An optimized unit cell design of a micro-slit resonant metamaterial is proposed to increase the size frequency stop-bands and enhance sound absorption at normal incidence. Micro-slit metamaterials offer compact lightweight solution for low-frequency noise reduction, in contrast traditional methods such as absorptive foams. A combination numerical semi-analytical solutions based on dispersion cu...

We have used three-dimensional stereolithography to synthetically replicate the gyroid photonic crystal (PC) structure that occurs naturally in the butterfly Parides sesostris. We have experimentally characterized the transmission response of this structure in the microwave regime at two azimuthal angles (ϕ) over a comprehensive range of polar angles (θ). We have modelled its electromagnetic re...

Splitting of speech using comb filters with complementary magnitude response and presenting them to the two ears has helped in improving the perception of speech in sensorineural hearing impaired persons. The pair of comb filters with 18 bands based on auditory critical bandwidths over 5 kHz band, were designed initially with sharp transition between pass and stop bands. Further these filters w...

We present free-space microwave measurements on composite metamaterials (CMMs) consisting of split ring resonators (SRRs) and wires either on the same dielectric board or on alternating boards. Our experimental results disprove the widely held belief that the occurrence of a CMM transmission peak within the stop bands of the SRRs alone and wires alone constitutes a clear demonstration of left-h...

Issues around research ethics and the reproducibility of research are impacting the credibility of science. Firstly, we look at what is to be understand by research ethics, misconduct, and reproducibility. Next, we examine some examples of fraud, beautification, and failed reproducibility. Next, we address the causes and possible resolutions, culminating in the question whether the scholarly li...

In the present work the acoustic band structure of a two-dimensional (2D) phononic crystal (PC) containing an semiconducting ferroelectrics ABC (A=Sb, Bi; B=S, Se, Te; C=I, Br, and Cl) were investigated theoretically and numerically by the plane-waveexpansion (PWE) method. Two-dimensional PC with square lattices composed of semiconducting ferroelectric cylindrical rods embedded in the organic/i...

In this paper gradient based topology optimization (TO) is used to discover 3-D phononic structures that exhibit ultra-wide normalized all-angle all-mode band gaps. The challenging computational task of repeated 3-D phononic band-structure evaluations is accomplished by a combination of a fast mixed variational eigenvalue solver and distributed Graphic Processing Unit (GPU) parallel computation...

CHEBYSHEV APPROXIMATION FOR NON-RECURSIVE DIGITAL FILTERS by James H. McClellan An efficient procedure for the design of finite length impulse response filters with linear phase is pre¬ sented. The algorithm obtains the optimum Chebyshev approximation on separate intervals corresponding to pass and/or stop bands, and is capable of designing very long filters. This approach allows the exact spec...

The effects of periodicity perturbations in underwater phononic crystal layers composed of noninterpenetrating rows of identical shells are investigated. The results for one row are obtained by using a multiple scattering method between shells. Then, taking into account the multiple reflections and transmissions between two adjacent rows, a Debye series method is used to calculate the reflectio...

Any photonic crystal is in practice periodic with some inevitable fabricational imperfections. We have measured angle-resolved transmission of photons that are multiply scattered by this disorder in strongly photonic crystals. Peculiar non-Lambertian distributions occur as a function of frequency: due to internal diffraction, wide angular ranges of strongly reduced diffuse transmission coincide...