Showing papers on "Slab published in 1980"

The dynamical origin of subduction zone topography

Abstract: Summary. Subduction zones are expressed topographically by long linear oceanic trenches flanked by a low outer rise on the seaward side and an island arc on the landward side. This topographic structure is reflected in free air gravity anomalies, suggesting that much of the topography originates from dynamical forces applied at the base of the crust. We have successfully reproduced the general topographic features of subduction zones by supposing that the stresses generated by the bending of the viscous lower lithosphere as it subducts are transmitted through the thin elastic upper portion of the lithosphere. The trench is due to a zone of extensional flow (associated with low pressure) in the upper part of the viscous lithosphere. The stresses in the subducting slab are computed using a finite element technique, assuming a Maxwell viscoelastic constitutive relation. Various dips (10 to 90") were investigated, as well as depth dependent and nonNewtonian (power law, n = 3) viscosities. Observed subduction zone dimensions are well reproduced by these models. The effective viscosity required at mid-depth in the lithosphere is about 6 x lo2* P. This low value is probably due to the stress dependence of the effective viscosity. However, these models also show that the topography of the subduction zone depends primarily upon the geometry of the subducting slab (dip, radius of curvature of the bend) rather than upon' its rheology. Shear stresses beneath the trench reach maxima of approximately 50 MPa. An interesting feature of some solutions is a dynamically supported bench or platform between the trench and island arc.

Mechanics of subducted lithosphere

Abstract: Some simple mechanical models of subducted lithosphere, combined with observations of Benioff seismic zones, challenge some commonly accepted views of descending lithospheric slabs. The great thermal inertia of subducted slabs results in very large negative buoyancy forces, and phase changes may provide significant additional downward forces, but it is not clear what opposing forces are large enough to balance these. For slabs which do not penetrate beyond a depth of 650 km, the only reasonable possibilities seem to be frictional stresses of about 0.2 GPa (2 kbar) in shallow fault zones or viscous resistance from the surrounding mantle, which requires effective viscosities of at least 5×1021 Pa s (5×1022 P), significantly greater than viscosities inferred from post-glacial rebound. Although more deeply penetrating slabs might encounter additional resistance below 650 km depth, this resistance seems unlikely to be able to provide significant support for the slab since the slab would probably buckle, whether or not compressional stresses are limited by brittle or ductile yielding; in any case, the slab would probably only be supported episodically, if at all, and the results of buckling or fracture should be more evident in Benioff zones. Again the only reasonable alternatives seem to be large shallow frictional stresses or a high-viscosity upper mantle, which would slow the growth of buckling instabilities.

Structural analysis of concrete pavement systems

Abstract: Performance of concrete pavements is controlled by the behavior and performance of the jointing system used, especially the performance and load transfer efficiency of the joint. A finite-element program is presented that includes the analysis of slabs with various joint systems in PCC pavements. Dowelled joints, joints with aggregate interlock, and joints with various types of load transfer schemes can be taken into account during the analysis of the slab under load rather than analyzing the slab and joint systems separately and superimposing the results. The program described is also capable of analyzing slabs comprised of two layers with different material properties, either bonded together or unbonded. Slab thickness, slab modulus values, and subgrade support values can each be varied at each node point in the program to evaluate jointed slabs of nonuniform stiffness and nonuniform support.

Fracture Mechanical Models of Dry Slab Avalanche Release

Abstract: Experimental evidence shows that snow is a pressure sensitive, dilatant, strain-softening material in slow, constant rate, shear deformation. When strain softening initiates in a weak layer underneath a snow slab, avalanche release is hypothesized to be possible with or without additional loading. Specifically, two cases are discussed: (1) a shear-crack-like disturbance can initiate after formation of a slip surface in the weak layer and traverse the layer by a self-propagating progressive failure with or even without loading, and (2) a self-propagating shear instability can develop when a region of the weak layer is driven past peak shear strength by loading. For these cases the implied fracture sequence, fracture geometry, time scale of release, and temperature effects are discussed and shown to be consistent with the known facts of dry slab avalanche release.

Photometric evaluation of slab gels I. Data acquisition and image analysis

Abstract: The photometry of two‐dimensional electrophoretograms is described in some detail. This method has a high sensitivity of 5·10−4 O.D., because it takes advantage of the noise characteristics of photometric signals. Digital image analysis is used to locate and evaluate the individual spots on the electrophoretogram. The presented procedure of segmentation detects the faintest protein spots visible by eye and separates even confluent spots reliably and automatically. The combination of scanning photometry and image analysis is a sensitive, versatile, and accurate method for the evaluation of slab gels.

Electromagnetic absorption in a multilayered slab model of tissue under near-field exposure conditions

Abstract: The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.

Leaky modes in active three-layer slab waveguides

Abstract: We present a comprehensive numerical mode calculation based on a phenomenological theory for a three-layer slab waveguide with a refractive-index depression but finite gain in the centre region (leaky modes). The leaking rays and the refraction loss of the modes are discussed as well as their influence on the threshold conditions for typical stripe-geometry laser structures. Special attention is paid to the transition regime between refractive-index depression and enhancement. i.e. between leaky-mode ‘antiguiding’ and mode ‘guiding’. The results are compared with simple analytical formulas available from the literature.

Production of aluminum alloy sheet

Abstract: Fine-grained, formable Al-Mn alloy sheet is produced from strip-cast slab (eg twin-roll-cast slab) by including 13-23% Mn in the alloy, slab annealing the workpiece by heating it to precipitate most of the Mn in fine intermetallic particles, cold rolling the workpiece to sheet of final gauge with an interanneal performed (between successive cold rolling stages) under nonrecrystallizing conditions to reduce the amount of Mn present in solid solution in the aluminum matrix, and annealing the final sheet

Cladding element for façade surfaces

Abstract: This facing element consists of a narrow, thin, fibre-reinforced concrete or synthetic resin dispersion concrete slab (4) which can be put together on a substructure to form a smooth facade totally sealed against driving rain, in the manner of a composite brickwork structure. The slab consists of a front slab part (3) which is designed as an exposed surface in the manner of natural-cleft limestone brickwork, or which is inlaid with facing slabs of natural stone, ceramic, ashlar or glass, visually divided by shallow closed or deep partially open joints (1), and of a smooth slab part (2) which is offset rearwards parallel by a slab thickness, is hung on and/or fastened to the substructure and is covered by the front slab part (3) of the overlaid facing element. The two slab parts (2 and 3) are offset laterally relative to one another in a particular embodiment, so that even with partially open joints no crossjoint is visible and the elements can be fitted together to form a totally leaktight facade.

Dome Effect in RC Slabs: Rigid-Plastic Analysis

Abstract: The literature on compressive membrane action (dome effect) in restrained slabs is reviewed with emphasis on plastic analysis. The differences between the flow theory and deformation theory approaches are discussed. The example of the rigid-plastic restrained slab strip is used to show that deformation theory may lead to unrealistic predictions.

Method of and apparatus for cutting stone panels

Abstract: The method comprises bonding a backing layer to the opposed faces of a slab (29) of stone, supporting the slab (29) with backing layers attached, in an upward position on its edge cutting the slab (29) along a cutting plane parallel to and midway between the opposed faces of the slab to a depth which is about half the depth of the stab, tumbling the stab (29) on to its opposite longitudinal edge, and cutting through the remainder of the depth of the slab to leave a lamina of stone adhered to each backing layer. Apparatus for carrying out the aforesaid method comprises a saw (1) having two disc blades (3,4), a bogie (7) movable beneath the saw and having a pair of vacuum-operated slab-gripping devices (14) each of which is adapted to support a slab (29) upwardly on its edge, and a second bogie movable in a direction transverse to the first bogie (7) and carrying means for tumbling a slab (29) supported on one longitudinal edge, through 180°, so that it rests on its opposite longitudinal edge.

Concrete slab assembly, especially for building facades

Abstract: A concrete plate assembly, eg as load carrying members or for building facades, comprises an inner concrete slab, an outer concrete slab spaced from the inner slab, and at least one main or stress-absorbing anchor embedded and interconnecting the slabs which are reinforced The intervening space can be filled with an insulation and/or can constitute an insulating air space According to the invention, at least one of the concrete slabs in the region of the connecting anchor, is provided with a closed reinforcing ring which lies in the plane of the slab, preferably midway of the cross section thereof, the anchor being embedded in the concrete within the reinforcing ring and preferably centrally thereof

Dome Effect in RC Slabs: Elastic-Plastic Analysis

Abstract: The influence of elastic deformations on compressive membrane action (dome effect) in restrained slabs is considered. The elastic-plastic circular slab is analyzed, using a flow-theory approach. The inplane and boundary flexibilities are lumped and an initial elastic deflection is assumed. The first part of the predicted load-deflection curve is compared with the results of a test series and reasonable agreement is found, especially with respect to the peak load.

Method of overlay and sandwich formation of pervious concrete

Abstract: A method of overlay and sandwich formation of a combination of pervious concrete with itself and/or standard cement concrete wherein the existing surface is cleaned either mechanically or chemically, a coating of cement and water mortar, mixed in a high energy/shear type mixer, is then applied, and pervious concrete is directly applied to any required thickness, which results in a complete bonding between the overlay and the original pavement. To apply pervious concrete to reinforced concrete slab construction, in cases where lateral water movement may be undesirable, a similar procedure is used after transverse penetration of the reinforced slab with holes spaced so as to clear reinforcing steel and of sufficient size and area to permit the drainage of the combined slab. These holes will be filled with pervious concrete during the overlay procedure.

The spin correlation functions of a finite-thickness ferromagnetic slab

Abstract: Explicit expressions are derived for the Green functions between a pair of spin operators at any two sites within a Heisenberg ferromagnetic slab of finite thickness. These Green functions are found to contain a description of the bulk spin waves and surface spin waves, together with their spectral weighting factors. The results are employed to evaluate the magnetisation in the ferromagnet as a function of temperature and distance from the surfaces.

Slab and holder for face pumped slab laser

Abstract: A face pumped slab laser includes a housing within a resonator cavity for housing a slab of host material and a light source for pumping the slab. The slab is mounted in a holder which is readily inserted in or retracted from the housing. The holder rigidly supports the slab without inducing stresses therein. The holder includes first and second longitudinal support members with generally U-shaped cross sections for engaging the top and bottom surfaces of the slab. Each end of the slab is engaged by two cooperating support members which have surfaces for receiving the periphery of the face of the slab. Ears on the first and second support members mate with brackets on support members at either end of the slab.

Mass Transfer in a Laboratory Washing Machine

Abstract: Rinsing of loosened soil from textiles into an agitated bath is one of the essential steps in washing. This paper describes a rinsing model, its measurements, and further applications.A textile is an inhomogeneous porous medium. The liquid from the bath easily flows into the large pores. In these regions the soil is dispersed mainly by convection. The small pores are occupied by stagnant liquid. Consequently, the supply of detergents and the transport of loosened soil take place by diffusion. A piece of textile is therefore regarded as a porous slab having diffusion and convective regions. The length of each region depends on agitation, cloth/liquor ratio, textile porosity, and tem perature.Using the diffusion length as a characteristic parameter, the agitation and the influence of detergents in fabric cleaning can be investigated and optimized in washing machines of various types and dimen sions.

Thermoelastic analysis of laminated orthotropic slabs

Abstract: Stationary two-dimensional temperature, stress, and displacement distributions are investigated for a simply supported slab consisting of bonded orthotropic layers. The top and bottom faces of the slab are subject to arbitrary variations of temperature, heat flux, or convection, and arbitrary distributions of tractions. Displacement potentials are used to obtain the exact thermo-elasticity solution. For purposes of comparison, a strength-of-materials approximation for the temperature-induced stresses and middle-surface displacements is presented. As an illustrative example, the thermoelastic response to a sinusoidal distribution of temperature rise over the top face of the slab is computed; numerical results are given for laminates of various geometric configurations.

Source function expansion method for radiative transfer in a two-layer slab

Abstract: Radiative heat transfer in an isotropically scattering, absorbing and emitting two-layer slab with specularly reflecting boundaries is solved by expanding the source function by Legendre polynomials in the space variable in the integral form of the equation of radiative transfer The reflectivity and the transmissivity of the slab for an externally incident isotropic radiation are determined The S -1 solution yields results which are sufficiently accurate for most engineering applications

Prevention of cracking of continuously cast steel slabs containing boron

Abstract: Production of boron-containing steel slabs free from surface defects by continuous casting, particularly prevention of the slab surface crackings by cooling the slab with a specific cooling rate through the temperature range from the melting point to 900° C. so as to prevent boron-containing compounds such as BN from precipitating along the austenite grain boundary. Great advantage over the conventional art is that boron-containing molten steels which could not be continuously cast can be successfully continuously cast into slabs free from surface defects.

Strength of Composite Beams with Web Openings

Abstract: An ultimate strength analysis of composite beams with unreinforced, rectangular web openings is presented. The analysis is developed for general beam geometry and material properties, and for a single web opening of any practical depth, width and location. The beneficial effects of strain hardening and the shear contribution of the slab are neglected, and a four hinge failure mechanism at the opening is assumed. Analytical results indicate that a composite section with a web opening has a significantly higher bending strength than the corresponding noncomposite section, and that variations in opening length, height and eccentricity can have a significant effect on the ultimate strength. Comparison of the analytical results with the limited experimental data available indicates that the theory provides a very conservative estimate of the ultimate strength. The discrepancy between theory and test results is attributed primarily to strain hardening and the shear contribution of the slab.

Rotating disc splitter

Abstract: A method and apparatus for splitting wood slabs substantially along the wood grain into longitudinal-grain wood strands are provided. The apparatus comprises a rotating disc splitter having a pair of parallel rotary shafts each having centered thereon and secured thereto a series of spaced apart circular discs, means for counter rotating the shafts to pull a slab of wood between the series of discs and to split the slab into strands, and a series of floating spacer rings on each shaft interspaced between the discs, the floating spacer rings being positioned on either side of the shafts adapted to permit the spacer rings to move away from the discs when a slab is being split therebetween. The method comprises inserting an end of a slab of wood between counter rotating discs, a first series of discs pushing first sections of the slab in one direction perpendicular to the direction of travel of the slab and perpendicular to the axes of the counter rotating discs, a second series of discs interfitting with the first series of discs pushing second sections of the slab between the first sections in an opposite direction to the one direction thus causing splitting to occur between first sections and second sections of the slab and forming strands, and guiding the first sections and second sections of the slab downstream of the counter rotating discs to issue as substantially straight strands from the counter rotating discs.

Heating furnace controlling method

Abstract: PURPOSE:To smoothly cope with a residence time change due to cessation, etc. by accumulating slab temp. rising patterns from charging slabs into a heating furnace to extracting them in the form of the ratio of the time elapsed after charging and the predetermined residence time and by controlling the slab temp. according to the date. CONSTITUTION:When slabs 5 are heated in heating furnace 1, the temp. of the i-th zone is detected with slab temp. operator 7, and the temps. of all slabs 5 in the i-th zone are estimated according to the following equation: dtheta/dtau=K(T -theta ) wherein theta is slab temp., T is furnace temp., tau is time and K is a coefficient. Next the time elapsed after charging each slab 5 is measured with zero dimensional operator 11, and the time is divided by the predetermined residence time the of slab to calculate zero dimensional time. In accordance with this calculated time the slab temp. of the time is selected from slab temp. pattern accumulator 12 and compared to the output value of operator 7 to obtain the difference. This operation is performed with respect to all slabs 5 in the i-th zone to calculate the mean value of differences in temp. of the slabs, and the temp. of the i-th zone is changed according to the value.

Scattering and mode conversion of guided modes of a slab waveguide by a circular cylinder

Abstract: Using expansions of modes of the dielectric slab waveguide in terms of the cylindrical functions, the scattering and mode conversion of guided modes by a circular dielectric cylinder are analysed approximately; mode conversion coefficients, total scattering power, and scattering power patterns are obtained. Some representative numerical results are presented for the case of scattering by a circular cylinder located in the surrounding outer region.