• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.64-72
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• 2022

In this study, in order to confirm the seismic performance of reinforced concrete frames retrofitted with Wall Friction Damper(WFD), the test was conducted by setting two-story Reinforced concrete frames (reference specimen, OMF-N and specimen retrofitted with internal H-shaped steel frame and WFD, OMF-ALL(H)) as main variables. The WFD Seismic Retrofit Method is a mixture of strength improvement and energy dissipation methods. To prevent the pre-destruction of existing structure by friction force before sufficient energy dissipation of WFD, the internal H-shaped steel frame and chemical anchor that penetrates the side of the beam were used to install WFD. According to the test results, the OMF-N specimen showed an brittle failure pattern caused by the shear force of the R/C column after the maximum strength was expressed. The OMF-ALL(H) specimen showed that the reduction of pinching effect and the failure of the RC column occurred. Also, the maximum strength, cumulative energy dissipation and ductility of OMF-ALL(H) increased 3.01 times, 7.2 times and 1.72 times for OMF-N. As a results, test results revealed that the WFD Seismic Retrofit Method installed on Reinforced concrete structure improves the seismic performance and the strengthening effect is valid.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.254-258
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• 2000

Current leads of high $T_{c}$ superconductor were fabricated with Bi excess B $i_{2.2}$/S $r_{1.8}$/C $a_{1}$/C $u_{2}$/ $O_{x}$ composition by rapid cooling method. The dimensions of final samples were fixed 3 mm and 8 mm diameter with 50 mm length each To control uniform density the samples were preformed by CIP(Cold Isostatic Press) process and followed by partial or full melting process after raising up to 90$0^{\circ}C$ for 30min. Plate shaped microstructure was clearly observed adjacent to the Ag tube wall and the size of plate was about 100$\mu$m. However the severe destruction of growth orientation was shown in the inner growth part. critical temperature ( $T_{c}$) was about 53~71K after directional growth while Tc was decreased about 77~80 K before directional growth. After directional growth critical current( $I_{c}$) and critical current density( $J_{c}$) in the specimen of 8 mm diameter at 50 K were about 110 A and 280 A/c $m^2$ respectively.pectively.ely.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.483-492
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• 1998

An inverse analysis been applied to obtain the flow stress of the material. In this method, a ring-shaped specimen is compressed between two flat tools. This procedure employs, as the object function of inverse analysis, the balance of measured loads and reaction forces calculated by using rigid-plastic finite element method. The balance is explicit scalar function of flow stress which is a function of some unknown constants. For minimizing the balance, Newton-Raphon scheme is used. The friction factor, m, between flat tools and the specimen is determined by using friction area-divided method. The proposed method allows an accurate identification by avoiding the usual assumptions made in order to convert experimental measures into stress-strain relation. In this paper, the proposed method is numerically tested. A commercial pure aluminum was selected, as an example, to apply the method and the results are compared with stress-strain relation obtained by experiments.

• Ocean Science Journal
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• v.42 no.4
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• pp.231-240
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• 2007

Three marine fish species are recorded for the first time from Korean waters: a molid (Ranzania laevis, 1 specimen, 279.8 mm SL) and bramid (Pterycombus petersii, 3 specimens, 95.3-214.0 mm SL) collected from a large purse seine off Jeju Island, in the southern sea of Korea, and a carangid (Carangoides dinema, 1 specimen, 194.5 mm SL) from a set net in coastal waters off Busan, in the southeastern sea of korea. R. laevis is characterized by a wedge-shaped body and truncated clavus; P. petersii by the dorsal fin origin above or behind the posterior margin of eye, and dorsal and anal fins depressible; and C. dinema by a row of black blotches along the second dorsal fin base, the curved part of the lateral line longer than straight part, and 18 and 16 dorsal and anal fin rays, respectively. New Korean names are proposed for all three species.

• The Korean Journal of Malacology
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• v.27 no.3
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• pp.175-180
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• 2011

The investigated amounts according to microalgae for stable supply of artificial seed of the hard clam, Meretrix petechialis and also observed the effect according to the repower of the microalgae after the specified period starvation. The stage of specimen used in the test was the D-shaped larva. The microalgae was Chaetoceros calcitrans, Isochrysis galbana and Nannochloris oculata. When the mixture of Chaetoceros calcitrans, Isochrysis galbana and Nannochloris oculata or alone C. calcitrans as food was supplied with 3,000-5,000 cells/ind., it turned to be the most effective. When the food was provided after starvation for some period, the shell length of D-shaped larva was grown to over $192.5{\mu}m$ at fourth day from the initial feeding. The survival rate tended to be lower, the longer the starvation period.

• Journal of Ocean Engineering and Technology
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• v.18 no.6 s.61
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• pp.84-90
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• 2004

Fatigue tests were conducted on SM45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading systems, were employed fully-reserved cyclic torsion without a superimposed static tension or compression fully-reserved cyclic torsion with a superimposed static tension and fully-reserved cyclic torsion with a superimposed static compression. The test results showed that a superimposed static tensile mean stress reduced fatigue life however a superimposed static compressive mean stress increased fatigue life. Experimental results indicated that cracks were initiated on planes of maximum shear strain whether or not the mean stresses were superimposed. A biaxial mean stress had an effect on the direction that the cracks nucleated and propagated at stage 1 (mode II).

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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• pp.115-121
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• 2008

Microstructure of glass-ceramics obtained by heat treating silicate glass containing 50 wt% electric arc furnace dust (EAF dust) and nucleation agents were observed. The crystallization temperature, $T_c$ of glassy specimen measured around $850^{\circ}C$ from different thermal analysis, so the heat treatment condition to obtain glass-ceramic specimen was selected as $950^{\circ}C/15 hr$. The nucleation agent, $TiO_2$ showed the superior effect on enhancing franklinite crystal growth which has stronger mechanical properties and more durable chemical resistance than willemite phase. Some specimens containing $TiO_2$ had the augite crystal phase and increasing $TiO_2$ amount decreased a fraction of willemite and increased a franklinite. Especially, the specimen with 5 wt% $TiO_2$ showed no willemite crystal phase and $1{\sim}2\;{\mu}m$ franklinite crystals dispersed uniformly in glassy matrix. Also, the specimens containing 5 wt% $TiO_2$ mixed with $Fe_2O_3$ showed a dendrite-shaped franklinite crystals caused by coalescence of small crystallites.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.909-914
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• 2001

It is important to consider an effect of concrete member sizes when estimating the ACI rectangular stress block of a reinforced concrete flexural member. However, the experimental data and analytical analyses are still not available for a proper evaluation. For all types of loading conditions, the trend is that the size of an ACI rectangular stress block tends to change when the member sizes change. In this paper, the size variations of strength coefficients for ACI rectangular stress block and actual stress distribution have been studied. Results of a series of C-shaped specimens subjected to axial compressive load and bending moment were adopted from references 1 and 2. The analysis results show that the effect of specimen sizes on strength coefficients for ACI rectangular stress block and actual stress distribution of concrete member was apparent. Thus, the results suggest that the current strength criteria based design practice should be reviewed.

• Journal of Species Research
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• v.11 no.3
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• pp.174-179
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• 2022

In this study, we identified two marine synchaetid rotifers, Synchaeta grimpei Remane, 1929 and S. vorax Rousselet, 1902, in Korea, which are the first synchaetid rotifers collected from a marine environment in the country. Prior to this study, all six synchaetids recorded in Korea were collected from freshwater environments. The morphological characteristics of both species are consistent with those recorded in previous studies of each species. Synchaeta grimpei is distinguished from other synchaetid rotifers by its cone-shaped body, wide and flat apical field, indistinct auricles, and long foot with two separated small toes. The morphological characteristics of Korean S. vorax specimens were most similar to the original description of Rousselet (1902), with its slender and cylindrical trunk shape, strongly convex apical field, and short foot with two small, separated toes. The rami of the Korean S. vorax specimen contained one frontal hook and several distinct and large teeth. Here, we provide the morphological diagnoses of the two synchaetid rotifers and the sequences of the partial mitochondrial cytochrome c oxidase subunit I (COI) of the two species.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.5
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• pp.230-235
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• 2004

In this paper, epoxy elasticity factors were investigated by TMA (Thermomechanical Analysis), DMTA (Dynamic Mechanical Thermal Analysis) and FESEM (Field Emission Scanning Electron Microscope) to improve toughness and reduce brittleness of existing epoxy resin. Dumbbell shaped specimens were made and tested at rates of 0, 20 and 35phr (part per hundred resins). TMA temperatures ranged from -2$0^{\circ}C$ to 20$0^{\circ}C$. Tg (glass transition temperature) of elastic epoxy was measured by thermal analysis. Also investigated were thermal expansion coefficient ($\alpha$), modulus and Tan$\delta$ (loss factor). And we analyzed structure through FESEM, could find elastic-factors of elastic epoxy that is not existing-epoxy. In addition, we measured permittivity and Tan$\delta$ for investigation of the electrical properties of elastic epoxy. Permittivity and Tan$\delta$ depend on elastomer composition. Namely, permittivity and Tan$\delta$ increase according to the elastomer contents. For experimental analysis results, 20phr was considered an excellent specimen.