Showing papers on "Slab published in 1973"

TE modes of graded-index slab waveguides

Abstract: An analysis of the TE modes of a slab waveguide with graded refractive-index distribution is presented. The refractive index is approximated by a piecewise-linear distribution for which exact solutions of the guided-wave problem can be obtained. For multimode guides, useful approximate solutions can be worked out with the help of the Wentzel-Kramers-Brillouin (WKB) approximation. A formula is given for the total number of guided TE modes supported by the waveguide. The coupling efficiency of a prism coupler is investigated by studying the radiation losses of the guided modes escaping from the waveguide through the coupling prism. It is found that the radiation losses of the modes of the graded-index waveguide are more nearly constant than those of the asymmetric slab waveguide.

Coupling coefficients for imperfect asymmetric slab waveguides

Abstract: This paper presents a collection of formulas that are necessary for the treatment of radiation and mode conversion phenomena of imperfect asymmetric slab waveguides. The coupled mode theory of dielectric waveguides is briefly reviewed, and general expressions for the coupling coefficients are given. The field expression of the guided and the radiation TE and TM modes of the asymmetric slab waveguide are stated, and are used to derive formulas for the coupling coefficient for slight core boundary irregularities.

Convergence of the discrete-ordinates method for anisotropically scattering multiplying particles in a subcritical slab*

Abstract: For steady state transport of particles in a subcritical slab, it is shown that the continuous-space discrete-ordinates approximation converges to the exact solution. This result is established for a spatially inhomogeneous slab and for a general class of scattering laws and quadrature rules.

Probability density function and moments of the field in a slab of one‐dimensional random medium

Abstract: The problem of a plane wave normally incident on a slab of one‐dimensional random medium is studied. The refractive index variations of the random medium are taken to be a stationary Gaussian‐Markov process. By employing an invariant imbedding technique and by using the Markov property of the refractive index variations, two cascaded diffusion equations are obtained for the probability density function of the reflection coefficient and the field in the slab. These equations are then solved approximately for small refractive index fluctuations and an expression is obtained for mean intensity in the slab interior.

On the Observability and Stability of the Temperature Distribution in a Composite Heat Conductor

Abstract: An infinite slab of finite thickness is composed of two given homogeneous isotropic slab heat conductors whose thermal properties are constants. Assuming that temperature conditions uniform in the space variables are applied and maintained at the boundaries, the problem of the observability of the temperature distribution inside from the boundary temperatures and the temperature at the interface of the two different materials is considered. Continuous dependence of the temperature distribution upon the data is studied.

Ionospheric slab thickness: Its relation to temperature and dynamics

Abstract: Summary. The relationship between the ionospheric slab thickness and the temperature and dynamic processes in the ionosphere has been examined. It has been found that the slab thickness is a poor indicator of the temperature or of Te/Ti. Nevertheless, some new expressions relating τ to Hp, Hn, and Te/Ti are presented. Evidence is presented to show that the departures of τ from the values dictated by τ = 4.13Hn are strongly correlated with the departure from diffusive equilibrium as measured by the index (D/Hn² - β).

Performance of precast prestressed hollow core slab with composite concrete topping

Abstract: This load test of a machine-made hollow-core slab with composite topping verified a number of accepted industry design and fabrication practices, specifically the following: 1. Impact test hammer data taken on the side of the member provided an accurate assessment of concrete strength as determined by uncracked deflection behavior and ultimate moment capacity. 2. The observed ultimate moment was about 10 percent greater than calculations based on Eq.(18-3) in ACI 318-71 but nearly identical to calculations based on strain compatibility by Fig. 5.2.5 in the PCI Design Handbook. 3. The bilinear concept for predicting the deflection of cracked prestressed members was conservative well beyond a nominal bottom fiber tensile stress of 12i,/ f'c. 4. Composite action between the precast and cast-in place portions was evident up to ultimate load. The top surface of the precast slab was a smooth, even, machine cast finish and did not comply with Section 17.7 of ACI 318-71. There was no reinforcing steel projecting from the precast slab into the topping concrete. 5. A shear failure did not occur even though the ultimate shear stress vu was 1.75 times vc as computed in accordance with ACI 318-71.

Study of the Injection Upsetting of Metals

Abstract: The punch pressure required to injection upset a cylindrical billet of an isotropic, non-work-hardening, rigid–plastic material is derived using an upper bound (velocity field) technique and by a ‘slab’ stress analysis. A method for applying the theory to the injection upsetting of work-hardening materials is evolved and the validity of this application is demonstrated by the results of experiments using pure aluminium, an aluminium alloy and copper.

Soft Surface Phonons and Surface Reconstruction

Abstract: We propose a new mechanism which can lead to reconstruction in the surface region of a large class of materials. The mechanism is based on the fact that the dynamic effective charges present on the atoms near the surface can be different from those on the atoms in the bulk. The long-range interaction of these charges can cause the surface phonon to be lowered in frequency. We present numerical calculations of the normal-mode frequencies of a simple-cubic monatomic slab [(001) faces] of 15 layers when surface-induced dynamic effective charges are present near one of the surfaces. For reasonable values of the short-range atomic force constants, and for values of the dynamic effective charge on the surface layer of the order of 0.5e, the surface is unstable and recontruction occurs. Various patterns of reconstruction can be obtained depending upon the values of the short-range force constants.

Tests of Curved Steel-Concrete Composite Beams

Abstract: Four curved composite beams, each consisting of a steel beam with a reinforced concrete slab, were fabricated and tested. The tests were limited to single girders on a simple span. The concrete slab was attached to the top flange of the steel girders using 1/2-in. (12.7 mm) diam stud shear connectors. The main variables in the test program were the girder size, radius of curvature, loading, and the number of connectors at a section. All four beams were loaded to failure and the vertical deflection, strain, rotation, and slip (between the steel and concrete) were recorded at several locations along the length of the span. Two of the beams failed in torsion near the supports and two failed in combined bending and torsion near midspan. Observations concerning the agreement between theory and experiment are presented for the loads causing failure, and stresses and deflections at one-half the failure loads. The significance of the test results regarding the design of the shear connection is examined and a simplified method of design of headed shear connectors is presented.

Reflection and transmission of radio waves at a dielectric slab with variable permittivity

Abstract: Expressions for the reflection and the transmission power coefficients are derived for the case where a plane wave is obliquely incident on a dielectric slab in which the relative permittivity decreases symmetrically according to a 1/z^{2} law from a given maximum value at the plane of symmetry and tends towards unity at the two faces of the slab. The effect of the curvature and other parameters governing the inverse square profile on the transparency property of the material at radar frequencies has been studied within a large d/\lambda range where d is the half-slab thickness and \lambda the wavelength of the incident wave.

Sensing mechanism for slicing machine control system

Abstract: A mechanism for sensing the cross-sectional area of a slab of a food product during processing, as in a slicing machine where the slab is cut into drafts of predetermined weight. As the slab is advanced into the slicing blade, sensing fingers ride on the top and one side surface of the slab and respond to changes in the thickness and the width of the slab. The mechanism through a multiplier coupling provides a mechanical output indicative of the product of the thickness and the width, and is employed to drive the rotor of a step switch which, in conjunction with digital circuitry, serves to convert the mechanical output into a slice number signal for use by the electrical control apparatus of the slicing machine.

Method of soil treatment

Abstract: A network of interconnected rigid or collapsible perforated pipes are installed below ground, such as before the erection of a wood containing structure, and an inlet pipe extends from the network to an accessible point. A solution or emulsion of a termicide is pumped under pressure through the inlet pipes and pipe network to impregnate the ground underlying or around the structure, when required, to inhibit termite growth and destroy any termite colonies. As an alternative, in slab on ground construction, the slab is provided at accessible points with suitably spaced openings providing communication with the ground, the openings being closed by removable plugs.

Reflection and transmission of electromagnetic waves obliquely incident on a relativistically moving uniaxial plasma slab

Abstract: The reflection and transmission properties of electromagnetic waves obliquely incident on a relativistically moving uniaxial plasma slab are investigated theoretically and the maxima and minima of the power reflection coefficient as a function of the normalized incident wave frequency ( \Omega ) and the slab velocity ( \beta ) are discussed for slab motion parallel as well as normal to the slab boundaries. One can predict the nature of variation of the reflection coefficient with respect to any parameter from the variation of q' (the root of the dispersion equation) with that parameter. When q' is real and varies rapidly, the oscillations in the reflection coefficient are rapid and when q' differs significantly from the free-space value, the amplitude will be large. In the imaginary range of q' , the reflection coefficient is nonoscillatory. The discussion of the results is facilitated by introducing a parameter p which is a quadratic in \beta . For slab motion parallel to the interface, the two slab velocities for a given p give rise to same reflection coefficient whilst for normal motion the results are significantly different.

Outdoor pool table

Abstract: An outdoor pool table resistant to weather. A concrete slab is mounted atop a rectangular shelf of a metal frame and supported by a plurality of sheet metal legs. The concrete slab includes a depending bracket embedded therein, which bracket abuts against a vertical wall of the rectangular shelf to provide for the mounting of the slab on the shelf. A plurality of concrete bumper supports are mounted atop the slab and extend peripherally therearound. Bumper pads are mounted to and inwardly of the supports. A plurality of pool ball receiving pockets are mounted to the supports adjacent the slab.

Reflection and transmission of electromagnetic waves obliquely incident on a relativistically moving isotropic plasma slab

Abstract: The oscillations in the power reflection coefficient as a function of the normalized incident wave frequency and slab velocity are shown for electromagnetic waves obliquely incident on an isotropic plasma slab relativistically moving along the slab interface. Both parallel and perpendicular polarizations of the wave are considered.

Method of stripping slab casting forms

Abstract: A method for stripping slab casting forms from cured concrete slabs by flexing the forms to allow grout keyway forming protrusions projecting inwardly from the form side walls to clear the associated grout keyways formed in the slab. By applying stripping forces to the form in a particular manner a more satisfactory grout keyway, from a structural view point, can be formed in the slab while still permitting the form to be stripped from the slab by flexing without exceeding the elastic limit of the material, such as steel, of which the bottom pan of the form is constructed.

Laminated padlock body with incorporated band-forming slab

Abstract: The major portion of the padlock body is formed of metallic laminations but a section of the padlock body in juxtaposition to a series of laminations is completed by a band-forming slab which projects slightly outwardly of the surfaces of the laminations to provide an annular bumper which may also carry identifying indicia. Portions of the slab are formed with openings cooperating with contiguous openings in the laminated portion of the padlock body to accommodate components of the padlock mechanism.

Bridge construction using precast curb and edge beam

Abstract: A high type bridge construction produced with a minimum field forming. By utilizing precast elements for the supporting substructure as well as for the interior and exterior beams the field forming is eliminated for these items. The exterior beam is precast with the curbing and includes a dap to receive the edge beam which is also precast and assembled to the dap. The edge beam is cast low enough so that it stops surfaces below the top of the poured slab allowing the slab to be continuous to its end. Angles are secured to the top of the precast edge beam to serve as the end form of the slab. The precast exterior and interior beams include a longitudinal edge which supports a metal form and which is held in place.

Convection in a vertical porous slab

Abstract: It is shown that the basic flow of the fluid saturating a vertical porous slab, whose walls are maintained at constant, but different, temperatures, is asymptotically stable in the mean against disturbances of arbitrary amplitude, when the Rayleigh number is smaller than 4π2.

Construction panel having overlapping edges and foam backing

Abstract: A prefabricated panel of substantially uniform width and thickness comprising a foamed sheet or slab of a plastic material, and a rigid facing sheet bonded to one surface of the foamed slab, the facing sheet extending beyond the outermost edges of the foamed slab at at least two opposite edges to define flanges, one of the flanges being coplanar with the facing sheet, and the opposite flange being debossed to permit the coplanar flange of an adjacent panel to overlap the debossed flange and to have its outer surface substantially coplanar with the surface of the adjacent panel, the other surface of the foamed slab being exposed for adhesive bonding to the surface of a supporting structure such as an interior wall or ceiling.