Influence of Densification Method on Some aspects of Undrained Silty Sand Behavior

Different specimen preparation methods such as moist tamping, dry funnel deposition, slurry deposition, dry air pluviation have been reported in the literature to investigate the undrained behavior of silty sands. Similarly, different means have been used to densify the soils prepared with such methods. Ongoing research shows that the change in undrained behavior (e.g. change in initial peak deviator stress and instability angle) due to different deposition densities is significantly affected by the densification technique utilized within a particular deposition method. It is believed that those variations are closely related with changes in the initial soil fabric that is achieved after the deposition. In this study, a relatively new densification technique, avoiding mold tapping, is used with the dry funnel deposition method. This new method of densification is thought to create a soil fabric that is much closer to the initial fabric than other techniques. The experimental results show that the change in undrained behavior with increasing density by densification is much less pronounced when compared to the other densification methods reported in the literature

The Effect of Nonplastic Silt Gradation on the Liquefaction Behavior of Sand

Various researchers have published results regarding the effect of non plastic silts on the liquefaction behavior of sands. Some concluded that increasing fines content decrease the liquefaction potential, whereas others observed the opposite. Some of those discrepancies might be explained via various factors such as different confining stresses, different depositional methods, different consolidation histories and possibly different comparison bases (i.e. void ratio, intergranular void ratio, relative density). New experimental results from monotonic undrained triaxial compression tests performed on Nevada Sand-A mixed with different silts indicate that liquefaction behavior is also significantly influenced by the gradation of the fines

Magnetic and Transport Properties of Fe-Ag granular multilayers

Results of magnetization, magnetotransport and Mossbauer spectroscopy measurements of sequentially evaporated Fe-Ag granular composites are presented. The strong magnetic scattering of the conduction electrons is reflected in the sublinear temperature dependence of the resistance and in the large negative magnetoresistance. The simultaneous analysis of the magnetic properties and the transport behavior suggests a bimodal grain size distribution. A detailed quantitative description of the unusual features observed in the transport properties is given

The relationship between fragility, configurational entropy and the potential energy landscape of glass forming liquids

Glass is a microscopically disordered, solid form of matter that results when a fluid is cooled or compressed in such a fashion that it does not crystallise. Almost all types of materials are capable of glass formation -- polymers, metal alloys, and molten salts, to name a few. Given such diversity, organising principles which systematise data concerning glass formation are invaluable. One such principle is the classification of glass formers according to their fragility\cite{fragility}. Fragility measures the rapidity with which a liquid's properties such as viscosity change as the glassy state is approached. Although the relationship between features of the energy landscape of a glass former, its configurational entropy and fragility have been analysed previously (e. g.,\cite{speedyfr}), an understanding of the origins of fragility in these features is far from being well established. Results for a model liquid, whose fragility depends on its bulk density, are presented in this letter. Analysis of the relationship between fragility and quantitative measures of the energy landscape (the complicated dependence of energy on configuration) reveal that the fragility depends on changes in the vibrational properties of individual energy basins, in addition to the total number of such basins present, and their spread in energy. A thermodynamic expression for fragility is derived, which is in quantitative agreement with {\it kinetic} fragilities obtained from the liquid's diffusivity.Comment: 8 pages, 3 figure

Construction of the free energy landscape by the density functional theory

On the basis of the density functional theory, we give a clear definition of the free energy landscape. To show the usefulness of the definition, we construct the free energy landscape for rearrangement of atoms in an FCC crystal of hard spheres. In this description, the cooperatively rearranging region (CRR) is clealy related to the hard spheres involved in the saddle between two adjacent basins. A new concept of the simultaneously rearranging region (SRR) emerges naturally as spheres defined by the difference between two adjacent basins. We show that the SRR and the CRR can be determined explicitly from the free energylandscape.Comment: 11 pages, 3 figures, submitted to J. Chem. Phy

Theoretical Evaluation of the Reaction Rates for 26Al(n,p)26Mg and 26Al(n,a)23Na

The reactions that destroy 26Al in massive stars have significance in a number of astrophysical contexts. We evaluate the reaction rates of 26Al(n,p)26Mg and 26Al(n,a)23Na using cross sections obtained from the codes EMPIRE and TALYS. These have been compared to the published rates obtained from the non-smoker code and to some experimental data. We show that the results obtained from EMPIRE and TALYS are comparable to those from non-smoker. We also show how the theoretical results vary with respect to changes in the input parameters. Finally, we present recommended rates for these reactions using the available experimental data and our new theoretical results

Toeplitz operators with radial symbols on weighted holomorphic Orlicz space

Peer reviewe

Harmonic Vibrational Excitations in Disordered Solids and the "Boson Peak"

We consider a system of coupled classical harmonic oscillators with spatially fluctuating nearest-neighbor force constants on a simple cubic lattice. The model is solved both by numerically diagonalizing the Hamiltonian and by applying the single-bond coherent potential approximation. The results for the density of states $g(\omega)$ are in excellent agreement with each other. As the degree of disorder is increased the system becomes unstable due to the presence of negative force constants. If the system is near the borderline of stability a low-frequency peak appears in the reduced density of states $g(\omega)/\omega^2$ as a precursor of the instability. We argue that this peak is the analogon of the "boson peak", observed in structural glasses. By means of the level distance statistics we show that the peak is not associated with localized states