• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.635-642
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• 2000

We have been derived theoretically the SER's and CLP's of Wireless ATM (WATM) cells employing an OFDM/16QAM modulation scheme in wireless channel modeled as a frequency selective Rayleigh fading channel. The amount of the performance improvement of WATM- OFDM/16QAM systems adopting various coding techniques has been evaluated. In frequency selective Rayleigh fading channel, considering CLP : $10^{-3}$ as a criterion, it is observed that the performance improvement of about 14 dB is obtained in terms of $E_b/N_o$ by employing an OFDM scheme. It is also confirmed that convolutional coding technique gives better performance than the other coding techniques. Especially, when the convolutional codes are adopted to WATM-OFDM/16QAM systems, voice transmission services are sufficiently available with 5 dB of $E_b/N_o$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1359-1367
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• 2000

A new coherent detection scheme with data based channel estimation (DBCE) for CDMA/BP(staggered burst pilot in parallel) channel structure is proposed. Because the pilot burst initiates DBCE operation periodically it is shown to be remarkably stable to Gaussian noise and Doppler shift with proper parameter settings. In our own system parameter setting, there is a negligible loss(0.068 dB) in $E_{b}/N_{o}$ by the introduction of the burst pilot. When compared with an ideal coherent detection, the required $E_{b}/N_{o}$ on Doppler shift corresponding to the speed of 160Km/H is degraded less that 2.0 dB. the burst pilot can be implemented without complexity even though some extra correlators are needed for DBCE. This improvement is superior to the previously coherent CDMA detectors with external or internal pilot.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.11
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• pp.1665-1670
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• 2006

The objective of this research was to provide the characterization and method for producing anti-E. coli O157:H7 antibodies in egg-laying hens and to determine if the antibody can restrain the proliferation of E. coli O157:H7 in-vitro. Selected antigenic fractions (whole cell, outer membrane protein and lipopolysaccharide (LPS)) from E. coli O157:H7 were injected to hens in order to produce anti-E. coli O157:H7 antibodies. The immune response and the egg yolk antibodies of laying hens against the whole cell, outer membrane protein and LPS antigens were monitored by ELISA. The level of antibodies against whole cell antigen monitored through ELISA sharply increased after the initial immunization, and it was found to be maximum on day 49 however, the level was maintained up to day 70. Antibodies (5 mg/ml) directed against the whole cell inhibited E. coli proliferation 10-13 times more than outer membrane protein or LPS. The antibody response against the whole cell antigens appeared to have higher activity in restraining the proliferation of E. coli O157:H7 than antibody against outer membrane protein or LPS. Results reflected that increasing the IgY's in the egg yolk could prevent greater economic losses due to human and animal health from pathogenic bacteria i.e. E. coli O157:H7.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.534-540
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• 2006

Thin films of $V_2O_3$, $VO_2$, and $V_2O_5$ were obtained from a single precursor solution through post-annealing processes under different annealing conditions. As annealed in air, the deposited films became $V_2O_5$ with orthorhombic crystal structure, while they were $V_2O_3$ and $VO_2$ with rhombohedral and monoclinic crystal structure as annealed in vacuums with base pressure of $1{\times}10^{-6}$ Torr and with 10 mTorr $O_2$ pressure, respectively. Electrical and optical measurements indicated that the $V_2O_5$ and $VO_2$ films are semiconducting, while the $V_2O_3$ films are metallic at room temperature. Chromium doping in $VO_2$ resulted in a decrease of the resistivity and changed the conduction type from n-type to p-type. 10% Cr-doped $VO_2$ films were found to have orthorhombic crystal structure, which is different from that of the undoped $VO_2$. Spectral features in the optical absorption spectra of all the films were interpreted as the transitions involving O 2p and V 3d bands. The crystal-field splittings between $t_{2g}$ and $e_g$ states of the V 3d bands are estimated to be about 1.5 and 1.0 eV for $V_2O_5$ and $VO_2$, respectively.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.46-50
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• 2004

Compounds of $Y_{3-x}Ce_{x}Fe{5}O_{12}$(x=0.0, 0.1, 0.2, and 0.3) were prepared using the sol-gel method. The XRD measurements show that these samples have only a single phase of the garnet structure regardless of the amount of Ce substitution. The lattice constants of x = 0.0 and x = 0.3 were found to be a$_0$ = 12.3758 ${\pm}$0.0005 ${\AA}$ and 12.4062 ${\pm}$0.0005 ${\AA}$, respectively. The lattice constant increases linearly with increasing Ce concentration. The saturation magnetization was not changed flirty, with increasing Ce concentration, but coercivity decreased form 18.3 Oe to 5.8 Oe as x increased form x = 0.0 to x = 0.1. Mossbauer spectra of $Y_{3-x}Ce_{x}Fe{5}O_{12}$ were measured at various absorber temperatures from 13 K to Neel temperature. The Mossbauer spectra were fitted by least-squares technique with two subpatterns of Fe sites in the structure and corresponding to the 16a and 24d site. The temperature dependence of the magnetic hyperfine field in $^{57}$/Fe nuclei at the tetrahedral 240 and octahedral 16a sites were analyzed based on the Neel theory of ferrirnagnetism. The result of the Debye temperatures indicated that the inter-atomic binding force for the 24d site was larger than that for the 16a site.

• The Korean Journal of Pesticide Science
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• v.11 no.2
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• pp.72-81
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• 2007

Quantitative structure-activity relationships (QSARs) on the pre-emergency herbicidal activity and reactivity of a series of new O,O-dialkyl-1-phenoxyacetoxy-1-methylphosphonates (S) analogues against seed of cucumber (Cucumus Sativa) were discussed quantitatively using 2D-QSAR and HQSAR methods. The statistical values of HQSAR model were better than that of 2D-QSAR model. From the frontier molecular orbital (FMO) interaction between substrate molecule (S) and $BH^+$ ion (I) in PDH enzyme, the electrophilic reaction was superior in reactivity. From the effect of substituents, $R_2$-groups in substrate molecule (S) contributed to electrophilic reaction with carbonyl oxygen atom while X, Y-groups contributed to nucleophilic reaction with carbonyl carbon atom. And the influence of X,Y-groups was more effective than that of $R_2$-groups. As a results of 2D-QSAR model (I & II) and atomic contribution maps with HQSAR model, the more length of X, Y-groups is longer, the more herbicidal activity tends to increased. And also, the optimal ${\epsilon}LUMO$ energy, $({\epsilon}LUMO)_{opt.}$=-0.479 (e.v.) of substrate molecule is important factor in determining the herbicidal activity. It is predicted that the herbicidal activity proceeds through a nucleophilic reaction. From the analytical results of 2D-QSAR and HQSAR model, it is suggested that the structural distinctions and descriptors that contribute to herbicidal activities will be able to applied new herbicide design.

• Applied Biological Chemistry
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• v.46 no.3
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• pp.246-250
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• 2003

In order to isolate antibacterial substances from the rhizome of Zingiber mioga Roscoe, the ethanol extracts was fractionated according to the activity against Bacillus subtilis, B. cereus and Staphylococcus aureus. Three antibacterial substances were isolated and purified by column chromatography and recrystallization. Compounds I and III showed activity against all the tested bacterias and compound II exhibited the activity against B. subtilis and B. cereus S. aureus. Compound I was examined antimicrobial activity against B. subtilis, B. cereus and S. aureus by optical density using Bioscreen C. Compound I showed strong growth inhibition at 10 ppm on B. subtilis and B. cereus for 72 hrs, and at 25 ppm on S. aureus. On the basis of spectrometric studies including $1^H-NMR$, ${13}^C-NMR$, DEPT, IH-lH COSY, HMQC, HMBC and IR, compounds I, II and III were identified as $(E)-8{\beta}(17)-epoxylabd-12-ene-15,16-dial\;(C_{20}H_{30}O_3,\;MW=318)$, galanolactone $(C_{20}H_{30}O_3\;MW=318)$ and galanal A $(C_{20}H_{30}O_3,\;MW=318)$, respectively. These results are the first reports on the isolation of $(E)-8{\beta}(17)-epoxylabd-12-ene-15,16-dial, galanolactone and galanal A from the rhizome of Zingiber mioga.

• Fisheries and Aquatic Sciences
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• v.24 no.12
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• pp.428-436
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• 2021

The aim of this study was to isolate and identify secondary metabolites from Sonchus brachyotus and evaluate their antioxidant and anti-inflammatory activities. In this study, we isolated three flavonoids from a 70% EtOH extract by Medium Pressure Liquid Chromatography (MPLC) and prep-High-Performance Liquid Chromatography (HPLC). To evaluate the biological activities (antioxidant and anti-inflammatory) of these flavonoids, their in vitro inhibitory activities against lipopolysaccharide (LPS)-induced reactive oxygen species (ROS) generation, nitric oxide (NO) production, and prostaglandin E₂ (PGE₂) secretion were determined. We successfully identified three flavonoids, namely luteolin (1), luteolin-7-O-β-D-glucoside (2), and luteolin-7-O-β-D-glucuronide (3) by spectral analyses. Luteolin (1) at 20 ㎍/mL inhibited ROS generation, NO production, and PGE₂ secretion by 48.6%, 61.28% and 12.10%, respectively, and luteolin-7-O-β-D-glucoside (2) inhibited NO and PGE₂ generation by 67.03% and 20.82%, respectively. Luteolin (1) and luteolin-7-O-β-D-glucoside (2) showed similar anti-inflammatory activities; however, luteolin (1) was observed to be a stronger antioxidant. Besides antioxidant and anti-inflammatory activities, S. brachyotus extract containing luteolin (1) and luteolin-7-O-β-D-glucoside (2) is considered to possess diverse biological activities. The results indicate that S. brachyotus is an edible medicinal plant, which is believed to be significant resource of functional foods.

• Journal of Applied Biological Chemistry
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• v.57 no.2
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• pp.165-170
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• 2014

The stems of Viburnum erosum were extracted with 80% MeOH. The concentrated extract was partitioned with EtOAc, n-BuOH, and $H_2O$. From the EtOAc and n-BuOH fractions, four compounds were isolated through the repeated $SiO_2$, octadecyl silica gel, and Sephadex LH-20 column chromatographies. Based on NMR, MS, and IR spectroscopic data, the chemical structures were determined as betulinic aldehyde (1), koaburside (2), (6R,7E,9R)-9-hydroxymegastigma-4,7-dien-3-one-9-O-${\beta}$-D-glucopyranoside (3), and byzantionoside B (4). All the compounds were isolated for the first time from the stems of Viburnum erosum.

• Journal of the Korean Ceramic Society
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• v.38 no.8
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• pp.698-704
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• 2001

Doped ceria의 전기전도도는 도핑 원소의 종류와 양에 큰 의존성을 가지고 특정 조성에서 최대 전도도 값을 가지며 높은 dopant 농도에서는 전기전도도는 감소한다. 이런 현상은 dopant와 산소 빈자리 사이의 회합 형성과 관련이 있다고 알려져 있다. 그러나 Gd 이온이 도핑된 ceria의 경우 주된 회합종이 (2G $d_{Ce}$ $V_{o}$ )인지 (G $e_{Ce}$ $V_{o}$ ) 인지는 명확하게 알려져 있지 않다. 본 연구에서는 회합분포가 전기전도도에 미치는 영향을 연구하기 위해 결함의 회합종과 분포가 다른 3가지 경우에 대해서 시뮬레이션을 행하였다. 분자동력학법을 이용하여 다양한 온도와 다른 회합분포의 경우에 대해 산소 확산계수가 계산되어졌으며, 계산된 산소 확산계수는 실험적으로 결정된 bulk 전도도로부터 얻어진 산소 확산계수와 비교되어졌다. 그 결과 (2G $d_{Ce}$ $V_{o}$ )와 (G $e_{Ce}$ $V_{o}$ ) 회합이 공존하며 이들이 통계학적으로 이항 분포를 가지는 경우가 실험적으로 보고된 값과 가장 일치하는 결과를 얻을 수 있었다.