• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.343-346
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• 2000

When a feedback bridging fault is activated, oscillation may be generated in output signal lines. If the oscillation is generated, the fault may not be detected by logic testing. Thus, in the past we proposed a current sensor to detect feedback bridging faults by supply current testing. The sensor circuit design requires the maximum frequency of oscillation which is generated when feedback bridging fault is excited as a specification. In this paper, an estimation method of the oscillation frequency is proposed. Also, it is shown by some experiments that the frequency obtained by the method can be used for the sensor design.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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• pp.102-111
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• 1996

For the air-fuel ratio control in a fuel injection SI engine, the Jump-Ramp control algorithm has been widely adopted by using the on/off type oxygen sensor. But the Jump-Ramp control method has limitation on treating the frequency and amplitude of the air-fuel ratio oscillation. This study suggests another feedback control logic named modulated fuel feedback control, which has a concept of pre-tuned air-fuel ratio oscillation. In the modulation method, the oxygen sensor output is not treated as on/off signal but as analog signal for feedback. By using the modulation method, the frequency and the amplitude of air-fuel ratio oscillation can be adjustable to some extent for improving the conversion efficiency of the Three-Way Catalyst. The result shows that the performance of the modulation method is better than that Jump-Ramp control method in reducing the amplitude of the air-fuel ratio oscillation as well as in increasing the frequency of the air-fuel ratio oscillation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.3
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• pp.253-262
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• 2003

In this paper, the interference cancellation system, which is used to cancel the feedback signal in the wireless communication system with the same frequency, is studied. The time varying feedback signal generated from transmitter antenna to receiver antenna reduces the performance of the receiver system. the interference cancellation system using adaptive feedback method(AF-ICS) is suggested to prevent the oscillation of the receiver system and maintain the maximum output power of the power amplifier by the reduction of time-varying feedback signal and also this paper conforms that the oscillation disappears from the output signal by cancellation of the feedback signal and the total output power is satisfied the system specification.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.38-43
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• 2008

This paper presents a new interference cancellation method to remove the oscillation due to feedback signal of RF relay. In this paper, we estimate the feedback signal using to LMS(Least Mean Square) algorithm and remove the interference through attenuation signal arbitrary corresponding to feedback signal. From the various performance analysis for various doppler effects, a proposed method prevents from oscillation using -30dB attenuation signal as a cancellation value of feedback signal.

• Journal of IKEEE
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• v.6 no.2 s.11
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• pp.128-135
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• 2002

We use the saturation nonlinear feedback element to generate self-oscillation in order to find an ultimate gain and period of linear plant. The use of saturation nonlinear feedback element can improve accuracy of an ultimate gain and period of unknown linear plant. An ultimate gain and period of linear plant can be used to tune a PID controller parameters. It is possible that an asymmetric oscillation can be occurred under the special circumstances such as with static load disturbance. We analyze an asymmetric self-oscillation. As the results of an analysis, we propose a method to find an ultimate gain and period of linear Plant under the asymmetric self-oscillation.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.12
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• pp.542-548
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• 2002

We consider an unknown linear time invariant plan with static load disturbance. A saturation function nonlinear element is sued to find th one point information in the frequency domain. We analyze an asymmetric self-oscillation caused by static load disturbance with relay feedback and saturation function feedback. We propose a new method to tune a PID controller using a saturation nonlinear feedback element in the presence of asymmetric oscillation. The proposed method does not require the knowledge of plant d.c. gain with an asymmetric oscillation in the plat output.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05a
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• pp.90-95
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• 1997

In this work, linear dynamics of a circulating fluid-fueled subcritical reactor system with temperature feedback and external neutron source was modeled and examined. In a circulating fluid-fuel system, the stable region is slightly moved by a circulation fluid effect. The effects of subcriticality and temperature feedback coefficient on the reactor stability were tested by calculating frequency response of neutron density originated from reactivity perturbation or external source oscillation of system. The amplitude transfer function has a different shape near subcritical region due to the exponential term in the transfer function. The results of the study show that at a slightly subcritical region, low frequency oscillation in accelerator current or reactivity can be amplified depending on the temperature feedback. However, as the subcriticality increases, the oscillation becomes negligible regardless of the magnitude of the temperature feedback coefficient.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1234-1240
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• 2002

A new feedback control law is proposed and tested for suppressing the vortex shedding from a circular cylinder in a uniform flow. The lift coefficient ( $C_{L}$) is employed as a feedback control signal and the control forcing is given by a rotational oscillation of the cylinder. The influence of the feedback transfer function on the $C_{L}$ reduction is examined. The main rationale of the feedback control is that a feedback control forcing is imposed at a phase which is located outside the range of lock-on. By applying the feedback control law, $C_{L}$ is reduced significantly. Furthermore, the reduction mechanism of $C_{L}$ is analyzed by showing the vortex formation modes with respect to the forcing phase.e.ase.e.

• Journal of the Korean Institute of Telematics and Electronics
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• v.8 no.3
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• pp.15-26
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• 1971

The paper presents a new method for analyzing oscillation regions of transistor oscillators. In transistor feedback oscillators oscillation region appears as a circle in feedback impedance complex plane. When the resistive component of feedback impedance is fixed and the reactive component of feedback impedance is varied or vice versa, the locus of maximum negative output conductance becomes hyperbola. In transistor crystal oscillators oscillation region is determined by two circles which make real part and imaginary part of input impedance zero in load impedance complex plane. When the resistive compoment of load impedance is fixed and the reactive colnponent of load impedance is varied or vice versa, the loci of maximum or minimum resistive component of input impedance become straight lines.

• Molecules and Cells
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• v.27 no.5
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• pp.497-502
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• 2009

In mouse embryos, somite formation occurs every two hours, and this periodic event is regulated by a biological clock called the segmentation clock, which involves cyclic expression of the basic helix-loop-helix gene Hes7. Hes7 expression oscillates by negative feedback and is cooperatively regulated by Fgf and Notch signaling. Both loss of expression and sustained expression of Hes7 result in severe somite fusion, suggesting that Hes7 oscillation is required for proper somite segmentation. Expression of a related gene, Hes1, also oscillates by negative feedback with a period of about two hours in many cell types such as neural progenitor cells. Hes1 is required for maintenance of neural progenitor cells, but persistent Hes1 expression inhibits proliferation and differentiation of these cells, suggesting that Hes1 oscillation is required for their proper activities. Hes1 oscillation regulates cyclic expression of the proneural gene Neurogenin2 (Ngn2) and the Notch ligand Delta1, which in turn lead to maintenance of neural progenitor cells by mutual activation of Notch signaling. Taken together, these results suggest that oscillatory expression with short periods (ultradian oscillation) plays an important role in many biological events.