Comment on "Radial dependence of radiation from a bounded source" by Kirk T. McDonald

The purpose of this note is to point out that McDonald's criticism of our work \cite{r1} is based on a circular argument. In order to show that the field of a bounded source falls off as $f(\theta,\phi)/r$ in the far zone, McDonald uses a Huygens-Kirchhoff diffraction integral whose derivation (from Maxwell's equations) already entails assuming a fall-off of this form for the field at infinity \cite{r2}. ($r$, $\theta$ and $\phi$ are the spherical polar coordinates centred on a point within the source, and $f$ is a factor independent of $r$

Modeling and Performance of Microwave and Millimeter-Wave Layered Waveguide Filters

This paper presents novel designs, analysis, and performance of 4-pole and 8-pole microwave and millimeter-wave (MMW) waveguide filters for operation at X and Y frequency bands. The waveguide filters have been designed and analyzed based on the RF mode matching and coupled resonators design techniques employing layered technology. Thorough waveguide filters working at X-band and Y-band have been designed, analyzed, fabricated, and also tested along with the analysis of the output characteristics. Accurate designs of RF waveguides along with their filters based on the E-plane filter concept have been carried out with the ability of fitting into the layered technology in high frequency production techniques. The filters demonstrate the appropriateness in order to develop high-performance well-established designs for systems that are intended for the multi-layer microwave, millimeter- and sub-millimeter-waves devices and systems; with the potential employment in radar, satellite, and radio astronomy applications

Response to "Comment on `Method of handling the divergences in the radiation theory of sources that move faster than their own waves'" [J. Math. Phys. 40, 4331 (1999)]

There is a fundamental difference between the classical expression for the retarded electromagnetic potential and the corresponding retarded solution of the wave equation that governs the electromagnetic field. While the boundary contribution to the retarded solution for the potential can always be rendered equal to zero by means of a gauge transformation that preserves the Lorenz condition, the boundary contribution to the retarded solution of the wave equation governing the field may be neglected only if it diminishes with distance faster than the contribution of the source density in the far zone. In the case of a source whose distribution pattern rotates superluminally (i.e., faster than the speed of light in vacuo), the boundary term in the retarded solution governing the field is by a factor of the order of R^(1/2) larger than the source term of this solution in the limit where the distance R of the boundary from the source tends to infinity. This result is consistent with the prediction of the retarded potential that the radiation field generated by a rotating superluminal source decays as 1/R^(1/2), instead of 1/R. It also explains why an argument based on the solution of the wave equation governing the field in which the boundary term is neglected, such as Hannay presents in his Comment, misses the nonspherical decay of the field

DeepCloud. The Application of a Data-driven, Generative Model in Design

Generative systems have a significant potential to synthesize innovative design alternatives. Still, most of the common systems that have been adopted in design require the designer to explicitly define the specifications of the procedures and in some cases the design space. In contrast, a generative system could potentially learn both aspects through processing a database of existing solutions without the supervision of the designer. To explore this possibility, we review recent advancements of generative models in machine learning and current applications of learning techniques in design. Then, we describe the development of a data-driven generative system titled DeepCloud. It combines an autoencoder architecture for point clouds with a web-based interface and analog input devices to provide an intuitive experience for data-driven generation of design alternatives. We delineate the implementation of two prototypes of DeepCloud, their contributions, and potentials for generative design

Geometric study of Gardner equation

In this paper, we apply the method of approximate transformation groups proposed by Baikov, Gaziziv and Ibragimov, to compute the first-order approximate symmetry for the Gardner equations with the small parameters. We compute the optimal system and analyze some invariant solutions of These types of equations. Particularly, general forms of approximately Galilean-invariant solutions have been computed

Violation of the inverse square law by the emissions of supersonically and superluminally moving volume sources

The generally familiar notion that the conservation of energy requires the intensity of the radiation generated by a localized finite-duration source to decay like the inverse square of the distance from the source is not necessarily true. In this paper, we identify physically tenable sources of acoustic and electromagnetic radiations the amplitudes of whose emissions to particular distant zones decay cylindrically (like {R_P}^{-{1\over2}}) rather than spherically (like {R_P}^{-1}) as R_P tends to infinity (R_P denotes the distance of the observer from the source). These sources have moving distribution patterns which are in general three-dimensional and which propagate faster than the emitted waves. Their emission is characterized by a waveform of constant duration that consists of a continuous assemblage of cylindrically decaying subpulses. Each subpulse embodies a propagating caustic and is narrower the further away it is observed from the source. The change in the lifetime of the subpulses with range (\sim {R_P}^{-1}) is such that their energy---but not their intensity---follows the inverse square law and the Rayleigh distance associated with them is of the same order of magnitude as their distance from the source (R_P) for all values of this distance.\par We present our work in the context of the literature on the non-diffracting wave packets known as acoustic or electromagnetic missiles, and point out how these missiles allow the existing body of data on the emissions from supersonic jets and propellers and from pulsars to be seen in a different light. A supersonically convected aeroacoustic source of volumetric scale L^3 and lifetime T radiates conventional Mach waves whose mean square pressure-fluctuations level scales as \rho^2 U^4cTL /{R_P}^2 (\rho and U areComment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

Morphology of the nonspherically decaying radiation beam generated by a rotating superluminal source

We consider the nonspherically decaying radiation field that is generated by a polarization current with a superluminally rotating distribution pattern in vacuum, a field that decays with the distance \subP{R} from its source as \subP{R}^{-1/2}, instead of \subP{R}^{-1}. It is shown (i) that the nonspherical decay of this emission remains in force at all distances from its source independently of the frequency of the radiation, (ii) that the part of the source that makes the main contribution toward the value of the nonspherically decaying field has a filamentary structure whose radial and azimuthal widths become narrower (as \subP{R}^{-2} and \subP{R}^{-3}, respectively), the farther the observer is from the source, (iii) that the loci on which the waves emanating from this filament interfere constructively delineate a radiation `subbeam' that is nondiffracting in the polar direction, (iv) that the cross-sectional area of each nondiffracting subbeam increases as \subP{R}, instead of \subP{R}^2, so that the requirements of conservation of energy are met by the nonspherically decaying radiation automatically, and (v) that the overall radiation beam within which the field decays nonspherically consists, in general, of the incoherent superposition of such coherent nondiffracting subbeams. These findings are related to the recent construction and use of superluminal sources in the laboratory and numerical models of the emission from them. We also briefly discuss the relevance of these results to the giant pulses received from pulsars

Probabilistic Structural Controllability in Causal Bayesian Networks

Humans routinely confront the following key question which could be viewed as a probabilistic variant of the controllability problem: While faced with an uncertain environment governed by causal structures, how should they practice their autonomy by intervening on driver variables, in order to increase (or decrease) the probability of attaining their desired (or undesired) state for some target variable? In this paper, for the first time, the problem of probabilistic controllability in Causal Bayesian Networks (CBNs) is studied. More specifically, the aim of this paper is two-fold: (i) to introduce and formalize the problem of probabilistic structural controllability in CBNs, and (ii) to identify a sufficient set of driver variables for the purpose of probabilistic structural controllability of a generic CBN. We also elaborate on the nature of minimality the identified set of driver variables satisfies. In this context, the term "structural" signifies the condition wherein solely the structure of the CBN is known

A Maximum-Likelihood Analysis of Observational Data on Fluxes and Distances of Radio Pulsars: Evidence for Violation of the Inverse-Square Law

We analyze pulsar fluxes at 1400 MHz ($S_{1400}$) and distances ($d$) extracted from the Parkes Multibeam Survey. Under the assumption that distribution of pulsar luminosities is distance-independent, we find that either (a) pulsar fluxes diminish with distance according to a non-standard power law, due, we suggest, to the presence of a component with $S_{1400} \propto 1/d$, or (b) that there are very significant (i.e. order of magnitude) errors in the dispersion-measure method for estimating pulsar distances. The former conclusion (a) supports a model for pulsar emission that has also successfully explained the frequency spectrum of the Crab and 8 other pulsars over 16 orders of magnitude of frequency, whilst alternative (b) would necessitate a radical re-evaluation of both the dispersion-measure method and current ideas about the distribution of free electrons within our Galaxy

Magneto-optics of organic crystalline field effect transistors

Organic molecular FETs provide an experimental framework for studying the band-filling dependent properties of two-dimensional metals. Here, we propose experiments to investigate the band-filling dependent cyclotron resonance, and the effect of van Hove singularities.Comment: Submitted for the proceedings of ISCOM200