Showing papers on "Slab published in 1975"

On the Relative Importance of the Driving Forces of Plate Motion

Abstract: Summary A number of possible mechanisms have recently been proposed for driving the motions of the lithospheric plates, such as pushing from mid-ocean ridges, pulling by downgoing slabs, suction toward trenches, and coupling of the plates to flow in the mantle. We advance a new observational method of testing these theories of the driving mechanism. Our basic approach is to solve the inverse problem of determining the relative strength of the plausible driving forces, given the observed motions and geometries of the lithospheric plates. Since the inertia of the plates is negligible, each plate must be in dynamic equilibrium, so that the sum of the torques acting on a plate must be zero. Thus, our problem is to determine the relative sizes of the forces that minimize the components of net torque on each plate. The results indicate that the forces acting on the downgoing slab control the velocity of the oceanic plates and are an order of magnitude stronger than any other force. Namely, all the oceanic plates attached to substantial amounts of downgoing slabs move with a ' terminal velocity ' at which the gravitational body force pulling the slabs downward is nearly balanced with the resistance acting on the slab; regardless of the other features of the trailing horizontal part of the plates. The drag on the bottom of the plates which resist motion is stronger under the continents than under the oceans.

Gravity Effect of Downgoing Lithospheric Slabs beneath Island Arcs

Abstract: Recent geophysical data from the northwestern Pacific suggest that the total gravity effect of a downgoing slab beneath island arcs is small and limited in extent to the region of the island arc and trench. The total effect is small either because the density contrast associated with the downgoing slab is small or because the slab is in some manner compensated. The small total effect suggests that it is not possible to obtain details of the configuration of the slab from gravity data alone. The small total effect also suggests that the large positive gravity anomaly associated with some island arcs from satellite data must originate from sources other than the downgoing slab.

Punching Shear Strength of Restrained Slabs

Abstract: The punching shear strength of restrained concrete slabs is investigated. A rational idealized model of a restrained slab at punching failure is developed. This model is an extension of one previously developed by Kinnunen and Nylander for simply supported slabs. The influence of boundary restraints on punching load is demonstrated and the model is shown to yield accurate estimates of the punching strength of slabs with known boundary restraints. An empirical factor, termed the restraint factor, is introduced to estimate the influence of boundary restraints and can be used in the design of slabs for which the actual restraints are not exactly known. The restraint factors for a number of restrained slab systems are reported.

The Distribution of Heating Potential Inside Lossy Spheres

Abstract: The distribution of the heating potential inside a lossy sphere having the same electrical characteristics as those of brain tissue was investigated in the frequency region of 10 MHz to 12 GHz. The conditions under which a potential hot spot appears inside the sphere and its shape were determined and were displayed in a radius vs. frequency diagram. The results show that hot spots appear inside only for spheres with radii 8 cm > R > 0.1 cm and only in the frequency range of 300 < f < 12,000 MHz. It was found that the heating potential is always non-uniformly distributed, and in cases where it was maximum inside the sphere it was larger by a factor of approximately ten to the values calculated by the plane slab or the average cross section model.

Bending losses of dielectric slab optical waveguide with double or multiple claddings: theory

Abstract: Bending-loss formulas of a multilayer planar optical waveguide are obtained on the basis of continuation of wave functions without solving the complicated eigenvalue equation. We then consider the bending losses of a doubly clad slab waveguide in which the core has the largest refractive index, and the inner cladding has the lowest. Bending losses are shown to be drastically reduced by inserting low-index inner claddings between the core and the outer cladding.

Solar-heated dwelling

Abstract: In a preferred embodiment of the invention, rotatably adjustable elongated cylindrical solar collector plate cells, rotatable around the elongated axis thereof for adjusting angle of incidence of exterior light rays from the sun to the surface of the collector plate, are mounted upon a roof with water flow therefrom being channelled below an insulated ceiling downwardly for alternate flow as between parallel flow paths alternately selectively to and through concrete slab conduits having copper tubing directing heated water therethrough, and the parallel flow conduits through a layer of rocks beneath the concrete slab, the concrete slab being a part of the floor structure of the dwelling and the layer of rocks being a reservoir sink therebeneath, flow being directed dependent upon differential temperature of the upper floor surface of the concrete slab, such that space within supporting wall room space defined between the ceiling and the floor is economically heated devoid of excessive room temperatures and with substantially level and constant ambient temperature ranges as desired and preset within the room space over extended periods of time for and throughout a heating season of the year, while being inoperative and non-functional when heat is not desired, and including further a hot-water heating provision embodied within an intermediate heat exchanger located between the solar cells fluid circuit and the concrete slab heating circuit, each circuit having its individual circulation pump controlled by its respective thermostat.

Propagation, Attenuation, and Dispersion Characteristics of Inhomogeneous Dielectric Slab Waveguides

Abstract: A numerical method based upon invariant imbedding and the transverse impedahce concept is applied to the problem of calculating various properties of inhomogeneous slab waveguides. The approach appears not only to be rapidly convergent but is also capable of giving arbitrary accuracy for any given mode. In particular, some interesting properties of a class of asymmetric profiles are pointed out, relating to discussions of lossy structures, temporal pulse distortion, and spatial broadening.

Slab gel electrophoresis apparatus

Abstract: Apparatus for vertical slab gel electrophoresis has upper and lower tanks having open tops. The tanks are supported in stepped relation to each other by a vertical support plate which forms a front wall of one tank and a rear wall of the other. At least part of the wall of the upper tank formed by the support plate has a top edge which is lower than the other top edges of the tank. A substantially open-ended chamber is formed by clamping a plastic plate to a glass plate with strip members between side edges of the plates. The plastic plate is held against the spport plate for reinforcing the rigidity of the plastic plate with the support plate. A portion of the top edge of the plastic plate is lower than the top edge of the glass plate and intermediate the lower edge portion of the wall of the upper tank formed by the support plate and the other top edges of the upper tank. Partitions extend across the chamber from the plastic plate to the glass plate and down into the chamber from the top, lower edge of the plastic plate at least to a slab of gel which fills the chamber to form wells over the gel for receiving samples. An electrolytic buffer solution is placed in both tanks, the solution in the upper tank flowing over the lower edges of the support plate and plastic plate to the glass plate to cover the samples in the wells. Opposite electric potentials of the appropriate polarity are then applied to electrodes in both tanks to cause the samples to migrate electrophoretically into the gel, the position of the samples in the gel then being an indication of the composition of the samples.

Foam glass structural element and method of producing

Abstract: Foam glass developed under vacuum is continuously formed into a slab while being cladded on its major sides and longitudinal edges with sheet metal. The metal claddings or facings for the two major sides of the slab are held under tension during the solidifying of the slab body. End plates are inserted transversely through the product at specified points during its movement and sections of the continuous product are cut to length, whereby the sections are prestressed partly as a result of compression along two axes caused by differing coefficients of expansion of the cladding and foam glass body and partly to atmospheric compression of the product on a third axis perpendicular to its major sides. Modified forms of the product eliminate the metal cladding or skin entirely or provide the same as a cast-on coating without mechanical prestressing.

Thermoelectric heating and cooling apparatus

Abstract: This invention pertains to an improved thermal slab assembly. A metal slab defines an exterior surface of the assembly and is supported on a hollow chassis. A plurality of thermoelectric devices are conductively engaged with the underside of the slab and are disposed in a regular array relative to each other, whereby each device is assigned a respective one of a corresponding plurality of equal area portions of the slab. Control means are coupled between the slab and the thermoelectric devices for sensing the temperature of the slab and for regulating operation of the devices to establish and maintain a predetermined temperature of the slab. A vertically and parallelly finned heat sink is conductively coupled to each thermoelectric device. Baffle means are located in the housing and are engaged between the chassis floor and the slab, and also with the heat sinks at the outer surfaces of the outer fins thereof and at the lower ends of the fins thereof, for dividing the housing interior into an inner chamber and an outer chamber. The baffle means cooperate with the heat sinks for defining ports between the inner and outer chambers only via the spaces between the fins of the heat sinks. An air flow opening is provided through the chassis to the inner chamber and an air flow opening is provided through the chassis to the outer chamber. A fan is associated with one of the openings for circulating air between the chambers through the ports. The control means includes means for adjusting the predetermined temperature to be established and maintained in the slab by the thermoelectric devices. The control means also includes means for reversing the direction of current flow through the thermoelectric devices so that the assembly may be operated either for heating or for cooling the slab.

Vertical gel slab electrophoresis apparatus and method

Abstract: A gel electrophoresis device in which the separating gel is cast in a vertical position between hydrophilic plates which form a gel slab chamber filled with a separating gel solution from the bottom for reducing fill turbulence allowing formation of a gel slab having a predetermined gradient. A removable seal is applied to the bottom of the gel slab chamber for containing the separating gel solution prior to polymerization. One gel slab chamber may be removably attached to each vertical side of a central temperature control chamber which is completely enclosed and which has an inlet and an outlet channel for circulation of temperature control fluid therethrough. An upper buffer chamber which opens upwardly is formed above the central temperature control chamber in communication with the top of the vertical gel slab chambers. The top of the gel slab is formed using a well forming implement made of polymerization inhibiting material so that the implement may be withdrawn after polymerization without altering the desired shape of the top of the vertical gel slab. The gel slab chambers attached to the central enclosed temperature control and upper buffer chamber are lowered into an outer chamber after polymerization of the separating gel solution and removal of the seals from the lower end of the gel slab chambers. The outer container is filled with a buffer solution in consequent directi contact with the lower end of the gel slabs, and the upper buffer chamber is filled with a buffer solution in direct contact with the top of the gel slabs. Samples are underlaid beneath the upper buffer solution atop the shaped upper surface of the gel slabs and a cover is placed on the outer container to contact a pair of electrodes which are in separate electrical contact with one of the upper and lower buffer chambers for applying a voltage therebetween, thereby causing electrophoretic separation of the sample within the gel slab.

Light concrete monolithic slab

Abstract: A monolithic slab manufactured from light, generally foamy concrete between two layers of reinforced concrete, having smooth, or alternatively corrugated, exterior surfaces, to suit the particular utilization requirements thereof.

Dominant Creep Mechanism and the Descending Lithosphere

Abstract: Summary The descending of the lithospheric slab into the asthenosphere is governed by gravitational body forces generated by thermal volume contraction and by phase boundary elevation in the colder slab. The dynamics of sinking depends on the rate controlling deformation mechanism in the lithospheric slab and in the adjacent mantle; it is a function of the thermal conditions, the state of shear stress, the grain size, and the elastic moduli. A finite element initial strain, incremental procedure has been used to model the sinking of the lithospheric slab into the asthenosphere. Both diffusional flow and power law creep have been incorporated as dominant deformation mechanisms separately. Computed principal stresses and maximum shear stresses are in good agreement with observations of seismicity and focal mechanisms in those models which involved power law creep mechanisms with a power of n= 3. Similarly, computed creep displacements and velocities support the view that the power law creep mechanism is the dominant mechanism in the mantle region of slab subduction. The resistance of the mantle to a slab sinking with a velocity of 8 cm/yr requires a stress-strain rate equation equivalent to the one based on experimental and theoretical results, involving constants, however, which render strain rates five orders of magnitude smaller than those in experiments. A corresponding strain rate map of the upper mantle based on the computed shear stress suggests a maximum rate of 3 × 10−14s−1 in the asthenosphere and an average rate of 10−19s−1 in the mesosphere, both taken at 100 bars shear stress. Translation into effective viscosities leads to a reasonable agreement with viscosities derived from glacio-isostatic rebound data.

Geometry and lateral strain of subducted plates in island arcs

Abstract: Oceanic trenches associated with island arcs generally have small radii of curvature, much less than 45 degrees. A geometric model of subduction is presented that predicts three types of arcs: one in which the subducted plate is subject to lateral extension, a second in which the subducted plate is laterally shortened, and a third in which the subducted plate is not laterally deformed. Parameters of the model are the radius of curvature of the island arc and the dip of the subducted plate. Comparison of island arcs with the model suggests that, at intermediate and deep levels of subduction, most arcs are of the type in which the subducted plate is laterally extended.

Prefabricated structural elements, and box-shaped building sections formed from such elements

Abstract: A structural element constituting a panel for a floor, wall or roof of a space defining elongated box-shaped prefabricated section which includes a rectangular concrete slab with a peripheral rectangular frame of beams. A reinforcement network is attached to the frame beams. With I-beams constituting the frame beams, one side of an upper flange is cast within the slab, such flange being connected to the reinforcement network. Recesses are provided at the corners of the slab to receive upright extensions affixed to the top of the upper flanges of the I-beams, such extensions being adapted to receive for attachment columns or other components of the section. The recess provided for the extensions may be spaced therefrom and being filled in with a concrete or other plastic type material when the further component is received on the extension. The extension may extend above the slab without a recess. A covering material may be applied to the top of the slab and folded over its edges. An L-shaped edge piece may be connected to the slab at its upper edges, the vertical leg of the edge piece extending to the exposed edges of the upper flanges of the I-beam and the horizontal leg of the edge piece extending inwardly and being flush with the top surface of the slab. An angle piece member may be connected to the slab at its edges so it is received on top of the upper flange of the I-beam and its vertical portion extends upwardly from the exposed edges of the upper flanges of the I-beam. A further alternative is to furnish a wooden border member with its top flush with the top surface of the slab. Another alternative is to place a wooden beam on top of the slab which is rigidly connected to the I-beam, such wooden beam having a wall affixed thereto. Further, transverse I-beams may be connected to the web and lower flanges of the I-beam spaced below the slab to provide increased rigidity. The same structure is disclosed with channel beams. A wooden frame is disclosed wherein the frame beams are made up of two frame parts connected side-by-side with the outer frame part higher than the inner frame part and the slab received so as to be coplanar with the upper edge of the inner frame part, such upper edge being utilized to secure the reinforcement network. Transverse beams are located between the two longer sides which are the same height as the inner frame part so as to be received in the slab at the level of the reinforcement and beams in place is disclosed as well as a method for utilizing such jig apparatus.

Slab gel dryer and method

Abstract: An apparatus for drying slab gels having a metal platen with electrical strip heaters mounted on one side thereof and a depression formed in the other side which serves as a drying chamber. The slab gel is laid on a sheet of porous filter paper over which is laid a sheet of non-porous material having non-adhesive qualities relative to the slab gel. The mounted and covered slab gel is placed in the depression and a compliant cover sheet is placed over the top of the depression overlapping the platen around the periphery of the depression. An open passage is formed through one edge of the platen in communication with the depression therein. The strip heaters are connected to an electrical power source and the open passage is connected to a vacuum source. The pressure in the depression is reduced relative to ambient pressure causing the compliant cover to be forced against the platen around the periphery of the depression for sealing the drying chamber. Moisture vaporized from the slab gel is removed through the open passage. A thermostat may be used to control the temperature of the platen and a timer may be used to provide for a predetermined period of heating and evacuation of the drying chamber. A temperature sensor may be placed in intimate contact with the slab gel for producing a signal to a relay for interrupting heater power when slab gel temperature rises through a predetermined temperature after substantially all of the moisture content has been vaporized from the slab gel.

Plastic concrete slab curtain wall system - with undercut-edged slab groove engaging stem of diverging-armed carrier batten

Abstract: The system of assembled building slabs incorporates two anchorages for each slab, one at least being in the form of a carrier batten engaging in a groove in the slab and attached to carrier anchoring elements fixed on the anchoring base, esp. for use in curtain walling systems with an insulating layer as in 2355803. Form-locking engagement between slab and carrier batten is achieved by providing a groove in the slab which is bounded by undercut sidewalls; and arms on the batten, running at an angle diverging from each other, these being connected by a stem which engages in the groove. Each of the diverging arms may be accommodated by a groove in the slab, the grooves running into the slab on diverging lines. Secure form-locked fixtures is achieved.

Ballastless permanent way for railway vehicles - has prefabricated concrete supports which rest after alignment on hardenable filling

Abstract: The ballastless railway track support structure is built up from prefabricated concrete components, all aligned by a simple process before final fixing The building process can be automatic The foundation consists of lightweight concrete with added foamed polystyrene The prefabricated slab is placed on this substrate and aligned The gap formed is filled by injection with a hardenable compound and the aligned slab is hence stable Slabs are connected with dowels to form a continuous support The rail is held on a saddle and this saddle forms a mould for plastics container mortar layer used for aligning rail The rail rests on damping pads and it is clamped by bolts to the slab

Minimum Cost Selection of One-Way Slab Thickness

Abstract: Considerable cost savings can result from the design of one-way reinforced concrete slabs, beams of constant width, and footings based on cost minimization techniques of flexural capacity. Equations for minimum cost slab depth are developed and a simple iterative method of their solution is presented. Resulting slab costs are compared, one using the minimum cost procedure, the other based on minimum slab thickness requiring no deflection check. The minimum cost slab usually requires a deflection check except where steel is expensive relative to concrete or for intense design loads.

Propagation of electromagnetic waves in a nonlinear dielectric slab

Abstract: The early phases of propagation of a large amplitude electromagnetic disturbance in a nonlinear dielectric slab embedded between two linear media are investigated by the method of characteristics. This disturbance is triggered by the arrival of an electromagnetic shock wave at one of the interfaces. Reflection and transmission of an arbitrary signal when it arrives at one of the slab boundaries is characterized in terms of nonlinear reflection and transmission coefficients for the interface. No restrictions are placed on the form of the constitutive laws of the material comprising the slab.

Deck structure and connector for building construction

Abstract: An improved deck structure and connector for construction of demountable structures such as a parking building as well as permanent structures such as a high rise office or apartment building, comprising connectors spaced along the edges of a concrete slab for attaching the slab to an underlying beam Each connector includes an upright bushing embedded in the slab for receiving a removable lifting bolt which expands to engage the inside walls of the bushing to lift the slab into location on the beam The portion of the bushing engaged by the expandable lifting bolt is preferably tapered upwardly between a horizontal mounting plate which rests on top of the beam and an anchor rod extending laterally from the bushing into the slab The lifting bolt can be released and removed allowing same bushing to receive a fastener bolt An alternative embodiment provides a downward vertical flange on the connector for welding to an edge of the beam

Load bearing reinforced ground slab

Abstract: A reinforced horizontal slab having high bearing strength is created on the surface of the ground by initially forming a plurality of discrete vertically elongated reinforced zones in situ in the ground with their tops adjacent ground level and then covering the ground over and between the zones with a surfacing material constituting a slab that rests on the tops of said zones and on the ground therebetween Each zone is a downwardly tapered concrete column having at least one vertically oriented reinforcing metal bar embedded therein The zones are formed by a method which entails vibratorily vertically sinking a tapered hollow elongated mandrel into the ground at each zone location, vertically extracting the mandrel to leave a tapered vertical hole in the ground, filling the hole with concrete, vibratorily reinserting the hollow mandrel with a reinforcing metal bar therein and having its lower end laterally protruding from the mandrel tip, so that the concrete is expanded into the soil adjacent to the hole and the bar is vertically emplaced in the hole, vibratorily extracting the mandrel from the hole while leaving the rod in the concrete, and then allowing the concrete to set in the hole The slab is poured on the ground surface over the tops of the columns, the slab being reinforced with a mat or reinforcing bars

Marine vessel with vertical annular walls

Abstract: A marine vessel for storage or transport of cargo employing a honeycomb sandwich panel system of concrete construction applied to open or closed deck vessels comprising a plurality of vertically extending annular walls formed monolithically with the hull of the vessel in which the vertical annular walls may extend from the bottom deck or slab to the top deck or slab or between either the top or bottom and an intermediate deck or slab with the annular walls defining a plurality of compartments and serving as vertical shear walls which strengthen the structure to withstand stresses caused by wave action and the like in both longitudinal and transverse directions.