• 한국수자원학회논문집
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• 제30권6호
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• pp.731-741
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• 1997

동일한 원수에 대하여 탁도제거 지배인자를 변화시켜가며 임펠러 형태별 탁도제거효율을 비교함으로써 관습적으로 설계 운영해오던 혼화과정의 문제점과 정수장의 최적 혼화저건을 만족시킬 수 있는 혼화기의 임펠러 타입 및 체류시간에 대한 운전기준을 제시하고자 하였다. 실험결과 혼화기의 종류는 탁도제거 효율을 물론 정수장의 경제적 운영을 위한 전력비 절감에도 효과가 있는 것으로 판명되었다. 또한 혼화지와 혼화기 설계기준에 일반적으로 활용되어 오던 속도구매 G이외에도 원수의 단위체적당 필요한 혼화에너지를 제시하여 정수효율은 물론 정수장의 경제적 운영효과를 극대화시킬 수 있는 참고자료로 제시하였다.

• 대한기계학회논문집A
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• 제33권4호
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• pp.417-424
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• 2009

A micro-mixer with a quasi-active rotor was fabricated, and mixing characteristics were evaluated. The proposed micro-mixer combines an active type micro-mixer with a passive type micro-mixer. The micro-rotor, which is a moving part of an active type micro-mixer, is added in a micro-chamber of a passive type vortex micro-mixer. The rotor rotated by inflows tangent to a chamber, causing strong perturbations. The micro-mixers were fabricated using photosensitive glass. Mixing efficiency of the micro-mixers was measured using an image analysis method. Mixing efficiency and characteristics of the micro-rotor mixer were compared with the vortex micro-mixer without a rotor. Mixing efficiency was reduced as Reynolds number increased at a low Reynolds number due to decrease of residence time. Mixing efficiency at higher Reynolds number, on the other hand, was improved even though residence time decreased since the contact surface between fluids increased by twisted flow. The perturbation induced by rotating rotor at greater than Re 200 improved the efficiency of the rotor mixer.

• Computers and Concrete
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• 제31권6호
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• pp.501-511
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• 2023

The strengthening efficiency of biopolymer treated soil depends on biopolymer type, concentration ratio, soil type, initial water content, curing time and mixing method. In this study, the physical and mechanical properties of xanthan gum (XG) treated kaolinite were investigated through compaction test, Atterberg limit test, triaxial test and unconfined compression test. The results indicated that the optimum water content (OWC) increased from 30.3% of untreated clay to 33.5% of 5% XG treated clay, while the maximum dry density has a slight increase from 13.96 kg/m³ to 14 kg/m³ of 0.2% XG treated clay and decrease to 2.7 kg/m³ of 5% XG treated clay. Meanwhile, the plastic limit of XG treated clay increased with the increase of XG concentration, while 0.5% XG treated clay can be observed the maximum liquid limit with 79.5%. Moreover, there are the ideal water content about 1.3-1.5 times of the optimum water content achieving the maximum dry density and curing time to obtain the maximum compressive strength for different XG contents, which the UCS is 1.52 and 2.07 times of the maximum UCS of untreated soil for 0.5% and 1% XG treated clay, respectively. In addition, hot-dry mixing can achieve highest UCS than other mixing methods (e.g., dry mixing, wet mixing and hot-wet mixing).

• 한국생산제조학회지
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• 제22권3호
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• pp.459-464
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• 2013

The purpose of a micro-mixing device is to enhance the mixing by increasing the diffusion effect between different types of flows. There have been many attempts to actively or passively increase mixing. However, those studies were limited to lab-scale experiments because the production of devices requires a series of processes, time, cost, and the mixing quality itself. For this reason, this study attempted to develop a quick and simple process for micro-mixing device fabrication by using conventional machining and bonding processes and applying ultrasonic waves from the outside of the mixing device. The mixing quality was quantified by using the mixing index, and the results showed that the proposed system increases the mixing from ~33% to ~10% with respect to the flow rates.

• Computers and Concrete
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• 제6권4호
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• pp.343-356
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• 2009

Experiments were designed to investigate the flow behavior of portland cement paste and concrete incorporating superplasticizers. The paste and concrete mixtures were subjected to prolonged mixing for up to 110 min at high temperature. The yield stress values of concrete and that of the corresponding cement paste were measured using a rotating rheometer and viscometer, respectively. The results reveal a weak linear correlation between the yield stress of concrete mixtures and that of the corresponding cement pastes. Results also indicate that the yield stress of concrete varies in a linear fashion with the elapsed time, while its variations with the temperature and superplasticizer dosage follow power and inverse power functions, respectively. In this study, the genetic algorithms (GA) technique was used to predict the yield stress of concrete considering various parameters, such as the mixing time, ambient temperature, and superplasticizer dosage. A sensitivity study was conducted to evaluate the ability of the GA equations thus developed to capture the effects of test parameters on the yield stress of concrete. It was found that the GA equations were sensitive to the effects of test parameters and provided yield stress predictions that compared well with corresponding experimental data.

• Journal of the Korean Data and Information Science Society
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• 제11권2호
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• pp.173-179
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• 2000

Interval prediction based on the empirical distribution function for the class of time series with time varying coefficients is discussed. To this end, strong mixing property of the model is shown and results due to Fotopoulos et. al.(1994) are employed. A simulation study is presented to assess the accuracy of the proposed interval predictor.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.925-928
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• 2000

In this paper, physical properties of cement mortar for floor using expansion agent are discussed varied with mixing time and curing temperature, delivery time and content of added water for preventing fluidity loss. According to experimental results, slump loss shows high with elapse of time And as curing temperature goes up, it also show high when curing temperature goes up and time lag between mixing and casting increases. As curing temperature goes down, drying shrinkage shows to be decreased. But it shows decline tendency with increase of added water content.

• Journal of the korean society of oceanography
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• 제32권1호
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• pp.17-27
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• 1997

Miami Isopycnic Coordinate Ocean Model is applied to the East Sea to estimate the renewal time of the upper Intermediate Water The model gives about 10 years of renewal time. Extrapolating this result to the whole water mass below, including the upper Intermediate Water, leads to about 81.4 years of renewal time, which is quite comparable to that obtained by Kim and Kim (1997) based on the recent observations. Deep winter mixing occurs in the north of the basin. The areas of the largest water mass conversion, from the upper mixed to the intermediate below, are along the periphery of the deep mixing zone. Large portion of the renewed Intermediate Water then advects along the Korean and Japanese coasts. It is concluded that the high-oxygen content Intermediate Water found off the Korean coast (Kim and Chung, 1984) is in part locally formed but mostly advected from the deep mixing zone.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.137-138
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• 2023

This study proposed the optimal mixing time for pre-mixed cement and post mixed cement using the statistical analysis method of box plots. Pre-mixed cement can prevent material seegregation, strength loss, and quality variation if mixed for at least 60 seconds, and the data median is shown to be within the box range. Post-mixed cement should be mixed for at least 180 seconds to prevent material segregation, strength loss, and quality variation, and compressive strength tends to increase with longer vibrating times. Therefore, it is suggested that using pre-mixed cement can shorten the vibrating time and increase the productivity of the concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.7-12
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• 1992

The aim of this study is to develop economical High-Strength and High-Quality Concrete, and to assure quality control of Concrete in the field. For this purpose, Five types of Mixing Methods are examined and the relationship between slump loss and slump recovery by transport is studied. As a result, workability and strength are dependent on the Mixing Method, although the Mixing proportions are same, Also, adding admixture in the field is proposed as an alternative to consider the relationship between slump loss and slump recovery.