• Korean Chemical Engineering Research
• /
• 제56권3호
• /
• pp.430-434
• /
• 2018

본 연구에서는 잔류 메틸렌 클로라이드 제거를 위한 마이크로웨이브를 이용한 파클리탁셀 건조에서 유효확산계수 및 물질전달계수를 조사하였다. 모든 온도(35, 45, $55^{\circ}C$)에서 건조 초기에 많은 양의 잔류 메틸렌 클로라이드가 제거되었으며 건조 온도가 증가할수록 건조 효율은 증가하였다. 건조 온도가 증가할수록 파클리탁셀의 유효확산계수($1.299{\times}10^{-13}{\sim}2.571{\times}10^{-13}m^2/s$)와 물질전달계수($1.625{\times}10^{-11}{\sim}4.857{\times}10^{-11}m/s$)는 증가하였다. 또한 낮은 Biot 수(0.0100~0.0151)로부터 건조의 진행이 주로 파클리탁셀의 외부확산에 의해 조절됨을 알 수 있었다.

• 한국물환경학회지
• /
• 제30권2호
• /
• pp.166-174
• /
• 2014

Velocity gradient, G, a measure of the average velocity gradient in the fluid has been applied for complete mixing of chemicals in mechanical mixing devices. G values were calculated by the power input transferred to fluid in turbulent and transient range. Chemical reactions occur so fast that total mass transfer time required for even distribution of the chemicals determine the overall reaction time. The total mass transfer time is composed of the time for complete mixing through the reactor and for diffusion of the chemicals into the eddy. Complete mixing time was calculated by CFD (computer fluid dynamics) and evaluated by tracer tests in 2 liter jars at different rotating speeds. Turbulent range, Reynolds number above 10,000 in regular 2 liter jars occurred at revolution speed above 100 rpm (revolution per minute), while laminar range occurred at revolution speed below 10 rpm. A typical range of rotating speed used in jar tests for water and wastewater treatment was between 10 and 300 rpm, which covered both transient and turbulent range. G values supplied from a commercial jar test apparatus showed big difference from those calculated with power number specially in turbulent range. Diffusion time through eddy decreased 1.5 power-law of rotating speed. Complete mixing time determined by pumping number decreased increases in rotating speed. Total mass transfer time, finally, decreases as rotating speed increases, and it becomes 1 sec at rotating speed of 1,000 rpm. Complete mixing times evaluated from tracer tests showed higher than those calculated by power number at higher rotating speed. Complete mixing times, however, calculated by CFD showed similar to those of experimentally evaluated ones.

• 한국분무공학회지
• /
• 제1권1호
• /
• pp.63-75
• /
• 1996

The purpose of this study is to investigate the break-up characteristics by taking advantage of a two-phase coaxial nozzle. Air and water are utilized as working fluids and the mass ratio air/water has been controlled to characterize the atomization, diffusion and development of mixing process. By way of a photographic technique, conventional developing structures and diffusion angles have been analyzed systematically with variations of mass ratios. The turbulent flow components of the atomized particles were measured by a two channel LDV system and the data were treated by an on-lined measurement equipment. According to the photographic results the spreading angles decreased because the axial inertia moment was relatively higher than the lateral one with respect to the increase of mass ratio. It is found the jet flow diffuses linearly in a certain limit region while the atomizing characteristics, in terms of the distributions of particle diameters did not show particular differences. It may be expected that these fundamental results can be used as reference data in studying the atomization, breakup and diffusions.

• 디지털융복합연구
• /
• 제6권2호
• /
• pp.55-64
• /
• 2008

The Internet possesses not only features of mass media but also features of word of mouth communication. Communication channel is considered as one of most important variables in diffusion process. In this paper, we examined functionality of technology diffusion on the Internet through the use of meta tags. We have measured the coefficients of the Bass diffusion model which has been well-established in new product diffusion. This research shows that the Bass model is appropriate for describing technology diffusion on the Internet. The external influence as represented by the coefficient of innovation was found to be much smaller while the internal influence dominates in all meta tag diffusion. In meta tag diffusion, the internal influence as represented by the coefficient of imitation was increased at least twice bigger than that of consumer durables and information technology. Collecting necessary data in social sciences research can be a burden. This research shows that it can be alleviated through the use of software agents over the Internet. The research made use of software agents for collecting longitudinal data from publicly accessible archive such as Archive.org.

• 한국지하수토양환경학회지:지하수토양환경
• /
• 제13권6호
• /
• pp.40-49
• /
• 2008

평평한 fractures에서 공극을 가진 모암으로의 NAPL 확산을 수치적인 방법으로 해석하였다. 2D와 3D에 대한 일회성 디스크 소스와 3D 연속 디스크소스에 대한 모델은 Caralaw and Jaeger(1959)의 이론을 바탕으로 개발하였다. 3D 연속 디스크소스에 대해 공극모암으로 확산되는 NAPL의 총량을 계산할 수 없기 때문에 확산이 반구형으로 이루어진다고 가정하여 등농도선의 합을 이용하여 공극모암으로 확산되는 NAPL의 총량을 계산하였다. 수치적 계산에 따르면 2D 대비 3D의 경우에 NAPL 손실 시간이 현저히 빠른 것으로 나타났으며, 디스크 소스의 중심점에서 normalized된 농도는 일회성 디스크 소스는 시간에 따라 감소하고, 연속 디스크 소스는 증가하는 것으로 나타났으며, 시간과 공간에 따라 확산율은 감소하는 것으로 나타났다. 그리고 NAPL의 mass 손실은 1에 도달하지 못하였으며, 이는 연속 디스크 소스를 semi-infinite로 가정하고 적분했기 때문이다. 확산에 의해 사라지는 시간은 소스의 크기 및 모암 공극률 크기 증가에 비례해서 지수함수적으로 증가하고, 반면 NAPL의 용해성이 증가하면 감소하는 것으로 나타났다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1310-1315
• /
• 2004

The present study deals with the unique characteristics of hydrogen jet diffusion flames, such as split flames and reignition phenomenon. The split flames are composed of a small flamelet on the nozzle rim and a lifted main flame at downstream. When mass flow rates of fuel reach a critical point, a small-sized flamelet is found to remain in the vicinity of the nozzle exit and the flame reignition subsequent to blowout of main flame occurs repeatedly. In this study, the non-luminous hydrogen jet diffusion flames are visualized by using schlieren technique in order to analyze the combustion characteristics of hydrogen jet diffusion flames with focus on the flame reignition phenomenon.

• 한국초전도ㆍ저온공학회논문지
• /
• 제9권3호
• /
• pp.72-82
• /
• 2007

This paper relates to reducing the temperature of a cryogenic liquid by contacting it with gas bubbles, which can be characterized by diffusion-driven evaporative cooling, The characteristic of diffusion-driven evaporative cooling is thoroughly examined by theoretical. analytical and experimental methods specifically for the case of helium injection into liquid oxygen. The results reveal that if the gaseous oxygen partial pressure in helium bubbles is lower than the liquid oxygen vapor pressure, cooling occurs autonomously due to diffusion mass transfer. The method of lowering the injected helium temperature turns out to be very effective for cooling purpose.

• Bulletin of the Korean Chemical Society
• /
• 제17권3호
• /
• pp.217-219
• /
• 1996

• Nuclear Engineering and Technology
• /
• 제5권2호
• /
• pp.115-131
• /
• 1973

L.S. Pontryagin의 Maximum Principle과 수직방향을 고려하지 않은 2군 화산 방정식을 우라늄농축도 범위에 제한없이 원통형원자로의 최소 임계질량문제에 적용하였다. 핵연료 장전방법에 관한한 최적 원자로는 내심부와 외심부가 최소의 농축도를 갖고 중간영역은 최대의 농축도를 갖는 3-영역식 원자로인 것으로 밝혀졌다. 상기 3-영역식 원자로를 모델로 하여 임계조건을 유도하였으며, 또한 고리원자로를 예로하여 농축도를 여러가지로 변환시키면서 임계조건의 해를 구하는 수치해석을 수행하였다. 그 결과 여러가지 임계조건중 최소의 임계질량을 갖는 경우는 중간영역에서의 최대 농축도가 1.2%이고 내심부와 외심부에서의 농축도가 0.65%일때라는 것이 판명되었다.

• 대한토목학회논문집
• /
• 제13권2호
• /
• pp.279-285
• /
• 1993

여러 오염물질 사이의 흡착 경쟁, 평형, 물질확산의 상호 연관성을 이해하는 것은 효율적인 활성탄 흡착탑 설계 및 운전을 위하여 중요하다. 흡착탑내에서의 오염물질의 확산 및 흡착 현상을 동역학적 및 수학적으로 예측하기 위하여 "Micro-Diameter-Depth Adsorption System" Technique을 개발하여 평형 및 물질확산 계수들을 측정하였다. 활성탄 입자의 외부 "Film Transfer"와 입자 내부에서의 "Surface Diffusion"을 고려한 오염 물질 사이의 흡착경쟁, 탈착, Chromatographic Displacement Effect 등을 Homogeneous Surface Diffusion Model(HSDM)을 이용하여 예측했다. p-Chlorophenol(PCP)/p-Nitrophenol(PNP)의 Breakthrough Curve에서 PCP는 PNP에 의해 Displace되는 현상을 볼 수 있었으며 HSDM은 이를 잘 예측하였다. Dodecylbenzenesulfonate (DBS)는 흡착된 DBS의 일부분이 비가역적 흡착반응을 보인다는 가정하에서 HSDM에 의해 잘 예측될 수 있었다.