• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.3
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• pp.25-36
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• 2000

The purpose of this research work is to propose an analytical method of tunnel design based on reasonable site data. Therefore the proposed design method consists of monitoring data and Modified In Situ Rock Model. Also the Rock Mass Rating for very poor quality rock is very difficult to estimate, the balances between the ratings may no longer gives a reliable basis for the rock mass strength. But in reality Rock Mass Rating is only the property which can be obtained from face mapping records of the exposed tunnel face during construction stage. Evaluation of rock parameters for the actual design prior to tunnel construction should be corrected during tunnelling process in particularly complex ground conditions. This study intends to investigate application of in-situ rock model to soft rock tunnelling (weathered rock) by face mapping results and site measurement data that are obtained at the costraction site of Seoul Subway Tunnel. For the preparation of more reliable ground parameters, the Rock Mass Rating values for the weathered rocks were modified and readjusted in accordance with the measurement data. The modified input parameters obtained by the proposed method are used for the prediction of the tunnel behavior at subsequent construction stages. The results of this study revealed that more reasonable feed back tunnel analysis can be possible as suggested. Ample measurement data would be able to confirm the new proposed technique in this research work.

• Journal of Pharmaceutical Investigation
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• v.36 no.3
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• pp.185-192
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• 2006

The purpose of this study was to determine the effects of iontophoresis on transdermal delivery of procaine hydrochloride in healthy volunteers, as well as to the synergic effect of high voltage current or ultrasound on the efficacy of transdermal delivery of iontophoresis. Forty healthy volunteers were randomly assigned to four groups topical application group (TA), iontophoresis group (IT), pre-treatment of high voltage current stimulation with iontophoresis (HVS + IT), and pre-treatment of ultrasound application with iontophoresis (US + IT). All subjects received procaine iontophoresis on the forearm using direct current with 4 mA f3r 15 minutes. All subject was measured the duration of local anesthesia, pressure pain threshold, pain perception threshold using rectangular wave at 0.2 ms, 1 ms, 50 ms of rectangular current stimulation after procaine iontophoresis. For comparisons of the sensory characteristics and efficacy of iontophoresis between the groups, an one-way ANOVA and Kruskal-Wallis were used. The significant difference the duration of local anesthesia were found between the groups (p<0.001). The local anesthetic duration of IT, HVS+IT were significantly longer than TA. Meanwhile, the local anesthetic duration of US+IT was significantly longer than HVS+IT, IT and TA group (p<0.05). Also, the pressure pain threshold, pain perception threshold at 0.2 ms, 1 ms, 50 ms were significant difference between the groups (p<0.001). All sensory characteristics including pressure pain threshold, pain perception threshold of IT, HVS+IT was significantly increased than TA, whereas, US+1T was significantly increased HVS+1T, IT and TA (p<0.05). This study showed that the procaine iontophoresis have increase the duration of local anesthesia concomitantly pressure pain threshold and pain perception threshold of sensory nerve fibers such as $A-{\beta}$, $A-{\delta}$ and C fiber. This findings suggest that the iontophoresis enhanced the transdermal delivery of drug ions in vivo. The combination of ultrasound application and iontophoresis synergized the transdermal delivery of drug ions. It is suggests that an electric field, mechanical and heating property of ultrasound may contribute to synergic effect due to temporary changes of structure in the stratum corneum.

• The Korean Journal of Pesticide Science
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• v.9 no.2
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• pp.140-145
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• 2005

Quantitative Structure Activity Relationship (QSAR) assumes the relatedness between physical property and biological activity. However, activity data measured at single concentration such as percent activity have not been used extensively for modeling purpose. This probably comes from the fact that these values are qualitative instead of quantitative. To utilize percent activity data for molecular modeling, we classified the whole data into two classes. One class represents the active while the other signifies the inactive. The percent activity data of ${\beta}$-Ketoacetoanilides measured for TLB (Tomato Late Blight) were investigated. CoMFA (Comparative Molecular Field Analysis) was used as a discriminant function. Using CoMFA provides 3D (three dimensional) information, which is crucial for chemical insight. It can also serve as a predictive model. The resultant model classified the given data correctly (98%). When LOO (leave-one-out) crossvalidation procedure was applied, the classification accuracy was 69%. Therefore two class approximation of percent activity data with CoMFA can be utilized to understand the relationship between chemical structure and biological activity and design subsequent chemical analogs.

• Elastomers and Composites
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• v.36 no.1
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• pp.44-51
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• 2001

To see the effect of chemical surface modification, the carbon black surfaces were treated with three types of chemicals (KOH, $H_3PO_4$, and benzene). Vulcanization and mechanical properties of a styrene-butadiene rubber (SBR) were investigated depending on the chemical treatments. The surface free energy increased considerably with the treatments by both the acid (HCB) and base (KCB), but only a slight increase was observed for benzene treatment(BCB). The BCB showed the highest level of the London dispersive component. The vulcanization reaction was found to be faster in the order of KCB-SBR> BCB-SBR> VCB-SBR(virgin) > HCB-SBR. The difference in minimum and maximum torque of rheocurve, representing the degree of crosslinking, was found to be higher for the BCB-SBR compared to those of VCB-SBR, KCB-SBR, and HCB-SBR. The BCB-SBR and KCB-SBR showed the improved tensile and dynamic mechanical properties. A linear relationship was found to exist between the London dispersive component of surface free energy and mechanical properties.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.288-293
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• 2011

We investigated the effects of piezoelectric field on the electro-absorption characteristics in InGaN/GaN multiple-quantum well (MQW) green light emitting diodes (LED). Double crystal X-ray diffraction measurement was performed to study the crystalline property and indium (In) composition in the MQW active layer. To measure the electro-luminescence and electro-reflectance (ER) spectroscopy, we fabricated the $1{\times}1\;mm^2$ large-area green LED chip. The piezoelectric field inside the LED structure was evaluated from the Vcomp in active layer by the ER spectra. Finally, we analyzed the electro-absorption characteristics of the green LED by using the photo-current spectroscopy.

• Membrane Journal
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• v.26 no.4
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• pp.239-252
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• 2016

Two-dimensional materials offer unique characteristics for membrane applications to water technology. With its atomic thickness, availability and stackability, graphene in particular is attracting attention in the research and industrial communities. Here, we present a brief overview of the recent research activities in this rising topic with bringing two membrane architecture into focus. Pristine graphene in single- and polycrystallinity poses a unique diffusion barrier property for most of chemical species at broad ambient conditions. If well designed and controlled, physical and chemical perforation can turn this barrier layer to a thinnest feasible membrane that permits ultimate permeation at given pore sizes. For subcontinuum pores, both molecular dynamics simulations and experiments predict potential salt rejection to envisage a seawater desalination application. Another novel membrane architecture is a stack of individual layers of 2D materials. When graphene-based platelets are chemically modified and stacked, the interplanar spacing forms a narrow transport pathway capable of separation of solvated ions from pure water. Bearing unbeknownst permeance and selectivity, both membrane architecture - ultrathin porous graphene and stacked platelets - offer a promising prospect for new extraordinary membranes for water technology applications.

• Journal of the Korean Electrochemical Society
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• v.19 no.1
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• pp.21-27
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• 2016

Vanadium redox flow batteries (VRFBs) using the electrolytes containing various vanadium ions in sulfuric acid as supporting solution are one of the energy storage devices in alternatively charging and discharging operation modes. The positive electrolyte contains $V^{5+}/V^{4+}$ and the negative electrolyte $V^{2+}/V^{3+}$ depending on the operation mode. To prevent the mixing of two solutions, proton exchange membranes are mainly used in VRFBs. Nafion 117 could be the most promising candidate due to the strong oxidative property of $V^{5+}$ ion, but causes high crossover of electroactive species to result in a decrease in coulombic efficiency. In this study, the composite membranes using Nafion ionomer and porous polyethylene substrate were prepared to keep good chemical stability and to decrease the cost of membranes, and were compared to the properties and performance of the commercially available electrolyte membrane, Nafion 117. As a result, the water uptake and ionic conductivity of the composite membranes increased as the thickness of the composite membranes increased, but those of Nafion 117 slightly decreased. The permeability of vanadium ions for the composite membranes significantly decreased compared to that for Nafion 117. In a single cell test for the composite membranes, the voltage efficiency decreased and the coulombic efficiency increased, finally resulting in the similar energy efficiency. In conclusion, the less cost of the composite membranes by decreasing 6.4 wt.% of the amount of perfluorinated sulfonic acid polymer due to the introduction of porous substrate and lower vanadium ion permeability to decrease self-discharge were achieved than Nafion 117.

• Geomechanics and Engineering
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• v.19 no.5
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• pp.421-434
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• 2019

It is of great significance to study the mechanical properties and failure mechanism of the defected rock for geological engineering. The defected sandstone modeling with power-law distribution of pre-cracks was built in this paper by Particle Flow Code software. Then the mechanical properties of sandstone and the corresponding failure process were meticulously analyzed by changing the power-law index (PLI) and the number of pre-cracks (NPC). The results show that (1) With the increase of the PLI, the proportion of prefabricated long cracks gradually decreases. (2) When the NPC is the same, the uniaxial compressive strength (UCS) of sandstone increases with the PLI; while when the PLI is the same, the UCS decreases with the NPC. (3) The damage model of rock strength is established based on the Mori-Tanaka method, which can be used to better describe the strength evolution of damaged rock. (4) The failure mode of the specimen is closely related to the total length of the pre-crack. As the total length of the pre-crack increases, the failure intensity of the specimen gradually becomes weaker. In addition, for the specimens with the total pre-crack length between 0.2-0.55 m, significant lateral expansion occurred during their failure process. (5) For the specimens with smaller PLI in the pre-peak loading process, the concentration of the force field inside is more serious than that of the specimens with larger PLI.

• Geophysics and Geophysical Exploration
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• v.4 no.4
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• pp.124-132
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• 2001

Electrical resistivity survey has been conducted for delineating geological fault structure in Kaekok-ri near Kyungju. In general, electrical resistivity survey has an advantage of searching buried faults and its traces compared with other geophysical survey methods. Distribution of electrical conductivity in the ground is influenced by the ratio of pores, groundwater and clay minerals. These properties are evidenced indirectly to explain for weathering condition, faults and fracture Bones. Thus the electrical resistivity survey can be an effective method to find buried faults. We have carried out two dimensional (2-D) interpretation by means of smoothness-constrained least-squares and finite element method. Field data used in this paper was acquired at Kaekok-ri, Wuedong-eup, Kyungju-si, where is Ulsan Fault and is close to the region in which debatable quaternary fault traces were found recently. The dipole-dipole array resistivity survey which could show the 2-D subsurface electrical resistivity structure, was carried out in the area with three lines. The results showed good property of fault, fracture zone and fault traces which we estimated were congruous with the results. Through this study, 2-D electrical resistivity survey interpretation for fault is useful to apply.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.288-289
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• 2000

SBN, BSKNN KNSBN 등의 tungsten-bronze 계열에 속하는 광굴절 결정은 짧은 파장에서 좋은 감광도와 빠른 응답시간을 갖는다. 이중에서도 KNSBN 결정은 큰 크기의 결정 성장 및 도핑이 용이하고 광굴절 결정에서 중요한 특성 중 하나인 열 안정성(thermal stability)이 좋기 때문에 빠른 응답특성이 요구되는 응용분야에서 촉망받는 매질이다. 본 논문에서는 광정보저장, 광정보처리, 광컴퓨터, 광통신과 같은 다양한 분야에서 응용가능성을 가지는 Cu가 0.04wt.%도핑된 5mm$\times$5mm$\times$5mm 크기의 KNSBN 결정을 이용한 광신호의 증폭기술에 대하여 연구하였다. 먼저 Cu-KNSNB 결정의 2광파 결합 특성을 분석하기 위하여, 기록 파장에 따른 지수이득계수의 외부입사각의존성, 최대 지수이득계수를 나타내는 외부입사각에서 입사빔의 세기비에 따른 2광파 결합 이득을 측정하였다. 또한, 632.8nm파장 영역에서 기록 및 삭제시간 상수, 회절 효율의 입사빔 세기비 의존성을 측정하였다. 그리고, 음향-광학 변조기(AOM: acousto-optic modulator)에 의해 진폭 변조된 신호빔을 이용하여 광신호 증폭특성을 분석하고 그 결과를 제시하였다. 이때 두 빔의 입사각은 최대 지수이득계수를 나타내는 입사반각 12$^{\circ}$로 고정하고, 감쇄기를 이용하여 신호빔의 세기를 조절하면서 신호빔의 차동이득을 측정하였다. 투과된 신호빔은 같은 주파수에서 차동 이득(diffrerential gain)을 보였으며, 이는 moving grating과 시간-변조된 신호빔(또는 펌프빔)사이의 새로운 상호작용은 광굴절 결정의 시간 적분 특성에 의한 것이다. (중략) 경우는 상온에서 펌프 펄스의 유지시간이 0.5% 인 경우 레이저가 동작하는 것을 보여주었다. 이는 구조내에서 열전도가 문제가 된다는 것을 의미하는데 위아래가 공기로 둘러 싸여 있어 발생한 열이 가는 유전체 네트웍을 통해서만 전달 될 수 있기 때문이다. (중략)$^4$A$_2$에 의한 nophonon line R$_1$, R$_2$(680.4, 678.5 nm) 및 $^2$T$_1$$\longrightarrow$$^4$A$_2$(655.7, 649.3, 645.2 nm)의 형광방출 스펙트럼을 얻었으며, 형광수명은 0.264 ms로 조사되었다. 제조된 레이저 발진봉은 직경 6.3 m, 길이 45 nm이었다.\pm$0.06kHz Ge $F_4$; -1.84$\pm$0.04kHz$0.04kHz/TEX>0.04kHz 모국어 및 관련 외국어의 음운규칙만 알면 어느 학습대상 외국어에라도 적용할 수 있는 보편성을 지니는 것으로 사료된다.없다. 그렇다면 겹의문사를 [-wh]의리를 지 닌 의문사의 병렬로 분석할 수 없다. 예를 들어 누구누구를 [주구-이-ν가] [누구누구-이- ν가]로부터 생성되었다고 볼 수 없다. 그러므로 [-wh] 겹의문사는 복수 의미를 지닐 수 없 다. 그러면 단수 의미는 어떻게 생성되는가\ulcorner 본 논문에서는 표면적 형태에도 불구하고 [-wh]의미의 겹의문사는 병렬적 관계의 합성어가 아니라 내부구조를 지니지 않은 단순한 단어(minimal $X^{0}$ elements)로 가정한다.