• Archives of Pharmacal Research
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• v.21 no.1
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• pp.35-40
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• 1998

Human cytochrome P450 4F2 shows high regioselectivity in hydroxylation of stearic acid and leukotriene $ B_4.$ As a first step of its regulation study, human cytochrome P450 4F2 genomic DNA was isolated from liver of a person who was administered clofibrate for 10 years. From Southern hybridization, restriction enzyme digestion and sequencing experiments, isolated genomic DNA fragment was found to contain around 32 Kb DNA and more than 20 Kb of $5^I$ end regulatory region. Sequences of the structural gene region revealed exon 1 and exon 2. Further regulation studies would elucidate the feedback mechanisms of the oxidative degradation of fatty acids, inflammatory response and the clearance of leukotriene B4 in the liver. Furthermore, regulation study of this gene could explain the species difference in responses to peroxisome proliferator and help in the safety evaluation of peroxisome proliferating chemicals to human being.

• KSTLE International Journal
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• v.1 no.1
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• pp.48-51
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• 2000

Surface damage accumulation of alumina ceramics under the cyclic stress state was analyzed. The alternating stress state in repeat pass sliding contact was simulated by a synchronized biaxial (normal and tangential) repeated indentation technique. Wear debris formation mechanism through damage accumulation and fatigue grain failure in both alumina ceramic balls and flat disks was confirmed, and the contact induced surface degradation due to fatigue cracking accumulation was quantified by measuring vertical contact displacement. Variation of structural compliance (slope of load-displacement curve) of two contacting bodies was expressed as a variation of the apparent elastic property, called pseudo-elastic constant, of the contact system.

• Journal of KSNVE
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• v.10 no.5
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• pp.880-885
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• 2000

In a verical type, vibratory gyroscope, the coupled motion between the reference and sensing vibrations causes the zero-point output which means non-zero sensing vibration without angular velocity. This structural coupling leaks to an inherent discrepancy between the natural frequencies of the reference and sensing oscillations, causing the degradation of the sensing performance and dynamic stability. In this paper, the dynamic characteristics associated the coupling phenomenon are theoretically analyzed. Effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are studied. A technique to predict the existence of curve veering of crossing in frequency trajectories is introduced to apply the design of micro gyroscopes with decoupled structures.

• Journal of the Society of Disaster Information
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• v.6 no.2
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• pp.119-130
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• 2010

In designing a railroad bridge, the fatigue is one of the main factors to be considered for ensuring safe operation. Especially, for a new type of a structural member, which has not been adopted to railroad bridges, the fatigue performance should be checked. In this paper, the fatigue characteristics of an IT girder are examined. The IT girder is a new type of a prestressed concrete girder which has two prestressed H-beams in the top of the girder to give the girder additional sectional capacity. To obtain the fatigue performance, a 10m IT girder specimen is designed, and a repeated load test is performed by applying the load cyclically two million times. The magnitude of the repeated load is determined considering the stress level under the service condition. During the test, static load tests are performed to identify the stiffness degradation. The fatigue performance of the girder is checked according to the Japanese and the CEB-FIB design codes. The fatigue test result shows that the IT girder satisfies both design codes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.337-338
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• 2018

In recent years, residential apartment building parking lots are built in underground spaces, and with conjunction to improve the environment of the urban area, artificial greeen roof systems are installed on the upper slabs. However, early plant growth are resulting in root penetration into concrete cracks and in turn into the waterproofing membranes, leading to degradation and damaging of the waterproofing system and structural durability. This issue highlights a problem of conventional maintenance system of concrete structures, and proposals for amendments follow. In this study, a waterproofing and root barrier construction design for the upper slabs of residential building underground parking lots is proposed, and motioned to be added into future construction specifications.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2252-2254
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• 2002

The Reactor internal structures which consist of many complex components are subjected to flow-induced vibration due to high temperature and pressure in Reactor coolant system. The above flow-induced vibration causes degradation of structural integrity of the Reactor and may result in loosing mechanical binding component which might impact other equipment and component or cause flow blockage. It is important to analyze reactor noise signal for the early detection of potential problem or failure in order to diagnosis reactor integrity in the point of view of safety and plant economics. Detailed composition of diagnostic system reactor internal structures using neutron noise(RIDS).

• Nuclear Engineering and Technology
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• v.45 no.1
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• pp.99-106
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• 2013

Thermal fatigue is a significant long-term degradation mechanism in nuclear power plants. In particular, as operating plants become older and life time extension activities are initiated, operators and regulators need screening criteria to exclude risks of thermal fatigue and methods to determine significant fatigue relevance. In general, the common thermal fatigue issues are well understood and controlled by plant instrumentation at fatigue susceptible locations. However, incidents indicate that certain piping system Tee connections are susceptible to turbulent temperature mixing effects that cannot be adequately monitored by common thermocouple instrumentations. Therefore, in this study thermal fatigue evaluation of piping system Tee-connections is performed using the fluid-structure interaction (FSI) analysis. From the thermal hydraulic analysis, the temperature distributions are determined and their results are applied to the structural model of the piping system to determine the thermal stress. Using the rain-flow method the fatigue analysis is performed to generate fatigue usage factors. The procedure for improved load thermal fatigue assessment using FSI analysis shown in this study will supply valuable information for establishing a methodology on thermal fatigue.

• Bulletin of the Korean Chemical Society
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• v.35 no.10
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• pp.2990-2994
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• 2014

The studies on design and synthesis of new monocyclic ${\beta}$-lactam esters 4(R/S)-(1'-methoxycarbonylpropyl- 2'(R/S)-thio)-3(R)-phenylacetamidoazetidin-2-one (3a) and 4(R/S)-(1'-methoxycarbonyl-2'-methylpropyl-2'- thio)-3(R)-phenylacetamidoazetidin-2-one (3b) were described. Compounds 3a and 3b were specifically designed to retain all penicillin substructures except the bicyclic system, which would be conceived by cleaving the C(3)-N(4) bond of penicillin G. Compounds 3a and 3b are of particular interest in the context of the structural elucidation of monocyclic ${\beta}$-lactams originated from penicillin. Key intermediates, ${\beta}$-mercapto esters 6a and 6b, were synthesized from conjugate acids 4a and 4b using three-step synthetic sequences, respectively, and 4(S)-acetoxy-3(S)-phenylacetamidoazetidin-2-one (7) was obtained from the degradation of penicillin G. Reactions of 6a and 6b with 7, thus obtained, provided the target compounds 3a and 3b, respectively.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.615-621
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• 2016

SiC-polycrystalline fiber (Tyranno SA, Ube Industries, Ltd.) shows very high heat-resistance and excellent mechanical properties up to very high temperatures. However, further increase in the strength is required. Up to now, we have already clarified the relationship between the strength and the defect-size of the SiC-polycrystalline fiber. The defects are formed during the conversion process from the raw material (amorphous Si-Al-C-O fiber) into SiC-polycrystalline fiber. In this conversion process, a degradation of the Si-Al-C-O fiber and a subsequent sintering of the degraded fiber proceed as well, accompanied by a release of CO gas and compositional changes, to obtain the dense SiC-polycrystalline fiber. Since these changes proceed in each filament, the strict control should be needed to minimize residual defects on the surface and in the inside of each filament for achieving the higher strength. In this paper, the controlling factors of the fiber strength and the fine structure will appear.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.82-83
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• 2008

AI doped ZnO (AZO) films, and intentionally Zn added AZO (ZAZO) films were prepared on Corning glass by rf magnetron sputtering, and the electrical, optical, and structural properties of the as-deposited films together with the air annealed films were investigated. The resistivity of the AZO films increased with increasing substrate temperature and having minimum resistivity at $150^{\circ}C$. At the high temperature, the ZAZO films showed improved electrical properties better than the AZO films due.to increase in both the carrier concentration and.the Hall mobility. Upon air annealing at $500^{\circ}C$, the resistivity of both AZO and ZAZO films increased substantially, but the relative amount of degradation was smaller for films deposited at $450^{\circ}C$ than the films deposited at $150^{\circ}C$.