• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.259-269
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• 2005

This paper describes the application of genetic algorithm for the discrete optimum design of reinforced concrete continuous beams. The objective is to minimize the total cost of reinforced concrete beams including the costs of concrete, form work, main reinforcement and stirrup. The flexural and shear strength, deflection, crack, spacing of reinforcement, concrete cover, upper-lower bounds on main reinforcement, beam width-depth ratio and anchorage for main reinforcement are considered as the constraints. The width and effective depth of beam and steel area are taken as design variables, and those are selected among the discrete design space which is composed with dimensions and steel area being used from in practice. Optimum result obtained from GA is compared with other literature to verify the validity of GA. To show the applicability and efficiency of GA, it is applied to three and five span reinforced concrete beams satisfying with the Korean standard specifications.

• Journal of Periodontal and Implant Science
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• v.38 no.1
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• pp.91-96
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• 2008

Purpose: One of the main objectives of periodontal reconstructive surgery is the coverage of exposed roots that occur due to gingival recession. and Aestheic concerns are usually the reason to perform root coverage procedure. This case report was performed to evaluate the effect of root coverage using subepithelial connective tissue graft(SCTG) on Miller's Class I marginal tissue recession. Materials and Methods: One patient, with two Miller's class I marginal tissue recession on both maxiallay canines, was treated with root coverage using SCTG (modified Nelson's technique). At baseline, the following measurements were recorded: 1) recession depth; 2) width of keratinized giniga. At 9, 10 months post-surgery, all clinical measurements were repeated. Result: 1) The mean root coverage from baseline to 9, 10 months post-surgery was 92.3%. 2) The mean recession depth decreased from 6.5 mm to 0.5 mm. 3) The mean width of keratinized gingiva increased from 1.25 mm to 3.5 mm. Conclusion: Within the above results, root coverage using SCTG is an effective procedure to cover Miller's class I marginal tissue recession defect. Also, patient with aesthetic concern could be satisfied with this result.

• Journal of Advanced Navigation Technology
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• v.27 no.4
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• pp.488-494
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• 2023

In this paper, scenario-based urban flood prediction for the entire Jinju city was performed, and a simulation domain was constructed using G2D as a 2-dimensional urban flood analysis model. The domain configuration is DEM, and the land cover map is used to set the roughness coefficient for each grid. The input data of the model are water level, water depth and flow rate. In the simulation of the built G2D model, virtual rainfall (3 mm/10 min rainfall given to all grids for 5 hours) and virtual flow were applied. And, a GPU acceleration technique was applied to determine whether to run the flood analysis model in the target area. As a result of the simulation, it was confirmed that the high-resolution flood analysis time was significantly shortened and the flood depth for visual flood judgment could be created for each simulation time.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.223-238
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• 2023

This research presents the actual situation analysis and suggestions for the changes, experiences, and process of adaptation that college students have experienced throughout their studies and life over the past two years and more. In-depth interviews were conducted with university students, who are educational objects, and qualitative analysis methods were used to explore the overall living experiences under the pandemic situation. The interview questions were composed to cover classes, life, and emotional experiences after COVID-19, and the result of analyzing the responses boiled down to four super-categories of 'adaptation process to a new system, daily incontinence, struggle for health, and longing for connection.' This study is significant in that it analyzed the experiences and intimate changes of individual college students in unexpected and challenging situations, and urged the myriad aspects that universities, society, and the government should illuminate and respond to.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.155-167
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• 2024

In Korea, many solar power generation facilities are being installed in mountainous regions, which cover 70% of the country' area. This study aimed to analyze the slope characteristics of solar power generation facilities installed in such regions, considering the potential for mountain hazards. A database was created for 663 mountainous solar power generation facilities in Gangwon province, including data on area, slope angle, slope direction, altitude, and soil depth. GIS techniques were used to analyze the slope characteristics of these facilities. The area of solar power generation facilities installed in the Gangwon Mountains ranges from 606 to 320,718 m². We found that a notable number of these facilities have slopes exceeding the permit standards for mountain solar power installations and steep slope criteria. In addition, most facilities are located south, making them vulnerable to landslides. The correlation between soil depth and slope or topographical altitude was found to be quite low.

• Computers and Concrete
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• v.12 no.5
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• pp.669-680
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• 2013

This paper unveils a new computer based stabilization methodology for automated modeling analysis and its experimental verification for corrosion in reinforced concrete structures under the effect of varying oxygen concentration. Various corrosion cells with different concrete compositions under four different environmental conditions (air dry, submerged, 95% R.H and alternate wetting-drying) have been investigated under controlled laboratory conditions. The results of these laboratory tests were utilized with an automated computer-aided simulation model. This model based on mass and energy stabilization through the porous media for the corrosion process was coupled with modified stabilization methodology. By this coupling, it was possible to predict, maintain and transfer the influence of oxygen concentration on the corrosion rate of the reinforcement in concrete under various defined conditions satisfactorily. The variation in oxygen concentration available for corrosion reaction has been taken into account simulating the actual field conditions such as by varying concrete cover depth, relative humidity, water-cement ratio etc. The modeling task has been incorporated by the use of a computer based durability model as a finite element computational approach for stabilizing the effect of oxygen on corrosion of reinforced concrete structures.

• Advances in Computational Design
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• v.2 no.2
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• pp.147-168
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• 2017

Over the past couple decades, externally bonded fiber reinforced polymer (FRP) composites have emerged as a repair and strengthening material for many concrete infrastructure applications. This paper presents an analytical investigation of the use of carbon FRP (CFRP) for a specific problem that occurs in concrete bridge girders wherein the girder ends are damaged by excessive exposure to deicing salts and numerous freezing/thawing cycles. A 3D finite element (FE) model of a full scale prestressed concrete (PC) I-girder is used to investigate the effect of damage to the cover concrete and stirrups in the end region of the girder. Parametric studies are performed using externally bonded CFRP shear laminates to determine the most effective repair schemes for the damaged end region under a short shear span-to-depth ratio. Experimental results on shear pull off tests of CFRP laminates that have undergone accelerated aging are used to calibrate a bond stress-slip model for the interface between the FRP and concrete substrate and approximate the reduced bond stress-slip properties associated with exposure to the environment that causes this type of end region damage. The results of these analyses indicate that this particular application of this material can be effective in recovering the original strength of PC bridge girders with damaged end regions, even after environmental aging.

• Fisheries and Aquatic Sciences
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• v.18 no.3
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• pp.325-332
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• 2015

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Geomoondo and Jejudo in west of South sea, Korea by conver-net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k't as estimated by peak event analysis. The escape rate of juvenile fish in conver-net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

• Journal of Periodontal and Implant Science
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• v.25 no.1
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• pp.146-152
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• 1995

A mucogingival grafting procedure has been developed to cover denuded root surfaces. The subepithelial connective tissue graft is composed of a free connective tissue graft and an overlying pedicle graft. The source of connective tissue graft were trap door approach and thining of a full thickness palatal flap. The purpose of this study was compare a two different connective tissue obtaining method. In this study, where palatal pocket was present, pocket elimination was performed, and the tissue normally discarded after thinning of the palatal flap was used as a grafting material. The results were as follows : 1. The mean difference between trap door approach and thinning procedure for root coverage were $2.1{\pm}O.lmm$, $2.2{\pm}O.2mm$. 2. The mean difference between trap door approach and thinning procedure for pocket depth change were $O.2{\pm}O.lmm$, $O.2{\pm}O.2mm$. 3. The mean difference between trap door approach and thinning procedure for attachment gain were $2.1{\pm}O.2mm$, $2.4{\pm}O.2mm$. 4. The esthetics in recipient site, both color match and tissue contour, were acceptable to the patient in all cases. 5. Therefore, thinning procedure were similar to trap door approach in root coverage effect.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.239-246
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• 2004

To improve the durability of concrete structure, we usually consider the reduction of water-cement ratio, the increase of concrete cover depth and the use of mineral admixtures. The use of admixtures make concrete more durable and tighten against water in recent papers so it is needed to study more about the relationship between the admixtures and the chloride ion diffusion. Therefore we analyzed the correlation between chloride ion diffusion and physical properties such as compressive strength, void ratio, air permeability of the concrete, and tried to use them as fundamental data for analyzing chloride ion diffusion mechanism of the concrete mixed with mineral admixtures.