• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.9-15
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• 2004

The most shortcoming of metalhalide lamps is what the instant restarting cannot be realized when the arc tube is in the hot condition. The discharge starting voltage of arc tube in the hot condition is much higher than in the cold condition. Therefore it takes about five minutes to restart the metalhalide lamps, that is to say, it is possible to start when the pressure and the temperature are decreased. But, if the lamp is restarted in the hot condition, we must supply the high voltage pulse with 20[kV] at the both electrode of lamp. The proposed electronic ballast is consist of a electromagnetic interference(EMI) filter, a power factor correction(PFC) circuit, a flyback converter, a half-bridge inverter, and a high voltage igniter circuit. By this composition we can start/restart the lamp with the voltage 20[kV], even if the lamp is in the hot condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3567-3573
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• 2009

This research proposed a dashpot type mount design using MR fluids, and investigated experimentally the influence of the design parameters of the dashpot MR fluid mount, which affect the damping forces of the dashpot MR fluid mount. In order to observe the influence, the dashpot MR fluid mount which have the different effective length and the core structure is manufactured. The variations of the resistance forces according to different effective lengths of the magnetic pole of MR fluid mount, along which magnetic field is defined, was investigated. It was founded that the resistance forces from the MR mount decreased with increased input frequencies, while increased with increased applied electric current intensities. Nevertheless, there is no appreciable change in the resistance forces with respect to the effective length variations of the magnetic pole of MR fluid mount.

• The Journal of the Acoustical Society of Korea
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• v.14 no.2
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• pp.40-49
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• 1995

Application of the filtered-x LMS adaptive filter to active noise cancellation requires to estimate the transfer charactersitics between the output and the error signal of the adaptive canceler. In this paper, we derive the filtered-x adaptive noise cancellation algorithm and analyze its convergence behavior when the acoustic noise consists of multiple sinusoids. The results of the convergence analysis of the filtered-x LMS algorithm indicate that the effects of the parameter estimation inaccuracy on the convergence behavior of the algorithm are characterized by two distinct components : Phase estimation error and estimated gain. In particular, the convergence is shown to strongly affected by the accuracy of the phase response estimate. Simulation results are presented to support the theoretical convergence analysis.

• Transactions on Electrical and Electronic Materials
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• v.11 no.3
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• pp.126-129
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• 2010

(1-X) $(Na_{0.5}K_{0.5})NbO_3-X$ $K_4CuNb_8O_{23}$ (NKN-X KCN) ceramics were produced using the conventional solid state sintering method, and their sinterability and electric properties were investigated. The density, dielectric constant (${\varepsilon}_r$), piezoelectric constant $d_{33}$, electromechanical coupling factor $k_p$ and mechanical quality factor $Q_m$ value of the NKN ceramics depended upon the KCN content and the sintering temperature. In particular, the KCN addition to the NKN greatly improved the mechanical quality factor $Q_m$ value. The ceramic with X = 2.0 mol% sintered at $1,150^{\circ}C$ possesses the optimum properties (${\varepsilon}_r=241$, $d_{33}=78$, $k_p=0.34$ and $Q_m=1,121$). These results indicate that the ceramic is a promising candidate material for applications in lead free piezoelectric transformer and filter materials.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1169-1177
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• 1995

Barium nitrate and yittrium nitrate were dissolved into distilled water. Titaium hydroxide precipitated from titanium chloride with NH4OH was dissolved into nitric acid. Each aqueous solution was mixed for 12 hr in the composition of Ba1-xYxTiO3 (x=0.1∼0.6) and the concentration of mixed solution was 0.1 mol/ι. The mixed solution was sprayed with an ultrasonic atomizer and carried into an electric furnace which was kept at 900∼1000$^{\circ}C$ and pyrolyzed. Pyrolyzed powders were collected on the glass filter with vacuum pump. Aqueous Mn solutiion was added into the synthesized powders, mixed with ultrasonic vibration and sintered at 1300∼1400$^{\circ}C$. Synthesized powders were characterized with SEM, XRD, DT-TGA, and BET. Microsture and resistivity of sintered body were investigated with SEM and multimeter. The results of this experiment were as follows; 1) Yittrium dooped BaTiO3 powders were synthesized above 950$^{\circ}C$. 2) The average particle sizes of powders from BET specific surface area and SEM were 0.045$\mu\textrm{m}$, 0.046$\mu\textrm{m}$ respectively. The particle size distribution was narrow in the range of 0.1∼1.0$\mu\textrm{m}$ from SEM. 3) Room temperature resistivity and pmax/pmin of 0.4 mol% Y doped specimen which was sintered at 1375$^{\circ}C$ were 102∼3 (Ω$.$cm) and 102∼3 respectively. 4) Room temperature resistivity and pmax/pmin of 0.4 mol% Y and 0.04 at% Mn added specimen which was sintered at 1375$^{\circ}C$ were 102∼3 (Ω$.$cm) and 106∼7 respectively. 5) Grain growth was inhibited with addition of Y2O3 and enhanced in addition of Mn by 0.05 atm%.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.233-239
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• 2012

The harmonic frequency occurred in a power system causes errors and failures of equipments such as motors, and an unnecessary power consumption. The fundamental countermeasure for the harmonic frequency is to eliminate the cause of the harmonic frequency. This paper describes about making the device to figure out the cause in real time, verifying the operation of the device, and utilizing it to various power quality measurements. The power usually has the line frequency between 45Hz and 66Hz. In this research, the number of the harmonic frequencies which can be analysed inside the 2.8kHz bandwidth, the filter bandwidth of ADE7880, is 2800/f, and the maximum is 2800/45 = 63. The maximum order of the harmonic frequency in Korea, which has the line frequency of 60Hz, was measured as 2800/60 = 46th. Also, the accuracy of the voltage, current, and power measurement had the error within 0.1%, confirming that it is very precise.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.4
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• pp.22-29
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• 2002

Usually, much harmonics are included and cause harmonic loss of motor, torque pulsation, electro-magnetic noise and shock etc. by switching function of inverter when drive induction motor variableness inside. It applied partial resonant Buck converter and three phase voltage type SPWM inverter circuit to induction motor driving system in this paper that see to solve such problem. Changed operation condition variously to do input current of circuit that propose sine-wave by unit power factor almost and capacitor supplied bringing back to life voltage by power supply arranging properly assistance diode and electric power switching. Power factor and efficiency improved as that minimize variation of input at power supply voltage polarity reverse by that add voltage reversal function. Also, by using output filter, reduced harmonic of output line to line voltage components, and introduce state space analysis and forecast operation of rectifier. Such all items confirmed validity through simulation and an experiment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.503-506
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• 2001

There are four factors for patient monitoring : electrocardiography, blood pressure, temperature and respiration. While there are a lot of studies of E.C.C (electro-cardiography) monitoring system in the world, the studies of Respiratory system are not enough and leave much to be desired in the country. In this paper, we developed a respiratory system with the electrical impedance change of the lungs depending on the breath. Using the same electrode, we can monitor E.C.C and Respiration simultaneously, so we can monitor a patient's no-breathing state due to the central nerve paralysis in the emergency room easily. In this monitoring system, the analog part was made separated from the digital part for reducing power source noise and protecting patient from electric shock. The analog part consists of the several parts a high-frequency sine-wave generator, all amplifier for amplifying any impedance change signal, an analog processing part for rectifying and filtering. And the digital parts consists of three parts an AD convertor for converting analog signal to digital signal, digital filter, and a digital part for digital signal processing. This system's merits are using the same electrode with E.C.C and developing the multiple patient monitoring system easily.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.495-501
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• 2020

The various sintered samples comprising of 72 wt% (Al₂O₃) : 28 wt% (SiO₂) based ceramics were fabricated using a colloidal processing route. The phase analysis of the ceramics was performed using an X-ray diffractometer (XRD) at room temperature confirming the presence of Al₂O₅Si and Al_5.33Si_0.67O_9.33. The surface morphology of the fracture surface of the different sintered samples having different sizes of grain distribution. The resistive and capacitive properties of the three different sintered samples at frequency sweep (1 kHz to 1 MHz). The contribution of grain and the non-Debye relaxation process is seen for various sintered samples in the Nyquist plot. The ferroelectric loop of the various sintered sample shows a slim shape giving rise to low remnant polarization. The excitation performance of the sample at a constant electric signal has been examined utilizing a designed electrical circuit. The above result suggests that the prepared lead-free ceramic can act as a base for designing of dielectric capacitors or resonators.

• Composites Research
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• v.16 no.3
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• pp.58-67
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• 2003

To perform the realtime strain and fracture monitoring of the smart composite structures, two optical fiber sensor systems are proposed. The two types of the coherent sources were used for fracture signal detection - EDFA with FBG and EDFA with Fabry-Perot filter. These sources were coupled to EFPI sensors imbedded in composite specimens. To understand the characteristics of matrix crack signals, at first, we performed tensile tests using surface attached PZT sensors by changing the thickness and width of the specimens. This paper describes the implementation of time-frequency analysis such as short time Fourier transform (STFT) and wavelet transform (WT) for the quantitative evaluation of fracture signals. The experimental result shows the distinctive signal features in frequency domain due to the different specimen shapes. And, from the test of tensile load monitoring using optical fiber sensor systems, measured strain agreed with the value of electric strain gage and the fracture detection system could detect the moment of damage with high sensitivity to recognize the onset of micro-crack fracture signal.