• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.176-181
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• 2001

As the data rate between chip-to-chip gets high, the skin effect and load of pins deteriorate noise margin. With these, noise disturbances on the bus channel make it difficult for receiver circuits to read the data signal. This paper has proposed a new pre-emphasis driver circuit which achieves wide noise margin by enlarging the signal voltage range during data transition. When data is transferred from a memory chip to a controller, the output boltage of the driver circuit reaches the final values through the intermediate voltage level. The proposed driver supplies more currents applicable to a packet-based memory system, because it needs no additional control signal and realizes very small area. The circuit has been designed in a 0.18 ${\mu}m$ CMOS process, and HSPICE simulation results have shown that the data rate of 1.32 Gbps be achieved. Due to its result, the proposed driver can achieved higher speed than conventional driver by 10%.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.443-450
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• 2009

This paper deals with the design of decentralized controller for load-frequency control of interconnected power systems with superconducting magnetic energy storage units and Governor Dead Band Nonlinearity using Multi-Objective Evolutionary Algorithm. The superconducting magnetic energy storage unit exhibits favourable damping effects by suppressing the frequency oscillations as well as stabilizing the inter-area oscillations effectively. The proposed control strategy is mainly based on a compromise between Integral Squared Error and Maximum Stability Margin criteria. Analysis on a two-area interconnected thermal power system reveals that the proposed controller improves the dynamic performance of the system and guarantees good closed-loop stability even in the presence of nonlinearities and with parameter changes.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.89-91
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• 1995

This paper describes an extension or a pair or multiple load flow solutions and nose curve method developed for voltage stability analysis or AC power systems to AC/DC systems. In this approach the converters are regarded as voltage dependent loads. Assuming that the converters at the unstable (-mode) solution consume the same power equal to the power at the stable (+mode) solution, the unstable solutions or the nose curves arc determined. This method is very efficient since estimating voltage collapse point and voltage stability margin arc determined by a few iterations of multiple load flow solutions. Also the method has the advantages that since the structure or Jacobian matrix is same with that of AC load flow, modal analysis or voltage stability is readily applicable if desired.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.168-170
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• 2001

This paper presents the strategy of reactive power compensation which directly improves voltage stability. Voltage stability index that serves as an indirect assessment of voltage stability margin is derived from M.G.C.F. (Modified Generalized Curve Fit) algorithm incorporating load model. Weak buses are ranked by this stability index, and amounts of reactive power compensation are determined by function of reactive power and stability index. Using the proposed strategy, all load buses can be prevented from voltage collapse gradually. A simple illustrative example is given as well as simulation results obtained on 5 bus test system and 19 bus real power system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.10
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• pp.472-479
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• 2001

In order to prevent voltage collapse. this paper introduces the idea of the intelligent system and operating polices for a power system, then presents the results of voltage stability studies for that power system. The intelligent system includes a dedicated computer doing calculation and evaluation jobs and several intelligent relays serving as last guards to carry out the pre-set remedies. In the intelligent system, P-V curves are used to determine the operating margin from the current operating point to the maximum operating point, or the nose point. This paper suggests an operating guide for voltage stability of a power system. The effectiveness of location ad amount of load shedding for the different power load models are studied.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.8
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• pp.958-964
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• 1999

The distance in load parameter space to the closest saddle node bifurcation (CSNB) point provides the worst case power margin to voltage instability and the left eigenvector at CSNB identifies the most effective direction to steer the system to maximize voltage stability under contingency. This paper presents an improved direct method for computing CSNB: the order of nonlinear systems equations is reduced to about twice of the size of load flow equations in contrast to about three-times in Dobson's direct method; the initial guess for the direct method is computed efficiently and robustly by combined use of continuation power flow, a pair of multiple load flow solution with Lagrange interpolation. It is also shown that voltage stability may be enhanced significantly with shift of generations in the direction of the left eigenvector at CSNB.

• Proceedings of the KIEE Conference
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• 1994.11a
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• pp.45-47
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• 1994

The simulation of reactive power compensation in 5-bus and 25-bus system was conducted using transmission-line loss system identification method. Sensitivities of maximum load-power with respect to reactive power compensation was identified by the simulation. With sufficient reactive power compensation at the first voltage-collapsing load-bus, the first voltage collapse could be prevented until the next voltage-collapsing load-bus lost its voltage stability. And the total compensated reactive power at the first voltage-collapsing bus means reactive power margin of voltage collapse or distance to voltage collapse. This quantity can be useful for determining the size of compensating devices or the site to compensate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.900-907
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• 2013

Payload fairing(PLF) protects satellites and related equipment from the external environment. They are separated before the satellite separation. Payload fairing made of composite sandwich materials due to their considerable bending stiffness and strength-to-weight ratio. Payload fairing have compression, shear and bending load during the flight. In this study, To check the strength of PLF and connected part, structural test of PLF accomplished using an actuator and a fixture. Purpose of structural test is to verify the strength of PLF in force of separation spring and combination structural load applied. Test result shows that the PLF have an acceptable margin of safety for the combination structural load and force of separation spring.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.687-691
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• 2011

In this paper, we design an 8-bit eSuse OTP (one-time programmable) memory in consideration of EM (electro-migration) and eFuse resistance variation based on a $0.18{\mu}m$ generic process, which is used for an analog trimming application. First, we use an external program voltage to increase the program power applied an eFuse. Secondly, we apply a scheme of precharging BL to VSS prior to RWL (read word line) activation and optimize read NMOS transistors to reduce the read current flowing through a non-programmed cell. Thirdly, we design a sensing margin test circuit with a variable pull-up load out of consideration for the eFuse resistance variation of a programmed eFuse. Finally, we increase program yield of eFuse OTP memory by splitting the length of an eFuse link.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.47-56
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• 2018

In this paper, the structural analysis of the Geostationary Korea Multi-Purpose Satellite-2 (GEO-KOMPSAT-2) tubing system is discussed, and the structural integrity of the tubing system is assessed by comparative analysis with the results of overseas partner AIRBUS. Securing structural reliability of the tubing system is a very important key element of the propulsion system of the GEO-KOMPSAT-2 satellite. Therefore, FE modeling of the propulsion tubing was carried out directly using the CAE program, and structural analysis was performed to evaluate the stress state under launch conditions. Hoop stress, axial stress, bending stress, and torsion stress were calculated according to diverse load conditions by using pressure stress analysis, thruster alignment analysis, sine qualification load analysis, and random qualification load analysis. From the results, the Margin of Safety (MoS) of the tubing system is evaluated, and we can verify the structural integrity of the tubing system when subjected to various launch loads.