• Journal of Korea Foundry Society
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• v.30 no.2
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• pp.66-75
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• 2010

The effects of alloying elements on the mechanical properties of normalized and quenched 3.60wt%C-2.60wt%C ductile cast iron poured into shell stack mold were investigated. The strength and hardness of as-cast specimen were increased and the elongation of it was decreased with the additions of Mn, Cu and Sn. The strength and hardness were increased with the addition of 0.40wt%Mo and then rather decreased with the increased addition of 0.80wt%. The strength and hardness were increased with normalizing treatment and the strengths of normalized specimens were increased slightly with the addition of alloying elements except Mo. Meanwhile the yield strength of the normalized specimen was increased slightly with the addition of Mo, the tensile strength was not changed much. Meanwhile the hardness and strength of the quenched specimen were slightly increased with the addition of Mn, those were almost not changed with the amount added. The tensile strength of the quenched specimen with larger diameter, when the Cu had been added, and the tensile and yield strengths of them, when Mo had been added, were increased with the addition of alloying element. On the other hand, those were not changed with the amount added. For the case of specimen with smaller diameter, there were no effects of these two elements. When Sn had been added, the strength of hardened specimen with larger diameter was slightly increased with the amount added. However, that with smaller diameter was rather decreased with it. The effect of specimen diameter on the strength of quenched specimen with the addition of Cu, Mo and Sn was reduced.

• Microbiology and Biotechnology Letters
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• v.34 no.4
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• pp.306-310
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• 2006

For screening of the compounds exhibiting antimicrobial activities against the D-alanyl-D-alanine of Gram positive bacteria, approximately 2,500 actinomycetes isolated from soil were examined far antimicrobial activity. In consequence, we recently isolated the Streptomyces sp. G91353 strain produced an active compound, A91353, that inhibits the growth of Gram positive bacteria. A91353 was identified as N-acetyl-phenylalanine by various spectroscopic methods. The minimum inhibitory concentration (MIC) values of N-acetyl-phenylalanine on Gram positive bacteria such as Streptococcus pyogenes 308A, Streptococcus pyogenes 77A were determined as $50{\mu}g/ml$, respectively, but did not effect on Gram negative strains. These results indicate that N-acetyl-phenylalanine have an antimicrobial activity, which may be caused by the disturbance of D-alanyl-D-alanine synthesis.

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.273-277
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• 1999

From each sediments collected at Chudong(static) and Hoenam(streaming) site of Lake Daechung on May 18(before rainy season) and on August 24 in 1998(after rainy season), different strains of Actinomycetes were isolated and identified to genus level. For comparison, the genus diversity of Actinomycetes in control soils such as grass land around lake, lake shore, and shallow(5-10cm) lake was also investigated. In consequence, the isolation of Streptomyces from the sediments of Lake Daechung was the most copious(41 strains) at the streaming site before rainy season and the least(27 strains) at the static site before rainy season, which were 2.4- and 1.6-fold larger than the average(17 strains) of control soils, respectively. In addition, the isolation of rare Actinomycetes from the sediments of Lake Daechung was the most copious(23 strains) at the streaming site before rainy season and the least(12 strains) at the static site after rainy season, which were 3.2-and 1.6-fold larger than the average(17 strain) of controls, respectively. Therefore, it is considered that lake sediments exhibit higher diversity of Streptomycete as well as rare Actinomycetes than general soils, and thereby can be utilized as useful sources to isolate diverse Actinomycetes.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.5
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• pp.597-602
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• 1997

Cytochrome P450 2E1 (CYP2E1) is involved in the toxicity and carcinogenicity of a number of solvents and xenobiotics. Like the various types of oxidation pharmacogenetics, the activity of the enzyme shows a discernible interindividual and interethnic variation. However, no pharmacogenetic information on CYP2E1 polymorphism has been available from a Korean population. The aim of this study was to explore the pharmacogenetics of CYP2E1 polymorphism in a native Koreans after an oral 400 mg dose of chlorzoxazone administered to 128 subjects. Urine samples were collected during the subsequent 8-hour period and urinary concentrations of chlorzoxazone and 6-hydroxychlorzoxazone were determined by a high performance liquid chromatography with an ultraviolet detector. The limit of detection in the samples was found to be $0.5\;{\mu}g/ml$. The mean value of the 6-hydroxychlorzoxazone excreted in 8 hr urine expressed as the percentage was 48.2 13.8%. The frequency distribution of percentage of the administered dose excreted as the 6-hydroxy metabolite was unimodally distributed in the subjects studied. However, the values showed wide (7-fold) interindividual difference, ranged from 11.6% to 79.8% of the dose of chlorzoxazone. Thus, it was considered that the pharmacogenetic characteristics of CYP2E1 in a Korean population did not represent multimodal distribution in the 6-hydroxychlorzoxazone excreted in 8-hr urine expressed as the percentage. And the activity of the CYP2E1 in a Korean population seemed to be less compared with that of the Caucasian subjects.

• The Korean Journal of Physiology and Pharmacology
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• v.13 no.1
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• pp.9-14
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• 2009

We cultured canine kidney(MDCK) cells stably expressing aquaporin-2(AQP2) on collagen-coated permeable membrane filters and examined the effect of extracellular ATP on arginine vasopressin(AVP)-stimulated fluid transport and cAMP production. Exposure of cell monolayers to basolateral AVP resulted in stimulation of apical to basolateral net fluid transport driven by osmotic gradient which was formed by addition of 500 mM mannitol to basolateral bathing solution. Pre-exposure of the basolateral surface of cell monolayers to ATP(100 ${\mu}M$) for 30 min significantly inhibited the AVP-stimulated net fluid transport. In these cells, AVP-stimulated cAMP production was suppressed as well. Profile of the effects of different nucleotides suggested that the $P2Y_2$ receptor is involved in the action of ATP. ATP inhibited the effect of isoproterenol as well, but not that of forskolin to stimulate cAMP production. The inhibitory effect of ATP on AVP-stimulated fluid movement was attenuated by a protein kinase C inhibitor, calphostin C or pertussis toxin. These results suggest that prolonged activation of the P2 receptors inhibits AVP-stimulated fluid transport and cAMP responses in AQP2 transfected MDCK cells. Depressed responsiveness of the adenylyl cyclase by PKC-mediated modification of the pertussis-toxin sensitive $G_i$ protein seems to be the underlyihng mechanism.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.976-979
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• 2002

A focusing grating coupler (FGC) was not fabricated by the 'Continuous Path Control' writing strategy but by an electron-beam lithography system of more general exposure mode, which matches not only the address grid with the grating period but also an integer multiple of the address grid resolution (5 nm), To more simplify the fabrication, we are able to reduce a process step without large decrease of pattern quality by excluding a conducting material or layer such as metal (Al, Cr, Au), which are deposited on top or bottom of an e-beam resist to prevent charge build-up during e-beam exposure. A grating pitch period and an aperture feature size of the FGC designed and fabricated by e-beam lithography and reactive ion etching were ranged over 384.3 nm to 448.2 nm, and $0.5{\times}0.5mm^2$ area, respectively, This fabrication method presented will reduce processing time and improve the grating quality by means of a consideration of the address grid resolpution, grating direction, pitch size and shapes when exposing. Here our investigations concentrate on the design and efficient fabrication results of the FGC for coupling from slab waveguide to a spot in free space.

• The KIPS Transactions:PartB
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• v.19B no.1
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• pp.9-18
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• 2012

Many audio watermarking researches which have been adapted to authenticate contents can not recover the original media after watermark removal. Therefore, reversible watermarking can be regarded as an effective method to ensure the integrity of audio data in the applications requiring high-confidential audio contents. Reversible watermarking inserts watermark into digital media in such a way that perceptual transparency is preserved, which enables the restoration of the original media from the watermarked one without any loss of media quality. This paper presents a new interval-based audio integrity authentication algorithm which can detect malicious tampering. To provide complete reversibility, we used differential histogram-based reversible watermarking. To authenticate audio in parts, not the entire audio at once, the proposed algorithm processes audio by dividing into intervals and the confirmation of the authentication is carried out in each interval. Through experiments using multiple kinds of test data, we prove that the presented algorithm provides over 99% authenticating rate, complete reversibility, and higher perceptual quality, while maintaining the induced-distortion low.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.26-31
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• 2013

The reduction unit is one of the most important components for railway vehicles because the torque of the motor must be transmitted to the wheels of the vehicle by the reduction unit. The faults in the reduction units of high-speed trains are caused by damage such as gear, fatigue. These have serious impacts on safety of the train during operation. To address this development of a system for monitoring, fault diagnosis of the reduction unit is needed to keep the vehicle running safely. Before that can be accomplished, it is most important to understand the vibration characteristics of the reduction unit in a normal state. Vibration diagnosis technology using characteristic-analysis of vibration waveform and frequency is known to be the most effective method for fault diagnosis. In this paper, we analyzed the vibration characteristics of the reduction units two Korean high-speed trains (KTX and KTX II), under normal conditions, by two test methods (driving gear test, full-vehicle test).

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.21-30
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• 2008

The purpose of this study was to investigate changes in mechanical properties of human tibialis anterior following eccentric exercise. Healthy subjects (n=12) performed 120 maximum eccentric contraction of ankle dorsiflexor. Before and 1- and 24- hour after the eccentric exercise, ankle dorsiflexion moment-angle relationships were obtained. Along with significant decrease in maximum isometric muscle strength, the shift of the optimum ankle joint angle toward the longer muscle length direction was observed, independent of the ranges of motion of the eccentric exercise. The results of this study demonstrated that eccentric exercise-induced micro muscle damage(Morgan & Allen, 1999) does rut seem to be a sole mechanism of eccentric contraction-induced muscle damage, suggesting further investigation for the better understandings of this phenomenon.

• Nuclear Engineering and Technology
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• v.41 no.8
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• pp.1053-1064
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• 2009

The existence of a large sodium pool in the KALIMER, a pool-type LMR developed by the Korea Atomic Energy Research Institute, plays an important role in reactor safety and operability because it determines the grace time for operators to cope with an abnormal event and to terminate a transient before reactor enters into an accident condition. A two-dimensional hot pool model has been developed and implemented in the SSC-K code, and has been successfully applied for the assessment of safety issues in the conceptual design of KALIMER and for the analysis of anticipated system transients. The other important models of the SSC-K code include a three-dimensional core thermal-hydraulic model, a reactivity model, a passive decay heat removal system model, and an intermediate heat transport system and steam generation system model. The capability of the developed two-dimensional hot pool model was evaluated with a comparison of the temperature distribution calculated with the CFX code. The predicted hot pool coolant temperature distributions obtained with the two-dimensional hot pool model agreed well with those predicted with the CFX code. Variations in the temperature distribution of the hot pool affect the reactivity feedback due to an expansion of the control rod drive line (CRDL) immersed in the pool. The existing CRDL reactivity model of the SSC-K code has been modified based on the detailed hot pool temperature distribution obtained with the two-dimensional pool model. An analysis of an unprotected transient over power with the modified reactivity model showed an improved negative reactivity feedback effect.