• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.241-257
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• 2020

The rapid proliferation of oil/gas drilling and wind turbine installations with jack-up rig-formed structures increases structural safety requirements, due to the greater risks of operational collisions during use of these structures. Therefore, current industrial practices and regulations have tended to increase the required accidental collision design loads (impact energies) for jack-up rigs. However, the existing simplified design approach tends to be limited to the design and prediction of local members due to the difficulty in applying the increased uniform impact energy to a brace member without regard for the member's position. It is therefore necessary to define accidental load estimation in terms of a reasonable collision scenario and its application to the structural response analysis. We found by a collision probabilistic approach that the kinetic energy ranged from a minimum of 9 MJ to a maximum 1049 MJ. Only 6% of these values are less than the 35 MJ recommendation of DNV-GL (2013). This study assumed and applied a representative design load of 196.2 MN for an impact load of 20,000 tons. Based on this design load, the detailed design of a leg structure was numerically verified via an FE analysis comprising three categories: linear analysis, buckling analysis and progressive collapse analysis. Based on the numerical results from this analysis, it was possible to predict the collapse mode and position of each member in relation to the collision load. This study provided a collision strength assessment between attendant vessels and a jack-up rig based on probabilistic collision scenarios and nonlinear structural analysis. The numerical results of this study also afforded reasonable evaluation criteria and specific evaluation procedures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.457-464
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• 2006

Fiber-reinforced composite materials due to their high specific strength, high stiffness and light weight are becoming increasingly used in many engineering industry, especially in the aerospace, marin and civil, etc. In this paper, the buckling load and mode shapes of composite laminates with elliptical cross-section including transverse shear deformations are analyzed. For solving this problems, a versatile flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. Also, an improved shell element has been established by the combined use of the addition of enhanced assumed strain and the substitute shear strain fields. The combined influence of shell geometry and elliptical cross-sectional parameter, fiber angle, and lay-up on the buckling loads of elliptical cylinder is examined. The critical buckling loads and mode shapes analyzed here may serve as a benchmark for future investigations.

• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.413-422
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• 2022

Barnea manilensis is a bivalve which bores soft rocks, such as, limestone or mudstone in the low intertidal zone. They make burrows which have narrow entrances and wide interiors and live in these burrows for a lifetime. In this study, the morphology and the microstructure of the valve of rock-boring clam B. manilensis were observed using a stereoscopic microscope and FE-SEM, respectively. The chemical composition of specific part of the valve was assessed by energy dispersive X-ray spectroscopy (EDS) analysis. 3D modeling and structural dynamic analysis were used to simulate the boring behavior of B. manilensis. Microscopy results showed that the valve was asymmetric with plow-like spikes which were located on the anterior surface of the valve and were distributed in a specific direction. The anterior parts of the valve were thicker than the posterior parts. EDS results indicated that the valve mainly consisted of calcium carbonate, while metal elements, such as, Al, Si, Mn, Fe, and Mg were detected on the outer surface of the anterior spikes. It was assumed that the metal elements increased the strength of the valve, thus helping the B. manilensis to bore sediment. The simulation showed that spikes located on the anterior part of the valve received a load at all angles. It was suggested that the anterior part of the shell received the load while drilling rocks. The boring mechanism using the amorphous valve of B. manilensis is expected to be used as basic data to devise an efficient drilling mechanism.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.383-399
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• 2020

Optimizing the spacing of the disc cutter is a key element in the design of the TBM cutter head, which determines the drilling performance of the TBM. The full-scale linear cutting test is known as the most reliable and accurate test for calculating the spacing of the disc cutter, but it has the disadvantage of costly and time-consuming for the full-scale experiment. In this study, through the numerical analysis study based on the discrete element method, the tendency between Specific Energy-S/P ratio according to uniaxial compression strength and penetration depth of rock was analyzed, and the optimum spacing of 17-inch disc cutter was derived. To examine the appropriateness of the numerical analysis model, the rolling force acting on the disc cutter was compared and reviewed with the CSM model. As a result of numerical analysis for the linear cutting test, the rolling force acting on the disc cutter was analyzed to be similar to the rolling force derived from the theoretical formula of the CSM model. From the numerical analysis on 5 UCS cases (50 MPa, 70 MPa, 100 MPa, 150 MPa, 200 MPa), it is found that the range of the optimum spacing of the disc cutter decreases as the rock strength increases. And it can be concluded that 80~100 mm of disc cutter spacing is the optimum range having minimum specific energy regardless of rock strength. This tends to coincide with the optimal spacing of previously reported disk cutters, which underpins the disk cutter spacing calculated through this study.

• Journal of Chest Surgery
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• v.33 no.6
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• pp.494-501
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• 2000

Background: Transmyocardial laser revascularization(TMLR) for revascularizing ischemic myocardium in patients was originally based on the assumption that laser channels remain their patency much longer. But recent studies show that laser channels did not remain open and that TMLR could achieve treatment benefits without long-term channel patency. The angiongencesis is currently thought to be induced by non-specific inflammatory response to mechanical tissue injury. This study is to evaluate hypothesis that various transmyocaridal mechanical revascularization(TMMR) may induce the angiogenic responses similar to that seen with TMLR, and transmyocaridal polymer stent revascularization(TMSR), the polymer stent in the myocardial tissue is hydrolyzed in 2 weeks, may enhance the non-specific inflammatory reaction resulting angiogenesis. Furthermore, polymer myocaridal stent channels remain long-term patency. Material and Method: Eight domestic pigs underwent ligation of the proximal circumflex artery, and 2 weeks later they were randomized to undergo transmycardial acupunctural revascularization (TMPR, Group I) of the left lateral wall with 18-G needle(n=2), to undergo transmyocardial (TMDR, Group II) with industrial 2mm steel drill(n=2), to undergo transmyocardial polymer stent revascularization (TMSR, Group III) after drilling the infarcted myocardium(n=2), the stent is poly(lactic acid-co-glycolic acid), which is self-degradated in the myocardium, and to a control group the ischemic zone was unterated(n=2). All the pigs were sacrificed after 4 weeks TMMR. Sections from the ischemic zone were submitted for vascular endothelial growth factor (VEGF) ELISA and histology. Result: There were makedly increase in the VEGF immunoassay in the ischemic zone of the TMMR group compared to the ischemic zone of the control group(control: each 30.85 and 43.15pg/mg protein, TMPR: each 44.14 and 68.61 pg/mg protein, TMDR: each 65.92 and 78.65 pg/mg protein, TMSR: each 177.39 and 168.87 pg/mg protein). TMSR channels caused greatest VEGF expression than channels made by other group and the polymer stent channels remained vacuole after 4 weeks. Conclusion: Transmyocardial polymer stent revascularization promoted the most angiogenci response by the VEGF immunoassay, although our study did not show the statistical significancy. The channels remained but the flow patency was not verified. Transmyocardial polymer stent revascularization (TMSR) is desirable in future experimental trials and in view of the significant cost implications comparable to that of laser.

• Restorative Dentistry and Endodontics
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• v.27 no.1
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• pp.1-11
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• 2002

Immune responses associated with bacterial infection involve various inflammatory cells. Clinical symptoms and pathologic features are particularly influenced by the predominant cells Among inflammatory cells, T cells have the heterogenity. T cells may develop into the mature cells expressing the cell surface markers with different functions and T helper cells are categorized into Th1 and Th2 cells based on their different patterns of cytokine production. The objective of this study was to investigate the change of expression of surface markers on T cells and the Th1/Th2 immune response in pulpal inflammation associated with specific bacteria. We experimentally induced pulpal inflammation in rat incisors by drilling without coolant and innoculated with Streptococcus mutans (S.M. group), Porphyromonas endodontalis (P.E. group), or only sterile cotton (control group). After 1, 2, and 5 days, mandibular incisors were extracted and the pulp tissues were extirpated The expressions of IL-2 recepters (CD25) and ICAM-1 (CD54) on CD4+ and CD8+ cells in the pulps were determined using a flow cytometer, and the concentration of IL-2, IFN-$\gamma$ and IL-4 was measured by enzyme-linked immunosorbent assay. The results were as follows: 1 In the S.M. group, CD4+ cells were more increased at 2nd day than 1st day and in the P.E. group, CD8+ cells were more increased at 2nd day than 1st day. 2. The percentages of CD4+, CD4+25+ and CD4+54+ cells were decreased in the pulp tissues at 5th day after irritation in all groups. 3. The ratios of CD4+/CD8+, CD4+/CD4+25+ and CD4+/CD4+54+ in the pulps at 2nd day after irritation by P. endodontalis were significantly lower than the other groups. 4. The higher concentrations of IFN-$\gamma$ than IL-4 in the pulps at 2nd day after irritation by P. endodontalis showed that T helper 1 reaction were predominant in the early stage of the pulpal inflammation induced by P. endodontalis. 5. The higher concentrations of IL-4 than IFN-$\gamma$ in the pulps at 1st day and 5th day after irritation by S. mutans were measured but the differences were not significant.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.1
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• pp.67-75
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• 2023

In this study, the dynamic characteristics of an offshore platform being installed and physical phenomena are analyzed from the perspective of interaction between operation and maneuvering simulation using a real-time Maneuvering & Operation simulator of Shipbuilding & Marine Simulation Center at Tongmyong University. It was simulated to install the semi-submersible drilling rig moored by 8 mooring lines according to a scenario that is similar to it on the real sea, and 4 tug boats for position keeping of the rig and an offshore support vessel for hook-up of the mooring lines were operated. During the simulation, the motion, trajectory, tension of the objects were output in real time, and they were analyzed at each work procedure. This study about the simultaneous simulation of operation and maneuvering showed the detailed motion of the offshore platform and ships on the operation procedure and the interaction between operation and maneuvering in specific environment condition. Also, it confirmed that the simulation can be utilized to determine the possibility of offshore platform installation in specific situations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3C
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• pp.187-196
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• 2008

An earthquake of magnitude 5.0 occurred at Ssang-gye-sa, a Buddhist temple in Jirisan, located near the southern border of the Korean peninsula on 4 July 1936. It resulted in severe damage of several buildings and structures in Ssang-gye-sa. Particularly, the top component of a five-story stone pagoda in the temple was tipped over and fell down during the earthquake. This earthquake damage case would be usefully applied to estimating the intensity of ground motion in the Korean peninsula, a moderate seismicity region, where strong motion has never been recorded with the exception of historic seismic events. In order to estimate the local site effects and the corresponding ground motion at Ssang-gye-sa site, intensive site investigations including borehole drilling and in-situ seismic tests such as crosshole and SASW tests were performed in the temple area. Based on the site characteristics, site-specific seismic response analyses using various input motions were conducted for a representative Ssang-gye-sa site by means of both one-dimensional equivalent-linear and nonlinear methods with six input rock outcrop acceleration levels ranging from 0.044g to 0.220g. The resultant site-specific seismic responses indicated the amplified ground motions in the short-period range near the site period of Ssang-gye-sa. Furthermore, the intensity on rock outcrop of the 1936 Jirisan earthquake was estimated by making a comparison between the site responses analysis results in this study and the full-scaled seismic test of pagoda model in the prior study.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.499-508
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• 2019

Based on the preliminary surveys for the occurrences of the Muwellut chrome-nickel mineralized zone ($800km^2$) in northwestern Myanmar, Bophivum area was selected as the detailed exploration area after considering data source, geological potential, metallogenic province, necessity of resource development on target mineral, exploration activity, grade, ore deposit type, nearby operating mine, infrastructure and exploration prediction effect. From 2013 to 2016, KIGAM and DGSE carried out geological and geochemical survey with 1:1,000 scale, magnetic survey(areal extent, $1.672km^2$), trench survey(19 trench, total length 392 m), pitting survey(18 pit, total depth 42.6m), exploration drilling(6holes 600m, 2015; 13holes 617.4m). We analyzed Cr and Ni contents of 77 drill cores with specific gravity in Yangon DGSE analytical center. Considering surface geological survey, geochemical exploration, magnetic survey, trench survey and drilling data, we divided Bophivum area into 8 blocks. Resource estimation are divided into measured and indicated resources. Measured resource is about 9,790t and indicated resource is about 12,080t with the average grade of Cr 11.8% and Ni 0.34%. In case of Bophivum area, if we develop by tying up Webula chrome mineralized zone in the south, it will be possible to upgrade the medium-scale mine. Geologically, the ophiolite belt are distributed in the western and eastern part in Myanmar. So, the exploration technology obtained from exploation in Bophivum area will be helpful to discover the hidden chromitite ore body in Myanmar ophiolite belt in the future.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2007.05a
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• pp.39-50
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• 2007

Sexing from bovine embryos fertilized in vitro implicates a possibility of the sex controlled cattle production. This study was carried out to produce the sex determined cattle through the embryonic sexing by fluorescence in situ hybridization (FISH) technique. FISH was achieved in in vitro fertilized bovine embryos using a bovine Y-specific DNA probe constructed from the btDYZ-1 sequence. Using this probe, a male-specific signal was detected on 100% of Y-chromosome bearing metaphase specimens. The analyzable rate of embryonic sexing by FISH technique was about 93% (365/393) regardless of embryonic stages. As tested single blastomere by FISH and then karyotype with their biopsied embryos, the accuracy of sex determination with FISH was 97.6%. We tried the embryo transfer with sex determined embryos on 15 cattle. Among them, the 5 cattle delivered calf with expected sex last year.