• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1327-1335
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• 2002

The shock wave process represents an abrupt change in fluid properties, in which finite variations in pressure, temperature, and density occur over the shock thickness which is comparable to the mean free path of the gas molecules involved. This shock wave fluid phenomenon is simulated by using the finite difference lattice Boltzmann method (FDLBM). In this paper, a new model is proposed using the lattice BGK compressible fluid model in FDLBM for the purpose of speeding up the calculation as well as stabilizing the numerical scheme. The numerical results of the proposed model show good agreement with the theoretical predictions.

• The Korean Journal of Ceramics
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• 제4권1호
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• pp.20-24
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• 1998

Thin films of diamond-like carbon(DLC) can be successfully deposited by using a magnetron plasma chemical vapor deposition (CVD) method with an rf(13.56 MHz) plasma of $C_dH_8$. Plasma characteristics are analyzed as a function of the magnetic field. As the magnetic field increases, both electron temperature ($T_e$) and density ($n_e$)increase, but the negative dc self-bias voltage (-$V_{ab}$) decreases, irrespective of gas pressures in the range of 1~7 mTorr. High deposition rates have been obtained even at low gas pressures, which may be attributed to the increased mean free path of electrons in the magentron plasma. Effects of rf power and additive gas on the structural properties of DLC films aer also examined by using various technique namely, TED(transmissio electron diffraction) microanalysis, FTIR, and Raman spectroscopies.

• 동력기계공학회지
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• 제11권3호
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• pp.16-21
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• 2007

Three dimensional numerical study was carried out to investigate the effect of aspect ratio on microchannel flow. We considered five straight rectangular channels with aspect ratios (height/width) 0.2, 0.4, 0.6, 0.8 and 1.0. Nitrogen gas flow was investigated for both slip and noslip wall boundary conditions. Isothermal wall condition was assumed. We used control volume method for this simulation. The slip velocity increases with the increase of aspect ratio. Friction coefficient decreases with the increase of aspect ratio. Slip friction coefficient is lower than noslip friction coefficient. Mass flow rate of slip model is higher than that of noslip model. We compared our results with the experimental result reported in the literature. The agreement was good.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.235.2-235.2
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• 2014

Plasma hardly grows in low pressure because of lack of collision. Especially, in extremely low pressure like 1 mTorr, the experiment scale is far larger than mean free path therefore plasma is hardly generated in such low pressure. But low pressure plasma has useful properties like low damage or fine sputtering process because it has typically low electron density. In here, thermal electron is used to make breakdown in low pressure easily and cylindrical geometry is used to help discharge easily. And we changed magnetic field strength to control electron density or temperature. In low pressure, density and temperature behavior is very interesting so its characteristics are examined here.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.204-208
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• 2006

In this study, we investigated the ion energy distributions in a chlorine based inductively coupled plasma by quadrupole mass spectrometer with an electrostatic ion energy analyzer. Ion energy distributions are presented for various plasma parameters such as $BCl_3/Ar$ gas mixing ratio, RF power, and process pressure. As the $BCl_3/Ar$ gas mixing ratio and process pressure decreases, and RF power increases, the saddle-shaped structures is enhanced. The reason is that there are ionized energy difference between $BCl_3$ and Ar, change of plasma potential, alteration of mean free path. and variety of ion collision in the sheath.

• 한국진공학회지
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• 제8권1호
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• pp.55-62
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• 1999

입사 이온과 시료 핵과의 개별 산란 방식으로 이온 산란의 몬테칼로 프로그램을 제작하였다. 이 때 시료 원자의 산란 전단면적과 시료 원자들간의 거리는 시료 원자 밀도의 함수로 주어지는 실질적인 크기로 하여 개개의 시료 입자와의 충돌을 계산한다. 이 프로그램을 이용하여 입사 이온에 대한 시료 물질의 스퍼터링의 현상을 입사 이온과 시료와 관련된 변수들의 관계에 대하여 조사하였다. 입사 이온의 질량, 입사 이온의 에너지, 입사각에 따른 스퍼터링 수율과 시료면의 표면 결합에너지에 대한 수율의 변화, 그리고 스퍼터되는 원자의 에너지 분포를 해석하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권9호
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• pp.634-640
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• 1999

Resonance radiation trapping has a great influence on the characteristics of vacuum ultraviolet(VUV) photon emissions in AC PDP cell. We calculate the spatial andspectral distributions of VUV photons, which are radiated by excited Xe in AC PDP cell by Monte Carlo method. Especially a dip in the spectrum at center frequency is discovered both in simulation and in experiment. We give a physical explanation of this phenomenon by the concept of frequency-dependent mean free path of VUV photons.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1376-1381
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• 2004

Understanding the thermal conductivity and heat transfer processes in superlattice structures is critical for the development of thermoelectric materials and optoelectronic devices based on quantum structures. $Chen^{(1)}$ developed ballistic diffusive equation(BDE) for alternatives of the Boltzmann equation that can be applied to the complex geometrical situation. In this study, a simulation code based on BDE is developed and applied to the 1-dimensional transient heat conduction across a thin film and transient 2-dimensional heat conduction across the film with heater. The obtained results are compared to the results of the $Chen^{(1)}$ and Yang and $Chen^{(1)}$. Finally, steady 2-dimensional heat conduction in the quantum dot superlattice are solved to obtain the equivalent thermal conductivity of the lattice and also compared with the experimental data from $Borca-Tasciuc^{(2)}$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2214-2219
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• 2008

The thermal contact resistance(TCR) of nanosized contact spots has been investigated through a multiscale analysis which considers the resolution of surface topography. A numerical simulation is performed on the finite element model of rough surfaces. Especially, as the contact size decreases below the phonon mean free path, the size dependent thermal conductivity is considered to calculate the TCR. In our earlier model which follows an elastic material, the TCR increases without limits as the number of nanosized contact spots increases in the process of scale variation. However, the elastoplastic contact induces a finite limit of TCR as the scale varies. The results are explained through the plastic behavior of the two contacting models. Furthermore, the effect of air conduction in nanoscale is also investigated.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.62-63
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• 2002

To reach 100 Gbit/in$^2$ magnetic recording densities in hard disk drives specular enhancement of giant magnetoresistance (GMR) effect in spin valve (SV) films has become one of the indispensable means for application as read elements in recording heads [1]. More recently specular spin valve (SSV) structure containing nano-oxides layers (NOL) were reported [2], where MR enhancement is caused to extended mean free path of majority spin polarized electrons through specular reflection at metal/insulator interfaces [3] in the SV films. (omitted)