• 한국대기환경학회지
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• 제32권4호
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• pp.349-359
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• 2016

Researchers have traditionally assumed that aerosol particles containing secondary organic aerosols (SOAs) are to be in liquid state with low viscosity even at low relative humidity. However, recent measurements showed that SOAs can have high viscosity under certain conditions. Herein, new different techniques for measurements of viscosities of SOA particles are introduced. Moreover, laboratory studies for the viscosities and the phases of biogenic SOAs produced by ${\alpha}$-pinene, isoprene, limonene, and ${\beta}$-caryophyllene of atmospheric relevance are reviewed. Future studies for determination of the phases of atmospheric aerosol particles are also suggested.

• 대한기계학회논문집B
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• 제27권9호
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• pp.1327-1334
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• 2003

Flow characteristics of the fluid laden with many particles in the two-dimensional channel are investigated using the Navier-Stokes equations coupled with the equation of motion of particles by direct numerical simulation. A four-step fractional step method with Crank-Nicolson scheme and ALE technique is used for P2P1 mixed finite element method. The motion and distribution of particles in the fluid is virtually described as a result of direct numerical simulation and the increase of viscosity is compared with theoretical equations. The effect of channel height on the relative viscosity and the tubular pinch effect are discussed.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.99-100
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• 2002

Radial, tilting-pad proceeding bearings are applied in high speed rotating machines operating at stable small and mean loads and the peripheral speeds of proceeding reaching 150 m/s. The operation of bearing can be determined by static characteristics including the oil film pressure, temperature and viscosity distributions, minimum oil film thickness, load capacity, power loss, oil flow. The operation of 5-lobe tilted-pad proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions habe received by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss. oil flow, maximum oil film pressure, maximum temperature were computed for different sets of bearing geometric parameters as: bearing length to diameter ratio, pad angular length and width as well as pad relative clearance.

• Macromolecular Research
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• 제17권12호
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• pp.943-949
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• 2009

A highly dispersed W/O emulsion of silicone oil (cyclomethicone)/water system was prepared with a nonionic surfactant. The surface and interfacial tension between the oil and water were characterized in terms of the droplet size distribution and viscosity change of the emulsion. When the dispersed phase concentration was relatively high, the viscosity of the emulsion was rapidly increased and the droplet size of the emulsion was decreased. The rheological behavior of the emulsion system showed non-Newtonian and shear thinning phenomena depending upon the content of the dispersed phase. The droplet size of the emulsion was decreased with increasing surfactant content and water concentration. The relative viscosity of the emulsion was better predicted with the Choi-Schowalter model than with the Taylor model. The value of the complex modulus increased with increasing surfactant concentration. The linear viscoelastic region was expanded with a dispersed phase concentration. According to the change in the viscosity, the behavior was classified into three distinct regions: [I] linear viscoelastic, [II] partially viscoelastic, and [III] viscous. The creep/recovery behaviors in each region were characterized.

• 한국도로학회논문집
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• 제16권1호
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• pp.31-39
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• 2014

PURPOSES : Surface treatment material for pavement preventive maintenance should be inspected field applicability. This study(Part II) aimed to checkup coating characteristics and performance analysis using lab and field tests. The hydrophobic - low viscosity filling material for pavement preventive maintenance is presented in Part I, which is a series of companion study. METHODS : Relative comparison between general asphalt mixtures and surface treatment asphalt mixtures are analyzed and measured for the field application such as indirect tensile strength ratio(TSR), abrasion resistance, crack propagation resistance, temperature resistance, coating thickness, permeability resistance and skid resistance in terms of british pendulum number(BPN). RESULTS : It is found that TSR, crack propagation resistance and permeability resistance is increased as against uncoated asphalt specimen. Abrasion resistance and temperature resistance is secured from the initial coating thickness point of view, which is about 0.2~0.3mm. Skid resistance on the surface treatment pavement is satisfied with the BPN criteria of national highway because of exposed aggregate and crack sill induced pavement deterioration and damage cracks. CONCLUSIONS : The hydrophobic - low viscosity surface treatment material for pavement preventive maintenance is validated on field applicability evaluation based on quantitative analysis of coating thickness and performance analysis using lab and field tests.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2105-2119
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• 2015

This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.124-127
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• 2016

Humidity calibration for a temperature-stable quartz oscillator (TSQO) was investigated to exclude the influences of relative humidity on the TSQO output in order to use the corresponding devices outdoors. The TSQO output is a voltage that is inversely proportional to the electric impedance of the quartz oscillator, which depends on the viscosity and density of the measured gas. The TSQO output was humidity calibrated using its humidity dependence, which was obtained by varying the relative humidity (RH) from 0 to 100 RH% while other conditions were kept constant. The humidity dependencies of the TSQO output were fit by a linear function. Subtracting the change in the TSQO output induced by the change in humidity, calculated with the function from the experimentally measured TSQO output for a range of 0-100RH%, eliminated the influence of humidity on the TSQO output. The humidity calibration succeeded in reducing the fluctuations of the TSQO output from 0.4-3% to 0.1-0.3% of the average values for a range of 0-100RH%, at constant temperatures. The necessary stability of the TSQO output for application in hydrogen sensors was below one-third of the change observed for a hydrogen leakage of 1 vol.% hydrogen concentration, corresponding to 0.33% of the change in each background. Therefore, the results in this study indicate that the present humidity calibration effectively suppresses the influence of humidity, for the TSQO output for use as an outdoor hydrogen sensor.

• 한국자기학회지
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• 제11권4호
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• pp.157-162
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• 2001

Sm-Co계 플라스틱 자석 제조를 위한 사출 성형용 컴 파운드의 제조법을 연구하기 위해 미세분말과 조대분말을 혼합하여 자성분말의 입도 변화, 배합비 및 부피분율에 따른 컴파운드의 유변학적 특성을 조사하였다. 조대분말의 평균입도가 증가하면 분말의 충진율이 증가하여 컴파운드의 점도가 감소하였다. 그러나 미세분말의 평균입도가 작아지는 경우, 미세분말들간의 응집성으로 인하여 오히려 점도가 증가하였다. 기계적으로 분쇄된 Sm-Co계 분말의 경우, 125~75 $\mu\textrm{m}$ 크기의 조대분말과 평균입도 4.9 $\mu\textrm{m}$인 미세분말을 혼합하여 제조된 컴파운드의 점도는 분말의 배합비에 의존하며 조대분말을 60%혼합한 경우 가장 낮은 점도를 나타냈다. 이는조대분말의 양이 60 %일 때 자성분말의 충진율이 최대가 됨을 의미한다. 자성분말의 부피분율에 따른 컴파운드의 점도는 유변학적 모델을 잘 만족시켰으며 사출 성형이 가능한 Sm-Co계 자성분말의 최대 부피분율은 약 66 %이었다.

• 대한화학회지
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• 제24권3호
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• pp.209-217
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• 1980

요소 1,3-디메틸요소(DMU), 아세트아미드, 프로피온아미드의 상대점도와 삼투계수를 dimethylsulfoxide(DMSO), 메탄올, 에탄올 및 물용액에서 $25^{\circ}$C와 $45^{\circ}$C에서 각각 측정하였다. 수용액에서 각 용질의 점도증가량은 분몰랄부피가 증가하면서 증가하였으나 물아니 용액에서는 오히려 감소하였다. 또한 요소의 점도 증가량은 수용액에서는 DMU보다 작았으나, 물아닌 용액에서는 DMU보다 컸다. 그러나 아미드류는 어느 용매에서나 거의 같은 점도증가량을 나타내었다. 요소수용액에서 삼투계수는 DMU 수용액보다 컸으며, 물아닌 용액에서 요소용액은 DMU보다 Raoult의 법칙에서 크게 벗어났다. 이러한 사실로부터 요소는 DMSO 용액에서 자체회합을 크게 일으키고 있으며 알코올용액에서는 DMU보다는 큰 정도의 용매-용질상호작용, 수용액에서는 용매구조를 파괴하고 있음을 알았다. 아세트아미드나 프로피온아미드는 수용액이나 DMSO 용액에서보다 알코올용액에서 더 크게 용매구조를 파괴하고 있음을 알았다.

• 한국식품영양과학회지
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• 제27권5호
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• pp.821-826
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• 1998

Functional properties of mucilage and pigment extracted from Opuntia ficus-indica var. saboten were determined at various temperatures, pHs and alcohol concentrations. The crude mucilage extracted from pickly pear showed pH 4.2, 0.14% total acidity and 8.1% total soluble solid content(w/w, wet basis). Polysaccharide was purified from mucilage extract by isopropanol precipitation. Intrinsic viscosity of polysaccharide was 18.1dl/g and decreased with increasing KCl concentration. Relative viscosity and color stability of mucilage extract were determined with capillary viscometer and spectrophotometer at 534nm, respectively. In additions of 1~20%(v/v) ethanol, the red pigment of mucilage extract was very stable, but relative viscosity, increased gradually. For heating above 7$0^{\circ}C$, the stability of red pigment decreased drastically, but rheological property of mucilage was not changed. During storage, the red pigment was extremely unstable at above pH 8.3. At both pH 3.0 and pH 4.2, the red pigment was the most stable at 4$^{\circ}C$ for 18 days. In the case of storage at 37$^{\circ}C$, pigment of mucilage extract at pH 3.0 was destroyed more quickly than that at pH 4.2. Natural mucilage extract(pH 4.2) showed the good stability of red pigment at 3$0^{\circ}C$ for 10 days.