Microstructure of Selected Binary Food Powder Mixtures

Binary mixtures of sugar, citric acid, malic acid, soy protein and starch, after exposure to various relative humidities, were analyzed by Scanning Electron Microscopy (SEM). It is shown that depending on interparticle surfaceaffinity, concentration and relative humidity, the mixtures could be random, partially random, ordered or partially ordered. The type of bridging, between the aggregated particles depended on their chemical species and the availability of surface moisture.     

Development of a simple low-cost solar simulator for indoor collector testing

Indoor test methods for solar collectors are widely accepted and recommended by ASHRAE. The development of a solar simulator for indoor testing and the certification procedure for photo-thermal solar devices is discussed in this paper. The system consists of 14 quartz halogen lamps and provides a testing area of about 1 × 1 m. The irradiance can be varied from 400 to 1500 W/m². This is achieved by varying the input power supplied to individual lamps. The radiation output characteristics of a single lamp have been studied. The distribution of intensity over the covered area of 1·20 × 1·20 m has been recorded using a precision Eppley pyranometer.A variety of collectors—evacuated tubular collectors and flat-plate collectors of both liquid and air heating types—has been tested under sufficiently stable insolation conditions. Results for a conventional solar air heater are presented together with suggestions for further improvements.     

Oxygen consumption by portal-drained viscera of cattle: comparison of analytical methods and relationship to whole body oxygen consumption

Two experiments were conducted to compare methods of determining oxygen consumption by portal-drained viscera and to relate this consumption to total oxygen consumption by lactating dairy cows. Oxygen consumption was the product of portal blood flow (determined by dilution of dye infused into a mesenteric vein) and portal-arterial concentration differences of oxygen. In Experiment 1, portal-arterial concentrations of oxygen were determined in samples from three cows using equations based on blood pH, hemoglobin, partial pressure of carbon dioxide, and partial pressure of oxygen (method 1) or by direct oxygen determination with an oximeter (method 2). Overall, there were no differences in oxygen concentrations or oxygen consumption by portal-drained viscera between methods. In Experiment 2, oxygen consumption by portal-drained viscera (method 2) and total oxygen consumption were measured in two lactating cows. Oxygen consumption by portal-drained viscera accounted for 18% of total oxygen consumption.     

Solar pond ground heat loss to a moving water table

An analytical solution is presented that calculates the heat loss from the bottom of a solar pond (or any heated object) to a soil that contains a moving water table. The water table is treated as a fluid slab moving as a slug flow in one dimension. Edge effects and horizontal heat conduction are ignored. Both steady-state and time-dependent solutions are presented. Results are presented in terms of an effectiveness ratio—the actual heat flux divided by the steady-state heat flux resulting from a constant temperature heat sink at the depth of the water table. The only water-table parameter that strongly affects the effectiveness is the fluid capacity rate. Thus, for any potential solar pond site, a measurement of the mass flow rate of the water table combined with knowledge of the soil thermal properties will allow a good estimation of the ground heat loss expected over the lifetime of the pond.     

Special finite elements with holes and internal cracks

For the numerical treatment of stress concentration problems in plane elasticity, special finite elements with circular and elliptic holes and internal cracks have been developed. Two different variational formulations have been used to construct elements, which may be combined with conventional displacement elements. Using complex functions and conformal mapping techniques the systematic construction of trial functions is shown which not only satisfy a priori the governing differential equations but also the boundary conditions on such influential boundary portions as hole or crack surfaces. For the evaluation of the stiffness matrices of the special elements, only boundary integral computations arc necessary. The numerical results of various examples are very accurate for both functionals.     

On plastic potentials for anisotropic metals and their derivation from the texture function

Summary Plastic yielding of anisotropic metals can be either described by a macroscopic constitutive relation or assessed by means of a model which correlates single and polycrystal behaviors. The mathematical identification of the plastic work rate derived from the two approaches, for all strain rate tensors, leads to a fit of the polycrystal yield surface by an analytical function. When a quadratic from is assumed, the macroscopic anisotropy parameters become explicit functions of the texture coefficients. This identification method is applied to calculate yield surfaces andR-values of rolled and annealed steel sheets: theR-values and in general the flow rule, are more significantly modified by the fitting than the yield surface. Thus, it is worth extending the method to more general constitutive relations which may be given by the form of their work function: alternative forms of the work function for plastic materials are explored, especially in the bearing of convexity and homogeneity where quadratic forms have a distinct advantage. Finally, it is shown that the identification of the work function allows to express the phenomenological coefficients as analytical functions of the texture parameters for many forms of the work function; in the other cases, these coefficients may be obtained by linear or non-linear regression.     

Analysis of the high-frequency spectrum of acoustic emission signals and its relationship to the wear resistance of filled polytetrafluoroethylene

We have performed tribotechnical tests of carbonaceous filled polytetrafluoroethylene in a wide range of loads with the recording of acoustic emission signals. Based on a spectral analysis of the sequence of rms deviations of acoustic emission signals using a discrete Fourier transform, we have constructed a normalized energy spectrum. We show that the mass wear of the material can be determined from the power of the high-frequency component of the spectrum obtained.     

An enhanced zone 3 algorithm of a distance relay using transient components and state diagram

Zone 3 of a distance relay is used to provide the remote backup protection in case of the failure of the primary protection. However, the risk of maloperation under stressed conditions such as heavy loading, voltage, and transient instability is quite high. Zone 3 is used in combination with the derivatives of the voltage and current, etc. to prevent maloperation. At times, the impedance characteristics that restrict the tripping area of relay are used to avoid maloperation due to load encroachment. This work presents a novel zone 3 scheme based on combining the steady-state components (i.e., 60 Hz) and the transient components (TCs) using a state diagram that visualizes the sequence of studies that emanate from the sequence of events. The simulation results show that the novel zone 3 distance relay elements using the proposed method operate correctly for the various events.     

Leakage of Anthocyanins from Skin of Thawed, Frozen Highbush Blueberries (Vaccinium corymbosum L.)

Factors affecting the tendency of thawed blueberries to leak pigmented exudate were investigated. Drip and anthocyanin leakage rates (ALR) were determined spectrophotometrically. Leakage vs time curves were linear or two-phase linear, ALR varying with cultivar, ripeness, and berry condition. Dewaxing increased ALR with most cultivars. ALR did not correlate with berry anthocyanin content, surface area, or cuticle thickness. ALR and amount of drip were poorly correlated. ALR varied from berry-to-berry within samples. Leakage was observed to be nonuniform on berry surfaces, appearing at skin cracks and ruptures, the calyx area, and other point sources. An hypothesis relating leakage to skin condition, fluid accumulation, and anthocyanin content is presented.