• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.20-25
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• 2008

Structural studies have been performed on precipitation hardening and microstructural variations found in Ti-Al-Cr ternary $L1_0$- and $L1_2$-phase alloys using transmission electron microscopy. Both the $L1_0$ and $L1_2$ phase alloys harden by aging at 973 K after solution annealing at higher temperatures. The amount of age hardening of the $L1_2$ phase alloy is larger than that of the $L1_0$ phase alloy. The phase separation between $L1_0$ and $L1_2$ phase have not been observed by aging at 973 K. But $Al_2Ti$ was formed in each matrix alloy during aging. The crystal structure of the $Al_2Ti$ phase is a $Ga_2Zr$ type in the $L1_0$ and a $Ga_2Hf$ type in the $L1_2$ phase, respectively. At the beginning of aging the fine coherent cuboidal $Al_2Ti$-phase are formed in the $L1_0$ phase. By further aging, two variants of $Al_2Ti$ precipitates grow along the two {110} habit planes. On the other hand, in the $L1_2$ phase, the $Al_2Ti$ phase forms on the {100} planes of the $L1_2$ matrix lattice. After prolonged aging the precipitates are rearranged along a preferential direction of the matrix lattice and form a domain consisting of only one variant. It is suggested that the precipitation of $Al_2Ti$ in each matrix alloy occurs to form a morphology which efficiently relaxes the elastic strain between precipitate and matrix lattices.

• Carbon letters
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• v.11 no.4
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• pp.293-297
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• 2010

To investigate new potential application of a clay material for C/C composites, illite added C/C composites were prepared with various illite contents. The improvement of filler effect by illite size reduction was also investigated using wet ballmilling by evaluating illite/phenolic resin infiltration using bulk density and porosity measurements, chemical structural changes of the composites using XRD, and thermal oxidation stability in air of the composites using TGA. The size reduction of illite resulted in narrower particle size distribution and improved illite infiltration into carbon preform. And the resultant C/C composites prepared with illite had even more improved thermal oxidation stability in air, showing more increased IDTs up to $100^{\circ}C$, compared to those of the C/C composites with pristine illite, due to the SiC formation through carbothermal reduction between illite and carbon materials. The illite induced delay in oxidation of the illite-C/C composites was also observed and the delayed oxidation behavior was attributed to the layered structure of illite, which improved illite/phenol resin infiltration. Therefore, the potential use of illite as filler to improve oxidation stability of C/C composite can be promising. And the size reduction of illite can improve its effect on the desired properties of illite-C/C composites even more.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.109-112
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• 2005

Electronic and magnetic properties of $Ti_{1-x}M_xO_{2-\delta}$ (M=Co and Fe) thin films grown by sol-gel method have been investigated. Anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films were successfully grown on $Al_2O_3$ (0001) substrates and exhibited p-type electrical conductivity while the undoped films n-type conductivity. Room temperature vibrating sample magnetometry measurements on the anatase and rutile $Ti_{1-x}Co_xO_{2-\delta}$ films with same x ($=4.8 at.{\%}$) showed quite similar magnetic hysteresis curves with the saturation magnetic moment of $\~4 {\mu}_B$ per Co ion despite their differences in structural and electronic properties. Such giant magnetic moment is attributable to the unquenched orbital moment of the $Co^{2+}$ ions substituting the octahedral $Ti^{4+}$ sites. Similar ferromagnetic behavior was observed for $Ti_{1-x}Fe_xO_{2-\delta}$ films that are highly resistive compared to the Co doped samples. Saturation magnetic moment was found to decrease for higher x, i.e., $\~2$ and $\~1.5 {\mu}_B$ per Fe ion for x=2.4 and 5.8 at. $\%$, respectively. Conversion electron $M\ddot{o}ssbauer$ spectroscopy measurements predicted the coexistence of $Fe^{2+}$ and $Fe^{3+}$ ions at the octahedral sites of $Ti_{1-x}Fe_xO_{2-\delta}$.

• Macromolecular Research
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• v.16 no.1
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• pp.57-61
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• 2008

Chitosan is normally acylated and subsequently conjugated with drugs for biomedical applications. This study examined the relationship between the succinylation and gelation behaviors of glycol chitosan. Glycol chitosan was acylated with succinic anhydride under a wide variety of reaction conditions, such as different molar ratios of succinic anhydride to glucosamine, different methanol content in the reaction media, and different reaction temperatures. Among these reaction parameters, the methanol content in the solvent played an important role in determining the regioseletive succinylating site. N-succinylation and N-N cross-linking occurred regardless of the reaction conditions. However, O-succinylation was observed under specific conditions, i.e. a methanol content> 0.6 (v/v) and a reaction temperature> $25^{\circ}C$. O-succinylation accelerated the N-O cross-linking of glycol chitosan, and led to gelation. The N-succinylated glycol chitosans were water-soluble, whereas the N-and O-succinylated glycol chitosans fonned a gel. These physico-chemical structural differences in the succinylated glycol chitosans would definitely influence subsequent drug-conjugation reactions and consequently the drug loading and release kinetics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1287-1293
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• 2001

Fretting is a potential degradation mechanism of structural components and equipments exposed to various environments and loading conditions. The fretting degradation, for example, for example, can be observed in equipments of nuclear, fossil as well as petroleum chemical plants exposed to special environments and loading conditions. It is well known that a cast stainless steel(CF8M) used in a primary reactor coolant(RCS) degrades seriously when that material is exposed to temperature range from 290$\^{C}$∼390$\^{C}$ for long period. This degradation can be resulted into a catastrophical failure of components. In the present paper, the characteristics of the fretting fatigue are investigated using the artificially aged CF8M specimen. The specimen of CF8M are prepared by an artificially accelerated aging technique holding 180hr at 430$\^{C}$ respectively. Through the investigations, the simple fatigue endurance limit of the virgin specimen is not altered from that obtained from the fatigue tests imposed the fretting fatigue. The similar tests are performed using the degraded specimen. The results are not changed from those of the virgin specimen. The significant effects of fretting fatigue imposed on both virgin and degraded specimen on the fatigue strength are not found.

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.556-565
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• 2002

The concrete bridge decks on the main girder will usually develop initial cracks in the longitudinal or the transverse direction due to dry shrinkage and temperature change, and as the bridge decks age the crack will gradually develop in different directions due to repeated cyclic loads. The strengthening direction of the concrete bridge deck is a very important factor in improving proper structural behavior. Therefore, in this study, theoretical analyses of strengthened bridge decks were performed using the nonlinear finite element method. To improve the accuracy of the analytical result, boundary conditions and material property of strengthening material was simulated by laboratory condition and test results, respectively. The effect of the strengthening direction and the amount of strengthening material were estimated and compared to the experimental results. The efficiency of the strengthened bridge decks by strengthening variables such as the amount, width and thickness of CFS was observed.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.617-628
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• 2017

In order to study the failure mode and seismic behavior of the interior-joint in steel traditional-style buildings, a single beam-column joint and a double beam-column joint were produced according to the relevant building criterion of ancient architectural buildings and the engineering instances, and the dynamic horizontal loading test was conducted by controlling the displacement of the column top and the peak acceleration of the actuator. The failure process of the specimens was observed, the bearing capacity, ductility, energy dissipation capacity, strength and stiffness degradation of the specimens were analyzed by the load-displacement hysteresis curve and backbone curve. The results show that the beam end plastic hinge area deformed obviously during the loading process, and tearing fracture of the base metal at top and bottom flange of beam occurred. The hysteresis curves of the specimens are both spindle-shaped and plump. The ultimate loads of the single beam-column joint and double beam-column joint are 48.65 kN and 70.60 kN respectively, and the equivalent viscous damping coefficients are more than 0.2 when destroyed, which shows the two specimens have great energy dissipation capacity. In addition, the stiffness, bearing capacity and energy dissipation capacity of the double beam-column joint are significantly better than that of the single beam-column joint. The ductility coefficients of the single beam-column joint and double beam-column joint are 1.81 and 1.92, respectively. The cracks grow fast when subjected to dynamic loading, and the strength and stiffness degradation is also degenerated quickly.

• Journal of Plant Biology
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• v.36 no.2
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• pp.127-132
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• 1993

Self-incompatibility in Brassica campestris is controlled by multi-allele system in a single genetic locus, the S locus, and it is elucidated that S-glycoproteins are S gene products. In this experiments, we examined the genetic mode(pollen tube behavior and segregation of S-glycoprotein), characteristic of S-glycoproteins and DNA constitution within nuclear genome on S gene family that unexplained by single locus model, and investigated the segregation pattern of S-glycoproteins in bred F1 generation. By diallel cross among the 15 plants within one family the existence of three types of homozygotes and three types of heterozygotes were observed, and segregation of S-allele could not explained by single locus model. From the results of IEF-immunoblot analysis for non-segregated individual plant, the segregation pattern of S specific bands was corresponded with results of diallel cross except with one case(SaSa genotype). The molecular weight of 6 different S-genotype varied in near by 50 kD, and each genotype expressed with 2 or 3 bands. Specific bands in SaSa, SbSb, ScSc has almost similar molecular weight between them. Southern analysis of genomic DNA probed with S-glycoprotein cDNA for 6 different genotypes revealed that there are clear difference in polymorphism, multiple bands of hybridization, when restriction enzymes of EcoR I were used. It could be assumed that there are several sequences related to the S-glycoprotein structural genes within their nuclear genome. Therefore, we suggested the possibilities that S-allele system could be controlled by multi-locus, that dominance-recessive interactions could be explained by modifier gene or supressor gene based on the results of abnormal segregation of S-glycoprotein in bred F1. The F2 analyses are progressing in now.

• Journal of IKEEE
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• v.17 no.2
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• pp.182-188
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• 2013

Using a ceramic target ZnO:In with In doping concentration of 2%, hetero-junctions of n-ZnO:In/p-Si and p-ZnO:(In, N)/n-Si were fabricated by depositing Indium doped n - type ZnO (ZnO:In or IZO) and Indium-nitrogen co-doped p - type ZnO (ZnO:(In, N)) films on wafers of p-Si (100) and n-Si (100) by DC magnetron sputtering, respectively. These films with the best electrical and optical properties were then obtained. The micro-structural, optical and electrical properties of the n-type and p-type semiconductor thinfilms were characterized by X-ray diffraction (XRD), RBS, UV-vis; four-point probe resistance and room-temperature Hall effect measurements, respectively. Typical rectifying behaviors of p-n junction were observed by the current-voltage (I-V) measurement. It shows fairly good rectifying behavior with the fact that the ideality factor and the saturation current of diode are n=11.5, Is=1.5108.10-7 (A) for n-ZnO:In/p-Si hetero-jucntion; n=10.14, Is=3.2689.10-5 (A) for p-ZnO:(In, N)/n-Si, respectively. These results demonstrated the formation of a diode between n-type thin film and p-Si, as well as between p-type thin film and n-Si..

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.233-241
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• 2020

This paper is to investigate the retrofitting effect for a non-seismic reinforced concrete frame strengthened by perimeter steel moment frames with indirect integrity, which ameliorates the problems of the direct integrity method. To achieve this, first, full-scale tests were conducted to address the structural behavior of a two-story non-seismic reinforced concrete frame and a strengthened frame. The non-seismic frame showed a maximum strength of 185 kN because the flexural-shear failure at the bottom end of columns on the first floor was governed, and shear cracks were concentrated at the beam-column joints on the second floor. The strengthened frame possessed a maximum strength of 338 kN, which is more than 1.8 times that of the non-seismic specimen. A considerable decrease in the quantity of cracks for the strengthened frame was observed compared with the non-seismic frame, while there was the obvious appearance of the failure pattern due to the shear crack. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The lateral-resisting capacity for the non-seismic bare frame and the strengthened frame may be reasonably determined per the specified shear strength of the reinforced columns in accordance with the distance to a critical section. The effective depth of the column may be referred to as the longitudinal length from the border between the column and the foundation. The proposed method had an error of about 2.2% for the non-seismic details and about 4.4% for the strengthened frame based on the closed results versus the experimental results.