• Journal of Biosystems Engineering
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• 제37권6호
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• pp.429-433
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• 2012

Purpose: While rapeseed oil, soy bean oil, palm oil and waste cooking oil are being used for biodiesel, the viscosity of them should be lowered for fuel. The most widely used method of decreasing the viscosity of vegetable oil is to convert the vegetable oil into fatty acid methyl ester but is too expensive. This experiment uses ultrasonic energy, instead of converting the vegetable oil into fatty acid methyl ester, to lower the viscosity of the waste cooking oil. Methods: For irradiation treatment, the sample in a beaker was irradiated with ultrasonic energy and the viscosity and temperature were measured with a viscometer. For heating treatment, the sample in a beaker was heated and the viscosity and temperature were measured with a viscometer. Kinematic viscosity was calculated by dividing absolute viscosity with density. Results: The kinematic viscosity of waste cooking oil and cooking oil are up to ten times as high as that of light oil at room temperature. However, the difference of two types of oil decreased by four times as the temperature increased over $83^{\circ}C$. When the viscosity by the treatment of ultrasonic energy irradiation was compared to one by the heating treatment to the waste cooking oil, the viscosity by the treatment of ultrasonic energy irradiation was lower by maximum of 22% and minimum of 12%, than one by the heating treatment. Conclusions: Ultrasonic energy irradiation lowered the viscosity more than the heating treatment did, and ultrasonic energy irradiation has an enormous effect on fuel reforming.

• 한국건설순환자원학회논문집
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• 제6권2호
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• pp.123-129
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• 2018

본 연구의 목적은 고강도 및 일반강도 영역의 물-결합재 비에 대해 시멘트계열 재료의 점도를 감소시키기는 것에 대한 정보를 제공하는 것이다. 시멘트 계열 재료의 유동성을 결정하는 것은 물-결합재 비 및 치환재료와 감수제가 있다. 이를 레올로지적으로 보았을 때 물-결합재 비가 낮은 경우 항복치와 점도를 낮추며 감수제의 경우 항복치 저감에 영향을 주지만 점도 저하에는 한계가 있다. 따라서 이 연구에서는 시멘트 계열 재료의 점도를 낮추기 위해 물-결합재 비에 따른 폐석회석 치환에 대한 점도 저하 가능성을 분석하였다. 실험 결과, 폐석회석을 치환하였을 경우 점도 저하의 효과가 있었으며 이는 시멘트 계열 재료의 점도 제어에 유의미한 결과를 주는 것으로 판단되었다. 따라서 본 연구의 결과는 시멘트 계열 재료의 점도를 낮추는 방안으로써 분체 치환에 의한 방안의 기초적인 자료가 될 것으로 생각된다.

• 한국지구과학회지
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• 제38권2호
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• pp.105-114
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• 2017

Two dimensional finite element method with quadrilateral basis functions was applied to the spherical high order filter on the spherical surface limited area domain. The basis function consists of four shape functions which are defined on separate four grid boxes sharing the same gridpoint. With the basis functions, the first order derivative was expressed as an algebraic equation associated with nine point stencil. As the theory depicts, the convergence rate of the error for the spherical Laplacian operator was found to be fourth order, while it was the second order for the spherical Laplacian operator. The accuracy of the new high order filter was shown to be almost the same as those of Fourier finite element high order filter. The two-dimension finite element high order filter was incorporated in the weather research and forecasting (WRF) model as a hyper viscosity. The effect of the high order filter was compared with the built-in viscosity scheme of the WRF model. It was revealed that the high order filter performed better than the built in viscosity scheme did in providing a sharper cutoff of small scale disturbances without affecting the large scale field. Simulation of the tropical cyclone track and intensity with the high order filter showed a forecast performance comparable to the built in viscosity scheme. However, the predicted amount and spatial distribution of the rainfall for the simulation with the high order filter was closer to the observed values than the case of built in viscosity scheme.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 춘계 학술대회논문집
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• pp.192-198
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• 1999

The present study proposes modified temperature-dependent non-Newtonian viscosity model and investigates flow characters and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The proposed modified temperature dependent viscosity model has non-zero value near the high temperature and high shear rate region while on the existing viscosity models have zero value. Two versions of thermal boundary conditions involving difference combination of heated walls and adiabatic walls are analyzed in this study. The combined effect of temperature dependent viscosity, buoyancy, and secondary flow caused by second normal stress difference are ail considered. The Reiner-Rivlin model is adopted as a viscoelastic fluid model to simulate the secondary flow caused by second normal stress difference. Calculated Nusselt numbers by the modified temperature-dependent viscosity model gives under prediction than the existing temperature-dependent viscosity model in the regions of thermally developed with same secondary normal stress difference coefficients with experimental results in the regions of thermally developed. The heat transfer enhancement of the viscoelastic fluid in a 2:1 rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

• KSTLE International Journal
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• 제8권1호
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• pp.16-20
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• 2007

This study introduces a new approach to a falling ball viscometer by using a high speed motion camera to measure the viscosity of both Newtonian and non-Newtonian fluids from the velocity-time data. This method involves capturing continuous photographs of the entire falling motion of the ball as the ball accelerates from the rest to the terminal velocity state. The velocity of a falling ball was determined from the distance traversed by the ball by examining video tape frame by frame using the marked graduations on the surface of the cylinder. Each frame was pre-set at 0.01. Glycerin 74% was used for Newtonian solution, while aqueous solutions of Polyacrylamide and Carboxymethyl Cellulose were for non-Newtonian solutions. The experimental viscosity data were in good agreements with the results obtained from a rotating Brookfield viscometer.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.112-116
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• 1996

This experimental study was performed to produce high flowing nomal strength concrete using viscosity agent. Test variables were selected to the viscosity agent contents with 4 levels, the cement contents with 5 levels and the coarse aggregate contents with 3 levels, etc. As a result, the high flowing and filling properties of concrete were obtatined by proper amount of viscosity agent and superplasticizer in the normal strength concrete. For the concrete mix proportions, it was found that unit weight of cement was more than 364kg/㎥ and volume of coarse aggregate was less than $280\ell/\textrm{m}^3$ in this study.

• 콘크리트학회논문집
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• 제14권3호
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• pp.275-282
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• 2002

고유동 콘크리트를 제조할 경우는 유동성 향상을 위한 다량의 고성능 감수제와 재료분리를 방지하기 위한 다량의 분체 혹은 증점제로 말미암아 제조비용이 고가이고, 또한 품질관리에도 많은 어려움이 있다. 그러므로, 본 연구에서는 유동성 및 재료분리 저항성이 우수한 고유동 콘크리트를 경제적으로 제조하기 위하여 분리저감형 유동화제의 최적배합비를 결정한 다음, 유동화 공법으로 접근하는 것을 검토하였다. 실험결과로 유동화제 첨가량이 증가할수록 유동성 및 블리딩량은 증가하였고, 공기량 및 재료분리저항성은 저하하는 것으로 나타났다. 따라서, 여기에 증점제를 첨가함에 따라 양호한 유동성에서 블리딩량이 저하하였고, 재료분리저항성도 증대되었는데, 마지막으로 AE제량 증가에 따라 저하된 공기량이 회복되므로써 양질의 분리저감형 유동화제로 최적배합비를 결정할 수 있었다. 경화 콘크리트 특성으로 유동화 공법으로 제조된 고유동 콘크리트의 압축강도는 베이스 콘크리트보다 증가하는 것으로 나타났고, 무다짐 공시체의 압축강도는 표준다짐 공시체의 압축강도와 유사한 것으로 나타나 다짐 방법간의 차이는 없는 것으로 나타났다.

• 한국분말재료학회지
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• 제26권3호
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• pp.201-207
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• 2019

Tungsten heavy alloys (W-Ni-Fe) play an important role in various industries because of their excellent mechanical properties, such as the excellent hardness of tungsten, low thermal expansion, corrosion resistance of nickel, and ductility of iron. In tungsten heavy alloys, tungsten nanoparticles allow the relatively low-temperature molding of high-melting-point tungsten and can improve densification. In this study, to improve the densification of tungsten heavy alloy, nanoparticles are manufactured by ultrasonic milling of metal oxide. The physical properties of the metal oxide and the solvent viscosity are selected as the main parameters. When the density is low and the Mohs hardness is high, the particle size distribution is relatively high. When the density is high and the Mohs hardness is low, the particle size distribution is relatively low. Additionally, the average particle size tends to decrease with increasing viscosity. Metal oxides prepared by ultrasonic milling in high-viscosity solvent show an average particle size of less than 300 nm based on the dynamic light scattering and scanning electron microscopy analysis. The effects of the physical properties of the metal oxide and the solvent viscosity on the pulverization are analyzed experimentally.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.41-44
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• 1995

The purpose of this study is analyze to the properties of high fluidity concrete(W/C 35~50%) with the dosage of viscosity agent(Hydroxy Propyl Methyl Cellulose ; HPMC ; 15U), From the resuls, flowability was good about 200g/㎥. segregation-resisibility and placeability were good upward 300g/㎥, To synthetic, the dosage of viscosity agent are discovered best in 200~400g/㎥

• 한국세라믹학회지
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• 제49권6호
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• pp.542-548
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• 2012

The viscosity of a ceramic slurry depends on the slurry concentration, particle shape and size, hydrodynamic interactions, temperature, shear rate, pre-treatment condition and the method of measurement with the selected equipment. Representative ceramic slurries with low to high viscosity levels are selected from colloidal silica, barium titanate slurry and glass frit paste. Rotational rheometers and vibrational viscometers are used to compare the measured viscosity for various ceramic slurries. The rotational rheometer measured the viscosity according to the change of the shear rate or the rotational speed. On the other hand, the vibrational viscometer measured one point of the viscosity in a fixed vibrational mode. The rotational rheometer allows the measurement of the viscosity of a ceramic paste with a viscosity higher than 100,000 cP, while the vibrational viscometer provides an easy and quick method to measure the viscosity without deformation of the ceramic slurry due to the measurement method. It is necessary to select suitable equipment with which to measure the viscosity depending on the purpose of the measurement.