Experimental and numerical investigation of the reflection coefficient and the distributions of Wigner's reaction matrix for irregular graphs with absorption

We present the results of experimental and numerical study of the distribution of the reflection coefficient P(R) and the distributions of the imaginary P(v) and the real P(u) parts of the Wigner's reaction K matrix for irregular fully connected hexagon networks (graphs) in the presence of strong absorption. In the experiment we used microwave networks, which were built of coaxial cables and attenuators connected by joints. In the numerical calculations experimental networks were described by quantum fully connected hexagon graphs. The presence of absorption introduced by attenuators was modelled by optical potentials. The distribution of the reflection coefficient P(R) and the distributions of the reaction K matrix were obtained from the measurements and numerical calculations of the scattering matrix S of the networks and graphs, respectively. We show that the experimental and numerical results are in good agreement with the exact analytic ones obtained within the framework of random matrix theory (RMT).Comment: 15 pages, 8 figure

Classical wave experiments on chaotic scattering

We review recent research on the transport properties of classical waves through chaotic systems with special emphasis on microwaves and sound waves. Inasmuch as these experiments use antennas or transducers to couple waves into or out of the systems, scattering theory has to be applied for a quantitative interpretation of the measurements. Most experiments concentrate on tests of predictions from random matrix theory and the random plane wave approximation. In all studied examples a quantitative agreement between experiment and theory is achieved. To this end it is necessary, however, to take absorption and imperfect coupling into account, concepts that were ignored in most previous theoretical investigations. Classical phase space signatures of scattering are being examined in a small number of experiments.Comment: 33 pages, 13 figures; invited review for the Special Issue of J. Phys. A: Math. Gen. on "Trends in Quantum Chaotic Scattering

Chaotic scattering with direct processes: A generalization of Poisson's kernel for non-unitary scattering matrices

The problem of chaotic scattering in presence of direct processes or prompt responses is mapped via a transformation to the case of scattering in absence of such processes for non-unitary scattering matrices, \tilde S. In the absence of prompt responses, \tilde S is uniformly distributed according to its invariant measure in the space of \tilde S matrices with zero average, < \tilde S > =0. In the presence of direct processes, the distribution of \tilde S is non-uniform and it is characterized by the average (\neq 0). In contrast to the case of unitary matrices S, where the invariant measures of S for chaotic scattering with and without direct processes are related through the well known Poisson kernel, here we show that for non-unitary scattering matrices the invariant measures are related by the Poisson kernel squared. Our results are relevant to situations where flux conservation is not satisfied. For example, transport experiments in chaotic systems, where gains or losses are present, like microwave chaotic cavities or graphs, and acoustic or elastic resonators.Comment: Added two appendices and references. Corrected typo

Statistics of Resonances and Delay Times in Random Media: Beyond Random Matrix Theory

We review recent developments on quantum scattering from mesoscopic systems. Various spatial geometries whose closed analogs shows diffusive, localized or critical behavior are considered. These are features that cannot be described by the universal Random Matrix Theory results. Instead one has to go beyond this approximation and incorporate them in a non-perturbative way. Here, we pay particular emphasis to the traces of these non-universal characteristics, in the distribution of the Wigner delay times and resonance widths. The former quantity captures time dependent aspects of quantum scattering while the latter is associated with the poles of the scattering matrix.Comment: 30 pages, 15 figures (submitted to Journal of Phys. A: Math. and General, special issue on "Aspects of Quantum Chaotic Scattering"

Multiple cutaneous reticulohistiocytoma

Multicentric reticulohistiocytosis is a rare non-Langerhans cell histiocytosis characterized in its full form by severe destructive arthritis, cutaneous nodules, and systemic manifestations. Cutaneous lesions may precede, accompany, or more commonly develop later than other features in this disease. We describe a case of multiple cutaneous reticulohistiocytoma without any systemic associations after thorough investigations

Aspects of the Scattering and Impedance Properties of Chaotic Microwave Cavities

We consider the statistics of the impedance Z of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental Z data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized impedance whose probability density function is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We find that impedance fluctuations decrease with increasing loss. The results apply to scattering measurements on any wave chaotic system

Optimization of the tool wear and surface roughness in the high-speed dry turning of Inconel 800

AbstractMachining of Inconel 800 superalloy is associated with inherent issues like lower tool life and lower quality of machined surface owing to the work-hardening nature of the superalloy and increased mechanical and thermal stresses. The employment of cutting fluid in machining negatively affects the locale. Hence, dry machining is a feasible alternate solution. This work aims to optimize the cutting parameters (CP): cutting speed, feed rate and depth of cut in the high-speed dry turning of Inconel 800 employing an uncoated carbide insert to minimize the responses: tool wear (TW) and surface roughness (SR). The superalloy machining is conducted as per the experimental runs designed applying the Taguchi analysis. Then, the effects and contributions of the CP on the outputs were examined employing the signal-to-noise (S/N) ratio and the analysis of variance (ANOVA). Additionally, the multi-objective optimization (MOO) method grey relational analysis was employed to optimize CP. The results of the research work showed that cutting speed, feed rate, and depth of cut have noteworthy sway on TW and SR with a % contribution of 33.3, 13.8 and 23.7, respectively. Additionally, evaluation of SEM images of the cutting insert revealed that the abrasion, adhesion and diffusion are the primary wear mechanisms leading to abrasion groves, crater, chipping, built-up-edge and notch formation

Aspects of the Scattering and Impedance Properties of Chaotic Microwave Cavities

We consider the statistics of the impedance Z of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental Z data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized impedance whose probability density function is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We find that impedance fluctuations decrease with increasing loss. The results apply to scattering measurements on any wave chaotic system

Optically Pumped Reconfigurable Antenna Systems (OPRAS)

Abstract This paper presents a new reconfigurable antenna design using optical switching which overcomes any biasing associated with standard MEMs and PIN switches. In our approach, the switching elements comprises of doped silicon, and the change in the element&apos;s RF conductivity from that of a semiconductor material to that of a metal-like material is achieved upon exposure to a laser light coupled through an optical fiber cable. Two prototype antennas are fabricated and tested to demonstrate the proposed approach. Good qualitative agreement is observed between the simulated and measured data. Introduction The RF reconfigurability of a radiating structure (antenna) is of great interest in the field of wireless communications particularly for MIMO systems and cognitive radio applications. The basic concept of RF reconfigurability is to dynamically alter the physical structure of the antenna by connecting and/or disconnecting different parts of the antenna structure which interact with its radiation properties and thereby alters its RF response

Aspects of the scattering and impedance properties of chaotic microwave cavities. Acta Physica Polonica A

We consider the statistics of the impedance Z of a chaotic microwave cavity coupled to a single port. We remove the non-universal effects of the coupling from the experimental Z data using the radiation impedance obtained directly from the experiments. We thus obtain the normalized impedance whose probability density function is predicted to be universal in that it depends only on the loss (quality factor) of the cavity. We find that impedance fluctuations decrease with increasing loss. The results apply to scattering measurements on any wave chaotic system