• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.123-132
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• 2003

The final purpose of driveability analysis is to confirm whether a selected hammer drives a pile to a desired penetration depth and/or capacity without damage. The capacities from static analysis methods are meaningless if the pile cannot be driven to the required design depth and the ultimate capacity without damage. It often occurs that there are big differences between the capacities from measurements and calculations. It may be because the driveability is not evaluated due to the lack of engineers' understanding of the driveability of pile driving. The engineers in the field sometimes assume simply the penetration depth with standard penetration value only. In this study some test pilings with dynamic pile loading tests were performed to give an understanding about the driveability. The influence factors(driving resistance, impedance, material strength, hammer) on the driveability of steel piles were analysed with the monitoring data obtained from the dynamic load tests. It was shown that more cost-effective design can be made in case the driveability analysis and high strength steel pile are appropriately adopted in the design.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.846-853
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• 2006

In this study, quantitative sensitivity analysis on rockfill material influencing the dam crest displacement of Concrete-Faced Rockfill Dam(CFRD) was carried out. The purpose of this study is to indicate the most important input parameter and to show the quantitative variation of displacement at the crest of CFR type dam with this input parameter. The rockfill material properties for parametric study were obtained from the results of large scale triaxial tests on 34 rockfill materials in the 22 different sites. From the statistical analysis on these data, some statistical characteristics of rockfill material properties such as property range, distribution characteristics, and correlation between the properties were investigated. based on these characteristics, 27 property combinations were constituted by Latin Hypercube sampling method. Dam crest displacements after construction, impounding, and earthquake loading were evaluated by static and dynamic numerical analysis on each combination. From the sensitivity analysis, it was found that the crest displacement of CFR type dam was absolutely affected by the shear modulus of rockfill material and the effect of friction angle of it was negligible. This relative difference of sensitivity was more outstanding in case of crest settlement than in case of crest horizontal displacement. Also, it was found that the settlement and horizontal displacement of dam crest logarithmically decreased as the shear modulus increased and the difference between the maximum value and the minimum vale amounted to about 9.5 times in case of settlement and about 10 times in case of horizontal displacement.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.43-55
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• 2012

In this study, the resistance bias factors are calculated to determine the resistance factor of Gravel Compaction Piles which is one of the soft ground improvement methods. In order to calculate resistance bias factors for gravel compaction piles, two ultimate bearing capacities were analyzed. One is the ultimate bearing capacity in 2.54 cm settlement measured using data of the field loading test on 41 piles and the other is the ultimate bearing capacity calculated using the seven equations concerning bulging failure. The results of analysis show that the probability density function of the calculated ultimate bearing capacities has a lognormal distribution. Resistance bias factor and the coefficient of variation for Greenwood equation are 0.91 and 0.38, respectively, and for those of Hughes & Withers are 1.19 and 0.39. The two equations are suitable for calculating resistance factors for LRFD of soil improvement using gravel compaction piles.

• Journal of the Korea Convergence Society
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• v.8 no.5
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• pp.53-60
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• 2017

This study was conducted to develop the Sexually Transmitted Infections (STI) Knowledge Scale for adolescents. Based on a literature review, the first preliminary 40 questions were created, which content validation by expert reviewers and a pilot study then refined into a draft scale of 29 items. To confirm the validity and reliability of this preliminary scale, data were collected from 141 adolescents between February 13 and 26, 2016: factor analysis resulted in a factor loading of more than .52, while convergent validity revealed that the group receiving STI education was significantly higher (p=.009). The final version of the scale contained 16 items, with a reliability measured by Cronbach's ${\alpha}$ of .85 and the 39.3% of correct answers. The STI knowledge scale developed in this study is a valid scale that can be used to evaluate the effectiveness of STI education for adolescents.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.257-262
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• 2019

Recently, the number of people enjoying various leisure sports has increased. As a result, the vehicles with various items loaded onto the roof can be easily seen on the street. The device that enables loading on the vehicle roof is called by a rack, and each vehicle has its own different shape. There are various types of roof racks but they must have the strength and durability to load heavy loads. In this study, the structural analysis was performed according to the support method of the roof rack and the shape of the fixture. Of three models, it was shown that model C had the best durability. Therefore, this study result shows which shape of the roof rack is most stable among the models. By utilizing the design data about a convergence study through the structural analysis due to the shape of automotive roof rack obtained on the basis of this result, the esthetic feeling can be shown by being converged onto the part of automobile at actual life.

• Journal of the Microelectronics and Packaging Society
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• v.11 no.1
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• pp.87-96
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• 2004

Polymer/ceramic composites are the most promising embedded capacitor material for organic substrates application. Predicting the effective dielectric constant of polymer/ceramic composites is very important for design of composite materials. In this paper, we measured the dielectric constant of epoxy/$BaTiO_3$ composite embedded capacitor films with various $BaTiO_3$ particles loading for 5 different sizes $BaTiO_3$ powders. Experimental data were fitted to several theoretical equations to find the equation useful for the prediction of the effective dielectric constant of polymer/ceramic composites and also to estimate the dielectric constant of $BaTiO_3$ powders. The Lichtenecker equation and the Jayasundere-Smith equation were useful for the prediction of the effective dielectric constant of epoxy/$BaTiO_3$ composites. And calculated dielectric constants of the $BaTiO_3$ powders were in the range of 100 to 600, which were lower than those of $BaTiO_3$ bulk ceramics.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.45-52
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• 2009

This paper experimentally evaluates the strength characteristics of precast column-R.C. foundation anchor joint subjected to the cyclic horizontal load. The study presents differences in accurate stress transfer path and destruction mechanism between the concrete structural body applying the precast column-R.C. foundation anchor joint and the concrete structural body applying the steel joint. the result from width load experiment on reinforcing steel under the cyclic horizontal load provides the necessary minimum insertion length to construct the precast column-R.C. foundation anchor joint. This study also presents the accurate stress transfer path and destruction mechanism on the anchor joint th meet the customer's requirements, comparing stress transfer path and destruction mechanism provided by the experiment and those provided by the product manual. Eventually, this study presents all the necessary fundamental data to provide the construction design with accurate number of reinforcing steel, diameter of the steel, fixation length of the steel, etc. to build the optimum precast concrete column.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.8 s.338
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• pp.27-34
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• 2005

In this paper, FPGA It/w and S/W Embedded system for LDM remote control is implemented. XScale CPU is used on developed system and in communcation ethenet and serial is used. CPU interface with H/W LDM rotation and to drive LDM FPGA logic is implemented, to transmit LDM data from long distance command packet is composed, for S/W Embedded linux is used to design linux device driver and linux application program. This S/W is run by module so by loading this module to linu)( file system it can do any movement. Also by compiling Embedded linux to the system it can lower the price of the system. By using this H/W and S/W theory it can be used on any other embedded system.

• The Journal of Advanced Prosthodontics
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• v.10 no.4
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• pp.300-307
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• 2018

PURPOSE. To investigate the fatigue and fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic molar crowns on dental implants and human teeth. MATERIALS AND METHODS. Molar crowns (n=48; n=8/group) were fabricated of a lithium-disilicate-strengthened lithium aluminosilicate glass ceramic (N). Surfaces were polished (P) or glazed (G). Crowns were tested on human teeth (T) and implant-abutment analogues (I) simulating a chairside (C, crown bonded to abutment) or labside (L, screw channel) procedure for implant groups. Polished/glazed lithium disilicate (E) crowns (n=16) served as reference. Combined thermal cycling and mechanical loading (TC: $3000{\times}5^{\circ}C/3000{\times}55^{\circ}C$; ML: $1.2{\time}10^6$ cycles, 50 N) with antagonistic human molars (groups T) and steatite spheres (groups I) was performed under a chewing simulator. TCML crowns were then analyzed for failures (optical microscopy, SEM) and fracture force was determined. Data were statistically analyzed (Kolmogorow-Smirnov, one-way-ANOVA, post-hoc Bonferroni, ${\alpha}=.05$). RESULTS. All crowns survived TCML and showed small traces of wear. In human teeth groups, fracture forces of N crowns varied between $1214{\pm}293N$ (NPT) and $1324{\pm}498N$ (NGT), differing significantly ($P{\leq}.003$) from the polished reference EPT ($2044{\pm}302N$). Fracture forces in implant groups varied between $934{\pm}154N$ (NGI_L) and $1782{\pm}153N$ (NPI_C), providing higher values for the respective chairside crowns. Differences between polishing and glazing were not significant ($P{\geq}.066$) between crowns of identical materials and abutment support. CONCLUSION. Fracture resistance was influenced by the ceramic material, and partly by the tooth or implant situation and the clinical procedure (chairside/labside). Type of surface finish (polishing/glazing) had no significant influence. Clinical survival of the new glass ceramic may be comparable to lithium disilicate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.55-64
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• 1984

Presented is a nonlinear constitutive model for progressive tensile fracturing of concrete. The model is incremental, path-dependent, and tensorialy invariant. The total strain tensor is assumed to be a sum of a purely elastic component and an inelastic component. The material is considered to contain weak planes of all directions which characterize the planes of the microcracks. A one-to-one functional dependence is assumed between the normal stress and the normal strain across each of the weak planes. The tangential stiffness of concrete is then derived form the principle of virtual work. The present theory can be applied to loading histories which are nonproportional or during which the principal directions rotate. Good agreement with the available direct tensile test data which cover strain-softening is demonstrated.