• Journal of Biomedical Engineering Research
• /
• v.8 no.2
• /
• pp.223-230
• /
• 1987

In this paper the harmonic degrees between $\alpha$ wave and $\beta$ wave in visual evoked potential are analyzed by the bicoherence. The bicoherence analysis is based on an AR model which provides significantly better resolution than that of Fourier transform. The analysis results of visual evoked pope ntial are compared with the analysis results of background EEC. From the comparison results it is found that the harmonic degree of visual evoked potential is less than she harmonic degree of background EEG and the $\beta$ wave of visual evoke potential unlike the background EEC contains the non harmonic property of a wave more than the harmonic properity

• Journal of the Korean institute of surface engineering
• /
• v.36 no.2
• /
• pp.200-205
• /
• 2003

Thermoelectric p-type $Fe_{0.98}$ $Mn_{ 0.02}$$Si_2$ bulk specimens have been produced by mechanical alloying and consolidation by vacuum hot pressing. The subsequent isothermal annealing was not able to fully transform the mestastable as -milled powders into the $\beta$ $-FeSi_2$ phase, so that the obtained matrix consisted of not only thermoelectric semiconducting $\beta$-FeSi$_2$ but also some residual, untransformed metallic $\alpha$ $- Fe_2$$Si_{ 5}$ and $\varepsilon$-FeSi mixtures. Interestingly, $\beta$ - $FeSi_2$ was more easily obtained in the low density specimen when compared to the high density specimen. The oxidation at 700 and $800^{\circ}C$ in air led to the phase transformation of the above described iron - silicides and the formation of a thin silica surface layer.

• Bulletin of the Korean Mathematical Society
• /
• v.60 no.6
• /
• pp.1555-1566
• /
• 2023

A Hilbert space operator A ∈ B(H) is a generalised n-projection, denoted A ∈ (G-n-P), if A^*n = A. (G-n-P)-operators A are normal operators with finitely countable spectra σ(A), subsets of the set $\{0\}\,{\cup}\,\{\sqrt[n+1]{1}\}.$ The Aluthge transform à of A ∈ B(H) may be (G - n - P) without A being (G - n - P). For doubly commuting operators A, B ∈ B(H) such that σ(AB) = σ(A)σ(B) and ${\parallel}A{\parallel}\,{\parallel}B{\parallel}\;{\leq}\;{\parallel}{\tilde{AB}}{\parallel},$ ${\tilde{AB}}\;{\in}\;(G\,-\,n\,-\,P)$ if and only if $A\;=\;{\parallel}{\tilde{A}}{\parallel}\,(A_{00}\,{\oplus}\,(A_0\,{\oplus}\,A_u))$ and $B\;=\;{\parallel}{\tilde{B}}{\parallel}\,(B_0\,{\oplus}\,B_u),$ where A₀₀ and B₀, and A₀ ⊕ A_u and B_u, doubly commute, A₀₀B₀ and A₀ are 2 nilpotent, A_u and B_u are unitaries, A^*n_u = A_u and B^*n_u = B_u. Furthermore, a necessary and sufficient condition for the operators αA, βB, αà and ${\beta}{\tilde{B}},\;{\alpha}\,=\,\frac{1}{{\parallel}{\tilde{A}}{\parallel}}$ and ${\beta}\,=\,\frac{1}{{\parallel}{\tilde{B}}{\parallel}},$ to be (G - n - P) is that A and B are spectrally normaloid at 0.

• Journal of The Korean Association For Science Education
• /
• v.21 no.3
• /
• pp.516-528
• /
• 2001

In the educational study, the measure of EEG(brain waves) can be useful method to study the functioning state of brain during learning behaviour. This study investigated the changes of neuronal response according to four times repetition of audio-visual learning. EEG data at the prefrontal$(Fp_{1},Fp_{2})$ were obtained from twenty subjects at the 8th grade, and analysed quantitatively using FFT(fast Fourier transform) program. The results were as follows: 1) In the first audio-visual learning, the activities of $\beta_{2}(20-30Hz)$ and $\beta_{1}(14-19Hz)$ waves increased highly, but the activities of $\theta(4-7Hz)$ and $\alpha$ (8-13Hz) waves decreased compared with the base lines. 2). According to the repetitive audio-visual learning, the activities of $\beta_{2}$ and $\beta_{1}$ waves decreased gradually after the 1st repetitive learning. And, the activity of $\beta_{2}$ wave had the higher change than that of $\beta_{1}$ wave. 3). The activity of $\alpha$ wave decreased smoothly according to the repetitive audio-visual learning, and the activity of $\theta$ wave decreased radically after twice repetitive learning. 4). $\beta$ and $\theta$ waves together showed high activities in the 2nd audio-visual learning(once repetition), and the learning achievement increased highly after the 2nd learning. 5). The right prefrontal$(Fp_{2})$ showed higher activation than the left$(Fp_{1})$ in the first audio-visual learning. However, there were not significant differences between the right and the left prefrontal EEG activities in the repetitive audio-visual learning. Based on these findings, we can conclude that the habituation of neuronal response shows up in the repetitive audio-visual learning and brain hemisphericity can be changed by learning experiences. In addition, it is suggested once repetition of audio-visual learning be effective on the improvement of the learning achievement and on the activation of the brain function.

• Journal of Pharmaceutical Investigation
• /
• v.31 no.3
• /
• pp.151-160
• /
• 2001

The purpose of this study is to investigate the interaction of progesterone with various cyclodextrins (CDs) in the aqueous solution and in solid state, and finally to formulate a parenteral aqueous formulation. CDs used were ${\alpha}-$, ${\beta}-$, and ${\gamma}-CD$, $2-hydroxypropyl-{\beta}-CD$ (HPCD), sulfobutyl $ether-{\beta}-CD$ (SBCD), $dimethyl-{\beta}-CD$ (DMCD) and $trimethyl-{\beta}-CD$ (TMCD). The solubility studies of progesterone were performed in the presence of various CDs as a function of concentration or temperature. The solubility of progesterone increased in the rank order of ${\alpha}-CD$ < ${\beta}-CD$ < ${\gamma}-CD$ < TMCD$ < HPCD < DMCD < SBCD. Addition of SBCD (200 mg/ml) in water increased the aqueous solubility $(9.36\;{\mu}g/ml)$ about 3,200 times, and lowering the temperature facilitated the solubilization of progesterone. However, the addition of HPCD and SBCD in 20:80 (v/v) polyethylene glycol 300-water and propylene glycol-water cosolvents markedly decreased the solubility of progesterone, compared with solubilizing effects in water. Physical mixtures and solid dispersions of progesterone with HPCD or SBCD were prepared, and evaluated by differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), near IR spectroscopy and dissolution studies. By DSC and IR studies, it was found that progesterone was dispersed in HPCD in monotectic state and dissolved rapidly from both solid dispersions. Based on solubility studies, new aqueous progesterone fonnulations (5 mg/ml) containing SBCD (200 mg/ml) could be prepared and did not form precipitates even after 2 months at $4^{\circ}C$. The solution was transparent when mixed with normal saline and 5% dextrose injection at 1: 1, 1:10 and 1:20 (v/v) even after 7 days. Permeation rates of progesterone through a cellulose membrane from 20% PEG 300 solution $(50\;{\mu}g/ml)$ containing HPCD or SBCD were compared with oily formulation. Permeation of progesterone from oily formulation did not occur up to 8 hr, but aqueous formulations showed fast permeation rates from early stage of permeation study. The addition of HPCD or SBCD retarded the permeation rates of progesterone with the increase of CD concentrations, suggesting the possibility of a controlled absorption from the site administered intramuscularly. These results demonstrate that it is feasible to develop a new progesterone parenteral aqueous injection (5 mg/ml) using SBCD.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.11
• /
• pp.1914-1922
• /
• 2008

In this paper, examined characteristics of EEG(electroencephalogram) variation when the stimulation was given to lung-wan(CV12), Shin-gwol(CV8) and Gwan-won(CV4) which were some of the acupuncture point, through indirect moxibustion and No stimulation. The EEG signals were measured before the stimulation, during the stimulation, and 1 hour after the stimulation. The measured time domain data were converted to the frequency domain data FFT(Fast Fourier Transform) and frequency power spectrum. Then the $\alpha,\beta,\delta$, and $\theta$ waves were analyzed for variation to the amplitude of vibration according to the stages of stimulation.

• Journal of Microbiology and Biotechnology
• /
• v.19 no.9
• /
• pp.951-959
• /
• 2009

Most, if not all, Basidiomycetes mushrooms have biologically active polysaccharides showing potent antitumor activity with immunomodulating properties. These polysaccharides have various chemical compositions and belong primarily to the $\beta$-glucan group. In this study, the crude water-soluble polysaccharide HEF-P, which was obtained from the fruiting body of Hericium erinaceus by hot water extraction and ethanol precipitation, was fractionated by DEAE-cellulose and Sepharose CL-6B column chromatographies. This process resulted in four polysaccharide fractions, named HEF-NP Fr I, HEF-NP Fr II, HEF-AP Fr I, and HEF-AP Fr II. Of these fractions, HEF-AP Fr II was able to upregulate the functional events mediated by activated macrophages, such as production of nitric oxide and expression ofcytokines (IL-1${\beta}$ and TNF-${\alpha}$). The molecular mass of HEF-AP Fr II was estimated by gel filtration to be 13 kDa. Its structural characteristics were investigated by a combination of chemical and instrumental analyses, including methylation, reductive cleavage, acetylation, Fourier transform infrared spectroscopy (FT-IR), and gas chromatography-mass spectrometry (GC-MS). Results indicate that HEF-AP Fr II is a low-molecular-mass polysaccharide with a laminarin-like triple helix conformation of a ${\beta}$-1,3-branched-${\beta}$-1,6-glucan.

• Journal of Physiology & Pathology in Korean Medicine
• /
• v.28 no.6
• /
• pp.674-682
• /
• 2014

The purpose of this study was to identify the effect of applying oriental music therapy and reliability of electroencephalogram(EEG) equipment. The study was approved by the critical trial judge committee from ${\bigcirc}{\bigcirc}$(IRB No. 2013-07) university. In order to measure test-retest reliability for 15 subjects, EEG for same participants were measured using same method mentioned above after 2 hours from the first measurement. Same provider implemented to each person at same time. Firstly, EEG was measured for 5 minutes after the subject with attached electrodes sat on chair comfortably for 10 minutes. Then, the subject was given mental stress using the four fundamental arithmetic operations for 5 minutes, and measured EEG for another 5 minutes. After that the subject sat on the chair comfortably listening oriental medicine music therapy for 5 minutes, and EEG was measured for 5 minutes again. There was no side effect regarding music therapy reported. Raw data, which was measured in each step, were converted through FFT(fast fourier transform) and analyzed after divided into certain frequency including ${\alpha}$ wave, ${\beta}$ wave, ${\theta}$ wave, immersion wave, stabilization wave, sef100 wave, and sef95 wave. Data were analyzed using wilcoxon signed rank test, Intraclass correlation coefficient(ICC), repeated measures ANOVA with the SPSS program. In test-retes method, there were significantly differences in ${\alpha}$ wave, ${\beta}$ wave, immersion wave, stability wave, ${\theta}$ wave, sef100 wave, sef95 wave. ICC has shown a high degree of reliability that it was ${\alpha}$ wave .877, ${\beta}$ wave .855, ${\gamma}$ wave .895, immersion wave .897, stability wave .816, ${\theta}$ wave .904, sef100 wave .910, sef95 wave .776. Also, there was a statistically significant difference in ${\alpha}$ wave after applying oriental music therapy. Based on these results, it is considered that average of the channel EEG and application of oriental music therapy would be practiced by increase of sample size using this machine.

• Proceedings of the KIEE Conference
• /
• 1995.07c
• /
• pp.1190-1192
• /
• 1995

Poly(vinylidene fluoride)(PVDF) is one of the most studied polymers in the latest date. The interest in PVDF lies in its remarkable piezoelectric and pyroelectric properties. Also, PVDF has at least four known crystalline structures(; they are referred to as the ${\alpha},\;{\beta},\;{\gamma}\;and\;{\alpha}_p$ phase or forms II, I, III and $IV_p$). In this study, the manufactured PVDF thin film through vapor deposition method had form II(; the glass at $70^{\circ}C$). This thin film was investigated by x-ray diffraction(XRD), Fourier Transform Infrared(FT-IR) spectroscopy and Differential Thermal Analysis(DTA). XRD and FT-IR indicate crystallization forms from the glass at $70^{\circ}C$ into form II.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.3 no.3
• /
• pp.264-271
• /
• 2014

Virtual synchronous generator (VSG) in single-phase to interface distributed renewable energy resources is investigated in this paper. Mathematical models and numerical analysis are utilized to illustrate the features of the VSG. Enhanced control strategy is presented to ensure the performance of the VSG. Besides, a second order generalized integer (SOGI) is employed to calculate the instantaneous output power of the VSG in virtual ${\alpha}{\beta}$ frame. By the means of a phase-locked loop based scheme, the VSG can seamlessly transform between islanded and grid-tied modes, which can meet the requirements of micro-grid. At last, the validation and the proposed approach are verified by the simulated results using PSCAD/EMTDC.