• Issue front cover thumbnail

      Volume 42, Issue 10

      October 2017,   pages  1629-1824

    • LWDSA: light-weight digital signature algorithm for wireless sensor networks


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      The essential security mechanism in wireless sensor networks (WSNs) is authentication, where nodes can authenticate each other before transmitting a valid data to a sink. There are a number of public key authentication procedures available for WSN in recent years. Due to constraints in WSN environment there is a need for light-weight authentication procedure that consumes less power during computation. This proposed work aims at developing a light-weight authentication protocol using MBLAKE2b with elliptic curve digital signature algorithm (ECDSA). The proposed protocol is also tested using the protocol verification tool Scytherand found to be secure in all claims and roles. This proposed algorithm increases the network life time and reduces the computation time, which is essential for the constrained environment like WSNs.

    • Network lifetime-aware data collection in Underwater Sensor Networks for delay-tolerant applications


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      Development of energy-efficient data collection and routing schemes for Underwater Wireless Sensor Networks (UWSNs) is a challenging issue due to the peculiarities of the underlying physical layer technology. Since the recharging or replacement of sensor nodes is almost impossible after deployment, the critical issue of network lifetime maximization must be considered right from the beginning of designing the routing schemes. We propose a mobile sink (MS)-based data collection scheme that can extend network lifetime,taking into account power-constrained sensor nodes, partitioned networks with geographically distant datacollection points and periodic monitoring applications with delay-tolerance. Lifetime extension is achieved by mitigating the ‘sink neighbourhood problem’ and by deferring the data transmissions until the MS is at the most favourable location for data transfer. Unlike the models available for terrestrial WSNs, we consider non-zero travel time of the MS between data collection points, thus making our model more realistic for UWSNs, both connected and partitioned. The performance of the proposed mobility-assisted data collection scheme is thoroughly investigated using both analytical and simulation models. The analytical results are compared to those of existing models to assess their effectiveness and to investigate the trade-offs. Results show that, with a network size of 60 nodes, the network lifetime achieved by the proposed model is 188% higher than that of static sink model and 91% higher than that of mobile sink model (MSM). The proposed maximum lifetime routing scheme is implemented in the network simulation platform OMNET??, for validating the analytical results as well as for evaluating other performance metrics that are not tractable via analytical methods. Both analytical and simulation results demonstrate the superiority of the proposed model in capturing realistic network conditions and providing useful performance indicators prior to network deployment.

    • Development of optoelectronic-based pulsed current sensor to detect the poor laser discharge condition


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      A current transformer (CT)-based sensor has been developed to detect poor discharge conditions in copper vapour laser. The optoelectronic-based pulsed current sensor architecture involves the optical transmitter–receiver HFBR, high-frequency current transformer, and fiber optic link. The CT has been designed andcalibrated to ensure generation of an optical signal at the current threshold crossover. Bandwidth analysis of the CT is carried out using the bode plot. The optoelectronic inter-conversion of the pulsed voltage of the CT and transmission via fiber optic link provides the non-contact current sensing and remote signal processing of the signal. This study discusses the details of the sensor

    • Analysis and design of broadband U-slot cut rectangular microstrip antennas


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      Broadband microstrip antenna using variations of U-slot has been widely reported. However, in most of the reported work, an in-depth explanation about the mode introduced by U-slot and procedure to design U-slot cut antennas at any given frequency is not explained. In this paper, first an extensive analysis to study thebroadband response in symmetrical and a new configuration of asymmetrical U-slot cut rectangular microstrip antennas is presented. The U-slot tunes higher-order orthogonal mode resonance frequency of the patch with respect to fundamental mode to realise wider bandwidth. Further formulation in resonant length at modified patch modes in symmetrical U-slot cut antenna is proposed. Frequencies calculated using these formulations show closer agreement with simulated and measured results. Using proposed formulations, a procedure to design U-slot cut antenna at different frequencies over 800–4000 MHz range which shows broadband response is explained. Thus, the proposed work gives an insight into the functioning of widely used U-slot cut antennas and the formulations will be helpful for designing at any given frequency

    • Selection of keyframes for video colourization using steerable filtering


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      The appropriate selection of distinctive keyframes to represent the salient contents of a video is a critical task in video processing applications that rely on content analysis or information retrieval. Although many of the existing keyframe selection techniques perform satisfactorily in capturing salient visual contents,they often fail to adequately highlight the changes in visual information brought about by motion of objects between frames. In this paper, we propose a technique for keyframe selection by formulating the dissimilarity between the frames of a video shot in terms of the change in orientations that the corresponding objects of the two frames have undergone due to motion. This is accomplished by steerable filtering of the frames in order to extract the information about the local orientation of pixels within each frame. The frame to frame dissimilarity is adaptively thresholded over a group of frames in order to select the keyframes. In essence, keyframes areselected at the temporal instances where the change in orientation attains local maxima. Our keyframe selection methodology is specifically relevant to video colourization due to the fact that the keyframes that are to be employed for colourization must be chosen such that they capture all orientational changes effectively, while ensuring adequate content coverage.

    • Fuzzy sliding-mode control with low pass filter to reduce chattering effect: an experimental validation on Quanser SRIP


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      Stabilization of a single rotary inverted pendulum (SRIP) system is a benchmark nonlinear control problem. Inherent instability of SRIP in upright position and the presence of modelling uncertainty pose a challenge for control engineers. Sliding-mode control (SMC) is the most widely accepted robust control technique.Various versions of SMCs to stabilize SRIP have been reported in literature. Advantages of SMC come at the cost of chattering of input, which inhibits its usage in many practical applications. Several works have been done to reduce the chattering in SMC. Application of fuzzy logic in SMC to reduce chattering has been analysedextensively in the literature. Even though implementation of fuzzy SMC (FSMC) in theory/simulations completely eliminates chattering, practical implementation of FSMC does not reduce chattering to zero. In this paper, a filtered FSMC is proposed, which filters the high frequency component in the system input. Experimental results of SMC, FSMC and a fuzzy sliding-mode controller with filter (FSMCF) are given in this paper. Results indicate that filtering the output of FSMCF reduces the chattering effect in the system without affecting the closed loop dynamics

    • The energy demand estimation for Turkey using differential evolution algorithm


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      The energy demand estimation commands great importance for both developing and developed countries in terms of the economy and country resources. In this study, the differential evolution algorithm (DE) was used to forecast the long-term energy demand in Turkey. In addition to being employed for solving regularoptimization problems, DE is also a global, meta-heuristic algorithm that enables fast, reliable and operative stochastic searches based on population. Considering the correlation between the increase in certain economic indicators in Turkey and the increase of energy consumption, two equations were used—one applying the linear form and the other the quadratic form. Turkey’s long-term energy demand from 2012 to 2031 was estimated through the DE method in three different scenarios and in terms of the gross domestic product, import, export and population. To prove the success of the DE method in addressing the energy demand problem, the DE method was compared to other methods found in the literature. Results showed that the proposed DE method was more successful than the other methods. Furthermore, the future projections of energy demand obtainedusing the proposed method were compared to the indicators of energy demand estimated and observed by the Ministry of Energy and Natural Resources

    • Dynamic phasor based frequency scanning for grid-connected power electronic systems


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      Frequency scanning is a method of obtaining the frequency response of a system by injecting a small-amplitude wide-band signal as an input in a time domain simulation of the system. This is an alternative to analytical derivation of small-signal models, especially for complex grid-connected power electronic systems(PESs). These models are required for the study of adverse interaction of PES with lightly damped oscillatory modes in a power system. The use of the frequency scans for conventional small-signal stability analysis is predicated upon the time-invariance of the underlying model. Since PES are generally time-periodic, timeinvariance may be achieved in some transformed variables. Although the DQ transformation is suitable in many situations, it is not so for systems with low-order harmonics, individual-phase schemes, unbalanced or singlephase systems, and PES with negative-sequence controllers. This paper proposes the use of dynamic phasor variables in such situations since the underlying model in these variables is time-invariant. The procedure for dynamic phasor based scanning is, however, intricate because wide-band signal injection results in the simultaneouspresence of harmonic dynamic phasor components. The paper outlines this procedure and presents illustrative case studies of Thyristor Controlled Series Compensator (TCSC) and STATCOM. For the TCSC, a comparison of the frequency response obtained from the scanning method and the one obtained from an approximate analytical dynamic phasor model is also presented.

    • Integration of risk matrix and event tree analysis: a natural stone plant case


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      Machining has considerably increased with evolving technology and increasing demand in natural stone production facilities. Different types of accidents may occur in natural stone facilities during movement, dimensioning, cutting of blocks and surface processing. These accidents may be due to physical, chemical, ergonomic and mechanical conditions. Therefore, possible work accidents and occupational diseases should be investigated. In this study, an L-matrix analysis is conducted to analyze hazards and forecast risks in natural stone facilities. According to the L-matrix results, three major initiating events are identified. For each of these initiating events, event tree analysis is used to calculate risk scores. These initiating events are hoist rope fatigue and breaking, diamond wire fatigue and breaking, and electrical leakage due to old systems. These events andtheir results are classified according to the probabilities using event tree analysis.

    • Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode


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      In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were keptconstant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impacttoughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.

    • Linear reciprocating wear behaviour of plasma-sprayed Al2O3–Cr2O3 coatings at different loading and sliding conditions


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      Linear reciprocating wear test is carried out on atmospheric plasma-sprayed Al2O3–Cr2O3 coatings applied on steel substrates. Linear bi-directional sliding wear test of the coatings is performed at different loading and sliding conditions such as load (10, 20 and 30 N), reciprocating amplitude (1.5, 3 and 6 mm) andfrequency (5, 10, 15 and 20 Hz) using ball on flat linear reciprocating tribometer. The patterns of tribological behaviour of the coatings, as manifested at the tribo-contact surface, are judged. Results have shown that the wear rate increases with increasing applied load and frequency and that decreases with increasing reciprocating amplitude. Plastic deformation, detachments of unmelted core, reattachments, delamination and adhesive wear dominate the main failure mechanism of coating.

    • Property elucidation of vacuum-evaporated zinc telluride thin film towards optoelectronic devices


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      A thermal vacuum evaporation system has been used to deposit zinc telluride (ZnTe) thin film on glass substrate in order to investigate the structural, morphological, optoelectronic and electrical properties of the deposited film. The deposited film has been characterised by X-ray diffraction (XRD), atomic forcemicroscopy (AFM), and UV-VIS-NIR spectrophotometer. The polycrystalline and cubic structure of the sample has been confirmed by XRD. The order parameter(s), which determines the crystallinity and good environmental stability of the sample, has been obtained for the peak (1 1 1) to peak (2 0 0) and is found to be 0.83. The XRD patterns and Bragg’s law have been examined to determine the microstructural parameters (lattice parameter,inter-planar spacing, crystallite size, number of crystallites per unit area, strain, dislocation density) of the investigated film. Optical properties (transmittance, absorbance, refractive index, absorption coefficient, extinction coefficient, optical density) of ZnTe thin film were extensively studied in incident photon energy range of 0.5–3.5 eV, where direct optical transition has been obtained with a band gap of 2.63 eV. The surface morphology of the evaporated ZnTe thin film has been checked by AFM.

    • Group SkSP-R sampling plan for accelerated life tests


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      This study presents a group skip-lot sampling plan using resampling (SkSP-R) for accelerated life tests. It is assumed that the lifetime of a product follows Weibull distribution with known shape parameter under the use condition, while the scale parameter can be obtained from acceleration factor. The plan parameters aredetermined through a non-linear optimisation problem for fixed values of producer’s risk and consumer’s risk. The advantages of the proposed plan over the existing one are explained with some practical examples.

    • Development of an anti-loosening fastener and comparing its performance with different other threaded fasteners


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      Threaded fasteners are widely used for temporary joining of different components that require occasional disassembling. However, threaded fasteners may have the problem of loosening under vibrating conditions, which may lead to decreasing clamping force and, thereby, a system failure. In the present experimental investigation, anti-loosening ability of various fastening elements, such as conventional nut, nylock nut,flat washer, spring washer, inside and outside serrated washer, is tested with a conventional M16 high-tension steel bolt. A hybrid double nut is used to clamp the plates in which a conventional nut is used to tighten first, and one nylock nut is then placed at the outer side for further tightening. An adhesive-bonded nut is also tested, where an adhesive is placed between bolt and nut threads. All these fasteners are tested in terms of their loosening characteristics. Accelerated vibrating conditions are used for the test on an indigenously made test rig. A split bolt with taper pin is introduced for the first time to reduce loosening of fasteners. The split bolt with taper pin shows considerably good anti-loosening property compared with other threaded fasteners tested in thiswork.

    • Bridge pier scour in cohesive soil: a review


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      Bridge failure due to local scour has stimulated the enthusiasm of many researchers to study the causes of scouring and to predict the ultimate scour depth at bridge foundation. A brief review of the state of artwork of investigation conducted on local scour at bridge pier in cohesive bed material is presented. Scour process and mechanism at bridge pier in cohesive and noncohesive soil are presented. The effects of parameters influencing local scour around bridge pier is discussed. Empirical equations for predicting ultimate scour depth at bridge pier embedded in cohesive soil are outlined. Comparisons of the equations are made considering two examples: one under laboratory condition and another under field condition.

    • Effect of plant growth regulators on production of alpha-linolenic acid from microalgae Chlorella pyrenoidosa


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      The effect of various plant growth regulators (6-benzylaminopurine (BAP), 6-furfurylaminopurine (Kinetin), gibberellic acid (GA3), 1-naphthaleneacetic acid (NAA) and indole-3-butyric acid (IBA)) on the yields of biomass and an essential free fatty acid (alpha-linolenic acid from Chlorella pyrenoidosa) were studied.NAA and BAP showed significant increase of 2.2- (0.2905 to 0.6497 g/L) and 1.26-fold (0.2905 to 0.3727 g/L) in biomass yield, respectively. The only plant growth regulators belonging to the group cytokinins (BAP and kinetin) showed prominent rise in the yields of alpha-linolenic acid. BAP and kinetin resulted in 2.94- (371.83 to 1105.93 lg/mL) and 3.03-fold (371.83 to 1128.25 lg/mL) increase in ala yields, respectively, compared with that of control.

© 2017 Indian Academy of Sciences, Bengaluru.