• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.205-215
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• 2004

The characteristic ratio assignment (CRA) method〔1〕 is new polynomial approach which allows to directly address the transient responses such as overshoot and speed of response time in time domain specifications. The method is based on the relationships between time response and characteristic ratios($\alpha_i$ ) and generalized time constant (T), which are defined in terms of coefficients of characteristic polynomial. However, even though the CRA can apply to developing a linear controller that meets good transient responses, there are still some fundamental questions to be explored. For the purpose of this, we have analyzed several sensitivities of a linear system with respect to the changes of coefficients itself and $\alpha_i$ of denominator polynomial. They are (i) the unnormalized root sensitivity : to determine how the poles change as $\alpha_i$ changes, and (ii) the function sensitivity to determine the sensitivity of step response to the change of o, and to analyze the sensitivity of frequency response as o, changes. As an other important result, it is shown that, under any fixed T and coefficient of the lowest order of s in denominator, the step response is dominantly affected merely by $\alpha_1, alpha_2 and alpha_3$ regardless of the order of denominator higher than 4. This means that the rest of the$\alpha_i$ s have little effect on the step response. These results provide some useful insight and background theory when we select $\alpha_i$ and T to compose a reference model, and in particular when we design a low order controllers such as PID controller.

• Journal of Power Electronics
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• v.9 no.3
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• pp.507-515
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• 2009

This paper proposes an autonomous decentralized control for a parallel connected uninterruptible power supply (UPS) system based on a fast power detection method using a FPGA based hardware controller for a single phase system. Each UPS unit detects only its output voltage and current without communications signal exchange and a quasi dq transformation method is applied to detect the phase and amplitude of the output voltage and the output current for the single phase system. Fast power detection can be achieved based on a quasi dq transformation, which results in a realization of very fast transient response under rapid load change. In the proposed method, the entire control system is implemented in one FPGA chip. Complicated calculations are assigned to hardware calculation logic, and the parallel processing circuit makes it possible to realize minimized calculation time. Also, an Nios II CPU core is implemented in the same FPGA chip, and the software can be applied for non-time critical calculations. Applying this control system, an autonomous decentralized UPS system with very fast transient response is realized. Feasibility and stable operation are confirmed by means of an experimental setup with three UPSs connected in parallel. Also, rapid load change is applied and excellent performance of the system is confirmed in terms of transient response and stability.

• New & Renewable Energy
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• v.3 no.2 s.10
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• pp.24-30
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• 2007

The transient response of PEMFC (proton exchange membrane fuel cell) is important criteria in the application of PEM fuel cell to real automotive system. In this work, using a transparent unit PEM fuel cell, the transient response and cathode flooding during load change are investigated. The cell voltage is acquired according to the current density change($0.3Acm^2$ to $0.6A/cm^2$) under various stoichiometry conditions and different flooding intensities, Also the cathode gas channel images are obtained by CCD imaging system simultaneously. The different level of undershoots appeared at the moment of load changes under different cathode stoichiometries and flooding intensities. It takes about 1s that the product water comes up onto the flow channel so that oxygen supply is temporarily blocked which causes voltage loss in that "undershoot". The correlation of the dynamic behavior with stoichiometry and cathode flooding is induced from the results of these experiments.

• Bulletin of the Korean Chemical Society
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• v.34 no.11
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• pp.3223-3226
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• 2013

Spherical phospholipid-bilayers, vesicles, were prepared using the layer-by-layer double emulsion technique, which allows the bilayer to be formed asymmetrically. On the outer layer of the vesicles, the phospholipase D (PLD) reacted to convert phosphatidylcholine (PC) to phosphatidic acid (PA). The reaction induced the curvature change of the vesicles, which eventually led to rupture. The response time from the time of PLD injection to the time of rupture was measured against different vesicle curvatures and the outer layer phase, using the fluorescence intensity change of a pH-sensitive dye encapsulated within the vesicles. The effect of the vesicle curvature on the response was observed to be more significantly dramatic at the solid phase, compared to the liquid phase. Furthermore, in the solid phase, the response time was faster for 80 and 155 nm vesicles and, slower for 605 nm vesicles than similarly sized vesicles in the liquid phase vesicles. This difference in the response time was thought to result from the configuration determined by the phase difference and the PLD behavior.

• Journal of Korean Academy of Nursing
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• v.13 no.3
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• pp.119-126
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• 1983

Early extra-uterine development of the newborn infant has the potential for clarifying important questions of nature and care taking environment. In this study, tactile and auditory stimulation is used on .a group of infants to determine the effects of their response. Infants were tested by EKG at 24∼48 hrs after birth ana all they are free from complication. Stimuli presented were-touch and sound (40dB, 70dB and 40∼70dB). The result of the study were as follows: 1) The heart rate was seen to depend on their sleep-wake state. (light sleep ; 125/min, eyes: open & motor activity increase ； 151/min crying ; 185/min). 2) The heart rate affected by tactile & auditory stimulus. The heart rate response was acceleration above the prestimulus level. (tactile, 231min increase, auditory ; 16∼21/min increase), and heart rate change was seen to depend on prestimulus rate. (γ=.73) 3) There was a decrease in heart rate when they were soothe. (touch ; 24.8sec, 21/min decrease, pacifier ; 14.5sec, 26/min decrease) and significant difference in time between touch and pacifier (t= 1.76, p<0.05). This result support the evaluation of newborn infant's sensory abilitics, and has even begin to influence changes in nursing care. But systemic monitoring of newborn infants response would. further define.

• The Journal of Korean Physical Therapy
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• v.19 no.4
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• pp.33-41
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• 2007

Purpose: To investigate environmental enrichment and nerve stimulation follows in application times with the change of BDNF & Trk-B receptor in the motor cortex and spinal cord. Methods: Experimental groups were divided into the five groups. Group I: normal control group, Group II: experiment control group, Group III: sciatic never electrical stimulation after MCAO, Group IV: application of only environmental enrichment after MCAO, Group V: never electrical stimulation with environmental enrichment after MCAO. Histologic observation and coronal sections were processed individually in goat polyclonal antibody phosphorylated BDNF and rabbit polyclonal antibody Trk-B receptor. Results: In immunohistochemistric response of BDNF and Trk-B, group II were showed that lower response effect at postischemic 1 days, 3 days, and 7 days. Group V were showed that increase response effect at postischemic 3 days, 7 days and 14 days. Specially showed that the most response effect at postischemic 14 days. In neurobehavioral assessment, group V were significantly difference from other groups on between-subject effects. Conclusion: The above results suggest that combined environmental enrichment with peripheral nerve electrical stimulation in focal ischemic brain injury were more improved that the change of BDNF & Trk-B receptor expression than non treatment.

• Journal of the Korean Ceramic Society
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• v.29 no.6
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• pp.489-495
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• 1992

The continuous compaction response of zirconia powders prepared by different processing treatments was investigated. Though the yield point could be or not below 1 MPa, the change of slope was always observed at high pressure range around 60 MPa. Powder compaction was mainly governed by second compaction stage and compaction rate was decreased with increasing forming pressure. Rotary vacuum dried powder favored a high compaction density, whereas freeze dried and calcined powders favored an increase in the pressing efficiency. In order to extract more reliable information about powder compaction, it was necessary to use not only compaction response diagram but also compaction rate diagram.

• ETRI Journal
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• v.6 no.2
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• pp.3-9
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• 1984

This paper proposes an optimal control scheme for shaft position control using microcomputer-based state-variable feedback. In this scheme a performance index was set up in order to ruduce the overshoot and improve the steady- state response speed, and the time-variant system parameters were identified in real time for optimal control. As a result of experiment, the over-shoot was not occured and the response speed was improved 2. 9 times about proportional control. This scheme improves the performance against the variation of load and sampling time, and adding the integral control in this scheme can reduce the steady-state error without any change in response time.

• Journal of the Korean Statistical Society
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• v.7 no.2
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• pp.109-119
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• 1978

When a response surface by a seconde order polynomial regression model, the stationary point is obtained by solving simultaneous linear equations. But the point is a function of random variables. We can find a confidence region for this point as Box and Hunter provided. However, the confidence region is often too large to be useful for the experiments, and it is necessary to augment additional design points in order to obtain a satisfactory confidence region for the stationary point. In this note, the author suggests a method how to augment design points "eficiently", and shows the change of the confidence region of the estimated stationary point in a response surface.e surface.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.8
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• pp.610-615
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• 2003

This paper proposes a nonlinear virtual coupling fur haptic interface, which offers better performance while maintaining stability of the system. The nonlinear virtual coupling is designed based on a human response model. This human response model exploits delay between the human Intention and the actual change of arm impedance. The proposed approach provides with less conservative constraints for the design of stable haptic interface, compared with the traditional passivity condition. This allows increased performance that is verified through experiments.