Non-newtonian behavior of suspensions

Summary A theory is derived for the non-Newtonian behavior of a dilute suspension of neutrally buoyant, rigid, spherical inclusions in an incompressible Newtonian fluid. The source of the non-Newtonian effects is shown to be that portion of the kinetic energy associated with the flow perturbation caused by the presence of the particles. Explicit forms are given for the average stress constitutive relation under the restriction of slowly varying flow conditions. Related normal stress effects are considered in some detail for the case of simple shearing flow.

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Nicht Newtonsches Verhalten von Suspensionen

Zusammenfassung Es wird eine Theorie für nicht Newtonsches Verhalten von verdünnten Suspensionen gleichmäßig schwebender, starrer, kugeliger Teilchen in inkompressibler, Newtonscher Flüssigkeit hergeleitet. Es wird gezeigt, daß die Quelle nicht Newtonscher Effekte der Anteil der kinetischen Energie ist, der mit den Störungen in der Strömung zufolge der Anwesenheit der Teilchen verbunden ist. Es werden explizite Ausdrücke für die Stoffgleichungen der mittleren Spannung unter der Einschränkung langsam veränderlicher Strömungsbedingungen angegeben. Einflüsse der bezogenen Normalspannung werden in einigen Einzelheiten für den Fall der einfachen Scherströmung betrachtet.

     

Mathematical simulation of the drying of suspensions and colloidal solutions by their depressurization

The heat and mass transfer in the process of drying of high-humidity materials by their depressurization has been investigated. The results of experimental investigation and mathematical simulation of the indicated process are presented. They allow one to determine the regularities of this process and predict the quality of the finished product. A technological scheme and an engineering procedure for calculating the drying of the liquid base of a soap are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 116–122, May–June, 2006.     

Viscoelastic behavior of electrorheological suspensions

The dependence of viscoelastic properties (modulus of elasticity G and loss modulus G') of electrorheological suspensions on applied electric field is determined experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 4, pp. 605–609, April, 1986.     

Evaluating the bioequivalence of metronidazole tablets and analyzing the effect of in vitro dissolution on in vivo absorption based on PBPK modeling

Abstract

Metronidazole, a BCS class I drug, could be waived based on the BCS principles, thus enabling in vitro dissolution data as a surrogate of BE study. However, the impact of dissolution profiles of metronidazole tablets on the in vivo performance has never been studied systematically. So the aim of the present study was to conduct a multipronged approach of in vitro dissolution, in silico simulation, and in vivo study to evaluate the effect of dissolution performance on oral absorption of metronidazole tablets, as well as the accuracy of PBPK model to predict the oral bioavailability for BCS I drug. The results demonstrated that the PBPK models were successfully established for metronidazole immediate-release tablets. Bioequivalence comparison in dogs indicated that the test products were bioequivalent to the Reference (80%–125%, 90% CI), and even their dissolution profiles in vitro were significantly different. And the prediction of oral pharmacokinetics of the three formulations in human was also highly similar. In addition, the behavior of in vitro dissolution profiles and in vivo absorption was elucidated. These findings will contribute to understanding the potential risks during the formulation development and justifying the biowaiver for metronidazole tablets.     

Evaluating system behavior through Dynamic Master Logic Diagram (DMLD) modeling

In this paper, the Dynamic Master Logic Diagram (DMLD) is introduced for representing full-scale time-dependent behavior and uncertain behavior of complex physical systems. Conceptually, the DMLD allows one to decompose a complex system hierarchically to model and to represent: (1) partial success/failure of the system, (2) full-scale logical, physical and fuzzy connectivity relations, (3) probabilistic, resolutional or linguistic uncertainty, (4) multiple-state system dynamics, and (5) floating threshold and transition effects. To demonstrate the technique, examples of using DMLD to model, to diagnose and to control dynamic behavior of a system are presented. A DMLD-based expert system building tool, called Dynamic Reliability Expert System (DREXs), is introduced to automate the DMLD modeling process.     

Dynamic modeling of the sedimentation of concentrated bidispersed suspensions

A model based on the principle of continuity and the assumption that sedimentation results in a stratification of particles was proposed to describe the sedimentation of concentrated bidispersed suspensions. Using the slip velocity correlation of Fessas and Weiland (1984) the predicted movement of the settling interfaces was in good agreement with experiments. The model also predicted increases in concentrations of the monodispersed suspensions formed from the settling of suspensions consisting of heavy and buoyant particles when sedimentation was enhanced by the convective fingering effect.     

Effects of barium dissolution on dispersing aqueous barium titanate suspensions

Dissolution of barium ion and its effect on dispersion behavior of aqueous barium titanate suspensions at various pH values have been investigated. The amount of leached barium ion decreases with increasing pH value. The dissolution of barium ion also causes an increase in pH value of suspension, but the change decreases with increasing initial pH value. The iso-electric point (IEP) of leached barium titanate powder increases with increasing leaching pH value and solid loading as well. The dissolution of barium ion enhances the colloidal stability of aqueous barium titanate suspension, in agreement with zeta potential measurement.     

Multi scale modeling and simulation for oxygen precipitate behavior in silicon wafer

Oxygen precipitates in semiconductor device are generally considered beneficial for its metallic contaminants gettering function, but the oxygen precipitates also affect to degrade the efficiency of solar cell. The formation of oxygen precipitates is closely related to the grown-in defects like oxygen in crystal growth process and heat treatment cycle in device process. Oxygen comes into the silicon melt by dissolving quartz (SiO2) crucible and incorporates into the silicon crystal in Czochralski process. The oxygen plays key role in the formation of oxygen precipitate nuclei in crystal growth process and then the nuclei grow up to be oxygen precipitates in device process. Therefore, the formation of oxygen precipitates is closely related to the crystal growing process and device manufacturing process. In this research, we interpreted the formation and behavior of oxygen precipitates depending on varying oxygen concentrations by using Multi_Scale method. The method is very useful to obtain more reliable interpretation result than other single methods. The validity of this research is verified by comparing with experimental data.     

反渗透海水淡化能量回收装置中盐水和海水混合过程研究

正位移式能量回收装置利用盐水直接增压进料海水实现反渗透淡化系统余压能回收利用的同时,不可避免会产生盐水和进料海水间的混合．混合使得被增压海水的盐浓度升高,从而导致反渗透系统工作压力及淡化水盐浓度的增加．本文建立了能量回收装置水压缸中盐水和进料海水混合过程的数学模型,利用流体力学模拟软件对水压缸中混合段的形成、混合机理及混合段用作液柱活塞的条件等进行了研究,分析了液柱活塞的局限性和采用实体活塞的重要作用．     

Viscoelastic and rheological behavior of concentrated colloidal suspensions

Molecular approaches are discussed to the density (), viscoeleastic (), and rheological () behavior of the viscosity(,,) of concentrated colloidal suspensions with 0.3 < < 0.6, where, is the volume fraction, the applied frequency, and ; the shear rate. These theories are based on the calculation of the pair distribution functionP ₂(r,,), wherer is the relative position of a pair of colloidal particles. The linear viscoelastic behavior(,,=0) follows from an equation forP ₂(r,,) derived from the Smoluchowski equation for small, generalized to large by introducing the spatial ordering and (cage) diffusion typical for concentrated suspensions. The rheological behavior(,,=0) follows from an equation forP ₂(r,) of a dense hard-sphere fluid derived from the Liouville equation. This leads to a hard-sphere viscosity^hs(,) which yields the colloidal one(,) by the scaling relation(,) ₀=^hs(,) _B, where ₀ is the solvent viscosity. _B is the dilute hard-sphere (Boltzmann ) viscosity and the's are appropriately scaled,(,) and(,) agree well with experiment. A unified theore for(,,) is clearly needed and pursued.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994. Boulder, Colorado, U.S.A.     

Interconverting conformations of variants of the human amyloidogenic protein beta2-microglobulin quantitatively characterized by dynamic capillary electrophoresis and computer simulation

Capillary electrophoretic separation profiles of cleaved variants of beta2-microglobulin (beta2m) reflect the conformational equilibria existing in solutions of these proteins. The characterization of these equilibria is of interest since beta2m is responsible for amyloid formation in dialysis-related amyloidosis and thus is able to attain alternative conformations that lead to irreversible aggregation and precipitation. In this study, we quantitate the increased conformational instability of cleaved beta2m by extracting rate constants and activation energies by simulating the experimental data using a unified theory for dynamic chromatography and dynamic electrophoresis. The results are correlated with the outcome of independent experiments based on mass spectrometric measurement of H/D exchange. This study illustrates that dynamic capillary electrophoresis is suitable for the investigation of the interconversion of protein conformations of amyloidogenic molecules and is not only restricted to ideal model compounds.     

A modified meshless local Petrov–Galerkin method to elasticity problems in computer modeling and simulation

A modified meshless local Petrov–Galerkin (MLPG) method is presented for elasticity problems using the moving least squares (MLS) approximation. It is a truly meshless method because it does not need a mesh for the interpolation of the solution variables or for the integration of the energy. In this paper, a simple Heaviside test function is chosen to overcome the computationally expensive problems in the MLPG method. Essential boundary conditions are imposed by using a direct interpolation method based on the MLPG method establishes equations node by node. Numerical results in several examples show that the present method yielded very accurate solutions. And the sensitivity of the method to several parameters is also studied in this paper.     

Mathematical simulation of the process of fine cleaning of suspensions

A mathematical model is considered of the process of interaction of filtrate within a pipe with a two-phase disperse mixture in the porous wall and outside of the pipe. The results of numerical solution of conjugate problem of heat and mass transfer demonstrate the advisability of preheating the substrate of a tubular filter for producing filtrate.     

Compressive behavior of tailor-made metallic foams (TMFs): Numerical simulation and statistical modeling

In this work, the compressive behavior of tailor-made metallic foams (TMFs) was qualified and quantified under quasi-static compressive loading. Response surface methodology (RSM) based on a central composite design (CCD) was successfully employed for development quadratic polynomial regression models between the response variables (structural stiffness, yield and compressive strength) in terms of three variables (cell size, cell wall thickness and height of cell layers). These models were then used for finite element simulation of TMFs under compression conditions by considering a representative unit cell. There was an adequate agreement between the simulation data and the experimental measurements within 3.5% confidence interval. The analysis of the statistically developed models revealed that ratio of wall thickness to the size of cell (t/D) has the most significant influence on the compressive behavior of TMFs.     

Investigation of deformation and failure of the laminated composite Cr-V by the method of computer modeling

The article presents a further development of the mathematical method [N. V. Shadchina et al., Probl. Prochn., No. 2, 88–91 (1990)] that makes it possible to model the processes of deformation and failure of composite materials on a personal computer. The strength characteristics of laminated materials Cr-V are calculated on the basis of the physicomechanical and structural properties and with a view to their statistical scatter and the properties of the interlay er forming during the production of the composite. It was established that when the layers are thinner, the dependences of ultimate strength and yield strength of the composite material on the mean thickness of the layers are transformed into dependences Petch—Hall-type.Translated from Problemy Prochnosti, No. 2, pp. 47–54, February, 1996.