Showing papers on "Discontinuity (geotechnical engineering) published in 1976"

Heterojunction band discontinuities

Abstract: The discontinuity ΔEc=0.56 eV in the conduction band edge at n‐CdS/p‐InP junctions is reported. This discontinuity and others are compared with photoemission data and with Van Vechten’s extension of these data to many tetrahedrally coordinated semiconductors. Agreement between measured discontinuities and theoretical predictions is very good. Predictions are made for band parameters pertinent to interfaces involving AIIBIVCV2 compounds with zinc blende, chalcopyrite, or wurtzite crystal structures.

First order magnetisation processes in Pr 2 (Co 1-x Fe x ) 17 alloys

Abstract: The discontinuity in the hard direction magnetisation curve for the alloy Pr 2 (Co 0.6 Fe 0.4 ) 17 has been studied over the temperature rauge 5K-300K using a partially aligned polycrystalline sample. By means of the singular point detection technique we have measured the temperature variation of the anisotropy field and also the position of the magnetisation discontinuity. We conclude that the discontinuity is associated with a first-order rotation of the magnetisation vector, and its appearance as temperature is lowered is due to the rapid decrease of the second anisotrcpy constant K 2 to below a negative value K 2 = -K 1 /6. Analysis of the anisotropy constants obtained by Shanley for a Pr 2 (Co 0.8 Fe 0.2 ) 17 alloy enable a good estimate to be made of the position of the anomalous discontinuity for this alloy.

Upper mantle structure in western Canada

Abstract: Several upper mantle velocity distributions in western Canada are determined from short-period (1–10 Hz) body wave (P) observations. With the use of quantized ray theory, synthetic seismograms were constructed for laterally homogeneous earth models to satisfy the absolute travel time of first arrivals and the differential travel times and relative amplitudes of later arrivals. On the basis of travel time and amplitude observations, three models were obtained that correspond to three different regions. All of the three models show the presence of a low-velocity zone and discontinuities at 410 and 650 km. Of the three models, models WCA and WCB show the presence of a discontinuity in slope at about 504 km, but this is absent in the model WCC. Models WCA and WCB differ in their thickness of the lithosphere, the absolute velocity below the base of low-velocity zone, and the gradient of the velocity between the base of the low-velocity zone and 300 km of depth. Beyond 300 km, models WCA and WCB have the same velocity distribution. An extremal inversion determination of the depth limits to the discontinuities at 410 and 650 km indicates a maximum uncertainty of about ±30 km in depth to the discontinuities. An analysis of reduced delay times for the reflection from the 410-km discontinuity indicates a local down-buckling of the 410-km discontinuity by 30 km under the Cordillera.

Seeing through rock salt with radar

Abstract: A VHF radar has been used in a salt mine in the Cote Blanche Salt Dome to probe horizontally for the dome Rank and vertically for the top of the salt. Discontinuities in the salt’s complex electric permittivity caused by anhydrite stringers, shale, sandstone, water, or fractures will cause radar reflections. A narrow beam, f 9 degrees in salt, helps to determine the dire&on to the discontinuity. The time of the radar reflection determines the range to the discontinuity. The maximum one-way penetration was 2040 ft. The radar speed in Cote Blanche salt was measured by timing radar reflections through known distances of salt. The measured radar speed was 188 ft/usec, slightly less than the radar speed in pure salt (203 ft/wsec). A shear zone in the salt was found to have many discontinuities or radar targets. A discontinuity was detected in a pillar which contained an oil well casing, and a discontinuity about 400 ft above the mine level, but still inside the salt, was also found. The top of the salt dome was detected from several locations in the mine.

Channel flow over a smooth-to-rough surface discontinuity with zero pressure gradient

Abstract: Measurements are given for the combined effects of a change of surface roughness and a simultaneous change of pressure gradient. The latter is negative in a fully developed turbulent, two-dimensional smooth channel flow upstream of the discontinuity, but is artifically held to a value of zero in the rough channel following the surface discontinuity. Measurements of mean velocity, turbulent intensity, and wall shear stress in the current zero pressure gradient apparatus are compared with similar measurements made in the same apparatus with a negative pressure gradient in the rough channel. Results indicate that removal of the pressure gradient in the rough channel does not affect the growth rate of the internal boundary layer nor that of the sublayer; nor does the modified pressure gradient greatly reduce the transitional overshoot of wall shear stress and turbulence intensity previously observed.

Channel flow over a smooth-to-rough surface discontinuity with zero pressure gradient

Abstract: Measurements are given for the combined effects of a change of surface roughness and a simultaneous change of pressure gradient. The latter is negative in a fully developed turbulent, two-dimensional smooth channel flow upstream of the discontinuity, but is artifically held to a value of zero in the rough channel following the surface discontinuity. Measurements of mean velocity, turbulent intensity, and wall shear stress in the current zero pressure gradient apparatus are compared with similar measurements made in the same apparatus with a negative pressure gradient in the rough channel. Results indicate that removal of the pressure gradient in the rough channel does not affect the growth rate of the internal boundary layer nor that of the sublayer; nor does the modified pressure gradient greatly reduce the transitional overshoot of wall shear stress and turbulence intensity previously observed.

Pipe turning tool

Abstract: Disclosed are turning tools for elongated agricultural irrigation pipes which lie along the earth's surface and which include longitudinally aligned gated ports along each pipe segment for radial water emergence therefrom. The pipe turning tool, which ensures that the gated watering ports can be positioned the appropriate distance above the ground, generally comprises: an arcuate shoulder for abutment against the pipe outer side, an elongate handle rigidly attached to the shoulder and extending rearwardly therefrom and away from the pipe, and a fixed positioned stationary detent extending downwardly from a rigidly secured header and which detent is engageable with a radial discontinuity on the pipe thereby effecting turning about the pipe central-axis. Alternate tool embodiments are disclosed appropriate for use with latch-recess type radial pipe protuberances and depending upon the latch-recess spatial relationship to the aligned gated ports.

Further observations on the shape of the S/N curve of a ferritic steel

Abstract: The effect of testing frequencies at levels of 50 and 100 Hz on the shape of the S/N curves of an EnlA steel has been investigated. Axial loadings of the zero to peak (R = 0) and completely reversed (R = −1) types were applied to plain testpieces and the results are compared with rotating cantilever testing. At 50 Hz two discontinuities were observed in the S/N curves for both R=O and R=−1 loadings. At 100 Hz there was no lower discontinuity and the fatigue limit was significantly higher than that obtained at 50 Hz. The role of strain-ageing effects on these observations is discussed.

Stress concentrations in double welded partial joint penetration butt welds

Abstract: Results are presented for photoelastic analyses of stress concentrations in square butt welds that contain a centrally located unwelded area or discontinuity. The discontinuity may be intentional, as in a butt joint design that specifies a partial joint penetration weld, or it may be a defect such as inadequate joint penetration. Two kinds of loading are considered, namely, pure tension and pure bending. In pure tension the stress concentration based on mean plate stress is independent of the depth of the discontinuity when the depth is small and increases very rapidly for depths larger than one-fifth of the plate thickness. A basis is suggested for plotting fatigue test data which should reduce the scatter normally found in such tests. In pure bending the critical stress remains at the toe of the weld reinforcement for all but the largest discontinuities.

Technical note. a short solution for the stability of a rock slope containing a tetrahedral wedge

Abstract: To assist the engineer wishing to make a quick assessment, a solution is presented for the computation of the factor of safety against translational slip of a tetrahedral wedge formed in a rock slope by two intersecting discontinuities, the slope face and the upper ground surface. It does not take into account rotational slip or toppling. The solution allows for different strength parameters and water pressures on the two planes of weakness. It is assumed that the slope crest is horizontal, i.e. The upper ground surface is either horizontal or dips in the same direction as the slope face or at 180 degrees this direction. /TRRL/

Cone Penetration of Granular and Cohesive Soils

Abstract: The mechanics of rigid cone penetration into granular and cohesive soils is developed in three-dimensional form along limit equilibrium principles with solution sought through the method of characteristics. The use of a stress discontinuity condition is required to allow for solution of the problem in situations where abrupt changes in the deforming soil material occur. Comparison of generated forces and failure planes, between experimentally obtained results, and theoretical predictions show good agreement.

Automatic control device for train

Abstract: PURPOSE:To prevent the train from causing delay in response and to remove discontinuity in speed or deceleration during the period of deceleration pattern.

Comments on "Scattering of Surface Waves at a Dielectric Discontinuity on a Planar Waveguide" [Letters]

Abstract: An analysis of the problem of scattering of surface waves at a dielectric discontinuity on a planar waveguide has recently appeared in this TRANSACTIONS. (Letters)

Ossicular discontinuity: OSSICULAR DISCONTINUITY

Abstract: Because of the numerous and varied surgical approaches to ear pathology devised and expanded in the past two decades, we are destined to be confronted with increasingly frequent cases of ossicular defects behind an intact eardrum. Using a technique which is the converse of the established “patch” test a simple office procedure is described which may help establish the diagnosis of ossicular discontinuity in the adult with an intact eardrum. An audiogram is obtained and then a myringotomy performed with insertion of a large ventilation tube. A second audiogram is then done. A rise in the air conduction level, in the absence of fluid, is suggestive of ossicular discontinuity.