Showing papers on "Slab published in 1979"

Geometry of Subducted Slabs Related to San Andreas Transform

Abstract: Development of the San Andreas transform by rise-trench encounter in coastal California influenced the structural evolution of a large region within the adjacent continent. Continuation of arc magmatism and tectonism depends upon the presence of a subducted slab of lithosphere at depth beneath an arc-trench system. The lack of subduction at the transform plate boundary along the California continental margin led to the growth of a slab-free region beneath the part of the continental block adjacent to the San Andreas transform. Geometric analysis based on ideal assumptions predicts that generation of a lengthening transform by rise-trench encounter will also generate an expanding triangular hole or window in the slab of lithosphere subducted beneath the continent. One leg of the slab-window is the adjacent transform, but the orientations and lengths of the other two legs depend upon the relative motions of the three plates involved. By inference, arc volcanism and tectonism cannot persist across the no-sla...

Shear fracture precipitated by strain softening as a mechanism of dry slab avalanche release

Abstract: Snow stratigraphy studies at the fracture lines of dry slab avalanches often indicate a situation that consists of a harder thick layer overlying a thin weak layer. Prefracture stress conditions and progressive fracture of snow slabs are discussed here from the point of view that slow shear failure in the weak layer results in Griffith-like critical lengths there, resulting in rapid shear fracture and subsequent avalanche release. The important aspects of the timing of dry slab avalanche release and the relationship between the applied shear stress and the shear strength at the weak layer are discussed in this context. The results show that the main experimental facts on snow and field observations of snow slab avalanches are explainable from this approach, although direct, concrete proof is not presently available.

The double seismic zone in downgoing slabs and the viscosity of the mesosphere

Abstract: The seismic zone beneath several island arcs between about 100 and 200 km depth consists of an upper zone having down-dip compression and a lower zone having down-dip tension. Several numerical models of the Aleutian arc were computed to test the hypothesis that these double seismic zones are due to sagging of the slab under its own weight. This sagging occurs because the asthenosphere (between about 100 and 200 km) provides little support or resistance to the slab, which is supported from below by the more viscous mesosphere and from above by the lithosphere. The viscosity of the mesosphere was constrained to the interval between 0.25 x 10 to the 22nd and 0.5 x 10 to the 22nd P by noting that the slab would have mainly down-dip compression at higher viscosities and mainly down-dip tension at lower viscosities. The deviatoric stress in the slab and the fault plane between the slab and the island arc is about 200-300 bars (expressed as shear stress). The models were calibrated to the observed depth and gravity anomalies in the trench.

Single‐polarization optical fibers: Slab model

Abstract: Calculations for a simple three‐layer slab model show that sufficient anisotropic strain birefringence can be introduced into germanosilicate, phosphosilicate, and borosilicate single‐mode fibers to reduce the coupling between orthogonally polarized modes to a level of practical interest for single‐mode single‐polarization propagation.

P- and S-wave velocity anomalies associated with the subducting lithosphere determined from travel-time residuals in the Japan region

Abstract: Travel-time residuals of P and S waves from local deep earthquakes are used to apply geophysical constraints to the laterally heterogeneous structure associated with the Japan subduction zone. Theoretical residuals for two-dimensional upper mantle models that have high-velocity dipping slabs are calculated by applying Jacob's (1970) ray-tracing method. The forms of the spatial distribution of the observed and the calculated residuals are matched to determine the velocity contrasts across the asthenosphere and the subducting lithosphere boundary and a possible velocity structure inside the slab. We find 5 ± 1 per cent for Vp contrast and 7 ± 2 per cent for Vs contrast. These contrasts cannot simply be explained by a temperature effect alone and it is likely that other mechanisms such as partial melting in the asthenosphere are required for the observed velocity change. The data indicate that the subducting lithosphere can be modeled by a two-layer structure similar to that found for oceanic lithosphere (Shimamura and Asada, 1976) but with a smaller velocity contrast. Two-layer model calculations show that the subducting lithosphere is about 120 km thick. The upper layer of the slab is about 40 to 50 km thick and has about 1 per cent lower velocity than the underlying layer.

An approximate formula for describing dispersion properties of optical dielectric slab and fiber waveguides

Abstract: A systematic and analytic approach is made to approximate dispersion properties of dielectric three-layered slab and rod waveguides. The explicit formula obtained yields errors less than 1% except very near the cutoff frequencies of guided modes. The errors diminish rapidly as the normalized frequency increases. The formula has the same expression for slab and fiber waveguides.

Thermal insulation for buildings

Abstract: When masonry or wooden walls are insulated with hard-foam-slab insulation covered with plaster or mortar, reinforcement of the plaster or mortar can be omitted without incurring cracking if (a) the slabs are grooved, (b) the size and number of slab grooves have defined minimal values, depending on slab thickness, (c) the slabs have a residual shrinkage of at least 0.1 percent, (d) the plaster or mortar has a maximum plastic-resin content of 2.5 percent by weight and (e) the slab weight per cubic meter is, optionally, less than 20 kg per cubic meter.

Comparison of local and nonlocal theories of the collisional drift instability

Abstract: Two nonlocal cylindrical models of the collisional drift instability of a weakly ionized plasma are solved numerically and compared with the local slab model. It is shown that the local slab is inadequate in describing how mode stability varies with azimuthal mode number.

Realistic Vlasov slab equilibria with magnetic shear

Abstract: A method is described for generating exact Vlasov slab equilibria to model high‐beta plasmas with strong magnetic shear. Physically reasonable distribution functions that account for such effects as end losses and density gradients are constructed from constants of the motion and used to calculate the self‐consistent electrostatic and magnetic fields. As an application, numerically calculated equilibria modeling a tormac sheath are presented.

Method for controlling furnace temperature of multi-zone heating furnace

Abstract: A method for controlling furnace temperatures of a multi-zone heating furnace having a feedback control system for detecting and inputting a furnace temperature and a furnace temperature setting device or a combustion control computer of the type for determining an optimum furnace temperature for each slab and outputting it as a set point to said feedback control system, the method comprising the steps of determining, under predetermined limit conditions which are required for the operations of the furnace, a furnace temperature pattern or a slab temperature rise curve which may minimize the overall flow rate of fuel, heating the furnace along the furnace temperature pattern or the slab temperature rise curve which is determined, reducing, in response to the instruction for suspending the discharge of slabs from the furnace, the flow rate of fuel to be supplied to the furnace to a predetermined level, and heating the furnace along a new slab temperature rise curve which is obtained by shifting the steady state slab temperature rise curve by a slab discharge suspension period, thereby making the slab temperature when the slab discharge is resumed equal to the slab temperature when the slab discharge suspension instruction is received.

An Iterative Solution for Anisotropic Radiative Transfer in a Slab

Abstract: An iterative method is applied to solve the integral form of the equation of radiative transfer for the cases of isotropic scattering, highly forward, and backward anisotropic scattering in plane-parallel slab with reflecting boundaries. Calculations are performed for the values of single scattering albedo from ω = 0.7 to 1.0 where the convergence was previously reported to be poor. It is found that the convergence is significantly improved for most cases if the P-1 approximation of the spherical harmonics method is used for the initial guess. Results are presented for the hemispherical reflectivity and transmissivity of the slab over a wide range of parameters.

Exact solutions for TM modes in graded index slab waveguides

Abstract: Three continuous profiles for the dielectric constant are derived, which allow exact solutions of the vector wave equation, including all terms in the gradient of the profile, for both TE and TM modes on slab waveguides. The dielectric constant has been assumed to be a scalar quantity; i.e., the medium is isotropic.

Method of and apparatus for continuously rolling steel slabs

Abstract: A method of and apparatus for continuously hot rolling steel slabs. Separate pieces of steel slabs are continuously fed from a slab yard and delivered to a carriage which is adapted to move reciprocatingly along the line of path of the steel slab pieces. The carriage carries a welder which can move transversely of the path of the slab pieces, and also clamp devices for clamping preceding and succeeding slabs to fix them to the carriage, as means for keeping the preceding and succeeding slab pieces in abutting condition. As a steel strip including a plurality of slab pieces welded together is moved at a predetermined rolling speed into a rolling mill, the carriage moves substantially at the same speed to keep the succeeding slab in abutment with the trailing end of the last slab piece of the steel strip, to permit the welder to weld these slab pieces at their abutting end. This welding is performed only over a part of the cross-sectional area of these slab pieces. The steel slabs are thus welded together into continuous form, delivered to the rolling mill and rolled by the latter. This system ensures a higher yield of products and permits a full continuous hot rolling of the steel slabs.

Concrete floor slab constructed from basic prefabricated slabs

Abstract: A concrete floor slab constructed from several basic prefabricated slabs. This slab comprises at least three basic slabs 1, 2 and 3 of polygonal shape, set together and arranged around a central point, with at least three anchoring units located at the central point each at least partially embedded in a basic slab, a central junction component located at the central point between the basic slabs and mechanical assembly methods for the central junction component linking it with the anchoring units. The invention applies to the construction of all types of load bearing floors and in particular those of wide span which rest directly on pillars without the intermediate use of joists.

Barbecue grill slab

Abstract: A molded refractory slab for positioning in a barbecue grill between the burner unit and the heat-supporting grate has a plurality of uniformly spaced bosses simulating coals projecting upwardly from its top surface and integral dam means connecting adjacent bosses near the periphery of the slab to form a parapet for containing grease and rendered meat juices on the slab and preventing their dripping off the sides of the slab into the fire. The mold in which the slab is formed is of light-weight disposable material and is used as a protective container for shipping unfired slabs, which can then be fired during initial use of the slabs in barbecue grills.

A magnetostatic theory of the response functions for a finite-thickness ferromagnetic slab and the application to Brillouin scattering

Abstract: Calculations are given for the spin-dependent response functions (or Green functions) of a finite-thickness ferromagnetic slab using magnetostatic theory. The results are employed to obtain expressions for the integrated intensities for Brillouin scattering from the surface (magnetostatic) modes and bulk spin-wave modes of a ferromagnetic slab. Numerical estimates are made to compare the theory with recent experimental measurements for Fe and EuO, and it is found that many of the experimental observations can be satisfactorily explained.

Self‐similar power‐driven expansion into vacuum

Abstract: Planar, power‐driven expansion into a vacuum is found to be self‐similar for a power‐law driving source for the two ideal cases of a thick slab and a thin foil. For the thick slab expansion, an asymptotic solution for the far‐blowoff region is obtained and a numerical solution is present for the rest of the expansion wave. For the thin foil expansion, an analytical solution is obtained. In both cases, the solutions exhibit an unbounded flow field with velocities tending to infinity as a consequence of the continuum assumption, a finite temperature limit for the far‐blowoff material, and density profiles that decrease as a Gaussian in the far expanded material.

Matrix recovery electrophoresis apparatus

Abstract: Electrophoresis apparatus including a cooperating gel slab and matrix member. The matrix member has a first surface in generally surface-to-surface contact with the gel and is positioned overlying the gel. The matrix member has a plurality of openings therein which cooperate with the gel member to define a series of upwardly open wells. Electrode means pass through the wells. A reservoir for providing buffer solution to the gel is provided in underlying relationship with respect to the matrix member-gel slab assembly. The matrix member-gel slab assembly are urged into intimate contact. In a preferred form, integrally formed channel means cooperate with the underlying slab and a pump to establish a vacuum which serves to urge the matrix member-gel slab into intimate contact. The reservoir may have a support bracket for securing the matrix member-gel slab in overlying relationship to a buffer solution containing trough so that the matrix member-gel slab is maintained in generally horizontal position. In this fashion the material to be separated, such as proteins, migrates upward from inside the gel into the overlying wells. A plurality of molecules separated previously as by a standard slap gel system, for example, are eluted into separate wells.

Continuous casting device

Abstract: PURPOSE:To enable the broad slab of a thin thickness to be cast at a high speed economically by delineating the casting area by a pair of curved stationary side plates and a pair of movable strip-form bodies moving synchronously with the slab and providing a supporting and cooling device of strip-form bodies. CONSTITUTION:The casting area is delineated by a pair of stationary plates 30, 31 of mutually opposing curved form forming the short side wall faces of a slab 28 and a pair of movable strip-form bodies 4, 5 sandwiching the above-mentioned stationary plates 30, 31 along the curved faces and moving in synchronization with the slab 28. The strip-form bodies 4, 5 are the endless belts which are respectively stretched by rollers 6-11 and whose backs are supported and cooled by the static pressure bearing devices 14, 15, provided with water chambers 16, 17 and multiple nozzles 20, 21 in the inside. The above-mentioned constitution makes possible the high-speed casting of the thin-thickness and broad-width slab from the difficult-to- solidify moten steel and considerably reduces the equipment cost and maintenance cost before and behind the casting to be aligned.

Precast concrete joist system

Abstract: An improved concrete slab and steel construction wherein a pan is extended between adjacent joists, said pan having a bend line axially along its length, a portion of said pan resting a joist, a second portion being transversely notched such that said pan straddles adjacent joists at said notches, said pan serving to support poured in place concrete such that said concrete haunches down to supporting beams, thereby forming a composite concrete slab and steel structure.

Furnace temperature control

Abstract: In controlling a slab reheat furnace, the average temperature of each slab in a zone, is predicted as a function of the radiation heat source temperature in the zone, and the thermal properties, dimensions, location, velocity, and past thermal history of the slabs. The predicted slab temperatures are compared with a range of desired slab temperatures and the slab requiring the greatest time to be heated to its desired temperature is identified. The furnace is controlled in such a manner that the identified slab will be heated to the desired temperature. Slabs likely to be overheated are identified and, if a predetermined temperature limit is to be exceeded, the furnace is controlled to prevent further heating of the slabs. Gas temperatures throughout the zone are predicted based upon only one sensed temperature in the zone.

Scattering of surface waves at a slab waveguide discontinuity

Abstract: The analysis of a step discontinuity of single-mode slab waveguide excited in the dominant mode is presented for both TE- and TM-modes. The problem is formulated by using the mode-matching procedure parallel to that of Marcuse. The solutions for the reflection coefficient, transmitted power and radiated power are then obtained by the application of the residue-calculus technique, which leads to more general expressions than those so far obtained by others who used more complicated methods. Numerical results are given which are in good agreement with previous results for specific cases. For the general case, the results also agree very well with those obtained by the reciprocity theorem.

Concrete slab surface finishing apparatus

Abstract: A support frame to span and to be moved over the surface of a concrete slab on wheels running on rails extending along side edges of the slap, and having a hopper for depositing a layer of finishing material on the slab surface ahead of at least one roller carried by the frame, said finishing material being confined on the surface by side walls depending from the frame and overlapping the side edges of the slab. Power means rotates the roller, and this roller can be adjusted vertically relative to the frame to adjust the thickness of finishing material being rolled onto the slab surface.

Optical Characterization of Semiconductors

Abstract: Most samples are in the form of a slab or a thin film on a slab. We first review the optical properties of such samples described only by a complex index of refraction n = (n + ik). Later, we will determine the origin of n and k in a semiconductor so that we may characterize it in terms of free-carrier density, mobility, donor and acceptor densities, alloy homogeneity, etc.