• Issue front cover thumbnail

      Volume 40, Issue 4

      June 2015,   pages  1049-1383

    • Parameter estimation of linear and quadratic chirps by employing the fractional fourier transform and a generalized time frequency transform

      Shishir B Sahay T Meghasyam Rahul K Roy Gaurav Pooniwala Sasank Chilamkurthy Vikram Gadre

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      This paper is targeted towards a general readership in signal processing. It intends to provide a brief tutorial exposure to the Fractional Fourier Transform, followed by a report on experiments performed by the authors on a Generalized Time Frequency Transform (GTFT) proposed by them in an earlier paper. The paper also discusses the extension of the uncertainty principle to the GTFT. This paper discusses some analytical results of the GTFT. We identify the eigenfunctions and eigenvalues of the GTFT. The time shift property of the GTFT is discussed. The paper describes methods for estimation of parameters of individual chirp signals on receipt of a noisy mixture of chirps. A priori knowledge of the nature of chirp signals in the mixture – linear or quadratic is required, as the two proposed methods fall in the category of model-dependent methods for chirp parameter estimation.

    • Profit allocation among rational players in a cooperative game under uncertainty

      Sibasis Bandyopadhyay Swapan Raha Prasun Kumar Nayak

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      In this paper, a cooperative game has been considered, where there is a coalition between rational players in an uncertain environment. The uncertainty occurs in terms of the quality of the raw material. The pay-offs of the players are influenced by the degree of satisfaction. Pay-offs are considered as interval numbers. A multisection technique has been applied to obtain a rational solution. In the process, it has been found that the degree of satisfaction of the rational players converges to its optimum value with the convergence of the iterations. A comparative study has been made with methods existing in the literature.

    • Extraction of fetal electrocardiogram (ECG) by extended state Kalman filtering and adaptive neuro-fuzzy inference system (ANFIS) based on single channel abdominal recording

      D Panigrahy P K Sahu

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      Fetal electrocardiogram (ECG) gives information about the health status of fetus and so, an early diagnosis of any cardiac defect before delivery increases the effectiveness of appropriate treatment. In this paper, authors investigate the use of adaptive neuro-fuzzy inference system (ANFIS) with extended Kalman filter for fetal ECG extraction from one ECG signal recorded at the abdominal areas of the mother’s skin. The abdominal ECG is considered to be composite as it contains both mother’s and fetus’ ECG signals. We use extended Kalman filter framework to estimate the maternal component from abdominal ECG. The maternal component in the abdominal ECG signal is a nonlinear transformed version of maternal ECG. ANFIS network has been used to identify this nonlinear relationship, and to align the estimated maternal ECG signal with the maternal component in the abdominal ECG signal. Thus, we extract the fetal ECG component by subtracting the aligned version of the estimated maternal ECG from the abdominal signal. Our results demonstrate the effectiveness of the proposed technique in extracting the fetal ECG component from abdominal signal at different noise levels. The proposed technique is also validated on the extraction of fetal ECG from both actual abdominal recordings and synthetic abdominal recording.

    • Design of a CMOS PFD-CP module for a PLL

      N K Anushkannan H Mangalam

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      This paper introduces a modified design of Phase frequency detector (PFD) with reduced dead zone and improved charge pump (CP) with reduced current mismatch for a Phase Locked Loop (PLL). Three modified PFD circuits are proposed, designed, simulated, and the results are analyzed considering dead zone as a constraint. Design of pass transistor logic network plays a part in the diminution of the dead zone. Further, an improved design of CP is proposed to reduce current mismatch. It is achieved by placing the single ended differential amplifier in current–voltage feedback configuration which offers high output impedance. Simulations are performed using T-SPICE, implemented in IBM 0.13 $\mu$m technology under 1.3 V power supply. Results show that the modified PFD design has a dead zone of 0.3 ns and the current mismatch decrements to 0.1 $\mu$A in an improved CP design.

    • Runtime buffer management to improve the performance in irregular Network-on-Chip architecture

      Umamaheswari S Meganathan D Raja Paul Perinbam J

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      This paper presents a heterogeneous adaptable router to reduce latency in irregular mesh Network-on-Chip (NoC) architectures. Regular mesh-based NoC architecture may become irregular due to variable sized IPs and needs new routing algorithms to ensure throughput. Therefore, an irregular NoC mesh is considered and an adaptive algorithm is used for routing. The performance measures such as through-put, latency, and bandwidth are defined at design time to guarantee the performance of NoC. However, if the application has to change its communication pattern, parameters set at design time (say buffer size) may result in large area and power consumption or increased latency. Routers with large input buffers improve the efficiency of NoC communication, but they incur excessive power dissipation and hardware overheads. Routers with small buffers reduce power consumption, but result in high latency. In the proposed NoC router, input buffers can be dynamically allocated, thereby, latency can be reduced. In a 4 × 4 irregular mesh NoC with a buffer depth of 4 slots, 20% reduction in latency and 9% increase in throughput are attained using dynamic buffer allocation. An 8 × 8 irregular mesh NoC with the proposed router is exposed to the synthetic traffics like uniform, bit complement, tornado and hotspot traffics and it offered a 30.42% reduction in overall average latency and 18.33% increase in overall saturation throughput. The proposed router outperformed the static router by 22.63% less average latency for E3S benchmark applications. For the same performance, maximum of 55% reduction in buffer requirement and 53% less power consumption is achieved.

    • Securing jammed network using reliability behavior value through neuro-fuzzy analysis

      S Raja Ratna R Ravi

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      Wireless multi-hop networks are often exposed to serious physical layer jamming attack. In this attack, the jammer node corrupts the packet by injecting high level of noise and keeps the channel busy and thus blocks the legitimate communication. If multiple jammers collude together, this attack will become very severe. To prevent this attack, a simple yet effective Reliability Behavior Neuro-Fuzzy system has been proposed and it operates in three modules. In module one, each route node obtains its behavior value from the route path and neighboring paths using direct and indirect behavior observations. In module two, based on the behavior value, three factor identification methods have been presented to identify the reliability value of nodes. In module three, using the reliability value the route nodes are level positioned and classified into groups by a neuro-fuzzy classifier. By simulation studies, it is observed that the proposed scheme significantly not only identifies misbehaving nodes with higher detection rate and lower false positive and but also achieves higher network throughput and lower jamming throughput.

    • Investigation of schemes for incorporating generator Q limits in the fast decoupled load flow method

      Lakshmi Sundaresh P S Nagendra Rao

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      Fast Decoupled Load Flow (FDLF) is a very popular and widely used power flow analysis method because of its simplicity and efficiency. Even though the basic FDLF algorithm is well investigated, the same is not true in the case of additional schemes/modifications required to obtain adjusted load flow solutions using the FDLF method. Handling generator Q limits is one such important feature needed in any practical load flow method. This paper presents a comprehensive investigation of two classes of schemes intended to handle this aspect i.e. the bus type switching scheme and the sensitivity scheme. We propose two new sensitivity based schemes and assess their performance in comparison with the existing schemes. In addition, a new scheme to avoid the possibility of anomalous solutions encountered while using the conventional schemes is also proposed and evaluated. Results from extensive simulation studies are provided to highlight the strengths and weaknesses of these existing and proposed schemes, especially from the point of view of reliability.

    • Evolutionary robotics in two decades: A review

      Sameer Gupta Ekta Singla

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      Evolutionary robotics (ER) has emerged as a fast growing field in the last two decades and has earned the attention of a number of researchers. Principles of biological evolution are applied in the form of evolutionary techniques for solving the complicated problems in the areas of robotic design and control. The diversity and the intensity of this growing field is presented in this paper through the contributions made by several researchers in the categories of robot controller design, robot body design, co-evolution of body and brain and in transforming the evolved robots in physical reality. The paper discusses some of the recent achievements in each of these fields along with some expected applications which are likely to motivate the future research. For the quick reference of the readers, a digest of all the works is presented in the paper, spanning the years and the areas of the research contributions.

    • Automatic detection of microaneurysms using microstructure and wavelet methods

      M Tamilarasi K Duraiswamy

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      Retinal microaneurysm is one of the earliest signs in diabetic retinopathy diagnosis. This paper has developed an approach to automate the detection of microaneurysms using wavelet-based Gaussian mixture model and microstructure texture feature extraction. First, the green channel of the colour retinal fundus image is extracted and pre-processed using various enhancement techniques such as bottom-hat filtering and gamma correction. Second, microstructures are extracted as Gaussian profiles in wavelet domain using the three-level generative model. Multiscale Gaussian kernels are obtained and histogram-based features are extracted from the best kernel. Using the Markov Chain Monte Carlo method, microaneurysms are classified using the optimal feature set. The proposed approach is experimented with DIARETDB0 and DIARETDB1 datasets using a classifier based on multi-layer perceptron procedure. For DIARETDB0 dataset, the proposed algorithm obtains the results with a sensitivity of 98.32 and specificity of 97.59. In the case of DIARETDB1 dataset, the sensitivity and specificity of 98.91 and 97.65 have been achieved. The accuracies achieved by the proposed algorithm are 97.86 and 98.33 using DIARETDB0 and DIARETDB1 datasets respectively. Based on ground truth validation, good segmentation results are achieved when compared to existing algorithms such as local relative entropy-based thresholding, inverse adaptive surface thresholding, inverse segmentation method, and dark object segmentation.

    • A review of higher order strain gradient theories of plasticity: Origins, thermodynamics and connections with dislocation mechanics

      Suman Guha Sandeep Sangal Sumit Basu

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      In this paper we review developments in higher order strain gradient theories. Several variants of these theories have been proposed in order to explain the effects of size on plastic properties that are manifest in several experiments with micron sized metallic structures. It is generally appreciated that the size effect arises from the storage of geometrically necessary dislocations (GNDs) over and above the statistically stored dislocations (SSDs) required for homogeneous deformations. We review developments that show that the GNDs result from the non-homogeneous nature of the deformation field. Though the connection between GNDs and strain gradients are established in the framework of single crystal plasticity, generalisations to polycrystal plasticity has been made. Strain gradient plasticity inherently involves an intrinsic length scale. In our review, we show, through a few illustrative problems, that conventional plasticity solutions can always be reduced to a scale independent form. The same problems are solved with a simple higher order strain gradient formulation to capture the experimentally observed size effects. However, higher order theories need to be thermodynamically consistent. It has recently been shown that only a few of the existing theories pass this test. We review a few that do. Higher order theories require higher order boundary conditions that enable us to model effects of dislocation storage at impermeable boundaries. But these additional boundary conditions also lead to unique conceptual issues that are not encountered in conventional theories. We review attempts at resolving these issues pertaining to higher order boundary conditions. Finally, we review the future of such theories, their relevance and experimental validation.

    • Speed estimator for induction motor drive based on synchronous speed tracking

      S B Bodkhe M V Aware J G Chaudhari J G Agrawal

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      This paper presents a new open-loop speed estimation method for a three-phase induction motor drive. The open-loop speed estimators available in literature have the advantage of reduced computational stress over the observers but they share a common limitation of being largely dependent on flux and machine parameters. They involve integrations and differentiation in the algorithm that leads to serious error in estimation when subject to different operating conditions. The proposed estimator is based on synchronous speed tracking and is cost-effective. It is immune to any variation in machine parameters and noise. The synchronous speed is computed from stator frequency which is estimated on-line using the stator current signals. A unique, non-adaptive method for estimation of stator frequency within one-sixteenth of time period is also proposed to enhance the speed of estimation. Computer simulation and experimentation on a 2.2 kW Field oriented controlled induction motor drive is carried out to verify the performance of proposed speed estimator. The results show excellent response over a wide range of rotor speed in both directions including low speed and under different operating conditions. This confirms the effectiveness of the proposed method.

    • Shunt hybrid active power filter for harmonic mitigation: A practical design approach

      Unnikrishnan A K Chandira Sekaran E Subhash Joshi T G Manju A S Aby Joseph

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      The increasing importance of Power Quality problems has been responsible for several improvements in Active Power Filter (APF) typologies in the last decade. The increased cost and switching losses make a pure shunt APF economically impractical for high power applications. In higher power levels shunt Hybrid Active Power Filter (HAPF) has been reported to be a useful approach to eliminate current harmonics caused by nonlinear loads. This paper presents a control strategy and design criteria for transformer-less shunt HAPF with special attention to the integration of series passive filter. The paper also compares the performance improvement of passive harmonic filter when modified as shunt HAPF. Experimental results obtained verify the viability and effectiveness of the proposed design criteria and control algorithm.

    • Heat transfer to MHD oscillatory dusty fluid flow in a channel filled with a porous medium

      Om Prakash O D Makinde Devendra Kumar Y K Dwivedi

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      In this paper, we examine the combined effects of thermal radiation, buoyancy force and magnetic field on oscillatory flow of a conducting optically thin dusty fluid through a vertical channel filled with a saturated porous medium. The governing partial differential equations are obtained and solved analytically by variable separable method. Numerical results depicting the effects of various embedded parameters like radiation number, Hartmann number and Grashof number on dusty fluid velocity profiles, temperature profiles, Nusselt number and skin friction coefficient are presented graphically and discussed qualitatively.

    • Study of a 30 MW bubbling fluidized bed combustor based on co-firing biomass and coal

      Hemant Kumar S K Mohapatra Ravi Inder Singh

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      Today’s power generation sources are largely dependent on fossil fuels due to which the future sustainable development has become a challenge. A significant amount of the pollutant emissions such as carbon dioxide, carbon monoxide and nitrogen oxide from the power sector is related to the use of fossil fuels for power generation. As the demand for electricity is growing rapidly, emissions of carbon dioxide and other pollutants from this sector can be expected to increase unless other alternatives are made available. Among the energy sources that can substitute fossil fuels, biomass fuels appear as one of the options with a high worldwide potential. In the Punjab region of India, Fluidized-bed combustion technology is being used for converting biomass into thermal energy and power generation in various small scale units. The investigation of biomass-based plant through experimental activities and numerical simulation is the scope of this study. The investigations were done at Captive Power Plant (CPP), Ambuja Cement Limited, a project of Holcim, District Ropar, India. During experimental investigations, the study of bed temperatures and steam temperatures at different zones has been done for coal fired and biomass fired combustors with 30% share. No clear effects of co-firing on boiler performance are observed. However, the operational behavior of the boiler in terms of bed temperature and stack emissions shows a different trend. During simulation, the contours of temperature have been obtained for both the boilers and the trends are found in agreement with real process.

    • Estimation of mechanical properties of single wall carbon nanotubes using molecular mechanics approach

      P Subba Rao Sunil Anandatheertha G Narayana Naik G Gopalakrishnan

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      Molecular mechanics based finite element analysis is adopted in the current work to evaluate the mechanical properties of Zigzag, Armchair and Chiral Single wall Carbon Nanotubes (SWCNT) of different diameters and chiralities. Three different types of atomic bonds, that is Carbon–Carbon covalent bond and two types of Carbon–Carbon van der Waals bonds are considered in the carbon nanotube system. The stiffness values of these bonds are calculated using the molecular potentials, namely Morse potential function and Lennard-Jones interaction potential function respectively and these stiffness’s are assigned to spring elements in the finite element model of the CNT. The geometry of CNT is built using a macro that is developed for the finite element analysis software. The finite element model of the CNT is constructed, appropriate boundary conditions are applied and the behavior of mechanical properties of CNT is studied.

    • Numerical assessment of non-uniform corrosion scenarios of rebar in concrete exposed to natural chloride environment

      S Muthulingam B N Rao

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      Corrosion of embedded rebars is a classical deterioration mechanism that remains as one of the most significant problems limiting the service life of concrete structures exposed to chloride-laden environments. The primary objective of this study is to propose and verify a numerical framework that can efficiently quantify non-uniform corrosion penetration depth along the perimeter of the rebar in concrete exposed to chloride environment. This framework investigates the corrosion process during both the corrosion initiation and propagation phases by exploring the effects of not only the rebar existence but also its sizes and locations. The corrosion initiation phase is examined through a comprehensive chloride ingress model that identifies the most important parameters that influence the intrusion of chlorides into RC. The corrosion propagation phase is studied based on a decisive parameter, namely, the corrosion rate. In addition, the framework evaluates the non-uniform corrosion states that correspond to two scenarios of corrosion penetration depth: corrosion of segment of the rebar and uneven corrosion along the rebar perimeter. Numerical solution shows that, in general, chloride build-up along the perimeter of the corner bar is not only faster but also higher than that of the middle bar. Moreover, for the given values of cover thickness and water-to-binder ratio, time-to-corrosion initiation for the corner bar is faster than that for the middle bar. Furthermore, the larger the rebar, in general, the bigger the obstruction, and therefore, the higher the chloride build-up. Qualitative comparisons of the evaluated non-uniform corrosion scenarios with the variety of available laboratory and field data show good agreement.

    • The effect of fly ash to self-compactability of pumice aggregate lightweight concrete

      Murat Kurt Abdulkadir Cüneyt Aydin Muhammed Said Gül Rüstem Gül Türkay Kotan

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      This paper presents the results of an experimental study on the effects of fly ash, different water/(cement + mineral additive) ratios and pumice aggregates to some physical and mechanical properties of self-compacting lightweight aggregate concrete. In this study, pumice had been used as lightweight aggregates. Several properties of self-compacting pumice aggregate lightweight concretes like the unit weight, flow diameter, T50 time, flow diameter after an hour, V-funnel time, and L-box tests, 7, 28, 90 and 180-day compressive strength, 28-day splitting tensile strength, dry unit weight, water absorption, thermal conductivity and ultrasonic pulse velocity tests were investigated. For this purpose, 18 series of concrete samples were prepared in two groups. Pumice aggregate was used as a replacement of natural aggregate, at the levels of 0, 20, 40, 60, 80, and 100% by volume. Furthermore, a second series of 100% pumice aggregate was used for the production of self-compacting lightweight aggregate concrete with constant w/(c+m) ratios as 0.35, 0.40, and 0.45 by weight. The flow diameters, T50 times, paste volumes, 28-day compressive strengths, dry unit weights and thermal conductivities of self-compacting lightweight aggregate concrete were obtained in the range of 600–800 mm, 2–8 s, 471–572 lt/m3, 9.2–53.26 MPa, 839–2156 kg/m3 and 0.321–1.508 W/mk, respectively, which satisfies not only the strength requirement of semi-structural lightweight concrete but also the flowing ability requirements and thermal conductivity requirements of self-compacting lightweight aggregate concrete.

    • Effects of the different atmospheric steam curing processes on the properties of self-compacting-concrete containing microsilica

      Abdulkadir Cüneyt Aydin Ali Öz Riza Polat Harun Mindivan

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      In this paper an attempt has been made to study the use of microsilica on the properties of self-compacting-concrete (SCC) such as compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity (UPV) and micro-hardness when exposed to different atmospheric steam curing temperatures. The influence of microsilica as partial replacement of cement on the properties of SCC is investigated. In this study, mixes were prepared with three percentages of microsilica ranging from 5% to 10% and one controlled mixture without microsilica was also prepared for comparison. The specimens of each concrete mixture were heated up to different temperatures (65°C, 70°C and 75°C). The variables included were the temperature effects (65°C, 70°C and 75°C) using Cem I 42.5. SCC mixes enhanced atmospheric steam curing compressive strength ranging from 29.20 to 38.50 MPa, flexural strength ranging from 4.95 to 6.56 MPa and splitting tensile strength ranging from 1.18 to 1.63 MPa. Test results clearly show that there is little improvement in the compressive strength within temperature range of 70°C as compared to 65 and 75°C, although there is little reduction in splitting tensile strength ranging from 65 to 75°C and with the increase in percentage of microsilica. However, the rate of splitting tensile strength and flexural strength was higher than that of the compressive strength at elevated temperatures and with the increase in percentage of microsilica. In this paper, scanning electron microscopic (SEM) observations were also made to explain the observed residual compressive strength increase between 65°C, 70°C and 75°C.

    • Sedimentation control in the reservoirs by using an obstacle

      Morteza Marosi Mehdi Ghomeshi Hamed Sarkardeh

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      In the present experimental research, effect of different heights of obstacle on turbidity current, to control the sedimentation in a reservoir, was investigated. Experiments were carried out with horizontal and steep bed slopes and different flow conditions. To see the effect of obstacle on concentration of overflow turbidity current, some experiments were carried out without an obstacle. Results showed that concentration of the currents without obstacle reduced exponentially by distance from the entrance gate. More reduction of density and dilution of the currents were observed in the presence of an obstacle, especially with increasing the heights. Increasing height of obstacle also improved their trap efficiency. Moreover, it was concluded that effect of the presence of an obstacle was less intense in a steep bed slope of the reservoir than in a horizontal one.

© 2017 Indian Academy of Sciences, Bengaluru.