Implementation of a Classical Theory for Superfluids

The superfluidity of helium-4 is explained until today by a quantum theory: the Bose-Einstein condensation. This theory is rather satisfactory in describing the superfluid state of helium-4 because this one is a system made up of bosons (particles of integer spin). However, the discovery of the superfluidity of helium-3 in 1971 called into question the veracity of this quantum theory. In fact, helium-3 being a system composed of fermions (particles of half-integer spin), it cannot be subject to Bose-Einstein condensation. It is to correct this deficiency that we introduce here a classical (non-quantum) theory of superfluids. This new theory makes no difference between the λ transition of bosons and that of fermions. It is based on a fundamental law: “in a superfluid, density is conserved”. In this work, we have shown that this simple law explains not only the zero viscosity of superfluids but also the surprising phenomena observed in the superfluid state, I quote the liquidity of helium at normal pressure down to 0 K, vaporization without boiling, high thermal conductivity, the fountain effect, the ability to go up one side of the wall of a container to come down on the other side and the existence of a critical velocity.

Structural,electronic and elastic properties of YCu from first principles

The structural, electronic and elastic properties of YCu compound in the B2 （CsCl） phase were investigated using the density functional theory （DFT） within the generalized gradient approximation （GGA）. The electronic density of states （DOS） obtained in this way accorded weU with the results of a recent study utilizing the full-potential linearized augmented plane wave （FLAPW） method. We also found that the density of d-states at the Fermi energy was low. The calculated equilibrium properties such as lattice constant, bulk modulus and its first derivative, and the elastic constants were in good agreement with experimental and theoretical results.

Representative volume element of asphalt pavement for electromagnetic measurements

The motivation for this study was to investigate the representative volume element （RVE） needed to correlate the nondestructive electromagnetic （EM） measurements with the con- ventional destructive asphalt pavement quality control measurements. A large pavement rehabilitation contract was used as the test site for the experiment. Pavement cores were drilled from the same locations where the stationary and continuous Ground Penetrating Radar （GPR） measurements were obtained. Laboratory measurements included testing the bulk density of cores using two methods, the surface-saturated dry method and determining bulk density by dimensions. Also, Vector Network Analyzer （VNA） and the through specimen transmission configuration were employed at microwave frequencies to measure the reference dielectric constant of cores using two different footprint areas and therefore vol- ume elements. The RVE for EM measurements turns out to be frequency dependent; therefore in addition to being dependent on asphalt mixture type and method of obtaining bulk density, it is dependent on the resolution of the EM method used. Then, although the average bulk property results agreed with theoretical formulations of higher core air void content giving a lower dielectric constant, for the individual cores there was no correlation for the VNA measurements because the volume element seizes deviated. Similarly, GPR technique was unable to capture the spatial variation of pavement air voids measured from the 150-mm drill cores. More research is needed to determine the usable RVE for asphalt.