• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.10-15
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• 2017

The refraction expansion joints have been newly developed by complementing the problems of shock, noise, replaceability, displacement in the direction perpendicular to bridge, vertical difference, which are problems of existing expansion joints. The Refraction expansion joints are characterized by continuous surfaces with small impact and low noise. The behavior of the Refraction expansion joints performs the bridge expansion behavior by rotation of the link. In the rotational behavior of the link, the bolt is the central axis of the behavior. Therefore, it can be said that the durability of the bolt is very important. However, the theoretical and experimental verification of the bolt durability of the Refraction expansion joint is lacking. In this paper, to verify the fatigue durability of the bolt, test specimens with a 300 mm Refraction expansion joint were fabricated. A strain gauge dedicated to the bolt was installed inside the manufactured test specimen bolt. The test method was applied in accordance with KS F 4425. The fatigue durability of the bolts assembled inside the diaphragm expansion joint was confirmed by the repeated fatigue test of 2,000,000 cycles.

• Geotechnical Engineering
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• v.10 no.2
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• pp.41-56
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• 1994

Under the groundwater level, the tunnel face is affected by the seepage force and the groundwater flow may cause a trouble to the tunnel support systems. The appropriate methods of analysis and design in the tunnel face and the lining, considering groundwater flow according to tunnel drainage condition are presented in this thesis. First, the effect of seepage on the stability of tunnel face was studied. Seepage force was estimated by the 3-D finite element analysis and the stability of tunnel face was checked by analytical method. Furthermore, using the finite difference method the stress and displacement on the face were computed for either case, where the seepage force is or is not considered, and the effect of seepage on the tunnel face stability was evaluated. Second, the effect of seepage force on the tunnel lining when construction is finished and steady state seepage flow occurs was studied and a design methodology considering seepage effect was made. Consequently, in case where the groundwater level remains almost unchanged and the steady state groundwater flow occurs, the proper countermeasures for face staility are required according to the condition of groundwater flow. Moreover, the tunnel lining should be designed and constructed considering the seepage force occuring by the groundwater flow toward the tunnel linings.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.1
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• pp.15-29
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• 2005

Statement of problem. The adjustable dental impression trays were made for being adjusted their width automatically along the width of dental arch. Purpose. The purpose of this study was to investigate the best retentive form of adjustable dental impression tray, and so to make it a more satisfactory product. Material and methods. The eight pairs of adjustable trays were made of ABS(acrylonitrile butadiene styrene) with different distribution of holes and with or without the rim on the border area of them. The experiment was done with the horse-shoe shaped metal plate to pull out the set impression body from the tray, and the tray jig which was made for holding the tray on a lower part of Universal Testing Machine(UTM, Zwick Z020, Zwick Co., Germany). After the impression in the tray was allowed to set four minutes, a tensile force was applied at right angles to the tray which had been previously seated on the jig. The force was applied to measure a maximum retentive force by use of a UTM at a constant strain rate of 100mm per minute. A 2-factor analysis of variance (p<.05) was used to determine whether differences existed among distribution of retentive holes and between rim existing and not. Results. 1 The retentive force of the upper and lower resin tray with 2mm holes on the tray border was highest(25.83/24.98kg). (p<.05) 2. As the tray had more retentive holes, it was less retentive. 3. There was no significant difference in the retentive force of the varied hole intervals in the case of distributing all the area. (p>.05) 4. The rimless trays were more retentive generally, than the rimmed trays except 2 case: upper tray group-all area / 2 mm, intervals and lower tray group-margin only / 2 mm, intervals.(p<.05) 5. Most of the adjustable trays were showed higher retentive force than perforated metal tray except the lower group that perforated on the all area at intervals of 2 mm.

• Food Science and Preservation
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• v.8 no.4
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• pp.356-361
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• 2001

This study was conducted to improve the storability of onion bulbs by assembly simple house storage and the reduce the rotteness caused by field open storage. Allium cepa cv. Changnyungdeago, late strain was used for the test at the storage condition of natural ventilation of levels 2, forced ventilation of levels 2, field open storage and 75mm, 100mm, and 125mm ventilating holes. Mean tamperature and relative humidity were not significantly different by ventilation conditions. Mean temperature was lower in forced ventilation than that of in natural ventilation and non-ventilation, and relative humidity was a little higher in ventilation treatment than those of the others. Weight loss of onion bulbs were 2.5%, 2.9%, 3%, 4.3% in field open storage, non ventilation, natural ventilation of levels 2 and forced ventilation of levels 2 respectively. Rotting rate in natural ventilation of levels 2 and farced ventilation of levels 2 were 27.7% and 25.4% respectively but 34.6% and 37.8% in non ventilation and field open storage. Therefore, the treatment of ventilation reduced the rotteness of storage onion bulbs. The smaller the size of a ventilating hole, the lower mean temperature was maintained. The relative humidity was some high in July, but didn’t showed significantly difference in August and September. With small size of a ventilating hole, the strong wind velocity was obtained, and wind velocity by position was weaker in the middle part than both ends. Rutting rates in 75㎜, 100㎜, and 125㎜ ventilating holes were 17.9%, 15.3% and 14.1% respectively.

• The Korean Journal of Zoology
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• v.16 no.2
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• pp.127-137
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• 1973

Monosodium glutamate(MSG) is a widely used food additive. Some reports descried its positive effect and the others, negative effect on mouse, monkey, human or drosophilid flies. Because of the conflicting reports the present investigation was undertaken to study the effects of MSG on the development of Drosophila melanogaster. The two strains of D. melanogaster, Oregon-R and Sinchon-I were used and MSG as well as cane sugar (as the second control) media were prepared by adding MSG or cane sugar at various concentrations to the standard food media for the present study. Ten flies (Male 5, Female 5) were placed in each vial and the numbers of $F_1$ flies emerged from it were counted. The results are presented below: 1. The numbers of $F_1$ flies decrease as the concentrations of MSG increase, implying that MSG has an inhibitory effect in the development of D. melanogaster. 2. The effects of cane sugar show an enhancing effect rather than an inhibitory one. 3. The numbers of $F_1$ fies produced in the Sinchon-I strain are greater than in the Oregon-R. This may be due to the difference in the length of inbred period. 4. The Muller-5 test shows a negative result, suggesting that MSG may be not mutagenic.

• Journal of Life Science
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• v.25 no.2
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• pp.214-222
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• 2015

Aeromonas hydrophila is the most common water fish pathogen and cause diseases such as hemorrhagic septicemia, dropsy, ulceration and asymptomatic septicemia. A. hydrophila secretes many extracellular products (ECPs) which contribute to effective infection, wide distribution and great adaptability to environmental changes. Crude ECPs of A. hydrophila CK257, a strain used in this study, exhibits a toxic activity to the animals including mouse, rabbit and fish. Toxic symptoms were indicated by tissue damage and skin injuries in animal. When ECPs were subcutaneously injected to animals, skin damages were observed, appearing like necrosis. Preliminary research demonstrated that the active factors are protein component. The crude ECPs were collected after ammonium sulfate precipitation of cell-free culture supernatant. ECPs were fractionated with the use gel filtration chromatography. Five ECP fractions were obtained, of which one fraction was found to be toxic to goldfish. MALDI-TOF analyses provided two interesting proteases called M35 and M28. Both M35 and M28 are known as metalloprotease. Accordingly, proteins in an active fraction exhibited caseinolytic activity. These proteins were difference of caseinolytic activity under different metallic ions. Also active fraction has elastolytic activity. These results suggested that peptidase M28 and M35 may be a candidate factor for tissue necrosis activity about infection with A. hydrophila.

• Korean Journal of Microbiology
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• v.30 no.5
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• pp.371-376
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• 1992

Plasmid pSL4 of plasmid pKM 101 mutant have high protection effects and mutagenecity for UV and methyl methanesulfonate, The mucA gene and a pan of mucE gene of pKM 101 and pSL4 were sucloned onto lacZ' fusion vector pMC874 and the hybrid plasmids pBH31 and pBH30 were selected. These plsmids were intrduced into $recA^{+}lexA^{-}$, $recA^{-}와lexA^{+}$ strains and determined the activity of $\beta$-galactosidase for UV. In $recA^{+}lexA^{+}$ strain.$\beta$-galactosidase activity of pBH30 included mue region of pSL4 was higher thall pBH31 inclued muc region of pKM 10 I and the tf-galactosidase of two plasmids was not induced in reeA and leeA mutants with or without UV illumination. Without UV illumination. the .$\beta$-galactosidasc of pBH30 was expressed a little higher level than that of pBH3L We suggest that the functional difference of pKM 10l and pSL4 are due to the variety of mue regulatory region. Also. a plasmid pBH 100 earring umuC' -lacZ' gene fusion was constructed in vitro to study the regulation of the umu operon. It was shown that the umu operon is induced by UV and is regulated by the reeA and lexA genes.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.43-50
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• 2016

A reinforcement is required to ensure the structural safety in case of railway embankment excavation under railway load. A large diameter soil nailing with concrete wall is applied as the reinforcement method instead of the conventional soil nailing system. In this study, a series of 3 dimensional numerical analyses are performed to investigate the optimum reinforcement considering 15 different conditions based on the length, lateral spacing, diameter, and inclination of the reinforcement. The interface between soil nail and perimetric grout is considered by means of cohesion, stiffness and perimeter of the grout. 0.3 m of reinforcement diameter is assessed as the most appropriate based on the economical viewpoint though ground displacement decreases with the increase of diameter, however the difference of displacement is negligible between 0.4 m and 0.3 m of diameter. Surface settlement, lateral displacement of wall, and stress of reinforcement are calculated and economic viewpoint to reinforce embankment considered. Consequently, the optimum reinforcement conditions considering those factors are evaluated as 3 m in length, 0.3 m in diameter, 1.5 m in lateral spacing, and 10 degree of inclination angle in the case of 3 m of excavation depth. Additionally, inclined potential failure surface occurs with approximately 60 degrees from the end of nails and the surface settlement and wall lateral displacement are restrained successfully by the large diameter soil nailing, based on the result of shear strain rate.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.63-70
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• 2014

Design sensitivity analysis and topology design optimization for a piezoelectric crystal resonator are developed. The piezoelectric crystal resonator is deformed mechanically when subjected to electric charge on the electrodes, or vice versa. The Mindlin plate theory with higher-order interpolations along thickness direction is employed for analyzing the thickness-shear vibrations of the crystal resonator. Thin electrode plates are masked on the top and bottom layers of the crystal plate in order to enforce to vibrate it or detect electric signals. Although the electrode is very thin, its weight and shape could change the performance of the resonators. Thus, the design variables are the bulk material densities corresponding to the mass of masking electrode plates. An optimization problem is formulated to find the optimal topology of electrodes, maximizing the thickness-shear contribution of strain energy at the desired motion and restricting the allowable volume and area of masking plates. The necessary design gradients for the thickness-shear frequency(eigenvalue) and the corresponding mode shape(eigenvector) are computed very efficiently and accurately using the analytical design sensitivity analysis method using the eigenvector expansion concept. Through some demonstrative numerical examples, the design sensitivity analysis method is verified to be very efficient and accurate by comparing with the finite difference method. It is also observed that the optimal electrode design yields an improved mode shape and thickness-shear energy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.2
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• pp.121-128
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• 2020

The purpose of this study is to investigate the distribution patterns of displacement and acceleration fields in a nonlinear soil ground based on the interaction of high-speed train, wheel, rail, and ground. For this purpose, a high-speed train in motion was modeled as the actual wheel, and the vertical contact of wheel and rail and the lateral contact, caused by meandering motion, were simulated; this simulation was based on the moving mass analysis. The soil ground part was given the nonlinear behavior of the upper ground part by using the modified the Drucker-Prager model, and the changes in displacement and acceleration were compared with the behavior of the elastic and inelastic grounds. Using this analysis, the displacement and acceleration ranges close to the actual ground behavior were addressed. Additionally, the von-Mises stress and equivalent plastic strain at the ground were examined. Further, the equivalent plastic and total volumetric strains at each failure surface were examined. The variation in stresses, such as vertical stress, transverse pressure, and longitudinal restraint pressure of wheel-rail contact, with the time history was investigated using moving mass. In the case of nonlinear ground model, the displacement difference obtained based on the train travel is not large when compared to that of the elastic ground model, while the acceleration is caused to generate a large decrease.