• Title, Summary, Keyword: viscosity

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Hemorheology and Cardiovascular Disease

  • Cho, Young-I.;Kensey, Kenneth R.
    • 순환기질환의공학회:학술대회논문집
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    • pp.3-18
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    • 2002
  • Hemorheology plays an important role in atherosclerosis. Hemorheologic properties of blood include whole blood viscosity, plasma viscosity, hemaocrit, RBC deformability and aggregation, and fibrinogen concentration in plasma. Blood flow is determine by three parameters (pressure, lumen diameter, and whole blood viscosity), whole blood viscosity is one of the key physiological variables. However, the significance of whole blood viscosity has not yet not been fully appreciated. Whole blood viscosity has a unique property, non-Newtonian shear-thinning characteristics, which is primarily due to the presence of RBCs. Hence, RBC deformability and aggregation directly affect the magnitude of blood viscosity, and any factors or diseases affecting RBC characteristics influence blood viscosity. Therefore, on can see that whole blood viscosity is the causal mechanism by which traditional risk factors such as hypertension, hyperlipidemia, smoking, exercise, obesity, age, and gender are related to atherogenesis. In this regard, we included whole blood viscosity in the three key determinants of injurious pulsatile flow that results in mechanical injury and protective adaptation in the arterial system. Because whole blood viscosity is a potential predictor of cardiovascular diseases, it should be measured in routine cardiovascular profiles. Incorporating whole blood viscosity measurements into a standard clinical protocol could improve our ability to identify patients at risk for cardiovascular disease and its complications.

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A Calculation for the Viscosity of Fluid at the Critical Point

  • Kim, Won-Soo;Chair, Tong-Seek
    • Bulletin of the Korean Chemical Society
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    • v.23 no.11
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    • pp.1524-1526
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    • 2002
  • It is very difficult to measure the fluid viscosity at the critical point, there are seldom found experimental values of fluid viscosity at the critical point. Few theories can explain the critical viscosity quantitatively. A theory of viscosity previously proposed by authors10 is applied to the fluid at the critical point. This theory can be simplified as a simple form with no adjustable parameters, allowing for easy calculation. Viscosities at the critical point for some substances have been calculated, and calculated results are satisfactory when compared with the observed values.

Viscosity Characteristics of Waste Cooking Oil with Ultrasonic Energy Irradiation

  • Kim, Tae Han;Han, Jung Keun
    • Journal of Biosystems Engineering
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    • v.37 no.6
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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.

The Relationship between Viscosity of Soluble Dietary Fiber and their Hypoglycemic Effects (수용성 식이섬유소의 점도가 혈당강하에 미치는 영향)

  • 김은희
    • Journal of Nutrition and Health
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    • v.29 no.6
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    • pp.615-621
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    • 1996
  • Experiments were carried out in humans to assess the relationship between viscosity and post-prandial glucose response of soluble fibers. Eight(3 male and 5 female) healthy individuals were tested for their glucose response after taking control meals or 3 test fiber meals of different viscosities. Meal viscosity of the test food was adjusted to be between 200 and 70, 000 cps. There was a significant increase in post-prandial glucose response(p=0.01) in control meals by solely increasing the volume of water. Fiber with the highest viscosity konjac mannan demonstrated the lowest relative glucose response(70.1$\pm$6.6), followed by medium viscosity xanthan (79.3$\pm$8.7)and low viscosity psyllium (86.3$\pm$10.5). The difference is significant at the level of p<0.05. However, no significant difference in relative glucose response of the same fiber was found when the 4 levels of water were added to make different meal viscosity of each fiber (p=0.476). This result suggested that hypoglycemic action of soluble dietary fibers is related to fiber viscosity rather than meal viscosity.

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Solution Properties of Chitosan Polymer(I) - Variation of Viscosity with Temperature and Time in Acetic Solution- (키토산 고분자의 용액 물성(I) -초산수용액에서 온도와 경과시간에 따른 점도 변화-)

  • 김홍성;이순장
    • Textile Science and Engineering
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    • v.41 no.5
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    • pp.342-346
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    • 2004
  • Viscosity variation ensuing from processing temperature and time elapsed in acetic solution of chitosan was investigated by rotary viscometer. The solution showed a typical behavior of pseudoplastic liquid where the gradient of shear stress decreases as strain rate increases. The apparent viscosity decreased as chitosan polymer degraded with temperature rise and time elapsed in the solution. And the decrease in viscosity occurred rapidly in a fixed time interval at each temperature. The proportionality of viscosity to temperature was confirmed by temperature superposition curve that was obtained with the temperature dependence shift factor a$_{T}$ in WLF equation. Intrinsic viscosity was linearly proportional to apparent viscosity within a fixed range depending on strain rate. The activation energy of chitosan was about 55.2 KJ/mole in the acetic solution, which was calculated from intrinsic viscosity based on the Andrade-Eyring equation.n.

Rheological Characterization of Aqueous Poly(Ethylene Oxide) Solutions(II)-Comparison of Steady Flow Viscosity with Dynamic and Complex Viscosities- (폴리에틸렌옥사이드 수용액의 유변학적 특성 평가(II)-정상류점도와 동적점도, 복소점도의 상관관계-)

  • 송기원;장갑식;김철범;이장우;백종승
    • Textile Science and Engineering
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    • v.35 no.8
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    • pp.480-489
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    • 1998
  • Using a Rheometrics Fluids Spectrometer (RFS II), the steady shear flow viscosity and dynamic viscoelastic properties of aqueous poly(ethylene oxide) (PEO) solutions have been measured over a wide range of shear rate and angular frequency. In this paper, the relationship between the steady flow viscosity and dynamic viscosity was investigated, and the property of a conversion factor was determined from the data. Further, the validity of the Cox-Merz rule was examined by comparing the steady flow viscosity and the magnitude of the complex viscosity. The influence of a coil overlap parameter on the applicability of the Cox-Merz rule was discussed finally. Main results obtained from this study can be summarized as follows : (1) At higher range of shear rate and angular frequency, tile dynamic viscosity decreases more rapidly than does the steady flow viscosity. A conversion factor between the steady flow viscosity and dynamic viscosity increases with increasing shear rate and angular frequency (2) At relatively lower polymer concentration, the steady flow viscosity is higher than the complex viscosity, which is reversed at highly concentrated solutions. (3) A coil overlap parameter has an effect on the validity of the Cox-Merz rule. Especially, the use of a coil overlap parameter including the molecular weight distribution can be regarded as an effective method to evaluate the Cox-Merz rule for all kinds of linear polymer solutions.

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Acoustic Viscosity Characteristics of Oils with High Molecular Weight VI Improver Additives (고분자량 점도지수향상제가 첨가된 오일의 음향점도 특성)

  • Kong, H.;Ossia, C.V.;Han, H.G.
    • Tribology and Lubricants
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    • v.25 no.4
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    • pp.236-242
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    • 2009
  • Oil viscosity is one of the important parameters for machinery condition monitoring. Basically, it is expressed as kinematic viscosity measured by capillary flow and dynamic or absolute viscosity measured by rotary shear viscometry. Recently, acoustic wave techniques appear in the market, measuring viscosity as the product of dynamic viscosity and density. For Newtonian fluids, knowledge of density allows conversion from one viscosity parameter to the other at a specific shear rate and temperature. In this work, oil samples with different chain lengths of viscosity index (VI) improvers and concentrations were examined by different viscometric techniques. Results showed that acoustic viscosity measurements give misleading results for oil samples with high molecular weight VI improvers and at low temperatures ${\leq}40^{\circ}C$.

In-line Oil Viscosity Sensor Implementing An Elastomagnetic Ribbon Resonance (자기탄성체 리본의 공진을 이용한 인-라인 오일 점도센서)

  • Kong, H.;Han, H.G.;Markova, L.V.
    • Tribology and Lubricants
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    • v.26 no.2
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    • pp.97-104
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    • 2010
  • A new magnetoelastic technique of oil viscosity measurement, where the oil viscosity is estimated by frequency shift of natural oscillations of magnetoelastic ribbon, is implemented in this study. Laboratory tests of the detector prototype are performed for measurement of viscosity of base synthetic and mineral oils. It was found that measurement accuracy was better when damping factor was estimated in comparison with accuracy of frequency of damped oscillations. Thus the oil viscosity was calibrated as a function of number of pulses of the damped oscillations of magnetoelastic ribbon. Result generally showed that developed detector is promising for in line oil viscosity measurement in wide viscosity range from 10 cSt up to 600 cSt, while the viscosity measurement was relatively instable when the viscosity of test oil was over 400 cSt.

Comparison of the Viscosity of Ceramic Slurries using a Rotational Rheometer and a Vibrational Viscometer (회전형 레오미터와 진동형 점도계를 이용한 세라믹 슬러리의 점도 비교)

  • Ji, Hye;Lim, Hyung Mi;Chang, Young-Wook;Lee, Heesoo
    • Journal of the Korean Ceramic Society
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    • v.49 no.6
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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.

Characteristics of Shear-Thinning Fluid Viscosity under Traversal Vibration (진동장에서의 전단박화 유체 점도의 특성 연구)

  • Ku Yun-Hee;Lee Ji-Hyung;Shin Sehyun
    • Proceedings of the KSME Conference
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    • pp.317-320
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    • 2002
  • The effect of vibration on the viscosity of a shear-thinning fluid was investigated with a newly designed pressure-scanning capillary viscometer. The viscometer was designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time. Low frequency vibration was applied perpendicularly to the direction of the flow. The effect of the transversal vibration was investigated for both Newtonian fluids and non-Newtonian fluids. The experimental results showed that the vibration had no effect on the viscosity of the Newtonian fluids. However, the vibration caused a significant reduction of the shear-thinning fluid viscosity. The viscosity reduction was strongly dependent on both vibration frequency and shear rate. In addition, the viscosity reduction was affected by the amplitude of vibration, and, the bigger amplitude applied, the more viscosity reduction occurred.

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