• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.4B
• /
• pp.391-398
• /
• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.6 no.3
• /
• pp.425-432
• /
• 2011

To increase the bit rate over than 1 Gb/s in LED visible light communications, we need to reduce the multipath effect of the light in indoor environment. In this paper, we propose a MAC protocol for LED visible light wireless LAN with beamforming technique. We assumed that spatial light modulator is used for beamforming function. We use polling method since detecting another uplink channel is difficult in visible light communication. We also estimated the performance of the proposed MAC protocol.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.10
• /
• pp.3-10
• /
• 2012

The visible light communication takes advantages of LED and PD for communication and is considered as a next generation wireless communication technology. It can support variety indoor applications. Especially, Visible LAN service has drawn much attention due to high data rate and no interference with existing WPAN system as well as high efficiency in illumination. However, existing MAC protocol occurs a high communication delay due to uplink collision and backoff time. In this paper, to reduce packet delay, we propose an enhanced MAC protocol based on FDD where the time difference between uplink frame and downlink frame transmission is utilized. Through computer simulations, we verified that the proposed MAC protocol outperforms the existing MAC protocol in terms of average packet delay.

• Journal of the Korean Ceramic Society
• /
• v.55 no.3
• /
• pp.267-274
• /
• 2018

$TiO_2/CuS$ nanocomposites were fabricated by precipitation of nanosized CuS via sonochemical method on electrospun $TiO_2$ nanofibers, and their structure, chemical bonding states, optical properties, and photocatalytic activity were investigated. In the $TiO_2/CuS$ nanocomposite, the position of the conduction band for CuS was at a more negative than that of TiO; meanwhile, the position of the valence band for CuS was more positive than those for TiO, indicating a heterojunction structure belonging to type-II band alignment. Photocatalytic activity, measured by decomposition of methylene blue under visible-light irradiation (${\lambda}$ > 400 nm) for the $TiO_2/CuS$ nanocomposite, showed a value of 85.94% at 653 nm, which represented an improvement of 52% compared to that for single $TiO_2$ nanofiber (44.97% at 653 nm). Consequently, the photocatalyst with $TiO_2/CuS$ nanocomposite had excellent photocatalytic activity for methylene blue under visible-light irradiation, which could be explained by the formation of a heterojunction structure and improvement of the surface reaction by increase in surface area.

• Asian-Australasian Journal of Animal Sciences
• /
• v.17 no.9
• /
• pp.1227-1231
• /
• 2004

Pig oocytes contain high levels of lipids in the ooplasm, which reduces the visibility of the germinal vesicle (GV) under microscopic examination. Therefore, the purposes of this study were to investigate the effects of relative centrifugation force (RCF) on the visibility and maturation rates of the GV stage oocytes after centrifugation. In Experiment 1, cumulus-oocyte-complexes (COCs) were collected from slaughterhouse ovaries and randomly allocated to different RCFs (3,000 rpm: 970 g; 6,000 rpm: 3,900 g; or 10,000 rpm: 10,840 g) for 10 or 20 min. Percentages of visible GV were 76-79% in the oocytes centrifuged with 10,000 rpm, which were significantly higher (p<0.01) than those with 3,000 and 6,000 rpm. No significant differences in GV visibility were observed among oocytes with different lengths of centrifugation (p<0.05) regardless of the RCFs. In esperiment 2, the maturation rate of the oocyte was found significantly lower in the 20 min than in the 10 min group received 10,840 g of RCF (30 vs. 75%, p<0.05). In conclusion, the GV of porcine oocytes can be clearly visible by centrifugation at 10,840 g for 10 min without compromising their subsequent maturation rates and a longer centrifugation time (20 min) had no beneficial influence on the visibility of GV stage pig oocytes.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.27 no.3
• /
• pp.357-365
• /
• 2009

RTLS(Real-Time location system) for Location tracking of personnel and equipment of a construction site is now in development, among these techniques the wireless LAN-based techniques are being considered. To introduce these techniques to the construction site, the 3-dimensional visibility analysis prior to the installation location of AP must be simulated. At this time, three-dimensional visibility analysis considering the propagation distance of RTLS signal of AP(Access Point) should be performed. In this research, two processing methods LOS boundary are tested to various grid size of gridded terrestrial LiDAR data, and the results were compared. In evaluations of visible area, the Scanline Fill-Method shows approximately 7.4% more visible area than the Shadow Clipping-Method, but the Shadow Clipping-Method shows stable results for the grid size. About the processing time, the Scanline Fill-Method is about 2 times faster compared to the Shadow Clipping-Method.

• KSBB Journal
• /
• v.29 no.4
• /
• pp.263-270
• /
• 2014

This study reports significant improvement of atopic dermatitis condition as a result of experiment using Xanthium strumarium L. extract (XS-E) at the dorsal skin of induced atopic dermatitis Nc/Nga mice. Skin clinical score has decreased ($2.75{\pm}0.85$, *p<0.05), showing visible change of skin condition. IgE (***p<0.001) and IgG1 ($2522.00{\pm}32.80$, ***p<0.001) in plasma also decreased significantly. mRNA (gene expression) level increased ($RQ=2.75{\pm}0.10$, ***p<0.001) within skin tissue of CD4+CD25+Foxp3+ Treg cell that's activated by XS-E dosage, thereby discovering that there is an effect of suppressing proliferation and viability of Th2 cell, eosinophils, mast cell and inflammatory cell. Upon examining cells permeated with H&E and toluidine blue staining technique, thickness of epidermis and mast cell's permeation decreased, and the result of examining the distribution of CCR 3+ eosinophils within ALN showed that it's level fell down to that of wild type (normal group, NC/Nga-WT). By such results, it is suggested that XS-E is highly effective on atopic dermatitis, and it is considered that continued quantitative research and case study of clinical research such as effect of cell number in individual tissues or change of total cell number are necessary.

• Analytical Science and Technology
• /
• v.30 no.5
• /
• pp.221-225
• /
• 2017

Thioctic acid is a vitamin-like antioxidant which is prepared as tablets and injection. The Korean Pharmacopoeia (KP XI) contains monograph for the quality control of raw thioctic acid using ultra-violet visible spectrophotometry and its formulations using high performance liquid chromatography (HPLC). In British Pharmacopoeia 2013 (BP2013), another HPLC method is used for the assay test of thioctic acid material. For the international harmonization, we present an HPLC method for quantitation of thioctic acid in both raw material and tablets. Method validation was performed to determine linearity, precision, accuracy, system suitability, and robustness. The linearity of calibration curves in the desired concentration range was high ($r^2=0.9995$), while the RSDs for intra- and inter-day precision were 0.93 ~ 1.26 % and 1.40 ~ 1.76 %, respectively. Accuracies ranged from 98.13-100.00 %. Since the system suitability, intermediate-precision and robustness of the assay were satisfactory, this method will be a valuable addition to the Korean Pharmacopoeia (KP XI).

• Preventive Nutrition and Food Science
• /
• v.2 no.2
• /
• pp.83-88
• /
• 1997

Anthocyanin pigments of purple sweet potato roots (Ipomoea batatas L.) were extracted with 0.5% TFA (Trifluoroacetic acid) in 95% EtOh, and further isolated an purified by Amberlite XAD-7 and ODS column chromatography, and final preparative HPLC. Among nine anthocyanins isolated, the structure of three major anthocyanins were identified as 3-O-(6-O-trans-caffeyl)-2-O-(6-O-trans-caffeylglucopyranosyl)-$\beta$-D-glucopyranosyl-5-O-($\beta$-D-glucopyranosyl)-peonidin, 3-O-(6-O-trans-caffeyl)-2-O-(6-O-trans-feruloyl-glucopyranosyl)-$\beta$-D-glucopyranosyl-5-O-($\beta$-D-glucopyranosyl)-peonidin, and 3-O-(6-O-trans-caffeyl)-2-O-(6-O-p-hydroxylbenzoylglucopyranosyl)-$\beta$-D-glucopyranosyl)-peonidin, by using UV-visible absorption spectra, $^1$H-NMR and FAB-MS analysis.

• Korean Journal of Remote Sensing
• /
• v.24 no.6
• /
• pp.535-549
• /
• 2008

Vicarious calibration for the satellite sensor relies on simulated TOA (Top-of-Atmosphere) radiances over various targets. In this study, TOA visible radiance was calculated over ocean targets which are located in five different regions over the Indian and Pacific ocean, and its possible use for the satellite sensor calibration was examined. TOA radiances are simulated with the 6S radiative transfer model for the comparison with MODIS/Terra and SeaWiFS measurements. Geometric angles and sensor characteristics of the reference satellites were taken into account for the simulation. AOT (Aerosol Optical Thickness) from MODIS/Terra, pigment concentrations from Sea WiFS, and ozone amount from OMI measurements were used as inputs to the model. Other atmospheric input parameters such as surface wind and total column water vapor were taken from NCEP/NCAR reanalysis data. The 5-day averaged radiances over all targets show that the percent differences between simulated and observed radiances are within about ${\pm}5%$ in year 2005, indicating that the calculated radiances are in good agreement with satellite measurements. It has also been shown that the algorithm can produce the SeaWiFS radiances within about ${\pm}5%$ uncertainty range. It has been suggested that the algorithm can be used as a tool for calibrating the VIS bands within about 5% uncertainty range.