• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1469-1478
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• 2014

Use of acetonitrile in electrolytes promotes better operation of supercapacitors. Recent efforts show that electrolytes containing acetonitrile can also function in a wide range of operating temperatures. Therefore, this paper addresses the dielectric relaxation processes, structure and dynamic properties of the bulk acetonitrile at various temperatures. Systems of acetonitrile were modeled using canonical ensemble and simulated by employing Molecular Dynamics method. Results show that interactions among the molecules were correlated within a cut-off radius while parallel and anti-parallel arrangements are observed beyond this radius at relatively high and low temperatures respectively. Furthermore, effects of C-C-N and C-H bending modes were greatly appreciated on the power spectral density of time rate change of dipole-dipole correlations whereas frequency shifts were observed on all modes at the lowest temperature under consideration. Linear variations with temperature were depicted for reorientation times and self-diffusion coefficients. Shear viscosity was also computed with a good accuracy within a certain range of the temperature as well.

• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.119-122
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• 2011

A new high speed AFM probe has been proposed and fabricated. The probe is integrated with PZT actuated cantilever realized in bulk silicon wafer using heavily boron doped silicon as an etch stop layer. The cantilever thickness can be accurately controlled by the boron diffusion process. Thick SCS cantilever and integrated PZT actuator make it possible to be operated at high speed for fast imaging. The resonant frequency of the fabricated probe is 92.9 kHz and the maximum deflection is 5.3 ${\mu}m$ at 3 V. The fabricated probe successfully measured the surface of standard sample in an AFM system at the scan speed of 600${\mu}m$/sec.

• Solar Energy
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• v.17 no.2
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• pp.23-33
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• 1997

This paper reviews the advanced solar cell structures used in space. These are the structures which incorporate the back surface field and reflectors with very shallow and lightly doped emitters. Their use in space has shown that the thinner cells are more resistive to radiation damage than the thicker ones. It has been found that the charged particles affect both the surface and bulk of the cells used in space. This causes degradation in the output power, which in effect, can be explained by the degrading diffusion length of the cells. The PERL cells showed higher BOL(beginning of life) efficiency and almost the same EOL(end of life) efficiency as structures with wrap-around contact configuration fabricated on 10 ${\Omega}cm$ resistivity substrates. This observation lead to a conclusion that, the space cells do not necessarily need to have very high BOL efficiency except in specific missions which require such.

• Journal of the Korean Society of Safety
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• v.6 no.3
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• pp.40-49
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• 1991

To better understand the phenomena inside an absorber, where heat and mass transfer coexist, this study selected the most baslc absorption model from in whifh water vapor is absorbed on the surface of a stationary lithium bromide absurbent solution. The purpose of this study is to obtain basic knowledge of heat and mass transfer processes as affected by Marangoni convection induced by addition of surfactant. We apply a non-flowing bulk absorption model and assume that dropwise surfactant is fixed on the absorbent surface. Four governing equation-continuity, laminar monentum, energy and diffusion are solved numerically to obtain temperature and concentraion distributions during steam absorption with Marangonl convection.. In conclusion, Sh and Nu genrally increase at the initial absorption stage.

• Journal of Powder Materials
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• v.18 no.2
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• pp.172-175
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• 2011

We developed a 3D simulation model of microstructure evolution of vertically aligned porous structure due to phase separation during film growth. The model proves its validity by reproducing the results of previous researches which are topological features of the microstructures and effects of varied processing parameters. The model will be extended by including bulk diffusion effect and elastic effect.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; O$_2$, N$_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.84-91
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• 2008

Generalized hydrodynamic (GH) theory for multi-species gas and the computational models are developed for the numerical simulation of hypersonic rarefied gas flow on the basis of Eu's GH theory. The rotational non-equilibrium effect of diatomic molecules is taken into account by introducing excess normal stress associated with the bulk viscosity. The numerical model for the diatomic GH theory is developed and tested. Moreover, with the experience of developing the dia-tomic GH computational model, the GH theory is extended to a multi-species gas including 5 species; $O_2,\;N_2$, NO, O, N. The multi-species GH model includes diffusion relation due to the molecular collision and thermal phenomena. Two kinds of GH models are developed for an axisymmetric flow solver. By compar-ing the computed results of diatomic and multi-species GH theories with those of the Navier-Stokes equations and the DSMC results, the accuracy and physical consistency of the GH computational models are examined.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.248-248
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• 2010

We have demonstrated new functionalities of Ag-doped chalcogenide glasses based on their capabilities as solid electrolytes. The influence of silver on the properties of the newly formed materials is regarded in terms of diffusion kinetics, and Ag saturation is related to the composition of the hosting material. Silver saturated in chalcogenide glass has been used in the formation of solid electrolyte, which is the active medium in the programmable metallization cell (PMC) device. In this paper, we investigated the optical properties of Ag-doped chalcogenide thin film by He-Ne laser beam exposure, which is concerned with the Ag-doping effect of PMCs before or after annealing. Chalcogenide bulk glass was fabricated by a conventional melt quenching technique. Amorphous chalcogenide and Ag thin films were prepared by e-beam evaporation at a deposition rate of about $4\;{\AA}/sec$. As a result of resistance change with laser beam exposure, the resistance abruptly dropped from the initial value of $1.4\;M{\Omega}$ to the saturated value of $400\;{\Omega}$.

• Applied Science and Convergence Technology
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• v.26 no.5
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• pp.95-109
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• 2017

There are several contributions to the gas load of a system of which often the most important is outgassing. Adsorption occurs via two main processes, physisorption and chemisorption, and can be described using five (or six) classifying isotherms. Outgassing is the result of desorption of previously adsorbed molecules, bulk diffusion, permeation and vapourisation. Looking at the desorption rate, pumping speed and readsorption on surfaces, the net outgassing of the system can be calculated. There is significant variation in measured outgassing rates between different materials but also between published rates for the same materials, in part due to the number of different methods used to measure outgassing. This article aims to review the outgassing process, outgassing rates, measurement methods and techniques that can be used to reduce the outgassing of a system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.53-57
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• 2002

Reduction of insulation thickness would be beneficial not only for increasing the cable length but would also improve its thermal performance. An interfacial diffusion method was devised to reduce insulation thickness by improving the interfacial properties of XLPE cable insulation. In this paper, to evaluate superficially the interface properties between XLPE insulation and semiconducting layer, the dielectric and insulation properties of tan${\delta}$ and volume resistance were measured with temperature dependence. Above the results, dielectirc and insulation properties with semiconductor/XLPE were more anormal than its bulk caused by the interfacial properties.