• Tunnel and Underground Space
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• v.14 no.2
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• pp.86-96
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• 2004

Rock mass classification methods such as RMR, Q system and GSl have been widely adopted with certain modifications for the design of mine openings. The GSI system is the only rock mass classification system that is related to Mohr-Coulomb and Hoek-Brown strength parameters and gives a simple method to calculate the engineering properties of rock masses which can be useful input parameters for a numerical analysis. A detailed surveying for GSI mapping as well as far calculating RMR values was undertaken at Daesung and Pyunghae underground limestone mining sites. RQD values were determined for row locations in these two mining sites. Based on GSI values and intact rock strength properties, the rock mass strength modulus of elasticity as well as the Mohr-Coulomb strength parameter c$_{m}$ and $\phi$$_{m}$ were determined. GSI and RMR are correlated.

• Journal of the Korean Wood Science and Technology
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• v.30 no.1
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• pp.18-24
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• 2002

Small Sitka spruce specimens of 50×133×10 mm³ were artificially weathered in a chamber equipped with 340 mm xenon arc and water spray as part of the accelerated-weathering cycle. Specimens were exposed to only ultraviolet or ultraviolet with water spray for 10 and 20 hours. Physical properties of the weathered specimens were investigated by colorimetry, sorption and ultrasonic testing methods. The longer exposed to ultraviolet the less bright were the specimens. It was revealed that the water spray treatment accelerated the loss of brightness and increased the wettability. Among the specimens exposed to ultraviolet with water spray the specimens treated for 10 hours showed greater wettability than those for 20 hours, which might lose the wettability due to the excessive degradation on their surfaces. The ultrasonic velocities of the weathered specimens were obviously higher than those of the unweathered. It is considered that the accelerated weathering either increases the modulus of elasticity of wood or decrease the density of wood.

• Journal of the Korean Geotechnical Society
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• v.28 no.12
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• pp.53-64
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• 2012

In this study, the modified cyclic triaxial tests with Joomunjin standard sand are performed for dynamic deformation characteristics, such as Young's moduli and damping ratio. The cyclic triaxial test is equipped with Local Displacement Transducer (LDT) on the outside of a cell which has a range from $10^{-4}$ to $10^{-1}$ of shear strains, ${\gamma}$ (%), instead of conventional cyclic triaxial test which has linear variable displacement transducer (LVDT) with low precision. With the small strain control, tests were carried out at various loading rates, void ratios, and effective confining pressures. Based on the test results, such as dynamic deformation characteristics, shear modulus, and damping ratio, it is found that the test can measure more range of medium strains (0.02-0.2%) than results obtained from conventional test (resonant column test). For the medium strain range, dynamic deformation characteristics investigated by the cyclic triaxial test are also different from those predicted by nonlinear model in conventional test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.559-568
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• 2019

Recently, the infrastructure of the marine environment has been increasing. Therefore, there has been increasing interest in increasing the durability of structures. The FRP Hybrid Bar with improved durability against corrosion was developed in recent years. On the other hand, studies that evaluate the corrosion resistance are insufficient. In this study, the corrosion resistance according to the type of rebar in concrete was assessed and analyzed. The experiment used steel bars and FRP Hybrid Bar. The corrosion test method was a galvanic current and half-cell potential method. The accelerated corrosion test was carried out by four levels (0%, 1.5%, 3%, and 6%) of chloride added to the concrete. The galvanic current measurements revealed no corrosion current in the FRP Hybrid Bar. The half-cell measurement also showed the corrosion resistance of the FRP Hybrid Bar. Therefore. FHB can be used as an alternative steel for structures where a marine environment and steel corrosion are predicted.

• Korean Journal of Optics and Photonics
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• v.23 no.1
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• pp.12-16
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• 2012

In the paper, we fabricated a Ni master with $45^{\circ}$-mirror structures for flexible waveguide fabrication. The flexible waveguide films with embedded $45^{\circ}$-angled mirrors at the waveguide ends were successfully fabricated using a UV-imprint process. Next, in order to enhance the reflectivity of the mirrors, Ni(3 nm)-Au(200 nm) bilayers were evaporated on the $45^{\circ}$-angled facets through a locally opened thin mask using an electron beam evaporator. We measured propagation loss, bending loss, mirror loss and bending reliability of the fabricated waveguide.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.15-31
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• 2012

In our previous studies, the antioxidant, anti-aging, and antibacterial activities of Persicaria hydropipier L. extract, and the moisturizing effect of cream containing P. hydropipier extract were investigated. In this study, the cellular protective effects of P. hydropipier extract and isoquercitrin, main component from P. hydropipier in $^1O_2$-induced photohemolysis of human erythrocytes and ultraviolet B (UVB)-exposed HaCaT cells were investigated. Liposomes such as ethosome and elastic liposome for enhanced transdermal delivery were prepared. Size, loading efficiency, stability, and cumulative permeated amounts of ethosomes and elastic liposomes were evaluated. P. hydropipier extract and isoquercitrin showed more prominent cellular protective effect than (+)-${\alpha}$-tocopherol, known as lipid antioxidant at $5{\mu}g/mL$. P. hydropipier extract didn't show any characteristics of cytotoxicity at $50{\mu}g/mL$. When HaCaT cells were exposed to a single large dose ($400mJ/cm^2$) of UVB, the extract protected the cells against UVB radiation in a concentration dependent manner ($12.5{\sim}50{\mu}g/mL$). Cell viability of HaCaT cells exposed to UVB $400mJ/cm^2$ was increased by treatment with P. hydropipier extract or isoquercitrin from 36 % (cell viability of positve control groups) to 90 % (cell viability of P. hydropipier extract or isoquercitrin- treated groups). The size of 0.04 % P. hydropiper extract loaded ethosomes was 173.0 nm and the loading efficiency was 55.58 %. 0.04 % P. hydropiper extract loaded ethosomes were stable with as monodisperse particles for 1 week. The ethosome exhibited more skin permeability than general liposome and ethanol solution. The optimal ratio of lipid to surfactant ($Tego^{(R)}$ care 450) of 0.1 % P. hydropiper extract loaded elastic liposomes was observed to be 95 : 5. Vesicle size of 0.1 % P. hydropiper extract loaded elastic liposome was 176.5 nm. The deformability index of the elastic liposome was 16.4. The loading efficiency was 68.8 %. The elastic liposome containing P. hydropiper extract showed more skin permeability than liposome without surfactant ($Tego^{(R)}$ care 450).

• Korean Journal of Crystallography
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• v.5 no.2
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• pp.51-66
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• 1994

Y3Al5O2 and Nd: Y3Al5012 single crystals were grown by Czochralskl technique. The effectt of pulling rate rotation rate, and doping level of Nd3+ ion on the crystal quality were studied Various types of defects were analysed by photo-elastic effect and chemical etching method Finally, spectroscopic and laser poputies of grown crystal were measured. Optirmum pulling rate for good quality was dependant on the doping level of Nd3+ ion. It was found that the suitable pulling rates for pure Y3Al5O12 for 3.0∼3.5 a/o Nd3+ ion doped Y3Al5012 and for more than 40 a/o Nd3+ ion doped Y3Al5012 were 2∼4mm/hr, 0.6∼0.5mm/hr, and less than 0.4mm/hr respectively. Solid-liquid interface was convex at the rotation rate of 27∼60rpm, and concave at the rotation rate of 80∼100rpm. Growth axis was confired to <111> direction and lattice parameter was measured to 12.017A. Core (211) facets,striations, inclusions of metal particles, dislocations and optical inhonngeneities were detected. Four level laser transition of Nd3+ion in YIAls012 single crystal were identified by the spectroscopic measurements. Laser rod with tam diameter and 63mm length was fabricated from grown Nd3+ Y3Al5012 sin91e crystals. 1.8lJ of lasing threshould and 0.49% of soope efficiency were measured by the Pulsed laser action.

• Korean Journal of Optics and Photonics
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• v.24 no.4
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• pp.184-188
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• 2013

Two types of polymer-based optical splitters with $200{\mu}m$ large core are presented for optical multimode networks, such as smart home networks, intelligent automotive networks, etc. Optical splitters that have 1:1 symmetric and 9:1 asymmetric structure were fabricated by a ultra violet(UV)-imprint technology using a deep etched Si(silicon) master by the Bosch process. In this paper, we successfully fabricated the symmetric and asymmetric optical splitters with suitable optical network applications.

• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.33-41
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• 2011

To substitute TLS in the hybrid system which is combined with Sagnac interferometer and fiber bragg grating (FBG) it is necessary to investigate how the laser source (TLS and CW) and sensor material variate the response of fiber optic sensor. Two different hollow cylinder type mandrel materials are proposed which are PTFE and PTFE+carbon and 18 m optical fiber is wounded at the mandrel surface. CW laser source experiments had been done in the oil tank which is filled with transformer oil in the 1 kHz~20 kHz frequency range. Also Sagnac interferometer fiber optic sensor is combined with FBG called hybrid system and TLS used as a light source. Based on the experimental results PTFE sensor showed more higher magnitude of detection signal rather than carbon sensor and this result is agreement with the McMahon's theoretical results. Phase variation is inversely proportional to the elastic modulus of the mandrel material. In PTFE fiber sensor, tunable laser source showed more higher performance rather than CW case. Therefore, TLS fiber optic sensor can be applied to the hybrid system which is combined with Sagnac and FBG.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.35 no.1
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• pp.19-25
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• 2009

It has been reported that not only collagen but also elastin contribute to inhibit skin wrinkle formation. Ultraviolet (UV) radiation induces photo-aging on human skin. Because UV radiation increases elastase activity, it is thought that increased elastase activity could be the major reason for skin elasticity reduction and wrinkle formation by UV. In the present study to standardize elastase activity measuring system, purified elastases from porcine pancrease and human neutrophil, and cell extracts of normal human primary fibroblasts, 3T3 mouse fibroblasts, and CCD-25Sk human fibroblasts were used as various enzyme sources. Furthermore, elastase activities were compared according to concentrations of enzyme and substrate and incubation time. Phosphoramidon was used as a positive control to inhibit elastase activities of normal human primary fibroblasts and CCD-25Sk fibroblasts. However, it had no influence on the activity of porcine pancreatic elastase. Therefore, it is suggested that elastase used for testing anti-wrinkle agents should be selected carefully.