The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Kiichiro Mukai - One of the best experts on this subject based on the ideXlab platform.
-
measurement of rheological properties for smectic a liquid crystal by using ultrasonic rheometer and Rotational Viscometer
Progress in Organic Coatings, 1997Co-Authors: Kiichiro Mukai, Naoki Makino, Hiroyuki Usui, Takeshi AmariAbstract:Abstract The relationship between the rheological properties and the alignment direction of liquid crystals was studied using a Rotational Viscometer and an ultrasonic rheometer. 4-Cyano-4′- n -octylbiphenyl (8CB) was used for the sample. The measurements of viscosity for 8CB were carried out using the Rotational Viscometer having parallel plate geometry. The parallel plates were made from glass and covered by polyimide film with rubbing to align the liquid crystal molecules. The oriented structure of 8CB was examined using a polarizing microscope optical system which was built in the Rotational Viscometer. When the direction of shearing was perpendicular to the layers of smectic 8CB, the apparent viscosity was higher than that in the case of no-rubbing. Viscoelastic properties at ultrasonic frequency (3 MHz) were examined by the ultrasonic rheometer using a fused-quartz delay line. When the shear wave vibration was perpendicular to the smectic layers, G′ was observed. However, when the shear wave vibration was parallel to the smectic layers, G′ was not observed.
Fulong Liao - One of the best experts on this subject based on the ideXlab platform.
-
the criteria for evaluating shear stress measuring range and the lowest measurable shear stress of Rotational Viscometer
Clinical Hemorheology and Microcirculation, 2009Co-Authors: Qixue Qi, Yufen Li, Fulong LiaoAbstract:In the Guidelines for measurement of blood viscosity and erythrocyte deformability by ICSH in 1986, it points out that the Viscometer for hemorheology should ideally be able to operate over a wide range of shear conditions, and for a constant shear-rate Viscometer a high-shear measurement at 200/second and a low-shear measurement at 1/second (or shear-rates approximating to these values if they are not attainable in the instrument used) should be made [1]. It also states that a high degree of instrument sensitivity is required for measuring viscosity at low shear. A suitable shear stress measuring range and a high degree sensitivity at low shear-rate are required for measuring blood viscosity. Unfortunately, many of the industrial Viscometers do not meet the requirements [2]. In fact, the lowest measurable shear-stress is a critical parameter for a Rotational blood Viscometer. However, the criteria for evaluating shear measuring range and the lowest measurable shear-stress are not clearly described in the guidelines. We proposed double 5% criteria for the evaluation, i.e. less than 5% error in viscometry and less than 5% in coefficient of variation as “measurable” criteria. Recently, we experienced the criteria with a domestic Rotational Viscometer (anonym for avoiding possible conflicts in commercial interests). The Viscometer is a shear-rate controlled Rotational Viscometer with double gap cylinder sensor designed for measuring blood and plasma viscosities. A suspending torsion strip is employed as the shearstress sensing element. The Viscometer works in the shear-rate range of 1–220/second and shear-stress range of 10–2000 mPa according to the specifications described in the user’s manual. The sensor temperature is controlled at fixed 37 ± 0.5◦C. The required sample volume is 1.2 ml. We selected a number of standard oils (provided by the Chinese Academy of Metrology), including GBW(E)130251, GBW(E)130253, GBW(E)130254 and GBW(E)130255, for evaluation of the viscome-
Takeshi Amari - One of the best experts on this subject based on the ideXlab platform.
-
measurement of rheological properties for smectic a liquid crystal by using ultrasonic rheometer and Rotational Viscometer
Progress in Organic Coatings, 1997Co-Authors: Kiichiro Mukai, Naoki Makino, Hiroyuki Usui, Takeshi AmariAbstract:Abstract The relationship between the rheological properties and the alignment direction of liquid crystals was studied using a Rotational Viscometer and an ultrasonic rheometer. 4-Cyano-4′- n -octylbiphenyl (8CB) was used for the sample. The measurements of viscosity for 8CB were carried out using the Rotational Viscometer having parallel plate geometry. The parallel plates were made from glass and covered by polyimide film with rubbing to align the liquid crystal molecules. The oriented structure of 8CB was examined using a polarizing microscope optical system which was built in the Rotational Viscometer. When the direction of shearing was perpendicular to the layers of smectic 8CB, the apparent viscosity was higher than that in the case of no-rubbing. Viscoelastic properties at ultrasonic frequency (3 MHz) were examined by the ultrasonic rheometer using a fused-quartz delay line. When the shear wave vibration was perpendicular to the smectic layers, G′ was observed. However, when the shear wave vibration was parallel to the smectic layers, G′ was not observed.
N N Firsov - One of the best experts on this subject based on the ideXlab platform.
-
interaction between gravitational sedimentation and shear diffusion in a suspension moving in a Rotational Viscometer gap
Fluid Dynamics, 1991Co-Authors: E S Losev, N V Netrebko, S A Regirer, A S Stepanyan, N N FirsovAbstract:The start up behavior of a concentrated suspension of nonaggregating settling particles in a Rotational Viscometer is examined. The results of one of the experiments are presented.
-
in a suspension moving in a Rotational Viscometer gap
1991Co-Authors: E S Losev, N V Netrebko, S A Regirer, A S Stepanyan, N N FirsovAbstract:Work on concentrated suspensions in Rotational Viscometers has led to the discovery of two outwardly different, but physically related effects. The first of these corresponds to the case in which the true density of the particles is somewhat higher than that of the carrier phase; then the shear flow in the instrument affects the particle sedimentation rate [i, 2], modifying the aggregation kinetics and creating a fluctuating disordered motion of the particles which, like Brownian diffusion, counteracts the gravitational sedimentation [3]. The second effect consists in that for a suspension of neutrally buoyant particles a very slow fall in the measured value of the viscosity is observed [4, 5]. This initially puzzling effect subsequently received a simple explanation: the viscosity falls as a result of the decrease in the working gap of the concentration of the particles, which owing to the shear-induced diffusion escape from the working gap into the bottom zone, where the shear rates (and the intensity of the fluctuating motion of the particles) are small [5]. In [5] this effect was successfully used to estimate the shear diffusion coefficient from the fall in viscosity. In general, the competition between the gravitational sedimentation and diffusion of the particles should lead to the establishment of characteristic vertical concentration profiles. A simple example of the theoretical analysis of this situation is the derivation of the well-known "barometric formula" [6], which presupposes the constancy of the sedimentation rate and the diffusion coefficient. For concentrated coloidal systems both these parameters depend on the concentration in a special way; an asymptotic theory, which takes this dependence into account, was developed in [7]. The impossibility of directly extending the results of [7] to the motion of a suspension is due both to the different concentration dependence and to the need to take the aggregation kinetics of the particles also into consideration. The latter were previously included in the description of sedimentation in a Viscometer without allowance for diffusion [8]. The case in which aggregation is taken into account as a factor in the formation of a dense sediment but not in the shear flow was considered in [9]. i. We will consider the Rotational motion of a concentrated incompressible particle suspension in a narrow (with negligibly small curva%ure) vertical gap between coaxial cylinders, using the cylindrical coordinate system (r, 9, z), where the z axis is directed vertically upwards. The peripheral velocity u~ and shear rate Oa~/ar distributions in this gap may be assumed to be steady, if the given angular velocity of the moving cylinder is constant. In this case the shear rate ~f=--iiOu~#r I is constant and does not depend on the properties of the suspension, whereas the shear stresses T=~(I])~a~/Or may vary together with the volume particle concentration H, which in such a Couette flow depends on time and the vertical coordinate, conforming to the general conservation equation
Qixue Qi - One of the best experts on this subject based on the ideXlab platform.
-
the criteria for evaluating shear stress measuring range and the lowest measurable shear stress of Rotational Viscometer
Clinical Hemorheology and Microcirculation, 2009Co-Authors: Qixue Qi, Yufen Li, Fulong LiaoAbstract:In the Guidelines for measurement of blood viscosity and erythrocyte deformability by ICSH in 1986, it points out that the Viscometer for hemorheology should ideally be able to operate over a wide range of shear conditions, and for a constant shear-rate Viscometer a high-shear measurement at 200/second and a low-shear measurement at 1/second (or shear-rates approximating to these values if they are not attainable in the instrument used) should be made [1]. It also states that a high degree of instrument sensitivity is required for measuring viscosity at low shear. A suitable shear stress measuring range and a high degree sensitivity at low shear-rate are required for measuring blood viscosity. Unfortunately, many of the industrial Viscometers do not meet the requirements [2]. In fact, the lowest measurable shear-stress is a critical parameter for a Rotational blood Viscometer. However, the criteria for evaluating shear measuring range and the lowest measurable shear-stress are not clearly described in the guidelines. We proposed double 5% criteria for the evaluation, i.e. less than 5% error in viscometry and less than 5% in coefficient of variation as “measurable” criteria. Recently, we experienced the criteria with a domestic Rotational Viscometer (anonym for avoiding possible conflicts in commercial interests). The Viscometer is a shear-rate controlled Rotational Viscometer with double gap cylinder sensor designed for measuring blood and plasma viscosities. A suspending torsion strip is employed as the shearstress sensing element. The Viscometer works in the shear-rate range of 1–220/second and shear-stress range of 10–2000 mPa according to the specifications described in the user’s manual. The sensor temperature is controlled at fixed 37 ± 0.5◦C. The required sample volume is 1.2 ml. We selected a number of standard oils (provided by the Chinese Academy of Metrology), including GBW(E)130251, GBW(E)130253, GBW(E)130254 and GBW(E)130255, for evaluation of the viscome-
