• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.7-12
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• 2008

This paper described results for desiging the best effective bushing geometry by comparing the distribution of the electric field according to bushing geometry. Twelve cases of the geometrical change are tried to analysis. Improvement of the insulation strength related with the vector and the electric field distribution are reached to about 0.7[%] and $21{\sim}26[%]$ by changing the electrode length, respectively. Moreover, in cases of the change of insulator thickness at high-voltage parts, the insulation strength relevant to the same parameters as mentioned above are 2[%] and $23{\sim}43[%]$, respectively Consequently, the quenching voltage for interrupting the partial discharge might be improved due to increasing the insulation strength by the geometrical change.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.669-674
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• 2001

Electric Arc Furnace Dust (EAF Dust) Is residual dust produced during the manufacturing of metal products from heavily heated electric arc furnace. Many researches have focused on recycling and reusing EAF Dust for industrial and construction purposes. However, most of these researches were aimed at obtaining useful heavy metal powders by treating toxic metallic materials in EAF Dust. Also, few researches dealt with using EAF Dust as admixture in concrete mixture (i.e., slag dust). In this study, EAF Dust is used as admixture in concrete mixture content considering economical feasibility and construction applicability. The concrete specimens mixed with EAF Dust is then tested in compression and tension to study its strength and ductility as well as its failure mechanism. The compression and tension (by split cylinder test) test results are compared to the results from the specimens without EAF Dust to understand the chemical stability and mechanical characteristic of concrete specimens with EAF Dust. For the experiment, 6 types of admixture added concrete were studied: ⑴Combination of EAF Dust and blast-furnace slag in 1 to 1 ratio, ⑵Combination of EAF Dust and blast-furnace slag in 1 to 2 ratio, ⑶EAF Dust only, ⑷blast-furnace slag only, ⑸fly ash only, and ⑹no admixture. The experimental results show that the strength of EAF Dust added specimen has lower early age strength but higher 28 day strength when compared to other specimens. Also, the Elastic Modulus of EAF Dust is higher(28 days) than other specimens. The study results prove that EAF Dust can be used as an effective admixture in concrete for specific usages.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.106-111
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• 2014

Welding is very popular method for joining two or more metals. However, welding causes residual stress and distortion and these give a bad influence to the structure strength. In this paper, TIG welding technique was performed to investigate the joint characteristics of AISI321 steel. For its evaluation, the orthogonal array method and variance analysis were applied with three factors of electric current, travel speed and argon gas and also three levels of each factor to tensile tests for optimum design. From the results, the increaser weld speed the narrower bead width and the lower weld penetration. The increaser electric current the brighter argon gas and the wider bead width. Also weld speed influenced most on the tensile strength and presumption range of tensile strength at optimal condition from reliability 95% was estimated to $635.02{\pm}14.64$. In addition the increaser weld speed and electric current the fracture occurred around bead vicinity.

• Computers and Concrete
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• v.16 no.3
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• pp.343-356
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• 2015

1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.969-972
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• 1992

It is shown that the ac breakdown strength, treeing phenomena, oxidation level, and crystallinity of unaged and aged distribution CV cables vary with XLPE insulations (characterizing anti-oxidation) and curing process. The maximum size of bow-tie tree in insulation influenced on the decrease of ac breakdown strength and the increase of oxidation level and crystallinity of XLPE according to aging time lead to increase the size and density of bow-tie trees.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.32-32
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• 2010

A epoxy/multilayered silicate nanocomposite was prepared by a new AC electric application method and micro silica particle was poured into the nanocomposite in order to prepare epoxy/micro-and-nano- mixed composites (EMNC). Electric insulation breakdown strength was measured in a sphere-sphere electrode system designed for the prevention of edge breakdown and the data were estimated by Weibull plot. As the exfoliated silicate nano-plates were homogeniously dispersed in the micro silica particles, the insulation property was higherd.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.29-35
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• 2003

In this research 4 plate type ER-Valves which have same surface but different width and length are designed and an experimental apparatus is constructed. With this experimental apparatus, flow rate and pressure drop of ER fluid flowing in ER-valves are measured with varying electric field strength of ER-valve, and relation between valve types and pressure drop is also experimented. ER fluid is made silicon oil mixed with 40wt% starch having hydrous particles. If we allow the same electric field in the ER-Valve, we came to how that the pressure drop is effected by the electrode length and electrode width. When the strength of the electric field increased, the pressure drop happened big and the flow rate decreased.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.127-134
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• 2015

Recently, the external bonding of carbon fiber reinforced polymer (CFRP) sheets has come to be regarded as a very effective method for strengthening of reinforced concrete structures. The behavior of CFRP-strengthened RC structure is mainly governed by the interfacial behavior, which represents the stress transfer and relative slip between concrete and the CFRP sheet. In this study, the effects of bonded length, width and concrete strength on the interfacial behavior are verified and a bond-slip model is proposed. The proposed bond-slip model has nonlinear ascending regions and exponential descending regions, facilitated by modifying the conventional bilinear bond-slip model. Finite element analysis results of interface element implemented with bond-slip model have shown good agreement with the experimental results performed in this study. It is found that the failure load and strain distribution predicted by finite element analysis with the proposed bond-slip are in good agreement with results of experiments.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.131-132
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• 2022

Looking at recent construction cases at winter construction sites, there is a risk that heat sources such as kerosene fans and fossil fuels (brown coal, molded carbon) used in concrete will cure rapidly, so in situations where further curing is impossible after formwork removal, the outer wall and the entire slab are exposed to rapid external deterioration, resulting in delays in concrete strength expression and until collapse accidents. In this study, we applied kerosene fans and tropical circulating electric heat fans mainly used as curing heat sources at construction sites, comparative analysis. also verified the performance of structures during concrete curing due to thermal convention / circulation performance, concrete demand strength expression, and implementation of electric heat fans by heavy disaster methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.277-278
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• 2010