Ampacities of power cables wound on reels

This paper presents a mathematical model that is capable of calculating the ampacity of a wide variety of power cable designs consisting of an arbitrary number of layers on a cable reel. The model considers round cables with copper conductors. The validity and accuracy of the ampacity model were verified by comparing the predicted temperature distribution within the reel with measured temperatures collected during an extensive testing program conducted at the US Bureau of Mines (USBM). The mathematical model predicted a temperature distribution within the cable layers that was very close to the measured variation in temperature. The value of the program is illustrated by calculating ampacities for several copper conductor sizes     

Annular slot-coupled dielectric resonator antenna

An annular slot-coupled dielectric resonator antenna is investigated experimentally. As compared with the previous rectangular-slot version, the new configuration offers a much wider bandwidth of 18%. The return loss, radiation patterns, and antenna gain of the configuration have been measured and are discussed     

Kinetics of sol-to-gel transition for poloxamer polyols

Kinetics of gelation for aqueous solutions of poloxamers 407 and 288 were determined using pulse shearometry. The principle of this method for determining the shear modulus of a semisolid was based on generation of a torsional force that is transmitted through the poloxamer sample at discrete time intervals. Three distinct linear phases were observed for the log dynamic shear modulus (G′) vs. time profiles as poloxamer 407 and 288 solutions of varying concentrations were allowed to passively warm at room temperature to a temperature exceeding the sol-to-gel transition temperature, T_m. The beginning of the second exponential phase coincided with the onset of the gelation process as determined by visual observation. Although gelation appeared visually to be complete at the beginning of the third exponential phase of the log G′ vs. time profiles, this last exponential phase may indicate the rate of formation of the polymer network. A comparison of poloxamer 407 [30% (w/w); T_m = 10.9°C] and poloxamer 288 [37% (w/w); T_m = 11.1°C] would suggest that the concentration of poloxamer required to achieve approximately the same gelation temperature for poloxamers having a similar ratio of poly(oxypropylene):poly(oxyethylene) units decreases with increasing molecular weight of the poly(oxypropylene) hydrophobe contained in the copolymer. Results of these preliminary studies suggest that the gelation process was significantly (p < .05) more rapid for poloxamer 407 at a 30% (w/w) concentration compared to a 30% (w/w) solution of poloxamer 288 when the poloxamer solutions were allowed to passively warm at room temperature. In addition, it appears that the rate of gelation for the poloxamer solutions studied was dependent on the rate of heat transfer through the polymer solution.     

Scattering of EM waves from a slightly rough surface of a generallyanisotropic plane-layered halfspace

The problem of plane wave scattering by a slightly rough boundary of an arbitrarily layered medium with general anisotropy of electric and magnetic properties is considered using boundary conditions transference method and a small perturbation approximation combined with the Green's functions technique. It is shown that in the Born approximation, the second statistical moments of the fluctuation field scattered from an inhomogeneous anisotropic halfspace can be expressed exclusively in terms of the external parameters referring to a flat boundary and the spectral density of roughness. In the present circumstance, the set of the external parameters includes the four plane-wave reflection coefficients from a flat boundary and the (limiting) values of constitutive parameters of the adjacent media at said boundary, Within the framework of the outlined approach, the covariance dyads, Poynting's vector, scattering coefficients and Stokes parameters of the fluctuation field, and the Mueller matrix for a rough boundary are calculated     

Thermal/structural dynamic analysis via approximate analytical approach

The present paper uses a classical Galerkin weighted residual formulation to obtain the approximate analytical solution of a thermally loaded beam executing free flexural vibrations. The approach used is one where the time variable is considered in the same manner as the spatial variable, and is included in the basis functions. The basis functions used in the approach are polynomials obtained from the terms of a power series, with the condition of nullity on the boundary. This choice simplifies the algebraic manipulations considerably and yields close form expressions for components of the system matrix. The latter also simplifies the numerical computation of coefficients of the approximating polynomial. The approach provides benefits in terms of increased accuracy and lower computational costs.     

Space-domain method of moments solution for a strip on a dielectricslab

This paper presents a space-domain method of moments (MoM) solution to the problem of a strip dipole on a dielectric slab. The solution involves the use of a special junction basis function which models the nearly singular polarization currents in the vicinity of the strip/dielectric junction     

Nonlinear Kerr interactions between modulated waves propagating ina single-mode fiber

The interactions induced by the nonlinear refractive index in a single-mode optical fiber (Kerr effect) between a modulated wave and a carrier wave have been investigated for amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). The theoretical analysis, based on a time-domain solution, exploits the well-known formalism of self-phase modulation to describe the propagation of the input electric field in the fiber. The theoretical results were validated experimentally for amplitude- and phase-modulated waves with heterodyne detection techniques. These experiments mimic a coherent transmission system and allow the measurement of the spectrum of each of the waves that participate in the nonlinear interaction