Increase In Initial Density Research Articles

Change in structure of a detonation wave in 2′,2′,2′-trinitroethyl-4,4,4-trinitrobutyrate with initial density increase

Change in structure of a detonation wave in 2′,2′,2′-trinitroethyl-4,4,4-trinitrobutyrate with initial density increase

Strengthening of water glass and colloidal sol based silica gels by aging in TEOS

Previous work demonstrated that gels can be strengthened and stiffened by providing new monomers to the alcogel thus giving xerogels ambient pressure dried with properties similar to aerogels with porosity up to 90%. That work is extended to increase the strength and stiffness of wet gels obtained from cheaper water soluble sodium silicate (water glass) and colloidal silica sols (3 and 6 nm). During aging the water glass based gels in a TEOS solution, a more than 10-fold increase in shear G modulus was obtained within 27 h, showing a very high reactivity of this system compared to alkoxide based gels. Water glass based gels generally show a lower xerogel density compared to the gels prepared from colloidal sols and a xerogel density of 0.22 g/cm 3 was obtained. Starting from colloidal sols, a smaller increase in G was observed for the same increase in initial density, however, the larger particle size and hence pore size of these gels reduces the capillary pressure during drying, giving low density xerogels. A lower density was obtained for the xerogels prepared from 6 nm sol compared to 3 nm sol for the gels aged in TEOS. A large decrease in xerogel density was observed when the colloidal sol based gels were aged in TEOS.

The evolution of radio galaxies - A VLA survey of high-redshift clusters of galaxies

view Abstract Citations (12) References (7) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The evolution of radio galaxies: A VLA survey of high-redshift clusters of galaxies Jaffe, W. Abstract Data from a VLA 1465 MHz survey of high-redshift galaxy clusters with redshifts of 0.25 to 0.9 are presented. Sources are detected in 13 of 55 clusters. The sample shows strong evolution of the radio luminosity function (RLF) during this period even for weak cluster radio galaxies, i.e., those with log P1465 between 24.4 and 25.4 W/Hz. The changes in the RLF with redshift for these galaxies include an increase in the characteristic luminosity above which the slope of the RLF steepens and a moderation or reversal of the initial increase in density of weak sources at larger redshifts. Publication: The Astrophysical Journal Pub Date: November 1982 DOI: 10.1086/160391 Bibcode: 1982ApJ...262...15J Keywords: Galactic Clusters; Galactic Evolution; Radio Galaxies; Red Shift; Antenna Arrays; Luminosity; Radio Sources (Astronomy); Astronomy full text sources ADS | data products NED (36)

Rectangular plate loading test on snow

To predict vehicle mobility or drawbar pull of tracked oversnow vehicle on snow covered terrain, the fundamental relation between the structural properties of snow and deformation energy of snow due to compression were studied experimentally. For this purpose, rectangular plate (7.6 cm × 7.6 cm) loading tests at high deformation rate (3.7mm/sec) were carried out for several types of fresh snow and sintered snow in a cold room at constant temperature -13°C ± 1°C. This new apparatus for rectangular plats loading tests is designed as a strain controlled system, and also for penetration and rotation test of vane cones.The relation between penetration resistance and depth of penetration of a rectangular plate show elastoplastic behaviour and a saw-toothed effect due to the microfracture of snow until the density of snow reaches the threshold density. As a result, it is shown that the deformation energy due to compression of snow decreases with the increase of the coefficient of propagation of plastic compression. For fresh snow having an initial density of 0.18 to 0.42g/cm3, the elastic modulus increases from 6 × 10-3 to 7.8 × 10-2kg/cm2 · cm and the coefficient of propagation of plastic compression decreases from 5.8 to 3.0, with the increase of initial density. For sintered snow having an initial density of 0.40g/cm3, the initial density does not vary but the elastic modulus increases from 1.00 to 3.10 kg/cm2 · cm and the coefficient of propagation of plastic compression decreases from 3.2 to 2.1, with the increase of age of sintered snow.Thus the relations between coefficient of propagation of plastic compression and deformation energy due to settlement of an oversnow vehicle have been analysed for several types of fresh and sintered snow.

Molecular motions in compressed liquid water

Proton and deuteron NMR spin–lattice relaxation times in liquid water and heavy water were measured as a function of pressure and temperature in the range 10–90°C and 1 bar–9 kbar. D2O was also studied at 150 and 200°C. Availability of density and viscosity data under these experimental conditions enabled us to separate the effects of temperature and density on the spin–lattice relaxation times, T1, and viscosities. Under the assumption that the intermolecular dipolar contribution to the proton T1 follows the changes in shear viscosity with temperature and density, we separated the intramolecular and intermolecular dipolar contributions to the proton T1. We found that at a temperature of 10°C the initial increase in density leads to faster reorientation of the water molecules. The effect was much smaller at 30°C. Analysis of the experimental data on H2O and D2O leads to the conclusion that compression diminishes the coupling between the rotational and translational motions of water molecules. The change in the nature of the rotation–translation coupling with increasing density is mainly responsible for the failure of the Debye equation to describe the density effects on the reorientation of water molecules. In the case of D2O we find a relatively small variation in the deuteron quadrupole coupling constant with increasing density. Its average value is approximately 230 kHz over the range of our experimental conditions. Another experimental finding of this study is the decrease in the activation energies for relaxation and shear viscosity with increasing density. All the experimental evidence indicates that compression of water leads to significant distortion and/or disruption of the hydrogen bond network with the important consequence that the dynamic behavior of water under high compression resembles more that of a ’’normal’’ molecular liquid of comparable molecular size. At high densities the hard core repulsive interactions begin to dominate over the directional interactions which are mainly responsible for the open structure of liquid water at low temperatures and pressures.