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SUMMARY An experimental study of the equilibrium vapor pressure of frozen bovine muscle is presented for a temperature range of −23°C to −1°C. Measurements are presented for round, sirloin, and T‐bone steak. The results show that the equilibrium vapor pressure of beef is approximately 20% lower than the vapor pressure of pure ice at the same temperature. An interpretation of the experiments attributes the vapor‐pressure depression to dissolved solute species in the frozen liquid phase of the beef muscle. To determine the role of the solid meat matrix in the vapor‐pressure depression, experimental measurements are also presented for the vapor pressure of the frozen liquid phase, which can be mechanically removed from the meat by squeezing at room temperature. The vapor pressure of this phase at a given temperature lies between that of beef muscle and pure ice. This result is interpreted by the use of a simple model which idealizes the beef muscle as a cross‐linked ionic network which contains not only soluble and mobile ionic species but also ions and other hydrophilic groups which are permanently attached to the network. Because of the presence of these permanently attached groups, more solute particles are present in the frozen liquid phase when it is incorporated in the meat matrix than when it is removed. Since the magnitude of the vapor‐pressure depression increases with the concentration of dissolved solute species, the depression is greater when the meat matrix is present. These ideas are consistent with the observed temperature coefficient of the vapor pressure, which is larger for frozen beef muscle than for the separate frozen liquid phase.

ReSeDA (Remote sensing data assimiliation) is an international project jointly funded by the EU and France which ran 1997-2000. It involved field experiments just south of Avignon. Cranfield staff participated by using a small remotely-piloted aircraft to make near-surface measurements of atmospheric temperture and humidity above field boundaries to study the influence of surface properties on the surface layer of the atmosphere.

A general numerical-analysis procedure is presented for the screw extrusion of a non-Newtonion material. The full Navier-Stokes energy and continuity equations are used in the numerical procedure. The flow is taken as steady and incompressible, and the viscosity is written according to the Ostwald-de Waele model in which the viscosity is assumed to be inversely proportional to the square root of the second invariant of the rate of deformation tensor and exponentially dependent on the temperature. The procedure allows the prediction of vorticity, stream-function, swirl velocity, internal energy, and viscosity over any cross section of a groove containing plastic. Calculations for the mass extrusion rate and power consumption (shear rate) for the screw extruder are also given. Typical cases are considered for which all the quantities listed above are determined. The results compare favorably with other theoretical work.Past consideration of melt processing of thermoplastics is focused to a great extent on the prediction of the relationship between stress and rate of strain (equation of state) applying to a given material. Nontrivial solutions must be developed which utilize such equations of state to assess the merits of any proposed equation of state. The best representation for an equation of state can only be found by comparin the results of its use in a comprehensive solution wit a the experimental data. Obviously it is desirable to employ the most comprehensive solution possible consistent with an acceptable amount of computing expense. The comprehensive solution can also be used to check the accuracy of simpler solutions which can be effected with a minimum of computing time.The present discussion is restricted to the most important example of melt processing, namely, the single-screw extruder which is diagramatically shown in Figure 1. The barrel is driven by a motor while the screw is held fixed. Generally, solid polymer is fed at a constant rate into the feed section from the hopper. The screw forces the material into the compression section where viscous shear causes the material to melt. The molten polymer is then pumped through the metering section and finally through a die or orifice to form the desired product shape. The usual screw extruder operates with a constant height of material in the hopper so that the extrusion rate is controlled chiefly by the pumping action of the metering section. Under these conditions, a steady, stable operation is achieved.The objective of this paper is to obtain a comprehensive solution for the pumping phenomena in the metering zone of a single-screw extruder. The paper is not concerned with the design of extrusion apparati or with determining equations of state for polymers; rather it is desired to develop a solution scheme which is capable of accounting for all the phenomena occurring in the metering zone. A comprehensive solution of this type has not been reported in previous literature. As indicated earlier, this solution can be used to check the validity of equati...

We present a numerical solution for the operating conditions of a hydrodynamic porous journal bearing. The numerical method allows for the possibility of variable porosity in the bearing matrix, but the solution has been achieved on the assumption of matrix homogeneity. The relation between the various bearing parameters have been shown for a variety of bearing geometries and permeabilities enabling the operating conditions for this type of bearing to be better appreciated. A comparison of the present solution with approximate solutions used by other authors has been made, which indicates the useful working range of the approximate solutions.

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