Scattering from and penetration into a dielectric-filled conductingcylinder with multiple apertures

The theory of characteristic modes for aperture problems is used in this paper to solve the equivalent magnetic current and aperture fields due to a conducting cylinder with multiple slots. It is assumed that these slots are illuminated by either a transverse electric (TE) or a transverse magnetic (TM) plane wave and the media inside and outside the cylinder exhibit different electromagnetic properties. The formulation is given for the general case and numerical results for a limited number of slots are presented     

Electromagnetic radiation and scattering at the American Universityof Beirut

This paper presents the work carried out at the American University of Beirut on electromagnetic radiation and scattering, using the characteristic-modes theory. Several problems of various two-dimensional and three-dimensional geometrics have been considered: slots in a plane, slots in a conducting cylinder, a parallel plate-fed slot antenna, an aperture-fed waveguide, a rectangular aperture in a perfectly conducting plane, a cavity-backed aperture. The characteristic modes for each geometry were first computed, and the convergence of the solution was tested for all these problems. A combined characteristic-modes formulation, for the problem of electromagnetic coupling to conducting objects behind arbitrary apertures in a conducting plane, has been developed and used to solve many of these problems     

Characteristic mode formulation of multiple rectangular aperturesin a conducting plane with a dielectric-filled cavity

An analysis that is applicable to the general class of the apertures-fed cavity problem is presented. This formulation is done using the characteristic mode theory for aperture problems. First, a matrix equation whose solution determines the characteristic magnetic currents of the problem is derived. Finally, numerical results for two apertures example are presented to illustrate the generality and the simplicity of the formulation     

A Cost-Effective Design Approach for Permanent Magnet Brushless Machines

Small-power electric machines that use permanent magnets for providing field excitation are becoming increasingly attractive for use in various industrial applications, including those with high-torque requirements andspace limitations. There exists a wide range of designs based on different topologies and different types of magnetic materials. The cost-effectiveness of permanent magnet (PM) machine designs couldbe affected to a great extent by the choice of the magnet material, the overall size of the machine, and the selection of the most appropriate materials, taking into consideration their relative costs and properties. This paper presents an analytical approach to design a surface-magnet electric machine with optimum use of materials on cost basis. Influence of major design parameters is examined, as well using sensitivity analysis. The results show that the optimum split ratio is inversely related to the remanence of the chosen magnet. Also, the impact of the core saturation level on the overall machine cost is investigated.     

Diamond MISFET based on boron delta-doped channel

The delta doping concept has been successfully applied to a diamond field effect transistor structure with an Al₂O₃ gate diode, resulting in full channel carrier activation at room temperature and channel current modulation with complete pinch-off. Using a gate recess configuration, a channel current density of 30 mA/mm with a gate length L_G of 0.8 μm has been obtained with semi-enhancement mode operation. First RF measurements have resulted in f_T and f_max cut-off frequencies of approx. 1 GHz and 3 GHz respectively.     

Antenna array design using spreadsheets

This paper presents a spreadsheet method for the design and analysis of antenna arrays. The method exploits the familiarity of modern spreadsheets programs to a wide variety of computer users and offers them a quick and user friendly means to design and study the characteristics and performance of several classes of linear arrays. It is useful for educational purposes since it does not require writing computer programs nor access to advanced antenna design packages. The procedure is briefly described, and examples illustrating its use with uniform, binomial, and Chebyshev arrays are presented. Linear and polar array factor plots are generated, and estimates of the directivity and the half-power beamwidth are also obtained.     

Parallel Bifold: Large-scale parallel pattern mining with constraints

When computationally feasible, mining huge databases produces tremendously large numbers of frequent patterns. In many cases, it is impractical to mine those datasets due to their sheer size; not only the extent of the existing patterns, but mainly the magnitude of the search space. Many approaches have suggested the use of constraints to apply to the patterns or searching for frequent patterns in parallel. So far, those approaches are still not genuinely effective to mine extremely large datasets. We propose a method that combines both strategies efficiently, i.e. mining in parallel for the set of patterns while pushing constraints. Using this approach we could mine significantly large datasets; with sizes never reported in the literature before. We are able to effectively discover frequent patterns in a database made of billion transactions using a 32 processors cluster in less than an hour and a half. Recommended by: Ahmed Elmagarmid     

Characteristic mode analysis of a slot in a conducting planeseparating different media

The authors analyze a slot in a conducting plane separating different media when the slot is illuminated by a transverse electric and a transverse magnetic plane wave. The general characteristic mode theory for different media is used for the solution of this problem. The characteristic modes, which are computed using the method of moments, provide numerical results for the characteristic currents, the equivalent magnetic currents, and the field pattern for a slot whose width is a function of the wavelength. Analytical expressions for the narrow slot are also given     

Characteristic modes of a slot in a conducting cylinder and theiruse for penetration and scattering, TE case

A characteristic mode theory for slots in a circular conducting cylinder is given for calculating the characteristic magnetic currents, the equivalent magnetic current, the radiation patterns, and the fields everywhere (especially in the aperture region) of an infinitely long thin perfectly conducting cylinder with an infinitely long slot. The characteristic modes are obtained from the solution of an eigenvalue equation representing the continuity of the tangential component of the magnetic field in the slot     

Unlocking diamond's potential as an electronic material

In this paper, we review the suitability of diamond as a semiconductor material for high-performance electronic applications. The current status of the manufacture of synthetic diamond is reviewed and assessed. In particular, we consider the quality of intrinsic material now available and the challenges in making doped structures suitable for practical devices. Two practical applications are considered in detail. First, the development of high-voltage switches capable of switching voltages in excess of 10 kV. Second, the development of diamond MESFETs for high-frequency and high-power applications. Here device data are reported showing a current density of more than 30 mA mm(-1) along with small-signal RF measurements demonstrating gigahertz operation. We conclude by considering the remaining challenges which will need to be overcome if commercially attractive diamond electronic devices are to be manufactured.