• Magazine of the Korean Society of Agricultural Engineers
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• v.21 no.2
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• pp.81-103
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• 1979

The weathered granite soil involves problems in its stability in soil structures depending upon the reduction of soil strength due to the water absorption, crushability, and content of colored mineral and feldspar. As an attemt to solve the problems associated with soil stability, the crushability of weathered granite soil was investigated by conducting tests such as compaction test, CBR test, unconfined compression test, direct shear test, triaxial compression test, and permeability test on the five soil samples different in weathering and mineral compositions. The experimental results are summarized as follows: The ratio of increasing dry density in the weathered granite soil was high as the compaction energy was low, while it was low as the compaction energy was increased. The unconfined compressive strength. and CBR value were highest in the dry side rather than in the soil with the optimum moisture content, when the soil was compacted by adjusting water content. However, the unconfined compressive strength of smples, which were compacted and oven dried, were highest in the wet side rather than in soil with the optimum moisture content. As the soil becomes coarse grain, the ratio of specific surface area increased due to increased crushability, and the increasing ratio of the specific surface area decreased as the compaction energy was increased. The highest ratio of grain crushability was attained in the wet side rather than in the soil with the optimum moisture content. Such tendency was transforming to the dry side as the compaction energy was increased. The effect of water on the grain crushability of soil was high in the coarse grained soil. The specific surface area of WK soil sample, when compacted under the condition of air dried and under the optimum moisture content, was constant regardless of the compaction energy. When the weathered granite soil and river sand with the same grain size were compacted with low compaction energy, the weathered granite soil with crushability had higher dry density than river sand. However, when the compaction energy reached to certain point over limitation, the river sand had higher dry density than the weathered granite soil. The coefficient of permeability was lowest in the wet side rather than in the optimum moisture content, when the soil was compacted by adjusting soil water content. The reduction of permeability of soil due to the compaction was more apparent in the weathered granite soil than in the river sand. The highly significant correlation coefficient was obtained between the amount of particle breakage and dry density of the compacted soil.

• Advances in concrete construction
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• v.9 no.5
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• pp.437-448
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• 2020

In high rise buildings that utilize precast large panel system for construction, the shear wall provides strength and stiffness during earthquakes. The performance of a wall panel system depends mainly on the type of connection used to transfer the forces from one wall element to another wall element. This paper presents an experimental investigation on different types of construction detailing of the precast wall to wall vertical connections under reverse cyclic loading. One of the commonly used connections in India to connect wall to wall panel is the loop bar connection. Hence for this study, three types of wet connections and one type of dry connection namely: Staggered loop bar connection, Equally spaced loop bar connection, U-Hook connection, and Channel connection respectively were used to connect the precast walls. One third scale model of the wall was used for this study. The main objective of the experimental work is to evaluate the performance of the wall to wall connections in terms of hysteretic behaviour, ultimate load carrying capacity, energy dissipation capacity, stiffness degradation, ductility, viscous damping ratio, and crack pattern. All the connections exhibited similar load carrying capacity. The U-Hook connection exhibited higher ductility and energy dissipation when compared to the other three connections.

• Journal of the Korean Wood Science and Technology
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• v.24 no.2
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• pp.42-45
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• 1996

A residue from the newsprint waste was investigated as a filler in adhesive for bonding southern pine plywood. The residue was prepared by drying the wet residue to 8% moisture content and grinding the dry material using a laboratory Wiley mitt with a 75-${\mu}m$(200-mesh) screen. The residue was compared to a commercial filler commonly used in structural plywood adhesives. A total of 48 three-ply panels. 12.7mm nominal thickness and 0.3 by 0.3 m in size, were fabricated at two press times(4 and 5 min) and three assembly times(20, 40 and 60 min). Evaluations of the residue were carried out by performance tension shear tests after two 4-hour boil accelerated aging tests on plywood. The test results included tension shear strength and estimated wood failure values. All plywood made with the residue filler were comparable to the control-bonded plywood. These results indicate that residue from the newsprint waste streams would be suitable as filler for plywood adhesives.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.28-31
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• 1999

Carbon fiber/epoxy composites using electrodeposited monomeric and polymeric coupling agents were compared with the dipping and the untreated cases. Treating conditions such as time, concentration and temperature were optimized. Four-fibers embedded micro-composites were prepared for fragmentation test. Interfacial properties of four-fiber composites with different surface treatments were investigated with simultaneous acoustic emission (AE) monitoring. The microfailure mechanisms occurring from fiber break, matrix and interlayer crackings were examined by AE parameters and an optical microscope. It was found that interfacial shear strength (IFSS) of electrodeposited carbon fibers was much higher than the other cases under dry and wet conditions. Well separated and different-shaped AE groups occurs for the untreated and ED treated case, respectively.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.4
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• pp.91-98
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• 2012

This study was carried out in order to evaluate the effects of ultra fine precipitated calcium carbonate (UFPCC) on properties of coating color, coated paper and off-set printability. It was found that blending of UFPCC increased the low-shear viscosity and water retention of coating color. The smaller the particle size, the more significant the effect of it. When the blending ratio of UFPCC was increased, brightness, whiteness and opacity of the coated paper were improved, while paper gloss was decreased due to the increase in roughness. When the UFPCC with the average particle size of $0.12{\mu}m$ was used, the ink receptivity during off-set printing was improved while print gloss was maintained or a little decreased. It was also observed that the dry-pick and wet-pick strength of coated paper were improved by the use of UFPCC. In conclusion, it is possible to produce the low gloss matt paper with the use of UFPCC since it could improve the optical properties and ink receptivity of coated paper.

• The korean journal of orthodontics
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• v.33 no.1 s.96
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• pp.51-61
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• 2003

The purpose of this study was to evaluate the effects of a self-etching primer on the shear bond strength of orthodontic brackets and on the failure pattern of bracket-adhesive interfaces in dry or wet condition. Brackets were bonded to extracted human teeth according to one of three experimental protocols. In the Group P, teeth were etched with $37\%$ phosphoric acid. After the Transbond XT Primer was applied onto the etched surfaces, the brackets were bonded with Transbond XT(3M, Unitek, Monrovia, Calif) and light cured for 40 seconds. In the Group SD, a self-etching primer(3M, Unitek, Monrovia, Calif) was placed on the enamel for 3 seconds and gently evaporated with air, as suggested by the manufacturer. The brackets were then bonded with Transbond XT as in the Group P In the Group SW, artificial saliva was applied to the enamel surface for 10 seconds to allow complete hydration of the surface before application self-etching primer The brackets were then bonded following the procedures of Group SD. Each group was divided into 2 sub-groups(0.5h, 24h) according to debonding time. Shear bond strengths were measured by Instron universal testing machine. After debonding, the teeth and brackets were examined under scanning electron microscope and assessed with the adhesive remnant index. The result obtained were summarized as follows ; 1. The shear bond strengths were high enough to use clinically in all testing groups, but the shear bond strengths of Group SD and SW were significantly lower than Group P(p<0.05). 2. With respect to comparison of debonding time, 24h debonding samples exhibited heigher shear bond strength than 0.5h debonding samples in Group P, SD and SW(p<0.05). 3. In the self etching primer groups(Group SD and Group SW), there was no significant difference in mean shear bond strength between under dry and wet state(p>0.05). 4. There was a greater frequency of ARI score of 0 and 1 with the Group P. On the other hand, there was a higher frequency of ARI scores of 2 and 3 with Group SD and Group SW(p<0.05).

• Journal of the Korean Wood Science and Technology
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• v.18 no.2
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• pp.67-78
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• 1990

This study was performed to determine the characteristics of physical and mechanical properties of domestic wood based materials; plywood, particleboard, medium density fiberboard. Main items of tested properties were panel size, moisture content, water absorption, linear expansion and thickness swelling, glue bond shear strength, bending properties(stress at proportional limit, modulus of rupture. modulus of elasticity), tensile strength, screw holding strength, and internal bond as neccessary. the results were discussed mainly with Korean Standards. The obtained conclusions are as follows; 1. Length and width of 3mm thin plywood(3-ply) and 12mm thick plywood(7-ply) were satished with KS-standard, but thicknesses of these panels were not- passed tolerance limit except one of eight makers. 2. Length and width of particleboard and medium density fiberboard were greater than the tolerance limit value of KS standard, but the thicknesses of these panels were passed this value. 3. Moisture contents of 12mm thick and 3mm thin plywood were satisfied with KS-standard except one mill made 3mm thin plywood. 4. Moisture absortion of plywood was not passed tolerance limit of KS-standard but particleboard was satisfied with this standard value. 5. Dry and wet shear strengths in glue bond of 3mm thin plywood were not reached to KS-standard, but those of 12mm thick plywood were sufficiently satisfied with KS standrad. 6. Modulus of ruptures, parallel to grain and perpendicular to grain of plywood, and particleboard and medium density fiberboard were satisfied with KS-standard. 7. Tensile strengths, parallel to grain and perpendicular to grain of plywood were satisfied with allowance stress of US product standard PS 1-74. 8. Screw holding strength of particleboard was not reached to KS standard, but internal bond was satisfied with KS standard.

• Journal of the Korean Wood Science and Technology
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• v.12 no.1
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• pp.3-10
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• 1984

Taro-UF mixed type resin system was developed for gluing plywoods. The taro adhesive that was activated with sodium hydroxide was mixed with the definite ratios of UF resin adhesive. At the sametime, wheat-UF mixed type resin was also applied with the same method as taro-UF mixed type resin The mixing ratios of taro or wheat adhesive: UF resin were 0:100, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 80:20, and 100:0 by weight. In addition, the UF resins extended with wheat powder at the extending ratios of wheat powder UF resin, 10:90, 20:80, 30:70, 40:60, and 50:50 by weight, were also used. The dry and wet shear strengths of the plywoods of 30:70 (taro adhesive : UF resin) mixing ratio were highest. The dry shear strengths of the plywoods manufactured with the UF resin-mixing taro adhesive were higher than those of the plywoods with the UF resin-mixing wheat adhesive at 10:90, 20:80, 30:70, 40:60, 50:50, and 60:40 (taro or wheat adhesive: UF resin) mixing ratios. At all mixing ratios, the wet shear strengths of the plywoods manufactured with the UF resin-mixing taro adhesive were higher than those of the plywoods with the UF resin-mixing wheat adhesive. The dry and wet shear strengths of the plywoods manufactured with the UF resin-mixing wheat adhesive were higher than those of the plywoods with the wheat powder-extending UF resin at the mixmg ratios, 10:90, 20:80, 30:70, and 40:60 (wheat adhesive or wheat powder: UF resin). So, it was found that the plywoods manufactured with the UF resin-mixing taro adhesive and the UF resin mixing wheat adhesive had better shear strength than the plywoods with the wheat powder-extending UF resin. It was because the taro adhesive and wheat adhesive themselves took the bonding properties after being activated with alkali.

• Journal of the Korean Wood Science and Technology
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• v.14 no.2
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• pp.29-35
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• 1986

This study was carried out to examine the effect of aluminium sulfate addition to the alkali-acid catalyst phenolic resin for the manufacture of the kapur (Dryobalanops spp.) plywood on the reduction of phenolic resin spreading. On the manufacture of plywood, Adhesive Contents such as 50g/$m^2$, 75g/$m^2$ and 150g/$m^2$ were treated. The spreading adhesive content of 50g/$m^2$ and 75g/$m^2$ had been controlled to about 150g/$m^2$ added with the water in order to get sufficient spreading and controlled to pH 4.5 with aluminium sulfate [$Al_2(SO_4)_3$]. The results are summarized as follows: 1. Specific gravities of air dried plywood manufactured from each adhesive ranged from 0.77 to 0.86 and their moisture contents met the KS requirements. 2. In dry and wet shear strengths, 150 $P_{Al{\cdot}Ac}$ adhesive showed the highest and 75 $P_{Al{\cdot}Ac{\cdot}Am}$ adhesive indicated higher value than 150 $P_{Al{\cdot}Ac}$ adhesive. 3. In case of glue shear strength after boiling test, 150 $P_{Al{\cdot}Ac}$ adhesive was the best and adding of aluminium sulfate was not effective on reinforcement of boiling water resistance of phenolic resin, but met KS requirements. 4. 75 $P_{Al{\cdot}Ac{\cdot}Am}$ adhesive showed the good shear strength and met KS requirements. Therefore, adding of aluminium sulfate was very efficient for economical plywood manufacture.

• Economic and Environmental Geology
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• v.40 no.6
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• pp.771-784
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• 2007

This study shows the weathering characteristics of mica-schist affected by faulting and metamorphism through laboratory tests. Frozen-thaw test, which simulate the physical-chemical weathering processes in the laboratory, shows the important influence of foliation developed in mica-schist, resulting in $20{\sim}40%$ reduction of UCS according to weathering grade of rock. Slaking durability test was carried out for different weathering grade rock specimens and indicated that the specimens from fault area had a low durability index compared to other relatively fresh samples. XRD analysis allowed to estimate the dynamic evolution of mineral composition through wet-dry cycle in which the chlorite was the most important mineral leached out during slaking test. The creep test indicated that the main deformation produced along the foliation plane. The compacted clay minerals between discontinuity planes influence on the discontinuity shearing properties and result in a big difference between peak shear strength and residual strength. The results of laboratory tests on mica-schist show the possibility of a important deformation along the foliation plane or discontinuity.