• The Journal of Engineering Geology
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• v.32 no.1
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• pp.13-26
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• 2022

Calcite twins were analyzed in six oriented samples of the Pungchon limestone, Joseon Supergroup, to reconstruct the paleostress field. The orientations of c-axis of calcite and e twin plane were measured along with the average thickness and numbers of twins, and the widths of calcite grains. Twin strain, mean width, and intensity of twinning, and the relative magnitude and orientations of principal stresses were calculated using Calcite Strain Gauge program. Twin strain, mean width, and intensity of twinning showed ranges of 1.09-15.36%, 0.53-3.72 ㎛ and 21.0-53.1 twim/mm, respectively. Metamorphic temperatures calculated from the twins were 170-200℃, indicating that the twins developed after the Pungchon limestone was uplifted to at least half of the maximum burial depth. Results for five of the samples indicate that the calcite twins formed during two events with principal stress axes of different orientations, while the remaining sample recorded only one event that produced calcite twins. The axis of maximum compressive stress was oriented mainly WNW-ESE to ENE-WSW, and to a lesser degree NW-SE and NE-SW. Comparison of paleostress orientations measured here and in other studies indicates that most twins were produced during the Songrim orogeny. However, the Daebo orogeny and the Bulguksa orogeny also produced calcite twins in the Punchon limestone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.2
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• pp.33-41
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• 2023

The application of seismic separation joints that can improve the deformation capacity of piping is an effective way to improve seismic performance. Seismic separation joints capable of axial expansion and bending deformation are installed where deformation is expected and used for the purpose of safely protecting the piping. Bellows are flexible and have low stiffness, so they can be used as seismic separation joints because they have excellent ability to respond to relatively large deformation. In this study, the seismic performance and limit state for bending deformation of 2-ply and 3-ply bellows specimens were evaluated. Seismic performance was evaluated by applying an increasing cyclic load to consider low-cycle fatigue due to seismic load. In order to confirm the margin for the limit state of the evaluated seismic performance, an experiment was conducted in which a cyclic loading of constant amplitude was applied. As a result of the experiment, it was confirmed that the bellows specimen was made of stainless steel and had a high elongation, so that the 2-ply bellows specimen had the limit performance of resisting within 3 cycles even at the maximum forced displacement of the 3-ply bellows specimen.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.797-802
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• 2023

We prepared GZO (Ga₂O₃ : 5 wt %, ZnO : 95 wt %) thin film on glass substrate according to the substrate temperature using the pulsed laser deposition method and investigated electrical and optical properties of the thin film. Through the XRD measurements, their were confirmed that all GZO thin films grew preferentially in c-axis and the GZO thin film deposited at 300℃ showed the best crystallinity with a FWHM of 0.38°. As the substrate temperature increased from 150 to 300℃, the resistivity of GZO thin film tend to decrease, while the average transmittance in the visible light region was not significantly affected. The figure of merit of the GZO thin film deposited at 300℃ was 2.05×10⁴ Ω^-1·cm^-1, which was the best value, the resistivity and the average transmittance in the visible light region were 3.72 × 10^-4 Ω·cm and 87.71 %, respectively. In this study, it was found that GZO thin film is very promising material for transparent conducting thin film.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.21-30
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• 1985

The tension leg platform (TLP) is a kind of compliant structures, and is also a type of moored stable platform with a buoyancy exceeding the weight because of having tensioned vertical anchor cables. In this paper, among the various kinds of tension leg structures, Deep Oil Technology (DOT) TLP was analyzed because it has large-displacement portions of the immersed surface such as vertical corner pontoons and small-diameter elongated members such as cross-bracing. It also has results of hydraulic model tests, comparable with theorectical analysis. Because of the vertical axes of symmetry in the three vertical buoyant legs and because there are no larger horizontal buoyant members between these three vertical members, it was decided to develop a numerical algorithm which would predict the dynamic response of the DOT TLP using the previously developed numerical algorithm Floating Vessel Response Simulation (FVRS) for vertically axisymmetric bodies of revolution. In addition, a linearized hydroelastic Morison equation subroutine would be developed to account for the hydrodynamic pressure forces on the small member cross bracing. Interaction between the large buoyant members or small member cross bracings is considered to be negligible and is not included in the analysis. The dynamic response of the DOT TLP in the surge mode is compared with the results of the TLP algorithm for various combinations of diffraction and Morison forces and moments. The results which include the Morison equation are better than the results for diffraction only. This is because the vertically axisymmetric buoyant members are only marginally large enough to consider diffractions effects. The prototype TLP results are expected to be more inertially dominated.

• Korean Journal of Agricultural Science
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• v.13 no.1
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• pp.113-122
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• 1986

In order to promote mechanization of corn harvesting in Korea, this study was conducted to find out the effect of moisture content on compressive properties such as force, deformation, energy and modulus of stiffness to the bioyield and the rupture point for Korean corn kernel. In this study, the loading positions of corn were flat, edge, longitude and the moisture contents were about 13, 17, 21, 25% in wet basis. The compression test was carreied out with flat plate by use of dynamic straingage for three varieties of Korean corn under quasi-static force when the loading rate was 1.125mm/min. The results of this study are summarized as follows; 1. When the moisture content of corn ranged from 12.5 to 24.5 percent, at flat position, the bioyied force was in the range of 13.63-26.73 kg and the maximum compressive strength was in the range of 21.55-47.65kg. Their values were reached minimum at about 17% and maximum at about 21% moisture content. The bioyield force was in the range of 13.58-6.70kg at edge position and the maximum compressive strength which was 16.42 to 7.82kg at edge position was lower than that which was 18.55-9.05kg at longitudinal position. 2. Deformation of corn varied from 0.43 to 1.37 mm at bioyield point and from 0.70 to 2.66mm at rupture point between 12.5 to 24.5% moisture content. As the moisture content increased, deformation was increased. 3. The moduli of resilience and toughness of corn ranged from 2.60 to 8.57kg. mm and from 6.41 to 34.36kg. mm when the moisture content ranged from 12.5 to 24.5 percent, respectively. As the moisture content increased, the modulus of toughness was increased at edge position and decreased at longitudinal position. And their values were equal each other at 22-23% moisture content. 4. The modulus of stiffness was decreased with increase in the moisture content. Its values ranged from 32.07 to 5.86 kg/mm at edge position and from 42.12 to 18.68kg/mm at flat position, respectively. Also, the values of Suweon 19 were higher than those of Buyeo. 5. It was considered that the compressive properties of corn at flat position were more important on the design data for corn harvesting and processing machinery than those of edge or longitudinal position. Also, grinding energy would be minimized when a corn was processed between about 12.5 to 17% moisture content and corn damage would be reduced when a corn was handled between about 19 to 24% moisture content in wet basis.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.21-30
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• 2011

As well known, dowel bars are used to transfer traffic load acting on one edge to another edge of concrete slab in concrete pavement system. The dowel bars widely used in South Korea are round shape steel bar and they shows satisfactory performance under bending stress which is developed by repetitive traffic loading and environment loading. However, they are not invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Especially, the erosion could rapidly progress with saline to prevent frost of snow in winter time. The problem under this circumstance is that the erosion not only drops strength of the steel dower bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem in reasonable expenses, dowers bars with various materials are being developed. Fiber reinforced plastic(FRP) dower that is presented in this paper is suggested as an alternative of the steel dowel bar and it shows competitive resistance against erosion and tensile stress. The FRP dowel bar is developed in tube shape and is filled with high strength no shrinkage. Several slab thickness designs with the FRP dowel bars are performed by evaluating bearing stress between the dowel bar and concrete slab. To calculated the bearing stresses, theoretical formulation and finite element method(FEM) are utilized with material properties measured from laboratory tests. The results show that both FRP tube dowel bars with diameters of 32mm and 40mm satisfy bearing stress requirement for dowel bars. Also, with consideration that lean concrete is typical material to support concrete slab in South Korea, which means low load transfer efficiency and, therefore, low bearing stress, the FRP tube dowel bar can be used as a replacement of round shape steel bar.