• 한국전기전자재료학회논문지
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• 제11권7호
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• pp.571-580
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• 1998

The numerical model that can describe the ignition of pseudospark discharge using hybrid fluid-particle(Monte Carlo )method has been developed. This model consists of the fluid expression for transport of electrons and ions and Poisson's equation in the electric field. The fluid equation determines the spatiotemporal dependence of charged particle densities and the ionization source term is computed using the Monte carlo method. This model has been used to study the evolution of a discharge in Argon at 0.5 torr, with an applied voltage if 1kV. The evolution process of the discharge has been divided into four phases along the potential distribution : (1) Townsend discharge, (2) plasma formation, (3) onset of hollow cathode effect, (4) plasma expansion. From the numerical results, the physical mechanisms that lead to the rapid rise in current associated with the onset of pseudospark could be identified.

• Journal of Astronomy and Space Sciences
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• 제39권2호
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• pp.23-33
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• 2022

Electron density irregularities in the equatorial ionosphere at night are understood in terms of plasma bubbles, which are produced by the transport of low-density plasma from the bottomside of the F region to the topside. Equatorial plasma bubbles (EPBs) have been detected by various techniques on the ground and from space. One of the distinguishing characteristics of EPBs identified from long-term observations is the systematic seasonal and longitudinal variation of the EPB activity. Several hypotheses have been developed to explain the systematic EPB behavior, and now we have good knowledge about the key factors that determine the behavior. However, gaps in our understanding of the EPB climatology still remain primarily because we do not yet have the capability to observe seed perturbations and their growth simultaneously and globally. This paper reviews the occurrence climatology of EPBs identified from observations and the current understanding of its driving mechanisms.

• 한국해안해양공학회지
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• 제7권1호
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• pp.91-107
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• 1995

본 논문에서는 이안류의 생성ㆍ유지에 대한 모형을 크게 세가지로, 2차원 평면지형에서도 이안류가 생성되어 유지될 수 있는 프리즘지형 모형 (prismatic topography models), 이안류의 생성ㆍ유지를 위하여 쇄파대내의 3차원 해저지형을 필요로 하는 비프리즘지형 모형(non-prismatic topography models), 그리고 해안선을 따른 돌제 또는 방파제 등의 해안구조물이 생성하는 이안류 모형 등으로 분류하였다. 그러나 이안류의 생성ㆍ유지에 관계되는 모든 변수들을 포함한 지배역학현상을 규명하기 위해서는 더욱 더 많은 문헌연구가 필요하다는 것을 알았다. 다음에 연안사주 또는 잠제 등이 존재하는 해안지형과 그 위로의 해수 전달을 고려하여 연안사주와 해안선 사이에 흐르는 해안방향으로의 흐름현상을 예측키 위한 이론적인 모형을 개발하였다. 이 수리모형은 휴체력과 해저지형변환간에 서서히 발생하는 상호 간섭(slow feedback)을 고려할 수 있는 퇴적물 이동모형과 함께 연안지역에서의 해저지형변환 예측에 이용될 수 있으리라 사려된다.

• 한국수산과학회지
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• 제46권2호
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• pp.186-194
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• 2013

We compiled and analyzed long-term time-series data collected in Korea to evaluate changes in oceanographic conditions and marine ecosystems near Jeju Island ($33^{\circ}00^{\prime}-34^{\circ}00^{\prime}\;N$, $125^{\circ}30^{\prime}-127^{\circ}30^{\prime}\;E$) from 1981 to 2010. Environmental data included depth-specific time series of temperature and salinity that have been measured bimonthly since 1961 in water columns at 175 fixed stations along 22 oceanographic lines in Korean waters by the National Fisheries Research & Development Institute, and time series of estimated volume transport of the Tsushima Warm Current (TWC) and Korea Strait Bottom Cold Water (KSBCW) for the period from 1961 to 2008. We analyzed the species composition in terms of biomass of fish species caught by Korean fishing vessels in the waters near Jeju Island (1981-2010). Data were summarized and related to environmental changes using canonical correspondence analysis (CCA). The CCA detected major shifts in fish community structure between 1982 and 1983 and between 1990 and 1992; the dominant species were a filefish during 1981-1992 and chub mackerel from 1992 to 2007. CCA suggested that water temperature and salinity in the mixed layer and the volume transport of the TWC and the KSBCW were significantly related to the long-term changes in the fish community in the waters off Jeju Island. Fish community shifts seemed to be related to the well-established 1989 regime shift in the North Pacific. Further studies are required to elucidate the mechanisms driving climate change effects on the thermal windows and habitat ranges of commercial species to develop fisheries management plans based on reliable projections of long-term changes in the oceanographic conditions in waters off Jeju Island.

• Journal of Plant Biotechnology
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• 제39권1호
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• pp.23-32
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• 2012

Calcium is an essential nutrient for living organisms, with key structural and signaling roles. Its deficiency in plants can result in poor biotic and abiotic stress tolerance as well as reduced crop quality and yield. Calcium deficiency in humans causes various diseases such as osteoporosis and rickets. Biofortification of calcium in various food crops has been suggested as an economic and environmentally advantageous method to enhance human intake of calcium. Recent efforts to increase the levels of calcium in food crops have used calcium/proton antiporters ($CAXs$) and modified one to increase calcium transport into vacuoles through genetic engineering. It has been reported that overall calcium content of transgenic plants has been increased in their edible portions with some adverse effects. In conclusion, biofortification of calcium will add more value in crops as well as will be beneficial for animal and human. Therefore, more fundamental studies on the mechanisms of calcium ion storage and transporting are essential for more effective calcium biofortification.

• 대한화학회지
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• 제18권6호
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• pp.391-399
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• 1974

금속 코발트의 부식과 부동화현상들을 전기화학적 실험방법들을 써서 연구하였다. Tafel slope, Flade potential의 pH의존도, 부식속도의 반응역학적 데이타등으로 부터 코발트와 붕산염완충용액 사이 계면에서 일어나는 부식과 부동화 과정들의 메카니즘을 도출하였다. 금속표면에 흡착된 히드록실기가 표면산화와 부동화막의 형성에 참여하는 것으로 나타났다. 표면막의 성장속도에 관한 데이타로 보아 부동화피막은 "전기장에 의한-이온-이동" 과정에 의하여 성장하는 것으로 보인다. 측정된 표면막의 두께는 약 10${\AA}$에서 20${\AA}$에 이르렀다.

• 자원환경지질
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• 제32권1호
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• pp.43-51
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• 1999

In order to remediate hazardous waste site, a process of electrokinetically purging chemicals from saturated soil is examined by laboratory experiments. Electrokinetic soil remediation is one of the most promising soil decontamination processes that habe igh removal efficiency and time-effectiveness in low-permeability soils such as clay. Being combined with several mechanisms-electromigration, elec troosmosis, diffusion and electrolysis of water, electrokinetic soil processing can remove non-polar organics as well as ionic contaminants. The objectives of this study are; 1) the exploration of the feasibility of electrokinetic soil processing on the removal of heavy metals, 2) the investigation of applicability to the tailing-soils in aban doned mining area, 3) the examination of effects of soil pH and conductivity on the transport phenomena of elements in soils, and 4) the investigation of the applicability of the ionexchange membrance to the efficient collection of heavy metals removed from contaminated soils. With the result of this study, it is suggested that the removal efficiency is significantly influenced by applied voltage & current, type of purging solutions, soil pH, permeability and zeta potentials of soil. Although further study should be needed, it is possible to collect removed heavy metals with ion-exchange membrance in cathode compartment.

• Translational and Clinical Pharmacology
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• 제26권3호
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• pp.103-110
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• 2018

The human microbiome is known to play an essential role in influencing host health. Extracellular vesicles (EVs) have also been reported to act on a variety of signaling pathways, distally transport cellular components such as proteins, lipids, and nucleic acid, and have immunomodulatory effects. Here we shall review the current understanding of the intersectionality of the human microbiome and EVs in the emerging field of microbiota-derived EVs and their pharmacological potential. Microbes secrete several classes of EVs: outer membrane vesicles (OMVs), membrane vesicles (MVs), and apoptotic bodies. EV biogenesis is unique to each cell and regulated by sophisticated signaling pathways. EVs are primarily composed of lipids, proteins, nucleic acids, and recent evidence suggests they may also carry metabolites. These components interact with host cells and control various cellular processes by transferring their constituents. The pharmacological potential of microbiome-derived EVs as vaccine candidates, biomarkers, and a smart drug delivery system is a promising area of future research. Therefore, it is necessary to elucidate in detail the mechanisms of microbiome-derived EV action in host health in a multi-disciplinary manner.

• Journal of Electrochemical Science and Technology
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• 제14권4호
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• pp.320-325
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• 2023

In Li-ion batteries, a thick electrode is advantageous for lowering the inactive current collector portion and obtaining a high energy density. One of the critical failure mechanisms of thick electrodes is inhomogeneous lithiation and delithiation owing to the axial location of the electrode. In this study, it was confirmed that the top layer of the composite electrode contributes more to the charging step owing to the high ionic transport from the electrolyte. A high-loading multilayered electrode containing LiFePO₄ (LFP) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) was developed to overcome the inhomogeneous electrochemical reactions in the electrode. The electrode laminated with LFP on the top and NCM811 on the bottom showed superior cyclability compared to the electrode having the reverse stacking order or thoroughly mixed. This improvement is attributed to the structural and interfacial stability of LFP on top of the thick electrode in an electrochemically harsh environment.

• Journal of Ginseng Research
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• 제45권1호
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• pp.66-74
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• 2021

Background: Abnormal chloride (Cl-) transport has a detrimental impact on mucociliary clearance in both cystic fibrosis (CF) and non-CF chronic rhinosinusitis. Ginseng is a medicinal plant noted to have anti-inflammatory and antimicrobial properties. The present study aims to assess the capability of red ginseng aqueous extract (RGAE) to promote transepithelial Cl- secretion in nasal epithelium. Methods: Primary murine nasal septal epithelial (MNSE) [wild-type (WT) and transgenic CFTR-/-], fisher-rat-thyroid (FRT) cells expressing human WT CFTR, and TMEM16A-expressing human embryonic kidney cultures were utilized for the present experiments. Ciliary beat frequency (CBF) and airway surface liquid (ASL) depth measurements were performed using micro-optical coherence tomography (μOCT). Mechanisms underlying transepithelial Cl- transport were determined using pharmacologic manipulation in Ussing chambers and whole-cell patch clamp analysis. Results: RGAE (at 30㎍/mL of ginsenosides) significantly increased Cl- transport [measured as change in short-circuit current (ΔISC = ㎂/㎠)] when compared with control in WT and CFTR-/- MNSE (WT vs control = 49.8±2.6 vs 0.1+/-0.2, CFTR-/- = 33.5±1.5 vs 0.2±0.3, p < 0.0001). In FRT cells, the CFTR-mediated ΔISC attributed to RGAE was small (6.8 ± 2.5 vs control, 0.03 ± 0.01, p < 0.05). In patch clamp, TMEM16A-mediated currents were markedly improved with co-administration of RGAE and uridine 5-triphosphate (8406.3 +/- 807.7 pA) over uridine 5-triphosphate (3524.1 +/- 292.4 pA) or RGAE alone (465.2 +/- 90.7 pA) (p < 0.0001). ASL and CBF were significantly greater with RGAE (6.2+/-0.3 ㎛ vs control, 3.9+/-0.09 ㎛; 10.4+/-0.3 Hz vs control, 7.3 ± 0.2 Hz; p < 0.0001) in MNSE. Conclusion: RGAE augments ASL depth and CBF by stimulating Cl- secretion through CaCC, which suggests therapeutic potential in both CF and non-CF chronic rhinosinusitis.