A Novel FRFT Beamformer for Rayleigh Faded Channels

A method of optimal beamforming for flat Rayleigh faded channels using the Fractional Fourier Transform (FRFT) is considered in this paper. It has been demonstrated through simulations that optimal beamforming with FRFT allows smaller mean-square errors in restoring signals degraded with linear time-or frequency variant distortions and Additive White Gaussian Noise. This is made possible by the additional flexibility that comes with free parameter ‘a’ of the fractional Fourier transform as oppose to the classical Fourier transform (FT). The method is especially useful in moving source problems, where Doppler Effect produces frequency shift when the source is moving, as in mobile and wireless communication where user produces the frequency shift while moving. In this paper it is shown through simulations that beamforming in fractional domain reduces BER as compared to time or frequency domain.     

Calculation of Channel Capacity Considering the Effect of Different Seasons for Higher Altitude Platform System

This paper presents effect of the weather impairments on a high altitude platform (HAP) broadband wireless communication system. It is shown that attenuation due to oxygen, water vapor, fog, cloud, and rain has significant effect on a radio link which is operating in a millimeter frequency range. Channel capacity is calculated for different seasons using Shannon’s channel capacity theorem. The location of HAP is taken to be Delhi (India). Further, it is considered that a user and the HAP platform are stationary.     

Predicting and optimizing the heat transfer performance of radiator with functionalized graphene nanofluids

Accurately predicting the heat transfer characteristics of coolants used in thermal management of energy systems like heat exchangers, power electronics, and heating, ventilation, and air conditioning is indispensable in maintaining its operating conditions within safety limits. Apart from safety, factors such as power consumption and operating cost are the most important constraints to be considered in designing an energy-efficient and cost-effective cooling solution. In this study, the experimental data available from previous research on the use of functionalized graphene-based nanofluids in compact heat exchangers such as the automotive radiator is used to optimize the heat transfer performance parameters like Nusselt number of the nanofluid, the friction factor, and effectiveness of the heat exchanger. A supervised machine learning technique like the artificial neural network is used to obtain the objective functions of the response variables in terms of input features such as Reynolds number, Prandtl number, the volume concentration of nanoparticles in the base fluid, number of transfer units, heat capacity, the density of nanofluid, pressure drop and velocity. On the current dataset, it is found that by using the Bayesian regularization training algorithm and tangent sigmoidal activation function in the neural network, the best accuracies in the prediction can be achieved. Well-known nature-inspired optimization algorithms like genetic algorithms and simulated annealing are used in optimizing the above-mentioned response variables. Both algorithms converged to the same values of the objective functions. The optimum values of Nusselt number, effectiveness, and friction factor are 105.65, 0.506, and 0.0038, respectively, for the given composition of the nanofluid and radiator configuration.     

Exploration of radiative heat on magnetohydrodynamic rotating fluid flow through a vertical sheet

An analysis is built up for the exploration of radiative heat transport on the magnetohydrodynamic flow of rotating fluid over a vertical sheet. The inclusion of thermal radiation in conjunction with the reacting species enhances the energy as well as the solutal profiles respectively. In an advance, external heat source and applied magnetic field effects are considered for further improvement. As the magnetic Reynolds number is low, the influence of the induced magnetic field is neglected. The transformation of governing nonlinear partial differential equations into coupled nonlinear ordinary differential equations is attained with a proper supposition of similarity variables. Moreover, the solution of these transformed equations is scheduled using the “Runge–Kutta fourth-order” method numerically in association with the “shooting technique.” The simulation or various illustrating parameters affecting the flow phenomena are obtained and displayed through graphs and for numerical validation with earlier published work shows the convergence process of the methodology applied. The main findings of the study are; the Dufour number is favorable to enhance the fluid temperature throughout the domain and the destructive chemical reaction also encourages the solutal profile significantly.     

CLAMP: Efficient class-based sampling for flexible flow monitoring

With an increasing requirement to classify traffic and track security threats, newer flexible and efficient ways are needed for collecting traffic statistics and monitoring network flows. However, traditional solutions based on packet sampling do not provide the flexibility required for these applications. For example, operators are often interested in observing as many unique flows as possible; however, random packet sampling is inherently biased towards large flows. Operators may also be interested in increasing the fidelity of flow measurements for a certain class of flows; such flexibility is lacking in today’s packet sampling frameworks. In this paper, we propose a novel architecture called CLAMP that provides an efficient framework to implement class-based sampling. At the heart of CLAMP is a novel data structure we propose called composite Bloom filter (CBF) that consists of a set of Bloom filters working together to encapsulate various class definitions. In particular, we show the flexibility and efficacy of CLAMP by implementing a simple two-class size-based sampling. We also consider different objectives such as maximizing flow coverage and improving the accuracy of certain class of flows. In comparison to previous approaches that implement simple size-based sampling, our architecture requires substantially lower amounts of memory (up to 80×) and achieves higher flow coverage (up to 8× more flows) under specific configurations.     

Thiocompounds as simulants of sulphur mustard for testing of protective barriers

The protective potential of protective devices such as respirators, suits, gloves, and overboots is widely evaluated using the standard colorimetric test (spot disc breakthrough time test, also called SD BTT) involving sulfur mustard (SM) as the challenge chemical. The vesicant nature of SM makes the test inconvenient and poses stringent safety demands. Moreover, such tests are allowed only at a limited number of facilities, causing delay in product development and supply. This prompted the present study on the search for suitable SM simulant responsive to SD BTT test. The diffusivities at BTT (D_BTT) of 10 commercially available thiocompounds through butyl rubber (IIR) were compared vis‐a‐vis D_BTT of SM. For three representative thiocompounds, namely methyl (phenyl thio)acetate, 2‐chloroethyl phenyl sulfide (2‐CEPS) and phenyl‐n‐propyl sulfide (PNPS), the transport parameters through IIR were obtained. PNPS and 2‐CEPS were further compared with respect to D_BTT in elastomers such as IIR, ethylene–propylene–diene methylene rubber, polydimethylsiloxane, nitrile rubber, polybutadiene, and natural rubber. 2‐CEPS showed generally same order of D_BTT as SM implying its potential use as a simulant. The transport parameters for various 2‐CEPS/elastomer systems were also determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Doping effect of viologen on rectification, charge transport processes and photovoltaic properties of furazano (3,4-b)piperazine thin film device

The electrical and photoelectrical properties of a sandwich junction device based on allyl viologen (AV)-doped furazano (3,4-b)piperazine (FP) having structure ln/AV : FP/ITO have been reported. A significant enhancement in the rectification, dark conductivity and photovoltaic response has been observed in AV-doped FP devices compared with undoped FP devices. The present communication deals with the charge transport mechanism and photogeneration process in ITO/AV doped FP/ln Schottky devices. The J–V characteristics recorded in the dark show a rectification effect due to the formation of a barrier at the AV-doped FP/ln interface. Impedance spectroscopy has been used to study the charge transport mechanism for AV-doped FP and its interface with ln. The bulk and junction resistance along with capacitance were determined by analyzing their contribution at an individual level. Doping imparts an improvement in photoresponse of FP as well as an abundance of photoexcited species at the interface. © 2001 Kluwer Academic Publishers     

Polyoxometalate impregnated carbon systems for the in situ degradation of sulphur mustard

Kinetics of in situ degradation bis-(2-chloroethyl) sulphide (sulphur mustard, HD) on polyoxometalate impregnated carbon systems such as 11-molybdo-1-vanadophosphoric acid (V₁/C), phosphotungstic acid (PTA/C), sodium phosphotungstic acid (PTANa/C), phosphomolybdic acid (PMoA/C), sodium phosphomolybdic acid (PMoANa/C) and silicotungstic acid (SiTA/C) have been studied. These carbons were characterized for micropore volume and surface area by N₂ Brunauer, Emmett and Teller (BET) equation. For degradation studies the solution of HD in chloroform was prepared and taken for the uniform adsorption on the carbon systems using incipient volume. Degradation kinetics was monitored by gas chromatograph equipped with flame ionization detector (GC/FID) and found to be following the pseudo first order kinetics. The values of kinetic rate constant and half-life were calculated. V₁/C system showed the fastest degradation of HD. Hemimustard, thiodiglycol, 1,4-oxathiane, sulphoxide and vinyl-2-chloroethyl sulphide were found to be the degradation products with V₁/C system which indicated the oxidative, hydrolytic and dehydrohalogenation reactions, responsible for HD degradation. Effect of moisture was also studied on most reactive system, i.e., V₁/C. The study indicated that V₁/C can be used as a promising adsorbent system for the degradation of HD.