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The influence of solder paste viscosity on the porosity and mechanical properties of surface joints was investigated. X-ray radiography showed that solder joints have greater porosity area fraction for higher solder paste viscosity. Solder paste with lower viscosity range was found to have larger evaporation rate of organics than those with higher viscosity range. A solder paste with higher organics content should be employed to obtain a reliable, high shear strength solder joint.

This article describes the radical copolymerization of styrene (St) and n-butylmethacrylate (BMA) in a counter-rotating twin-screw extruder. In order to investigate the effect of the polymer melt viscosity on the working domain in reactive extrusion, the copolymer was crosslinked with different amounts of divinylbenzene (DVB). Crosslinking of the polymer resulted in a higher polymer melt viscosity. It was demonstrated that not only the product properties but also the process characteristics were strongly influenced by the addition of divinylbenzene to the reaction mixture. The product properties changed as expected: more crosslink agent led to a higher molecular weight or an increase in gel fraction, and a much higher melt viscosity of the polymer. Besides these effects on the product properties, the addition of DVB resulted in a more stable process, leading to an enlarged working domain., INTRODUCTION The copolymerization of styrene with several derivatives of acrylates, especially methylacrylate, methyl-methacrylate, and butylmethacrylate have been studied thoroughly. The importance of the latter copolymerization stems from the fact that [...]

Poly(urethane/isocyanurate) is a major resin used in the structural reaction injection molding (SRIM) process. In this study, the kinetics and viscosity changes of a poly(urethane/isocyanurate) resin were investigated by the adiabatic temperature/viscosity rise method and differential scanning calorimetry. The effect of the catalyst concentration and the volume ratio of isocyanate to polyol was investigated. It is found that isocyanate trimerization depends on the diffusion effect resulted from the urethane formation. A kinetic model including the diffusion effect is developed, which is able to predict the experimental results. The reaction induced viscosity rise depends on the concentration and the molecular weight of the formed polymer. The measured adiabatic viscosity rise correlates well with the calculated molecular weight growth using the recursive method., INTRODUCTION Analysis of the structural reaction injection molding (SRIM) process necessitates a thorough understanding of the reaction kinetics and rheological changes of the reacting resin. A knowledge of the reaction [...]

Numerical calculations based on Shaing's L-H transition theory in stellarators and performed by Dahi et al. determine viscosity as a function of ion flow speed in the interchangeable module stellarator (IMS). The calculations predict local maximums in viscosity at flows corresponding to Mach numbers -2 and -10, but not elsewhere. The local peaks manifest themselves as jumps in flow speed, and as regions of high radial electric field ([E.sub.r]) shear. By inducting flows swept between Mach numbers [+ or -]5, an electron injection biasing probe revealed a jump at -2, but none at +2, in agreement with the numerical results. A series of flow profiles at constant bias confirmed this result. Altogether, these data agree well with the numerical calculations and provide support for Shaing's L-H transition model as applied to stellarators.

Experiments were conducted using pairs of particles inside a hot stage microscopy setup with the ultimate objective to study the coalescence, which is a crucial stage in the rotational molding process. It was found that the geometry of the particles had no significant effect on the sintering rate. The sintering rate increases as the viscosity of the resin decreases. However, this effect became less important as the particle size decreased. The experimental results of this study have been compared with the available mathematical models based on balance of viscous and surface tension forces. The model developed by Frenkel and a corrected version by Eshelby predict a faster coalescence than observed experimentally. However, Hopper's model is in relatively good agreement with the present experimental data. Yet there is evidence that mechanisms other than Newtonian viscous flow may play a role in polymer sintering., INTRODUCTION Rotational molding is used to produce hollow plastic parts. Various aspects of the rotational molding process have been presented by several authors (1-4). Although the process itself is not [...]

Based on measurements of the dynamic viscosity, a strategy is proposed to find an expression that relates the viscosity of an epoxy compound during curing, to the temperature, shear rate, and degree of reaction. It appeared that the dynamic viscosity is a unique function of the effective shear rate (i.e. the product of frequency and strain) over a wide range of frequencies and strains after being corrected for the temperature. The effective shear rate dependence of the viscosity is described with a power law with an exponent that depends on the conversion. The effect of temperature is described with an Arrhenius-type equation with conversion dependent parameters. Differential scanning calorimetry is applied to determine the kinetic equation that is used, in combination with the thermal history, to obtain the conversion during the rheological measurements. The description of the viscosity gives a good prediction of the measured viscosity in the region between melting and gelation of the compound. The theories proposed in the literature to detect the gel point from dynamic experiments are examined. It is found that neither the G′-G″ crossover, investigated by e.g. Tung and Dynes (1), nor the frequency-independence of tan(Δ), described by Winter (2, 3), can be used to determine the gel point of the given material. In contrast, the curves of G′ against conversion for measurements performed at equal strain but with different thermal histories appear to converge at a conversion of [approximately]18%, which agrees with the gel point determined through extraction experiments., INTRODUCTION The materials studied are epoxy compounds used for the encapsulation of Integrated Circuits via a transfer molding process. Highly filled epoxy resins satisfy encapsulation requirements and are, therefore, almost [...]

A new constitutive model for the nonlinear behavior of noncrosslinked polymers with infinitesimal strains is derived. It generalizes a model of adaptive links for the viscoelastic behavior of crosslinked polymers. According to the model, a viscoelastic medium is treated as a set of elastic springs that replace each other. The springs model chemical links between polymer molecules, which arise and collapse because of the micro-Brownian motion, a law for replacing the springs determines the stress relaxation in a viscoelastic medium. Unlike crosslinked polymers, noncrosslinked polymers demonstrate steady-state creep flow after some transition period. To describe both the transition process and the steady creep, the model distinguishes two different types of adaptive links. Links of the first type are ruptured under loading, whereas links of the second type replace one another. Both these processes (destruction and replacement) are treated as kinetic, and equations of chemical kinetics are introduced for their description. The nonlinearity of the model arises because of a dependence of rates of kinetic processes on the stress intensity. The constitutive equations derived are testified by comparing theoretical results with data for polypropylene fibers. For the verification we use data presented by three independent sources. The results demonstrate good agreement between experimental observations and their theoretical predictions. Finally, the effect of molecular weight of polymers on parameters of the model is studied., 1. INTRODUCTION In the past three decades a number of publications have dealt with the viscoelastic behavior of polymers and plastics. The main attention was focused on non-linear stress-strain relations, [...]

An experimental study of the blow molding of talc-polyethylene and talc-polypropylene compounds is presented. These compounds are found not to exhibit zero shear viscosity but rather yield stresses, below which there is no flow. The annular swell of the compositions is greatly reduced compared to the neat thermoplastics, but extrusion sag is minimized. Blow molded bottles of talc-thermoplastic compounds were found to have much greater thickness uniformity than blow molded neat polyolefins. The talc particles were determined, by X-ray diffraction, to be oriented with the flake surfaces parallel to the mold surface or equivalently to the bottle surface., INTRODUCTION Thermoplastics highly loaded with talc and similar articles play an important role in modern industry. Talc particles are naturally occurring materials consisting of alternating layers of 2-dimensional silicate polymers [...]

The shear viscosity of poly(vinylchloride) (PVC) at 200 ° C can be decreased by at least one order of magnitude by the addition of as little as 5 wt% poly n-alkyl(meth)acrylates (PMA) of a much lower dynamic viscosity than PVC. For this effect to be observed, the polymeric additive must be immiscible with PVC at 200 ° C. The average size of the dispersed phases is observed in the range of 0.5 to 5 [µmeter]; size fluctuation in this domain has no significant effect. When these conditions are met, there is a linear increase in the shear viscosity ratio [[Eta].sub.blend]/[[Eta].sub.PVC] from 0.2 to 1.0 with increasing logarithmic values of the dynamic viscosity ratio of the additive over PVC [[Mathematical Expression Omitted] from -4 to -1]., INTRODUCTION Poly(vinylchloride) (PVC) is known as one of the most important thermoplastics, because of its low cost and its great versatility resulting from the modifying agents used: plasticizers, fillers, stabilizers, [...]

Many low viscosity, immiscible fluids are difficult to incorporate into polymer matrices because of thermodynamic immiscibility and a large mismatch of melt viscosities. In this investigation, a model system was used to determine the mechanisms and kinetics of mixing in such formulations. The model systems consisted of a series of different molecular weight polyethylenes in polystyrene. The viscosity ratio, [Eta](polyethylene)/[Eta](polystyrene), at 180 ° C and 100 [s.sup.-1] was varied from 0.7 to 0.003. Phase inversion was observed during the compounding of these formulations. The phase inversion was associated with a transition from low to high mixing torque during compounding. This change was primarily due to an increase in the blend viscosity caused by the morphological transformation. The melting behavior during compounding depended on the melt viscosity of the polyethylene. A critical viscosity ratio of ≅ 0.1 exists below which softening of the polystyrene, and thus mixing of the two components, was greatly retarded. Even at very low concentrations, low viscosity polyethylene can have a significant effect on the processing behavior. Effects of mixer set temperature, degree of fill, and polyethylene particle size were explored. The roles of thermal conduction and mechanical energy input were evaluated in the melting regime of the process., INTRODUCTION A wide variety of polymer formulations involve the incorporation of low viscosity, immiscible additives. Lubricants, processing aids, and mold release agents are added to a large number of formulations. [...]

The viscosity of process whey protein (PWP) increases and gelation occurs on adding sodium chloride (NaCl) and incubating PWP at room temperature or temperatures < 25 degrees celsius (C). The gelation is caused by the NaCl-induced aggregation of PWP molecules below 25 degrees C. Heating accelerates gelation but is not absolutely necessary. Viscosity is independent of shear rate. The viscosity increases rapidly with an increase in NaCl concentration.

A viscosity test was carried out on peroxynitrite to determine the validity of the free radical theory that the rate of unimolecular decomposition is slower in high-viscosity solvents. The biological oxidant, which is a product of superoxide and nitric oxide, was not found to undergo single-bond homolysis to form free radical formation as the rate of rearrangements were not affected by changes in viscosity.

Seven sulfonated polystyrene standards (18 000-3 000 000 g/mol), taken as model substances for macromolecular polyelectrolytes, were dissolved in aqueous 0.1 M sodium nitrate solution and characterized by multiangle laser light scattering coupled on-line to flow field-flow fractionation. The distributions of molar mass and root mean square radius and the diffusion coefficients were obtained for each sample using a constant field of force for separation. Relationships between molar mass and root mean square radius [[[.sub.z].sup.0.5] = (2.71 x [10.sup.-2])[[M.sub.w].sup.0.56]] or diffusion coefficient [D = (7.10 x [10.sup.-8])[[M.sub.w].sup.-0.68]] were calculated. To investigate the static analytical range of this novel hyphenated technique a mixture of all seven samples was fractionated applying a programmed field. The relationship obtained between root mean square radius and molar mass was used to calculate a Mark-Houwink equation [[[Eta]]calcd = (2.99 x [10.sup.-2])[[M.sub.w].sup.0.68]]. To verify this result, the intrinsic viscosities for all samples were measured at low shear rate and found to be in good agreement [[[Eta]]calcd = (2.77 x [10.sup.-2])[[M.sub.w].sup.0.67]].

The onset and extent of tetrachloroethylene (PCE) mobilization in four size fractions of Ottawa sand during surfactant flushing is examined through column experiments. The interfacial tension between residual PCE and the aqueous phase was lowered to 0.09 dyn/cm. from 47.8 dyn/cm. by flushing with different surfactant solutions to induce mobilization. A total trapping number that incorporates both viscous and buoyancy forces is used to express PCE desaturation curves. Findings indicate the potential input of buoyancy forces to PCE mobilization. They also offer a novel technique for predicting nonaqueous phase liquid displacement during surfactant flushing.

Transferrin-mediated endocytosis in two variant cell lines indicated similar relationships between internalization rate and extracellular viscosity. Local membrane motion can be catalyzed by spontaneous membrane complex formation. The nucleation stage of receptor-mediated endocytosis (RME) is a vital step in the whole RME process. Membrane tension and cellular viscosity variables are observed as control factors for internalization.

It is well established that at low Rossby and Froude numbers modes possessing potential vorticity behave differently from gravity-inertial wave modes. Wave energy cascades relatively more efficiently downscale to the dissipation, resulting in a geostrophic adjustment. For this reason, it has been suggested that wave energy be subjected to relatively stronger dissipation via 'divergence damping.' This study reports separate measurements of the effective eddy damping acting on wave and rotational modes in simulations of nonhydrostatic Boussinesq flow. The method employs an arbitrary cutoff wavenumber, [k.sub.c], within the simulation's range of resolved scales, in order to calculate explicitly the effect of the smaller-scale motion on wavenumbers below [k.sub.c]. It is found that the rotational-mode eddy viscosity resembles that found in studies of 2D turbulence, with a significant negative range, while it is positive at all wavenumbers for the wave modes.

Experiments on coated films of waterborne coatings (WBC) under controlled conditions (i.e., 25 ° C, 65% RH) were carried out to study the mechanism of leveling. Data in a companion paper imply that the development of the surface tension gradients plays an important role in promoting leveling. The stress due to surface tension gradients is found to be much greater than the stress introduced by hydrostatic pressure gradients in the film caused by surface tension and the free boundary curvature of the film. This reconfirms that the use of a co-solvent, which evaporates faster than water, greatly accelerates the leveling of a WBC., INTRODUCTION It is important to obtain coatings with a smooth surface for appearance and for the inherent performance properties of the coating film. The quality requirements for the leveling in [...]

The influence of film thickness on the leveling of a thermosetting waterborne coating (WBC) was examined. The theory of Patton has been revised to give the proper force balance and modified to include the changes in surface tension and viscosity during leveling by the evaporation of volatile components. However, the predicted leveling process by a numerical method did not coincide with the observed results. Thus, the driving force in the theory, the hydrostatic pressure gradient in the film, was considered to be insufficient to describe the leveling process of the WBC. The hydrostatic pressure gradient can be a component of the driving force to promote leveling, but the existence of an additional component is suggested., INTRODUCTION Coyle (1) showed that it is impossible to control the formation of surface ripples, called ribs, during the application process by the modification of the rheological properties of the [...]

The variants of preconditioned biconjugate gradient methods used in the compressible Navier-Stokes solver with the k-epsilon two-equation model for transonic separated flows shows that a fast convergence rate can be attained by the preconditioned variants and the residuals can be further decreased as the iterations are continued. This indicates that the computation of the turbulent flow with a two-equation model is possible within a reasonable computer time and with high accuracy.

A modified acetone process for the preparation of aqueous polyurethane (PU) dispersion is investigated. PU dispersions were prepared by polyaddition of isophorone diisocyanate (IPDI) to poly(tetramethylene ether glycol) (PTMG) and dimethylolpropionic acid (DMPA), followed by neutralization of pendant COOH groups with triethylamine (TEA). The resulting prepolymer chain was then extended through reaction with an ethylenediamine (EDA) derivative bearing sulfonate groups. The effect of such preparation conditions as catalyst (dibutyltin dilaurate, DBTDL) concentration, the acetone/PU ratio, phase-inversion temperature, agitation rate, and water-addition rate on the average particle size of aqueous PU anionomer dispersions is systematically studied using fractional factorial design and response surface methodology. Fractional factorial analysis indicates that the effects of the acetone/pu ratio, phase-inversion temperature, water-addition rate as well as the two factor interactions of DBTDL concentration and phase-inversion temperature, of the acetone/pu ratio and phase-inversion temperature, and of acetone/PU ratio and agitation rate are the key variables influencing average particle size of PU dispersions. Empirical models for average particle size are fitted and plotted using central composite experimental design as contour diagrams in order to facilitate examination of the average particle size results. The results show that for a 100 g PU anionomer containing 0.311 wt % COOH and 1.51 wt % [SO.sub.3]H groups, a minimum number-average particle size of the dispersion ~ 25 nm can be obtained under an acetone/PU ratio, water-addition rate, phase-inversion temperature, catalyst concentration, and agitation rate of 3.65, 2 mL/min, 50°C ppm and 350 rpm, respectively., INTRODUCTION A queous polyurethane (PU) dispersions have received considerable attention in the past few decades due to their successful applications in coatings and adhesives (1, 2). An aqueous PU dispersion [...]

Numerical simulations of three-dimensional convection with temperature-dependent Viscosity and viscous heating at realistic Rayleigh numbers for Earth's mantle reveal that, in the strongly time-dependent regime, very intense localized heating takes place along the top portion of descending cold sheets and also at locations where the ascending plume heads impinge at the surface. For a viscosity contrast of 100, these localized heat sources exceed the internal heating due to the radioactive decay of chondritic materials by more than an order of magnitude. The horizontally averaged viscous dissipation is concentrated in the top of the convecting layer and has a magnitude comparable with that of radioactive heating., Viscous dissipation is an irreversible process accompanying fluid motion and has generally been studied in the high Mach number regimes. However, even at the low speeds of fluid motion in [...]

ABSTRACT. In this short paper, we consider the possibility of transporting the biomass material by pipeline as slurry. We assume the suspension can be modeled as a non-homogenous viscous fluid [...]

In this work we present an experimental study of shear and apparent elongational behavior of linear low-density (LLDPE) and low-density (LDPE) polyethylene blends by means of capillary rheometry. The characterization of these rheological properties is crucial in the design of a blend that combines the ease of processing of LDPE with the mechanical advantages of the LLDPE. Two different low-density polyethylenes and one common linear low-density polyethylene were used to prepare the blends. The results obtained indicate a strong sensitivity of the rheology of the blend to changes in the molecular weight of the LDPE employed. For the higher molecular weight LDPE, the shear viscosity of the blend was essentially equal to that of the LDPE homopolymer up to a concentration of 25% of LLDPE, whereas the apparent extensional viscosity was appreciably lower. For the lower molecular weight LDPE, the same trend was obtained regarding the shear viscosity, but in this case the apparent extensional viscosity of the blend was somewhat higher than that of the LDPE homopolymer., INTRODUCTION Over the last ten years there has been an upsurge of activity in the study of blends that incorporate linear low-density polyethylene (LLDPE). This is due to the remarkable [...]

This study investigated the interrelationship between strength and flow characteristics of general-purpose polystyrene (GPPS) used in injection molding applications. The ease of flow was chosen as a measure of processability and was evaluated using the melt flow rate and capillary rheometer techniques. Of the different strength tests that were examined, flexural and notched tensile strength tests were most effective in differentiating between commercial grades of high and low molecular weight GPPS. While characterizing strength of injection molded specimens, the degree of molecular orientation was taken into consideration. For unplasticized resins, increasing the weight average molecular weight by about 100,000 enhanced the flexural strength by 10%, but also increased the viscosity at low shear rates (10 to 100 [s.sup.-1]). The increase in molecular weight had virtually no effect on viscosity at the highest shear rates (up to 10,000 [s.sup.-1]). Plasticized resins displayed a 6% loss in flexural strength as well as a significant reduction in viscosity (throughout the shear rate range) as compared with the unplasticized resins. As expected, the improvement in strength achieved by increasing molecular weight leads to a simultaneous increase in the viscosity, i.e., a deterioration of processability. In addition, our study indicates that for samples without preferential molecular orientation, narrowing the molecular weight distribution significantly improves the balance of strength and melt flow rate properties., INTRODUCTION General-purpose polystyrene (GPPS) is an amorphous thermoplastic that finds use in compact-disc cases, drinking cups, petri dishes, and numerous other applications (1). The polymer is available in different molecular [...]

Low-density polyethylene (LDPE) and also linear low-density polyethylene (LLDPE) resins can be characterized by the degree of strain hardening and down-gaging during elongation. A new method for the determination of the apparent elongational flow characteristics is presented. In a small scale apparatus, a molten monofilament is stretched under nonisothermal conditions similar to those found in tubular film extrusion. Measurement of resistance to elongational flow and apparent elongational strain rates permit the comparison of the processability of different resins under specified conditions. The effect of melt temperature and extension ratio are examined. The importance of the molecular structure of both LDPE and LLDPE resins on these properties is also outlined., INTRODUCTION In recent years, the use of linear low-density polyethylene (LLDPE) has dominated the production of blown film for packaging. The processability of LLDPE differs greatly from low-density polyethylene (LDPE), [...]

A slit viscometer to measure the viscosity of polymer melts under processing conditions is described. Along the slit a pressure drop is generated by applying a pressure at both the entrance and the exit. In this way the pressure in the center can be controlled independently of the shear rate. The pressure gradient in the slit is measured by means of three pressure transducers which are mounted in the region of fully developed flow. Results of pressure-dependent viscosity measurements on polystyrene, polyacrylonitrile-butadiene-styrene, and polypropylene are presented in a shear rate range of five decades. The flow curves obtained at different pressures and temperatures can be shifted onto a master curve. The shear thinning behavior of the three materials is adequately described with the generalized Cross-Carreau equation, while the zero shear viscosity is modeled with a generalized Arrhenius-W.L.F. relationship, incorporating a pressure dependency. Alternatively, it is possible to describe the zero shear viscosity in terms of the free volume fraction and the temperature., INTRODUCTION Nowadays, the demands on injection-molded products are becoming more and more stringent. Complex products are molded which require a high precision and geometric stability. For the design and processing [...]

A simulation technique for nonisothermal flow analysis of non-Newtonian fluid in a nonintermeshing counter-rotating twin screw extruder was developed by modifying the flow analysis network (FAN) method. The local shear viscosity in the flow field was calculated by an iteration method combing the three types of mean shear rate functions. The modified Cross model and an Arrhenius-type function for temperature dependence were also introduced. Streamlines in the flow field are represented by computing the movements of fluid particles based on the flux fields. The computed residence time from the streamlines led us to solve the energy equation by replacing the coordinate system. The profiles of pressure, shear rate, shear viscosity, temperature, and residence time were simulated. The influence of operating and geometrical parameters on the screw characteristics are discussed. Further, residence time distribution (RTD), strain distribution function (SDF), and interfacial area growth are predicted from the computation of streamlines to analyze the mixing capabilities of the extruder., INTRODUCTION The flow analysis network (FAN) method was originally developed by Tadmor and co-workers (1-2) to apply the analysis of filling a rectangular cavity and design of a crosshead die [...]

A viscoplastic theory is developed that reduces to creep theory analytically under steady-state conditions. A fairly simple model is constructed from this theoretical framework by defining material functions that have close ties to the physics of inelasticity; consequently, the model is characterized easily. The computational characteristics of the model are enhanced, in general, by converting the kinetics equation from a hyperbolic relationship to a power-law relationship. The resulting model is applied to copper and to the copper alloy, NARloy Z.

Parallel sliding load support has been a subject of numerous theoretical and experimental investigations. Postulated mathematical models suffer from restricting assumptions. The present analysis evaluates the several models that have appeared and provides an orderly analysis which elaborates on the mechanism that may be responsible for the fluid generated lifting force. The governing continuity, momentum and energy equations for a Newtonian fluid, which are coupled, via temperature dependent density and viscosity are solved simultaneously using the finite difference method, to yield various bearing characteristics. The results indicate that the consideration for the foreregion pressure together with the density variation, may lead to a useful load support with a reduced friction, even for parallel sliding.

The application of dynamic light scattering to the determination of the dynamic viscosity of transparent liquids is shown by the use of low-power (10-mW) laser sources and a multiple-tau correlator. A novel data evaluation scheme is demonstrated by the application of a nonlinear fit to various intervals of lag times, which can detect relevant systematic errors. An appropriate experimental procedure permits results with good accuracy and precision for selected liquids.

The roles of frequency dispersion, nonlinearity, and laminar viscosity in the evolution of long waves over distances of many wavelengths in constant water depth are investigated with numerical solutions of the Boussinesq equations. Pronounced frequency doubling and trebling is predicted, and the initial evolution to a wave shape with a pitched-forward front face and peaky crests is followed by development of a steep rear face and a nearly symmetric crest/trough profile. While reducing overall energy levels, laminar viscosity acts to prolong cycling of third moments and to inhibit the onset of disordered evolution characteristic of nonlinear, inviscid systems. Preliminary laboratory results show some qualitative similarities to the numerical simulations. However, these laboratory experiments were not suitable for detailed model-data comparisons because dissipation in the flume could not be accounted for with either laminar or quadratic damping models. More carefully controlled experiments are required to assess the importance of viscosity (and the accuracy of the Boussinesq model) in the evolution of nonlinear waves over distances of many wavelengths.

This paper presents a new method to reduce turbulent frictional drag by injecting high-viscosity fluid into the boundary layer. When the turbulent region of the boundary layer is filled with high-viscosity fluid, and the viscosity of the viscous sublayer is kept low, the Reynolds stress in the turbulent region is reduced and therefore requires a greater velocity gradient to transfer the momentum. The greater velocity gradient in the turbulent region results in a reduction of the velocity gradient at the viscous sublayer, which causes a drop in shear stress at the wall. Such a boundary-layer structure could be created by injecting two different fluids from double slits on a wall. Sugar syrup and water were used as the high-viscosity fluid and the low-viscosity fluid, respectively. The shear stress was directly measured by shear stress pick-ups mounted flush on the wall. The shearing stress was reduced by more than 50 percent at the optimum injection condition. A water/water injection experiment was also performed to show the effect of injection itself.

The influence of quantum tunneling on nonthermal viscosity in magnets was investigated. The results showed that there were two magnetic relaxation regimes. At high temperatures, the magnetic viscosity was proportional to temperature. At lower temperatures, the magnetic viscosity was not dependent on the temperature. This independence indicated the quantum tunneling of the magnetization.

Internal friction (IF) was measured for two polymer liquid crystal (PLC) esters, PET/xPHB, where PET is poly(ethylene terephthalate), PHB is p-hydroxybenzoic acid, with the mole fractions x of the PHB in the copolymers 0.5 and 0.6. Pure PET was also studied for comparison. The internal friction parameter Q to the -1 and the square of the output vibration frequency f squared were determined as a function of temperature between -150 degrees C and +400 degrees C for a fixed input frequency. Values of the latter were varied between 0.5 and 30 Hz; all spectra were recorded under vacuum of 0.10 Torr. The IF results are virtually independent of the substrate used, namely silica glass or platinum. Multiple transitions found in each sample agree fairly well with those determined by other methods, including thermally stimulated depolarization. In contrast to other dynamic mechanical methods, a single internal friction vs. temperature run can be used to locate transitions in solid as well as in melt phases.

Tuning a three-dimensional (3-D) coastal circulation model for vertical eddy viscosities can be a laborious task. An efficient alternative is to use adjoint inverse estimation methods, and one such method is developed here. A cost functional that consists of two terms is formulated: The first describes the lack of fit between model results and available data, and the second measures the variance of the eddy viscosity with depth. This latter term has been introduced with a view to eliminate the instabilities commonly associated with inverse methods. Weights are used to vary the relative influence of each term. The 'optimized' eddy viscosity estimate is obtained by a variational minimization of the functional. The procedure is tested using velocity data at the center of a rectangular sea domain. Wind and tidal forcing are considered along with known eddy viscosity profiles. The inverse model retrieves extremely good estimates of the eddy viscosities in all cases, even when data are sparse. The estimates are all smooth, and the method and the solutions exhibit no sign of instability.

A quasi-three-dimensional numerical model composed of two coupled modules has been developed for computing circulations in shallow waters. The depth-averaged flow is computed in one of the modules, and the vertical distribution of the flow velocities is determined in the other. A simple algebraic formulation is assumed for the vertical eddy viscosity. Based on measurements of velocity profiles in a wind-water flume, it was found that the vertical eddy viscosity should be scaled using the larger value of the bed- and surface-friction velocities. For the cases considered, computations using the k-epsilon model supported the results. Secondary currents caused by curvature effects and Coriolis force in open channel flow can be simulated by using the model. The model was also applied to compute circulations in a model harbor basin where measurements of velocities were available. The advective terms in the equations of motion are shown to be important to model the three-dimensional features of these flows.

The effect of whirl frequency and lubricant viscosity on the dynamic pressures and force response of an open end and a partially sealed squeeze film dampers (SFD) with a radial clearance of 0.38 mm is determined experimentally. The experiments are carried out in a damper test rig executing circular centered orbits and for whirl frequencies ranging from 33 to 83 Hz. The experimental results show that the sealed SFD configuration produces larger tangential forces than the open end SFD. The tangential (damping) force increases linearly with increasing whirl frequency. For this radial clearance fluid inertia effects in the damper are found to be negligible since the squeeze film Reynolds number is less than 1.20. Cavitation was observed in both damper configurations at high frequencies and high lubricant viscosities. This condition limited the rate of increment of the damping (tangential) force with increasing frequency and reduced the radial force when lubricant viscosity increased.

A study was conducted to verify if membrane enzymes are controlled by the viscosity of the surrounding lipids. Results showed that n values for bilayers in the liquid-crystalline phase would have to be significantly larger than those for gel phases if a basis for viscosity-dependent regulation of mebrane enzymes is desired. Results also showed that membrane enzymes are easily affected by the viscosity of the aqueous phase.

Magnetic viscosity, thermal relaxation and related thermal noise in Co-based amorphous and soft ferromagnetic alloys at milliKelvin temperatures were investigated using a superconducting quantum interference device magnetometer. The results showed that magnetic viscosity was not dependent on the temperature. In addition, thermal relaxation of the spin subsystem to the heat bath was observed.

An increasing number of polymer alloys made by reactive processing of a compatibilizer precursor (CP) to form the compatibilizer in situ have appeared in recent years. Literature reports on compatibilization studies have focused on interactions of chemistry-morphology, processing-morphology, morphology-rheology, morphology-properties, etc. In commercial alloys, the interaction of chemistry and processing results in a material that has a balance of physical properties and rheological behavior. To maximize the contribution of each phase, it is of interest to be near the phase inversion region. In this work, maleic anhydride functionalized polyethylene is used as an effective CP for polyamide/polyethylene blends. In blends containing 50% nylon 6, the melt viscosity of the alloy increases exponentially as the ratio of CP to polyethylene increases though the morphology remains dispersed polyamide 6. High ratios of CP/PE are desired for toughness, alloys containing lesser amounts of CP exhibit better processability. The balance of toughness and processability is shown to be affected by the molecular weight of the CP.

The effect of a polymer network on the alignment and rotational viscosity of a nematic liquid crystal was investigated. The results showed that the application of a field destroyed the uniform alignment induced by a monodomain network. The mesh size of the network was estimated at one micrometer, smaller than the magnetic field of the solvent. In addition, the diamagnetic anisotropies of the aligned samples were not affected by the polymer.

The solution of thermal elastohydrodynamic lubrication of rolling/sliding line contacts has been obtained. The Newton-Raphson technique was used to solve the simultaneous system of Reynolds and elasticity equations. The energy equation with boundary conditions was solved by the finite-difference method. Two models were developed: one with a constant viscosity across the oil film and another with a variable viscosity across the oil film. Different viscosity formulas such as modified WLF, Roelands, and Barus can be used in these models. Viscosity measurements were also performed over wide ranges of pressure and temperature. A very good fitting of experimentally measured viscosity by modified WLF formula was obtained. The oil film shape and minimum film thickness were calculated for pure rolling and high slip. For high slip and high rolling velocity, a tapered wedge shape of EHL film (in the longitudinal direction) was obtained. These results show a good correlation with measurements reported in other papers. They show that there is a significant influence of temperature on the oil film shape.

To predict the apparent viscosity ratio of gelling ovalbumin, a model for characterizing changes in the viscosity of soy protein was adapted. It was determined that at 85,90 and 95 degrees Centigrade, ovalbumin of 87% purity would form 3,5 and 7% gel respectively. A back-extrusion method helped to determine apparent viscosity ratios during gelation. The maximum apparent viscosity ratio increased with the increase in protein concentrations. The mathematical model was verified after determining apparent viscosity ratios at different temperatures and could be used to predict ovalbumin thermal gelation apparent viscosity ratios.

The standard eddy-viscosity concept postulates that zero velocity gradient is accompanied by zero shear stress. This is not true for many boundary layer flows: wall jets, asymmetric channel flows, countercurrent flows, for example. The generalized eddy-viscosity hypothesis presented in this paper, relaxes this limitation by recognizing the influence of gradients in the turbulent length scale and the shear. With this new eddy-viscosity concept, implemented into the standard k - epsilon model, predictions of some boundary layer flows are made. The modelling results agree well with measurements, where predictions with the standard eddy-viscosity concept are known to fail.

A model for turbulent backflows is presented and evaluated. The model is based on experimental observations, in particular, the wake-like behavior of the turbulence and the diffusion/dissipation energy balance observed in detached flow regions. These lead to an ODE for the eddy viscosity, based on a reduced form of the turbulence kinetic energy equation. This ODE is solvable analytically. The model is applied as a module within a 'host' eddy viscosity model (such as a k - epsilon model) using a three-layer framework wherein the host model predicts the eddy viscosity distribution in the inner and outer layers, while the backflow model provides the eddy viscosity distribution in the inner and outer layers, while the backflow model provides the eddy viscosity field in the middle layer. Predictions of several flow cases, using this approach, are shown.

Dynamic light scattering measurements using a diamond anvil cell were used to investigate the dynamics of fluids. The use of a diamond anvil cell eliminated the need to confine data to moderate pressures. However, the small size of the cell's pressure chamber resulted in a weak scattered intensity. In addition, scattering from the diamon/air and diamond/sample interfaces further complicated analysis of the measurements.

The veracity of predicting the viscosity of a polymer solution passing through porous media using an equation relating permeability and hydraulic conductivity was investigated. Viscosity of the test solutions were measured using two viscometers on several types of soil columns and the results compared with that from the equation. It was discovered that the effective viscosities of the polymer solutions were dependent on the pore size of the media, and the test equation failed to account for the effects of pore size. Actual viscosity readings showed that there was significant overprediction which was affected by the type of soil.