• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.127-134
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• 2004

Rammed Aggregate Pier (RAP) has extensive applicability as for a foundation of structures. In this study, bearing capacity of the reinforced ground by RAP and the failure behavior of RAP are investigated through experiments. RAPs with diameters of 45, 60, 70 mm were installed in sand, of which relative densities are 60, 70, 90%. Then, two columns of pressure gauges, near the RAPs and one diameter off from the center of piers, are installed 5, 10, 15, 20, 25, 30 cm from the surface of the ground. The test results show that maximum lateral earth pressure is observed near 5∼10 cm (1.0∼2.0D) from the surface, which indicates the occurrence of bulging failure type. In addition, deformation of RAP in radial direction increases with lower relative density of the ground. Furthermore, lateral stress distribution decreases with depth.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1149-1164
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• 1997

In this study, the applicability of the RNG k-.epsilon. model to the analysis of the complex flows is studied. The governing equations based on a non-orthogonal coordinate formulation with Cartesian velocity components are used and discretized by the finite volume method with non-staggered variable arrangements. The predicted results using the RNG k-.epsilon. model of three complex flows, i.e., the flow over a backward-facing step and a blunt flat plate, the flow around a 2D model car are compared to these from the standard k-.epsilon. model and experimental data. That of the unsteady axisymmetric turbulent flow within a cylinder of reciprocating model engine including port/valve assembly and the spray characteristics within a chamber of direct injection model engine are compared to these from the standard k-.epsilon. model and experimental data. The results of reattachment length, separated eddy size, average surface pressure distribution using the RNG k-.epsilon. model show more reasonable trends comparing with the experimental data than those using the modified k-.epsilon. model. Although the predicted rms velocity using the modified k-.epsilon. model is lower considerably than the experimental data in incylinder flow with poppet valve, predicted axial and radial velocity distributions at the valve exit and in-cylinder region show good agreements with the experimental data. The spray tip penetration predicted using the RNG k-.epsilon. model is more close to the experimental data than that using the modified k-.epsilon. model. The application of the RNG k-.epsilon. model seems to have some potential for the simulations of the unsteady turbulent flow within a port/valve-cylinder assembly and the spray characteristics over the modified k-.epsilon. model.

• The Plant Pathology Journal
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• v.36 no.4
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• pp.314-322
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• 2020

Interplay between histone acetylation and deacetylation is one of the key components in epigenetic regulation of transcription. Here we report the requirement of MoHDA1-mediated histone deacetylation during asexual development and pathogenesis for the rice blast fungus, Magnaporthe oryzae. Structural similarity and phylogenetic analysis suggested that MoHDA1 is an ortholog of Saccharomyces cerevisiae Hda1, which is a representative member of class II histone deacetylases. Targeted deletion of MoHDA1 caused a little decrease in radial growth and large reduction in asexual sporulation. Comparison of acetylation levels for H3K9 and H3K14 showed that lack of MoHDA1 gene led to significant increase in H3K9 and H3K14 acetylation level, compared to the wild-type and complementation strain, confirming that it is a bona fide histone deacetylase. Expression analysis on some of the key genes involved in asexual reproduction under sporulation-promoting condition showed almost no differences among strains, except for MoCON6 gene, which was up-regulated more than 6-fold in the mutant than wild-type. Although the deletion mutant displayed little defects in germination and subsequent appressorium formation, the mutant was compromised in its ability to cause disease. Wound-inoculation showed that the mutant is impaired in invasive growth as well. We found that the mutant was defective in appressorium-mediated penetration of host, but did not lose the ability to grow on the media containing H₂O₂. Taken together, our data suggest that MoHDA1-dependent histone deacetylation is important for efficient asexual development and infection of host plants in M. oryzae.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.6
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• pp.391-399
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• 2020

In this study, the behaviors of a suction cap shaped as an arch were analyzed using finite element models. The fundamental structural behaviors of both flat- and arch-type caps were compared, and the advantages of the arch-shaped cap were explained. Moreover, the effects of geometric parameters and stiffener arrangements on the stress and deformation of the arch-shaped caps were investigated by comparisons of the changes in the behaviors of the caps. Additionally, the effects of boundary condition at the edge of the cap were analyzed to study the interactions between the cap and cofferdam walls; these results were used to derive the fundamental structural design of stiffened arch caps. Unlike flat caps, the results showed that ring stiffeners could improve the structural behaviors of arch caps remarkably, while the contributions of the radial stiffeners to the structural behaviors of the caps are dependent on constraints at the edges of the caps.

• Journal of the Korean Geotechnical Society
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• v.38 no.9
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• pp.53-67
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• 2022

Micropiles are cast-in-place-type piles with small diameters. They are widely used for the foundation reinforcement of existing buildings and structures because this technique is easy to construct and economic. A base expansion structure is developed following the mechanism of radial expansion at the pile tip under compression. Numerical analysis, durability tests, and centrifuge tests have been conducted using the base expansion structure. In this study, three-dimensional numerical modeling was performed to describe the behavioral mechanism of the base expansion structure using steel bar penetration under compressive loading, and numerical analyses using centrifuge test conditions were performed for the comparative studies. Additionally, the base structure was modified based on the results of lab-scale analyses, and the bearing capacities of micropiles were compared using field-scale numerical analyses under various ground conditions.

• Restorative Dentistry and Endodontics
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• v.27 no.6
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• pp.577-586
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• 2002

The purpose of this in vitro study was to compare the effects of root canal cleanness following two Ni-Ti rotary instruments with different rake angle. Thirty-six sound, extracted human premolars with single root were randomly divided into three groups. The used rotary instruments were HEROShaper (Group 1, Micro-Mega, Besancon, France, n=12) and ProFile (Group 2, Maillefer, Ballaigues, Switzerland, n=12). Control group (n=12) was only extirpated with barbed broach (Mani, Matsutani Seisakusho Co., Japan) Group 1 & 2 teeth were prepared to a #40/.04 taper at the apex followed by 1 mm using crown-down technique. After canal preparation and frequent irrigation with 5.25% sodium hypochlorite, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. All root specimens were processed for SEM investigation and photographed. Separate evaluations by one endodontist were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. The penetration depth of smear layer into dentinal tubules was also estimated in the other halves. Following results were obtained: 1. Smear layer was observed on all the prepared walls with two experimental groups except control group. 2. Smear layer characteristics in two experimental groups; 1) HEROShaper group showed snowy, dusty appearance and were shown open dentinal tubuli on the prepared walls of almost specimens, and the thickness of smear layer covering onto dentinal surfaces was within 1-2 ${\mu}m$ in a few specimens. 2) ProFile group showed shiny, burnished appearance and complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli in all specimens. The penetration of smear layer into dentinal tubules was found in all specimens and the thickness was at 2-4 ${\mu}m$ in all specimens. These results demonstrated that a completely clean root canal could not be achieved regardless of positive or negative rake angle, which is in accordance with the majority of previous studies on root canal cleanliness In conclusion, through irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal wall in spite of Ni-Ti instrumentation.

• Journal of Conservation Science
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• v.7 no.2
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• pp.60-67
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• 1998

The effects of moisture content (MC) and diffusion period on the diffusion of boron from borate rod through Pinus densiflora and P. koraiensis were investigated as a preliminary research of integrated remedial treatment for heritage wooden structures using borate rod. After equilibrating MCs of samples (15, 25, and 40%), borate rod (1,000 mg) was inserted into the sample, and stored for diffusion of boron at room temperatures ($23^{\circ}C$) for 2, 4, 8, and 12 weeks. Wafers were serially cut at constant intervals from rod treatment point and the boron penetration through longitudinal and transverse direction was measured by staining with boron indicator. For boron diffusion, MC above fiber saturation point was needed, and the diffusion rates increased with time. The fastest rates of diffusion were observed in longitudinal direction, followed by the radial and then the tangential direction. The rates of diffusion in all directions were the fastest in P. koraiensis. In P. densiflora, the diffusion rates through heartwood was faster than that in sapwood in longitudinal direction and vice versa in transverse direction. Based on the best result of this study, optimal space between rod insertion points could be recommended as follows; approximately 120 mm for P. koraiensis and heartwood of P. densiflora, 60 mm for sapwood of P. densiflora in longitudinal direction, and approximately 30 mm for all species tested in transverse direction. However, the effect of rod size and long-term exposure for diffusion on boron movement should be fully investigated for the accurate evaluation of optimal space between rod holes.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Journal of the Korean Wood Science and Technology
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• v.30 no.2
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• pp.128-133
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• 2002

This study was conducted to investigate the influence of storage time on the sapstain development of Japanese red pine and Korean pine logs during storage in log yard, and their stain characteristics. Japanese red pine and Korean pine trees were harvested and cut into logs in mid January of 2001. These logs were transported to the two local sawmills where they were closely stacked in remote parts of log yard. The logs were then sampled destructively by cutting seven to nine 3-cm long discs along the length of each log at intervals of 3, 4, 5, 6, and 8 month after felling. The stain coverage and maximal radial penetration of stain were measured from the discs of the sampled logs after the isolation of causal staining fungi. The sapstain was primarily infested by the attack of bark beetles and the species of bark beetle was identified as Tomicus piniperda. The main fungal species isolated from stained wood was Ophiostoma species. Based on the present study, the logs could be stored in log yard until May without stain; but stain development was rapid after May and the severity of stain increased proportionally with storage time. Korean pine was more susceptible to fungal stain than Japanese red pine. During summer storage, decay started to develop in logs and the main species were identified as Tyromyces sp. and Schizophyllum commune. Information provided in this paper would be very useful to develop more effective control strategies for sapstain prevention in Japanese red pine and Korean pine logs.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.13-44
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• 1982

1. Since long time ago, it has been talked about that soaking wood into water for a long time would be profitable for the decreasing of defects such as checking, cupping and bow due to the undue-shrinking and swelling. There are, however, no any actual data providing this fact definitly, although there are some guesses that water soluble extractives might effect on this problem. On the other hand, this is a few work which has been done about the effect of water soluble extractives upon the some physical properties of wood and that it might be related to the above mentioned problem. If man does account for that whether soaking wood into water for a long time would be profitable for the decreasing of defects due to the undue-shrinking and swelling in comparison with unsoaking wood or not, it may bring a great contribution on the reasonable uses of wood. To account for the effect of water soluble extractives upon physical properties of wood, this study has been made at the wood technology laboratory, School of Forestry, Yale university, under competent guidance of Dr. F. F. Wangaard, with the following three different species which had been provided at the same laboratory. 1. Pinus strobus 2. Quercus borealis 3. Hymenaea courbaril 2. The physical properties investigated in this study are as follows. a. Equilibrium moisture content at different relative humidity conditions. b. Shrinkage value from gre condition to different relative humidity conditions and oven dry condition. c. Swelling value from oven dry condition to different relative humidity conditions. d. Specific gravity 3. In order to investigate the effect of water soluble extractives upon physical properties of wood, the experiment has been carried out with two differently treated specimens, that is, one has been treated into water and the other into sugar solution, and with controlled specimens. 4. The quantity of water soluble extractives of each species and the group of chemical compounds in the extracted liquid from each species have shown in Table 36. Between species, there is some difference in quantity of extractives and group of chemical compounds. 5. In the case of equilibrium moisture contents at different relative humidity condition, (a) Except the desorption case at 80% R. H. C. (Relative Humidity Condition), there is a definite line between untreated specimens and treated specimens that is, untreated specimens hold water more than treated specimens at the same R.H.C. (b) The specimens treated into sugar solution have shown almost the same tendency in results compared with the untreated specimens. (c) Between species, there is no any definite relation in equilibrium moisture content each other, however E. M. C. in heartwood of pine is lesser than in sapwood. This might cause from the difference of wood anatomical structure. 6. In the case of shrinkage, (a) The shrinkage value of the treated specimen into water is more than that of the untreated specimens, except anyone case of heartwood of pine at 80% R. H. C. (b) The shrinkage value of treated specimens in the sugar solution is less than that of the others and has almost the same tendency to the untreated specimens. It would mean that the penetration of some sugar into the wood can decrease the shrinkage value of wood. (c) Between species, the shrinkage value of heartwood of pine is less than sapwood of the same, shrinkage value of oak is the largest, Hymenaea is lesser than oak and more than pine. (d) Directional difference of shrinkage value through all species can also see as other all kind of species previously tested. (e) There is a definite relation in between the difference of shrinkage value of treated and untreated specimens and amount of extractives, that is, increasing extractives gives increasing the difference of shrinkage value between treated and untreated specimens. 7. In the case of swelling, (a) The swelling value of treated specimens is greater than that of the untreated specimens through all cases. (b) In comparison with the tangential direction and radial direction, the swelling value of tangential direction is larger than that of radial direction in the same species. (c) Between species, the largest one in swelling values is oak and the smallest pine heartwood, there are also a tendency that species which shrink more swell also more and, on the contrary, species which shrink lesser swell also lesser than the others. 8. In the case of specific gravity, (a) The specific gravity of the treated specimens is larger than that of untreated specimens. This reversed value between treated and untreated specimens has been resulted from the volume of specimen of oven dry condition. (b) Between species, there are differences, that is, the specific gravity of Hymenaea is the largest one and the sapwood of pine is the smallest. 9. Through this investigation, it has been concluded that soaking wood into plain water before use without any special consideration may bring more hastful results than unsoaking for use of wood. However soaking wood into the some specially provided solutions such as salt water or inorganic matter may be dissolved in it, can be profitable for the decreasing shrinkage and swelling, checking, shaking and bow etc. if soaking wood into plain water might bring the decreasing defects, it might come from even shrinking and swelling through all dimension.