• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.54-62
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• 1994

This paper presents active control methodologies to suppress structural deflections of a composite beam using a distributed piezoelectric-film actuator and sensor. Three types of different controllers are employed to achieve vibration suppression. The controllers are established depending upon the information on the velocity components of the structrue and on the deflection magnitudes as well. They are constant-amplitude controller(CAC), constant-gain mcontroller(CGC), and constant-amplitude-gain controller(CAGC). For the minimization of the residual vibration (chattering in a settled phase), which is the practical shortcoming of the conventional CAC dur to time delay phenomenon of the hardware system, a new control algoritym CAGCis designed by selecting switching constants in an optimal manner with respect to the initial tip deflection and the applied voltage. The experimental investigations of the transient and forced vibration control for the first vibrational mode are undertaken in order to compare the suppression efficiency of each control algorithm. Moreover, simultaneous controllability of various vibrational modes through the proposed scheme is also experimentally verified by pressenting both the transfer function and the phase.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3412-3418
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• 2013

The Purpose of this study was to evaluate by comparing the dose change and build up characteristic according to delay time in 30 days of glass dosimeter processed preheat and non preheat when measuring accumulation dose of radiation by using glass dosimeter over the long haul. For obtaining low dose with 0.1 mGy, 1 mGy and 5 mGy, we employed diagnostic generator AccuRay-650R. We compared the build up characteristic over the long haul by exposuring radiation to 30 glass dosimeters sorted into 10 glass dosimeters per tube voltage and current. In Non preheat glass dosimeter, initial measured dose was inferior to exposed dose but as time goes on, was close to exposed dose steadily. In 72 hour after experiment end, non preheat glass dosimeters were not indicated the difference from preheat glass dosimeters and statistical analysis were meaningful (p>0.05). Initial measured dose for low glass dosimeter processed preheat was close to exposed dose and stable. After 15 days dose was gradually increased. Previous study characteristics of glass dosimeter were with respect to characteristic of glass dosimeter in high dose of high energy area. However, in this study, we make a judgment to measure the dose of glass dosimeter without preheat processing when measuring the accumulation dose of low dose in conclusion.

• Clinical and Experimental Pediatrics
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• v.46 no.8
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• pp.784-788
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• 2003

Purpose : Perinatal asphyxia occurring in newborn is one of the major causes of acute mortality and chronic neurological disability in survivors. We have studied the relationship between early electroencephalography(EEG) findings and clinical course and neurologic outcome in severe asphyxiated neonates. Methods : Between the period of July 1999 and June 2002, 25 neonates who were diagnosed with severe perinatal asphyxia(1-minute Apgar score of ${\leq}3$ and initial pH is less than 7.2) at NICU in Dongsan Medical Center were enrolled. An EEG was recorded and analyzed within three days of life and divided into two groups - group 1(normal or focal change on EEG) and group 2(generalized abnormal EEG). Between the two groups, clinical courses and neurologic outcomes were compared. Results : Fifteen infants(60%) were group 1 and ten infants(40%) were group 2(polyspikes, burst-suppression, generalized low voltage). Associated maternal disease, days of hospitalization, need for ventilator support, delay of oral feeding and convulsion duration are significantly higher and longer in group 2. Also, poor neurologic outcome(expire, developmental delay) was significantly higher in group 2(60%) than group 1(13.3%). Conclusion : Thus, the early neonatal EEG in asphyxiated newborn can be a predictable diagnostic tool in assessment of neurologic outcome.