• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.43-48
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• 2018

In this paper, we present a method for removing shadows from scanned documents. Compared to the existing methods such as one based on image pyramid representation or adaptive thresholding, our method produces more robust and higher quality results. The basic idea of the approach is to use the local image statistics and to separate interesting regions from the image such as the regions around letters and figures. For the separated regions, we adaptively adjust the local brightness and contrast, and apply the sigmoid function to the intensity values as well to enhance the clarity of the image. For separated the other empty regions, we apply the gradient-base image hole filling method to fill the region with smooth color change.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.1
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• pp.46-52
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• 2012

Separate extraction of source ($R_S$) and drain ($R_D$) resistances caused by process, layout variations and long term degradation is very important in modeling and characterization of MOSFETs. In this work, we propose "Avalanche Hot-Source Method (AHSM)" for simple separated extraction of $R_S$ and $R_D$ in a single device. In AHSM, the high field region near the drain works as a new source for abundant carriers governing the current-voltage relationship in the MOSFET at high drain bias. We applied AHSM to n-channel MOSFETs as single-finger type with different channel width/length (W/L) combinations and verified its usefulness in the extraction of $R_S$ and $R_D$. We also confirmed that there is a negligible drift in the threshold voltage ($V_T$) and the subthreshold slope (SSW) even after application of the method to devices under practical conditions.

• Journal of the Korea Computer Graphics Society
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• v.16 no.2
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• pp.39-45
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• 2010

The color of object is a main role that people recognize outdoor entity with its shape. We can perceive the object due to the existence of light such as direct sunlight. Light is classified by wavelength into radio, microwave, infrared, the visible region we perceive as light, ultraviolet, X-rays and gamma rays. White light is all of the colors of light combined within the visible light spectrum. When white light is separated through a prism, we see the visible light spectrum. The various wavelengths of visible light are separated into colors. In this paper, we construct white light as the seven colors of rainbow and suggest the method of N-way color dispersion photon mapping to simulate the natural dispersion phenomenon.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.7
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• pp.1691-1701
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• 1995

Two aspects of Large-Eddy Simulation(LES) are investigated in order to improve its performance. The first one is on how to determine the model coefficient in conjunction with a dynamic subgrid-scale model, and the second one is on a wall-layer model(WLM) which allows one to skip near-wall regions to save a large number of grid points otherwise required. Especially, a WLM suitable for a separated flow is considered. Firstly, an averaging technique to calculate the model coefficient of dynamic subgrid-scale modeling(DSGSM) is introduced. The technique is based on the concept of local averaging, and useful to stabilize numerical solution in conjunction with LES of complex turbulent flows using DSGSM. It is relatively simple to implement, and takes very low overhead in CPU time. It is also able to detect the region of negative model coefficient where the "backscattering" of turbulence energy occurs. Secondly, a wall-layer model based on a local turbulence intensity is considered. It locally determines wall-shear stresses depending on the local flow situations including separation, and yields better predictions in separated regions than the conventional WLM. The two techniques are tested for a turbulent obstacle flow, and show the direction of further improvements.rovements.

• ALGAE
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• v.24 no.3
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• pp.129-138
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• 2009

DNA-based discrimination of species is a powerful way for morphologically otherwise similar species, like centric diatoms. Here, the author sequenced long-range nuclear ribosomal DNAs, spanning from the 18S to the D5 region of the 28S rDNA, of Stephanodiscus, particularly including a Korean isolate. By comparisons, high DNA similarities were detected from the rDNAs of nine Stephanodiscus (>99.4% in 18S rDNA, >98.0% in 28S rDNA). Their genetic distances, however, were significantly different (Kruskal-Wallis test, p < 0.01) compared to two related genera, namely Cyclotella and Discostella. In addition, genetic distances of 18S rDNAs were significantly different (Student’s t-test, p = 0.000) against those of the 28S rDNAs according to individual genera (Cyclotella, Discostella, and Stephanodiscus). Phylogenetic analyses showed that Stephanodiscus and Discostella showed a sister taxon relationship, and their clade was separated from a cluster of Cyclotella (1.00 PP, 100% BP). This suggests that Stephanodiscus has highly conserved sequences of both 18S and 28S rDNA; however, Stephanodiscus is well-separated from other freshwater centric diatoms, such as Cyclotella and Discostella, at the generic level.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1290-1299
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• 1990

Characteristics of flow patterns in horizontal gas-liquid two-phase flow for two different sizes of pipe were investigated based upon a statistical analysis of differential pressure fluctuations at an orifice. The probability density function and the power spectral density function of the traces indicate peculiar shapes depending upon the two-phase flow regime. Mixed and separated flows also could be identified by the autocorrelation function. The transition region from separated flow to mixed flow also could be identified by these statistical properties. The experimental data determined by this method were compared with the flow pattern maps suggested by other investigators. The result indicates that the statistical characteristics of differential pressure fluctuations at orifices may be a useful tool for identifying flow patterns of horizontal gas-liquid two-phase flow.

• Animal Systematics, Evolution and Diversity
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• v.26 no.2
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• pp.99-104
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• 2010

The subfamily Murinae is a very controversial group concerning their phylogenetic relationship. Previous studies could not resolve phylogeny among four genera Apodemus, Micromys, Mus and Rattus of the Muridae. In the present study, eight rodent species resident in South Korea were collected and phylogenetically analyzed based on sequence data of five mitochondrial and nuclear DNA regions: 12S rRNA, cytochrome b gene (cyt b), cytochrome oxidase II (COII), control region of mitochondrial DNA, and a thyroglobulin (Tg) of nuclear DNA. According to the phylogeny of the concatenated data, M. musculus separated early in Murinae (ML 100%; BA 1.00 pp) and the genus Rattus grouped with the harvest mouse, M. minutes; these were separated from the genus Apodemus with relatively strong support (ML 74%; BA 0.76 pp). The Siberian chipmunk population was also examined using the five genes to obtain better resolution. The phylogeny for Korean rodents determined using the 12S rRNA, cyt b, COII and control regions discriminated the Siberian chipmunk populations from Korea, Russia, and China.

• Journal of Sensor Science and Technology
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• v.27 no.6
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• pp.407-413
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• 2018

Most sleep apnea patients exhibit severe snoring, and long-lasting sleep apnea may cause insomnia, hypertension, cardiovascular diseases, stroke, and other diseases. Although polysomnography is the typical sleep diagnostic method to accurately diagnose sleep apnea by measuring a variety of bio-signals that occur during sleep, it is inconvenient as the patient has to sleep with attached electrodes at the hospital for the diagnosis. In this study, a diagnostic pillow is designed to measure respiration, heart rate, and snoring during sleep, using only one polyvinylidene fluoride (PVDF) sensor. A PVDF sensor with piezoelectric properties was inserted into a specially made instrument to extract accurate signals regardless of the posture during sleep. Wavelet analysis was used to identify the extractability and frequency domain signals of respiration, heart rate, and snoring from the signals generated by the PVDF sensor. In particular, to separate the respiratory signal in the 0.2~0.5 Hz frequency region, wavelet analysis was performed after removing 1~2 Hz frequency components. In addition, signals for respiration, heart rate, and snoring were separated from the PVDF sensor signal through a Butterworth filter and median filter based on the information obtained from the wavelet analysis. Moreover, the possibility of measuring sleep apnea from these separated signals was confirmed. To verify the usefulness of this study, data obtained during sleeping was used.

• Bulletin of the Korean Chemical Society
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• v.31 no.12
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• pp.3567-3572
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• 2010

Black pine barks from the southern region of Korea were extracted using pressurized hot water and the water soluble extracts were then separated in a stepwise fashion using a variety of solvents, column chromatography (CC), thin layer chromatography (TLC), and high pressure liquid chromatography (HPLC). The antioxidant activities of each fraction and the active compounds were determined based on the radical scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), reductive potential of ferric ion, and total phenol contents. A DPPH test showed that the half maximal effective concentration ($EC_{50}$ value : $6.59{\pm}0.31\;{\mu}g/mL$) of the ethyl acetate fraction (ca. 0.67%) was almost the same as that of the control compounds and inversely proportional to the value of the total phenol contents. The cell viability of the water extracts was confirmed by methyl thiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) with enzyme linked immune sorbent assay (ELISA). Catechin, epicatechin, quercetin and ferulic acid were isolated from the ethyl acetate fraction as active compounds and identified by nuclear magnetic resonance. The antioxidant activity as value of DPPH of each of the separated compounds was lower than the ethyl acetate fraction, and ferulic acid was the lowest among these compounds.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.30-35
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• 2016

In order to investigate effects of grid resolution on large-eddy simulation of flow over a heavy vehicle, large-eddy simulations over the vehicle with coarse grid and fine grid are conducted. In addition, comparison of drag coefficients with the experimental data obtained by a wind tunnel experiment is conducted. Both of the drag coefficients of coarse grid and fine grid large-eddy simulation show good agreement with the experimental data. Flow fields obtained by the coarse and the fine grid large-eddy simulation are compared in the vehicle frontal-face region, the vehicle rear wheel region, and the vehicle base region. Coarse grid large-eddy simulation shows good agreement with the fine grid large-eddy simulation in the vehicle front face region and the vehicle rear wheel region, since the flow over the present vehicle is dominated by flow separation which is geometrically pre-determined, not by the skin friction which is known to be sensitive to grid resolution.