• Computers and Concrete
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• v.8 no.2
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• pp.229-241
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• 2011

In this work, cement paste samples with 1% (by cement mass) of a conductive carbon fiber admixture have been studied under uniaxial compression. Three different arrangements were used to measure the resistivity of the samples. According to the results obtained, the resistance should be measured using the four wire method in order to obtain good sensitivity and repeatability. The effect of the load value and the load rate on the fractional change of the volume resistivity has been determined. It has been observed that the gage factor (fractional change in resistance respect to strain) increases when the maximum load is increased, and the loading rate does not affect significantly this parameter. The effect of the sample ambient humidity on the material piezoresistivity has also been studied, showing that the response of the composite is highly affected by this parameter.

• Magazine of the Korea Concrete Institute
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• v.2 no.2
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• pp.63-72
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• 1990

In this study, an optimization design of reinforced concrete structures is performed by using the structural optimization techniques based on the LRFD criteria. The target reliability index is estimated by the optimal reliability index considering the expected cost which is taken as a sum of the structural cost and the expected costs due to failure of the structure. The load and resistance factors calculated by using level I reliability theory with the target reliability index are compared for each load combination (D+L, D+L+w). The results of this study show that the resistance factors are ${\phi}_{M}$=0.90, ${\phi}_{V}$==0.70, ${\phi}_{C}$==0.65 and the load factors are 1.20D + 1.70L, 1.07L + 0.07L + 1.10W. The optimization techinques used to this study are S.L.P. The optimization design based on the LRFD criteria is more economical and rational than other criteria.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.546-551
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• 2009

In this paper, we studied insulation characteristics of LED lamps for load and street lighting. LED lamps can be divided into internal type and external type according to converter type. In this study, we analyzed technology standard, K(Electrical Appliances Safety Standards) and KS(Korean Industrial Standards) about insulation resistance for LED lamps for load and street lighting, and measured insulation resistances for each measured point. Mostly, insulation resistances were measured high more than regulation value but some measured points were measured badly. We expect that the results of these experiments would be helpful for electrical safety of LED lighting installation, manufacture, construction and maintenance.

• Korean Journal of Materials Research
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• v.12 no.2
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• pp.103-111
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• 2002

The thermally insulated underground pipelines have been used for district heating system. The sensor wire embedded in the insulation was used for monitoring the insulating resistance between the sensor wire and the pipe. The resistance measurement system detects corrosion of steel pipe under insulation. The corrosion and stress corrosion cracking(SCC) characteristics of sensor wire in synthetic ground water were investigated using the electrochemical methods and constant load SCC tests. The polarization tests were used to study the electrochemical behavior of sensor wire. The sensor wire was passivated at temperatures ranging from 25 to $95^{\circ}C$. However, the applied sensing current larger than passive current resulted in breakdown of passive film. The constant load SCC tests were performed to investigate the effects of applied current and load on the fracture behavior. Stress-corrosion cracks initiated at pits that were produced by sensing current. The growth of the pit involves a tunnelling mechanism, which leads to ductile fracture.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1114-1119
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• 2010

Pile foundations have been used for upholding superstructure's loads. The researches on pile foundations subjected to compressive forces or horizontal loads have been actively carried out. However, recently, pile foundations, which are subjected to pull-out forces, are getting increased. The study on the pull-out resistance of piles becomes to be important. In addition, it is expected that belled piles will be used more and more, since the belled piles are effective to resist the pull-out forces. But there is still a lack of research on pull-out resistance of belled piles. Therefore, in order to investigate the resisting effect against pull-out of belled piles which is embedded in cohesionless soil. a series of pull-out test is performed on belled piles in field. Especially, the relation between load and displacement is analyzed through the pull-out test.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.198-201
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• 2002

It has been well-blown that sandwich structures are efficient to resist bending loads by increasing the moment of inertia of the panel. However, the accurate theoretical prediction of failure load and its optimization of sandwich beams for strength under concentrated loads were so complicated. Moreover, the appropriate selection of the variables, such as face thickness, core density and core thickness of the sandwich beam with many theories has continuously researched to satisfy for the given strength to weight structural requirement. There will be interesting to investigate the effect of those variables with its optimization for the load resistance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.05a
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• pp.12-13
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• 2019

The bearing capacity of the wall against the eccentric load when the washbasin was attached on the ALC block wall was tested. Test methods are BS EN 14688 and BS 5234-2. Tests in accordance with BS EN 14688 showed that the holding capacity of steel was much stronger and more stable when HA-II (chemical anchor) was used than when the washbasin was fixed using HA-I (plastic anchor). As an experimental result according to the Annex K of BS 5234-2, the bearing capacity of ALC block wall corresponded to the "stage in which the force works(performance grade) 1,500N" for all of the cases where a washbasin is fixed using two types of the wall's dedicated anchors(HA-I and HA-II).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.2038-2040
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• 2009

This paper studies the state estimation problem for the current of DC/DC boost converters with parasitic inductor resistance. The parasitic resistance increases the system uncertainty when the output load variation occurs. In order to enhance the observation performance of the Luenberger observer this paper includes the integral of the estimation error signal to the estimation algorithm. By using the proposed PI observer the converter current signal is successfully reconstructed with the voltage measurement regardless of the load uncertainty. Computer simulation has been carried out by using Simulink/Sim Power System. Simulation results show the proposed method maintains robust estimation performance against the model uncertainty.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.176-179
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• 2005

Spray casting of hypereutectic Al-Si based alloy has been reported to provide distinct advantages over ingot metallurgy (IM) or rapid solidification/powder metallurgy (RS/PM) process in terms of microstructure refinement. Hypereutectic Al-Si based alloys have been regarded attractive for automotive and aerospace application, due to high specific strength, good wear resistance, low coefficient of thermal expansion, high thermal stability, and good creep resistance. In this study, hypereutectic Al-25Si-2.0Cu-1.0Mg alloy was prepared by OSPREY spray casting process. High temperature deformation behavior of the hypereutectic Al-Si based alloy has been investigated by applying the internal variable theory proposed by Chang et al. The change of strain rate sensitivity and Creep transition were analyzed by using the load relaxation test and constant creep test.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.1
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• pp.70-76
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• 1993

Burnishing, as a micro plastic working, is a finishing process used in conjuction with or in replacement of reaming, honing, lapping, and/or grinding. The tool which is a smooth, round steel ball slightly larger than the bore is pushed through pre-machined hole, leaving a closely controlled finish. The major application of the processes is to improve the geometric and mechanical properties of surface such as (1) dimensional accuracy, (2) surface roughness, (3) bearing ratio, (4) surface hardness, (5) wear resistance, (6) fatigue and corrosion resistance, etc. Therefore, this study carried out some experiments to illustrate the theoretical formula and to investigate surface accuracy (e.g. variation of diameter, surface roughness, bearing ratio) in accordance with the applied burnishing load.