Earth pressures on retaining walls due to Anisotropic and nonhomogeneous backfills

In this paper an attempt is made to study the lateral earth pressures on retaining walls as affected by anisotropy and non-homogeneity with respect to cohesion, of the backfill. Both the passive and active conditions are studied and the method of characteristics is used in the analysis. Numerical results show that, as the coeficient of anisotropy, k, defined as the ratio of vertical strength to horizontal strength, changes from 0-8 to 2, the pressure at the top of the wall decreases considerably.Also, as k changes fvom 0.8 to 2, the mod$ed passive and active earth pressure coeficients decrease when cohesion increases with depth and are unaffected by k when cohesion is constant with depth. On the other hand, when the rate of increase of cohesion with depth increares, the mod@ed earth pressure coefficients are found to increase considerably.

Entanglement production due to quench dynamics of an anisotropic XY chain in a transverse field

We compute concurrence and negativity as measures of two-spin entanglement generated by a power-law quench (characterized by a rate tau(-1) and an exponent alpha) which takes an anisotropic XY chain in a transverse field through a quantum critical point (QCP). We show that only spins separated by an even number of lattice spacings get entangled in such a process. Moreover, there is a critical rate of quench, tau(-1)(c), above which no two-spin entanglement is generated; the entire entanglement is multipartite. The ratio of the entanglements between consecutive even neighbors can be tuned by changing the quench rate. We also show that for large tau, the concurrence (negativity) scales as root alpha/tau(alpha/tau), and we relate this scaling behavior to defect production by the quench through a QCP.

Unusual Anisotropic Effects from 1,3-Dipolar Cycloadducts of 4-Azidomethyl Coumarins

4-Bromomethylcoumarins (1) reacted with sodium azide in aqueous acetone to give 4-azidomethyl-coumarins (2), which underwent 1,3-dipolar cycloaddition with acetylenic dipolarophiles to give triazoles (3). These triazoles (3) have been found to exhibit interesting variations in the chemical shifts of C-3-H and C-4-methylene protons. Protonation studies indicate that the shielding effect of the C-3-H of coumarin is due to pi-electrons of the triazole ring, further supported by diffraction and computational studies.

Implantation Induced Hardening of Nanocrystalline Titanium Thin Films

Formation of nanocrystalline TiN at low temperatures was demonstrated by combining Pulsed Laser Deposition (PLD) and ion implantation techniques. The Ti films of nominal thickness similar to 250 nm were deposited at a substrate temperature of 200 degrees C by ablating a high pure titanium target in UHV conditions using a nanosecond pulsed Nd:YAG laser operating at 1064 nm. These films were implanted with 100 keV N+ ions with fluence ranging from 1.0 x 10(16) ions/cm(2) to 1.0 x 10(17) ions/cm(2). The structural, compositional and morphological evolutions were tracked using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectrometry (SIMS) and Atomic Force Microscopy (AFM), respectively. TEM analysis revealed that the as-deposited titanium film is an fcc phase. With increasing ion fluence, its structure becomes amorphous phase before precipitation of nanocrystalline fcc TiN phase. Compositional depth profiles obtained from SIMS have shown the extent of nitrogen concentration gradient in the implantation zone. Both as-deposited and ion implanted films showed much higher hardness as compared to the bulk titanium. AFM studies revealed a gradual increase in surface roughness leading to surface patterning with increase in ion fluence.

Approximate methods for step function response of undamped non-linear spring mass systems with arbitrary hardening type spring characteristic

The possibility of applying two approximate methods for determining the salient features of response of undamped non-linear spring mass systems subjected to a step input, is examined. The results obtained on the basis of these approximate methods are compared with the exact results that are available for some particular types of spring characteristics. The extension of the approximate methods for non-linear systems with general polynomial restoring force characteristics is indicated.

A rectangular laminated anisotropic shallow thin shell finite element

This report contains the details of the development of the stiffness matrix for a rectangular laminated anisotropic shallow thin shell finite element. The derivation is done under linear thin shell assumptions. Expressing the assumed displacement state over the middle surface of the shell as products of one-dimensional first-order Hermite interpolation polynomials, it is possible to insure that the displacement state for the assembled set of such elements, to be geometrically admissible. Monotonic convergence of the total potential energy is therefore possible as the modelling is successively refined. The element is systematically evaluated for its performance considering various examples for which analytical or other solutions are available

Anisotropic properties of the layered semiconductor in Te

Anisotropic properties of the Bridgman grown layered semiconductor p-InTe were studied by analyzing the temperature dependence of electrical conductivity and Hall mobility parallel and perpendicular to the layer planes. The mobilities were μamalgamation or coproduct = 50–60 cm2V−1 sec−1 and μperpendicular = 10–15 cm2V−1sec−1 and varied as μ ≈ Tn where n = 1.43 due to impurity scattering. Pressure-induced semiconductor-metal transition occurred at about 50 kbar. The pressure coefficient of resistance was 3 times larger in the direction perpendicular to the layer plane due to the difference between inter and intra-planar bonding.

Stress and strength analysis of pin joints in laminated anisotropic plates

Mechanical joints in composites can be tailored to achieve improved performance and better life by appropriately selecting the laminate parameters. In order to gain the best advantage of this possibility of tailoring the laminate, it is necessary to understand the influence of laminate parameters on the behaviour of joints in composites. Most of the earlier studies in this direction were based on simplified assumptions regarding load transfer at the pin-plate interface and such studies were only carried out on orthotropic and quasi-isotropic laminates. In the present study, a more rigorous analysis is carried out to study pin joints in laminates with anisotropic properties. Two types of laminates with (0/ + ?4/90)s and (0/ ± ?2/90)s layups made out of graphite epoxy T300/5208 material system are considered. The analysis mainly concentrates on clearance fit in which the pin is of smaller diameter compared to the hole. The main aspect of the analysis of pin joints is the changing contact between the pin and the plate with increasing load levels. The analysis is carried out by an iterative finite element technique and a computationally efficient routine is developed for this purpose. Numerical studies indicate that the location and magnitude of the peak stresses along the hole boundary are functions of fibre angle and the overall anisotropic properties. It is also shown that the conventional assumption of cosine distribution for the contact pressure between pin and the plate in the analysis lead to underestimation of bearing failure load and overestimation of shear and tensile failure loads in typical (0/905)s cross-ply laminates.

Coherent-mode decomposition of general anisotropic Gaussian Schell-model beams

We present a complete solution to the problem of coherent-mode decomposition of the most general anisotropic Gaussian Schell-model (AGSM) beams, which constitute a ten-parameter family. Our approach is based on symmetry considerations. Concepts and techniques familiar from the context of quantum mechanics in the two-dimensional plane are used to exploit the Sp(4, R) dynamical symmetry underlying the AGSM problem. We take advantage of the fact that the symplectic group of first-order optical system acts unitarily through the metaplectic operators on the Hilbert space of wave amplitudes over the transverse plane, and, using the Iwasawa decomposition for the metaplectic operator and the classic theorem of Williamson on the normal forms of positive definite symmetric matrices under linear canonical transformations, we demonstrate the unitary equivalence of the AGSM problem to a separable problem earlier studied by Li and Wolf [Opt. Lett. 7, 256 (1982)] and Gori and Guattari [Opt. Commun. 48, 7 (1983)]. This conn ction enables one to write down, almost by inspection, the coherent-mode decomposition of the general AGSM beam. A universal feature of the eigenvalue spectrum of the AGSM family is noted.

Studies on age-hardening characteristics of ceramic particle/matrix interfaces in Al-Cu-SiCp composites using ultra low-load-dynamic microhardness measurements

Ultra low-load-dynamic microhardness testing facilitates the hardness measurements in a very low volume of the material and thus is suited for characterization of the interfaces in MMC's. This paper details the studies on age-hardening behavior of the interfaces in Al-Cu-5SiC(p) composites characterized using this technique. Results of hardness studies have been further substantiated by TEM observations. In the solution-treated condition, hardness is maximum at the particle/matrix interface and decreases with increasing distance from the interface. This could be attributed to the presence of maximum dislocation density at the interface which decreases with increasing distance from the interface. In the case of composites subjected to high temperature aging, hardening at the interface is found to be faster than the bulk matrix and the aging kinetics becomes progressively slower with increasing distance from the interface. This is attributed to the dislocation density gradient at the interface, leading to enhanced nucleation and growth of precipitates at the interface compared to the bulk matrix. TEM observations reveal that the sizes of the precipitates decrease with increasing distance from the interface and thus confirms the retardation in aging kinetics with increasing distance from the interface.

Rotating anisotropic disc of uniform strength

A procedure to design a constant thickness composite disc of uniform strength by radially tailoring the anisotropic elastic constants is proposed. A special case of an isotropic disc with radially varying modulus is also examined. Analytical results are also compared with FEM calculations for two cases of radially varying anisotropy and for an isotropic disc with variable modulus. (C) 1999 Elsevier Science Ltd. All rights reserved.