• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.9-18
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• 2019

Modular system can be divided into two types based on the methods of resisting load. The one is the open-sided modular system composed of beams and columns. The other is the enclosed modular system composed of panels and studs. Of the Modular systems, the use of open-sided modular system is limited because it consists of closed member sections. In order to solve this problem, Choi et al.(2017) proposed a composite modular system with folded steel members filled with concrete. However, it was assumed in the previous study that the connections between modules are composed of rigid joint. Therefore it didn't identify the effect of connection behavior in structure. This study used finite element analysis to calculate stiffness of the connections in the proposed modular system. The linearization method presented in FEMA 440 is used for seismic performance assessment of structures, considering the connection stiffness computed in this study. The result of analysis shows that the capacity and story drift ratio obtained in the model considering stiffness of connection are less than those in the model not considering connection stiffness. Based on this observation, it is concluded that the stiffness of connection has a considerable effect on structural behavior.

• Journal of the Korean Society of Food Culture
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• v.22 no.4
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• pp.492-497
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• 2007

The objectives of this study are to determine the full extent of the negative media reports and to broaden public awareness through content analysis. Samples of this study are news reports on vibrio on three major broadcasting companies such as MBC, KBS and SBS and three major national newspapers such as Chosun daily, Joongang daily and Donga daily in Korea for 5 years from January 1st in 2000 to December 31st in 2004. Total 628 cases were searched through from the web sites of fore mentioned TV and newspaper companies. It is highly advised to adhere to the proven fact as much as possible and full and thorough research on the outcome should be sought by media before they reach to the public.

• Korean Journal of Heritage: History & Science
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• v.38
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• pp.329-358
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• 2005

The Three storied Stone pagoda in Gameunsa Temple site, one of the early staged stone pagodas, has been known as a standard for Silla stone pagodas. A stone pagoda is not only a stone art work and but also a stone structure. Most studies and investigation of the stone pagoda has done mainly based on style and chronological research according to an art historical view. However, there is not an attempt to research the stone pagoda as a stone architecture. Most Korean experts at the stone pagoda has art history in their background. Engineers who can understand the structure of the stone pagoda are very limited. More architectural and engineering approach is need to research not only art historial understanding but also safety as a structure. We can find many technical know-how from our ancestors who made stone pagodas. 1. To reduce any deformation such as relaxation and sinking of BuJae which is caused by a heavy load, the BuJae (consist of a foundation stone and lower stereobates) should be enlarged. 2. A special construction method for connection between Myonsuk and Tangjoo was invented. This unique method is not used any longer after the Three storied Stone pagoda in Gameunsa Temple site. 3. The upper BuJae and the lower BuJae are missed each other by making a difference of Okgaesuk and Okgaebatchim in size. It is done for a distribution of perpendicular load and a prevention for relaxation of BuJae. 4. The center of gravity in the BuJae is located to the center of the stone pagoda by trimming the upper surface of the Okgaebatchim into a convex shape. The man who made stone pagodas had excellent knowledge on the engineering and techniques to understand the structure of the stone pagodas. We can confirm it as follows: the enlarged BuJae, dislocated connection between upper Bujae and lower BuJae, and moving the center of gravity close to the center of the stone pagoda.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.511-519
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• 2008

Statement of problem: An incompatibility between the initiator systems of self-curing composite resins and light-curing adhesives was supposed recently. Purpose: The purpose of the study was to evaluate the influence of activators for self/dual bonding on dentin shear bonding strengths. Material and methods: Fifty human molars were divided into 5 groups. A flat dentin surface was created for each tooth. A self-curing composite resin (Luxacore) was bonded with the following adhesives (n = 10); One-Step, Prime&Bond NT, AdheSE, Prime&Bond NT and AdheSE were also used in combination with activators. Shear bond strengths were measured after 24 hours of water storage. The specimens were loaded in shear in the Instron until failure at a 1 mm/min crosshead speed. Data were compared using one-way ANOVA and Tukey HSD test (${\alpha}$= 0.05). Results: The dentin adhesive systems in order of decreasing median bond strength were One-Step > Prime&Bond NT with activator, AdheSE with activator > Prime&Bond NT, AdheSE. Among adhesives, One-Step had the highest bond strength. Prime&Bond NT with activator had higher bond strengths than Prime&Bond NT that was used alone, and so was AdheSE. Conclusion: Shear bond strengths were increased in Prime&Bond NT and AdheSE when these were used with activators comparing used without activators. But using activators was not effective clinically comparing One-Step.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.3
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• pp.231-242
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• 2008

Purpose: The purpose of this study was to investigate the bond strength of the core-veneer interface in all ceramic systems. Material and Methods: The all ceramic systems tested with their respective veneer were IPS Empress 2 with IPS Eris, IPS e.max Press with IPS e.max Ceram and IPS-e.max ZirCAD with IPS e.max Ceram. Cores (N=36, N=12/group, diameter: 10mm, thickness: 3mm) were fabricated according to the manufacturer's instruction and cleaned with ultrasonic cleaner. The veneer(diameter: 3mm, thickness: 2mm) were condensed in stainless steel mold and fired on to the core materials. After firing, they were again ultrasonically cleaned and embedded in acrylic resin. The specimens were stored in distilled water at $37^{\circ}C$ for 1 week. The specimens were placed in a mounting jig and subjected to shear force in a universal testing machine(Z020, Zwick, Germany). Load was applied at close to the core-veneer interface as possible with crosshead speed of 1.00mm/min until failure. Average shear bond strengths(MPa) were analyzed with a one-way analysis of variance and the Tukey test(${\alpha}=.05$). The failed specimens were examinated by scanning electron microscopy(JSM-6360, JEOL, Japan). The pattern of failure was classified as cohesive in core, cohesive in veneer, mixed or adhesive. Results: The mean shear bond strength($MPa{\pm}SD$) were IPS e.max Press $32.85{\pm}6.75MPa$, IPS Empress 2 $29.30{\pm}6.51MPa$, IPS e.max ZirCAD $28.10{\pm}4.28MPa$. IPS Empress 2, IPS e.max Press, IPS e.max ZirCAD were not significantly different from each others. Scanning electron microscopy examination revealed that adhesive failure did not occur in any all ceramic systems. IPS Empress 2 and IPS e.max Press exhibited cohesive failure in both the core and the veneer. IPS e.max ZirCAD exhibited cohesive failure in veneer and mixed failure.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.207-220
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• 1999

Model tests were performed to investigate the failure modes in embankments on soft ground supported by piles with cap beams. In the model tests, Jumunjin standard sand was placed on simulated cap beams and soft ground. The cap beams are placed perpendicular to the longitudinal axis of the embankment. The colored sand and the Jmniin standard sand were placed one after the other above cap beams and soft ground to make lateral stripes with 3mm thickness in the embarkment. The colored sand was prepared by coating the Jumunjin sand with black lead powder. The photographs illustrate the two characteristic modes of failure in embarkments. One is the soil arching failure and the other is the punching shear failure. The failure mode depends on the height of embankment and the space between cap beams. That is, if the embankment is high enough compared with the space between cap beams, it will fail in arching failure. On the other hand if the embarkment is relatively low or the space between piles is too wide, it will fail in punching shear failure. The soil arching develops in embarkment as a semicylindrical arch with a thickness equal to the width of the cap beam. And the soil wedge developed above the cap beams remains intact during both arching and punching failures. The boundary of punching shear failure of the displaced soil mass can be defined on the basis of observation of the photographs.

• Journal of Sericultural and Entomological Science
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• v.47 no.1
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• pp.41-47
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• 2005

Kayagum is a traditional musical instrument in Korea. Kayagum strings are usually made of raw silk. It needs good vibration and durability. This study was carried out to increase durability of the strings by chemical treatment and manufacture of silk/polyester and silk/wild silk compound yarn. In this study, we used MKW-810(water solube acrylic adhesive)and polyvinyl alcohol as a adhesive. Before the twisting, the raw silk wet on the string manufacture process. The adhesive reagent were added in this process. And compound yarn were prepated by domestic silk, polyester and wild silk(antheraea pernyi) for make of Kayagum strings, respectively. The result are as follows. 1. Tenacity and elongation of the strings are almost same between none and chemical treatment. However number of extension cycling to breaks of the strings was largely increased by chemical treatment. Number of extension cycling to breaks of the strings is very important and useful item to check durability of the strings. The stiffness of the strings were almost same between none and adhesive treatment 2. Tenacity of the silk/polyester strings is largely decreased by increasing of polyester portion, but elongation of the silk/polyester strings increased. However tenacity of the silk/polyester(mono filament) strings are higher than that of silk strings. 3. Tenacity of the domestic silk/wild silk strings is largely decreased by increasing of wild silk portion, but elongation of the domestic silk/wild silk strings is almost same among silk and domestic silk/wild silk strings.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.4
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• pp.393-400
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• 2012

In recent years, nano-structured thin film systems are often applied in industries such as MEMS/NEMS device, optical coating, semiconductor or like this. Thin films are used for many and varied purpose to provide resistance to abrasion, erosion, corrosion, or high temperature oxidation and also to provide special magnetic or dielectric properties. Quite a number of articles to evaluate the characterization of thin film structure such as film density, film grain size, film elastic properties, and film/substrate interface condition were reported. Among them, the evaluation of film adhesive to substrate has been of great interest. In this study, we fabricated the polymeric thin film system with different adhesive conditions to evaluate the adhesive condition of the thin film. The nano-structured thin film system was fabricated by spin coating method. And then V(z) curve technique was applied to evaluate adhesive condition of the interface by measuring the surface acoustic wave(SAW) velocity by scanning acoustic microscope(SAM). Furthermore, a nano-scratch technique was applied to the systems to obtain correlations between the velocity of the SAW propagating within the system including the interface and the shear adhesive force. The results show a good correlation between the SAW velocities measured by acoustic spectroscope and the critical load measured by the nano-scratch test. Consequently, V(z) curve method showed potentials for characterizing the adhesive conditions at the interface by acoustic microscope.

• Journal of the Korean Geotechnical Society
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• v.28 no.8
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• pp.21-29
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• 2012

At-rest lateral stress coefficient that is used for the evaluation of geotechnical structures such as foundations and retaining walls plays a significant role in the analysis and design, as a state variable of in-situ stress condition. In the widely applied Jaky's Ko equation stress condition can be inferred from the internal friction angle obtainable from the laboratory experimentation whereas the eguation mares it challenging to evaluate the influences and criteria of particle characteristics which is essential for the application of friction angles in practices. Thus, this study experimentally explored the behaviors of Ko depending on the relative density, particle shape, and surface roughness effect during a range of loading stages. The Ko values of Jumumjin sand, glass beads, and etched glass beads were measured using a customized Ko device housing strain gauges during loading-unloading-reloading steps, and the effect of dominant factors on Ko is analyzed. Results show that the high Ko prevails for both round and angular specimens with low relative density and the surface roughness has a nominal effect. The angular particles exhibit low Ko for specimens with similar relative density. The characteristics of relevance between Ko and friction angles with varying relative density are also investigated based on the experimental results using empirical correlations and previously reported values.

• Journal of the Korean GEO-environmental Society
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• v.14 no.1
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• pp.5-13
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• 2013

Soils around a pile are highly constrained when the vertical load is applied to the pile. However, the conventional direct shear test cannot evaluate the shear strength of the soils under the normal confinement condition. The goal of this study is to evaluate the shear behaviors according to the normal displacement confinement condition including free normal displacement (FND) and constrained normal displacement (CND) during direct shearing. Jumunjin sands were prepared at the different relative densities and loaded at the different normal stresses. The specimens were sheared according to the normal confinement conditions. Experimental results show that shear strengths obtained by the CND tests are higher than those obtained by the FND tests. In addition, for the constrained normal displacement condition, the increment of shear strength increases with the increase of relative density, while the increment of shear strength decreases with the initial normal stress. This study suggests that the effect of confinement condition on the shear strength should be considered when the stability of constrained soils is analyzed.