There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

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The Observation of Gravitational Waves from a Binary Black Hole Merger

Antenna Theory And Design

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

Central Force Optimization (CFO) is a new deterministic multi-dimensional search metaheuristic based on the metaphor of gravitational kinematics. It models “probes” that “fly” through the decision space by analogy to masses moving under the influence of gravity. Equations are developed for the probes’ positions and accelerations using the analogy of particle motion in a gravitational field. In the physical universe, objects traveling through threedimensional space become trapped in close orbits around highly gravitating masses, which is analogous to locating the maximum value of an objective function. In the CFO metaphor, “mass” is a userdefined function of the value of the objective function to be maximized. CFO is readily implemented in a compact computer program, and sample pseudocode is presented. As tests of CFO’s effectiveness, an equalizer is designed for the well-known Fano load, and a 32-element linear array is synthesized. CFO results are compared to several other optimization methods.

/pdf/central-force-optimization-a-new-meta-heuristic-with-4iiiu721hd.pdf

Central force optimization: a new meta-heuristic with applications in applied electromagnetics

Here, we propose a modulated geodesic lens antenna array in E-band (56-62GHz), which has scanning abilities in both azimuth and elevation. The array consists of four lens antenna elements, and each lens antenna produces 13 independent beams that cover 110 degrees in the H-plane with scan losses below 1dB. The array is fed with a 1:4 power divider comprising three phase shifters to scan in the E-plane. The distance between lenses in the E-plane is 0.7 wavelengths at 60GHz. The E-plane coverage is 60 degrees with scan losses around −2.2dB. The maximum realized gain varies from 20.8 to 24.1dB across the frequency band.

Azimuth and Elevation Scanning with Stacked Modulated Geodesic Luneburg Lenses

The purpose of this paper is to present hybrid algorithms made by mixing gradient and evolutive algorithms, as a solution to solve electromagnetic problems. Specifically, array synthesis has been chosen to show the functionality of these methods. In this work the discussion was focused on the comparison of the traditional evolutionary algorithm (based on the Darwinian theories), with the most common hybrid algorithms (inspired on Baldwin effect and Lamarckian evolution by Michaelewicz and Fogel, 2004) in some examples of array synthesis.

Hybrid algorithms on antenna design

We present a surface constitutes arrays of periodic patches, which may serve as the metasurface to synthesize the Luneburg lens. The main purpose is by using different sizes of patches to achieve different refractive index at each stage, and get the proper function of Luneburg lens.

The manipulation of surface plasmon polaritons and design of luneburg lens based on periodic patch arrays

In this paper, we explain the concept of higher symmetries, their implications and possible applications-within electromagnetic technology.

Implications of Higher Symmetries in Periodic Structures

In this paper, the miniaturization performance of waveguide bandpass filters loaded with three different periodic metallic metasurfaces is studied. The effective refractive index of holey structure, pin-loaded holes, and glide-symmetric metallic pins and their effects on the compactness of K/Ka band filters are investigated. In the glide-symmetric filter, a fourth-degree Chebyshev response with the center frequency of 28 GHz, bandwidth of 3 GHz, return loss of 20 dB, insertion loss of 0.4 dB, and the size reduction of 41.3% is achieved.

Oscar Quevedo-Teruel

Papers

Azimuth and Elevation Scanning with Stacked Modulated Geodesic Luneburg Lenses

Hybrid algorithms on antenna design

The manipulation of surface plasmon polaritons and design of luneburg lens based on periodic patch arrays

Implications of Higher Symmetries in Periodic Structures

Waveguide Filter Miniaturization with Metallic Metasurfaces