• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.7-17
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• 2024

Vibrations were measured at the surface of a GTX-A site to assess the impact of blasting on underground tunneling. A numerical analysis was conducted using the same ground and blast conditions as those at the site, accompanied by a comparative analysis of other GTX-A sites. This analysis determined the maximum vibration velocity at regular intervals directly above the blasting point at each site. The results were compared with domestic and international vibration standards to establish the vibration measurement range. The specified vibration measurement locations in domestic regulations—"measuring from the closest part of the structure's foundation to the blasting source, and if conditions make it impossible, measuring from the nearest surface to it"—were evaluated. Furthermore, this study underscores the significance of considering the tunnel drilling depth and soil conditions when selecting a vibration measurement location.

• Advances in concrete construction
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• v.16 no.3
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• pp.155-167
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• 2023

The penetrated chloride in concrete has different behavior with mix proportions and local exposure conditions, even in the same environments, so that it is very important to quantify surface chloride contents for durability design. As well known, the surface chloride content which is a key parameter like external loading in structural safety design increases with exposure period. In this study, concrete samples containing OPC (Ordinary Portland Cement), GGBFS (Ground Granulated Blast Furnace Slag), and FA (Fly Ash) had been exposed to submerged, tidal, and splash area for 5 years, then the surface chloride contents changing with exposure period were evaluated. The surface chloride contents were obtained from the chloride profile based on the Fick's 2nd Law, and the regression analysis for them was performed with exponential and square root function. After exposure period of 5 years in submerged and tidal area conditions, the surface chloride content of OPC concrete increased to 6.4 kg/m³ - 7.3 kg/m³, and the surface chloride content of GGBFS concrete was evaluated as 7.3 kg/m³ - 11.5 kg/m³. In the higher replacement ratio of GGBFS, the higher surface chloride contents were evaluated. The surface chloride content in FA concrete showed a range of 6.7 kg/m³ to 9.9 kg/m³, which was the intermediate level of OPC and GGBFS concrete. In the case of splash area, the surface chloride contents in all specimens were from 0.59 kg/m³ to 0.75 kg/m³, which was the lowest of all exposure conditions. Experimental constants available for durability design of chloride ingress were derived through regression analysis over exposure period. In the concrete with GGBFS replacement ratio of 50%, the increase rate of surface chloride contents decreased rapidly as the water to binder ratio increased.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.110-116
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• 2016

The present study numerically investigated the deformation of the interface of two-phase fluids flow in a blast furnace. To simulate three-dimensional(3D) incompressible viscous two-phase flow in the furnace filled with the air and molten iron, the volume of fluid(VOF) method based on the finite volume method has been utilized. In addition, the porous medium with the porosity has been considered as the bed of the particles such as cokes and char etc. For the comparison, the single phase flow and the two-phase flow without the porosity have been simulated. The two-phase flow without porosity condition revealed the smooth parabolic profile of the free surface near the outlet. However, the free surface under the porosity condition formed the viscous finger when the free surface was close to the outlet. This viscous finger accelerated the velocity of the free surface falling and the outflow velocity of the fluids near the outlet.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.832-840
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• 2008

Ablation occurs at irradiance beyond $10^9\;W/cm^2$ with nanosecond and short laser pulses focused onto any materials. Phenomenologically, the surface temperature is instantaneously heated past its vaporization temperature. Before the surface layer is able to vaporize, underlying material will reach its vaporization temperature. Temperature and pressure of the underlying material are raised beyond their critical values, causing the surface to explode. The pressure over the irradiated surface from the recoil of vaporized material can be as high as $10^5\;MPa$. The interaction of high power nanosecond laser with a thin metal in air has been investigated. The nanosecond pulse laser beam in atmosphere generates intensive explosions of the materials. The explosive ejection of materials make the surrounding gas compressed, which form a shock wave that travels at several thousand meters per second. To understand the laser ablation mechanism including the heating and ionization of the metal after lasing, the temporal evolution of shock waves is captured on an ICCD camera through laser flash shadowgraphy. The expansion of shock wave in atmosphere was found to agree with the Sedov's self-similar spherical blast wave solution.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.348-352
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• 1995

Severe gray mold neck rot of onion occurred in most farmers' fields in the southern part of Korea, and 20∼50% of onions were infected by the disease at Goheung, Chonnam, in 1994. Symptoms of the disease appeared on the lower leaves near the soil surface in late February. The symptoms initially appeared as yellowish blotch with compact gray mold on the surface of the infected leaves and developed to blast of the aboveground parts of onions. As brown to dark brown symptoms progressed around the necks of onion later, the bulbs were rotting gradually. Botrytis sp. repeatedly isolated from the lesions produced the typical symptom on the neck of healthy onion 7 days after wound inoculation of conidial suspension of the fungus. The fungus reisolated from the bulbs was identified as Botrytis allii Munn based on the morphological and cultural characteristics and pathogenicity. This is first report of a gray mold neck rot of onion in Korea.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.223-224
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• 2012

금속 표면에 마이크로 나노 구조물을 형성하고 그 위에 발수 특성을 가진 물질을 증착하여, 발수성을 가지는 금속 표면을 개발하였다. Sand blast 공정으로 마이크로 구조 형성, Linear Ion Source(LIS)를 적용한 Ion beam etching으로 나노 구조를 형성하였다. 그 결과 FE-SEM을 통해 수~수십 ${\mu}m$ 크기의 구조 위에 nm 크기의 구조가 형성 된 것을 확인하였다. 발수 특성은 매끈한 표면보다 거친(rough)표면과 낮은 표면에너지로 구현된다. 마이크로 나노 구조가 형성된 Al의 표면에너지를 낮추기 위해 Hexamethyldisiloxane(HMDSO)을 코팅하였다. 접촉각 측정 결과 $105^{\circ}$로 표면 형상을 제어함으로써 발수 특성이 나타나는 것을 확인하였다.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.75-84
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• 2009

STATEMENT OF PROBLEM. A number of studies about the nano-treated surfaces of implants have been conducting along with micro-treated surfaces of implants. PURPOSE. The purpose of this study was to get information for the clinical use of nano-treated surfaces compared with micro-treated surfaces by measuring removal torque and analyzing histological characteristics after the placement of various surface-treated implants on femurs of dogs. MATERIAL AND METHODS. Machined surface implants were used as a control group. 4 nano-treated surface implants and 3 micro-treated surface implants [resorbable blast media surface (RBM), sandblast and acid-etched surface (SAE), anodized RBM surface] were used as experimental groups. Removal torque values of implants were measured respectively and the histological analyses were conducted on both 4weeks and 8weeks after implant surgery. The surfaces of removed implants after measuring removal torque values were observed by scanning electron microscopy (SEM) at 8 weeks. RESULTS. 1. Removal torque values of the nano-treated groups were lower than those of micro-treated groups. 2. Removal torque values were similar in the anodized RBM surface groups. 3. On the histological views, there was much of bone formation at 8 weeks, but there was no difference between 4 and 8 weeks, and between the types of implant surfaces as well. CONCLUSION. it is suggested that implant topography is more effective in removal torque test than surface chemistry. To get better clinical result, further studies should be fulfilled on the combined effect of surface topography and chemistry for the implant surface treatments.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.483-494
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• 2022

Owing to the saturation of ground spaces in downtown areas, underground spaces are being developed increasingly. Underground spaces are utilized for transportation, water supply and sewerage, communication zones, electric power zones, and various cultural complexes. In Korea, for excavating underground spaces, blasting methods using gunpowder such as the New Austrian Tunneling Method (NATM) are mainly used. However, the blasting method causes vibration and noise during tunnel excavation, generating many complaints from residents in the vicinity of the excavation site. To address this problem, various methods have been developed, and recently, vibration and noise have been reduced using deep excavation. This study predicts blast vibration changes according to the depth, under the same blasting and tunnel conditions, using numerical analysis based on the blast vibration measurement data of the GTX-A route, the tunnel cross-section drawings, and ground investigation reports. Furthermore, the necessary separation distance from densely populated areas such as residential areas is suggested by analyzing the trend of decreasing blast vibration according to the distance from ground surface directly above the blasting location.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.4
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• pp.307-314
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• 2005

After dental implant are planted into their bony site among the various growth factors associated with bone formation. BMP is expressed in the bone surrounding the implant fixture. By taking a close look at BMP2, BMP4 which are growth factors that take put in bone formation, its histologic features and radiographic bone healing patterns we would like to examine the mechanism of osseointegration. We randomly used 8 male and female house rabbit amd used diameter 5 mm height spiral shaped implants(Ostem, Korea) for animal use handled as a resorbable blast machined(RBM) surface and machined surface. 2group were formed and each group had RBM surface and machined surface implant or a simple bone cavity. After 3, 7, 14 and 28 days post surgery 2 objects were sacrificed from each group and histologic specimens were acquired. RT-PCR analysis was conducted and after H&E staining the extent of osseointegration was measured applying a histologic feature and histomorphometric analysis program. Quanitity one -4.41(Bio-Rad, USA) was used after scanning the PCR product image of the growth factors manifested in each group. According to the histomorphometric features the RBM, Machined surface group showed increased contact between bone and implant surface at 3, 7, 14 and 28 days after surgery. The BMP2 level increased in both experiment groups but remained unchanged in the contrast group. BMP4 levels stayed steady after the early post implantation period for RBM but showed decreased in the machined surface group and contrast group. The amount of contact between bone and implant surface increased with the passage of time. BMP2, BMP4 were expressed in both experimental group and contrast group. These growth factors play a role in osseointegration of implant.

• Journal of the Korean Home Economics Association
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• v.37 no.11
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• pp.49-58
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• 1999

This study is to develop the well-fit brassieres by observing the changes in the breast sizes and shapes, the surface area of the breast through the arm movements of 3 types (0$^{\circ}$ , 90$^{\circ}$ and 180$^{\circ}$) in vortical motion. The 11 elementary girls who are aged 12 participated in this experiment. To obtain the measures regarding the surface area of the breast, replicas are made at each motion. The results of this study are as fellows: 1. The changes in the breast sizes and shapes at each motion By increasing the motions of the arm movement, the following measure items are inclined to decrease: Shoulder length, Upper blast girth, Bust girth, Under bust girth, Upper bust depth, Bust depth, Under bust depth, Nipple to nipple breadth, Horizontal distance of bust, Horizontal length of the cup, Bust height, Cup size. By increasing the motions of the arm movement, the fellowing measure items are inclined to increase: Center point of shoulder~B.p., Shoulder point~B.p., Center point of shoulder~armpit, Upper Bust breadth, Bust breadth, Under bust breadth, Vertical distance of Bust. 2. The changes in the surface area of breast at each motion By making the replica to observe changes in the surface area, which are sectioned to 4 parts(area 1 to area 4), and volume of breast at each motion, the results are as follows: At 0$^{\circ}$and 180$^{\circ}$, the sizes of each part are ordered as the following: area2>area1>area4> area3. At 90$^{\circ}$, the sizes of each part are ordered as the following: area2>area1>area3>area4. Through these orders, it is found that the upper and inside part of the breast huts the inclination to increase so along as the motions of the arm movement increase. Also, the total surface area increases so long as the motions of the arm movement increase. As a reset of the F-test on the changes in the each surface areas, the surface area by arm movements, the significant differences among the each surface areas are found.