• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.14-18
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• 2014

The mechanical, electrical and thermal characteristics of insulating materials may significantly affect the performance and reliability of electrical devices using superconductors. General method to provide insulating layer between coated conductors is wrapping coated conductor with Kapton tape. But uniform and compact wrapping without failure or delamination in whole coverage for long length conductor is not a simple task and need careful control. Coating of insulating layer directly on coated conductor is desirable for providing compact insulating layer rather than wrapping insulating layers around conductor. Ceramic added polymer has been widely used as an insulating material for electric machine because of its good electrical insulating properties as well as excellent heat resistance and fairy good mechanical properties. The insulating layer of coated conductor should have high breakdown voltage and possesses suitable mechanical strength and maintain adhesiveness at the cryogenic temperature where it is used and withstand stress from thermal cycling. The insulating and mechanical properties of polymer can be improved by adding functional filler. In this study, insulating layer has been made by adding ceramic particles such as $SiO_2$ to a polymer resin. The size, amount and morphology of added ceramic powder was controlled and their effect on dielectric property of the final composite was measured and discussed for optimum composite fabrication.

• Advances in Computational Design
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• v.3 no.2
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• pp.147-163
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• 2018

Cementitious composites are multiphase heterogeneous materials with distinct dissimilarity in strength under compression and tension (high under compression and very low under tension). At macro scale, the phenomenon can be well-explained as the material contains physical heterogeneity and pores. But, it is interesting to note that this dissimilarity initiates at molecular level where there is no heterogeneity. In this regard, molecular dynamics based computational investigations are carried out on cement clinkers and calcium silicate hydrate (C-S-H) under tension and compression to trace out the origin of dissimilarity. In the study, effect of strain rate, size of computational volume and presence of un-structured atoms on the obtained response is also investigated. It is identified that certain type of molecular interactions and the molecular structural parameters are responsible for causing the dissimilarity in behavior. Hence, the judiciously modified or tailored molecular structure would not only be able to reduce the extent of dissimilarity, it would also be capable of incorporating the desired properties in heterogeneous composites. The findings of this study would facilitate to take step to scientifically alter the structure of cementitious composites to attain the desired mechanical properties.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.342-348
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• 2005

This study was carried out fusion-welded butt joints in SWS 490A high strength steel subjected to tensile test that load-deflection curve. The windowed or short-time Fourier transform (WFT or SIFT) makes possible for the analysis of non-stationary or transient signals into a joint time-frequency domain and the wavelet transform (WT) is used to decompose the acoustic emission (AE) signal into various discrete series of sequences over different frequency bands. In this paper, for acoustic emission signal analysis to use a continuous wavelet transform, in which the Gabor wavelet base on a Gaussian window function is applied to the time-frequency domain. A wavelet transform is demonstrated and the plots are very powerful in the recognition of the acoustic emission features. As a result, the technique of acoustic emission is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• Korean Journal of Medicinal Crop Science
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• v.13 no.6
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• pp.273-277
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• 2005

Adventitious shoots were directly induced from leaf explants of R. glutinosa, an important medicinal plant. Proliferating shoot cultures were obtained by culturing leaf discs on Murashige and Skoog(MS) medium alone or combination with auxins and cytokinins. MS medium supplemented with 1 $mg/{\ell}\;BA\;and\;2\;mg/{\ell}$ IAA was the most effective, providing high shoot bud formation frequency without formation of intervening callus. The effect of leaf age on adventitious shoot formation was also investigated. The maximum shoot bud production (93.4%) was achived using 3rd leaf from apex of 6 weeks old plantlets after seed germination. Plantlet were rooted on an half-strength MS (1/2MS) medium containing 0.1 $mg/{\ell}\;IBA$. This prtocol is useful for clonal propagation and Agrobacterium-mediated transforamtion in R. glutinosa.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.781-784
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• 2004

Method of Steel plate reinforced by fiber sheet is advantageous in the secure loading facility. For this method are a light weight and a high strength, the thickness of steel can be reduced Effects of composite system are depreciated when the thickness of steel is thin. This is the result of the difference of ductility ratio with steel plate. Steel plate reinforced by fiber sheets confirms the ability of transformation. This is the result of the property of steel materials Steel plate reinforced by fiber sheet didn't display an enough performance when theadhesives are epoxy rosin. This is the result of the slide of the surface of stee1. The adhesive ability is varied by the number and span of anchor bolts. There wasn't happening the separation between steel and epoxy. Thus the method used in combination with anchor and epoxy is best excellent. This is the result of the upward of accumulation effects Shearing force is in proportion to the number of bolts. But the ability of shearing force per one bolt is reducing. Thickness of steel plate reinforced by fiber sheet must be designed so that steel is endure before concrete is wreck.

• KIEAE Journal
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• v.5 no.3
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• pp.49-56
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• 2005

Recently the Volatile Organic Compound, HCHO, a harmful object spout from the construction materials is made an issue of social problem. Also the appearance of the building where the confidentiality is high was interior air pollution and it was brought about a huge problem. The government research facility and a relation industry sector conducts a many effort to improves like this actual condition. The Diverse ability building material which contains the natural material of the jade, the charcoal and the hwangto instead of the finish material which contains the harmful chemical material, is becoming development and utility. Hereupon the study have carried out research on hwangto plaster that was composed of hwangto and rice straw. The result of test that is deduced by basic proportion is properly appeared with suitable ratio of the hwangto and the sand to 4:6~5:5 by the compressive strength and crack control, workability. The result of test, that adds the rice straw to basic blending for a crack control, appeared with the fact that it is most suitable 3%to add the rice straw that has a length of 0.5cm~2cm. The result of test that plaster over the large size to compare a cement plaster with a hwangto plaster show a similar efficiency by workability. Also it controlled the crack and peeling off actual condition which is discovered from the hwangto plaster of existing perfectly.

• Advances in environmental research
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• v.3 no.4
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• pp.337-353
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• 2014

The determination of the effectiveness of the immobilization of blasting dust (waste generated in galvanic activities) in cement matrix, as well of mechanical, physical and microstructural properties of concrete paving blocks produced with partial replacement of cement was the objective of this work. The results showed that blasting dust has high percentage of silica in the composition and very fine particle size, characteristics that qualify it for replacement of cement in manufacturing concrete blocks. The replacement of Portland cement by up to 5% residues did not cause a significant loss in compressive strength nor increase in water absorption of the blocks. Chemical tests indicated that there is no problem of leaching or solubilization of contaminants to the environment during the useful life of the concrete blocks, since the solidification/stabilization process led to the immobilization of waste in the cement mass. Therefore, the use of blasting dust in the manufacture of concrete paving blocks is promising, thus being not only an alternative for proper disposal of such waste as well as a possibility of saving raw materials used in the construction industry.

• Advances in concrete construction
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• v.4 no.4
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• pp.319-332
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• 2016

In most cases strengthening reinforced concrete columns exposed to high strain rate is to be expected especially within weak designed structures. A special type of loading is instantaneous loading. Rapid loading can be observed in structural columns exposed to axial loads (e.g., caused by the weight of the upper floors during a vertical earthquake and loads caused by damage and collapse of upper floors and pillars of bridges).Subsequently, this study examines the behavior of reinforced concrete columns under rapid loading so as to understand patterns of failure mechanism, failure capacity and strain rate using finite element code. And examines the behavior of reinforced concrete columns at different support conditions and various loading rate, where the concrete columns were reinforced using various counts of FRP (Fiber Reinforcement Polymer) layers with different lengths. The results were compared against other experimental outcomes and the CEB-FIP formula code for considering the dynamic strength increasing factor for concrete materials. This study reveals that the finite element behavior and failure mode, where the results show that the bearing capacity increased with increasing the loading rate. CFRP layers increased the bearing capacity by 20% and also increased the strain capacity by 50% through confining the concrete.

• Journal of the Korean Society of Safety
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• v.28 no.3
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• pp.18-22
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• 2013

The Co-base super heat resisting alloy ECY768 is employed in gas turbine because of its high temperature strength and oxidation resistance. The prediction of fatigue life for superalloy is important for improving the efficiency. In this paper, low cycle fatigue tests are performed as variables of total strain range and temperature. The relations between strain energy density and number of cycle to failure are examined in order to predict the low cycle fatigue life of ECY768 super alloy. The lives predicted by strain energy methods are found to coincide with experimental data and results obtained from the Coffin-Manson method. The fatigue lives is evaluated using predicted by Coffin-Manson method and strain energy methods is compared with the measured fatigue lives at different temperatures. The microstructure observing was performed for how affect able to low-cycle fatigue life by increasing the temperature.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.181-189
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• 2001

Recently, the need for strengthening reinforced concrete(R.C.) structure has been increased, particularly when there is an increase in load requirements, a change in use, a degradation problem, or design/construction defects. The use of composite materials for structural repair presents several advantages and has been investigated all over the world. It is well known that the incorporation of carbon fiber sheet(CFS) with concrete is one of the most effective ways to strengthen the R.C. structure. In this papers, experimentally investigated the ductile behavior of the R.C. beams strengthened with CFS, and provided the basic data for design of R.C. beams strengthened with CFS. Tests were carried out with 15 beams ($20cm{\times}30cm{\times}240cm$) reinforced with CFS, and with parameters including and the ratio of tensile reinforcement to that of balanced condition and number of CFS. The results show that strengthened and non-strengthened beams exhibit different ductile behovior. Non-strengthened beams showed increase of ductility as amount of the tensile reinforcement decreased. However, bearing capacity of the CFS-strengthened beams are dictated by the strength of the CFS layers that a very high ductility is indicated for the beams with large number of CFS.