• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1172-1174
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• 2003

A resonant type voltage source and power device and a control method using Pulse Density Modulation(PDM) power control and Pulse Width Modulation(PWM)voltage control for plasma sterilization are described. For the stability of discharge in the generating tube, it is desirable that the peak apply voltage is constant. The PDM power control is employed for sustaining the voltage constant at any generating tube input power. Moreover, to avoid the influence of input AC voltage fluctuation etc., PWM voltage control with generating tube peak voltage feedback is used. Both functions were confirmed by the experiment with inverter and generating tube. The effect of input synchronous PDM method for input current stabilizing is confirmed also.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.6 no.6
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• pp.32-41
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• 1992

In this paper, an advanced Pulse Width Modulation Inverter strategy for driving a variable-speed induction motor is introduced. A switching pattern making use of the near-proportionality of voltage and frequency in AC machines operating with constant flux was computed. At low magnitudes and ow frequencies of the fundamental, many more harmonics are eliminated than at high magnitudes and frequencies. In order to keep the inverter switching frequency constant over the output frequency range, the chopping frequency is diminished as the frequency of the fundamental increases. Using these modulation strategy, the harmonics components of PWM inverter are efficiently eliminated.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.397-401
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• 2003

A resonant type voltage source and power device and a control method using Pulse Density Modulation(PDM) power control and Pulse Width Modulation(PWM) voltage control for plasma sterilization are described. For the stability of discharge in the generating tube, it is desirable that the peak apply voltage is constant The PDM power control is employed for sustaining the voltage constant at any generating tube input power. Moreover, to avoid the influence of input AC voltage fluctuation etc., PWM voltage control with generating tube peak voltage feedback is used. Both functions were confirmed by the experiment with 6.5[㎑], 1.8[㎾] inverter and generating tube. The effect of input synchronous PDM method for input current stabilizing is confirmed also.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.563-565
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• 1993

This paper describes ozone concentration and discharge characteristics in flowing $O_2$ with variation of Re at high voltage nozzle(HVN). HVN type ozonizer is equipped with ten nozzle. The important conclusions obtained from this paper are as follows. For constant pulse width(Pw) and pulse frequency(Pf) the more Re increases, the higher corona onset voltage(Vc) rise. Vc is inversely proportional to Pw and Pf. Ozone concentration($O_{3con}$) increases with less Re for constant Pw and Pf. $O_{3con}$ increases with less Pw. $O_{3con}$ is proportional to Pf.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1627-1633
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• 2018

A constant voltage AC-DC converter based on digital assistant technology is proposed in this paper, which has rapid dynamic response capability. The converter operates in the PFM (Pulse Frequency Modulation) mode. According to the load state, the compensation current produced by the digital compensation module was injected into the CS pin to adjust the switching pulse width dynamically and improve the dynamic response. The control chip is implemented based on NEC $1{\mu}m$ 5V/40V HVCMOS process. A 5V/1.2A prototype has been built to verify the proposed control method. When the load jumps from idle to heavy, the undershoot time is only 7.4ms.

• Korean Journal of Plant Resources
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• v.11 no.3
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• pp.319-325
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• 1998

The developmental changes occuring in the secondary xylem of Aristolochia manshuriensis Komarov have been studied in different ages of vine stems. A. manshuriensis possesses typical storeyed cambium comprising both vertically elongated fusiform initials and almost isodiametric ray cell initials. Stems of A. manshuriensis have wide rays that make the secondary xylem appear dissected as other vine types. The length of vessel member and fiber remained relatively constant throughout the secondary growth. However, vessel diameter increases with the increasing age of stem till the cell reaches their maximum limit and later more or less stabilize in diameter while number of vessel per $\textrm{mm}^2$ is vice versa. Width and relative proportion of ray to axial elements gradually increased with the increasing age of stem and later remained relatively constant.

• Progress in Superconductivity
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• v.4 no.2
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• pp.144-147
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• 2003

We investigated superconducting property of ($Mg_{1-x}$$Zn_{x}$)$CNi_3$ (x=0,0.03, 0.06, 0.09, 0.12, 0.15, and 0.18) sample where Mg is substituted with Zn. The samples were synthesized us ins the solid state reaction method under As atmosphere. X -ray diffraction spectra show that the $MgCNi_3$ structure is maintained up to x=18. With increasing x, the lattice constant (or the Ni-Ni distance) decreases. Magnetic susceptibility measurement shows that $T_{c}$ decreases systematically with x and becomes ～2K at x =0.18. Surprisingly, the transition width remains sharp (～0.3K). Under some assumptions, we estimate the coupling constant in the McMillan formula as a function of x which we interpret in terms of the BCS theory.y.y.y.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.63-72
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• 2006

The purpose of this raper is to address the negative impedance instability in DC/DC converters. We present the negative impedance instability of PWM DC/DC converters loaded by constant power loads (CPLs). An approach to design digital controllers for DC/DC converters Is presented. The proposed method, called Power Alignment control technique, is applied to DC/DC step-down choppers operating in continuous conduction or discontinuous conduction modes with CPLs. This approach uses two predefined state variables instead of conventional pulse width modulation (PWM) to regulate the output voltage. A comparator compares actual output voltage with the reference and then switches between the appropriate states. It needs few logic gates and comparators to be implemented thus, making it extremely simple and easy to develop using a low-cost application specific integrated circuit (ASIC) for converters with CPLs. Furthermore, stability of the proposed controllers using the small signal analysis as well as the second theorem of Lyapunov is verified. Finally, simulation and analytical results are presented to describe and verify the proposed technique.

• Journal of Korean Association for Spatial Structures
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• v.18 no.2
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• pp.121-128
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• 2018

The push-out tests have been conducted on the specimens which consist of the steel beam with U-shape section and the cap-type shear connectors with constant intervals. Existing equations for the evaluation of shear connector strength have been investigated on the basis of test results. The reinforcing bars for longitudinal reinforcement and the penetrative bars for transverse reinforcement didn't have much effect on the shear capacity of the cap-type shear connector. The larger the width of cap-type shear connector was profiled, the greater the shear strength turned. The shear capacities of cap-type shear connectors with constant intervals were evaluated on the basis of push-out test results, and those were possible to be determined with proper safety margin using the Eurocode 4. The slip capacity of cap-type shear connector was shown to exceed the limit value of 6mm for sufficiently ductile behavior.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.96-100
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• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].