• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.209-218
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• 2010

The fatigue phenomenon, which is induced by stress accumulation due to the repeated loading of vehicles in the long term, is one of the main factors of the span of life of a steel bridge. In this paper, the effects of traffic properties on the fatigue life of ordinary short- and medium-span steel plate girder bridges that are exposed to relatively large dynamic effects are investigated. From the analysis, it was known that the fatigue life of the bridge becomes shorter with increasing traffic volume and number of large vehicles, and is affected by the weights of the vehicles. Based on the analysis results, a new parameter that can represent the traffic property that affects the fatigue life of the subject bridge is suggested, and the validity of the parameter is confirmed.

• Informatization Policy
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• v.19 no.2
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• pp.85-105
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• 2012

So far, the importance of informatization, as well as investment into it, has been growing steadily. Due to the uncertainties and risks in adopting information technologies, systematic decision-making is definitely needed in investing in a large scale information system. Based on the existing theories about the economic life span of information systems and in consideration of the actual cost involved in the adoption and operation of the systems by the financial institutions in Korea, this study presents the optimal economic life span for all types of information systems in terms of the economic cost and generalizes the optimal life span. The ultimate purpose of this study is to develop a model that could be used in anticipating the timing of economic replacement of the information system of the same type and making decisions on IT investment.

• Honam Mathematical Journal
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• v.20 no.1
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• pp.67-78
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• 1998

• Journal of the Korean Society of Safety
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• v.29 no.5
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• pp.97-103
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• 2014

To ensure durability and light weight of bridges, high-strength concrete is required for long-span deck slabs. Such a technology eventually extends the life of bridges and improves the economic efficiency. The results of this study suggests a formula for calculating the minimum thickness of long-span deck slabs built with high strength concrete. The minimum thickness is proposed based on the limit states indicated in the CEB-FIP Model Code and the Korean Highway Bridge Design Code(limit state design). The design compressive strength of concrete used for the study is 80MPa. Moreover, the required thickness for satisfying the flexural capacity and limiting deflection is estimated considering the limit state load combination. The formula for minimum thickness of deck slabs is proposed considering the ultimate limit state(ULS) and the serviceability limit state(SLS) of bridges, and by comparing the Korean Highway Bridge Design Code and similar previous studies. According to the research finding, the minimum thickness of long-span deck slab is more influenced by deflection limit than flexural capacity.

• Wind and Structures
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• v.20 no.3
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• pp.363-388
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• 2015

For controlling the vibration of specific building structure with large span, a practical method for the design of MTMD was developed according to the characteristics of structures subjected to wind loads. Based on the model of analyzing wind-induced response of large-span structure with MTMD, the optimization method of multiple tuned mass dampers for large-span roof structures subjected to wind loads was established, in which the applicable requirements for strength and fatigue life of TMD spring were considered. According to the method, the controlled modes and placements of TMDs in MTMD were determined through the quantitative analysis on modal contribution to the wind-induced dynamic response of structure. To explore the characteristics of MTMD, the parametric analysis on the effects of mass ratio, damping ratio, central tuning frequency ratio and frequency range of MTMD, was performed in the study. Then the parameters of MTMD were optimized through genetic algorithm and the optimized MTMD showed good dynamic characteristics. The robustness of the optimized MTMD was also investigated.

• Journal of Information Management
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• v.35 no.1
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• pp.93-112
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• 2004

This study is intend to analyze the cited patent life time of US patent data via more objective way. It is based on exploratory approach which is one of various methods for technology forecasting. The life spans of cited patents of specific technological field are deduced from using informetric analysis of USPA database of KISTI, which is composed of US patent data covered from 1972 to present. The statistics of the results may help to estimate the economic life span of the specific technological area for technology valuation.

• Journal of Life Science
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• v.25 no.10
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• pp.1176-1183
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• 2015

Ulmus macrocarpa has been used in Korean medicinal food material to physical disorder or tonic material. The purpose of the present study was to evaluate splenocyte life span expansion effects of Ulmus macrocarpa water extract (UMWE) in general cell culture condition. Splenocytes were handled in the presence of 100 μg/ml UMWE for several different time conditions. Live cells were detected with Hoechst 33,342 dye and cell survival molecules were identified through Western blot. Changes in level of cytokine synthesis were evaluated by ELISA. UMWE showed an effect on increased splenocyte survival. UMWE elevated slightly PI3K phosphorylation and ERK1/2 phosphorylation used at 48 hr and 96 hr. Moreover, Bcl-2 was elevated at 48 hr and 96 hr in UMWE-treated splenocytes. UMWE decreased caspase-3 level at 48 hr and 96 hr. ICAD protein increased at 48 hr culturing time. Hematopoietin IL-2 cytokine was down-regulated, however IL-4 hematopoietin cytokine was up-regulated in UMWE treated cell culture media. Increased IFN-γ levels were verified in the supernatant of UMWE-treated cells in all periods (48 hr and 96 hr). Increased patterns in the production of IL-12 cytokine occurred as compared with control after 48 and 96 hr in UMWE-treated-cell cultures. These results suggested that UMWE can prolong splenocyte life span by controlling various signal factors and cytokines.

• Journal of the Korean Wood Science and Technology
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• v.43 no.2
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• pp.177-185
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• 2015

The goal of this study is to evaluate the limitation of ASTM D 198 bending and ASTM D 3044 in determination of elastic modulus and shear modulus. Different material properties and span to depth ratios were used to analyze the effects of material property and testing conditions. The ratio of true elastic modulus to apparent elastic modulus evaluated from ASTM D 198 bending sharply decreased with increment of span to depth ratio. Shear modulus evaluated from ASTM D 198 bending decreased with increment of depth, whereas shear modulus evaluated from ASTM D 3044 was hardly influenced by increment of depth. Poisson's ratio influenced shear modulus from ASTM D 198 bending but did not influence shear modulus from ASTM D 3044. Different shearing factor was obtained for different depths of beams to correct shear modulus obtained from ASTM D 198 bending equivalent to shear modulus from theory of elasticity. Equivalent shear modulus of materials could be obtained by applying different shearing factors associated with beam depth for ASTM D 198 bending and correction factor for ASTM D 3044.

• Current Research on Agriculture and Life Sciences
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• v.32 no.1
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• pp.30-33
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• 2014

A simulation model was developed to monitor food contamination during the ripening process of Kimchi on a factory scale. The cabbages were divided into three groups: control (without salt or red pepper), samples with added salt, and samples with added salt and red pepper. The processed Kimchi was left to ripen in a refrigerator at $4^{\circ}C$ and five frog heads (contaminant) left on the surface of the cabbages in each group. For the control, the contaminant exhibited a long life span of 10 days or more, however, for the samples with salt and samples with salt and red pepper, the contaminant showed a relatively short life span. In particular, for the processed Kimchi that included salt and red pepper, the life-span of the contaminant was dramatically decreased to around 3 days. Therefore, the present results suggest that the proposed simulation trial is suitable for monitoring contamination during Kimchi production. Moreover, since the contaminant could not survive more than 3 days, this suggests that the salt concentration in the Kimchi damaged the permeability of the skin and other tissue membranes.

• Current Research on Agriculture and Life Sciences
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• v.31 no.4
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• pp.280-285
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• 2013

This study supplies basic data to develop a greenhouse model for reducing the damage to single-span greenhouses caused by strong winds and heavy snow. Single-span plastic greenhouses are predominantly used for growing crops in Korea. Thus, the safety wind speeds for single-span greenhouses were calculated and compared with the actual wind speeds and snow depths over a period of 8 years in different regions to analyze the structural safety of single-span greenhouses. The unit wind load and unit snow load were applied to different designs of single-span greenhouse according to the cultivated crop to achieve a structural analysis. As a result, the maximum section force for the wind and snow load was greatest for leaf and root vegetables, where the safety wind speeds for single-span greenhouses according to the cultivated crop were 17.7 m/s(leaf vegetables), 20.2 m/s (fruit vegetables), and 22.3 m/s (root vegetables). Thus, the single-span greenhouses were not found to be safe for the wind load in most regions, except for Hongcheon, Icheon and Sungju. Plus, the safety snow depths for single-span greenhouses according to the crop were 8.8 cm (leaf vegetables), 9.4 cm (fruit vegetables), and 11.8cm (root vegetables). Thus, when comparing the safety snow depths with the actual snow depths, the single-span greenhouses were not found to be safe. Therefore, to improve the safety of single-span greenhouses, the structures need reinforcement by reducing the interval between rafters or increasing the size of the pipes. However, additional research is needed.