin cement (Panavia F 2.0) was used for cementation of the fiber posts to the root canal dentin. Three slices of 3 mm thick were obtained from each root. A universal testing machine was used with a cross-head speed of 1 mm/minute for performing the push-out tests. Two-way ANOVA and Tukey post hoc tests were used for analyzing data (${\alpha}$=0.05). RESULTS. It is revealed that different surface treatments and root dentin regions had significant effects on TBS, but the interaction between surface treatments and root canal regions had no significant effect on TBS. There was significant difference among $H_2O_2$ + Silane Group and other three groups. CONCLUSION. There were significant differences among the mean TBS values of different surface treatments. Application of hydrogen peroxide before silanization increased the bond strength between resin cements and fiber posts. The mean TBS mean values was significantly greater in the coronal region of root canal than the middle and apical thirds.

• 대한화학회지
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• 제20권2호
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• pp.97-110
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• 1976

竝進-振動에너지 變換에 있어서 中間에너지 準位를 거치지 않는 直接勵起가 多量子 振動천이에 미치는 영향을 理論的으로 조사하였다. 衝突 모형은 直線 충돌이며, 分子間의 포텐셜은 指數函數型의 것을 振動좌표(q)로 전개하고 四次項 $(q^4)$까지 包含시켜 사용하였다. $q^2$, $q^3$, $q^4$를 포함시켰을 때의 천이 확률 $(P_{m{\rightarrow}n})$에 對한 一般式을 各各 유도하고, 몇개의 충돌계에 대하여 그 값들을 계산하였다.結果를 線型化시킨 포텐셜(q)을 사용한 경우의 結果와 比較하고 直按 多量子 振動遷移가 重要한 役割을 하게 되는 條件 파라미터 ${\nalpha}$ 및 m과 관련시켜 제시하였다.

• 한국식품과학회지
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• 제24권2호
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• pp.137-141
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• 1992

고추 oleoresin의 적정 추출조건을 설정하기 위하여 추출에 영향을 미치는 몇 가지 인자들을 대상으로 oleoresin의 수율, capsanthin 및 capsaicin 함량의 변화를 조사하였다. Ethyl alcohol 용매로 추출한 oleoresin은 수율 및 capsanthin 함량이 높고, Ethylene dichloride 용매의 경우는 capsaicin 함량이 높게 나타났다. 혼합용매의 경우는 단일용매의 경우보다 수율은 증가하나 capsanthin 및 capsaicin 함량은 거의 변화가 없었다. 추출에 사용한 3가지 품종 중에서 진솔에서 추출한 oleoresin의 품질이 가장 우수하였다. 적정 추출온도 및 추출시간은 $20^{\circ}C$ 및 $3{\sim}5$시간이었다. 장기 저장한 고추일수록 고추분말의 입도가 클수록 추출되는 oleoresin의 품질은 저하되고, 함량도 적었다 고추의 과피에는 capsanthin이 씨에는 capsaicin이 가장 많았다. 고추분말과 추출용매의 적정혼합비는 $1\;:\;3{\sim}1\;:\;4(w/v)$였다.

• Molecules and Cells
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• 제39권4호
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• pp.286-291
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• 2016

Epstein-Barr virus (EBV) is the prototypical ${\gamma}$-herpesvirus and an obligate human pathogen that infects mainly epithelial cells and B cells, which can result in malignancies. EBV infects these target cells by fusing with the viral and cellular lipid bilayer membranes using multiple viral factors and host receptor(s) thus exhibiting a unique complexity in its entry machinery. To enter epithelial cells, EBV requires minimally the conserved core fusion machinery comprised of the glycoproteins gH/gL acting as the receptor-binding complex and gB as the fusogen. EBV can enter B cells using gp42, which binds tightly to gH/gL and interacts with host HLA class II, activating fusion. Previously, we published the individual crystal structures of EBV entry factors, such as gH/gL and gp42, the EBV/host receptor complex, gp42/HLA-DR1, and the fusion protein EBV gB in a postfusion conformation, which allowed us to identify structural determinants and regions critical for receptor-binding and membrane fusion. Recently, we reported different low resolution models of the EBV B cell entry triggering complex (gHgL/gp42/HLA class II) in "open" and "closed" states based on negative-stain single particle electron microscopy, which provide further mechanistic insights. This review summarizes the current knowledge of these key players in EBV entry and how their structures impact receptor-binding and the triggering of gB-mediated fusion.

• 한국해안해양공학회지
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• 제5권1호
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• pp.1-10
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• 1993

1차 자유도를 갖는 해양구조물을 선정하여 long crested, stationary, Gaussian random waves가 구조물의 동적응답 스펙트럼에 미치는 영향에 대해 규명하였다. 해수면 부근에서 주기적으로 수면위로 부상하는 연직부재를 고려하기 위해 hybrid Morison equation을 제안했고 이 방정식을 기초로 파력을 계산했다. 주기적으로 수면위로 부상하는 효과를 고려한 결과 동적응답 스펙트럼은 감소하였으며 고차 응당성분이 발생했다. 또한 동적응답 스펙트럼은 주파수가 증가할수록 감소하는 경향을 보였으며 이는 해수면 위로 주기적으로 부상하는 현상을 고려할 때 발생하는 고차응답성분 때문인 것으로 사료된다.