• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.59-59
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• 2011

We will report atomically sharp epitaxial growth of $Bi_2Se_3$ three-dimensional topological insulator films on Si(111) substrate with molecular beam epitaxy (MBE). It was achieved by employing two step growth temperatures to prevent any formation of second phase, like as $SiSe_2$ clusters, between $Bi_2Se_3$ and Si substrate at the early stage of growth. The growth rate was determined completely by Bi flux and the Bi:Se flux ratio was kept ~1:15. The second-phase-free atomically sharp interface was verified by RHEED, TEM and XRD. Based on the RHEED analysis, the lattice constant of $Bi_2Se_3$ relaxed to its bulk value during the first quintuple layer implying the absence of strain from the substrate. Single-crystalline XRD peaks of $Bi_2Se_3$ were observed in films as thin as 4 QL. TEM shows full epitaxial structure of $Bi_2Se_3$ film down to the first quintuple layer without any second phases. This growth method was used to grow high quality epitaxial $Bi_2Se_3$ films from 3 QL to 3600 QL. The magneto-transport properties of these thin films show a robust 2D surface state which is thickness independent.

• Proceedings of KOSOMES biannual meeting
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• 2005.05a
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• pp.161-165
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• 2005

Recently, it is on the increase interest for Al alloy with new material for ship application to substitute for FRP ship. The reason is thatAl alloy ship has beneficial characteristics such as high sea speed, increase of loadage and easy to recycle compared with FRP ship. In this paper, mechanical and electrochemical properties are investigated by slow strain rate test experiment in various applied potential condition. These results will provide as reference data to design ship by deciding optimum protection potential regard to hydrogen embrittlement and stress corrosion cracking. In general, Al and Al alloys are not corroded with forming film which has the corrosion resistance property in neutral solution. However, it was observed that formation and destruction of passive film by $Cl^-$ ion in sea water environment. At comparison of current density after 1200 sec in potentiostatic experiment, the current density in the potential range of -0.68 $\~$-1.5 V is shown low value. The low current density means protection potential range. Elongation in applied potential of 0 V was high. However, the corrosion protection application in this condition is impossible potential because the toughness is low value by decreasing strength by active dissolution reaction at parallel part of specimen. The film composed with $CaCO_3$ and $Mg(OH)_2$ has a corrosion resistance property. However, the uniform electrodeposition coating at below -1.6 V potential is not formed since the time to form the uniform electrodeposition coating is short. Therefore, it is concluded that mechanical property is poor because effect by hydrogen gas generation is larger than that of electrodeposition coating. It is concluded that the optimum protection potential range from comparison of_maxim urn tensile strength, elongation and time to fracture is -1.3$\~$0.7 V (SSCE).

• Journal of Life Science
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• v.13 no.6
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• pp.933-942
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• 2003

CoenzymeQ is a quinone derivative with a long isoprenoid side chain. It transports electrons in the respiratory chain located in the inner mitochondrial membrane of eukaryotes and the plasma membrane of prokaryotes. It also functions as an antioxidant. Saccharomyces cerevisine coq mutants, that are deficient coenzyme Q biosynthesis fail to aerobically grow. They are not able to grow on non-fermentable carbon sources, such as glycerol, either The putative $coq^{-7}$ gene involved in coenzyme Q biosynthesis of Neurospora crassa was cloned and used for complementation of S. cerevisiae coq7 mutant. The predicted amino acid sequence of N. crassa COQ7 showed about 58% homology with Coq7p of S. cerevisiae. The growth rate of S. cerevisiae $coq^7$ mutant transformed with the N. crassa $coq^{-7}$ gene was restored to the wild-type level. The complemented 5. cerevisiae strain was able to grow with glycerol as a sole carbon source and showed less sensitivities to linolenic acid, a polyunsaturated fatty acid.

• Journal of Microbiology and Biotechnology
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• v.18 no.7
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• pp.1266-1273
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• 2008

Lactic acid bacteria (LAB) with antimicrobial activity and high exopolysaccharide (EPS) production ability isolated from sourdough were studied for their fermentation characteristics as potential new starter cultures. The values of pH, titratable acidity, and viable cell counts were $4.06{\pm}0.009-4.50{\pm}0.015,\;0.787{\pm}0.020%-1.172{\pm}0.018%,\;and\;8.78{\pm}0.08-8.98{\pm}0.06$ log CFU/ml, respectively. In order to select probiotics with a high survival rate in the gut, isolates were tested to assess resistance against the artificial gastric acid and bile juice. Viable LAB counts were significantly (p<0.05) affected by the acidity. At pH 2.0, the total declines in the initial bacterial counts were 4.52$\pm$0.07 log for S. thermophilus St-Body-1, >7.98$\pm$0.03 log for E. flavescens DU-10, >7.95$\pm$0.05 log for E. faecium DU-12, and 3.15$\pm$0.06 log for L. amylovorus DU-21. Among the strains, L. amylovorus DU-21 was the only strain that had bile tolerance under simulated gastrointestinal conditions. In order to improve EPS production by L. amylovorus DU-21, the influence of carbon source was studied. When glucose was used as a carbon source, EPS production dramatically increased to 17.19$\pm$0.28 g/l (p<0.05). The maximum cell growth (10.012$\pm$>0.012 log CFU/ml) and EPS production (18.71$\pm$0.19 g/l) were achieved when 15 g/l of glucose was employed as the carbon source.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.309-316
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• 2010

This paper proposed a nonlocal anisotropic damage model to simulate the behavior of plain and reinforced concrete structures that are predominantly tensile and compressive load. This model based on continuum damage mechanics, used a symmetric second-order tensor as the damage variable. For quasi-brittle materials, such as concrete, the damage patterns were different in tension and in compression. These two damage states were modeled by damage evolution laws ensuring a damage tensor rate proportional to the total strain tensor in terms of principal components. To investigate the effectiveness of proposed model, the double edge notched specimen experimented by nooru-mohamed and reinforced concrete bending beam were analyzed using the implementation of the proposed model. As the results for the simulation, the nonlocal anisotropic damage model with an adequate control of rupture correctly represented the crack propagation for mixed mode fracture. In the structural failure of reinforced concrete bending beam, the proposed model can be showed up to a very high damage level and yielding of the reinforcements.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.1
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• pp.1-6
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• 2024

Spiders detect even tiny vibrations through their vibrational sensory organs. Leveraging their exceptional vibration sensing abilities, they can detect vibrations caused by prey or predators to plan attacks or perceive threats, utilizing them for survival. This paper introduces a nanoscale crack-based sensor mimicking the spider's sensory organ. Inspired by the slit sensory organ used by spiders to detect vibrations, the sensor with the cracks detects vibrations and pressure with high sensitivity. By controlling the depth of these cracks, they developed a sensor capable of detecting external mechanical signals with remarkable sensitivity. This sensor achieves a gauge factor of 16,000 at 2% strain with an applied tensile stress of 10 N. With high signal-to-noise ratio, it accurately recognizes desired vibrations, as confirmed through various evaluations of external force and biological signals (speech pattern, heart rate, etc.). This underscores the potential of utilizing biomimetic technology for the development of new sensors and their application across diverse industrial fields.

• Proceedings of the Korean Aquaculture Society Conference
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• 2003.10a
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• pp.36-36
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• 2003

In the present study, growth performances of the offspring from selected brood line were compared to those of the offspring from non-selected brood line of red sea bream. Offspring groups were mass produced separately from two brood lines, selected and non-selected Korean strain. Selected brood line have been selected by fish size for four generations (upper 5∼30% per generation) and non-selected brood line is the second generation of wild population at south sea in Korea. There's no significant difference in body length between offspring from selected and non-selected brood line during early growing stage (until 96-days old). However, offspring from selected brood line had superior body weight growth than offspring from non-selected brood line. At sea cages rearing trials with communal stocking, Offspring from selected brood line showed significantly better performance in body weight, body length, weight gain, specific growth rate and feed consumption (but not in feed conversion ratio) than offspring from non-selected brood line. At 24 months old, offspring from selected brood line grew faster 1.10 times in body length and 1.41 times in body weight than offspring from non selected brood line. The response to selection when compared to a non-selected line is on average of 10% in weight per generation at 24 months old.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.129-139
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• 2015

Concrete-Face Rock-Fill Dams (CFRDs) are rock-fill dams with watertight-concrete slabs on its upstream slope instead of its central earth cores. The design for CFRDs are still largely empirical and typically based on past experiences. This paper presents a description of the concrete face slabs and leakage behaviors of two post-constructed CFRDs based on the data gathered through instrumentation during the initial impoundment. The results show that the strain on the concrete face slab and the horizontal displacements of the vertical slab joints are slightly affected by both the seasonal temperature change and water loading during the initial impoundment. The deformation of perimetric joints are less affected by the temperature change, however it is significantly affected by the water loading during the initial impoundment. The leakage rate is significantly affected by the hydrostatic load and the deformation of the perimetric joints.

• Journal of Environmental Science International
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• v.2 no.4
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• pp.271-278
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• 1993

Optimal biodegradation kinetics models to the initial nonylphenol ethoxylates-30 concentration were investigated and had been fitted by the linear regression. Microorganisms capable of degrading nonylphenol ethoxylates-30 were isolated from sewage near Ulsan plant area by enrichment culture technique. Among them, the strain designated as EL-10K had the highest biodegradability and was identified as Pseudomonas from results of taxonomical studies. The optimal conditions for the biodegradation were 1.0 g/ι of nonylphenol ethoxylates-30 and 0.02 g/ι of ammonium nitrate at pH 7.0 and 3$0^{\circ}C$. The highest degradation rate of nonylphenol ethoxylates-30 was about 89% for 30 hours incubation on the optimal condition. Biodegradation data were fit by linear regression to equations for 3 kinetic models. The kinetics of biodegradation of nonylphenol ethoxylates was best described by first order model for 0.1 $\mu\textrm{g}$/ι nonylphenol ethoxylates-30 ; by Monod no growth model and Monod with growth model for 0.5 $\mu\textrm{g}$/mι and 1.0, 5.0 $\mu\textrm{g}$/mι, respectively.

• Applied Chemistry for Engineering
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• v.26 no.5
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• pp.569-574
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• 2015

Arthrospira platensis has high lipid and pigment (such as chlorophyll and carotenoid) contents and thus evaluated as an important resource in functional food production. The cell growth rate and pigment concentration of EM24 increased by approximately 1.2-fold than those of the wild-type strain (WT). Fluorescence intensity levels in EM24, which were quantified with a lipid triolein standard curve, also increased by approximately 1.5-fold than those in WT (62.9 mg/Lvs. 38.9 mg/L). The analysis of fatty acid profiles indicated that the gamma-linoleic acid level in EM24 increased by 1.5-fold than that in WT.