• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.158-163
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• 2001

Current Source Inverter(CSI), operated in square wave mode, is more efficient thant the PWM CSI because of increased cost, greater complexity of control algorithm and substantial switching losses, EMI. But, the square wave output current of CSI, rich in low order harmonics produce motor torque ripples. Therefore, in this paper, describes active power filters for compensating square wave input current of current source induction motor. Also, notch filtering as compensation algorithm is employed. To confirm the validity of proposed system, PSIM simulation results are presented and discussed.

• Journal of the Korean Chemical Society
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• v.38 no.3
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• pp.234-240
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• 1994

Square-wave voltammetric behavior for uranium(VI)-cupferron complex was studied in 0.1 M acetate buffer solution(pH5.0). The optimum condition for square-wave voltammetric analysis of uranium was also investigated. The reduction of uranium(VI)-cupferron complex was found to be irreversible and only uranium(VI)-cupferron complex was adsorbed on the electrode surface during the deposition time. Detection limit of uranium(VI) was 7.9nM(2 ppb) where the deposition time was 30sec at -0.1 V vs. Ag/AgCl. The amount of uranium(VI)-cupferron complex adsorbed on the electrode surface was ${\Gamma}_{max} = (4.9{\pm}0.3){\times}10^{-10} mol{\cdot}cm^{-2}$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.605-612
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• 1994

The methods to determine the hydrodynamic coefficients for the fixed type artificial reefs which were constructed to control ecological system in coastal waters are compared and discussed by model test results. To calculate the wave forces, least square method show good agreement with the experimental results and more stability than maximum force component method or Fourier decomposition method. This modified least square method of weighting the square of measured force turned out to be the most feasible method for maximum force. Using the feasible method, hydrodynamic characteristics for artificial reefs on uniform slopes offshore and breaking zone were studied. They were properly related to Keulegan-Carpenter's number and found larger than previous results. Wave force coefficients for artificial reefs around breaking zone were distributed from 1.5 to 2.5, and the mean value was 2.0. Drag force components were more in evidence than inertia force in maximum force which is important parameter to evaluate stability for high-permeability structures. A formula for the calculation of the maximum force for artificial reefs design is proposed, using structural dimension, water particle velocity and Keulegan-Carpenter's number.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.10
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• pp.587-594
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• 2002

A low frequency square wave electronic ballast for the high intensity discharge(HID) lamps using fuzzy logic controller is developed. This electronic ballast consists a buck converter, a low frequency square wave full bridge inverter, a high voltage pulse generator for the HID lamp ignition, an over current protection circuit and an 8-bit microcontroller. The ballast system is operated on the constant current mode during the HID lamp start-up process and the system is operated on the constant power mode during steady state. Experimental results show that the fuzzy logic control operation is carried out successfully by the 8-bit microcontroller PIC16F877 In this electronic ballast system, in spite of the limited control bandwidth caused by low operating speed of the microcontroller, the good performance in the constant lamp current characteristic is obtained. Acoustic resonance of the HID lamps can be effectively avoided because the instantaneous In lamp power is fully constant due to the low frequency square wave drive.

• Archives of Pharmacal Research
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• v.27 no.1
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• pp.31-34
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• 2004

The electrochemical behavior of doxorubicin hydrochloride was investigated by cyclic voltammetry (CV) and square wave voltammetry (SWV). From CV and SWV studies of doxorubicin hydrochloride in the acetate buffers of various pH values, it was found that protons were involved in the reduction of the antibiotic at the $H^+/e^$- ratio at one ( $\DeltaEp/pH =-53 ∼ -61 mV at 23^{\circ}C$), proposing the electrochemical reduction of the quinone moiety in its anthraquinone aglycone. Its electrochemical behavior was pseudo-reversible in the acetate buffer of pH 3.5 by exhibiting the well-defined single cathodic and anodic waves and the ratio of $lp^a/lp^c$ at approximately one over the scan rates of 10∼100 mV/s. Fast and sensitive SWV showing a single peak of doxorubicin has been applied for its quantitative analysis using an acetate buffer of pH 3.5. A linearity was obtained when the peak currents (lp) were plotted against concentrations of doxorubicin in the range of $5.0\times10^{-7} M∼1.0\times10^{-5}$M with a detection limit of $1.0\times10^{-7}$ M.

• Journal of information and communication convergence engineering
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• v.18 no.2
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• pp.88-93
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• 2020

The IEEE 802.11p-based wireless access in vehicular environments (WAVE) [1] communication is a method used exclusively for wireless communication on the road. This technique enables information sharing not only among moving vehicles but also between vehicles and infrastructure [2]. As part of WAVE communication, data is transmitted to and from vehicles in motion; in this case, it is difficult to determine the channel accurately in an outdoor environment owing to the Doppler shift [3]. This paper proposes a new channel estimation scheme for enhancing the reception performance of the IEEE 802.11p-based WAVE system. The proposed technique obtains the initial channel value by estimating the least square in the time domain by inserting a pilot signal for channel estimation into the IEEE 802.11p virtual subcarrier. Subsequently, a least mean square algorithm is applied to the initial channel value to update the estimated channel value. The simulation results obtained using the proposed channel estimation technique confirm its remarkable efficiency.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.10a
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• pp.481-486
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• 1997

The interfacial shear stress is experimentally investigated for co-current air-water stratified flow in inclined rectangular channels having a length of 1854mm, width of 120mm and height of 40mm at almost atmospheric pressure. Experiments are carried out in several inclinations from $0^{\circ}\;up\;to\;10^{\circ}$. The local film thickness and the wave height are measured at three locations, i.e., L/H = 8,23, and 40. According to the inclination angle, the experimental data are categorized into two groups; nearly horizontal data group ($0^{\circ}\;{\leq}\;{\theta}\;{\leq}\;0.7^{\circ}$), and inclined channel data group ($0.7^{\circ}\;{\leq}\;{\theta}\;{\leq}\;10^{\circ}$). Experimental observations for nearly horizontal data group show that the flow is not fully developed due to the water level gradient and the hydraulic jump within the channel. For the inclined channel data group, a dimensionless wave height, $\Delta$h/h, is empirically correlated in terms of $Re_{G}$ and h/H. A modified root-mean-square wave height is proposed to consider the effects of the interfacial and wave propagation velocities. It is found that an equivalent roughness has a linear relationship with the modified root-mean-square wave height and its relationship is independent of the inclination.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.6
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• pp.472-477
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• 2013

This paper carried out the comparative analysis on ground impedance of a carbon block and a copper rod. Two types of grounding electrode were compared ; a carbon block (L : 1 m, ${\Phi}$ : 245 mm) buried at a depth of 0.8 m and a three-linked copper rod (L : 1 m, ${\Phi}$ : 10 mm) of equilateral triangles with 1 m spacing. Ground impedance depending on applied current source was evaluated by the application of a sine wave current with 60 Hz ~ 3.5 MHz, a fast-rise pulse with rising time of 200 ns, a standard lightning impulse of $8/20{\mu}s$ and a 600 Hz square wave. Ground impedance for both electrodes were almost the same value below 100 kHz, and increased rapidly afterwards. The maximum ground impedance appeared $400{\Omega}$ at around 1.5 MHz. Ground impedance of the carbon block was lower at the square wave and was higher at fast-rise pulse than that of the copper rod. Also, ground impedance as ages showed no difference for the last 8 months. From the results, it is likely that ground performance for both electrodes shows no difference against commercial frequency and lightning impulse current, while the copper rod shows better performance against a fast-rise pulse with rise-time of a few hundred ns.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.2
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• pp.143-149
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• 2021

BLDC motors are getting better performance due to the improvement of material technology including high performance of permanent magnets, advancement of driving IC technology with high integration and high functionality, and improvement of assembly technology such as high point ratio. While having the advantage of such a square wave driven BLDC motor, interest in the design and development of a square wave driven BLDC permanent magnet motor and development of a position detection circuit and driver is increasing in order to more meet the needs of users. However, in spite of the cost and functional advantages due to reduced efficiency, switching loss and vibration, noise, etc., the application is somewhat limited. Therefore, in this paper, we study a position detection circuit that generates a sinusoidal signal in proportion to the magnetic flux of a BLDC motor rotor using a Hall Effect Sensor that generates a sinusoidal wave to increase the efficiency of the motor, reduce ripple, and drive a sinusoidal current with excellent speed and torque characteristics.

• The Research Journal of the Costume Culture
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• v.6 no.4
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• pp.13-25
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• 1998

This study focuses on the visual effects of various neckline-haristyle combinations on the perception of face image and type. The study employed a model with oval face and examined 35 combinations made up of five necklines and seven hairstyles. Looking at various face images depending upon different necklines, in case of round, V, boat square, and high necklines, long wave hair and medium wave hair produced a feminine image of marked individuality; long straight hair that covers the forehead and medium straight hair gave an image of charm and purity as well as an image of neatness; and long straight hair short cut hair showed an intellectual image. Regarding the perceptual type of face depending upon the different necklines of round, V, square, and high, the long straight hair covering the forehead and medium wave hair had the effect of an optical illusion that made the face look short and round; and short cut hair made the face line look distinct and the face look oval and slender.