• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.61-69
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• 2009

Statement of problem: Porcelain veneers have become a popular treatment modality for aesthetic anterior prosthesis. Fitting porcelain veneers in the mouth usually involve a try-in appointment, which frequently results in salivary contamination of fitting surfaces. Purpose: An in vitro study was carried out to investigate the effect of silane treatment timing and saliva contamination on the resin bond strength to porcelain veneer surface. Material and methods: Cylindrical test specimens (n=360) and rectangular test specimens (n=5) were prepared for shear bond test and contact angle analysis. Whole cylindrical specimens divided into 20 groups, each of which received a different surface treatment and/or storage condition. The composite resin cement stubs were light-polymerized onto porcelain adherends. The shear bond strengths of cemented stubs were measured after dry storage and thermocycling (3,000 cycles) between 5 and $55^{\circ}C$. The silane and their reactions were chemically monitored by using Fourier Transform Infrared Spectroscopy analysis (FTIR) and contact angle analysis. One-way analysis of variance (ANOVA) and Dunnett's multiple comparison were used to analyze the data. Results: FT-IR analysis showed that salivary contamination and silane treatment timing did not affect the surface interactions of silane. Observed water contact angles were lower on the saliva contaminated porcelain surface and the addition of 37% phosphoric acid for 20 seconds on saliva contaminated porcelain increased the degree of contact angle. Silane applied to the porcelain, a few days before cementation, resulted in increasing the bond strength after thermocycling. Conclusion: Within the limitation of this study, it can be concluded that it would be better to protect porcelain prosthesis before saliva contamination with silane treatment and to clean the contaminated surface by use of phosphoric acid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.448-454
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• 2020

This study aims to determine the cause of structural defects occurring during aircraft operations and to verify the structural integrity of the improved features. The fracture plane was analyzed to verify the characteristics of the cracks and the fatigue failure leading to the final fracture was determined by the progress of the cracks by the repeated load. During aircraft operations, the comparative analysis of the load measurement data at the cracks with the aircraft design load determined that the measured load was not at the level of 30% of the design to be capable of being damaged. A gap analysis resulted in a significant stress of approximately 32 ksi at the crack site. Pre-Load testing also confirmed that the M.S. was reduced by more than 50% from +0.71 to +0.43, resulting in a sharp increase in aircraft load and the possibility of cracking when combined. Thus, structural reinforcement and the removal of the gap for aircraft cracking sites improved the defect. Based on the structural strength analysis of the improvement features, the bulkhead has a margin of about +0.88 and the fitting feature is about +0.48 versus allowable stress. In addition, the life analysis results revealed an improvement of approximately 84000 hours.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.305-314
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• 2018

The steel-plate concrete composite beam is composed of a steel plate, concrete and a shear connector to combine the two inhomogeneous materials. In general, the steel plate is assembled by welding an existing composite beam. In this study, a new steel-plate concrete composite (SPCC) beam was developed to reduce the size of the shear connector and improve its workability. The SPCC beam was composed of folded steel plates and concrete, without any shear connector. The folded steel plate was assembled with high strength bolts instead of welding. To improve the workability in field construction, a hat-shaped cap was attached in the junction with the slab. Monotonic two-point load testing was conducted under displacement control mode. The flexural strength of the SPCC beam specimen was calculated to be 76% of that of the complete composite beam by using the plastic stress distribution method and strain compatibility method. The cap acted as the stud and accessory. The synthesis rate could be increased by controlling the gap of the cap, and the bending performance could be evaluated by using the strain fitting method considering the synthesis rate of the SPCC beam.

• Journal of the Korean Society of Tobacco Science
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• v.27 no.1 s.53
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• pp.141-152
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• 2005

This study focused on the relationships among leaf and smoke components and sensory properties following tobacco leaf blending. A completely randomized experimental design was used to evaluate components of leaf and smoke and sensory properties for sample cigarettes with four mixtures of flue cured and burley tobacco (40:60, 60:40, 80:20 and 100:0). Eleven leaf components, six smoke components, and eight sensory properties of smoking taste were analyzed. A sensory evaluation method known as quantitative descriptive analysis was used to evaluate perceptual strength on a fifteen score scale. Raw data from ten trained panelists were obtained and statistically analyzed. Based on the MANOVA, clustering analysis, correlation matrix and partial least square (PLS) method were applied to find out which smoke component most affected sensory properties. The PLS method was used to remove the influence between explanatory variables in the leaf, smoke components derived from the results. High correlations (p<0.0l) were found among ten specific leaf and smoke components and sensory attributes. Total nitrogen, ammonia, total volatile base, and nitrate in the leaf were significantly correlated (p<0.05) with impact, bitterness, tobacco taste, irritation, smoke volume, and smoke pungency. From the results of PLS analysis, influence variables are used to explain about the correlation. In terms of bitterness, with only two explanatory variables, Leaf $NO_3$ and Leaf crude fiber were enough for guessing their correlation. In the distance weighted least square fitting analysis, carbon monoxide highly influenced bitterness, hay like taste, and smoke volume.

• Tunnel and Underground Space
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• v.19 no.6
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• pp.473-478
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• 2009

The accuracy of point load apparatus is depend on point to point coaxial fitting. Also, the estimation of applied point load using the pressure gauge frequently lead to erroneous results. An improved point load apparatus has been developed in this study by mounting linear bearing on polished support rod, and eccentric error of point to point axis has been sustained less than 0.1 mm even under series of extreme work load conditions. Two digital displacement gauges are attached to measure the distance from point to point with sample specimen. A load cell mounted at the end of upper conical platen measure the applied net load on sample instead of preassure gauge. Total of 107 point load tests has been achieved to assure the quality and performance of developed apparatus. This exercise turned out to be successful.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.139-144
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• 1982

This study has examined closely on the various foundamental conditions for the fitting in steatite porcelain as a industrial porcelain of superior quality, and as a decorated porcelain. The materials consisting of the Kyul Sung talc, and the sea water magnesia clinker power which was produced from Sam Hwa-Hwa Sung, as major constituents have been used, and also used Hyup Jin kaolin as clay minerals to give them plasticity. First, the mixture was made of corresponding in the theoretical composition of enstatite with Kyul sung talc and sea water magnesia clinker, and kaolin was added in various kinds of 1%, 2.5% 5%, 10%, and 20% by weight of the mixture. Next, the mixture was fired at the various temperatures from 1330 to 145$0^{\circ}C$. After we examined closely the physical properties and microstructures, we achieved the results that noted from this study were listed below. 1. The addition amount of kaolin should generally be from 5% to 10% by weight of the mixture to give mixture plasticity in steatite porcelain, but preferably about 20% to consider the firing temperature. 2. The temperature of the optimum firing range is from 1390 C to 142$0^{\circ}C$. 3. A case, which the $A_2$ composition had been fired at 142$0^{\circ}C$, showed a good effect in the strength, but showed a bad result in the absorption. Therefore, the specimens of $A_4$ the composition has excellent in properties of matters when the composition is fired at 142$0^{\circ}C$. Also, we consider that the specimens of the $A_5$ composition, which is fired at 139$0^{\circ}C$, is suitable for the $MgO-SiO_2$ porcelain bodies with respect to the various properties.

• Journal of the Korean Society of Clothing and Textiles
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• v.32 no.3
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• pp.395-407
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• 2008

As global interest in clothing spreads over the smart clothing which arouses high added-value in the apparel industry, this study is to develop a smart jacket with an electrically-vibrating device maintaining excellent appearance and comfort. The vibrating device has a massage function that could relieve muscle pain near shoulders and neck. The purposes of this research are to develop jacket pattern for men in their thirties considering body shapes and fashion trend, to develop a wearable device that is composed of motor and controller and integrate it into a jacket, and to assess the external appearance and functional satisfaction of the smart jacket through the wearing test. The results are as follows: 1. In order to develope an appropriate jacket pattern for men in their thirties, several patterns were assessed for their fitting comfort. The final pattern was completed after making alterations some parts, and showed high satisfaction as 3.6(on a five-point scale) in all categories. 2. A vibrating device was developed by connecting motor, controller, battery and switch. Developing this device, focus was maximizing the strength of motor and minimizing the heat generated from motor and controller. Snaps were placed between inner and outer cloth of jacket so that the vibrating device could be easily attachable and detachable. The motor was located around Trapezius where muscles often get stiff. A switch was designed to be used in selecting the modes of Strong, Weak, and Cross Tapping. 3. The wearing test was conducted to examine outer appearance, comfort for motion, and functionality of the smart jacket. The results of assessing outer appearance showed that the location for attaching the vibrating device was not noticeable but looked natural, and there is almost no change in outer appearance when the vibrating device operates. The result of assessing comfort of action revealed that wearer's satisfaction was high in all categories about activity, wearer's comfort, etc. The result also showed that wear's satisfaction for effects of vibrating massage, easiness in using the device, heat generation was not less than 3.5 in all categories except a category about noise.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.4
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• pp.457-465
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• 2010

In this study, a Taylor series (T-S) model based on the Arrhenius, McVetty, and Monkman-Grant equations was developed using a mathematical analysis. In order to reduce fitting errors, the McVetty equation was transformed by considering the first three terms of the Taylor series equation. The model parameters were accurately determined by a statistical technique of maximum likelihood estimation, and this model was applied to the creep data of alloy 617. The T-S model results showed better agreement with the experimental data than other models such as the Eno, exponential, and L-M models. In particular, the T-S model was converted into an isothermal Taylor series (IT-S) model that can predict the creep strength at a given temperature. It was identified that the estimations obtained using the converted ITS model was better than that obtained using the T-S model for predicting the long-term creep life of alloy 617.

• Explosives and Blasting
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• v.38 no.3
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• pp.15-29
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• 2020

In this paper the Hoek-Brown (HB) failure criterion is integrated into the Holmquist-Johnson-Cook (HJC) concrete material model to reflect the inherent characteristics of field rock masses in LS-DYNA blast modeling. This is intended to emphasize the distinctive characteristics of field rock masses that usually have many geological discontinuities. The replacement is made only for the static strength part of the HJC material model by using a statistical curve fitting technique, and its procedure is described in detail. An example is also given to illustrate the use of the obtained HJC material model. Computation is performed for a plane strain model of a single-hole blasting on a field limestone by using the combination of the fluid-structure interaction (FSI) technique and the multi-material arbitrary Lagrangian Eulerian (MMALE) method in LS-DYNA.

• Journal of the Korean GEO-environmental Society
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• v.14 no.5
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• pp.41-47
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• 2013

Well-graded and dense soils have good engineering properties. Unsaturated soil properties such as shear strength, compressibility and permeability are closely related to the soil-water characteristic curve of the soil. Therefore it is important to study the effects of the coefficient of uniformity and the porosity on the soil-water characteristic curve of the sandy soils, which are also related to the grain size distribution and the density of the soil, respectively. In this study soil-water characteristic curves (SWCCs) for six sandy soil specimens were investigated using Tempe pressure cells. The test data were best-fitted to Fredlund and Xing equation. The obtained fitting parameters and the characteristic points of SWCCs were discussed and correlated with the porosity and the coefficient of uniformity of the specimens. The results show that the smaller the porosity of the specimen becomes, the larger the value of the residual matric suction becomes, whereas the larger the coefficient of uniformity of the specimen becomes, the larger the value of the residual matric suction becomes. Regardless of the coefficient of uniformity, the smaller the porosity of the specimen, the flatter the max. slope of SWCC.