Decentralized Spectrum Access Amongst Cognitive Radios—An Interacting Multivariate Global Game-Theoretic Approach

This paper studies decentralized dynamic spectrum access using the theory of multivariate global games. We consider a network of cognitive radios (CRs) where each CR obtains noisy multivariate measurements of the quality of several logical channels and needs to decide which channel to access. Assuming the CRs are rational devices, each CR determines which channel to access, based on its expected throughput and Bayesian estimate of the intention of other CRs. We formulate conditions for which the Bayesian Nash equilibrium (BNE) of the resulting global game is monotonically increasing in the quality of the logical channel. This leads to a simple characterization of the competitive optimal behavior of the system as a function of the prior probability distribution of spectrum hole occupancy, channel quality and observation noise. In obtaining the characterization of the BNE, we extend recent results in univariate global games to the multivariate case.     

Tuning radio resource in an overlay cognitive radio network for TCP: greed isn't good [Accepted from Open Call]

In this article we illustrate the performance of Transmission Control Protocol in an overlay cognitive radio network under dynamic spectrum access. We show that the performance of TCP in overlay CR networks that implement DSA to be quite different from its performance in conventional networks, which do not allow DSA. The key difference is that secondary users in an overlay CR network have to cope with a new type of loss called service interruption loss, due to the existence of primary users. We demonstrate on an NS2 simulation testbed the surprising result: Excessive radio resource usage leads to a decrease in aggregate TCP throughput. This behavior is in contrast to the behavior of TCP in conventional networks, where throughput increases monotonically with the available radio resource.     

Optimal Adaptive Modulation and Coding with Switching Costs

We present an optimal adaptive modulation and coding policy that minimizes the transmission latency and modulation/coding switching cost across a finite-state Markovian fading channel. We formulate the optimal tradeoff between transmission latency and modulation/coding switching cost as a discounted infinite horizon Markov Decision Problem (MDP). By exploiting special structures of the formulated MDP and under certain sufficient conditions, we show that optimal modulation and coding selection policies are monotone in the state variables. These monotone optimal policies are computationally inexpensive to implement and are scalable in terms of channel and switching cost parameters. Numerical results confirm the monotonicity and threshold-based structure of the optimal Modulation and Coding Scheme (MCS) selection policies under the proposed sufficient conditions.     

Microscopic and Spectroscopic Evaluation of Inactivation of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> by Pulsed UV Light and Infrared Heating

Pulsed UV light and infrared heat-treated Staphylococcus aureus cells were analyzed using transmission electron microscopy to identify the cell damage due to the treatment process. A 5-s treatment with pulsed UV light resulted in complete inactivation of S. aureus even after enrichment. The temperature increase during the pulsed UV light treatment was insignificant, which suggested a nonthermal treatment. S. aureus was also infrared heat treated using an infrared heating system with six infrared lamps. Five milliliters of S. aureus cells in phosphate buffer was treated at 700°C lamp temperature for 20 min. The microscopic observation clearly indicated that there was cell wall damage, cytoplasmic membrane shrinkage, cellular content leakage, and mesosome disintegration after both pulsed UV light and infrared treatments. Fourier transform infrared microspectrometry was successfully used to classify the pulsed UV light and infrared heat-treated S. aureus by discriminant analysis.     

Predicting trends in structural and physical properties of a model polymer with embedded natural fibers: Viability of molecular dynamics studies for a bottom up design

The effects of relatively high- and low-shear processing on the macroscopic and microscopic porosities of a standard packaging polymer—linear low density polyethylene (LLDPE) and its composites with pine flour are studied. The macroscopic porosities, represented by deviations of observed density from the theoretical density, primarily drive the trends in mechanical and solvent uptake properties. The microscopic porosities of the system, however, are independent of the processing method and pine flour concentration. Furthermore, by using molecular dynamics (MD), molecules of LLDPE and pine flour were constructed. The material properties of the molecules, specifically microporosity and elastic moduli, were compared to experiment. A semiempirical modeling approach was used to fit the simulated data to the experimental composite moduli. The model of Halpin and Tsai was found to be the most efficacious for this system, and the benefits of the combined MD-semiempirical modeling for bottom up design are discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48189.     

Evolution and Impact of Wi-Fi Technology and Applications: A Historical Perspective

International Journal of Wireless Information Networks - The IEEE 802.11 standard for wireless local area networking (WLAN), commercially known as Wi-Fi, has become a necessity in our day-to-day...     

Physical layer impairment-aware shared path protection in wavelength-routed optical networks

The Journal of Supercomputing - In this paper, physical layer impairment (PLI)-aware shared path protection (SPP) scheme for single-link failures in transparent optical WDM mesh networks is...     

Alkaline earth metal-based catalyst and process for selective hydrocarbon conversion to acetylene and carbon monoxide

A multi-step process that employs a Ni-modified mixed alkaline earth metal oxides (AEMO) has been developed for the selective conversion of hydrocarbons to C₂H₂ and CO. The initial process step is the catalytic decomposition of a gaseous hydrocarbon mixture at an elevated temperature (ca. 800 °C) over Ni/AEMO, generating H₂, trace CO, carbon (C), and trace alkaline earth metal carbide (MC₂). The Ni/AEMO/C/MC₂ material is then heated to consume the remaining carbon, generate more MC₂, and evolve CO. Then, Ni/AEMO/MC₂ is cooled and reacted with excess H₂O at a low temperature (20 < T (°C) < 80) to selectively generate C₂H₂ and Ni/AEM(OH)₂·zH₂O. In the final process step, Ni/AEM(OH)₂·zH₂O is decomposed to yield H₂O and Ni/AEMO, which is recycled within the process. The most advanced Ni/AEMO materials developed thus far exhibit intrinsic production capacities exceeding 2000 μmoles of C₂H₂ per gram of Ni/AEMO per process cycle.     

Binary Cellulose Nanocrystal Blends for Bioinspired Damage Tolerant Photonic Films

Most attempts to emulate the mechanical properties of strong and tough natural composites using helicoidal films of wood‐derived cellulose nanocrystals (w‐CNCs) fall short in mechanical performance due to the limited shear transfer ability between the w‐CNCs. This shortcoming is ascribed to the small w‐CNC‐w‐CNC overlap lengths that lower the shear transfer efficiency. Herein, we present a simple strategy to fabricate superior helicoidal CNC films with mechanical properties that rival those of the best natural materials and are some of the best reported for photonic CNC materials thus far. Assembling the short w‐CNCs with a minority fraction of high aspect ratio CNCs derived from tunicates (t‐CNCs), we report remarkable simultaneous enhancement of all in‐plane mechanical properties and out‐of‐plane flexibility. The important role of t‐CNCs is revealed by coarse grained molecular dynamics simulations where the property enhancement are due to increased interaction lengths and the activation of additional toughening mechanisms. At t‐CNC contents greater than 5% by mass the mixed films also display UV reflecting behaviour. These damage tolerant optically active materials hold great promise for application as protective coatings. More broadly, we expect the strategy of using length‐bidispersity to be adaptable to mechanically enhancing other matrix‐free nanoparticle ensembles.     

Computational fluid dynamics analysis of MQL spray parameters and its influence on superalloy grinding

The application of emulsion for combined heat extraction and lubrication requires continuous monitoring of the quality of emulsion to sustain a desired grinding environment; this is applicable to other grinding fluids as well. To sustain a controlled grinding environment, it is necessary to adopt an effectively lubricated wheel–work interface. The present work aims to develop a numerical model to replicate the mist formation in minimum quantity lubrication (MQL) grinding using a fluent-based computational fluid dynamics (CFD) flow solver. The MQL parameters considered for this study are air pressure and the mass flow rate. Simulation of the atomization under turbulent conditions was done in a discrete phase model (DPM) owing to the fact that oil mass flow rates are very low and oil acts as a discrete medium in air. Jet velocity and droplet diameters were also obtained under different input conditions to find the optimum value of air pressure and mass flow rate of oil to achieve the desired results (lower cutting force and surface roughness) in MQL grinding of superalloy (Inconel 751). It is seen that medium size (around 16.3 µm) of droplet plays a significant role in improved performance by the way of reduction in cutting force and surface roughness.