In an earlier publication 1 the problem of the equilibrium between the two phases in a phaseseparated liquid He 3 -He 4 mixture near 0°K has been discussed on the basis of the theory of impurities in liquid helium put forward by Landau and Pomeranchuk. 2 ' 3 The theory gives the way in which the excitation spectrum of the liquid is modified by the presence of the impurity; e.g., a small concentration X of He 3 modifies the Landau (phonon + roton) excitation spectrum of liquid-helium II by adding a branch of Fermi particles, equal in number to the number of He 3 atoms, and with energy-momentum relation e = -E 3 (X) +p 2 /2m 3 *. The effective mass ra 3 * has been determined from second sound measurements 4 to be 2.5 times the real mass of He 3 at the saturated vapor pressure. The binding energy E s is found 5 from vapor-pressure data to be rather close to L 3°, the latent heat of vaporization per atom of pure liquid He 3 at 0°K, although it actually depends slightly on X. In a similar way the Fermi quasiparticle spectrum of pure liquid He 3 is modified by the addition of a Bose branch when He 4 is dissolved in it. 8 The thermodynamic properties of dilute He s -He 4 mixtures can thus be calculated in a straightforward way using standard formulas of statistical mechanics. In particular, in a mixture in which phase separation has occurred, one can equate the chemical potentials of each isotope in the two phases to obtain the concentration in each phase as a function of T. It was found earlier 1 that the upper He 3 -rich phase is almost pure He 3 for T^ 0.2°K and this has been confirmed by experiment. 7 The theory also shows that it is possible, in principle, for He 3 to remain dissolved in He 4 up to a certain concentration, even at C^K. 1 This is true for any solution in which He 3 is more strongly bound than it is in pure liquid He 3 . The maximum solubility at 0°K, X 0 , is then determined by equating the latent heat of vaporization of He 3 from the solution to that from the pure liquid:-W + *W = -L 3-where kTj? is the Fermi energy of He 3 in solution (calculated for a gas of the same number density and with mass m 3 *). Determinations of E 3 (X) from vapor-pressure data are not at present sufficiently precise to demonstrate that this possibility is realized in nature.A more sensitive method of determining E 3 (X) than from vapor pressures is from measurements of the phase-separation temperatures T$ of dilute solutions of known X. This has been done in the present work by measuring the heat capacity of the solutions under their saturated vapor pressure down to temperatures of about 0.1 °K or less. The solutions were contained in a nylon calorimeter packed with small crystals of cerium magnesium nitrate used as a refrigerant and as a thermometer. The phase separation appears as a discontinuity AC in the specific heat (Fig. 1), as was previously observed at higher temperatures by Ouboter, Beenakker, and Taconis. 5 We found such discontinuities in solutions withX = 0.08, 0.10, 0.12, and 0.15 but not with X = 0.04, 0....

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Waste foundry sand (WFS) is the by-product of the foundry industry. Utilizing it in the construction industry will protect the environment and its natural resources, and enable sustainable construction. WFS was employed in this research as a fractional substitution of natural sand by 0%, 10%, 20%, 30%, and 40% in concrete. Several tests, including workability, compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS), ultrasonic pulse velocity (USPV), Schmidt rebound hammer number (RHN), and residual compressive strengths (RCS) tests were performed to understand the behavior of concrete before and after exposure to elevated temperatures. Test findings showed that the strength characteristics were increased by including WFS at all the phases. For a substitute rate of 30%, the maximum compressive, splitting tensile, and flexural strength were observed. Replacement with WFS enhanced the 28-day compressive, splitting tensile, and flexural strength by 7.82%, 9.87%, and 10.35%, respectively at a 30% replacement level, and showed continuous improvement until the age of 91 days. The RCS of foundry sand concrete after one month of air cooling at ambient temperature after exposing to 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, and 800 °C was found to be in the range of 67.50% to 71.00%, 57.50% to 61.50%, 49.00% to 51.50%, 38% to 41%, 31% to 35% and 26% to 31.5% of unheated compressive strength values for 0% to 40% replacement of WFS, respectively. The RCS decreases with increasing temperature; however, with increasing WFS, the RCS was enhanced in comparison to the control samples. In addition, the replacement of 30% yielded excellent outcomes. Hence, this study provides a sustainable construction material that will preserve the Earth’s natural resources and provide a best use of WFS.

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In this paper, numerical simulations are performed in a single and double lid driven square cavity to study the flow of a Bingham viscoplastic fluid. The governing equations are discretized with the help of finite element method in space and the nonconforming Stokes elementQ~1/Q0is utilized which gives 2nd-order accuracy for velocity and 1st-order accuracy for pressure. The discretized systems of nonlinear equations are treated by using the Newton method and the inner linear subproablems are solved by the direct solver UMFPACK. A qualitative comparison is done with the results reported in the literature. In addition to these comparisons, some new reference data for the kinetic energy is generated. All these implementations are done in the open source software package FEATFLOW which is a general purpose finite element based solver package for solving partial differential equations.

Despite presenting a very high global warming toll, Portland cement concrete is the most widely used construction material in the world. The eco-efficiency, economy, and the overall mechanical and durability performances of concrete can be improved by incorporating supplementary cementitious materials (SCMs) as partial substitutions to ordinary Portland cement (OPC). Naturally found bentonite possesses pozzolanic properties and has very low carbon footprint compared to OPC. By applying activation techniques, the reactivity of bentonite can be improved, and its incorporation levels can be maximized. In this study, the influence of mechanical and thermo-mechanical activation of bentonite is investigated on properties of concrete. Bentonite was used for 0%, 10%, 15%, 20%, 25%, 30%, and 35% mass replacements of OPC. Mechanical (compressive strength and split tensile strength) and durability (water absorption, sorptivity coefficient, and acid attack resistance) properties were studied. Results of experimental testing revealed that, concrete containing bentonite showed good mechanical performance, while durability was significantly improved relative to control mix. Application of thermo-mechanical activation can enhance the incorporation levels of bentonite in concrete. At 15% and 25%, bentonite produced optimum results for mechanical and thermo-mechanical activation, respectively. Bentonite inclusion is more beneficial to the durability than the mechanical strength of concrete.