• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.3
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• pp.273-278
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• 2014

On poly and single crystalline Cu substrates, the graphene was synthesized by chemical vapor deposition(CVD). Optical microscopic images which were not possible to show the detailed characterization of graphene growth were adjusted and analyzed using image analyzing software. As a result it was possible to show the detailed growth mechanism of graphene by utilizing the image analysis. Nucleation of graphene on Cu grain boundary and its growth behavior into Cu grain are shown. In addition, the movement of graphene grain boundary interacting with Cu grain boundary and pinholes during growth was illustrated in detail, and the cause and result are discussed as a result of those interactions.

• Journal of ILASS-Korea
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• v.12 no.4
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• pp.211-219
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• 2007

The liquid film thickness inside a pressure-swirl nozzle was measured, and then the measured liquid film thickness was compared with the results from previous empirical equations. The liquid film inside the nozzle was visualized using extended transparent nozzles and a microscopic imaging system, and then the measurement error was evaluated using optical geometry analysis. The high injection pressures up to 7MPa were adopted to simulate the injection conditions of the direct-injection spark-ignition engines. The totally different two injectors with different fuels, nozzle lengths, nozzle diameters and swirlers were utilized to obtain the comprehensive equations. The results showed that the liquid film thickness very slightly decreased at high injection pressures and the empirical equations overestimated the effect of injection pressure. Most of empirical equations did not include the effect of nozzle length and swirler angle, although it caused significant change in liquid film thickness. A new empirical equation was suggested based on the experimental results with the effects of fuel properties, injection pressure, nozzle diameter, nozzle length and swirler angle.

• International Journal of Safety
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• v.6 no.2
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• pp.1-7
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• 2007

In this study mechanical strength of A53B carbon steel was analyzed using several types of test specimens directly machined from oil recycling pipe experienced a failure due to hydrogen attack in chemical plants. High temperature hydrogen attack (HTHA) is the damage process of grain boundary facets due to a chemical reaction of carbides with hydrogen, thus forming cavities with high pressure methane gas. Driven by the methane gas pressure, the cavities grow on grain boundaries forming intergranular micro cracks. Microscopic optical examination, tensile test, Charpy impact test, hardness measurement, and small punch (SP) test were performed. Carbon content of the hydrogen attacked specimens was dramatically reduced compared with that of standard specification of A53B. Traces of decarburization and micro-cracks were observed by optical and scanning electron microscopy. Charpy impact energy in hydrogen attacked part of the pipe exhibited very low values due to the decarburization and micro fissure formation by HTHA, on the other hand, data tested from the sound part of the pipe showed high and scattered impact energy. Maximum reaction forces and ductility in SP test were decreased at hydrogen attacked part of the pipe compared with sound part of the pipe. Finite element analyses for SP test were performed to estimate tensile properties for untested part of the pipe in tensile test. And fracture toughness was calculated using an equivalent strain concept with SP test and finite element analysis results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.6
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• pp.279-282
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• 2013

Recently, it has been interested much that AlN (Aluminum Nitride) crystals can be applied to UV LEDs and high power devices as like GaN and SiC crystals. The reports about commercial grade of AlN wafers in the world have been absent, however several results for growth of large size of AlN single crystals have been reported from abroad. In this report, the result of AlN single crystals of a diameter of about 8 mm grown are reported. Optical microscopic characterization was applied to observe the form of the crystals and the crystal quality was evaluated by FWHM measurement by DCXRD rocking curve analysis.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3383-3386
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• 2012

SnS thin films were deposited on glasses through metal organic chemical vapor deposition (MOCVD) method at relatively mild conditions, using bis(3-mercapto-1-propanethiolato) tin(II) precursor without toxic $H_2S$ gas. The MOCVD process was carried out in the temperature range of $300-400^{\circ}C$ and the average grain size in fabricated SnS films was about 500 nm. The optical band gap of the SnS film was about 1.3 eV which is in optimal range for harvesting solar radiation energy. The precursor and SnS films were characterized through infrared spectroscopy, nuclear magnetic resonance spectroscopy, DIP-EI mass spectroscopy, elemental analyses, thermal analysis, X-ray diffraction, and field emission scanning electron microscopic analyses.

• Journal of Industrial Technology
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• v.21 no.B
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• pp.331-339
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• 2001

Zero to tension fatigue tests and strain controlled fatigue tests were carried out to find how initial strain induced martensite, ${\alpha}^{\prime}$ affects low and high cycle fatigue behavior and fatigue crack growth mechanisms. Microscopic study and phase analysis were carried out with TEM, SEM, EDAX, Optical Microscope, Ferriscope, and X-ray diffractometry. The amount of Initial ${\alpha}^{\prime}$ was controlled from 0% to 33% by controlling the temperatures for cold working and heat treatment. Lower contents of initial ${\alpha}^{\prime}$ showed higher fatigue resistance in low cycle fatigue but lower fatigue resistance in high cycle fatigue because it is ascribed to the more transformation of ${\alpha}^{\prime}$ martensite during low cycle fatigue and higher ductility. In high cycle fatigue, fatigue life is attributed to the strength and phase transformation of austenite into ${\alpha}^{\prime}$ during fatigue was negligible. ${\gamma}$ boundary, ${\gamma}/twin$ boundary, and ${\gamma}/{\alpha}^{\prime}$ boundary were found to be the preferred site of fatigue crack initiation.

• Applied Microscopy
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• v.46 no.2
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• pp.93-99
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• 2016

The thickness of specimen is an important factor in microscopic researches. Thicker specimen contains more information, but it is difficult to obtain well focused image with precise details due to optical limit of conventional microscope. Recently, a microscope unit that combines improved illumination system, which allows real time three-dimensional (3D) image and automatic z-stack merging software. In this research, we evaluated the usefulness of this unit in observing thick samples; Golgi stained nervous tissue and ground prepared bone, tooth, and non-transparent small sample; zebra fish teeth. Well focused image in thick samples was obtained by processing z-stack images with Panfocal software. A clear feature of neuronal dendrite branching pattern could be taken. 3D features were clearly observed by oblique illumination. Furthermore, 3D array and shape of zebra fish teeth was clearly distinguished. A novel combination of two channel oblique illumination and z-stack imaging process increased depth of field and optimized contrast, which has a potential to be further applied in the field of neuroscience, hard tissue biology, and analysis of small organic structures such as ear ossicles and zebra fish teeth.

• Journal of Microbiology and Biotechnology
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• v.16 no.10
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• pp.1597-1604
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• 2006

To screen for an anti-yeast substance (AYS), many bacteria were isolated from soil and a strain AY2000 was selected. The strain AY2000 was identified as Rahnella aquatilis by morphology, biochemical properties, and 16S r-RNA nucleotide sequence analyses. The strain AY2000 showed anti-yeast activity against Candida albicans and Saccharomyces cerevisiae, whereas R. aquatilis ATCC33071 as a type strain did not show the activity against the yeasts under the same condition. The growth of yeast cell was significantly inhibited by AYS produced by the strain AY2000, as shown by optical density and MTT assay. The minimum inhibitory concentration (MIC) of the AYS against S. cerevisiae and C. albicans at $28^{\circ}C\;was\;20{\mu}g/ml\;and\;60{\mu}g/ml$, respectively. The MIC of AYS against hyphae of C. albicans at $37^{\circ}C\;was\;600{\mu}g/ml$. Scanning electron microscopic analysis revealed that yeast cells treated with AYS had an irregular form with a wrinkled and rough surface.

• International Journal of Concrete Structures and Materials
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• v.1 no.1
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• pp.75-81
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• 2007

The concrete pavement of the Seohae Highway in Korea has suffered from serious distress, only four to seven years after construction. Deterioration due to Alkali-Silica Reaction (ASR) has seldom been reported per se in Korea, because the aggregate used for the cement concrete has been considered safe against alkali-silica reaction so far. The purpose of this study is to examine the deterioration caused by an alkali-silica reaction of concrete pavement in Korea. The investigation methods included visual inspection and Automatic Road Analyzer (ARAN) analysis of surface cracks, coring for internal cracks, stereo microscopic analysis, scanning electronic microscope (SEM) analysis, and electron dispersive X-ray spectrometer (EDX) analysis. The results are presented as follows: the crack pattern of the concrete pavement in Korea was longitudinal cracking, map cracking or D-cracking. Local areas of damage were noticed four to five years after construction. The cracks started from edges or joints and spread out to slabs. The most intensive cracking was observed at the intersection of the transverse and longitudinal joints. Where cracking was the most intense, pieces of concrete and aggregate had spalled away from top surface and joint interface area. The progress of deterioration was very fast. The reaction product of alkali-silica gel was clearly identified by its generally colorless, white, or very pale yellow hue seen through a stereo optical microscopy. The typical locations of the reaction product were at the interface between aggregate and cement paste in a shape of a rim, within aggregate particles in the cracks, and in the large void in the cement paste. Most of the white products were found at interface or internal aggregates. SEM and EDX analysis confirmed that the white gel was a typical reaction product of ASR. The ASR gel in Korea mainly consisted of Silicate (Si) and Potassium (K) from the cement. The crack in the concrete pavement was caused by ASR. It seems that Korea is no longer safe from alkali-silica reaction.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.167-171
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• 2014

Using chemical vapor deposition(CVD), the synthesis of graphene was performed on poly and single crystalline Cu substrates. The growth behavior of graphene and its characterization were shown utilizing the optical microscopic image and its image analysis. As a result in the analysis of graphene growth, it was found out the graphene is growing always in particular direction in relation to the crystalline direction of a single grain in polycrystalline Cu substrate. With the image analysis it was possible to show the characterization of graphene, such as the growth direction and the number of layers showing single, double and triple layers, within the neighboring single grains in polycrystalline Cu. In addition, the relatively large area of graphene with about $3mm^2$ on Cu(111) having high quality, single layer, and single crystalline was shown along with its characterization.