• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.19-28
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• 2022

In this study, three types of combined isolator consisting of High Damping Rubber Bearing (HDRB) and wire isolator were developed for Uninterruptible Power Supply system (UPS). The dynamic characteristics of the combined isolator were investigated through one-axis shaking table test. The input acceleration were generated in accordance with ICC-ES AC156 code. Scale factors of the input acceleration were designed to be 0.5-2 times the required response spectrum defined in ICC-ES AC156. Based on the test results, damage and dynamic characteristics of the UPS were investigated: including natural frequency, damping ratio, acceleration time history response, dynamic amplification factor and relative displacement. Based on that, it was found that the combined isolator developed in this study could improve the seismic behavior of the UPS, in particular, the response acceleration.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.11
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• pp.783-789
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• 2022

In a recent study, it was observed that the combustion gas entering the post chamber of a hybrid rocket contains vortices with very small size and high frequency characteristics. In addition, it was observed that small vortices collided with the nozzle wall to create a counter-flow, resulting in additional combustion with ignition delay. This study investigated the physical relationship between ignition delay induced by the counter-flow and the formation of beating pressure. To do this, a newly modified model was proposed by including ignition delay in the existing energy kicked oscillator model proposed by Culick. Numerical results show that the ignition delay is an important factor in determining the occurrence of the combustion pressure beats through the periodic formation of thermoacoustic coupling. In addition, when the ignition delay was reduced by increasing the post chamber length, the phase difference between the energy kick and the pressure generation was increased, the periodic pressure beats did not occur at all.

• Korean Journal of Plant Tissue Culture
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• v.24 no.1
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• pp.37-41
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• 1997

The in vitro regeneration and genetic transformation systems in hot pepper(Capsicum annuum L.) have not been routinely available, which has been a major limiting factor in the application of new genetic manipulations. An efficient procedure to regenerate whole pepper plants and to generate transgenic plants expressing a foreign gene was established. A relatively high frequency of plant regeneration was observed when hypocotyl and cotyledon explants were cultured on MS medium supplemented with NAA 0.1 mg/L plus zeatin 2.0 mg/L or IBA 10.0 mg/L plus BAP 1.0 mg/L. Addition of AgNO$_3$5 $\mu$M to these media improved the regeneration frequency up to 8%. For plant transformation, hypocotyl and cotyledon explants of hot pepper were precultured on shoot induction media without kanamycin added for 2 days, and then cocultured with Agrobacterium tumefaciens pDY183 for 2 days. Putative transformants were obtained from selection media containing 100 mg/L kanamycin sulfate and 500 mg/L carbenicillin. Putatively selected transformants were confirmed by amplification of selectable marker genes (ADA and NPT II) by polymerase chain reacion. Successful transcripts of ADA gene were detected by Northern blot analysis. Enzyme activity of ADA was also examined by spectrophotometric analysis, and expression of ADA gene in hot pepper suggests the potential application of ADA gene as a selectable marker in plants.