DRAG ON MULTIPLE SPHERE ASSEMBLIES SUSPENDED IN NON-NEWTONIAN TUBE FLOW

The drag forces experienced by single and multiple sphere assemblies suspended in non-Newtonian tube-flow were investigated under different levels of fluid viscosity of aqueous CMC solutions (m=2.0 to 21.1 Pa-sⁿ and n=0.73 to 0.82), flow rate (0.02 to 0.86 kg/s) and particle concentrations (1.53 to 11.01% on a volume basis). It was found that an increase in particle concentration resulted in an increase in drag force experienced by each sphere in an assembly. It was also observed that the presence of identical assemblies upstream and downstream of the single test assembly (multiple assembly case), resulted in drag force increases per sphere from 14% for low concentration to 25% for high concentration. an equation was developed to predict a drag correction factor for Stokes' equation for the multiple assembly configuration based on particle concentration.     

RHEOLOGICAL CHARACTERIZATION of COFFEE MUCILAGE

Rheological behavior of mucilage obtained from two varieties of coffee grown in Colombia (Caturra and Colombia) was studied as a function of ripe cherry content (RCC) and postharvest time (PHT). A Brookfleld HB DV-III viscometer was used in concentric cylinder geometry over a shear rate range of 4.8 to 120 s⁻¹. the power-law model was used to describe the shear stress versus shear rate data, and the consistency index (K) and flow behavior index (n) were determined. the mucilage is a highly viscous and pseudoplastic (n < 0.3) fluid. the K increased and n decreased as the RCC and PHT increased. the mucilage of the Caturra variety was more viscous and shear thinning than that of the Colombia variety. Microstructural examination of the mucilage revealed that certain weak structures as phloem vessels found in the mucilage may be destroyed upon application of shear stress and may contribute to the pseudoplastic nature of the mucilage. Diffusion of tannin from the pulp to mucilage with delay in postharvest processing may be responsible for increased apparent viscosity with increased PHT.     

Polyphosphates as inhibitors of surface mould growth on hard cheese during ripening

A novel treatment using polyphosphates to protect cheeses against superficial mould growth was assayed. The treatments were: control commercial paint with natamycin (I), commercial paint based on polyvinyl–water (II), immersion in a saturated solution of polyphosphate (III), immersion and commercial paint (IV), commercial paint of polyphosphate solutions (V) and immersion and commercial paint of a saturated solution of polyphosphates (VI). The cheeses were ripened for 6 months. Superficial mould growth was inhibited in groups IV and VI when compared to cheeses from the control group (I). Statistical sensory analysis made between cheeses from groups IV and I (control) showed no significant differences.     

Titanium diffusion in shinbone of rats with osseointegrated implants

Dental implants are composed of commercially pure Ti (which is actually an alloy of titanium, and minor or trace components such as aluminium and vanadium). When the implant is inserted, its surface undergoes a number of chemical and mechanical processes, releasing particles of titanium to the medium. The metabolism of free ions of titanium is uncertain; the uptaking processes in the body are not well known, nor their toxic dose. In addition, physical properties of newly formed bone, such as diffusivity and activation energy, are scarce and rarely studied. In this study, we analysed the diffusion of titanium in the titanium‐implanted shinbones of six adult male Wistar rats by spatially resolved micro x‐ray fluorescence. The measurements were carried out at the microfluorescence station of the x‐ray fluorescence (XRF) beamline of the Brazilian synchrotron facility LNLS (from Portuguese ‘Laboratorio Nacional de Luz Sincrotron’). For each sample, XRF spectra were taken by linear scanning in area near the new bone formed around the Ti implant. The scanning line shows a clear effect of titanium diffusion whereas calcium intensity presents a different behaviour. Moreover, a clear correlation among the different structures of bones is observed in the Ti and Ca intensities. The results obtained in these measurements may allow determining quantitatively the parameters of diffusion rates and other physical properties of new bone like diffusion coefficients.     

A NOTE: EFFECTS OF LOGARITHMIC TRANSFORMATIONS OF NONLINEAR GOALS IN THE GOAL PROGRAMMING PROBLEM

This note points out that in the context of goal programming the linearization of nonlinear goals by logarithmic transformations, as it is usually done in the field of mechanical engineering applications, is not in general a valid method and can lead to wrong results.     

AN ALGORITHM TO IDENTIFY ALL PATHS IN SCHEDULING NETWORKS

The purpose of this paper is to present an algorithm that identifies every path in scheduling networks. The algorithm finds the answer by simulating the way we solve the problem by hand. The result is a list, in sequential order, of all activities involved in each path, the algorithm is divided into forward and backward passes that are repeated until all paths have been identified. Backward passes determine the existence of paths, while forward passes determine the activities involved in the paths. The algorithm has been successfully tested with 31 construction networks, and has been implemented in simulation programs used for construction scheduling and probabilistic analyses.     

A REVIEW of PARTICLE BEHAVIOR IN TUBE FLOW: APPLICATIONS to ASEPTIC PROCESSING1

The design of holding tubes for continuous sterilization of foods containing large particulates depends heavily on knowledge of pipe flow behavior of food suspensions. Although directly related literature is limited, a considerable body of potentially useful literature is available on solid-liquid flows. This critical review discusses literature on solid-liquid flow in tubes, including capsule flow, effects on bends, radial migration phenomena, particle-particle interactions, modeling studies and other topics which may have a bearing on particle velocities in holding tubes.     

A STUDY of DRAG FORCES ON SOLID SPHERICAL PARTICLES IN POWER LAW BOUNDED FLOW: APPLICATIONS to ASEPTIC PROCESSING1

Drag forces on rigid spherical particles suspended at specific points in a tube carrying viscous solutions of sodium carboxymethylcellulose (CMC) were measured using a load cell. Polystyrene spheres of diameter 1, 2.22 and 3.175 cm were used in a plexiglass tube of 4.75 cm internal diameter. the range of consistency coefficient of the carrier fluid studied was 5 to 16 Pa-sⁿ. Mass flow rate was varied between 0.01 and 0.9 kg/s. the drag coefficient-generalized particle Reynolds number correlation developed from linear regression was: Cd = 101.35/[(N_Re)p]^0.84/n. This correlation may be used to estimate drag forces on suspended spherical food solids in aseptic holding tubes.