• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.141-155
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• 2023

Monitoring technology based on electrical resistivity is widely used for non-destructive data collection and health analysis of underground structures and tunnels. Vulnerable sections such as fault zone generates many problems during construction of the tunnel. These problems cause displacement and stress changes of the ground. Therefore, it is necessary to predict the state of the fault zone section to ensure the mechanical stability of the underground structure. Monitoring the size of joints and the porosity of the fillings is essential for rocks. Previous studies have not considered the variety of fillings in rock joints. In this study, electrical resistivity tests were conducted according to the particle mixing state of the sandy fillings. When the size of fillings is decreased at the constant porosity, the electrical resistivity tends to increase. The results of this study are expected to be useful as basic electrical resistivity data for predicting the ground conditions and evaluation of the ground behavior that is containing sandy fillings in the rock joint for tunnels.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2002.05b
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• pp.289-295
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• 2002

Crab shell 충진 칼럼을 이용한 수중 중금속의 연속적 제거에 있어서 여러 중금속 ($Pb^{2+}$ , $Cd^{2+}$ , $Cu^{2+}$ , $Cr^{3+}$ )의 제거능 비교와 중금속 제거 전후의 crab shell의 표면 변화를 관찰해 보았다. Crab shell 충진 칼럼의 중금속 제거능을 알아보기 위해, 가장 변화가 많은 1,000 BVs까지의 crab shell g 당 각각 중금속의 제거량을 비교해 보면 $Pb^{2+}$(0.61 mmol/g) > $Cu^{2+}$(0.43 mmol/g) > $Cd^{2+}$(0.38 mmol/g) > $Cr^{3+}$(0.30 mmol/g) 순으로 나타났다. $Cd^{2+}$의 경우는 미세 침전보다는 내부의 화학적 침전이나 물리적 침전에 의한 제거가 더 많이 일어나고 $Pb^{2+}$의 경우는 유출되는 미세 침전량이 전체 제거량 중 26.6 %를 차지 하고 칼럼내 crab shell 표면에서도 다른 중금속들보다 월등히 많은 미세 침전물이 관찰 됨으로 $Pb^{2+}$의 경우는 중금속 제거는 화학적 침전이나 물리적 침전에 따른 미세침전에 의해 많이 이루어지고 있는 것으로 판단된다. $Cu^{2+}$와 $Cr^{3+}$의 경우, 중금속의 고유 색깔인 청색이 중금슥 제거가 끝난 후 crab shell 표면에 착색된 것을 관찰할 수 있었다. Crab shell 충진 칼럼을 이용한 수중 중금속 제거 후 중금속을 고농도로 수거하기 위한 탈착에 있어서는 초기 20 BVs 내에서 대부분의 중금속이 탈착되어 유출되는 것을 관찰 할 수 있었다.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.829-834
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• 1995

Homogeneously dispersed zirconia suspension was prepared by addition of 500ppm polyvinyl alcohol (PVA). The powder compact by centrifugal casting from this suspension shows more uniform packing, higher packing density, and smaller pore size than that of suspension without PVA. On using this powder compacts, sintered monocllnic zirconia with the relative density of 98% could be obtained at low temperature of 125$0^{\circ}C$.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.848-851
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• 1999

In order to increase the stability of Ginkgo Biloba extract, we investigated the effect of three different fill formulations(SBO, PEG400, and PEG600 fill types) on the stability of Ginkgo Biloba extract in three different shell formulations (ssmb, smb and gmb shell types). The stabilities of each types were evaluated by testing their disintegration time sunder the condition of $40^{\circ}C$, 75% relative humidity(RH) for 8 weeks. The formulation of Ginkgo Biloba extract with ssmb and PEG600 formulation type showed the best stability among them.

• Journal of Ocean Engineering and Technology
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• v.2 no.2
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• pp.130-137
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• 1988

This thesis introduced that character of a treatment technique for a mading synthetic resin Hifiow-Ring. The material system of packings make an experiment air$NH_{3}$/air$H_{2}SO_{4}$, $SO_{2}$-air/NaOH, $NH_{3}$-air/$/H_{2}SO_{4}$ under general conditions. Lattices packing compared with conventional packings was proved low pressure loss and high separation efficiency for high loading per trans unit. And an inflow materal tested for absorption and rectification, it made an experiment under a range regular temperature, low energy and small amount of money. That made possible in simple equation, volume material tranfer coefficient$\beta_{L}$ . a by absorption or $\beta_{V}$ .a calculated in all range loading. The peculiarity pressure loss $\Delta\;P/NUT_{ov}$ for Hiflow-ring contributed to a fall cost of energy, a grade number of a vacuum rectification and absorption calculation.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.4 s.19
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• pp.29-36
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• 2005

In this study, relations among unconfined compressive strength, strain at maximum strength and depth were compared with each other. Test specimen is marine clay originated from the place near Ga-duck island in Busan city. In addition, influence of impure material contained in specimen and that of total core recovery(TCR) on unconfined compressive strength and degree of disturbance were investigated. As a result of tests, unconfined compressive strength decreases as strain corresponding to maximum strength increases. Also, the deeper the sampling depth and the bigger the TCR, the unconfined compressive strength increases. Especially, as the TCR increases, the unconfined compressive strength Increases and quality of specimen is enhanced.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.4
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• pp.141-147
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• 2018

Solar energy has attracted big attentions as one of clean and unlimited renewable energy. Solar energy is transformed to electrical energy by solar cells which are comprised of multi-silicon wafer or mono-silicon wafer. Monosilicon wafers are fabricated from the Czochralski method. In order to decrease fabrication cost, increasing a poly-silicon charge size in one quartz crucible has been developed very much. When we increase a charge size, the temperature control of a Czochralski equipment becomes more difficult due to a strong melt convection. In this study, we simulated a Czochralski equipment temperature at 20 inch and 24 inch in quartz crucible diameter and various charge sizes (90 kg, 120 kg, 150 kg, 200 kg, 250 kg). The simulated temperature profiles are compared with real temperature profiles and analyzed. It turns out that the simulated temperature profiles and real temperature profiles are in good agreement. We can use a simulated profile for the optimization of real temperature profile in the case of increasing charge sizes.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.217-222
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• 2015

There has been increased amount of atmospheric pollutants including NOx and SOx which cause acid rain and photochemical smog as a result of increased use of fossil fuels. In order to reduce the amount of pollutants produced by fossil fuel, wet scrubber system is introduced in this experiment. Wet scrubber system is applied to a diesel engine (3,298 cc) and the amount of smoke is measured before and after the application in terms of aspect ratio, filling rate, and flow rate. The result showed a lot of smoke reduction when wet scrubber system was applied, and also the aspect ratios and water spray flow rate were the important factors to improve smoke reduction.

• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.422-426
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• 2005

Visible-light activated polymer nanocomposites (PNC) were designed to be used for dental restoration. Hybrid-filler composed of barium silicate and nano-sized silica was adopted as a filler system. To improve the interfacial be havior of the resin matrix of bisphenol A glycerolate methacrylate/triethyleneglycol dimethacrylate, the surface of filler was hydrophobically treated with a silane coupling agent. Mechanical properties of PNC were investigated by measuring the abrasion resistance, and it was discovered that PNC showed excellent properties with an increase of nanofiller content. However, the polymerization shrinkage was consistently maintained under 3 vol% and the shrinkage continued even after photo-polymerization. In addition, a slight color difference between PNC specimens was observed with increase of nanofiller content.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.115-120
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• 2018

This study examined the cast quality of small-sized induction motor rotors during the die casting process. Numerical analyses with 3-dimensional half models were performed to investigate the filling patterns of aluminum molten metals into a mold after high-speed injections. The following were obtained from numerical analyses and experimental results. First, molten metals started to fill the lower end ring, then moved horizontally to fill the core slot and upper end ring, and finally stopped to fill the rotor core slot. Second, circulation of molten metals occurred at the lower end ring, resulting considerable porosity at the section of lower end ring from the experimental results. Third, further work for obtaining sound quality of rotor core cast is required to develop a new shape of the rotor core cast or improve the die casting conditions.