• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.323-345
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• 2019

It is essential to predict ground conditions ahead of a tunnel face in order to successfully excavate tunnels using a shield TBM. This study proposes a forward prediction method for a mixed soil ground and/or a ground containing core stones by using electrical resistivity and induced polarization exploration. Soil conditioning in EPB shield TBM is dependent upon the composition of mixed soils; a special care need to be taken when excavating the core-stoned soil ground using TBM. The resistivity and chargeability are assumed to be measured with four electrodes at the tunnel face, whenever the excavation is stopped to assemble one ring of a segment lining. Firstly, the mixed ground consisting of weathered granite soil, sand, and clay was modeled in laboratory-scale experiments. Experimental results show that the measured electrical resistivity considerably coincides with the analytical solution. On the other hand, the induced polarization has either same or opposite trend with the measured resistivity depending on the mixed ground conditions. Based on these experimental results, a method to predict the mixed soil ground that can be used during TBM tunnel driving is suggested. Secondly, tunnel excavation from a homogeneous ground to a ground containing core stones was modeled in laboratory scale; the irregularity of the core stones contained in the soil layer was modeled through random number generation scheme. Experimental results show that as the TBM approaches the ground that contains core stones, the electrical resistivity increases and the induced polarization fluctuates.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.301-328
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• 2006

The geology of the Tumbang Mirih area in the Middle Kalimantan, Indonesia comprises Permian to Carboniferous Pinoh Metamorphic Rocks and Cretaceous Sepauk Plutonics of the Sunda Shield, late Eocene Tanjung Formation, Oligocene Malasan Volcanics, Oligocene to early Miocene Sintang Intrusives and Quaternary alluvium. Results of geochemical exploration and geological mapping exposed obviously that large amounts of gold-bearing quartz veins were found in the whole Tumbang Mirih areas. In many places, gold grains were megascopically detectable from panning products of stream sediments and conglomerate as Quaternary sediments. Even though no remnants of quartz veins are revealed in the most of survey area except Taran region, association of fold grains with layers of quartz pebbles and clays which correspond to the horizon of unconformity or previous river bottom indicates that the gold grains were separated from quartz veins. Along rivers often pebbles and clay layers just over or 10 to 20cm above the current waterlevel are recognized. The occurrence of gold in the conglomeratic layer was frequently confirmed during geochemical exploration. Since the conglomeratic layer was old stream sediments of Quaternary, it can be assumed that deposition of golds was controlled by shape of river floor, speed and shape of river flow, and distance from the source rock. Taran area and northern Takaoi area based on the all data are recommended as the promising areas.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.3
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• pp.234-240
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• 2015

In the face of the world's growing energy storage needs, liquid hydrogen offers a high energy density solution for the storage and transport of energy throughout society. A 5 L liquid hydrogen storage tank has been designed, fabricated and tested to investigate boil-off rate of liquid hydrogen. As the insulation plays a key role on the cryogenic vessels, various insulation methods have been employed. To reduce heat conduction loss, the epoxy resin-based insulation supports G-10 were used. To minimize radiation heat loss, vapor cooled radiation shield, multi-layer insulation, and high vacuum were adopted. Mass flow meter was used to measure boil-off rate of the 5 L cryogenic vessel. A series of performance tests were done for liquid nitrogen and liquid hydrogen to compare with design parameters, resulting in the boil-off rate of 1.7%/day for liquid nitrogen and 16.8%/day for liquid hydrogen at maximum.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.3
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• pp.194-198
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• 2010

Recently as the electronic devices are getting to be more and more smaller, transformers are needed to be micro fabricated using MEMS technology. In this paper transformers have been fabricated and measured by depositing insulation layer to reduce the loss of eddy current and in the middle core a high permeability permalloy was designed based on the turns ratio between primary coil and secondary coil which are 1:1 transformers. (the number of turns of primary coil and secondary coil: 3/3, 5/5, 7/7). The size of the transformers including ground shield are $1mm{\times}1.5mm$, $1mm{\times}1.95mm$, $1mm{\times}2.35mm$ respectively. The line width, pitch and the height of post are 50um. Based on the measured data from the micro fabricated transformers, the 3/3 turns in the primary coil and secondary coil showed the lowest insertion loss with 1.5 dB at 480 MHz and the 7/7 turns in the primary coil and secondary coil showed the highest insertion loss with 2.5 dB at 280 MHz. Also confirmed that the bandwidth goes up as the number of turns goes down. There was some difference between the actual measured data and the HFSS simulation result. It looks as if it is an error of the difference between oxidation of copper or the permeability of SU-8.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1964-1969
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• 2010

Recently, as construction market scale is getting bigger and transportation industry is developing, the underground structure construction such as subway, tunnel (excavation box) or shield tunnel structure is becoming more diverse, and its demand is gradually increasing. However, for the concrete structures constructed underground, the water leakage is occurred due to the expansion joint and construction joint, or movement, uneven settlement, excessive load and vibration during application causing cracks. Many waterproofing method and materials are used in jobsites, but areas such as underground railroad and subway that has movement and vibration at all times, the ability of waterproofing layer is declined causing repetitive water leakage due to crack, erosion and separation, which is a vicious cycle. Therefore, this study evaluates the responsiveness to a movement for adhesive/flexible waterproofing material that can cope with the vibration and the movement of the structure. Also to recommend a waterproofing technology that can cope with structure movement through examples of actual jobsite applications such as subway and tunnel where there are constant movement and vibration.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.15-20
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• 2015

To examine the magnetic shielding effect for carbon-based materials at extremely low frequencies (60 Hz), two types of carbon black (Super-P and Denka Black) and a natural graphite (HC-198) were mixed into organic binder at 10 wt.% to produce a coating solution, and a powder coating with varying thickness was applied on an aluminum disk measuring 88 mm in radius. A device was developed to measure the sheielding effect at extremely low frequencies. A closed circuit was achieved by connecting a transformer and a resistor. The applied voltage was fixed at 65 V, and the magnetic field was measured to being the range of 4.95~5.10 mG. Depending on the thickness of the coating layer, the magnetic field showed a decreasing trend. The maximum decrease in the magnetic field of 38.3% was measured when natural graphite was coated with specimens averaging $455{\mu}m$. This study confirmed that carbon-based materials enable magnetic shielding at extremely low frequencies, and that the magnetic shielding effect can be enhanced by varying the coating thickness.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2019.05a
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• pp.69-69
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• 2019

The distillation of liquid cathode is necessary to separate cadmium from the actinide elements in the pyroprocessing since the actinide deposits are dissolved or precipitated in a liquid cathode. It is very important to avoid a splattering of cadmium during evaporation due to the high vapor pressure. Several methods have been proposed to lower the splattering of cadmium during distillation. One of the important methods is an installation of crucible cover on the distillation crucible. A multi-layer porous round cover was proposed to avoid a cadmium splattering in our previous study. In this study, the effect of crucible cover on the cadmium distillation was examined to develop a splatter shield. Various surrogates were used for the actinides in the cadmium. The surrogates such as bismuth, zirconia, and tungsten don't evaporate at the operational temperature of the Cd distiller due to their low vapor pressures. The distillation experiments were carried out in a crucible equipped with cover and in a crucible without cover. About 40 grams of Cd was distilled at a reduced pressure for two hours at various temperatures. The mixture of the cadmium and the surrogate was heated at $470{\sim}620^{\circ}C$. Most of the bismuth remained in the crucible equipped with cover after distillation under $580^{\circ}C$ for two hours, whereas small amount of bismuth decreased in the crucible without cover above $580^{\circ}C$. The liquid bismuth escaped with liquid cadmium drop from the crucible without cover. It seems that the crucible cover played a role to prevent the splash of the liquid cadmium drop. The effect of the cover was not clear for the tungsten or zirconia surrogate since the surrogates remained as a solid powder at the experimental temperature. From the results of this work, it can be concluded that the crucible cover can be used to minimize the deposit loss by prevention of escape of liquid drop from the crucible during distillation of liquid cathode.

• Nuclear Engineering and Technology
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• v.51 no.6
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• pp.1633-1637
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• 2019

While considering the photon attenuation coefficient (${\mu}$) and its related parameters for photons shielding, it is necessary to account for its transmitted and reflected photons energy spectra and dose contribution. Monte Carlo simulation was used to study the efficiency of clay ($1.99g\;cm^{-3}$) as a shielding material below 150 keV photon. Am-241 gamma source and an X-ray of 150 kVp were calculated. The calculated value of ${\mu}$ for Am-241 is higher within 5.61% compared to theoretical value for a single-energy photon. The calculated half-value layer (HVL) is 0.9335 cm, which is lower than that of ordinary concrete for X-ray of 150 kVp. A thickness of 2 cm clay was adequate to attenuate 90% and 85% of the incident photons from Am-241 and X-ray of 150 kVp, respectively. The same thickness of 2 cm could shield the gamma source dose rate of Am-241 (1 MBq) down to $0.0528{\mu}Sv/hr$. For X-ray of 150 kVp, photons below 60 keV were significantly decreased with 2 cm clay and a dose rate reduction by ~80%. The contribution of reflected photons and dose from the clay is negligible for both sources.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.6
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• pp.603-608
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• 2023

Carbon black with high purity and excellent conductivity is used as a conductive filler in the semiconductive compound for EHV (Extra High Voltage) power cables of 345 kV or higher. When carbon black and CNT (carbon nanotube) are applied together as a conductive filler of a semiconductive compound, stable electrical properties of the semiconductive compound can be maintained even though the amount of conductive filler is significantly reduced. In EHV power cables, since the semi-conductive layer is close to the conductor, stable electrical characteristics are required even under high-temperature conditions caused by heat generated from the conductor. In this study, the theoretical principle that a semiconductive compound applied with carbon black and CNT can maintain excellent electrical properties even under high-temperature conditions was studied. Basically, the conductive fillers dispersed in the matrix form an electrical network. The base polymer and the matrix of the composite, expands by heat under high temperature conditions. Because of this, the electrical network connected by the conductive fillers is weakened. In particular, since the conductive filler has high thermal conductivity, the semiconductive compound causes more thermal expansion. Therefore, the effect of CNT as a conductive filler on the thermal conductivity, thermal expansion coefficient, and volume resistivity of the semiconductive compound was studied. From this result, thermal expansion and composition of the electrical network under high temperature conditions are explained.

• Journal of Sensor Science and Technology
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• v.33 no.1
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• pp.56-61
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• 2024

The quality of the display can be managed by effectively managing the temperature generated by the panel during use. Conventional display panels rely on an external reference resistor for temperature monitoring. However, this approach is easily affected by external factors such as temperature variations from the driving circuit and chips. These variations reduce reliability, causing complicated mounting owing to the external chip, and cannot monitor the individual pixel temperatures. However, this issue can be simply and efficiently addressed by integrating temperature sensors during the display panel manufacturing process. In this study, we fabricated and analyzed a temperature sensor integrated into an a-IGZO (amorphous indium-gallium-zinc-oxide) TFT array that was to precisely monitor temperature and prevent the deterioration of OLED display pixels. The temperature sensor was positioned on top of the oxide TFT. Simultaneously, it worked as a light shield layer, contributing to the reliability of the oxide. The characteristics of the array with integrated temperature sensors were measured and analyzed while adjusting the temperature in real-time. By integrating a temperature sensor into the TFT array, monitoring the temperature of the display became easier and more accurate. This study could contribute to managing the lifetime of the display.