• Bulletin of the Korean Chemical Society
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• 제18권4호
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• pp.385-389
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• 1997

We report on the development of a new method to control the coverage of a metal film prepared with immersion method. An Sb species in solution adsorbed irreversibly at an open circuit potential (∼0.2 V) as an oxygenous Sb(Ⅲ) on a clean Au electrode, and the adsorbates showed voltammetric features in the potential range from 0.1 V to - 0.4 V. The full coverage of the Sb adsorbates was ∼0.45. On the contrary, the Sb species in solution did not adsorb at all on iodine-covered Au electrode surfaces, when the iodine coverages were more than 0.25. As the iodine coverage decreased below 0.25, however, the irreversible adsorption of Sb took place and the coverage of Sb increased accordingly. This electrochemical behavior has been interpreted as the penetration of the adsorbing Sb species in solution through open spaces among the iodine adlattices of coverages less than 0.25. With the manipulation of the iodine coverage, the controllable range of Sb coverage was from 0 to 0.45, i.e. the full coverage of Sb. In addition, the reversible deposition of Sb on an iodine-saturated Au electrode with voltammetric scan has been observed, which is contrasted with the adsorptive behavior of Sb on the clean Au electrode.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.231-234
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• 2003

This paper presents a novel high frequency transformer linked full-bridge type soft-switching phase-shift PWM control scheme DC-DC power converter, which can be used as power conditioner fur small-scale fuel cell power generation system. Using full-bridge soft-switching DC-DC converter topology makes possible to use low voltage high performance MOSFETs to achieve high efficiency of the power conditioner. A tapped inductor filter is implemented in the proposed soft-switching converter topology to achieve soft-switching PWM constant high frequency operation for a wide load variation range. to minimize circulating and idling currents without using additional resonant circuit and auxiliary power switching devices. The practical effectiveness of the proposed soft-switching DC-DC converter is verified in laboratory level experiment with 1 kW 100kHz breadboard setup using power MOSFETs. Actual efficiency of 94-96$\%$ is obtained for the wide load range

• Wind and Structures
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• 제36권2호
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• pp.91-103
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• 2023

Tuned liquid dampers (TLDs) are increasingly being used as efficient dynamic vibration absorbers to mitigate wind-induced vibration in super high-rise buildings. However, the damping characteristics of screens and the control effectiveness of actual structures must be investigated to improve the reliability of TLDs in engineering applications. In this study, a numerical TLD model is developed using computational fluid dynamics (CFD) and a simulation method for achieving the coupled vibration of the structure and TLD is proposed. The numerical results are verified using shaking table tests, and the effects of the solidity ratio and screen position on the TLD damping ratios are investigated. The TLD control effectiveness is obtained by simulating the wind-induced vibration response of a full-scale structure-TLD system to determine the optimal screen solidity ratio. The effects of the structural frequency, damping ratio, and wind load amplitude on the TLD performance are further analyzed. The TLD damping ratio increases nonlinearly with the solidity ratio, and it increases with the screens towards the tank center and then decreases slightly owing to the hydrodynamic interaction between screens. Full-scale coupled simulations demonstrated that the optimal TLD control effectiveness was achieved when the solidity ratio was 0.46. In addition, structural frequency shifts can significantly weaken the TLD performance. The control effectiveness decreases with an increase in the structural damping ratio, and is insensitive to the wind load amplitude within a certain range, implying that the TLD has a stable damping performance over a range of wind speed variations.

• 제어로봇시스템학회논문지
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• 제2권4호
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• pp.306-311
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• 1996

This paper discusses the maintenance of the water level of steam generators at its programmed value. The process, the water level of a steam generator, has the nonminimum phase property. So, it causes a reverse dynamics called a swell and shrink phenomenon. This phenomenon is severe in a low power condition below 15 %, in turn makes the start-up of the power plant too difficult. The control algorithm used here incorporates a pole-assignment scheme into the minimum variance strategy and we use a parallel adaptation algorithm for the parameter estimation, which is robust to noises. As a result, the total control system can keep the water level constant during full power by locating closed-loop poles appropriately, although the process has the characteristics of high complexity and nonlinearity. Also, the extra perturbation signals are added to the input signal such that the control system guarantee persistently exciting. In order to confirm the control performance of a proposed pole-assignment self-tuning controller we perform a computer simulation in full power range.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
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• pp.1584-1587
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• 2008

We proposed a technique controlling continuously pretilt angle in full range with high process margin. The proposed method is characterized by tuning thickness of heterogeneous polyimide (PI) layer that homeotropic PI is mixed with planar PIs.

• JSTS:Journal of Semiconductor Technology and Science
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• 제10권4호
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• pp.282-291
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• 2010

This paper presents a full-CMOS transmitter and receiver for VDSL2 systems. The transmitter part consists of the low-pass filter, programmable gain amplifier (PGA) and 14-bit DAC. The receiver part consists of the low-pass filter, variable gain amplifier (VGA), and 13-bit ADC. The low pass filter and PGA are designed to support the variable data rate. The RC bank sharing architecture for the low pass filter has reduced the chip size significantly. And, the 80 Msps, high resolution DAC and ADC are integrated to guarantee the SNR. Also, the transmitter and receiver are designed to have a wide dynamic range and gain control range because the signal from the VDSL2 line is variable depending on the distance. The chip is implemented in 0.25 ${\mu}m$ CMOS technology and the die area is 5 mm $\times$ 5 mm. The spurious free dynamic range (SFDR) and SNR of the transmitter and receiver are 67.5 dB and 41 dB, respectively. The power consumption of the transmitter and receiver are 160 mW and 250 mW from the supply voltage of 2.5 V, respectively.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.1487-1506
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• 2009

A long-term field experiment of the selected stabilization methods(Cover system, full range and upper range treatment) was conducted to reduce the heavy metal mobility in farmland soil which was contaminated by heavy metals around abandoned mine site. Field experiments were established on the contaminated farmland with the wooden plate and filled with treated soil, which was mixed with lime stone and steel reforming slag except on control plot. Soil samples were collected and analyzed during the experiment period(about 4 months) after the installation of the plots. Field demonstration experiments results showed that the cover system and the full range treatment of the selected stabilization methods applied to the application ratio of lime stone 5% and steel refining slag 2% were effective for immobilizing heavy metal components in contaminated farmland soil.

• Journal of Advanced Marine Engineering and Technology
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• 제16권4호
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• pp.102-112
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• 1992

The three-phase full(6-pulse) bridge controlled rectifier is one of the most widely used types of solid-state converters in DC drive applications for higher performance. In most of the previous designs, the gate control circuits of the converter have been designed with analog method which can be easily affected by noise. Nowdays with advances of microelectronics and power electronics, microprocessor and pheripal LSIs are increasingly used for eliminating this problems. In this paper, a novel general-purpose microprocessor -based firing system and control scheme for a three-phase controlled rectifier bridge has been developed and tested. Using the phase relations between ${\Delta}$-Y transformer in power operation part, gate pulse of the converter is generated with real time process so that microprocessor may share its time to control algorithms efficiently. The firing angle of the converter is smoothly controlled in the range of 0 $^{\dirc}$ to 180$^{\dirc}$ with a fast respone and a constant open loop gain, even for the case where the converter is fed by a weak AC system of unregulated frequency. The hardware and software control circuit implementation built around a 80286 microprocessor is discussed, and the experimental results are given. This scheme uses less hardware components and has higher dynamic performance in variable speed DC drive applications.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.364-367
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• 2001

ZVS Full-bridge converter is widely used in medium power level(1-3kW). ZVS can be designed within a limited load range and ZVS failure at light load condition is assumed to be acceptable within the given efficiency and thermal constraints. However, unbalanced ZVS resonant energy caused by dc blocking capacitor may alleviate the switching loss problem at light load condition. ZVS resonant energy is unbalanced by do blocking capacitor. This problem causes loss and heat concentration of a switch leg, In this paper, this problem is analyzed, and a novel control method is proposed to solve the problem.

• Journal of Power Electronics
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• 제19권1호
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• pp.201-210
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• 2019

This paper proposes a multimode hybrid control strategy that can achieve zero-voltage switching of primary switches and zero-current switching of secondary rectifier diodes in a wide input voltage range for full-bridge LLC resonant converters. When the input voltage is lower than the rated voltage, the converter operates in Mode 1 through the variable-frequency control strategy. When the input voltage is higher than the rated voltage, the converter operates in Mode 2 through the VF and phase-shift control strategy until the switching frequency reaches the upper limit. Then, the converter operates in Mode 3 through the constant-frequency and phase-shift control strategy. The secondary-side diode current will operate in the discontinuous current mode in Modes 1 and 3, whereas it will operate in the boundary current mode in Mode 2. The current RMS value and conduction loss can be reduced in Mode 2. A detailed theoretical analysis of the operation principle, the voltage gain characteristics, and the realization method is presented in this paper. Finally, a 500 W prototype with 100-200 V input voltage and 40 V output voltage is built to verify the feasibility of the multimode hybrid control strategy.