• Journal of the Korean Geotechnical Society
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• v.32 no.3
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• pp.29-37
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• 2016

SSG (self-healing smart grouting) method, which is developed recently, has the characteristics such as an improvement of durability and waterproofing, prevention of leaching and pollution. In this study, we performed several tests such as gel-time measurement, uniaxial compression test, permeability test, fish poison test and chemical resistance test to compare the engineering properties of SSG with the other chemical grouting method (LW, SGR). As results of tests, the SSG method has low possibility of groundwater and ground pollution caused by leaching, furthermore, it has advantages like long/short term waterproofing, strength and durability. Therefore the SSG method can be applicable in the fields as an alternative of existing chemical grouting methods with problems.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.62-69
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• 2010

This paper presents the dependances of transient grounding impedances of counterpoises on the soil structures and the injected point of impulse currents. The transient and conventional grounding impedances of the 25 and 50[m] counterpoises buried in the soil with different resistivity were measured and analyzed as a function of the rise time of impulse currents. As a result, the transient grounding impedances give an inductive behavior, and the trend of the conventional grounding impedances is similar to that of the transient grounding impedances. The ground resistance of counterpoises is irrespective to the injected of impulse current, but the transient and conventional grounding impedances in a short time range especially depend on the soil resistivity and position of the injected point of impulse currents.

• Journal of the Korean Institute of Gas
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• v.8 no.3 s.24
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• pp.1-7
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• 2004

The polyethylene pipe can use semi-permanent because of the high corrosion resistance with chemical stability. In addition to, there is the merit that is an easy to establish and to maintain. However, as the reason that it is simply degraded when the polyethylene pipe was exposed to the outside, mainly it is used to lay under the ground with low-pressure gas transportation pipe. In this study, the nondestructive evaluation method was used to maintain the integrity of the polyethylene pipe. We simulated the various defects on the polyethylene pipes, and then the AE signal occurred according to the impact test of steel ball was evaluated by the acoustic emission method. From the results, the waveform and dominant frequency could be distinguishing from the defect shapes of polyethylene pipe. Especially, in the case of notch defect, the AE signals occur different by the angle and depth of the notch.

• Geomechanics and Engineering
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• v.10 no.5
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• pp.677-687
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• 2016

Industrialization and urbanization are the two phenomena that are going relentless all over the world. The consequence of this economic success has been a massive increase in waste on one hand and increasing demand for suitable sites for construction on the other. Owing to the surplus raw materials and energy requirement needed for manufacturing synthetic fibers, applications of waste fibers for reinforcing soils evidenced to offer economic and environmental benefits. The main objective of the proposed work is to explore the possibilities of improving the strength of soil using fly ash waste as an admixture and Human Hair Fiber (HHF) as reinforcement such that they can be used for construction of embankments and land reclamation projects. The effect of fiber content on soil - fly ash mixture was observed through a series of laboratory tests such as compaction tests, CBR and unconfined compression tests. From the stress - strain curves, it was observed that the UCC strength for the optimised soil - flyash mixture reinforced with 0.75% human hair fibers is nearly 2.85 times higher than that of the untreated soil. Further, it has been noticed that there is about 7.73 times increase in CBR for the reinforced soil compared to untreated soil. This drastic increase in strength may be due to the fact that HHF offer more pull-out resistance which makes the fibers act like a bridge to prevent further cracking and thereby it improves the toughness which in turn prevent the brittle failure of soil-flyash specimen. Hence, the test results reveal that the inclusion of randomly distributed HHF in soil significantly improves the engineering properties of soil and can be effectively utilized in pavements. SEM analysis explained the change of microstructures and the formation of hydration products that offered increase in strength and it was found to be in accordance with strength tests.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.132-136
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• 1996

A Study is a experiment which is figure out to aptimum discharge cutting condition of the surfaceroughness, electric discharging speed and electro wear ratio with Ton Toff and V(voltage) as an input condition according to the current(Ip) in an electric spark machine ; 1)Electrode is utilized Cu(coper) and Graphite. 2)Work piece is used the material of carbon steel. The condition of experiment is; 1)Current is varied 0.7(A) to 50(A). 2)Pulse time(Ton) is varied 3($\mu$s) to 240($\mu$s) and also Toff is varied 7($\mu$s) to 20($\mu$s). 3)The time of electric discharging to work piece in each time is 30(min) to 60(min) 4)After the upper side of work piece was measured in radius (5${\mu}{\textrm}{m}$) of syulus analyzed the surface roughness to made the table and graph of Rmax by yielding data. 5)Electro wear ratio is; \circled1Coper was measured cx-machining and post machining but the electronic baiance. \circled2The ex-machining of graphite measured by it, the post-machining was found the data from volume specific gravity and analyzed to made its table and graph on ground the data 6)In order to keep the accuracy of voltage affected to the work piece was equipped with the A.V.R(Automatic Voltage Regulator). 7)The memory scope was sticked to the electric spark machine. 8)In order to preserve the precision of current, to get rid of the noise occured by internal resistance of electric spark machine and to force injecting for the discharge fluid, it made the fixed table for a work piece to minimize the work error by means of one's failure during the electric discharging According to above results, the surface roughness by the variation of electrodw and current was analyzed to compare KS(Korea Standards) It was decided the optimum condition of electric discharge cutting through analyzing the effect of electric discharge speed and electro wear ratio.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.5
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• pp.197-209
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• 2020

Evidence of liquefaction during the 2017 Pohang earthquake has highlighted the urgent need to evaluate the current seismic design standard for liquefaction in Korea, particularly the liquefaction triggering standard. With the simplified method, which is the most popular method for evaluating liquefaction triggering, the factor of safety for liquefaction triggering is calculated via the cyclic stress ratio (CSR) and the cyclic resistance ratio (CRR). The parameters in the CSR and CRR have undergone changes over time based on new research findings and lessons learned from liquefaction case-histories. Hence, the current design standard for liquefaction triggering evaluation in Korea should also reflect these changes to achieve seismic safety during future earthquakes. In this study, liquefaction susceptibility criteria were discussed initially and this was followed by a review of the current liquefaction triggering codes/guidelines in other countries and Korea. Next, the parameters associated with the CSR such as the maximum ground acceleration, stress reduction factor, magnitude scaling factor, and overburden correction factor were discussed in detail. Then, the evaluation of the CRR using the SPT N-value and CPT qc-value was elaborated along with overburden and clean-sand correction factors. Based on this review of liquefaction triggering evaluation standards, recommendations are made for improving the current seismic design standard related to liquefaction triggering in Korea.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.247-254
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• 2003

While the interests in the environmental problem during the construction are increasing, the use of low noise-vibration auger-drilled pilling is increasing to solve noise and vibration problem in pilling. Therefore, in Korea, SIP (Soil-Cement Injected Precast Pile) method is mainly used as auger-drilled pilling. However, there is no proper design criteria compatible with the ground condition of Korea, so which is most wanted. To improve and supplement this situation, direct shear tests for the friction between SIP pile skin interface and soil were executed on various conditions. Through the analysis of test results, skin friction characteristics of SIP were investigated thoroughly Also, hyperbolic model parameter fomulas which describe the friction behavior and the new non-linear unit skin friction capacity model with SM, SC soil were suggested.

• Journal of the Korea Institute of Building Construction
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• v.15 no.4
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• pp.383-389
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• 2015

The objective of this study is to develop mixture proportioning approach of crack controlled lightweight foamed concrete without using high-pressure steam curing processes, as an alternative to autoclaved lightweight concrete blocks (class 0.6 specified in KS). To control thermal cracks owing to hydration heat of cementitious materials, 30% ground granulated blast-furnace slag (GGBS) was used as a partial replacement of ordinary portland cement (OPC). Furthermore, polyvinyl alcohol (PVA) and polyamid (PA) fibers were added to improve the crack resistance of foamed concrete. The use of 30% GGBS reduced the peak value of hydration production rate measured from isothermal tests by 28% and the peak temperature of foamed concrete measured from semi-adiabatic hydration tests by 9%. Considering the compressive strength development, internal void structure, and flexural strength of the lightweight foamed concrete, the optimum addition amount of PVA or PA fibers could be recommended to be $0.6kg/m^3$, although PA fiber slightly preferred to PVA fiber in enhancing the flexural strength of foamed concrete.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.549-555
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• 2012

Silicon carbide(SiC) exhibits many unique properties, such as high strength, corrosion resistance, and high temperature stability. In this study, a SiC-fiber web was prepared from polycarbosilane(PCS) solution by employing the electrospinning process. Then, the SiC-fiber web was pyrolyzed at $1800^{\circ}C$ in argon atmosphere after it was subjected to a thermal curing. The SiC-fiber web (ground web)/phenolic resin (resol) composite was fabricated by hot pressing after mixing the SiC-fiber web and the phenolic resin. The SiC-fiber web composition was controlled by changing the fraction of filler (filler/binder = 9:1, 8:2, 7:3, 6:4, 5:5). Thermal conductivity measurement indicates that at the filler content of 60%, the thermal conductivity was highest, at 6.6 W/mK, due to the resulting structure formed by the filler and binder being closed-packed. Finally, the microstructure of the composites of SiC-fiber web/resin was investigated by FE-SEM, EDS, and XRD.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.2
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• pp.189-194
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• 2018

Nowadays most integrated circuits are built using the bulk CMOS technology, but it has much difficulty in further reduction of the power consumption and die size. As a super low-power technology to solve such problems, the SOI technology attracts great attention recently. In this paper, the study results of the temperature dependency of the hot carrier effects in the n-channel MOSFETs fabricated on the thin SOI substrate were discussed. In spite that the devices employed the LDD structure, the hot carrier effects were more serious than expected due to the high series resistance between the channel region and the substrate contact to the ground, and were found to be less serious for the higher temperature with the more phonon scattering in the channel region, which resulted in reducing the hot electron generation.