• Particle and aerosol research
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• v.8 no.1
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• pp.29-35
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• 2012

The Faraday cup electrode of different size has been developed and evaluated to investigate the diffusion effect of particles by Brownian motion in a particle beam mass spectrometer(PBMS). Particles which focused and accelerated by aerodynamic lens are charged to saturation in an electron beam, and then deflected electrostatically into a Faraday cup detector for measurement of the particle current. The concentration of particles is converted from currents detected by Faraday cup. Measurements of particle current as a function of deflection voltage are combined with measured relationships between particle velocity and diameter, charge and diameter, and mass and diameter, to determine the particle size distribution. The particle currents were measured using 5, 10, 20, 40 mm sized Faraday cup that can be move to one direction by motion shaft. The current difference for each sizes as a function of position was compared to figure out diffusion effect during transport. Polystyrene latex(PSL) 100, 200 nm sized standard particles were used for evaluation. The measurement using 5 mm sized Faraday cup has the highest resolution in a diffusion distance and the smaller particles had widely diffused.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.1-8
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• 1992

This paper presents a p-version finite element approach for modeling the stress distribution around a circular hole in a finite strip subjected to membrane and flexural behaviors. Also, same problem with a crack emanating from a perforated tension strip was solved by virtual crack extension method. The p-version of the finite element method based on integrals of Legendre polynomials is shown to perform very well for modeling geometries with very steep stress gradients in the vicinity of a circular cutout. Here, the transfinite mapping technique for circular boundaries was used to avoid the discretization errors. The numerical results from the proposed scheme have a good comparison with those by Nisida, Howland, Newman etc. and the conventional finite element approach.

• Journal of The Korean Astronomical Society
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• v.33 no.1
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• pp.1-17
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• 2000

We have performed extensive simulations of response of gaseous disk in barred galaxies using SPH method. The gravitational potential is assumed to be generated by disk, bulge, halo, and bar. The mass of gaseous disk in SPH simulation is assumed to be negligible compared to the stellar and dark mass component, and the gravitational potential generated by other components is fixed in time. The self-gravity of the gas is not considered in most simulations, but we have made a small set of simulations including the self-gravity of the gas. Non-circular component of velocity generated by the rotating, non-axisymmetric potential causes many interesting features. In most cases, there is a strong tendency of concentration of gas toward the central parts of the galaxy. The morphology of the gas becomes quite complex, but the general behavior can be understood in terms of simple linear approximations: the locations and number of Lindblad resonances play critical role in determining the general distribution of the gas. We present our results in the form of 'atlas' of artificial galaxies. We also make a brief comment on the observational implications of our calculations. Since the gaseous component show interesting features while the stellar component behaves more smoothly, high resolution mapping using molecular emission line for barred galaxies would be desirable.

• Journal of Environmental Impact Assessment
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• v.7 no.1
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• pp.81-91
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• 1998

The objective of this study was to use remotely sensed data, combined with in situ data, for the assessment of trophic state for Daecheong reservoir. Three Landsat TM(Thematic Mapper) imagery data were processed to portray trophic state conditions. The remotely sensed data and the measured data were obtained on 20 June 1995. Regression models have been developed between the chlorophyll-a concentration and reflectance which was converted to Landsat TM digital data. The regression model was determined based on the correlation coefficient which was higher than 0.7 and was applied to the entire study area to generate a distribution map of chlorophyll-a and trophic state. The equation, providing estimates of chlorophyll-a concentration, represented the year-to-year spatial variation of trophic zones in the reservoir. Satellite remote sensing data derived from Landsat TM had been successfully used for trophic slate mapping in Daecheong reservoir.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.182-183
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• 2004

Atmospheric carbon monoxide (CO) and ozone $(O_3)$ play the important trace gases in tropospheric chemistry, through its concentration in the troposphere directly influences the concentrations of tropospheric hydroxyl (OH). Understanding the impact of CO and $O_3$ on the global tropospheric chemistry requires measurements of the global atmospheric CO and $O_3$ distributions. This study focuses on the identification of CO and O3 released in the East Asia between March 2000 and February 2004. During the period, the MOPITT instrument onboard the Earth Observing System (EOS)-Terra platform collected extensive measurement of CO. So we have used MOPITT data at 700hPa to analyze seasonal distribution of CO concentration. And the O3 measurements for this study were Total Ozone Mapping Spectrometer (TOMS) and Dobson spectrometer provided NASA/GSFC and Yonsei University, Korea. During springtime, the CO and O3 concentrations were increased over East Asia for April, May, and June. CO and O3 transport and chemistry in the springtime in East Asia are studied by use of the HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.902-910
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• 2018

In recent times, development of nanofluid insulation for power transformers is a hot research topic. Many researchers reported the enhancement in dielectric characteristics of nano modified mineral oils. Considering the drawbacks of petroleum based mineral oil, it is necessary to understand the dielectric characteristics of nanofluids developed with natural ester based oils. Palm oil has better insulation characteristics comparable to mineral oil. However very few research reports is available in the area of nanofluids based on palm oil. Partial discharge (PD) is one of the major sources of insulation performance degradation of transformer oil. It is essential to understand the partial discharge(PD) characteristics by collecting huge data base of PD performance of nano modified palm oil which will increase its confidence level for power transformer application. Knowing these facts, in the present work, certain laboratory experiments have been performed on PD characteristics of nano $SiO_2$ modified palm oil at different electrode configurations. Influence of concentration of nano filler material on the PD characteristics is also studied. Partial discharge inception voltage, Phase resolved partial discharge (PRPD) pattern, PD signal time-frequency domain characteristics, PD signal equivalent timelength-bandwidth mapping, Weibull distribution statistical parameters of PRPD pattern, skewness, repetition rate and phase angle variations are evaluated at different test conditions. From the results of the experiments conducted, we came to understand that PD performance of palm oil is considerably enhanced with the addition of $nano-SiO_2$ filler at 0.01%wt and 0.05%wt concentration. Significant reduction in PD inception voltage, repetition rate, Weibull shape parameter and PD magnitude are noticed with addition of $SiO_2$ nanofillers in palm oil. These results will be useful for recommending nano modified palm oil for power transformer applications.

• Ocean and Polar Research
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• v.29 no.2
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• pp.87-99
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• 2007

This study was conducted to understand the source and behavior of organic matter using the fluorescent technique (excitation-emission matrix) as a part of environmental monitoring program in the Korea manganese nodule mining site in the Northeastern Pacific Ocean. Water samples were collected at $0^{\circ},\;6^{\circ}N$, and $10.5^{\circ}N$ along $131.5^{\circ}W$ in August 2005. The concentration of total organic carbon (TOC) ranged from 58.01 to $171.93\;{\mu}M-C$. The vertical distribution of TOC was characterized as higher in the surface layer and decreased with depth. At $6^{\circ}N$, depth-integrated (from surface to 200 m depth) TOC was $337.1\;gC/m^2$, which was 1.4 times higher value than other stations. The exponential decay curve fit of vertical profile of TOC indicated that 59% of organic carbon produced by primary production in the surface layer could be decomposed by bacteria in the water column. Dissolved organic matter is generally classified into two distinctive groups based on their fluorescence characteristics using three-dimensional excitation/emission (Ex/Em) fluorescence mapping technique. One is known as biomacromolecule (BM; protein-like substance; showing max. at Ex 280/Em 330), mainly originated from biological metabolism. The other is geomacromolecule (GM; humic-like substance; showing max. at Ex 330/Em 430), mainly originated from microbial degradation processes. The concentration of BM and GM was from 0.42 to 7.29 TU (tryptophan unit) and from 0.06 to 1.81 QSU (quinine sulfate unit), respectively. The vertical distribution of BM was similar to that of TOC as high in the surface and decreased with depth. However, the vertical distribution of GM showed the reverse pattern of that of BM. From these results, it appeared that BM occupied a major part of TOC and was rapidly consumed by bacteria in the surface layer. GM was mainly transformed from BM by microbial processes and was a dominant component of TOC in the deep-sea layer.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.477-491
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• 2013

Natural radionuclides in groundwater in the Danyang area were investigated to characterize the behaviors of uranium and radon with respect to lithology and physico-chemical components, which can aid our understanding of their occurrence, properties, and origins. To this end, a total of 100 groundwater samples were collected and analyzed, and radionuclide levels were used to construct detailed concentration maps. The water type of the groundwater, assessed using a Piper diagram, is mainly Ca-Na-$HCO_3$. The concentrations of uranium range from 0.02 to $251.0{\mu}g/L$ (average, $3.85{\mu}g/L$) and only 1% exceed USEPA's MCL (Maximum Contaminant Level). Uranium is enriched in groundwaters of Cretaceous granites and Precambrian metamorphic rocks, whereas it is depleted in groundwaters of sedimentary rocks. The concentrations of radon range from 13 to 28,470 pCi/L (average, 2397 pCi/L). Only 15% of the samples exceed AMCL (Alternative Maximum Contaminant Level) of 4000 pCi/L. The radon concentration is highest in groundwater of Cretaceous granites and lowest in groundwater of sedimentary rocks. In conclusion, the distribution and occurrence of radionuclides are intimately related to the basic geological characteristics of the rocks in which the radiogenic minerals are primarily contained. The behavior of uranium is only weakly related to that of radon (correlation coefficient = 0.15). There are also weak correlations between radionuclides and the main chemical components, pH, EC, Eh, and well depth. Of note, the correlation coefficient between radon and $SiO_2$ is 0.68, and that between radon and $HCO_3$ is -0.48. Factor analysis shows that radionuclides behave somewhat independently of each other because there are no significant factors that control the behavior of chemical components as well as radionuclides. The detailed concentration maps during this study will be used to establish useful database of radionuclide distribution and geological properties throughout Korea.

• Journal of Acupuncture Research
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• v.18 no.3
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• pp.56-68
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• 2001

Objective : Functional brain mapping study on acupuncture stimulation using the [14C]2-deoxyglucose([14C]2-DG) autoradiography provides quantitative data and visualized pathway in central nervous system(CNS). We aimed to investigate the neural pathway and spatial distribution of metabolic activity elicited in CNS on electroacupuncture stimulation using [14C]2-DG autoradiography. Methods : The study were divided into three groups by stimulation times. 45-mins stimulation group according to Sokoloffs method, 5-mins stimulation group according to Duncun's method, and 15-mins stimulation group. ;A venous catheter was equipped into right jugular vein. The rats (Sprague-Dawley rats, 230-260g) were kept fastened loosely on a holding platform without anesthesia. Electroacupuncture stimulation (5 ms, 2 Hz, 1~3 mA) were applied on the left Zusanli (ST36) acupoint and [14C]2-DG ($25{\mu}Ci/rat$) injection was performed through the catheter. After sacrifice, the brain and the spinal cord were made to sections for film image. The film images were digitalized as the isotope concentration based upon comparison of optical densities with that of the standards and normalized by the optical density of corpus callosum. Results : 1. 15-mins stimulation group was most effective among 3 experiments. 2. On 15-mins stimulation group, medial geniculate nucleus, intetpeduncular nucleus intermedius, ventral periolivary nucleus, caudal periolivary nucleus, medial superior olive, lateral paragigantocellular nucleus, including hypothalamic arcuate nucleus were increased by more than 25% (at least, p<0.05) by electroacupuncture stimulation. 3. Especially, the metabolism in hypothalamic arcuate nucleus was increased by 90% (p<0.05). 4. The fact that arcuate nucleus of hypothalamus might play a role of interconnection area between ascending and descending pathway of acupuncture stimulation was demonstrated visually. Conclusions : Advanced study on electroacupuncture stimulation elicited significant increase of metabolic activity in various nuclei of hypothalamus will provide the important experimental basis in research of the relationship between electroacupuncture stimulation and internal visceral functions.

• Korean Journal of Remote Sensing
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• v.36 no.6_1
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• pp.1339-1348
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• 2020

Phytoplankton controls marine ecosystems in terms of nutrients, photosynthetic rate, carbon cycle, etc. and the degree of its influence on the marine environment depends on their physical size. Many studies have been attempted to identify marine phytoplankton size classes using the remote sensing techniques. One of successful approach was the three-component model which estimates the chlorophyll concentrations of three phytoplankton size classes (micro-phytoplankton; >20 ㎛, nano-; 2-20 ㎛ and pico-; <2 ㎛) as a function of total chlorophyll. Here, we examined the applicability of Geostationary Ocean Colour Imager (GOCI) to the mapping of the phytoplankton size class distribution in the East Sea. A fit of the three-component model to a biomarker pigment dataset collected in the study area for some years including a large harmful algal bloom period has been carried out to derive size-fractioned chlorophyll concentration (CHL). The tuned three-component model was applied to the hourly GOCI images to identify the fractions of each phytoplankton size class for the entire CHL. Then, we investigated the distribution of phytoplankton community in terms of the size structure in the East Sea during the harmful Cochlodinium polykrikoides blooms in the summer of 2013.