• Issue front cover thumbnail

      Volume 42, Issue 11

      November 2017,   pages  1825-1986

    • Comprehensive asynchronous symmetric rendezvous algorithm in cognitive radio networks


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      Spectrum has become a scant quantity with recent upsurge in the field of wireless communication. Cognitive radio network (CRN) alleviates the overgrowing spectrum scarcity and underutilization problem by adequately sharing the frequency bands between licensed and unlicensed users. CRN allows unlicensed users or secondary users (SUs) to opportunistically utilize the free portion of the spectrum allocated to the licensed users or primary users. The fundamental process in the formation of CRN is the rendezvous process where SUs meeton commonly available channels and establish reliable links for effective communication. Existing rendezvous solutions based on the assumption of a common control channel (CCC) among the SUs are infeasible and lessefficient in the dynamic environment of CRNs. Therefore, channel hopping (CH) technique without CCC support, often referred to as blind rendezvous, is usually employed for accomplishing the rendezvous between SUs. This paper presents a comprehensive asynchronous symmetric rendezvous (CASR) algorithm that does not require time synchronization and guarantees rendezvous of SUs in finite time. CASR algorithm exploits the MAC address of SU as the unique identifier (ID) and generates CH sequence based on the dynamic manipulation of ID according to the number of available communication channels. Leveraging the unique ID of each SU, CASR algorithm succeeded in rendezvous guarantee while perpetuating a good time to rendezvous. The efficiency of CASR algorithm is estimated theoretically and verified through various simulation experiments. Simulation results affirm that CASR algorithm performs better in terms of average time-to-rendezvous as compared with existing rendezvous algorithms.

    • Open-eye detection using iris–sclera pattern analysis for driver drowsiness detection


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      This paper proposes a novel approach for open-eye detection that can be used in driver drowsiness analysis based on computer vision techniques. The proposed method captures the driver video using a low resolution camera. The proposed drowsiness detection system has three main stages. The first stage is facedetection using elliptical approximation and template matching techniques. In the second stage, the open eye is detected using the proposed iris–sclera pattern analysis method. In the third stage, the drowsiness state of the driver is determined using PERcentage of eye CLOSure (PERCLOS) measure. The entire system is designed to be independent of any specific data sets for face or eye detection. The proposed method for open-eye detection uses basic image processing concepts of morphological and laplacian operations. The proposed system was evaluated with real-life images and videos. Open-eye detection accuracy of 93% was achieved

    • A new hybrid teaching–learning particle swarm optimization algorithm for synthesis of linkages to generate path


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      This paper proposes a novel hybrid teaching–learning particle swarm optimization (HTLPSO) algorithm, which merges two established nature-inspired algorithms, namely, optimization based on teaching–learning (TLBO) and particle swarm optimization (PSO). The HTLPSO merges the best half of population obtained after the teacher phase in TLBO with the best half of the population obtained after PSO. The population so obtained is used subsequently in learner phase of TLBO. To validate the proposed algorithm, five constrained benchmark functions are considered to prove its robustness and efficiency. The proposed algorithm is applied to synthesize four-bar linkage for prescribed path. It is found that the HTLPSO performs better than other single nature-inspired algorithms for path synthesis problem in mechanism theory. Hence, HTLPSO may prove to bean important tool for mechanism design to follow the prescribed path.

    • An analytical solution based on mobility and multicriteria optimization for access selection in heterogeneous environment


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      Providing global connectivity with high speed and guaranteed quality at any place and any time is now becoming a reality due to the integration and co-ordination of different radio access technologies. The internetworking of existing networks with diverse characteristics has been considered attractive to meet the incredible development of interactive multimedia services and ever-growing demands of mobile users. Due to the diverse characteristics of heterogeneous networks, several challenges have to be addressed in terms of quality of service (QoS), mobility management and user preferences. To achieve this goal, an optimal network selection algorithm is needed to select the target network for maximizing the end user satisfaction. The existing works do not consider the integration of utility function with mobile terminal mobility characteristics to minimize ping-pong effects in the integrated networks. An integrated multicriteria network selection algorithm based on multiplicative utility function and residual residence time (RRT) estimation is proposed to keep the mobile users always best connected. Multiplicative weighted utility function considers network conditions, application QoS and user preferences to evaluate the available networks. In this paper, the proposed scheme is implemented with two mainstreams (pedestrian users and high-velocity users). For high-velocity users, RRT and adaptive residence time threshold are also considered to keep the probability of handover failures and unnecessary handovers within the limits. Monte-Carlo simulation results demonstrate that the proposed scheme outperforms against existing approaches.

    • A novel structure of photonic crystal fibre for dispersion compensation over broadband range


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      This paper studies a novel structure of photonic crystal fibre (PCF) for dispersion compensation at broadband wavelengths. The application of broadband is investigated using a design model based on combination of modal properties and dispersion compensation. The newly designed PCF with defect introduced isrecorded over transmission spectrum range 146.7–256.98 THz, i.e., 1.16–2.04 lm. The modal characteristics and dispersion compensation of 2D PCF with circular air holes defect introduced are investigated and compared to those of conventional hexagonal 2D PCF. Changes in bandwidth behaviour are also observed by changing refractive index and geometric parameter of PCF.

    • A statistical analysis on the leak detection performance of underground and overground pipelines with wireless sensor networks through the maximum likelihood ratio test


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      Leaks in pipelines of the oil and gas industry are an economic and environmental problem that needs to be detected early and effectively. Wireless sensor networks (WSNs) have been researched as one of those technologies to be used in the remote monitoring of pipeline infrastructure. The idea of using tiny sensor nodes on pipelines seemingly provides industries with effective and reliable real-time monitoring, and better coverage density per area. The benefits are apparent in the deployment of WSNs for pipeline monitoring.However, what really lacks is an actual comparison in the detection performance between deployment in overground pipelines and underground pipelines. Extensive research has been going on the use of wireless underground sensor networks for a number of applications. This paper attempts to provide a statistical insight on the concepts of leak detection performance of WSNs when deployed on overground and underground pipelines.The approach in the study employs the hypothesis testing problem to formulate a solution on the detection plan.Through the hypothesis test, the maximum likelihood ratio scheme is used to provide an optimal performanceanalysis of the detection idea. The test also takes into consideration the signal to noise ratio performance of the two settings of underground and overground and is crucial in bringing up a conjecture on the performance of detection. As would be shown in the paper, thresholds, determined by probability, are the key in ensuring a good detecting performance for the WSN.

    • Computational model on pulsatile flow of blood through a tapered arterial stenosis with radially variable viscosity and magnetic field


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      An unsteady two-fluid model of blood flow through a tapered arterial stenosis with variable viscosity in the presence of variable magnetic field has been analysed in the present paper. In this article, blood in the core region is assumed to obey the law of Jeffrey fluid and plasma in the peripheral layer is assumed to be Newtonian. The values for velocity, wall shear stress, flow rate and flow resistance are numerically computed by employing finite-difference method in solving the governing equations. A comparison study between the velocity profiles obtained by the present study and the experimental data represented graphically shows that that the rheology of blood obeys the law of Jeffrey fluid rather than that of Newtonian fluid. The effects of parameters such as taper angle, radially variable viscosity, hematocrit, Jeffrey parameter, magnetic field and plasma layer thickness on physiologically important parameters such as wall shear stress distribution and flow resistance have been investigated. The results in the case of radially variable magnetic field and constant magnetic field are compared to observe the effect of magnetic field in driving the blood flow. It is observed that increase in hematocrit increases the wall shear stress. The values of wall shear stress and flow resistance are obtained at various time instances and compared. It is pertinent to note that the magnitudes of flow resistance are higher in the case of converging tapered than non-tapered and diverging tapered artery.

    • Design of textured surfaces for super-hydrophobicity


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      Although the Cassie–Baxter and Wenzel equations predict contact angles for relative dimensions of micro-pillars on textured surfaces, the absolute pillar dimensions are determined by trial and error. Alternatively, geometries of natural super-hydrophobic surfaces are often imitated to design textured surfaces. Knowing the limitations of both the approaches, this work presents a constraint minimization model on the basis of Cassie–Baxter equation to determine the absolute dimensions of square micro-pillars on a textured surface so as tomaximize the contact angle. The constraints are derived based on the limiting physical conditions at which spontaneous breakdown of super-hydrophobicity takes place. The single-droplet numerical simulations on textured surface gave the duration for which super-hydrophobicity is sustained. The model demonstrated that the round edged pillars, arising out of fabrication imperfections, reduce the height of the pillars without significantly compromising on the contact angle. The measurement of contact angle on the fabricated textured surfaces wasfound to be in agreement with the model predictions when the fabricated pillars had fairly uniform dimensions.The proposed approach is sufficiently general that its application can be extended to design other textured surface

    • Double-diffusive mixed convection in a lid-driven cavity with nonuniform heating on sidewalls


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      The effect of sinusoidal heating on double-diffusive mixed convective flow with heat and mass transfer in a lid-driven square cavity is numerically investigated. The horizontal walls of the cavity are adiabatic and impermeable. Sinusoidal boundary temperatures and concentrations are imposed along the left and rightsidewalls of the cavity. The governing unsteady equations for continuity, momentum, energy and species transfer are solved using the finite-volume method. The numerical solutions are computed for various parameterssuch as the Richardson number, amplitude ratio, buoyancy ratio and phase deviation. The obtained results are discussed in detail under different combinations of the pertinent parameters

    • A method for correcting radial distortion based on verifying the planarity of specimens


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      Image distortion is inevitable when an image is captured through a lens. While the digital image measurement technique is getting popular, image distortion problem can result in significant error. A new distortion correction method is proposed in this study. The proposed method is based on the fact that a flat surface should keep flat when it is measured using three-dimensional (3D) digital image measurement technique. The 3D digital image measurement technique adopted in this research is the simplified 3D digital image correlation (DIC) method. Because radial distortion has a more noticeable influence than other types of distortions,this method deals only with radial distortion. A few experiments are carried out in this study to verify the correctness of this method and its accuracy. Both simulated data and actual image data are adopted in these experiments. The results show that this method can achieve a good accuracy. The standard deviations caused byrandom errors are about the same order as the random errors. It also shows that this method is suitable for both large and small distortion conditions

    • Estimation of riverbank soil erodibility parameters using genetic algorithm


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      Determination of the erodibility parameters, such as critical shear stress and erodibility coefficient, are necessary before estimating the annual bank erosion (or bank retreat) at river reaches. However, in many cases, the river site is inaccessible making it difficult to assess the soil parameters either by in situ tests or by laboratory experiments. In this study, Genetic Algorithm (GA)-based optimisation technique was used to estimate the erodibility parameters of middle reaches of the Brahmaputra River in India. Two approaches were followed. At first, erodibility parameters were estimated using daily stage records at a selected site. Secondly, based on the annual observed bank erosions (bank retreat) from satellite images, erodibility parameters were estimated in three different river reaches. All these results were compared with that from a previous study usingin situ jet tests. Annual bank erosions (bank retreat) were estimated using the median values of the erodibility parameters. The results agree well with the average observed annual bank erosion of these river reaches. In addition, the effects of measurement errors and optimisation algorithms on the parameter estimation were analysed. Sensitivity analysis of the parameters in GA was evaluated and it was found that GA can be utilised in the data-scarce regions to estimate the average erodibility parameters

    • Seventeen-lump model for the simulation of an industrial fluid catalytic cracking unit (FCCU)


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      A 17-lump kinetic model has been developed for the riser–reactor cum regenerator of a fluid catalytic cracking unit (FCCU). This accounts for cracking, hydrogen transfer, aromatization, isomerization, alkylation and dimerization, as well as catalyst deactivation due to the coke deposition in its pores. A model forthe industrial combustor–regenerator unit is also developed. The lumping scheme includes the detailed characterization in terms of the paraffins, naphthenes and aromatics (PNAs) for the VGO feed and also the detailed compositions of the two important products: gasoline and LPG. A total of 199 kinetic parameters for the riser–reactor cum regenerator have been fitted (tuned) using 192 sets of plant data (under different operating conditions) from an industrial FCC unit. The tuned model of the integrated FCCU was run for 15 additional operating conditions. The match was found to be quite good.

    • Stagnation point flow and heat transfer for a viscoelastic fluid impinging on a quiescent fluid


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      A theoretical study is made in the region near the stagnation point when a lighter incompressible viscoelastic fluids impinges orthogonally on the surface of another quiescent heavier incompressible viscous fluid. Similarity solutions of the momentum balance equations for both fluids are equalized at the interface. It isnoted that an exact boundary layer solution is obtained for the lower lighter fluid. The velocity of the lower fluid is independent of lateral interface velocity but the velocity of the upper viscoelastic fluid increases with increasing lateral interface velocity. It is observed that lateral interface velocity increases with increasingviscoelastic parameter for fixed values of density and viscosity ratio of the two fluids. The convective heat transfer is investigated base on the similarity solutions for the temperature distribution of the two fluids. The interface temperature increases with increasing viscoelastic parameter of the upper viscoelastic fluid

© 2017 Indian Academy of Sciences, Bengaluru.