• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.95-109
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• 2018

Recently, GRS (Geosynthetic Retaining Segmental) wall has been widely used as a method to replace concrete retaining wall because of its excellent structural stability and economic efficiency. It has been variously applied for foundation, slope, road as well as retaining wall. The GRS wall system, however, has a weak point that is serious crack of wall due to stress concentration at curved part of it. In this study, therefore, behaviour of GRS wall according to shape of it, shich has convex and concave, are analysed and compared using Finite Element analysis as the fundamental study for design optimization. Results including lateral deflection, settlements of ground surface and wall obtained from 2D FE analysis are compared between straight and curved parts from 3D FE analysis.

• Composites Research
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• v.27 no.2
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• pp.52-58
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• 2014

Short fiber reinforced composites manufactured by injection molding have diverse fiber orientations variable with measuring positions even in the same specimen, which is caused by the flow induced fiber orientation. Fiber orientations considerably affect the mechanical and thermal properties of final composite products. In this study, fiber orientation of injection molded carbon fiber reinforced PA6/PPO composite was measured at several points of the specimen by optical microscopy analysis and the corresponding izod impact strength, coefficients of thermal expansion (CTE) were also measured to investigate the influence of local fiber orientation on the mechanical and thermal properties. Izod impact strength where fiber was perpendicular to the direction of crack propagation was higher than where fiber was parallel to the direction, which could be explained be the impact resistance reinforcing mechanism by fiber orientation. CTE was also lower where fiber was parallel to the measurement direction of CTE than where fiber was perpendicular to the direction, which could be also explained by the dimensional stability mechanism by fiber orientation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.743-748
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• 2010

The stability forecasting of rock slope is more difficult than soil slope because catching the sign of failure in monitoring is not easy and deformation of the rock is small in failure process. But in the rock slope, there is small deformation like crack propagation in rock itself and it accumulates gradually in failure process. If it is possible to detect the small change in the rock slope, we can know the failure time exactly. Because the individual signal is gathered in the acoustic emission monitoring, it is possible to monitoring the slope if many sound signal is accumulated. Detection test of acoustic emission was performed. Uniaxial, two types of bending test, and two plane shear test were done with various cement paste sample. Wave propagation velocity of uniaxial test sample was increased with curing time. Wave Analysis give us the result that there is a AE sign signal before the failure, the AE count is suddenly increased. And frequency level 125kHz before failure is changed to level 200-250kHz after failure. In two plane shear test we can catch the AE signal and can know the failure type from wave shape. Monitoring test site is tunnel slope in Hongcheon but special signal is not collected.

• Membrane Journal
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• v.21 no.2
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• pp.148-154
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• 2011

Metal-ceramic composite membrane have been developed to separate hydrogen from mixed gases, particularly product streams generated during coal gasification and methane reforming. Cermet membrane was fabricated with palladium as hydrogen-permeable metal and $Y_2O_3$-stabilized $ZrO_2$ (YSZ) as ceramic supporter. As-prepared membrane showed dense structure with continuous channel of palladium. The hydrogen flux of Pd/YSZ membrane have been measured in the range of 0.5~2 atm with 100% hydrogen gas. The results indicate that the hydrogen flux was 0.333 mL/$min{\cdot}cm^2$ at $450^{\circ}C$ and 2 atm. The crack was formed in the surface and cross-section of membrane.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.11
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• pp.250-258
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• 2019

The seismic performance and stability of operating facilities installed in domestic power plants need to be verified because of the increased incidence of earthquakes resulting in power plant damage due to the overturning failure of electric operating facilities. In this study, a structural performance evaluation of the anchor bolts constructed to setup the operating facilities on concrete slabs was carried out through an on-site inspection of power plants, called Daechung-Dam. M10 J hook and M12 J hook anchor bolts were installed in the field unit. According to the ASTM E 488-96 specifications, anchor bolt pullout and shear tests were carried out and compared with the anchor-bolt design standards. The results from the tension and shear pullout tests showed that the M10 and M12 J hook anchor bolts had higher performance than the required design load. Thus, they were found to be safe enough. Nevertheless, more research in the field of analytical study will be needed in the near future.

• Journal of Conservation Science
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• v.8 no.1 s.11
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• pp.1-9
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• 1999

The present aspect of the Seoggulam is the result of natural weathering of the rocks and influences by mankind. The rocks constituting the Seoggulam is granodiorite of medium and coarse grains which show brown to dark brown weathered surface resulted mainly from chemical weathering of feldspars. It also shows partly milky white or black colors due to influences by weathering products of cement used in the concrete dome and cracks. There are cracks and crack zones with very small cracks which may be formed by strong weathering and influences of shocks during operations of reconstitution and repair. However, for the better conservation, it must be considered to maintain the balances of temperature and moisture, especially relative moisture in places within the room, structural stability, and the influences of vibration made up by some reasons.

• Computers and Concrete
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• v.17 no.1
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• pp.1-27
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• 2016

Final construction project cost is significantly determined by construction rate. The Industrialized Building System (IBS) was promoted to enhance the importance of prefabrication technology rather than conventional methods in construction. Ensuring the stability of a building constructed by using IBS is a challenging issue. Accordingly, the connections in a prefabricated building have a basic, natural, and essential role in providing the best continuity among the members of the building. Deficiencies of conventional precast connections were observed when precast buildings experience a large induced load, such as earthquakes and other disasters. Thus, researchers aim to determine the behavior of precast concrete structure with a specific type of connection. To clarify this problem, this study investigates the capacity behavior of precast concrete panel connections for industrial buildings with a new type of precast wall-to-wall connection (i.e., U-shaped steel channel connection). This capacity behavior is compared with the capacity behavior of precast concrete panel connections for industrial buildings that used a common approach (i.e., loop connection), which is subjected to monotonic loading as in-plane and out-of-plane loading by developing a finite element model. The principal stress distribution, deformation of concrete panels and welded wire mesh (BRC) reinforcements, plastic strain trend in the concrete panels and connections, and crack propagations are investigated for the aforementioned connection. Pushover analysis revealed that loop connections have significant defects in terms of strength for in-plane and out-of-plane loads at three translational degrees of freedom compared with the U-shaped steel channel connection.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.785-788
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• 2008

This study is focused on applying heavyweight concrete to ballast used to have stability of a ship. Generally, heavyweight concrete is made from a high density aggregate like magnetite or limonite. However, these materials are hard to obtain them from relevant companies and so expensive. Therefore, this study plans to product heavyweight ballast concrete which is easy to obtain by recycled iron slag. Heavyweight ballast concrete isn't required to meet some compressive strength in use, but it is required to have high flowable and 2.7t/m3 of bulk density to fill the ballast tank densely. The designed field mix proportion of concrete based on the results of pre-experiment shows it can control the temperature crack and has superior chloride corrosion resistance after conducting chloride corrosion experiment. Also, it is prefer that before airtightness voltile corrosion inhibiter(VCI) is added in airtight space of shipyard.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.702-713
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• 2003

The importance of protection for data and information is increasing by the rapid development of information communication and network. And the concern for protecting private information is also growing due to the increasing demand for lots of services by users. Asymmetric cryptosystem is the mainstream in encryption system rather than symmetric cryptosystem by above reasons. But asymmetric cryptosystem is restricted in applying fields by the reason it takes more times to process than symmetric cryptosystem. In this paper, encryption system which executes authentication works of asymmetric cryptosystem by means of symmetric cryptosystem. The proposed cryptosystem uses an algorithms combines that combines block cipherment with stream cipherment and has a high stability in aspect of secret rate by means of transition of key sequence according to the information of plaintext while symmetric/asymmetric cryptosystem conducts encipherment/deciphermeent using a fixed key. Consequently, it is very difficult to crack although unauthenticator acquires the key information. So, the proposed encryption system which has a certification function of asymmetric cryptosystem and a processing time equivalent to symmetric cryptosystems will be highly useful to authorize data or exchange important information.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.17-24
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• 2008

Many problems exist in the current cast in place concrete lining used in domestic tunnel construction. Especially, the crack of tunnel lining brings about a social and economic problem. It has a lot of influence on stability of structure and the fine finish of lining. So enormous repair-work and reinforcement of tunnel lining could occur an running out of government's budget. In our country, there are domestic production enterprises which produce a special pre-cast concrete product, but the technical level of them is still far behind compared to developed countries. Also, optimum steam coring method is important for the production of high quality product. But there is no regulation of steam curing method in our country. This study is to investigate the properties of PC panel according to the variation of steam curing conditions such as presteaming time and rate of temperature rise. The result shows that the optimum presteaming time of steam curing method in PC panel is more than 1 hour and the desirable rate of temperature in curing chamber is about $20^{\circ}C/hr$.