Observations on the Constitution and Characterization of Paving Asphalts

This paper contains results of analyses with asphalts of various composition and derivation. The objective of the study is to define and correlate constitution and fundamental character of asphalts in a manner significant to their use in highway pavements. Further confirmation of the existence of three discrete solubility fractions in asphalts was obtained by extraction methods and by paper partition chromatography. Paraffin bodies were revealed by microscopic examination of thin films. Asphaltene fractions showed the presence of particulate material by electron microscopy and also revealed indications of peptized asphaltene bodies. Oils dialyzed from asphalt exhibited u.v. fluorescence similar to components of the oil fractions obtained by extraction. Oven tests revealed increases in asphaltenes and resin fractions and attendant hardening of the asphalt. It is suggested that proper interpretation of asphalt composition is contingent upon adequate means for measuring the fundamental shearing characteristics and other rheological properties of the composite asphalt

Poisson's ratio in cryocrystals under pressure

We present results of lattice dynamics calculations of Poisson's ratio (PR) for solid hydrogen and rare gas solids (He, Ne, Ar, Kr and Xe) under pressure. Using two complementary approaches - the semi-empirical many-body calculations and the first-principle density-functional theory calculations we found three different types of pressure dependencies of PR. While for solid helium PR monotonically decreases with rising pressure, for Ar, Kr, and Xe it monotonically increases with pressure. For solid hydrogen and Ne the pressure dependencies of PR are non-monotonic displaying rather deep minimums. The role of the intermolecular potentials in this diversity of patterns is discussed.Comment: Fizika Nizkikh Temperatur 41, 571 (2015

Study of methane fuel for subsonic transport aircraft

The cost and performance were defined for commercial transport using liquid methane including its fuel system and the ground facility complex required for the processing and storage of methane. A cost and performance comparison was made with Jet A and hydrogen powered aircraft of the same payload and range capability. Extensive design work was done on cryogenic fuel tanks, insulation systems as well as the fuel system itself. Three candidate fuel tank locations were evaluated, i.e., fuselage tanks, wing tanks or external pylon tanks

Effects of propeller rotation direction on airplane interior noise levels

Interior noise measurements for upsweeping and downsweeping movement of the propeller blade tips past the fuselage were made on a twin-engine airplane and on two simplified fuselage models. Changes in interior noise levels of as much as 8 dB reversal of propeller rotation direction were measured for some configurations and test conditions

Electromagnetic Structure Resonances in Inhomogeneous Plasma Layers

Laser-light absorption and radiation forces are investigated for weakly collisional (_/__1), rigid, two-step plasma profiles in planar and spherical geometry. For the first step near critical density, the second step above critical, and appropriate step lengths, we find strong absorption even for weakly collisional plasmas. We show, however, that the radiation forces may not permit such profiles to persist in realistic, dynamic situations.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86119/1/PhysRevLett.40.30-RKO.pd

Effects of seawater and deionized water at 0 to 80 deg C on the flexural properties of a glass/epoxy composite

The effect on the flexural properties of a glass/epoxy composite of immersion in deionized water or seawater at 0, 25, and 80 C for 451 hr was examined. The percent weight gain at 0 and 25 C was low (0.06 to 0.17 percent) and there was no significant change in the flexural properties for these environmental conditions. At 80 C there was a decrease in the flexural strength of 17 and 20 percent in seawater and deionized water, respectively. This is a comparison to control samples exposed to 80 C heat alone. These decreases were found to be nearly reversible once the samples were dried. Optical microscopy did not reveal cracking of the matrix. The flexural modulus was essentially unaffected by exposure to deionized water and seawater at 80 C

Triple minima in free energy of semiflexible polymers

We study the free energy of the worm-like-chain model, in the constant-extension ensemble, as a function of the stiffness for finite chains of length L. We find that the polymer properties obtained in this ensemble are "qualitatively" different from those obtained using constant-force ensembles. In particular we find that as we change the stiffness parameter, the polymer makes a transition from the flexible to the rigid phase and there is an intermediate regime of parameter values where the free energy has three minima and both phases are stable. This leads to interesting features in the force-extension curves.Comment: Published version, 4 pages, 5 figures, revte

Shear stress fluctuations in the granular liquid and solid phases

We report on experimentally observed shear stress fluctuations in both granular solid and fluid states, showing that they are non-Gaussian at low shear rates, reflecting the predominance of correlated structures (force chains) in the solidlike phase, which also exhibit finite rigidity to shear. Peaks in the rigidity and the stress distribution's skewness indicate that a change to the force-bearing mechanism occurs at the transition to fluid behaviour, which, it is shown, can be predicted from the behaviour of the stress at lower shear rates. In the fluid state stress is Gaussian distributed, suggesting that the central limit theorem holds. The fibre bundle model with random load sharing effectively reproduces the stress distribution at the yield point and also exhibits the exponential stress distribution anticipated from extant work on stress propagation in granular materials.Comment: 11 pages, 3 figures, latex. Replacement adds journal reference and addresses referee comment

Bounds for the time to failure of hierarchical systems of fracture

For years limited Monte Carlo simulations have led to the suspicion that the time to failure of hierarchically organized load-transfer models of fracture is non-zero for sets of infinite size. This fact could have a profound significance in engineering practice and also in geophysics. Here, we develop an exact algebraic iterative method to compute the successive time intervals for individual breaking in systems of height $n$ in terms of the information calculated in the previous height $n-1$. As a byproduct of this method, rigorous lower and higher bounds for the time to failure of very large systems are easily obtained. The asymptotic behavior of the resulting lower bound leads to the evidence that the above mentioned suspicion is actually true.Comment: Final version. To appear in Phys. Rev. E, Feb 199