• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.289-297
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• 2009

We numerically analyzed flow characteristics of the polymer melt in the screw equipment using a proper modeling and investigated design parameters which have influence on the mixing performance as the capability of the screw equipment. We considered the non-Newtonian and non-isothermal flow in a single rotor equipment to investigate the mixing performance with respect to screw dimensions as shape parameter of the single rotor equipment and screw speed as process parameter. We used Bird-Carreau-Yasuda model as a viscous model of the polymer melt and the particle tracking method to investigate the mixing performance in the screw equipment and considered four mixing performance indexes: residence time distribution, deformation rate, total strain and particle standard deviation as a new mixing performance index. We compared these indexes to determine design parameters and object function. On basis of the analysis results, we carried out the optimal design by using the response surface method and design of experiments. In conclusion, the differences of results between the optimal value and numerical analysis are about 5.0%.

• 한국안전학회지
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• 제12권2호
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• pp.133-139
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• 1997

Conventional concrete mixing method is to put all of the materials simultaneously into a mixer and mix for a required time. However, recently concrete researchers have reported that mixing sequence iufluences the properties of concrete. This study discusses the influence of mixing sequence and partitioning addition of mixing water. Concrete, by method of partitioning addition of mixing water, was found to have substantially stronger strength than conventional concrete with the same water-cement ratio. This means that a higher strength concrete could be obtained by using “Sand Enveloped with Cement”(S.E.C) mixing technique. Both a high bond strength between cement paste and aggregate, and elimination of bleeding both contribute to improving the strength of S. E. C concrete.

• Korean Chemical Engineering Research
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• 제60권2호
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• pp.300-307
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• 2022

매우 짧은 펄스 폭의 X선 자유전자 레이저(XFEL)를 이용한 시간 분해능 연속 펨토초 결정학(time-resolved serial femtosecond crystallography, TR-SFX)기법에서 반응 물질과 생체분자 결정 샘플간의 혼합률(mixing rate)과 결정 샘플과 X선 레이저 간의 충돌률(hit rate)은 생체분자의 시분해 구조 변화에 대한 정확한 이미지 획득 및 효율적인 샘플소비와 같은 TR-SFX의 분석 성능을 결정짓는 핵심인자이다. 본 연구에서는 극초단 내 일어나는 생체분자의 시분해 구조 변화 해석을 위해 초고속 믹싱 기능을 가짐과 동시에 공압 기반의 주문형 액적 젯팅이 가능한 두 가지 다른 방식의 샘플 전달시스템을 고안하였다. 한 방식은 이중 노즐을 통해 토출된 액적의 고속 충돌에 유발된 관성 믹싱을 기반으로 하고 있으며, 다른 방식은 마이크로믹서가 내장된 공압 젯팅을 기반으로 하고 있다. 먼저, 이중 노즐을 통해 토출된 액적의 충돌에 대한 동적 거동 및 액적 내부 관성 유동에 대한 믹싱에 대한 실험 및 수치해석적 연구를 수행하였다. 다음으로 마이크로믹서가 내장된 공압 젯팅 시스템의 성능을 유사한 방법을 통해 평가하였다. 본 연구에서 개발한 샘플 전달시스템은 질환을 유발하는 특정 단백질들의 기작을 규명하거나, 항체 의약품과 신약 후보 물질 탐색하는 데 있어 필수적인 3차원 생체 분자 구조분석 연구에 매우 유용하게 활용될 수 있을 것이다.

• 한국전산유체공학회지
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• 제8권2호
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• pp.16-23
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• 2003

A numerical study of the mixing of two fluids(pure water and a solution of glycerol in water) in a microchannel was carried out. By varying the glycerol content of the glycerol/water solution, the variation in mixing behavior with changes in the difference of the properties of the two fluids(e.g., viscosity, density, diffusivity) was investigated. The mixing phenomena were tested for three micromixers: a square mixer, a three-dimensional serpentine mixer, and a staggered herringbone mixer. The governing equations of continuity, momentum and solute mass fraction were solved numerically. To evaluate mixing performance, a criterion index of mixing of mixing uniformity was proposed. In the systems considered, the Reynolds numbers based on averaged properties were 1 and 10. For low Reynolds number (Re = 1), the mixing performance varied inversely with mass fraction of glycerol due to the dominance of molecular diffusion. The mixing performance by diffusion deteriorated due to a significant reduction in the residence time of the fluid inside the mixers.

• 한국환경과학회지
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• 제20권5호
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• pp.639-645
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• 2011

This study found that flotation efficiencies for removing algae and micro particles in raw water were optimized on mixing intensity and time of the mixing and flocculation conditions with a continuous DAF system. It is more efficient for mixing intensity at 23.1 $s^{-1}$ and time at 660 s(Gt value : 15246) to float flocculated floc with the raw water in M water treatment plant. Flotation efficiency was more than about 0.9 when operated pressure and A/S ratio were sustained at 5 $kg_f{\cdot}cm^{-2}$ and up to 0.056 $mL{\cdot}mg^{-1}$. The continuous DAF system made by the study could be continuously operated for 20 days and sustained not exceeding 4 NTU with raw water with low turbidity(13.4~9.8 NTU).

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.245-248
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• 2005

SCRamjet is the key technology for hypersonic flight over mach number 6. It is characterized by very short residence time in combustor because its internal flow is supersonic. In this short time, the whole process of combustion must be done. Especially numerical study of combustor is important because air-fuel mixing rate influences the performance of combustor. Various methods of air-fuel mixing enhancement are proposed. Among these, cavity injection method is selected to study in this paper. The numerical study is conducted with the variation of the cavity length at the fixed height of unit and jet injection on the downstream of cavity.

• 한국안전학회지
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• 제13권2호
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• pp.109-115
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• 1998

Tri-cresyl phosphate(TCP) was synthesized by reaction of phosphorus chloride with mixed cresol(mixture of m-cresol, p-cresol, and others) in the presence of $AlCl_3$. Some of unwanted products and unreactants colored TCP. In order to separate TCP from these, vaccume distillation was carried twice, but colorless TCP could not be producted. Separation of unwanted materials by 2% NaOH solution was introduced before first and second distillation and optimal separation conditions such as NaOH concentration, mixing volume ratio, mixing time, and rpm were investigated for new batch separation and production of colorless TCP Optimal conditions were 2% NaOH solution, 35% mixing volume ratio of 2% NaOH solution, 1.5 hours of mixing time, and 20 rpm.

• 펄프종이기술
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• 제33권3호
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• pp.44-51
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• 2001

Sedimentation characteristics such as SS, $BOD_5$, COD removal efficiency of waste water in the toilet paper mill using milk carton were examined. Optimum dosage of coagulant, rapid mixing time and slow mixing time were determined by turbidity, SS, COD, $BOD_5$ and then equation for treatment efficiency was suggested. Mechanical strength of floc was determined by turbidity. For the coagulant, polyacrylamide (PAM) is more efficient for removing pollution than the aluminium sulfate. Effective mixing ratios of PAM and aluminum sulfate to remove pollution are 70:30 and 30:70. The lowest turbidity was showed when rapid mixing at 300 rpm after coagulant injection was applied. That which indicates the highest point of flocs mechanical strength.

• 한국공작기계학회논문집
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• 제16권6호
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• pp.146-152
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• 2007

An active micro-mixer, which was composed of an oscillating micro-stirrer in the microchannel to provide rapid, effective mixing at high flow, rates was analyzed. The effects of molecular diffusion and disturbance by the stirrer were considered with regard to two types of mixer models: the simple straight microchannel and microchannel with an oscillating stirrer. Two types of mixer models were studied by analyzing mixing behaviors such as their interaction after the stirrer. The mixing was calculated by Lattice Boltzmann methods using the D2Q9 model. In this study, the time-averaged mixing index formula was used to estimate the mixing performance of time-dependent flow. The mixing indices of the two models compared. From the results, it was found that the mixer with an oscillating stirrer was much more enhanced and stabilized. Therefore, an optimum design for a dynamic micro-mixer with an oscillating stirrer was performed using Taguchi method in order to obtain a robust solution. The design parameters were established as the frequency, the length and the angle of the stirrer and the optimal values were determined to be 2, 0.8D and ${\pm}75^{\circ}$, respectively. It was found that the mixing index of the optimal design increased 80.72% compared with that of the original design.

• Journal of the Korean Statistical Society
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• 제22권2호
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• pp.259-269
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• 1993

A moving average model, LMA(q) and an autoregressive-moving average model, NLARMA(p, q), with Laplacian marginal distribution are constructed and their properties are discussed; Their autocorrelation structures are completely analogus to those of Gaussian process and they are partially time reversible in the third order moments. Finally, we study the mixing property of NLARMA process.