• Journal of the Korean Society for Aviation and Aeronautics
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• v.5 no.1
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• pp.31-50
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• 1997

A new variable wing that can be swept back and forward synchronously were developed to enhance the aerodynamic and stability characteristics of a high speed airplane. The configuration of the new variable wing changes in such a way that inner part of the wing sweeps forward and outer part of the wing sweeps backward, the shift of aerodynamic center of the wing is small, therfore the static margin that is required for the stability of a airplane is not affected. In this study, various configurations of wing models by combined swept back and forward were designed and a wind tunnel tests were conducted to investigate the aerodynamic characteristics of these variable wings. The experimental results showed that the variable wing by combined swept back and forward has no effect on the pitching moment coefficient affecting on an aircraft stability margin and enhance the aerodynamic characteristics for a given approach angle of attack.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1571-1581
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• 2016

A novel method is proposed to construct the voltage stability boundary of power system considering different Reactive Power Control Mode (RPCM) of Doubly-Fed Induction Generator (DFIG) Wind Power Plant (WPP). It can be used for reflecting the static stability status of grid operation with wind power penetration. The analytical derivation work of boundary search method can expound the mechanism and parameters relationship of different WPP RPCMs. In order to improve the load margin and find a practical method to assess the voltage security of power system, the approximate method of constructing voltage stability boundary and the critical points search algorithms under different RPCMs of DFIG WPP are explored, which can provide direct and effective reference data for operators.

• Transactions on Electrical and Electronic Materials
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• v.16 no.6
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• pp.293-302
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• 2015

Degraded data stability, weaker write ability, and increased leakage power consumption are the primary concerns in scaled static random-access memory (SRAM) circuits. Two new SRAM cells are proposed in this paper for achieving enhanced read data stability and lower leakage power consumption in memory circuits. The bitline access transistors are asymmetrically gate-underlapped in the proposed SRAM cells. The strengths of the asymmetric bitline access transistors are weakened during read operations and enhanced during write operations, as the direction of current flow is reversed. With the proposed hybrid asymmetric SRAM cells, the read data stability is enhanced by up to 71.6% and leakage power consumption is suppressed up to 15.5%, while displaying similar write voltage margin and maintaining identical silicon area as compared to the conventional memory cells in a 15 nm FinFET technology.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1191-1194
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• 2005

The effects of addition of $D_2$ to conventional gases on the discharge characteristics were investigated in this work with the aim of improving the voltage margin, the wall charge and the jitter. The addition of an extremely small gas-inlet amounts of $D_2$ increased the number of electrons which improves the $Xe^{\ast}$ density and $Xe_2^{\ast}$ density. As a result, the voltage margin, the jitter and the wall charge increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.11
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• pp.3639-3648
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• 1996

The effect of 15% pinched diffuser in a centrifugal air compressor with a cascade airfoil diffuser on the aerodynamic performance is investigated using a numerical approach. The commercial CFD code for three-dimensional, turbulent, compressible flow fields is executed for various mass flow rates at a design speed which can be obtained as long as the calculation succeeds. The pinched diffuser is found to help improve the instability of flow within vaneless diffuser space, especially the reverse flow near shroud, and to change both stall/surge line and choking line to increase the surge margin. It is also found to generate more favorable increase of static pressure in diffuser region, and to increase the resulting pressure ratio and efficiency.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1689-1691
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• 2003

In this paper, we investigated the relationships between the position of bus electrode and discharge characteristics in ac PDP with VGA resolution. The double bus electrode lines at the edge of ITO electrode are placed in order to lower the firing voltage. As a result, static margin and dynamic margin for the PDP with double bus electrodes was about 10V lower than conventional type.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.133-136
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• 2000

A new Op-Amp output buffer is presented for driving large-size LCD panels. The proposed Op-Amp is designed by combining a common source and a common drain amplifier to have a high slew rate and to minimize the quiescent current. The proposed circuits are simulated in a high-voltage 0.6${\mu}{\textrm}{m}$ CMOS process, dissipates only 20${\mu}{\textrm}{m}$ static current, and have 83dB open-loop DC gain and 60$^{\circ}$phase margin.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.313-319
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• 2006

This paper addresses improving the voltage stability limit of interface flow between two different regions in an electric power system using the Static Synchronous Series Compensator (SSSC). The paper presents a power flow analysis model of a SSSC, which is obtained from the injection model of a series voltage source inverter by adding the condition that the SSSC injection voltage is in quadrature with the current of the SSSC-installed transmission line. This model is implemented into the modified continuation power flow (MCPF) to investigate the effect of SSSCs on the interface flow. A methodology for determining the interface flow margin is simply briefed. As a case study, a 771-bus actual system is used to verify that SSSCs enhance the voltage stability limit of interface flow.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.11
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• pp.963-969
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• 2005

An advanced method of Relaxed Static Stability (RSS) is utilized for improving the aerodynamic performance of modem version supersonic jet fighter aircraft. The flight control system utilizes RSS criteria in both longitudinal and lateral-directional axes to achieve performance enhancements and improve stability. The T-50 advanced trainer employs the RSS concept in order to improve the aerodynamic performance and the flight control law in order to guarantee aircraft stability, The T-50 longitudinal control laws employ the dynamic inversion and proportional-plus-integral control method. This paper details the design process of developing longitudinal control laws for the RSS aircraft, utilizing the requirement of MIL-F-8785C. In addition, This paper addresses the analysis of aircraft characteristics such as damping, natural frequency, gain and phase margin about state variables for longitudinal inner loop feedback design.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.7
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• pp.341-348
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• 2002

Recently, an SVC(Static Var Compensator) was installed at Seo-daegu substation in order to maintain the voltage level and reserve stability margin of the Korean Power System. This paper deals with the development of the simulation model for the Seo-daegu SVC. As a simulation platform, PSCAD/EMTDC is adopted and library components for the SVC are developed. The model includes detailed control system functions of Seo-daegu SVC. In order to verify the developed model, simulation results are compared with the TNA test performed by ABB. The results show a good agreement of the developed model with the real system.