• Korean Journal of Optics and Photonics
• /
• v.8 no.2
• /
• pp.111-115
• /
• 1997

Vertical-cavity surface-emitting laser(VCSEL)s operating at 1.3-micron wavelength for optical communication are fabricated by using Si/SiO$_2$dielectric quater-wave pairs on both sides of the InGaAsP(${\lambda}_g$=1.3 ${\mu}{\textrm}{m}$) gain material. VCSELs are optically pumped with a Nd-YAG laser in a pulsed mode and lasing around 1.3 microns is observed. Lasing characteristics such as threshold pump intensity as a function of mirror-reflectivity, polarization, and threshold pump density with pump spot size are investigated.

• Journal of the KSME
• /
• v.31 no.7
• /
• pp.644-651
• /
• 1991

• Journal of the Society of Naval Architects of Korea
• /
• v.55 no.4
• /
• pp.321-329
• /
• 2018

Resonance phenomena occurs at large vertical pump which is operating to cool down the hot steam using sea water in the power plant. To avoid the resonance, the natural frequency needs to be isolated about 20% from motor operating speed. Yet, excessive vibration occurs especially at low tide. At first, natural frequency of the whole pump system and each part is calculated using ANSYS. As it is revealed in the previous journal papers that only circular pipe part is related to resonance, the FSI technique is applied for free vibration analysis. The natural frequency is reduced to 60% (compared to that) of the frequency measured in air as it is similar to other published results. And the frequency obtained by finite element analysis is almost same to that obtained from modal test. Based on the accurate finite element model and analysis, design change is tried to avoid the resonance by changing the thickness of pipe and base supporting plate. In stead of doing optimization process, design sensitivity is computed and used to find such designs to avoid resonance.

• Plant Journal
• /
• v.9 no.1
• /
• pp.43-49
• /
• 2013

In this study, the natural frequency of the actual operating vertical pump in the P combined cycle power plant is measured and the cause of high vibration is determined by using fluid-structure coupled vibration theory. Choosing the vibration reduction plan suited for field conditions and using the numerical analysis verify effectiveness of the plan. The plan is applied to the actual pump and the empirical experiments are conducted.

• Journal of KSNVE
• /
• v.4 no.4
• /
• pp.425-433
• /
• 1994

A detailed investigation of a reed resonance for a vertical pump design has been conducted. The structural features of this class of pump lead to typical dynamic characteristics. Of particular importance is the fact that the pump assembly is suspended on a high column above the floor with a heavy motor on the top. Considerable amount of mass forces is involved and the vibration can cause damage to the pumps or to the foundation. It is shown that the reed resonance of the pump-motor system plays important role for design and troubleshooting purposes.

• The KSFM Journal of Fluid Machinery
• /
• v.2 no.2 s.3
• /
• pp.13-18
• /
• 1999

The pump safety related to the functions in nuclear power plants must be designed to meet load conditions considering seismic requirements. In order to satisfy both structural integrity and operability of these pumps, the initial step in the seismic qualification is to establish the resonant frequencies of the structure. Applications we made to the design of the vertical and horizontal type pump. Computational results are analyzed with respect to the dynamic characteristics and are compared to the expected design requirements.