• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2010.10a
• /
• pp.318-319
• /
• 2010

• Proceedings of the SAREK Conference
• /
• 2005.06a
• /
• pp.214-214
• /
• 2005

• Proceedings of the SAREK Conference
• /
• 2004.06a
• /
• pp.197-197
• /
• 2004

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.10a
• /
• pp.651-652
• /
• 2013

• Proceedings of the Korean Magnestics Society Conference
• /
• 2008.12a
• /
• pp.27.1-27.1
• /
• 2008

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.6
• /
• pp.982-990
• /
• 1987

In previous modeling of Helmholtz-type pulse combustion water heater, muffler and the motion of the flapper valve were omitted. In present work, these have been included in modeling for providing more accurate information regarding the thermal and dynamic behavior of the water heater. In addition, a computer simulation based on the modeling was developed. The comparison of computer predictions with available experimental data shows that the simulation is satisfactory in predicting the nature of operating behavior, amplitudes of the pressure oscillations, and the magnitude of the frequency. But the predicted time-averaged axial temperature of the flue gas along the flue tube length is somewhat below the previous experimental results. The temperature pulsation of the combustion chamber and the velocity pulsation of the flue gas were predicted which have never been measured in previous studies. In particular, the latter is of importance for a valid determination of the heat transfer enhancement due to the gas flow pulsation. Heat transfer results in flue tube were presented and discussed. Also the effects on the installation of the muffler were investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.40 no.3
• /
• pp.237-242
• /
• 2012

Spaceborne pulse tube-type cryogenic compressors are widely used for space applications. To guarantee cooling performance of the compressor, mission life time and micor-vibration stability, suitable thermal control of compressor is required. Micro-vibration of the compressor is the one of the sources to degrade the pointing performance of observation satellite. In the present work, on-orbit thermal design of compressor in order not to degrade the performance of micro-vibration isolation system keeping the thermal control performance has been proposed and investigated through thermo-mechanical analysis.

• Progress in Superconductivity and Cryogenics
• /
• v.24 no.2
• /
• pp.1-6
• /
• 2022

This paper reviews the literature that has been published since 1980s related to cryogenic refrigeration systems for quantum computing. The reason why such a temperature level of 10-20 mK is necessary for quantum computing is that the superconducting qubit is sensitive to even very small thermal disturbances. The entanglement of the qubits may not be sustained due to thermal fluctuations and mechanical vibrations beyond their thresholds. This phenomenon is referred to as decoherence, and it causes an computation error in operation. For the stable operation of the quantum computer, a low-vibration cryogenic refrigeration system is imperative as an enabling technology. Conventional dilution refrigerators (DR), so called 'wet' DR, are precooled by liquid helium, but a more convenient and economical precooling method can be achieved by using a mechanical refrigerator instead of liquid cryogen. These 'dry' DRs typically equip pulse-tube refrigerators (PTR) for precooling the DRs around 4 K because of its particular advantage of low vibration characteristic. In this review paper, we have focused on the development status of 4 K PTRs and further potential development issues will be also discussed. A quiet 4 K refrigerator not only serves as an indispensable precooler of DR but also immediately enhances the characteristics of low noise amplifiers (LNA) or other cryo-electronics of various type quantum computers.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.240.2-240.2
• /
• 2014

Characteristics of pulse-discharged plasma in liquid and its biological applications to proteins are investigated by making use of high voltage Marx generator. The Marx generator has been consisted of 5 stages, where each charging capacitor is $0.5{\mu}F$ to generate a high voltage pulse with rising time of $1{\mu}s$. We have applied an input voltage of 6 kV to the each capacitor of $0.5{\mu}F$. The high voltage pulsed plasma has been generated inside a polycarbonate tube by a single-shot operation, where the breakdown voltage is measured to be 7 kV, current of 1.2 kA, and pulse width of ${\sim}1{\mu}s$ between the two electrodes of anode-cathode made of stainless steel, which are immersed into the liquids. For the investigation of the influence of pulsed plasma on biomolcules, we have focused on the amino acids, DNA, proteins, cell and cholesterol.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.419-426
• /
• 2008

As pulse detonation engine(PDE) does not need compression mechanisms such as compressors because self-sustained detonation waves are able to compress propellant gases by their incident shock waves, the PDE can have a simple straight-tube structure. In this study, we propose an autonomous driving valve system of the PDE, which fill premixed gases into the PDE tubes at high frequency with high mass flow rate. The proposed valve is composed of only three parts: a piston, a cylinder, and a spring. This valve system can produce intermittent flow at high mass flow rate, and also can keep stable reciprocal motion by using the propellant-gas enthalpy. When the cylinder content product is assumed to be constant, experimental results of the mass flow rate were approximately equal to the calculation model. We confirmed the autonomous driving valve performance by experiments, and concluded that this extremely simple valve with no electrical power and controller can be used as the PDE propellant supply system.