• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.6-11
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• 2015

PPS 소자가 삽입된 N형 실리콘 제어 정류기(NSCR_PPS)소자에서 게이트와 $N^+$ 확산층 간격(Gate to Primary $N^+$ diffusion Space; GPNS)의 변화가 정전기 보호 성능에 미치는 영향을 연구하였다. FPW 구조와 CPS 이온주입을 행하지 않은 구조를 갖는 종래의 NSCR 표준소자는 on 저항, 스냅백 홀딩 전압 및 열적 브레이크다운 전압이 너무 낮아 정전기 보호소자의 필요조건을 만족시키지 못해 마이크로칩의 정전기보호소자로 적용이 어려웠다. 그러나 본 연구에서 제안하는 PPW 구조와 CPS 이온주입을 동시에 적용하여 변형설계된 소자에서는 GPNS의 변화가 정전기 보호성능의 향상에 영향을 주는 중요한 파라미터였으며, 정전기보호소자의 설계창을 만족시키는 향상된 정전기보호성능을 나타내어 고전압 동작용 마이크로 칩의 정전기보호 소자로 적용 가능함을 확인하였다.

• 한국진공학회지
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• 제9권2호
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• pp.150-154
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• 2000

Impurity-free vacancy diffusion 방법을 이용하여 압축 응력을 가진 InGaAs/InGaAsP 다중 양자 우물 구조에서 열처리 온도에 따른 무질서 정도를 조사하였다. InGaAs/SiO$_2$ cap 구조가 InP/$SiO_2$ cap 구조보다 급속열처리 (rapid thermal annealing : RTA) 과정에서 더 많은 청색 천이를 나타내었다. 열처리 온도 $700^{\circ}C$에서, InGaAs/$SiO_2$ cap 구조의 경우 다중양자우물의 밴드갭 파장은 1.55 $\mu\textrm{m}$대역에서 1.3 $\mu\textrm{m}$ 대역으로 이동하였으며, InGaAs/$SiO_2$ cap 구조와 InP/$SiO_2$ cap 구조의 밴드갭 파장차이는 195 nm (123 meV)로 높은 선택성을 나타내었다. 또한, DCXRD 스펙트럼으로부터 다중양자우물 구조에서 균일한 합금형태로 완전히 무질서화되는 것을 볼 수 있었다.

• 대기
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• 제14권3호
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• pp.29-40
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• 2004

It is well known that convections and fronts are the most effective weather systems for the vertical transport of pollutants. I used a two dimensional front model in order to investigate the mechanism of the vertical transport of atmospheric pollutants between planetary boundary layer(PBL) and free atmosphere by fronts. The main dynamic processes which contribute the vertical transport of pollutants are advection and diffusion. The transported amount of pollutant from the boundary layer to the free atmosphere increases dramatically during the developing stage of the front. 46% of pollutants are transported vertically within 12 hour and 54% are transported within 24 hour. In the meantime, compared to the total amount of pollutants transported by both advection and diffusion, about 25% (30%) less pollutants are transported when only advection (diffusion) process in included in the model. The most important mechanism for the vertical transport is vertical advection, while the vertical diffusion process plays an important role in the redistribution of pollutants in the PBL.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제13권1호
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• pp.31-40
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• 2009

In the present work transformation of dimensionless heat diffusion equation for the solution of moving boundary problems have been formulated. The formulation is based on 1-D, 2-D and 3-D, unsteady heat diffusion equations. These equations are rst turned int dimensionless form by using dimensionless quantities and their transformation was formulated in liquid and solid phases. The salient feature of this work is that during the transformation of dimensionless heat diffusion equation there arises a convective term $\tilde{v}$ which is responsible for the motion of interface in liquid as well as solid phase. In the transformed heat equation, a correction factor $\beta$ also arises naturally which gives the correct transformed flux at interface.

• 한국경영과학회지
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• 제34권4호
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• pp.15-26
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• 2009

Bass diffusion model have played a central role in studying the diffusion of the new products since 1969, the year of publication of Bass model. Almost 750 publications based on the Bass diffusion model have explored extensions and applications. Extension models can be divided into two types. One is the model containing marketing-mix variables and the other is the model containing additional parameters. This paper presents another extension model of the latter type. Our model allows the time varying coefficients of innovation and imitation. Two pieces approximation of time varying coefficients is introduced and it's parameters are estimated based on NLS(Non-Linear Mean Square) method. Empirical studies are performed and the results show that our model is superior to the basic Bass model and the NUI(Non-Uniform Influence) model which is the well-known extension of the Bass model. The model developed in this paper is, also, transformed into the Bass model with the ready potential adopters in order to enhance the descriptive power.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.62-65
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• 2003

In this study, to confirm corrosion of reinforced concrete affected by carbonation, chloride ion diffusion, absorption ratio, air permeability, measured carbonation velocity coefficient, chloride ion diffusion coefficient, absorption coefficient, air permeability coefficient. Corrosion velocity under environment of complex deterioration. And than compared corrosion velocity with these coefficients. As the results of this study, the correlation coefficient between chloride ion diffusion coefficients and absorption coefficient was revealed that it is very high. As well, an increase in carbonation, chloride ion diffusion also increases corrosion velocity. It showed that corrosion velocity was affected by the carbonation, chloride ion diffusion, absorption ratio, air permeability. Generally, data on the development of these coefficient made with none, organic B, organic A, inorganic B, and inorganic A is shown. It showed that coating of surface prevent steel bar from deteriorating.

• 한국결정성장학회지
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• 제14권2호
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• pp.58-62
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• 2004

The shape evolution of the interface void of copper metallization for intergrated circuits under electromigration stress is modeled. A 2-dimensional finite-difference numerical method is employed for computing time evolution of the void shape driven by surface diffusion, and the electrostatic problem is solved by boundary element method. When the diffusion coefficient is isotropic, the numerical results agree well with the known case of wedge-shape void evolution. The numerical results for the anisotropic diffusion coefficient show that the initially circular void evolves to become a fatal slitlike shape when the electron wind force is large, while the shape becomes non-fatal and circular as the electron wind force decreases. The results indicate that the open circuit failure caused by slit-like void shape is far less probable to be observed for copper metallization under a normal electromigration stress condition.

• 한국통신학회논문지
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• 제29권1C호
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• pp.50-58
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• 2004

본 논문은 수정된 이방성 확산 펄터를 이용한 영상 개선 방법을 제안하였다. 이를 위하여 최소 신뢰 스케일을 기반으로 하는 센서 잡음 추정과 스케일 스페이스 방법을 도입하였다. 이때 이방성 필터는 구해진 임계값 함수와 국부 기울기에 의해 수정되었다. 모의 실험을 통해 제안한 방법이 평탄 영역에서의 잡음을 거의 증폭시키지 않으면서도 뛰어난 에지 향상을 보임을 증명할 수 있었다.

• 한국분말재료학회지
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• 제7권3호
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• pp.137-142
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• 2000

In order to analyze the densification behaviour of stainless steel powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model, as well. The power-law creep model in conjunction with various diffusion models was applied to the HIP process of 316L stainless steel powder compacts under 50 and 100 MPa at $1125^{\circ}C$. The results of the calculations were verified using literature data. It could be found that the contribution of the diffusional mechanisms is not significant under the current process conditions.

• Bulletin of the Korean Chemical Society
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• 제17권2호
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• pp.192-198
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• 1996

We present a theoretical formulation of diffusion process on solid surface based on multidimensional transition state theory (TST). Surface diffusion of single adatom results from hopping processes on corrugated potential surface and is affected by surface vibrations of surface atoms. The rate of rare events such as hopping between lattice sites can be calculated by transition state theory. In order to include the interactions of the adatom with surface vibrations, it is assumed that the coordinates of adatom are coupled to the bath of harmonic oscillators whose frequencies are those of surface phonon modes. When nearest neighbor surface atoms are considered, we can construct Hamiltonians which contain terms for interactions of adatom with surface vibrations for the well minimum and the saddle point configurations, respectively. The escape rate constants, thus the surface diffusion parameters, are obtained by normal mode analysis of the force constant matrix based on the Hamiltonian. The analysis is applied to the diffusion coefficients of W, Ir, Pt and Ta atoms on the bcc(110) plane of W in the zero-coverage limit. The results of the calculations are encouraging considering the limitations of the model considered in the study.