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      Volume 44, Issue 11

      November 2019

    • Comparative study of flow separation control using suction and blowing over an airfoil with/without flap


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      This study mainly focused on the comparison of the effect of single and simultaneous suction and blowing jets on the aerodynamic performance of an airfoil with/without flap to evaluate the most effective flow control configuration using computational fluid dynamics (CFD) method. Moreover, the effect of applying single and simultaneous jets have been conducted on delaying and controlling the flow separation. The results were obtained using two-dimensional incompressible Unsteady Reynolds-Averaged Navier–Stokes (URANS), and the turbulence was simulated with SST κ - ω turbulence model. Also, different parameters including two jet locations (Ljet), three jet velocity ratios (Rjet), three jet angles (θjet) and three flap deflections (δf) were analyzed to find the most effective case of applying flow control jets to delay the boundary layer separation. It was concluded that applying a single suction jet and simultaneous suction and blowing jets on the flapped airfoil was more effective to improve the lift-to-drag ratio (CL/CD) than applying these jets to the without flap case. Themaximum value of CL/CD was achieved by single suction jet for the without flap case which was equal to 73.7. The maximum increment of stall angle over the without flap airfoil and flapped airfoil was obtained by applying single suction jet, which increased the stall angle from 14° to 20° and 14° to 16° for the suction angle of -90° and suction velocity ratio of 0.15, respectively.

    • A novel and precise on-line digital measurement of unsaturated phase inductance of a switched reluctance motor


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      This paper presents a simple and accurate method for the on-line measurement of the unsaturated phase inductance of a switched reluctance motor (SRM). The basic principle behind the approach is to obtain the instantaneous flux linkage of the phase, which when divided by the instantaneous current of the correspondingphase will dynamically generate the phase inductance for that rotor position. A numerical division process, based on Newton–Raphson (N–R) iterative method, has been implemented using the sensed current and estimated flux linkage on an FPGA platform to generate the inductance value at each instant. It is ensured in the practical implementation that the iron parts do not saturate. It has been also verified through simulation using standard finite-element method (FEM) software packages. Further, it has been established that the effect of mutual inductance is negligibly small. The proposed method will give the true value of the unsaturatedinductance of the phase identified for diagnosis/measurement. Practical results, for the experiments conducted on an existing 4 kW, 1500 rpm Oulton-make SRM, have been also presented. They are further validated against the results obtained from FEM analysis and against previously published results of the phase inductance values for this SRM. The results are found to be in very good agreement.

    • Population-based improvement heuristic with local search for single-row facility layout problem


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      The Single-Row Facility Layout Problem (SRFLP) is a well-known combinatorial optimization problem. The objective of SRFLP is to find out the arrangement of facilities with given lengths on a line so that the weighted sum of the distances between all pairs of facilities is minimized. This problem is known to be NPhard.Hence, a population-based improvement heuristic algorithm with local search is presented in this article to solve SRFLP. The proposed algorithm works well also for the Single-Row Equidistant Facility Layout Problem (SREFLP), where the length of each facility is equal. The computational efficiency of the proposed algorithm is checked with the instances of sizes ranging from 5 to 300 available in the literature for SRFLP and SREFLP. The obtained results are compared to those from different state-of-the-art algorithms. The proposed algorithm achieves best known solutions to date for every instance considered in this article in reasonable computational time.

    • An approach of refining RC4 with performance analysis on new variants


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      Many years of research on the RC4 stream cipher proves it to be strong enough, but there are claims that its swap function is responsible for essential biases in the output. There are suggestions to discard some initial bytes from the key-stream, to get rid of this, before the actual encryption starts, though no optimum valuehas been defined. In this paper, by analysing different variants of RC4, the authors have attempted to find out whether this cipher becomes more secure by discarding initial bytes and, if so, what is its optimum limit. Also, multiple S-boxes generated by different logics and a unique key-mixing procedure have been implemented,which made k RC4 more robust.

    • Flow field investigation behind a trapezoidal rib and the effect of the synthetic jet


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      The motive of the present work is to investigate the combined effect of synthetic jet and chamfer angle (15°, 18° and 21°) of a trapezoidal rib on flow phenomena. However, detailed study is restricted to 21° chamfer angle, which is the optimum angle from the heat transfer perspective. The rib has an obstruction of 5% of the tunnel for an aspect ratio of 30. Emphasis has been given to identifying the optimal location of the synthetic jet at which the recirculation zone behind the rib turbulator becomes a minimum. Experiments are performed on a low-velocity subsonic wind tunnel by particle image velocimetry (PIV) and hotwire anemometry (HWA). Flow field has been characterized in terms of time-averaged velocity magnitude, vorticity, streamlines, turbulence quantities such as turbulence intensity, Reynolds stress and root mean square (rms) velocities as wellas instantaneous flow field. The data are presented at Reynolds number 32,000, based on the hydraulic diameter of the test section. Along with the large primary recirculation, a secondary recirculation bubble is visible at the leeward corner predominantly for the angles 18° and 21°. The secondary bubble is considered to be responsible for maximum heat transfer from the near rib surface. The synthetic jet is placed at different upstream and downstream locations to see the effect on flow parameters. With the synthetic jet, the primary recirculationbubble moves closer to the rib, which ultimately reduces the recirculation length. A greater mixing is observed in the near wake of the obstacle, and the secondary recirculation zone near the surface diminishes. Out of six different synthetic jet locations studied, the maximum reduction of the recirculation bubble is observed when the synthetic jet is placed 0.5D upstream and 1.5D downstream from the rib front face. A comparison has been made between with and without synthetic jet for these flow parameters.

    • Frequency response masking based FIR filter using approximate multiplier for bio-medical applications


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      The advancements in medical healthcare networks and bio-medical sensor technologies enabled the use of wearable and body implantable intelligent devices for healthcare monitoring. These battery-operated devices must be capable of very low power operation for ensuring long battery life and also to prevent intenseradiations. The major power consuming part of these devices are the multipliers built into the digital filters for performing signal processing operations. This paper proposes a low power signed approximate multiplier architecture for bio-medical signal processing applications. The circuit characteristics and error metrics of theproposed multiplier are estimated to verify its performance advantage over other approximate multipliers. In order to validate the efficacy of the approximate multiplier in real time signal processing applications, a band pass finite impulse response filter (FIR) filter is designed using frequency response masking technique and used in the Pan Tompkins method for the extraction of QRS complex from raw ECG data. The sensitivity, positive predictivity, and detection error rate of the QRS detection method are estimated and the results show that the approximate filtering method implemented gives a comparable performance as that of exact methods.

    • Sense disambiguation for Punjabi language using supervised machine learning techniques


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      Automatic identification of a meaning of a word in a context is termed as Word Sense Disambiguation (WSD). It is a vital and hard artificial intelligence problem used in several natural language processing applications like machine translation, question answering, information retrieval, etc. In this paper, an explicitWSD system for Punjabi language using supervised techniques has been analysed. The sense tagged corpus of 150 ambiguous Punjabi noun words has been manually prepared. The six supervised machine learning techniquesDecision List, Decision Tree, Naive Bayes, K-Nearest Neighbour (K-NN), Random Forest and Support Vector Machines (SVM) have been investigated in this proposed work. Every classifier has used same feature space encompassing lexical (unigram, bigram, collocations, and co-occurrence) and syntactic (part of speech) count based features. The semantic features of Punjabi language have been devised from the unlabelled Punjabi Wikipedia text using word2vec continuous bag of word and skip gram shallow neural network models. Two deeplearning neural network classifiers multilayer perceptron and long short term memory have also been applied for WSD of Punjabi words. The word embedding features have experimented on six classifiers for the Punjabi WSDtask. It has been observed that the performance of the supervised classifiers applied for the WSD task of Punjabi language has been enhanced with the application of word embedding features. In this work, an accuracy of 84%has been achieved by LSTM classifier using word embedding feature.

    • Low-velocity impact response of nanotube-reinforced composite sandwich curved panels


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      The low-velocity impact response of the sandwich curved panels with functionally graded carbon nanotube- reinforced composite (FG-CNTRC) surface and isotropic foam core is discussed in this paper. Five types of stacking arrangements including uniform distribution of FG-CNTRC considering thermal environment were analysed. Using the Hertz contact law and rule of mixture model as well as the Kármán-type equations, the nonlinear formulations were built and solved by the two-step perturbation method. The carbon nanotubes’ volume fraction, the structure size, the original impact velocity, temperature, relative thickness and the influence of gradient forms on the panels’ impact behaviours were analysed. The outcomes show that the stiffness of the non-contact surface has large influence on contact response and various types of FG-CNTRC can be used for different operating conditions providing stiffness or cushion performance.

    • Stability of the Riemann solution for a 2 × 2 strictly hyperbolic system of conservation laws


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      In this work, we study the system of conservation laws that is strictly hyperbolic and whose Riemann solution contains delta shock waves as well as classical elementary waves. In order to study stability, we consider the linear approximation of flux functions with three parameters. The approximation does not affectthe structure of Riemann solution. Furthermore, we prove that the solution of the Riemann problem for the approximated system converges to the solution of the original system when the perturbation parameter tends to zero.

    • Studies on electro-chemical corrosion of carbon fiber reinforced aluminium alloy AA7075


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      Carbon fiber reinforced AA7075 is known for good thermal properties and thus used as heat dissipating material. However, few such applications involve corrosive environments too, and hence there is a need to study the behavior of these composite materials under corrosive environment. In the present work,milled carbon fiber reinforced AA7075 composites were produced by vacuum hot pressing with varying amounts of milled carbon fibers. The relative densities of the composites were measured. SEM-EDS, TEM and XRD techniques were also employed for characterization. The composites were then characterized for electrochemical behavior in 3.5 wt.% aqueous NaCl solution by electrochemical polarization technique. Results showed that the corrosion potentials Ecorr have shifted to more negative direction and thus showed increase in corrosion current density, leading to increase in corrosion rate with increasing vol.% of carbon fibers. These results were complemented by SEM micrographs of the composites after corrosion test, which revealed that corrosion occurred at the interface of carbon fiber and matrix due to formation of galvanic coupling between carbon fiber and matrix. Thus, reduced corrosion resistance in composites as amount of fibers increases, is attributed to increase in number of galvanic cells that form at the interface.

    • Development of association rules to study the parametric influences in non-traditional machining processes


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      Non-traditional machining (NTM) processes have already emerged out as the suitable substitutes for the conventional metal removal methods due to their capability of generating complicated shape geometries on diverse difficult-to-machine engineering materials. For these NTM processes, it is always proposed that they should be operated while setting their various input parameters at the optimal levels for achieving better machining performance. In this paper, the application of a data mining tool in the form of development of association rules is explored to determine the best machining conditions for three NTM processes, i.e. electrochemical machining process, ultrasonic machining process and electrical discharge machining process. These rules, presented as simple ‘If-Then’ statements, would also guide the concerned process engineers in investigatingthe effects of various NTM process parameters on the considered responses. It is observed that the most preferred parametric combinations identified based on the generated association rules closely match with those as perceived by the past researchers.

    • A comparative study on allocation/rationing mechanisms operational with/without backorder clearing in divergent supply chains


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      The management of inventory in a divergent supply chain involves inventory allocation/rationing in addition to the determination of order policy parameters. In the case of a stock point feeding product(s) to several downstream members, rationing mechanism can be viewed as a special case of the allocation mechanism. In a supply chain with multi-period ordering cycles, a rationing decision ensures that the entire inventory available with the feeder stock point is rationed to downstream members, whereas an allocation decision neednot allocate the entire inventory available, and it is at the discretion of the decision maker at the feeder stock point to retain inventory for possible high priority demands in future periods. In any supply chain permitting backordering of demands from downstream members, the clearing of backorders is a matter of concern. This study addresses the said issue by ensuring that the feeder stock point considers the current period demand for fulfilment only after clearing the backorders with respect to the downstream members. Through this study, anattempt is made to develop mathematical models for supply chains operating with installation-specific costs (holding and shortage) and ordering policy (base stock) over a finite time horizon with and without clearing backorders in the case of rationing as well as allocating inventory to downstream members. Specifically, thiswork appears to be the first comparative study on allocation and rationing mechanisms in association with/ without backorder clearing mechanisms in divergent supply chains, and their impact on the total supply chaincost.

    • Dynamic model of fractional thermoelasticity due to ramp-type heating with two relaxation times


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      This is an attempt to design a fractional heat conduction model in a bounded cylindrical region exposed to axisymmetric ramp-type heat flux and discuss its thermal behaviour. This model is drafted using the classical theory of fractional thermoelasticity due to the involvement of two relaxation times to the heatconduction equation and the equations of motion. In order to achieve finite thermal wave speed, the heat conduction equation is derived from the viewpoint of Maxwell–Cattaneo law in the context of fractional derivative. Analytical results for the distribution of temperature, displacement and thermal stresses are obtainedusing integral transforms in the Laplace domain. The Gaver–Stehfest method has been used to invert the results of Laplace domain. The convergence of infinite series solutions has been discussed. As a specific case this model has been applied to a thick circular plate subjected to the axisymmetric ramp-type heat flux. The results obtained for the thermal variations are validated by comparing to coupled and generalized theory of thermoelasticity. These comparisons are shown graphically.

    • Bandwidth and gain enhancement of microstrip antenna by frequency selective surface for WLAN, WiMAX applications


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      The research work presents a broad band with enhanced gain FSS based microstrip patch antenna for wireless communication. Three different antennas results are investigated to obtain proposed antenna. The designed antennas are E shaped patch, combined E and T shaped patch and combined E and T shaped patch with frequency selective surface (FSS). The proposed antenna is obtained by combined E and T shaped radiating patches with FSS under the modified ground plane. U shaped slit with multiple number of slots are loaded on theground plane. The broad bandwidth of 6.4 GHz (2.9–9.3 GHz) with 8.12 dBi gain is achieved which is 5.12 dBi greater than the proposed E and T shaped patch (without FSS) antenna. The proposed patch antenna without FSS is fabricated and measured to validate the work. The designed antenna is very much applicable in wireless communication systems. It is specially designed for WiMAX (3.5/5.8 GHz) and WLAN (3.6/4.9/5/5.9 GHz) applications.

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