Nonstationary method of measuring flow curves of low-viscosity settling suspensions

The kinematics of fluid flow in the measuring unit of a rotational viscometer with variation in the rotational velocity by the exponential law has been considered. The asymptotic expression for calculation of the rate of shear and the dimensionless parameter determining the regime of steady-state flow have been obtained. Experimental check of this method has been carried out. It has been shown that exponential variation in the rotational velocity of the measuring unit makes it possible to cut the time of measurement of the flow curve and to improve the accuracy of measurement in the region of low shear rates.     

采用拟牛顿流体原理确定冶金熔体流动特性的方法

根据冶金熔体的物理化学性质，可以确定冶金熔体是属于性流体，利用同一牛顿流体在任何剪切速率下的粘度桢的这一特点，给出了一个用拟牛顿流体原理检验冶金熔体的流动特性的方法。钭普通固定转速高温粘度计改造为可调转速，可同熔体的流动特性，进而能确定熔体是否为牛顿流体。     

Effect of Human Serum on the pH-Induced Rheological Properties of Polymethacrylic Acid

Abstract

The use of polyelectrolytes have been proposed for the production of pH sensitive microcapsules and liposomes. Polymethacrylic acid (PMA) has been synthesized for this purpose and has been shown to be extremely effective in increasing the release from these delivery systems a pH's below 6.0 in distilled water. The current studies show that serum and ionic strength conditions dramatically effect the rate and extent of any PMA conformational changes. The rate of conformational change was found to be proportional to time in contrast to the cube root of time reported within molecular probe investigations. Conformational changes in this study have been monitored using a cone/plate rotational viscometer. The results of this study suggest that under biologically relevant conditions, PMA (Mv 400,000) may not be suitable for use in pH sensitive delivery systems but may have other important uses.     

Effect of Human Serum on the pH-Induced Rheological Properties of Polymethacrylic Acid

The use of polyelectrolytes have been proposed for the production of pH sensitive microcapsules and liposomes. Polymethacrylic acid (PMA) has been synthesized for this purpose and has been shown to be extremely effective in increasing the release from these delivery systems a pH's below 6.0 in distilled water. The current studies show that serum and ionic strength conditions dramatically effect the rate and extent of any PMA conformational changes. The rate of conformational change was found to be proportional to time in contrast to the cube root of time reported within molecular probe investigations. Conformational changes in this study have been monitored using a cone/plate rotational viscometer. The results of this study suggest that under biologically relevant conditions, PMA (Mv 400,000) may not be suitable for use in pH sensitive delivery systems but may have other important uses.     

改性M-CMHPC增稠PVA乳液体系的流变特性

用旋转粘度计研究了改性羧甲基羟丙基纤维素(M-CMHPC)增稠聚醋酸乙烯(PVA)乳液体系的流变特性。与离子型羧甲基纤维素和非离子型羟乙基纤维素相比较,在实验的增稠剂浓度范围内,改性M-CMHPC增稠PVA乳液体系呈现非牛顿流体Bingham塑性流型,具有较明显的屈服值、塑性粘度和触变性。     

Cold stepping drive for the ISO/LWS

Development work has begun on an interchange mechanism for the pair of Fabry-Perot interferometers proposed for the Long Wavelength Spectrometer planned as one of the focal plane instruments for the Infrared Space Observatory. The two Fabry-Perot assemblies will be mounted on a balanced wheel which is to be carried on a shaft mounted in ball bearings which have been MoS₂ treated at the European Space Tribology Laboratory. Cryogenic testing is in hand at the Institute of Cryogenics, University of Southampton, UK. A ring gear on the wheel will be driven from the output pinion of a stepping motor. At a later stage in the project a choice will be made among all available cold motors with suitable performance. In the meantime, a prototype has been built of a special cryogenic permanent magnet stepping motor intended to operate on a current of a few milliamperes. The Paper describes constructional features of the drive, together with early results for the motor prototype.     

Boundary element simulation of inviscid flow around an oscillatory foil with vortex sheet

The dynamic performance of a rigid foil with harmonic vertical and rotational motions in fluid flow has been studied through velocity potential theory. A boundary element based time stepping scheme is introduced to simulate the flow around the foil and the vortex wake. The body surface condition is satisfied on the exact foil surface and the motion and deformation of the wake sheet shed at the trailing edge is tracked. Kelvin condition is satisfied and a Kutta condition for the unsteady motion is proposed to circumvent the singularity at the trailing edge. Point vortex, which is reduced from wake vortex dipole, is introduced to approximate the vorticity. The performance of foil NACA0012 with harmonic vertical and rotational motions are studied extensively; the propulsion/swimming mode, energy harvesting mode and the flying mode are analysed in detail.     

Material flow and mechanical behaviour of dissimilar AA2024-T3 and AA7075-T6 aluminium alloys friction stir welds

The scope of this investigation is to evaluate the effect of joining parameters on the mechanical properties, microstructural features and material flow of dissimilar aluminium alloys (3 mm-thick AA2024-T3 and AA7075-T6 sheets) joints produced by friction stir welding. Mechanical performance has been investigated in terms of hardness and tensile testing. Material flow using the stop action technique has also been investigated in order to understand the main features of the mixing process. No onion ring formation has been observed; the boundary between both base materials at the stir zone is clearly delineated, i.e., no material mixing is observed. A non-stable rotational flow inside the threads has been identified due to the formation of a cavity on the rear of the pin. Microstructural observation has revealed the development of a recrystallised fine-grained stir zone, with two different grain sizes resulting from the two different base materials.     

Comparison of Several Diffusion Equations in the Calculation of Viscosity and its Relation to Dissolution Rate

The viscosity of polymeric solutions as measured by a rotational viscometer may not be the viscosity of the environment through which a solute molecule diffuses. By use of the Stokes-Einstein equation a viscosity, which is not affected by the mechanics of the viscometer, may be calculated if the size and diffusivity of the solute molecule are determined. The values of such viscosity calculated by using several diffusion equations compare favorably with the value calculated with the Stokes-Einstein equation. The dissolution rates of benzoic acid in aqueous solutions of three non-ionic suspending agents is related to the viscosity.     

Rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser

An experimental study of a rapidly tuning miniature transversely excited atmospheric-pressure CO2 laser is reported. To rapidly shift laser wavelengths over selected transitions in the 9-11 microm wavelength region, we have utilized a high-frequency stepping motor and a diffraction grating. The laser is highly automated with a monolithic microprocessor controlled laser line selection. For the achievement of stable laser output, a system of laser excitation with a voltage of 10 kV, providing effective surface corona preionization and allowing one to work at various gas pressures, is utilized. Laser operation at 59 emission lines of the CO2 molecule rotational transition is obtained and at 51 lines, the pulse energy of laser radiation exceeds 30 mJ. The system can be tuned between two different rotational lines spanning the wavelength range from 9.2 to 10.8 microm within 10 ms.     

Viscosities of molten alkali-metal bromides and iodides

Viscosities of molten alkali-metal bromides and iodides, whose reported values are scattered, have been measured by the use of a capillary viscometer made of quartz which is newly designed to obtain a high precision. The viscometer consists of the quartz capillary with a funnel of the suspended level type, and the melt is sealed in it under vacuum. The total error in the measurement is estimated to be within 0.7% at high temperatures. Viscosities of all the alkalimetal bromides and iodides show similar values at a constant temperature. Viscous flow behaviors of all the alkali-metal halides are discussed based on the activation energy and the hard sphere model. The apparent activation energy increases with an increase in the melting temperature of the salt. The viscosity of the alkali-metal halide melt at the melting temperature increases as the ratio of hard sphere volume to hole volume calculated from the surface tension.     

双极性步进电机细分驱动器的设计与实现

论述了一种双极性步进电动机驱动器的工作原理，该驱动器能较好地改善步进电动机的运行性能，具有实用性强，结构简单，成本低的优点。针对实际调试中出现的问题进行分析后，提出了对策；最后给出了试验结果。     

Relationship of dissolution rate in anionic polymeric solutions to viscosity

The influence of viscosity on the dissolution rate of m-acetotoluidide in aqueous solutions of acacia, gelatin type B, sodium carboxymethylcellulose, sodium alginate and xanthan gum was investigated. The viscosity was measured by a rotational viscometer. The dissolution rates decreased as the viscosities of solutions of anionic polymers increased. The curves representing the relationship of dissolution rate and viscosity varied for each polymeric solution depending on the structural characteristics of the polymer.     

Thermoviscoelastic Properties of Phenolic Resin/Polymeric Isocyanate Binder Systems

Thermoviscoelastic properties of phenolic resin/polymeric isocyanate binder systems (i.e., ISOCURE Parts I and II) are reported. The effects of blend composition and the reaction between the binders on these properties of the systems are also considered. The viscous properties of binders and their blends were measured using computer-controlled rotational viscometers (Brookfield HBDV-II+ viscometer and HAAKE Rotovisco 12 rheometer in the cone-and-plate mode). The elastic properties of the phenolic urethane polymer (the blend composition) were measured by means of a modified jet thrust technique based on measuring the thrust of a liquid jet. Although both binders are Newtonian liquids, their blends exhibit viscoelastic non-Newtonian fluid flow behavior. The viscosity of the blends increases both with time and with an increasing Part I content and may reach comparatively high values at high values of either parameter. This behavior is explained as a result of the rubbery nature of the phenolic urethane polymer, which was produced as a product of reaction between Part I and Part II. The use of the jet thrust method allowed determination of the relaxation time of various blends at different shear rates.     

基于单片机的改进型五相混合式步进电机驱动器设计

在高性能纺织机械尤其是电脑绣花机中,步进电机是广泛应用的执行部件.电脑绣花机系统中现有五相混
合式步进电机驱动器存在诸多不足之处低频转矩振荡、高频输出转矩不足和多电源供电等.在分析现有步进电机
驱动器的基础上,结合理论分析,设计出一种基于单片机的改进型五相混合式步进电机W动器.该驱动器使用单一
电源供电,采用三相励磁PWM输出方式,改善了驱动的矩频特性,在电脑绣花机系统中投人应用取得良好效果.     

Non-newtonian viscosity of polymer-modified bitumens

The viscosity of road bitumen is a rational, physical property which plays an important role in the technological and quality assessment of a binder. On the other hand, it is believed that the viscosity might substitute for the penetration of a bitumen as a classification property in the appropriate standards. Measurement of the bitumen’s viscosity at lower temperatures, e.g. 60°C, creates some problems caused by the non-Newtonian character of the material. This is observed when dealing with hard bitumens and particularly with polymer-modified bitumens (PmBs). This paper presents viscosity measurements of three PmBs with a rotational viscometer. Regression analysis of the results was conducted according to the four-parameter Cross model, which enabled calculation of the absolute viscosity (or zero shear-rate viscosity). The computed flow curves according to the Cross model were compared with those according to the power-law model frequently applied for road bitumens. The calculated absolute viscosity values together with the conventional test results were applied to the Heukelom bitumen test data chart.     

基于随动测量系统的步进电机跟踪精度研究

利用ARM控制系统实现齿轮测量仪的两轴随动控制,完成齿轮螺旋线高精度测量.根据步进电机脉冲信号和步距角的线性关系,采用ARM系统输出频率脉冲控制步进电机,由于步进电机只有周期误差而无累积误差,系统能够实现齿轮螺旋线偏差快速、准确测量.与现有系统比较,本系统具有控制精度高、测量速度快、误差精度高的特点,能够实时、动态显示测量误差.     

淀粉－丙烯酰胺接枝共聚物增稠能力的研究

以硝酸铈铵为引发剂，分别合成了可溶性淀粉、玉米淀粉及氧化淀粉与丙烯酰胺的接枝共聚物，并经碱性水解制备了相应的阴离子型衍生物。用旋转粘度计研究了这些接枝共聚物水溶液的剪切稳定性，对盐的敏感性和温度稳定性，并与非接枝聚丙烯酰胺（ＰＡＭ）比较。结果表明，同玉米淀粉和氧化淀粉相比，可溶性淀粉与丙烯酰胺接枝共聚的接枝ＰＡＭ链分子量较高；接枝共聚物水解度为５０％左右时水溶液的粘反最大；比之非接枝ＰＡＭ，接枝共聚物水溶液的粘度具有较好的温度稳定性。此外还对接枝共聚物水溶液的剪切稳定性和耐盐性也作了评价。     

Developing unified rheological curves for polymermodified asphalts-part II. Experimental verification

The theoretical analysis in Part I of the paper has shown that unified curves can be obtained, in principle, if the rheological data obtained by measurements on the dynamic shear rheometer (DSR) are normalized through the use of the material's volumetric-flow rate (MVR) generated from a simple flow measurement device (FMD). In Part II of the paper, experimental verification of the unification process is done through systematic data analysis on selected polymer-modified asphalts. The unified curves have far-reaching implications and these have been brought out explicitly. Since MVR is so simple to determine quite accurately on a relatively inexpensive, easy-to-use flow measurement device (FMD), this parameter can be generated on paving sites or at refineries. The MVR can be used as a quality control/quality assurance parameter to ensure batch-to-batch invariance and also as an excellent indicator of the fundamental rheological parameters through the use of the unified curves.     

Hydraulic transport of solids in pipes: a simple method for the prediction of pressure drop

Suspensions such as grouting slurries, concrete and dredge muds exhibit a complex flow behaviour in pipes which is not fully understood. This flow in cement systems is often complicated by the time-dependent behaviour of the material and the apparent slippage at the wall of the pipe. Most of the methods which have been developed to predict the flow behaviour of thick suspensions are very complex and are frequently inaccurate. In this paper a simple method is discussed which can be used to predict the pressure drop in pipes for time-dependent or time-independent materials with a yield stress. The method is based on the assumption that the sheared layer in the pipe can be simulated by a similar layer in the coasial cylinder viscometer, and the properties of the layer are only dependent on plug speed in both systems. The implication of this assumption is that the shear stresses at the surface of the pipe and at the surface of the inner cylinder of the coaxial viscometer are independent of the pipe diameter and the diameter of the cylinders. The method was tested against the authors’ own data and by other data from the literature.