• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.768-773
• /
• 2004

When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is underexpanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with nonequilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics can not even know. In the present study, the effect of the nonequilibrium condensation on the underexpanded moist air jet impinging on a vertical flat plate is investigated experimentally. Flow visualization and impact pressure measurement are performed for various relative humidities and flat plate positions. The obtained results show the plate shock and Mach disk are dependent on the nozzle pressure ratio and the relative humidity, but for a given nozzle pressure ratio, the diameters of the plate shock and Mach disk depend on the stagnation relative humidity. The impact pressure deviation from the flow of without condensation is large, as the relative stagnation humidity increases.

• Journal of Mechanical Science and Technology
• /
• v.20 no.8
• /
• pp.1292-1301
• /
• 2006

This article investigates numerically the carrier-phonon interactions in thin gallium arsenide (GaAs) film structures irradiated by subpicosecond laser pulses to figure out the role of several recombination processes on the energy transport during laser pulses and to examine the effects of laser fluences and pulses on non-equilibrium energy transfer characteristics in thin film structures. The self-consistent hydrodynamic equations derived from the Boltzmann transport equations are established for carriers and two different types of phonons, i.e., acoustic phonons and longitudinal optical (LO) phonons. From the results, it is found that the two-peak structure of carrier temperatures depends mainly on the pulse durations, laser fluences, and nonradiative recombination processes, two different phonons are in nonequilibrium state within such lagging times, and this lagging effect can be neglected for longer pulses. Finally, at the initial stage of laser irradiation, SRH recombination rates increases sufficiently because the abrupt increase in carrier number density no longer permits Auger recombination to be activated. For thin GaAs film structures, it is thus seen that Auger recombination is negligible even at high temperature during laser irradiation.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2007.05a
• /
• pp.237.1-237.1
• /
• 2007

• International Journal of Aeronautical and Space Sciences
• /
• v.14 no.2
• /
• pp.105-111
• /
• 2013

Radiative heating phenomena occurring in planetary entry flights are reviewed for the purpose of educating those who are not familiar with the problem. How the radiative heat transfer rates to the Apollo entry vehicle were measured and analyzed are first described. Next, the effects of thermo-chemical non-equilibrium on radiation are summarized. Then the radiation problems in entry flights into other planets are reviewed. Finally, unsolved problems are enumerated.

• 한국초전도학회:학술대회논문집
• /
• v.12
• /
• pp.17-17
• /
• 2002

• Proceeding of EDISON Challenge
• /
• 2017.03a
• /
• pp.75-81
• /
• 2017

Polymer collapse transition에 대한 연구가 많이 진행되어왔다. 허나 각각의 microstate에 대한 entropy나 free energy에 대한 계산을 하지는 못하였다. 최근 local nonequilibrium thermodynamics와 관련한 논문이 발표되었는데 이는 비평형 상태에서의 각각의 microstate에 대한 확률 분포를 결정하는 물리량을 발견 및 특성을 규명하여 이 중 특별한 상태가 지니는 "information" 이라는 양이 내부에너지와 엔트로피와의 상관관계가 있음을 보였다. 또한, 이러한 information theory를 이용한 Shannon entropy를 사용하여 entropy를 정의하고 free energy와 같은 물리량을 계산하였다. 따라서 이를 이용하여 information theory를 이용한 Shannon entropy와 이로 정의된 free energy를 이용하여 polymer collapse중 entropy 및 free energy를 계산하였다.

• Journal of the Korean Applied Science and Technology
• /
• v.18 no.3
• /
• pp.161-166
• /
• 2001

While the equilibrium behaviour of surfactant solution is well studied, the understanding of the kinetics and pathways of structural transition under nonequilibrium conditions is only begining to develop. Attention has recently been directed mainly towards micellar kinectics, transitions between micellar and lamellar phases, vesicle fusion, and phases separation in microemulsions. This progress has profited greatly from developments that have taken place in various techniques and instruments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.628-630
• /
• 2000

Since the concept for the ozone generation using a nonequilibrium electric discharge techniques had been proposed by Siemens, some experimental and theoretical studies on the ozone generation by streamer corona discharge, surface discharge and silent discharge have been performed. In this paper some results on the discharge characteristics of the silent discharge gap with various dielectric materials were reported. Dielectric materials used in this study were pyrex glass, quartz and glass beefs with diameter of 1 mm.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.8
• /
• pp.652-661
• /
• 2018

It is necessary to resolve the absolute velocity as well as Mach number to reflect the high temperature effect in high speed flow. So this region is classified as high enthalpy flows distinguished from high speed flows. Many facilities, such as arc-jet, shock tunnel, etc. has been used to obtain the high enthalpy flows at the ground level. However, it is difficult to define the exact test condition in this type of facilities, because some chemical reactions and energy transfer take place during the experiments. In the present study, a quasi 1D code considering the thermochemical non-equilibrium effect is developed to effectively estimate the test condition of a shock tunnel. Results show that the code gives reasonable solution compared with the results from the known experiments and 2D axisymmetric simulations.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.425.1-425.1
• /
• 2014

Thermal transport in nanomaterials is not only scientifically interesting but also technological important for various future electronic, bio, and energy device applications. Among the various computation approaches to investigate lattice thermal transport phenomena in nanoscale, the atomistic nonequilibrium Green's function approach based on first-principles density functional theory calculations appeared as a promising method given the continued miniaturization of devices and the difficulty of developing classical force constants for novel nanoscale interfaces. Among the nanometerials, carbon atomic chains, namely the cumulene (all-doulble bonds, ${\cdots}C=C=C=C{\cdots}$) and polyyne (alternation of single and triple bonds, ${\cdots}C{\equiv}C-C{\equiv}C{\cdots}$) can be considered as the extream cases of interconnction materials for nanodevices. After the discovery and realization of carbon atomic chains, their electronic transport properties have been widely studied. For the thermal transport properties, however, there have been few literatures for this simple linear chain system. In this work, we first report on the development of a non-equilibrium Green's function theory-based computational tool for atomistic thermal transport calculations of nanojunctions. Using the developed tool, we investigated phonon dispersion and transmission properties of polyethylene (${\cdots}CH2-CH2-CH2-CH2{\cdots}$) and polyene (${\cdots}CH-CH-CH-CH{\cdots}$) structures as well as the cumulene and polyyne. The resulting phonon dispersion from polyethylene and polyene showed agreement with previous results. Compared to the cumulene, the gap was found near the ${\Gamma}$ point of the phonon dispersion of polyyne as the prediction of Peierls distortion, and this feature was reflected in the phonon transmission of polyyne. We also investigated the range of interatomic force interactions with increase in the size of the simulation system to check the convergence criteria. Compared to polyethylene and polyene, polyyne and cumulene showed spatially long-ranged force interactions. This is reflected on the differences in phonon transport caused by the delicate differences in electronic structure.