• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.8
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• pp.1-9
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• 2009

In this paper, we describe DSSS transceiver development robust to jamming signals as an investigation of ECCM transceiver for UAV uplink. The jamming margin is 15dB or greater with the development target of transceiver because the jamming margin is more important than the transmission rate of data and the spreading code can be changeable. The rake receiver is applied to combine multipath components and turbo code which the coding gain is 7.2dB as a FEC. In this paper, the whole structure, design method and functional test result about the designed modem are described and a conclusion is made.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.112-117
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• 2007

In this paper, we focus on the total transmission power minimization problem for downlink beamforming multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems while ensuring each user's QoS requirement. Although the linear integer programming (LIP) solution we formulate provides the performance upper bound of the margin adaptive (MA) optimization problem, it is hard to be implemented in practice due to its high computational complexity. By regarding each user's equivalent channel gain as approximate independent values and using iterative descent method, we present a heuristic MA resource allocation algorithm. Simulation results show that the proposed algorithm efficiently converges to the local optimum, which is very close to the performance of the optimal LIP solution. Compared with existing space division multiple access (SDMA) OFDM systems with or without adaptive resource allocation, the proposed algorithm achieves significant performance improvement by exploiting the frequency diversity and multi-user diversity in downlink multiple-input single-output (MISO) OFDM systems.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.65-73
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• 2008

Retaining large stability margin is essential in designing a feedback control system to deal with the uncertainties inherently existing in the mathematical model and the control apparatus. The LQG controller in general loses the stability margin due to the embed Kalman filter. The performance of a control system called LTR with a DUOX structure(LTR/DOUX) to overcome the demerit of LQG controller is to be investigated from the responses in both the time and the frequency domain. The results indicated that the LTR/DOUX recovered the gain margin of 30dB approximately 20 times more than that of LQG/DOUX, resulting in a robust stable control system.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2589-2592
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• 2003

In this paper, a robust mixed H$_2$/H$\_$$\infty$/ output feedback control method is applied to the design of loop filter for PLL carrier phase tracking. The proposed method successfully copes with large S-curve slope uncertainty and a significant decision delay in the closed-loop that may exist In modern receivers due to a convolutional decoder or an equalizer. The objective is to design an output feedback controller which minimizes the H$_2$performance while satisfying the H$\_$$\infty$/ performance to guarantee the gain margin and phase margin for linear time invariant(LTI) polytopic uncertain systems. LMIs based approach is given to solve this problem. We can verify the H$\_$$\infty$/ performance satisfaction and minimize the phase detector error through the simulation result.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.675-677
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• 2004

This paper presents a nonlinear controller design for optical disk drive systems to improve anti-shock performance. The nonlinear anti-shock controller is added parallel to the original linear servo control loop. In the previous work, dead-zone nonlinear element is used for nonlinear controller and PID control method is used for linear controller. Although this strategy improves anti-shock performance, it has a narrow stability bound. In this paper, we propose dead-zone with saturation nonlinear element for the nonlinear controller. Since this nonlinear element improves stability margin, we can use higher gain of dead-zone than the controller with dead-zone only. In the linear controller design, we show that lead-lag control has improved stability margin over PID control. Numerical simulation results show that the proposed method can get better performance to the external shock than previously proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.9
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• pp.1605-1610
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• 2010

In this paper, the relative stability of magnetic bearing system for the flywheel energy storage is evaluated using both simulation and experimental analysis. We make the simulation model for the magnetic bearing flywheel system using the rigid body shaft model. According to international standard ISO 14839-3, We experimentally analyzed the relative stability of magnetic bearing system. Additionally using both the simulation model and experimental tests, Phase margin and Gain margin is acquired through Nyquist plot.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.161-167
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• 1993

This paper presents robustness properties of the Kalman Filter ad the associated LQG/LTR method for linear time-invariant systems having delays in both the state and output. A circle condition relating to the return difference matrix associated with the Kalman filter is derived. Using this circle condition, it is shown that the Kalman filter guarantees(1/2, .inf.) gain margin and .+-.60.deg. phase margin, which are the same as those for nondelay systems. However, it is shown that, even for minimum phase plants, the LQG/LTR method can not recover the target loop transfer function. Instead, an upper bound on the recovery error is obtained using an upper bound of the solution of the Kalman filter Riccati equations. Finally, some dual properties between output-delated system and input-delayed systems are exploited.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.11 no.2
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• pp.33-36
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• 2002

As patients have concerned the esthetics of dental restorations, the porcelain fused to metal restorations have gain their popularity due to their strength and esthetic appearance for many years. However, metal collar in subgingival level of porcelain fused to metal restoration often causes black shadows. Inadequately positioned metal collar causes plaque depositions, gingival inflammations, black shadows, and discolorations of margin area. Those problems can be avoided by a clear finishing line, well-fabricated provisional restorations with precise margin and fine polishing, collarless porcelain fused to metal restoration, and all ceramic restoration. In this case report, collarless porcelain fused to metal restoration was used to treat cervical discoloration from old restorations.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.6
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• pp.1-5
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• 2010

We propose an algorithm which can classify the system should use a PI controller, which have a weak high frequency attenuation characteristics near the critical frequency. To classify the system, we use a time delay element to calculate a gain attenuation rate near the critical frequency. The proposed algorithm also can design PI controller with the given magnitude margin and phase margin specification. The proposed algorithm uses time delay element and saturation function to identify the one point information in frequency domain. We justify the proposed algorithm via the simulation.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.188-196
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• 2003

In order to increase competitiveness and to gain economic benefit, companies ask more and more how to recycle their products in a efficient way. So far, to answer this question, companies are not sufficiently supported by suitable methods specially in the area of disassembly process planning. For this reason, we develop in collaboration with an industrial partner a new method for generating an optimal disassembly sequence. In the presented paper this method will be described in detail by considering the exiting assembly information, disassembly method and disassembly depth. PLM (Profit-Loss Margin) curve that is used to determine disassembly depth consists of profit value, disassembly cost and disassembly effect. Using assessment parameters, generated alternative disassembly sequences are evaluated and optimal disassembly sequence is proposed. This method is applied to generate the optimal disassembly sequence of Door Trim as an example.