• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6C
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• pp.203-212
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• 2011

This paper investigates the caharactheristics of the earth pressure magnigue and distribution in jointed rockmass for a safe and economic design and construction of earth retaining structures installed in rock stratum. For this purpose, this study will first investigate the limitations and problems of the existing earth pressure studies and then to overcome them th study will conduct the discontinuum numerical parametric studies based on the Discrete Element Method (DEM), which can consider the joint characteristics in rock stratum. The controlled parameters include rock type and joint conditions (joint shear strength and joint angle), and the magnitude and distribution characteristics of earth pressure have been investigated considering the interactions between the ground and the retaining structures. In addition, the comparison between the earth pressures induced in rock stratum and Peck's earth pressure for soil ground has been carried out. From the comparison, it is found that the earth pressure magnitude and distribution in jointed rockmass has been highly affected by rock type and joint condition and has shown different characteristics compared with the Peck's empirical earth pressure. This result would hereafter be utilized as an important information and a useful data for the assessment of earth pressure for designing a retaining structures installed in jointed rockmass.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.7
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• pp.673-677
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• 2016

Recently, engineering applications have started to adopt solutions inspired by nature. The peculiar adhesive properties of gecko skin are an example, as they allow the animal to move freely on vertical walls and even on ceilings. The high adhesive forces between gecko feet and walls are due to the hierarchical microscopical structure of the skin. In this study, the effect of metal coatings on the adhesive strength of synthetic, hierarchically structured, dry adhesives was investigated. Synthetic dry adhesives were fabricated using PDMS micro-molds prepared by photolithography. Metal coatings on synthetic dry adhesives were formed by plasma sputtering. Adhesive strength was measured by pure shear tests. The highest adhesion strengths were found with coatings composed of 4 nm thick layers of Indium, 8 nm thick layers of Zinc and 6 nm thick layers of Gold, respectively.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.557-561
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• 2007

Polypropylene (PP)/corn starch master batch (starch-MB) blends with different PP compositions of 40, 50, 60, and 80 wt% were prepared by melt compounding at $200^{\circ}C$, using lab scale Brabender mixer. The chemical structures and thermal properties of the PP/starch-MB blends were investigated by FT-IR, differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). The chemical structure was confirmed by the existence of hydroxy group. There was no district change in melting temperature and melting enthalpy, and TGA curve indicated a decrease in degradation temperature with starch-MB content. The porosity change of blend was measured by scanning electron microscope (SEM), the degree of porosity on the blend surface increased with the starch-MB content. The rheological properties indicated an increase in complex viscosity, shear thinning tendency and elasticity with the starch-MB concentration. These effects were confirmed by an oscillatory viscometer at $200^{\circ}C$. From these results, it is found that 40 wt% is the optimum starch-MB concentration. The fiber was fabricated from PP60/MB40 with 40 wt% starch-MB and the porosity and tensile properties were investigated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.87-98
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• 2011

Clay bricks with lime mortar are recently popular since they are eco- and environment-friendly construction material being capable of air flow and moisture movement. However, there is little study on those of clay brick an lime mortar while relatively many researches on the structural characteristics of concrete bricks with cement mortar are available in Korea. Furthermore, the current Korean Building Code of masonry structures was established on the base of the Foreign Codes which does not reflect Korean masonry construction circumstance, such as material characteristics and section properties. To overcome these problems, experiments of masonry structures constructed using clay bricks with lime mortar were carried out to evaluate their structural characteristics such as, prism compressive strength, adhesive strength and diagonal tensile(shear) strength. Also this research compares the mechanical characteristics between clay bricks with lime mortar and concrete bricks with cement mortar to provide information that will be used for revisions of the domestic standards for masonry structures. As masonry structures constructed with clay bricks and lime mortar show different aspects over the ones constructed with concrete bricks and cement mortar, we suggest estimation equation of prism compressive strength and diagonal tensile strength on masonry structures constructed with clay bricks and lime mortar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.54-63
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• 2014

Corrugated steel plate structure, which is built by assembling corrugated steel plate segments with bolts on site and filling the surroundings with quality soil, is widely used for buried structures as a eco-corridors, small bridges, and closed conduits. This experimental study is dealt with the static and fatigue performance of bolt connected corrugated steel plates under flexural loading. The experimental variables to verify the fatigue performance are bolt diameters and detailing of connection such as washer and the corrugation dimension of specimens has a $400{\times}150$ mm. The experimental ultimate strength of specimens under static loading was higher than the theoretical strength and all specimen failed by a bearing and tearing failure of bolt hole of upper plate. Therefore, a fatigue tests of specimens had 6.0mm and 7.0mm thickness was conducted in which the load range was up to 209kN and 516kN, respectively. From the fatigue test, failure patterns are changed from plate bearing and tearing which is a typical failure pattern of static failure to a bearing failure of plate and shear failure of bolt, and experimental fatigue limit at $2{\times}10^6$cycles is about 85MPa.

• Economic and Environmental Geology
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• v.50 no.6
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• pp.525-535
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• 2017

Exhumation mechanism of migmatite in orogenic belts provides insights into thermo-mechanical evolution of lithosphere in association with orogeny. This study deals with kinematics of structures in and around the Gwangcheon Gneiss, as a preliminary study on exhumation mechanism, which is a main constituent of a domal structure (viz., Oseosan Dome) in the Hongseong area, southwestern margin of the Gyeonggi massif. Geological structures in the Gwangcheon Gneiss, which mainly comprises southern and northwestern part of the Oseosan Dome, generally have kinematic component of top-outward shear. This feature is likely to represent diapiric dome-up movement. In addition, a high strain zone, by which the tectonic domain involving the Gwangcheon Gneiss is bounded on the west, show structural features with normal sense of shear component. Taking available (thermo)chronological data into account, it is interpreted that activation of the high strain zone and exhumation of the Gwangcheon Gneiss occurred during Late Triassic, when the Gyeonggi massif was widely affected by post-collisional processes. It means that the Gwangcheon Gneiss was diapirically moved up and exhumed in the footwall of extensional high strain zone in association with Triassic post-collisional processes.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.121-131
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• 2006

This study is performed to examine the ground reinforcement effect and the environmental impact of LW injection, which is widely used during the excavation of high-rise apartment buildings. In addition, it proved that by conducting field exploration and laboratory test the engineering ground reinforcement effect of LW injection in the ground has low coefficient of permeability. The environmentally friendly aspect was evaluated through an assessment of environmental impact. The results of laboratory test shows that LW coagulating material with SC type soil structure has significant improvement of uniaxial compressive strength, increasing by three times and the shear strength increasing by twice, coefficient of permeability decreasing six to seven times. And the result of environmental impact tests show that from 6 hour after where the pH increases until 7.96 to initially it diminished, it started and to 80 hour after it recovered a pH 7.25 initially with 7.30. The chemical composition analysis test result that unpolluted water and polluted water hydrogen ion concentration (pH) show that the unpolluted water pH 7.36, polluted water pH 7.85, which is inside the Ministry of Environment standard of drinking water (the pH 5.8~8.5). The assessment of environmental impact and chemical analysis test also demonstrate that the LW coagulating material is environmentally friendly. In the $Cr^{6+}$ and the salinity detection test, it was proven that the salinity is slight and the $Cr^{6+}$ is not detected.

• Journal of Adhesion and Interface
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• v.16 no.1
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• pp.29-34
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• 2015

Hydrocarbon resins, which are defined as low molecular weight, amorphous, and thermoplastic polymers, are widely used as tackifier for various types of adhesives, as processing aids in rubber compounds, and as modifiers for plastics polymers such as isotactic polypropylene. Typically, hydrocarbon resins are non-polar, and thus highly compatible with non-polar rubbers and polymer. However, they are poorly compatible with polar system, such as acrylic copolymer, polyurethanes, and polyamides. Moreover, recently the raw materials of hydrocarbon resin from naphtha cracking had been decreased because of light feed cracking such as gas cracking. To overcome this problem, in this study, novel hydrocarbon resins were designed to have a highly polar chemical structure which material is sustainable. And, it was successfully synthesized by Diels-Alder reaction of dicyclopentadiene monomer and sorbic acid from blueberry as renewable resources. Acrylic resins were formulated with various tackifiers solution including sorbic acid grafted hydrogenated dicyclopentadiene hydrocarbon resins in acrylic adhesive and rolling ball tack, loop tack, $180^{\circ}$ peel adhesion strength, and shear adhesion strength were measured. The properties depend on the softening point and polar content of tackifiers.

• Geophysics and Geophysical Exploration
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• v.22 no.4
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• pp.210-224
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• 2019

Surface wave (SW) surveys, which have been applied to numerous application fields ranging from micro-scale ultrasonic analysis to geological scale analysis, are widely used to monitor near-surface stability. The survey method is basically made through analysis on dispersion of SW propagating along the earth surface, in order to delineate shear velocity structure of subsurface. SW survey data are inverted with assuming one-dimensional (1D) layered-earth in order to recover shear wave velocities of each layer, after being analyzed to make the dispersion curve that shows phase velocity of SW with respect to frequency. This study reviews surface wave surveys with explaining the basic theory including the characteristics of dispersion and the procedure of general data processing. Even though surface wave surveys can be categorized into active and passive methods, this paper focuses only on active surface wave methods which includes continuous SW (CSW), spectral analysis of SW (SASW) and multichannel analysis of SW (MASW). Passive method will be reviewed in the subsequent paper.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.55-62
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• 2001

With a spread of BGA, CSP and fine pitch devices, the need of flatter surface finish in bare board is becoming more critical in solderability. The electroless Ni/Au plating has a solution of these needs and also has being spread to apply to surface finish for bare board in many electronic goods. But, the electroless Ni/Au plating had several issues such as Ni oxidation and phosphorous contents. Before this study, we studied on the effect of BGA solderability in electroless Ni/Au plating and chose some major factors such as the oxidation property of NiP plating and warpage of board. Firstly, we made test board with various plating conditions and improved the plating property through the improvement of NiP oxidation reducing P content. Also, we minimized the warpage of board with the improvement of inner layer structure and the analysis of warpage. For the evaluation of solderability, we analyzed the warpage of board and the plating property after mounting BGA on the board with optimizing conditions. The solder joint of BGA is investigated by SEM(Scanning Electronic Microscope) and OM(Optical Microscope). The composition of joint is used by EDS(Energy Dispersive Spectroscopy). We analyzed the fracture strength and mode by ball shear teser.