21 research outputs found
๋ชจ๋ฐ์ผ ์์ด๋งฅ์ค ์์คํ ์์ ์ธ์ ์ ๊ฐ์ญ ์ํ๋ฅผ ์ํ ์ฑ๋ ์ถ์
In orthogonal frequency division multiplexing
based wireless system, a pilot signal is often
employed to estimate channel state information
(CSI). However, the received pilot signal is
interfered by other cell interference in multi-cell
environments. We consider the estimation of CSI by
utilizing orthogonal preambles and channel
correlation.Seoul R&BD Progra
Preamble-Assisted Channel Estimation in OFDM-based Wireless Systems
Accurate channel state information (CSI) is
indispensable for the use of channel-adaptive transmission
techniques, but it may not easily be achievable near the cell
boundary in cellular environments. This paper considers the
improvement of CSI estimation accuracy in OFDM-based
wireless packet transmission systems by exploiting the
preamble signal as well as the pilot signal. The CSIs
respectively estimated from the received preamble and pilot
signal are combined according to the channel correlation
between the preamble and the pilot signaling. The combining
weight is analytically determined to minimize the mean
squared error. When multiple antennas are employed for
interference cancellation, the CSI of interference channels
can also be estimated in a similar manner. The proposed
scheme is applied to the mobile-WiMAX system to verify the
effectiveness. Simulation results show that the proposed
scheme is quite effective near the cell boundary.This work was in part supported by the IT R&D
program of MKE/IITA (2008-F-007-01, Intelligent
Wireless Communication Systems in 3 Dimensional
Environment)
Adaptive Grouping MMSE Channel Estimation in OFDM-Based Wireless Systems
In this paper, we design an minimum meansquare
error (MMSE)-type channel estimation scheme in
orthogonal frequency division multiplexing-based wireless
systems. By using the averaged channel frequency response
(CFR) of pilot symbols in a group as a representative CFR ,
the proposed MMSE channel estimator can reduce the
mean-square error (MSE) of channel estimation by achieving
the signal-to-noise ratio (SNR) gain without increasing the
computational complexity compared to conventional MMSE
channel estimator. The grouping size of pilot symbols is
optimized to minimize the MSE according to the channel
correlation characteristics. Finally, the performance of the
proposed channel estimation scheme is verified by computer
simulation.This work was in part supported by the IT R&D
program of MKE/IITA (2008-F-007-01, Intelligent
Wireless Communication Systems in 3 Dimensional
Environment)
o-Carboranylalkoxy-1,3,5-Triazine Derivatives: Synthesis, Characterization, X-ray Structural Studies, and Biological Activity
Morpholine- and bis(2-methoxyethyl)amine-substituted 1,3,5-triazine derivatives containing an alkoxy-o-carborane in the 6-position of the triazine ring were successfully synthesized. The molecular structures of the methoxy- and ethoxy-o-carboranyl-1,3,5-triazines were established by X-ray crystallography. In vitro studies showed that the methylene bridged morpholine- and bis(2-methoxyethyl)amine-substituted o-carboranyl-1,3,5-triazines accumulated to high levels in B16 melanoma cells and exhibited higher cytotoxicity than p-boronophenylalanine
Design and Implementation for the Electronic Parking Brake System Based on Operating System
Electronic Parking Brake(EPB) system is operated by Electronic Control unit(ECU). EPB system has been by replaced a traditional parking brake system, which is a mechanical device to be driven by a parking brake lever or foot pedal. EPB system is more convenient for the women and elderly. Interior design as well as space utilization has also been important recently. By using EPB system, it is possible to ensure more space in a vehicle. Also, EPB system provides better convenience and safety than the traditional system through the cooperative control of Electric Stability Program(ESP) or alone. In this paper, we propose methodology of software architecture design and function development for the EPB system based on software tools.1
Analysis of volatile organic compounds in exhaled breath for lung cancer diagnosis using a sensor system
UPLC-MS/MS-Based Profiling of Eicosanoids in RAW264.7 Cells Treated with Lipopolysaccharide
While both the pro- and anti-inflammatory effects of several eicosanoids have been widely studied, the degree of inflammation in cells that results from various eicosanoids has yet to be comprehensively studied. The objective of this study was to assess the effect of lipopolysaccharide (LPS) treatment on eicosanoid content in RAW264.7 cells. An Ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS)-based profiling method was used to analyze the eicosanoid contents of RAW264.7 cells treated with different LPS concentrations. The profiling data were subjected to statistical analyses, such as principal component analysis (PCA) and hierarchical clustering analysis. LPS treatment increased nitric oxide production and secretion of pro-inflammatory cytokines, such as tumor necrosis factor-ฮฑ and interleukin-6, in a concentration-dependent manner. In total, 79 eicosanoids were identified in the cells. RAW264.7 cells treated with different LPS concentrations were well differentiated in the PCA score plot. A heatmap was used to identify the eicosanoids that were up- or down-regulated according to the degree of inflammation and LPS concentration. Thirty-nine eicosanoids were upregulated and seven were down-regulated by LPS treatment in a concentration-dependent manner. Our novel UPLC-MS/MS technique can profile eicosanoids, and can evaluate the correlations between inflammation and eicosanoid metabolism
Cancer-specific cytotoxicity of pyridinium-based ionic liquids by regulating hypoxia-inducible factor-1ฮฑ-centric cancer metabolism
Owing to their unique properties and biological activities, ionic liquids (ILs) have attracted research interest in pharmaceutics and medicine. Hypoxia-inducible factor (HIF)โย 1ฮฑ is an attractive cancer drug target involved in cancer malignancy in the hypoxic tumor microenvironment. Herein, we report the inhibitory activity of ILs on the HIF-1ฮฑ pathway and their mechanism of action. Substitution of a dimethylamino group on pyridinium reduced hypoxia-induced HIF-1ฮฑ activation. It selectively inhibited the viability of the human colon cancer cell line HCT116, compared to that of the normal fibroblast cell line WI-38. These activities were enhanced by increasing the alkyl chain length in the pyridinium. Under hypoxic conditions, dimethylaminopyridinium reduced the accumulation of HIF-1ฮฑ and its target genes without affecting the HIF1A mRNA level in cancer cells. It suppressed the oxygen consumption rate and ATP production by directly inhibiting electron transfer chain complex I, which led to enhanced intracellular oxygen content and oxygen-dependent degradation of HIF-1ฮฑ under hypoxia. These results indicate that dimethylaminopyridinium suppresses the mitochondria and HIF-1ฮฑ-dependent glucose metabolic pathway in hypoxic cancer cells. This study provides insights into the anticancer activity of pyridinium-based ILs through the regulation of cancer metabolism, making them promising candidates for cancer treatment