• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.158-161
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• 1989

This paper describes the AR model of EMG signal during maximum voluntary contraction. By comparing the AR coefficients and the reflection coefficients of the AR model with the median frequency of power spectrum, it if proved that muscle fatigue can be measured by the AR and the reflection coefficients. In the estimation procedure of AR model parameter, the auto-correlation method is superior to the covariance method, and it is determined that the optimal order is six. As the muscle becomes fatigue, the median frequency of power spectrum is declined, and the AR coefficient [$a_1$ ] and the reflection coefficient [$k_1$ ] are also decreased. Therefore the muscle fatigue can be measured by the AR parameter.

• 대한의용생체공학회:의공학회지
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• 제10권1호
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• pp.11-16
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• 1989

This paper describes the AR model of EMG signal during maximum voluntary contraction. By comparing the AR coefficients and the reflection coefficients of the AR model with the median frequency of power spectrum, it is proved that muscle fatigue can be measured by the AR and the reflection coefficients. In the estimation procedure of AR model parameter, the autocorrelation method is superior to the covariance method, and it is determined that the optimal order is six. As the muscle becomes fatigue, the median frequency of power spectrum is declined, and the AR coefficient [$a_1$] and the reflection coefficient [$k_1$] are also decreased. Therefore the muscle fatigue can be measured by the AR parameter.

• 한국전기전자재료학회논문지
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• 제14권9호
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• pp.773-778
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• 2001

In this dissertation the results of the combined experimental and theoretical studies designed to understand and predict the spatial growth and transport coefficients for electrons in SF$_{6}$ and SF$_{6}$-Ar mixtures have described. The ionization and attachment coefficients in pure SF$_{6}$ and SF$_{6}$-Ar mixtures have been calculated over the range of 10$_{6}$ molecule and for Ar atom proposed by other authors. The transport coefficients for electrons in (0.2%)SF$_{6}$-Ar and (0.5%)SF$_{6}$-Ar mixtures were measured by time-of-flight method, and the electron energy distribution function and the parameters of the velocity and the diffusion were determined by the variation of the collision cross-sections with energy. The results obtained in this work will provide valuable information on the fundamental haviors of electrons in weakly ionized gases and the role of electron attachment in the choice of better gases and unitary gas dielectrics or electro negative components in dielectric gas mixtures. gas mixtures.

• Communications for Statistical Applications and Methods
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• 제3권2호
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• pp.77-83
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• 1996

This paper is concerned with an estimation problem for the AR(1) process $Y_t, t=0, {\pm}1, {\cdots}$with time carying autoregressive coefficient, where coefficient itself is also stochastic process. Attention is directed to the problem of finding a consistent estimator of ${\Phi}$, the mean level of autoregressive coefficient. The asymptotic distribution of the resulting consistent estimator of ${\Phi}$, is them discussed. We do not assume any time series model for the time varying autoregressive coefficient.

• Wind and Structures
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• 제31권3호
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• pp.255-267
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• 2020

A systematic set of low-speed wind tunnel experiments was performed at Re = 6.5×10⁴ and 1.1×10⁵ to study the mean wind loading experienced by surface-mounted finite-height square prisms for different aspect ratios, incidence angles, and boundary layer thicknesses. The aspect ratio of the prism was varied from AR = 1 to 11 in small increments and the incidence angle was changed from α = 0° to 45° in increments of 1°. Two different boundary layer thicknesses were used: a thin boundary layer with δ/D = 0.8 and a thick boundary layer with δ/D = 2.0-2.2. The mean drag and lift coefficients were strong functions of AR, α, and δ/D, while the Strouhal number was mostly influenced by α. The critical incidence angle, at which the prism experiences minimum drag, maximum lift, and highest vortex shedding frequency, increased with AR, converged to a value of α_c = 18° ± 2° once AR was sufficiently high, and was relatively insensitive to changes in δ/D. A local maximum value of mean drag coefficient was identified for higher-AR prisms at low α. The overall behaviour of the force coefficients and Strouhal number with AR suggests the possibility of three flow regimes.

• 한국경영과학회지
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• 제37권1호
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• pp.29-43
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• 2012

We design a DEA-AR model using multiple regression analysis with new methods which limit weights. When there are multiple input and single output variables, our model can be used, and the weights of input variables use the regression coefficient and coefficient of determination. To verify the effectiveness of the new model, we evaluate the efficiency of the Regional Corporations in Korea. Accordance with statistical analysis, it proved that there is no difference between the efficiency value of the DEA-AR using AHP and our DEA-AR model. Our model can be applied to a lot of research by substituting DEA-AR model relying on AHP in the future.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.628-631
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• 2004

A tetrafluoromethane$(CF_4)$ is most useful gas in plasma dry etching, because it has a electron attachment cross-section. therefor it is important to calculate transport coefficients like electron drift velocity, ionization coefficient, attachment coefficient, effective ionization coefficient. and critical E/N. The aim of this study is to get these transport coefficients for information of the insulation strength and efficiency of etching process. Electron transport coefficients in $CF_4+Ar$ gas mixture are simulated in range of E/N values from 1 to 250 [Td] at 300[K} and 1 [Torr] by using Boltzmann equation method. The results of this method can be important data to present characteristic of gas for plasma etching and insulation, specially critical E/N is a data to evaluate insulation strength of a gas. and is presented in this paper for various mixture ratios of $CF_4+Ar$ gas mixture.

• 대한기계학회논문집B
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• 제20권8호
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• pp.2637-2649
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• 1996

Flow characteristics and aerodynamic forces acting on an elliptic cylinder placed in a plane boundary layer were investigated experimentally. Four cylinder models with axis ratio(major axis to minor axis, AR=A/B) of 1, 2, 3, and 4 having the same equivalent diameter were used in this experiment. The Reynolds number based on the equivalent diameter $D_e$(=20mm) was 13,000. In the case of circular cylinder, regular vortex shedding occurs for the cylinder gaps larger than G/B=0.3 and is not almost related to the boundary layer thickness. But, for the elliptic cylinders, the vortex shedding frequency is increased with increasing the gap ratio (G/B) and the axis ratio (AR) of elliptic cylinders. The maximum drag coefficient acting on a circular cylinder is mainly affected by the boundary layer thickness. But, the elliptic cylinders(AR$\geq$2), except for the smaller gap G/B<0.2, show a nearly constant drag coefficient which is much smaller than that of a circular cylinder. The base pressure on the flat plate decreases with increasing the axis ratio(AR) of the elliptic cylinder. In the case of a circular cylinder, the base pressure has the minimum value at the gap ratio G/B=0.4, but it occurs at G/D=2 for elliptic cylinders. The mean velocity of the cylinder wake is quickly recovered at a small cylinder height ratio(H/$\delta$), but the turbulent intensity is rapidly recovered at a large cylinder height ratio(H/$\delta$). The effective wake region in the plane boundary layer is shrinkaged with increasing the axis ratio(AR) of elliptic cylinder. And the drag coefficient and streamwise turbulent intensity of the elliptic cylinder with AR=4 are less than half of those for the circular cylinder(AR=1).

• 한국전기전자재료학회논문지
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• 제14권2호
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• pp.169-174
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• 2001

The electron transport coefficients(the electron drift velocity, W, and the longitudinal and transverse diffusion coefficient, D$_{L}$ and D$_{T}$) in SiH$_4$-Ar mixtures containing 0.5% and 5.0% monosilane were calculated over the E/N range from 0.01 to 300 Td and over the gas pressure range 0.5, 1.0 and 1.5 Torr by the time-of-flight(TOF) method of the Boltzmann equation(BE.) and Monte-Carlo simulation(MCS). The electron energy distribution function in each SiH$_4$-Ar mixtures at E/N=10 Td and L=0.2 cm, which in equilibrium region in the mean electron enregy were compared.red.

• 전기학회논문지P
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• 제56권1호
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• pp.1-5
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• 2007

Study on the electron transport coefficient in mixtures of CF4 and Ar, have been analyzed over a range of the reduced electric field strength between 0.1 and 350[Td] by the two-term approximation of the Boltzmann equation (BEq.) method and the Monte Carlo simulation (MCS). The calculations of electron swarm parameters require the knowledge of several collision cross-sections of electron beam. Thus, published momentum transfer, ionization, vibration, attachment, electronic excitation, and dissociation cross-sections of electrons for $CF_4$ and Ar, were used. The differences of the transport coefficients of electrons in $CF_4$ mixtures of Ar, have been explained by the deduced energy distribution functions for electrons and the complete collision cross-sections for electrons. The results of the Boltzmann equation and the Monte Carlo simulation have been compared with the data presented by several workers. The deduced transport coefficients for electrons agree reasonably well with the experimental and simulation data obtained by Nakamura and Hayashi. The energy distribution function of electrons in $CF_4-Ar$ mixtures shows the Maxwellian distribution for energy. That is, $f({\varepsilon})$ has the symmetrical shape whose axis of symmetry is a most probably energy. The proposed theoretical simulation techniques in this work will be useful to predict the fundamental process of charged particles and the breakdown properties of gas mixtures. A two-term approximation of the Boltzmann equation analysis and Monte Carlo simulation have been used to study electron transport coefficients.