Showing papers on "Discontinuity (geotechnical engineering) published in 1984"

Deep seismicity and modes of deformation in Tonga subduction zone

Abstract: The geometry of deep (>400 km) earthquakes in the subducting western edge of the Pacific plate, when related to the local distribution of seismic activity, reveals a complex pattern of planes of shear failure, enabling the modes of deformation by which the descending plate shortens and thickens to be identified. The deepest part of the slab is displaced laterally, suggesting that it fails to penetrate the discontinuity at 670 km.

Calculation of the conduction band discontinuity for Ga(0.47)In(0.53)As/Al(0.48)In(0.52)As heterojunction

Abstract: Photoluminescence studies at 4 K on Ga0.47In0.53As/ Al0.48In0.52As single quantum wells exhibit emission ranging from 1.318 eV for a 15‐A well to 0.82 eV for thick wells. The emission energy of each single quantum well is compared to theoretical curves which are generated from a finite potential square well model. The closest agreement between the experimental curves and the theoretical curves occurs when the conduction band discontinuity is taken to be 70% of the band‐gap discontinuity or 0.52 eV.

Transverse Resonance Analysis Discontinuities of Finline

Abstract: A method of analysis is proposed for characterizing finline discontinuities. Two conducting or magnetic planes are inserted at some distances away from the discontinuity so as to obtain a closed resonant structure. A transverse resonance technique is then used to compute the resonant frequencies and, from these, the equivalent circuit parameters of the discontinuity. In the particular case when the discontinuity is removed, the method can be used to characterize uniform finlines.

Acoustic Microscopy of Elastic Discontinuities

Abstract: In the reflection-scanning acoustic microscope, interference fringes may be obtained from cracks and grain boundaries running at an angle to the surface. The periodicity of these fringes suggests that while sometimes they are caused by reflection of longitudinal waves within the specimen, when the feature is approximately normal to the surface, Rayleigh waves are responsible, and this confirms the dominant role played by Rayleigh waves in the contrast in acoustic microscopy. The variation of contrast with defocus may be expressed as a Fourier transform of the reflectance function of a specimen; oscillations in V(z) then arise as the transform of the change in phase around the Rayleigh angle. When Rayleigh waves strike a surface-breaking discontinuity, they may be strongly reflected even though the discontinuity is much less than a wavelength thick. This enables fine cracks and other features which would not be resolved according to conventional criteria to be revealed very clearly in acoustic micrographs.

The magnetopause as a tangential discontinuity for large field rotation angles

Abstract: Three passes of the ISEE 1 and 2 satellites through the dayside terrestrial magnetopause are discussed where the magnetopause is identified as a tangential discontinuity. This identification is based primarily on the failure of the plasma and magnetic field data to satisfy the conditions for a rotational discontinuity. In all these cases the interplanetary magnetic field was directed strongly southward and the angles between the fields on the two sides of the magnetopause ranged between 136 deg and 170 deg. As this is precisely the field geometry thought to be most conducive for reconnection, the magnetopause would be expected to be a rotational discontinuity. The simplest explanation of this result would appear to be that the magnetic field orientation is not the only factor controlling the onset of reconnection. However, as the identification of the discontinuity applies only locally, it cannot be excluded that for the magnetic field conditions investigated here, different portions of the magnetopause can be described as tangential and rotational discontinuities simultaneously.

Fatigue and microcracking of concrete

Abstract: The direct and indirect methods of examining microcracks are reviewed. It is concluded that the discontinuity stress is a fundamental property of concrete. It signifies (1) the end of the quasi-elastic behavior of concrete (2) the long time sustained strength of concrete, (3) the point at which the Poisson's ratio starts to increase, and (4) the point at which mortar cracks begin to develop extensively. However, a logical and measurable definition of discontinuity stress has not yet been found. This paper suggests a new approach to define discontinuity stress based on fatigue tests. The fatigue interactions surface is derived, which reveals a measurable “kink”. This “kink” represents the discontinuity stress. Below this “kink” in the high cycle region, microcracks are developing as bond cracks in a slow gradual process. Above the “kink” in the low cycle region, mortar cracks are forming continuous networks.

Restrictions on Quasi-Statically Moving Surfaces of Strong Discontinuity in Elastic-Plastic Solids

Abstract: This paper educes the restrictions on a hypothesized quasi-statically propagating planar surface of strong discontinuity in an elastic-plastic solid. The derivation treats a solid under general three-dimensional conditions, employing a “small strain” formulation; the principal constitutive assumptions are that the elastic part of total strain be linearly related (although with arbitrary anisotropy) to the stress state, that the material possess a positive definite elastic strain energy function, and that inelastic deformation occur in accordance with the principle of maximum plastic resistance. It is proved that under these conditions all components of stress must be continuous across such a propagating surface. Further, the only components of strain which may suffer discontinuities across such a surface are shown to be the plastic components which do not deform elements in the plane of the surface, and these may be discontinuous only if the stress state at the moving surface meets certain specific conditions.

Detecting Developmental Discontinuities

Abstract: In a sense, discontinuities are commonplace. In cognitive-developmental psychology, discontinuity typically refers to qualitative change, and behavior undergoes qualitative change routinely. Whenever people learn something new, some part of their behavior shows qualitative change.

Investigation of a lower mantle shear wave triplication using a broadband array

Abstract: SH signals recorded by an array of four broadband (Benioff 1-90) instruments, run by Caltech, are inspected for evidence of a lower mantle shear wave velocity discontinuity previously detected using WWSSN data. Deep focus earthquakes beneath Argentina span the distance range 78° to 82° from the array, where the triplication in the travel time curve produced by the discontinuity is expected to result in an arrival between the direct shear wave, S, and the reflection off of the core-mantle boundary, ScS. The SH data for these events do show evidence of the arrival; however, the broadband signals also show significant receiver structure complexity. Empirical receiver functions are determined for each station by stacking observations for events in South America closer than 75° from the array. Incorporating these receiver functions into the synthetic modeling demonstrates that lower mantle shear velocity models with a discontinuity fit the observations better than models without one.

Power loss at a step discontinuity in an asymmetrical dielectric slab waveguide

Abstract: Power loss at an abrupt but small step discontinuity in an asymmetrical single-mode waveguide is analyzed. An integral expression is given for the power loss suffered by the transverse-electric and transverse-magnetic modes as a function of wavelength, film index, cover index, substrate index, and input and output waveguide widths so that any slab-waveguide discontinuity can be analyzed. Normalized power-loss plots are presented for two specific, commonly used waveguides with different degrees of asymmetry. It is shown that the magnitude of the power loss at a discontinuity depends more on the mismatch in the modal effective width than on the geometrical mismatch in waveguide width. In particular, close to cutoff, guides exhibit severe power loss even for small step size, whereas waveguides that are sufficiently far away from cutoff can tolerate a relatively large step discontinuity with surprisingly low power loss.

The effect of a surface discontinuity on an axisymmetric boundary layer

Abstract: Etude de la couche limite sur un corps de revolution elance pour trois tailles differentes du rayon du corps. Dans tous les cas l'ecoulement a une structure a trois couches

The occurrence of isothermal discontinuities in relativistic fluids

Abstract: The effect of radiation on the appearance of an isothermal discontinuity in a relativistic shock wave is considered. When the postshock speed of sound is small compared to the speed of light, algebraic relations are found for the allowed ratios of radiation pressure to matter pressure and for the amplitude of the isothermal discontinuity.

A Metaphorics of Fiction: Discontinuity and Discourse in the Modern Novel

Abstract: by \"the rigid boundaries erected by the farming community\" and \"the corrosive influence of the land\" (36-37). Once again, I do not find the unremitting determinism in these texts that Budhos seems to, but I am struck by her perception that: \"In every instance, Lessing points to a direct connection between the illusion of possibilities (expanses) and the actual limitations (enclosure) placed upon community and women\" (43).

Transverse resonance analysis

Abstract: A transverse resonance technique is used to compute the resonant frequencies of a finline resonator containing the discontinuity to be analyzed. From this, the parameters of the equivalent circuit of the discontinuity are evaluated as functions of frequency and geometry of the structure.

Method of producing pipes with crack arresters

Abstract: Disclosed is a method of producing crack arrester consisting in that a hollow cylindrical blank (1) with a multi-layer wall and a discontinuity (2) provided at least in one of the layers is made so that the diameter and wall thickness thereof are smaller and greater, respectively, than the specified final dimensions of the crack arrester (5) and the blank (1) is then heated and rolled on a ring-rolling mill (4) uniformly over the entire length to the final dimensions of the crack arrester (5) so that the layers fuse to each other in the course of rolling.