• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.2
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• pp.47-64
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• 2013

Landscape structure changes over the past three decades were determined with land use and land cover(LULC) maps, and their relationships with mean air temperature time series were the analyzed for the Busan metropolitan area and South Kyeongsang Province, Korea. The geometric structures of the LULC data were quantitatively represented based on FRAGSTATS, a spatial pattern analysis program for quantifying landscape structure. FRAGSTATS-derived landscape metrics confirmed that there were major changes in LULC and landscape fragmentation in the region. Meteorological observation records showed that mean air temperature had increased from $14.1^{\circ}C$ in the 1990's to $14.8^{\circ}C$ in the 2000's in Busan. For South Kyeongsang Province, they increased from $13.2^{\circ}C$ to $13.9^{\circ}C$ during the same time period. These long-term temperature changes are correlated with typical spatial pattern changes of LULC in the southeastern region of the country. Spatial metrics analysis showed that urban area expanded from 9.7% to 26.8% of Busan while forest and agricultural land decreased by 9.6% and 14.9%, respectively over the past thirty years. The significant urbanization are tightly associated with deforestation, removal of agricultural land, and fast temperature increases since the 1990's. The urban area of South Kyeongsang Province rapidly increased, and it became 12 times as large as it was. The degree of temperature increases differed among three different sub-regions. The temperature increasing rate was lowest in the coastal region while the colder mountainous region had the highest figure.

• Composites Research
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• v.28 no.4
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• pp.155-161
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• 2015

A composite structure was fabricated with embedded impact detection capabilities for applications in Structural Health Monitoring (SHM). By embedding sensor functionality in the composite, the structure can successfully perform impact localization in real time. Smart resin, composed of $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,\;Ti)O_2$ (PNN-PZT) powder and epoxy resin with 1:30 wt%, was used instead of conventional epoxy resin in order to activate the sensor function in the composite structure. The embedded impact sensor in the composite was fabricated using Hand Lay-up and Vacuum Assisted Resin Transfer Molding(VARTM) methods to inject the smart resin into the glass-fiber fabric. The electrodes were fabricated using silver paste on both the upper and bottom sides of the specimen, then poling treatment was conducted to activate the sensor function using a high voltage amplifier at 4 kV/mm for 30 min at room temperature. The composite's piezoelectric sensitivity was measured to be 35.13 mV/N by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. Because impact sensor functionality was successfully embedded in the composite structure, various applications of this technique in the SHM industry are anticipated. In particular, impact localization on large-scale composite structures with complex geometries is feasible using this composite embedded impact sensor.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.100-107
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• 2004

The nano or micro sized structures of conducting polymer had been prepared by synthesizing the desired polymer within the pores of template of nano or micro porous membrane filter. In this study, we had tried to fabricate conducting polymer microstructures on an electrode by using electrochemical deposition adopting template synthesis. Our attention was focused on two different things, attaching template on the electrode and fabricating microstructures only at limited areas of the electrode. A conducting polymer, PEDiTT (poly 3,4-ethylenedithi-athiophene) solution was blended with PVA(polyvinyl alcohol) solution and used as an conducting adhesive. After attaching template membrane, the electrode were immersed in 0.5M pyrrole in 0.1M KCI solution, and electrochemical polymerization was performed. The growth process of the microstructures studied by SEM. The electrochemical fabrication of conducting polymer was performed by using two-electrode system. A large working electrode and a micro scale disc electrode were used for the confined area synthesis. Polymerization potential was 4V in an electrolytic solution made of KCI in deionized water. The optimum polymerization conditions were, i.e. (4V/100sec) for $250{\mu}m$ electrode and (6V/30 sec) for $10{\mu}m$ electrode.

• Journal of the Korean GEO-environmental Society
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• v.18 no.7
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• pp.13-20
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• 2017

Soil nailing is ground reinforcement method using the shear strength of ground and the pullout shear resistance force of nail. It is mainly used for reinforcement of cut slopes, earth retaining structures and retaining walls, etc. It may be designed considering the pullout resistance of nail in the case of earth retaining structure and retaining wall, but it should be designed considering not only pullout resistance but also shear and bending resistance in the case of slope. However, conservative designs considering only pullout resistance are being done and most of the studies are about increasing pullout resistance by improving of material, shape and construction method of nail. Actually, Shear bending deformations occur centering on the active surface in ground reinforced with the nail. The grout with relatively low strength is destroyed and separated from the reinforcing material. As a result, the ground is collapsed while reducing the frictional resistance rapidly. Therefore, it is necessary to develop the method to increase the shear resistance while preventing separation of nail and grout body. In this study, an experimental study was conducted on new soil nailing method which can increase shear resistance by forming protrusions through pressurized grouting after installing a packer on the outside of deformed bar.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.469-475
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• 2008

It is obvious that chloride penetration through cracks can threaten the durability of concrete substantially, according to the previous studies of author. It was proposed that crack depth corrseponded with critical crack width from the surface is a crucial factor in view of durability design of concrete structures. It is now necessary to deal with chloride penetration through microcracks characterized with the mixing features of concrete. The purpose of this study is examining the effect of mix proportional features of concrete such as coarse aggregate, high strengtherize of concrete and reinforcement of steel fiber on chloride penetration through cracks. Although small size of coarse aggregate can lead to many microcracks in concrete, the cracks should not impact on chloride penetration directly. On the contrary, chloride should penetrate through cracks easily in concrete with a large size of coarse aggregate because mixrocracks are connected to each other. Second, high strength concrete has an excellent performance to resist with chloride penetration. However, for cracked high strength concrete, its performance is reduced upto the level of ordinary concrete. Finally, steel fiber reinforcement is effective to reduce chloride penetration through cracks because steel fiber reinforcement can lead to reduce crack depth significantly.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.4
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• pp.524-534
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• 2000

Deciduous teeth can be extracted for two reasons, one due to the physiologic resorption and the other by the inflammation at the apex after traumatic injury. Physiologic resorption may be different from pathologic resorption in timing and mechanism. Therefore we resumed the different features of physiologic and pathologic resorption root surfaces. Many previous studies showed micromorphology of resorbed surface of roots of deciduous teeth. But, few studies compared physiological and pathological root resorption surfaces. In this study, we carefully observed microscopic morphologies of those two different root surfaces by scanning electron microscope and histologic features by light microscope. The resultant differences between physiologic and pathologic resorption surfaces of deciduous teeth were as follows: 1. The morphology of pathologic resorption lacunae due to inflammation varied in size and shape with irregular boundaries compared with the physiologic areas from scanning electron microscope observations. 2. From light microscope observations, several large resorption fossae containing numerous resorption lacunae were found, whereas the resorption lacunae were irregular in shape with pathologic resorption surface. 3. Numerous multinucleated giant cells were closely attached to the physiologic resorption lacunae, whereas several kinds of mesenchymal cells with numerous inflammatory cells were found in the areas adjacent to the pathologic resorption surface. 4. Light microscope findings showed that compensating cementum formation took place along some of the areas of inflammatory dentinal resorption. In conclusion, several morphological differences were present between physiologic and pathologic root resorption surfaces of human deciduous teeth. The future studies should include cytochemistry to clarify the cellular roles in resorption process observations of pulpal surfaces of coronal and radicular dentin to and the changes that occur in each phase of human deciduous tooth resorption.

• Journal of the Korean Geotechnical Society
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• v.15 no.3
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• pp.161-176
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• 1999

A powerful numerical method that can be used for modeling rock-structure interaction is the Discontinuous Deformation Analysis (D D A) method developed by Shi in 1988. In this method, rock masses are treated as systems of finite and deformable blocks. Large rock mass deformations and block movements are allowed. Although various extensions of the D D A method have been proposed in the literature, the method is not capable of modeling water-block interaction, sequential loading or unloading and rock reinforcement; three features that are needed when modeling surface or underground excavation in fractured rock. This paper presents three new extensions to the D D A method. The extensions consist of hydro-mechanical coupling between rock blocks and steady water flow in fractures, sequential loading or unloading, and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the D D A method with the new extensions are presented. Simulations of the underground excavation of the \ulcornerUnju Tunnel\ulcorner in Korea were carried out to evaluate the influence of fracture flow, excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that fracture flow and improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the D D A program with the three new extensions can now be used as a practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.61-72
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• 2016

For the construction of high-rise structures and the optimized foundation design, the use of the large-diameter PHC pile has increased. Especially, the use of the 600 mm diameter PHC pile has significantly increased. In this study, for the evaluation of the suitability of the current design practice, the 46 dynamic pile load tests, which were carried out in the 600 mm diameter preboring PHC pile, are analyzed. The end bearing capacity is obtained from the end of initial driving test and the shaft capacity is estimated from the restrike test. The allowable capacities estimated by the dynamic load test are compared with those based on the current design practice. The analyses show that the allowable end bearing capacity evaluated by the dynamic pile load test is greater than the design practice in most piles. The allowable shaft capacity, however, is smaller than the design practice in many piles. The higher end bearing capacity and the smaller shaft capacity may result from the improvement of the drilling equipment and the increase in the penetration depth. Thus, the portion of the end bearing capacity in the total capacity increases.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.5
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• pp.82-91
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• 2007

Currently, bridges are regarding as the structure with formative, scenic and environmental values more than their function as simple passageways. Because an attempt to work on the diversity of the bridge types and installation of the large structures on bridge are part of the project of the regional amenity enterprises, a study that harmonizes bridges with landscape is needed at this point in time. This background can influence the direction of bridge landscapes that considers local features by analysis of visual preferences on a bridge simulated scene. The results were as follows: analyzing the change of the simulated landscape image, forest landscape are damaged by the input of a bridge which was natural, harmonic and intimate. On the other hand, when a bridge was inserted into the ocean landscape, it was thought to improve the ocean landscape, especially, upper part form of arch bridge various or suspension bridge were improved in polished and various image. The insertion of a bridge into an urban landscape change from a negative image to a beautiful, harmonic and attractive image. The intimate, harmonic and natural image of a rural landscape was damaged by inserting a bridge. As analysis result about change of landscape preference by input of bridge, there is difference between before and after as input the bridge, and bridge influences as main object in the simulated scene. Visual preference was the highest in the ocean landscape, and the lowest in the suspension bridge in the rural landscape. The complicated shape of bridge follows on the background type difference certainly appear. Thee simulated scene preference except the urban landscape of the simulated scene fell generally Especially, fall of preference of girder bridge in the forest and ocean landscape, suspension bridge in the rural landscape appeared notedly.

• Korean Journal of Construction Engineering and Management
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• v.21 no.3
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• pp.28-38
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• 2020

The large-scaled and high-rise construction structures in recent years have increased high place work, leading to an increase in falling accidents (hereinafter, "accidents"). The need for prediction and management of unsafe acts of workers at construction sites has been raised as unsafe acts of workers are identified as the main cause of industrial accidents. This research aims at deriving the improvement effect of unsafe acts by presenting the relationship between unsafe acts of workers and accidents at construction sites as a probability. Unsafe acts of workers were derived based on the analysis of accident cases. In addition, surveys were conducted to calculate the probability of occurrence of accidents caused by unsafe acts (hereinafter, 'accident probability'). The Event Tree Analysis (ETA) was utilized to confirm the final probability according to the combination of unsafe acts and improvement effect. The accident probability by unsafe act was found to be the highest for working after drinking (95.41%) and to be the lowest for equipment and machine utilization (65.70%). The accident probability according to a combination of unsafe acts was the highest when all of the unsafe acts were conducted (13.23%) and was the lowest when none of the unsafe acts were conducted (0.00%).