• Journal of Power Electronics
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• v.15 no.1
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• pp.268-277
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• 2015

In this paper, a dual-converter three-phase pulse width modulation (PWM) rectifier based on unbalanced one-cycle control (OCC) strategy is proposed. The proposed rectifier is used to eliminate the second harmonic waves of DC voltage and distortion of line currents under unbalanced input grid voltage conditions. The dual-converter PWM rectifier employs two converters, which are called positive-sequence converter and negative-sequence converter. The unbalanced OCC system compensates feedback currents of positive-sequence converter via grid negative-sequence voltages, as well as compensates feedback currents of negative-sequence converter via grid positive-sequence voltages. The AC currents of positive- and negative-sequence converter are controlled to be symmetrical. Thus, the workload of every switching device of converter is balanced. Only one conventional PI controller is adopted to achieve invariant power control. Then, the parameter tuning is simplified, and the extraction for positive- and negative-sequence currents is not needed anymore. The effectiveness and the viability of the control strategy are demonstrated through detailed experimental verification.

• 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.

• The Korean Journal of Physiology
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• v.20 no.2
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• pp.236-248
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• 1986

Alterations of renin-angiotensin system have been suggested as one of the mechanisms increasing arterial blood pressure in experimental and clinical hypertension. But the exact nature of high blood pressure in the early and late phase of renal hypertension is still controversial. To clarify the nature of renin release in both unclipped and clipped kidney of two kidney one clip Goldblatt lypertensive rat, experiments have been done in kidney slices, which were obtained from the rats of 3 and 7 days of operation. Basal rate of renin release was suppressed in unclipped kidney slices compared to clipped kidney Norepinephrine increased renin release from unclipped kidney slices, but not from clipped kidney slices. Suppressions by angiotensin Il and arginine vasopressin of renin release were attenuated in the clipped kidney slices compared to unclipped and sham-operated kidney slices. Increases by verapamil and trifluoperazine of renin release were attenuated in the clipped kidney slices compared to unclipped and sham-operated kidney slices. These results suggest that the negative feedback control mechanism of the renin-angiotensin system by angiotensin Il and arginine vasopressin is attenuated in the clipped kidney of two kidney one clip Goldblatt hypertensive rat, and that one of the altered mechanisms may be caused by certain regulatory changes of intracellular calcium and/or calcium-calmodulin complex in the juxtaglomerular cells.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.253-256
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• 2002

A programmable CMOS negative resistor has been designed and fabricated in a 0.5um double poly double metal technology. The proposed CMOS negative resistor consists of a positive feedback OTA and a bump circuit with Gaussian-like I-V curve. Measurements of the fabricated chip confirm that the proposed CMOS resistor shows various negative resistance according to control voltage.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.345-348
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• 2000

In this paper, A Feedforward Linear Power Amplifier for IMT-2000 which IMD characteristics was improved was designed and fabricated. To improve the main power amplifier IMD characteristics, the Feedback loop was added to basic Feedforward Power Amplifier structure. Therefore, the output power of error amplifier can be reduced, and it is easy to control the linearization circuit to cancel total IMD. The designed power amplifier represented the 40㏈m(l0W) output power and -55㏈C 3rd IMD at Center frequency 2.14㎓ (@5㎒).

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1496-1501
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• 2004

Recently, many Korean firms have been adopting 360$^{circ}$ Degree Feedback System with the environmental change in business world. The reason is that the traditional top-down way of personnel evaluation pattern can not but has many limits in this turbulent changing environment. The main purpose of this article is to depict some aspects of 360$^{circ}$ Degree Feedback System including its current status quo, its positive and negative side, and the effective way of its improvement focusing on A firm.

• Journal of The Korean Association For Science Education
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• v.16 no.1
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• pp.97-102
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• 1996

Attitude is considered one of the most important influences on behavior and is defined as an enduring positive or negative feeling about some person, object or issues. The teaching strategies for affective domain are needed to develop the positive attiudes about environments. One of them is to faciliate the involvement of emotional feedback. The purpose of this study was to verify the effects of emotional feedback. Cognitional feedback was carried to control group but cognitional and emotional feedback were carried concurrently to experimental group. By the results, post test scores of experimental group were significantly higher than those of control group about four goals of Environmental Education, respectively. Therefore this strategy is effective to achieve goals of affective domain. Also, emotional feedback is important factor to raise the achievement of cognitive domain, too.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2753-2756
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• 2003

A convenient, tunable loop-gain negative impedance circuit that increases input impedance of a front-end in a bioimpedance measurement has been proposed. Since the proposed circuit comprises wide-band operational amplifiers, selecting operational amplifiers is easy, while an operational amplifier of proper bandwidth should be chosen to use conventional circuit. Also, since loop-gain can be controlled by a feedback resistor connected serially with a feedback capacitor, loop-gain is tunable with a potentiometer. The input impedance of the proposed circuit is two times larger than that of the conventional circuit. Furthermore, closed loop phase response of the proposed circuit is better than that of the conventional circuit or without a negative capacitance circuit. The implemeted, proposed circuit showed stable operation and a zero input capacitance.

• Korean Journal of Child Studies
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• v.26 no.6
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• pp.173-187
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• 2005

This study examined relations between infants' strategies for emotional regulation and maternal responsiveness. Fifty 24-month-olds were observed for six kinds of emotional regulation strategy during four negative emotion-eliciting tasks; their mothers were observed for five styles of maternal responsiveness during toy-centered free play. Infants used different strategies according to the kinds of negative emotioneliciting tasks; their strategies correlated with maternal responsive styles. In the anger-eliciting tasks, infants used "distraction" and "self soothing." In the fear-eliciting tasks, they used "avoidance" and "problem solving." Infants who received more negative feedback from their mothers used the "irritation" strategy. Infants who got received more positive feedback from their mother used the "getting reference" strategy.

• 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.