• Geophysics and Geophysical Exploration
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• v.19 no.2
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• pp.59-66
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• 2016

The electrical resistivity method is an effective geophysical tool to detect subsurface contamination because the contaminated zones show generally lower electrical resistivity. In this study, the electrical resistivity surveys were applied to a waste landfill site to image the subsurface structure around the landfill and to identify the contaminated zones. First, the dipole-dipole 2D resistivity surveys were conducted along the boundaries of landfill to define the developed contaminated zones. Then the crosshole resistivity tomography was applied to confirm the suspected contaminated zones at depth. The results of drilling and geochemical analysis of ground water supported that the low resistivity zones coincide well with the contaminated zones and the leachate pathways could be delineated effectively from the resistivity survey.

• Advances in biomechanics and applications
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• v.1 no.2
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• pp.127-141
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• 2014

A preliminary study of a new pulsatile pump that will work to a frequency greater than 1 Hz, is presented. The fluid-structure interaction between a Newtonian blood flow and a piston drive that moves with periodic speed is simulated. The mechanism is of double effect and has four valves, two at the input flow and two at the output flow; the valves are simulated with specified velocity of closing and reopening. The simulation is made with finite elements software named COMSOL Multiphysics 3.3 to resolve the flow in a preliminary planar configuration. The geometry is 2D to determine areas of high speeds and high shear stresses that can cause hemolysis and platelet aggregation. The opening and closing valves are modelled by solid structure interacting with flow, the rhythmic opening and closing are synchronized with the piston harmonic movement. The boundary conditions at the input and output areas are only normal traction with reference pressure. On the other hand, the fluid structure interactions are manifested due to the non-slip boundary conditions over the piston moving surfaces, moving valve contours and fix pump walls. The non-physiologic frequency pulsatile pump, from the viewpoint of fluid flow analysis, is predicted feasible and with characteristic of low hemolysis and low thrombogenesis, because the stress tension and resident time are smaller than the limit and the vortices are destroyed for the periodic flow.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.6
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• pp.473-479
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• 2011

In this paper, we have compared amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) with the nano-crystalline embedded-IGZO ($N_c$-embedded-IGZO) TFT fabricated by solid-phase crystallization (SPC) technique. The field effect mobility (${\mu}_{FE}$) of $N_c$-embedded-IGZO TFT was 2.37 $cm^2/Vs$ and the subthreshold slope (S-factor) was 0.83 V/decade, which showed lower performance than those of a-IGZO TFT (${\mu}_{FE}$ of a-IGZO was 9.67 $cm^2/Vs$ and S-factor was 0.19 V/decade). This results originated from generation of oxygen vacancies in oxide semiconductor and interface between gate insulator and semiconductor due to high temperature annealing process. However, the threshold voltage shift (${\Delta}V_{TH}$) of $N_c$-embedded-IGZO TFT was 0.5 V, which showed 1 V less shift than that of a-IGZO TFT under constant current stress during $10^5$ s. This was because there were additionally less increase of interface trap charges in Nc-embedded-IGZO TFT than a-IGZO TFT.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.181-181
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• 2013

최근에 형광체 결정 입자의 크기와 적당한 활성제 이온의 종류를 선택하여 우수한 발광 특성을 갖는 세라믹 형광체를 합성하고자 많은 노력을 경주하고 있다. 본 연구에서는 비교적 간단한 장비로 구성되며, 볼밀을 통하여 초기 물질들을 혼합하고 분쇄하여 최적의 형광 특성을 갖는 형광체 분말을 비교적 용이하게 합성하기에 적합한 고상반응법을 사용하여 적색, 황색, 녹색 형광체 La2WO6:RE3+ (RE=Eu, Dy, Tb)를 제조하고자 한다. 사용한 초기 물질은 (99.99% 순도), (99.99%), (99.9%), (99.9%) (99.9%)을 화학 정량으로 준비하였고, 활성제 이온의 함량비를 0, 0.01, 0.05, 0.10, 0.20 mol로 각각 변화시켜 형광체를 제조하여 그것의 발광과 흡광, 결정 입자의 크기와 형상을 조사하였다. 이온이 도핑된 형광체의 경우에, 발광 스펙트럼은 이온의 함량비에 관계없이 모든 시료에서 전형적인 이온의 (j=1-4) 전이에 의한 발광 스펙트럼을 나타내었고, 가장 강한 적색 발광 파장은 611 nm에서 관측되었으며, 이온의 함량비가 0.15 mol에서 발광 피크가 장파장 쪽으로 10 nm 이동하였으며, 세 종류의 발광 스펙트럼의 세기는 최대를 나타내었다. 이온의 함량비가 더욱 증가함에 따라 모든 발광 스펙트럼의 세기는 순차적으로 감소하였다. 이 현상은 농도 소광 현상으로 해석 할 수 있다. 이온이 도핑된 형광체의 경우에, 이온의 함량비에 관계없이 모든 시료에서 이온의 전형적인 전이에 의한 발광 스펙트럼이 관측되었으며, j=13/2에서 가장 강한 황색 발광이 피크 581 nm에서 관측 되었다. 상대적으로 발광 세기가 약한 484 nm에 정점을 갖는 청색 발광스펙트럼은 전이 신호이다. 이온의 함량비가 0.10 mol 일 때 세 영역의 발광 스펙트럼의 세기는 최대를 나타내었다. 이온의 함량비가 증가함에 따라 모든 발광 스펙트럼의 세기는 순차적으로 감소하였다. 주 흡광 스펙트럼은 이온의 함량비에 관계없이 모든 시료에서 파장 250 nm에서 관측되었다. 이온이 도핑된 형광체의 경우에, 이온의 함량비에 관계없이 모든 형광체 분말은 발광 세기가 제일 강한 550 nm의 피크를 갖는 녹색 발광과 상대적으로 발광 세기가 약한 495와 590 nm에 피크를 갖는 청색과 주황색 발광 스펙트럼들이 각각 관측되었다. 이 발광 신호들은 Tb3+ 이온의 5D47Fj (j=4, 5, 6) 전이에 의해 발광된 신호임을 확인하였다.

• Korean Journal of Plant Tissue Culture
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• v.25 no.4
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• pp.231-236
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• 1998

Carrot cotyledon explants cultured on MS medium with 1 mg/L 2,4-D were transferred to a hormone-free solid medium overlaid with filter paper in order to elucidate the effect of simple physical treatment on the development and germination of somatic embryos. Transfer of the explants cultured for one week on MS basal medium overlaid with 3 sheets of filter paper on to MS basal medium increased somatic embryo production 2-39 times over the one week culture on medium without filter paper overlay. Maturation and germination of somatic embryos was more prominent on medium overlaid with filter paper than on medium without filter paper. The explants cultured for one week on filter paper overlay added with liquid medium showed prominent decrease in somatic embryo formation compared to filter paper overlay only. It is suggested that the filter paper overlay affected the moisture environment of the somatic embryos developing on it.

• Journal of Adhesion and Interface
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• v.23 no.3
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• pp.75-79
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• 2022

Graphene is a two-dimensional carbon allotrope composed of honeycomb sp² hybrid orbital bonds. It shows excellent electrical and mechanical properties and has been spotlighted as a core material for next-generation electronic devices. However, it exhibits low environmental stability due to the easy penetration or adsorption of external impurities from the formation of an unstable interface between the materials in the electronic devices. Therefore, this work aims to improve and investigate the low environmental stability of graphene-based field-effect transistors through direct growth using solid hydrocarbons as a precursor of graphene. Graphene synthesized from direct growth shows high electrical stability through reduction of change in charge mobility and Dirac voltage. Through this, a new approach to utilize graphene as a core material for next-generation electronic devices is presented.

• Journal of Radiation Industry
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• v.17 no.2
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• pp.183-190
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• 2023

The global problem of handling radioactive materials is facing limitations. Eco-friendly bioremediation methods using microorganisms are being studied. This study was conducted to screen cesium-resistant microbial strains. M1 strain was selected from the soil sample by enriched culture in R2A medium containing 100 mM CsCl. In liquid medium containing above 40 mM of CsCl, the growth of M1 was inhibited in a concentration-dependent manner. Otherwise, M1 can survive up to 80mM CsCl in solid medium although the growth rate was slow and colony size was small. M1 strain was genetically identified as a strain of the genus Acinetobacter through 16S rRNA sequencing, and radiation resistance (D10 value) of M1 was found to be 0.307 kGy. These results showed that M1 strain is highly resistant to cesium and can grow in radiation environment. It was considered that M1 strain is useful in the field of biological decontamination of cesium.

• Journal of Dairy Science and Biotechnology
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• v.26 no.2
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• pp.23-30
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• 2008

This study implicated that the CBT-AK5 purified from Lactobacillus casei (LAFTI L26) which showed antitumor activity in ICR mice. Hence, ICR mice were inoculated intraperitoneally Sarcoma-180 as well as CBT-AK5. Then we observed the life span and tumor increment of those ICR mice. Here our studies showed effect on two different way of treatment as intraperitoneally and orally treated in Sarcoma-180 infected ICR mice. We found that intraperitoneally treatment of Sarcoma-180 and CBT-AK5 is more effective than orally fed. The life span of the ICR mice were highly reduced after the inoculation of Sarcoma-180. Those effects like increment of body weight, the growth of ascites and solid were inhibited significantly after the treatment of CBT-AK5 in Sarcoma-180 infected ICR mice. Finally these studies suggested that CBT-AK5 isolated form Lactobacillus casei showed excellent antitumor activity against Sarcoma-180 infected ICR mice.

• Radiation Oncology Journal
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• v.21 no.4
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• pp.322-329
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• 2003

Purpose: It is difficult to exactly determine the surface dose and the dose distribution In buildup region of high energy X-rays by using the conventional ion chamber. The aim of this study Is to evaluate the accuracy of widely used dosimetry systems to measure the surface dose and the depth of maximum dose (d$_{max}$). Materials and Methods: We measured the percent depth dose (PDD) from the surface to the d$_{max}$ in either a water phantom or in a solid water phantom using TLD-100 chips, thimble type ion chamber, diode detector, diamond detector and Markus parallel plate ion chamber for 6 MV and 15 MV X-rays, 10$\times$10 cm$^{2}$, at SSD=100cm. We analysed the surface dose and the d$_{max}$. In order to verify the accuracy of the TLD data, we executed the Monte Carlo simulation for 5 MV X-ray beams. Results: The surface doses In 6 MV and IS MV X-rays were 29.31% and 23.36% ior Markus parallel plate ion chamber, 37.17$\%$ and 24.01$\%$ for TLD, 34.87$\%$ and 24.06$\%$ for diamond detector, 38.13$\%$ and 27.8$\%$ for diode detector, and 47.92$\%$ and 35.01$\%$ for thimble type ion chamber, respectively. in Monte Carlo simulation for 6 MV X-rays, the surface dose was 36.22$\%$, which Is similar to the 37.17$\%$ of the TLD measurement data. The d$_{max}$ In 6 WV and 15 MV X-rays was 14$\~$16 mm and 27$\~$29 mm, respectively. There was no significant difference in the d$_{max}$ among the detectors. Conclusion: There was a remarkable difference in the surface dose among the detectors. The Markus parallel plate chamber showed the most accurate result. The surface dose of the thimble ion chamber was 10$\%$ higher than that of other detectors. We suggest that the correction should be made when the surface dose of the thimble ion chamber Is used for the treatment planning ion the supeficial tumors. All the detectors used In our study showed no difference in the d$_{max}$.

• Korean Journal of Environmental Biology
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• v.28 no.4
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• pp.223-230
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• 2010

To investigate the variations of physico-chemical factors in four stations (Hanlim, Aewol, Sinchon, Hamdeok) at Jeju coastal area, Water temperature, Salinity, dissolved oxygen (DO), pH, chemical oxygen demand (COD), suspended solid (SS), ammonia-nitrogen ($NH_4-N$), nitrite-nitrogen ($NO_3-N$), nitrate-nitrogen ($NO_2-N$) were analysed. The ranges of water temperature were from 26.23 to $28.6^{\circ}C$, the salinity were from 31.4 to 32.88‰, the pH were from 8.15 to 8.35, the chemical oxygen were from 0.48 to 0.91 mg $L^{-1}$. A total of 52 strains of marine actinomycetes was isolated from Jeju Island coastal area. They were characterized by determining morphological and physio-biochemical properties, the API kit and confirmed by molecular methods including partial sequencing of 16S rRNA. A neighbor-joining tree of partial 16S rRNA sequences divided the 52 isolates in 2 major groups, 22 strains of Gram positive bacteria/Actinobacteria (division)/Actinomycetales (order)/Streptomycineae (suborder)/Streptomycetaceae (family)/Streptomyces (93.1%) and 2 strains of Streptospotangineae (suborder)/Nocardiopsaceae (family)/Nocardiopsis (6.9%).