Articles written in Sadhana

    • Design and development of long-period grating sensors for temperature monitoring

      Smita Chaubey Purushottam Joshi Manoj Kumar Rajesh Arya A K Nath Sanjay Kher

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      Long Period Gratings (LPGs) have been developed using carbon dioxide laser in a standard optical fibre. LPGs with a periodicity of 600 𝜇m and grating length of 24 mm have been inscribed on standard single mode fibre. Such gratings have been used in designing temperature sensors and temperature is monitored up to 80°C. The sensitivity of such type of sensor is 0·06 nm/° C where as for standard Fibre Bragg Grating (FBG) it is 0·011 nm/°C. The LPG performance is also evaluated after 𝛾-ray irradiation for total dose of 5 KGy and has not shown any effect on transmission spectrum.

    • Space vector-based analysis of overmodulation in triangle-comparison based PWM for voltage source inverter

      Manoj Kumar Modi S Venugopal G Narayanan

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      The equivalence of triangle-comparison-based pulse width modulation (TCPWM) and space vector based PWM (SVPWM) during linear modulation is well-known. This paper analyses triangle-comparison based PWM techniques (TCPWM) such as sine-triangle PWM (SPWM) and common-mode voltage injection PWM during overmodulation from a space vector point of view. The average voltage vector produced by TCPWM during overmodulation is studied in the stationary (a–b) reference frame. This is compared and contrasted with the average voltage vector corresponding to the well-known standard two-zone algorithm for space vector modulated inverters. It is shown that the two-zone overmodulation algorithm itself can be derived from the variation of average voltage vector with TCPWM. The average voltage vector is further studied in a synchronously revolving (d-q) reference frame. The RMS value of low-order voltage ripple can be estimated, and can be used to compare harmonic distortion due to different PWM methods during overmodulation. The measured values of the total harmonic distortion (THD) in the line currents are presented at various fundamental frequencies. The relative values of measured current THD pertaining to different PWM methods tally with those of analytically evaluated RMS voltage ripple.

    • Optimization of Weibull deteriorating items inventory model under the effect of price and time dependent demand with partial backlogging


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      In this study, we have discussed the development of an inventory model when the deterioration rate of the item follows Weibull two parameter distributions under the effect of selling price and time dependent demand, since, not only the selling price, but also the time is a crucial factor to enhance the demand in the market as well as affecting the overall finance. In the present model, shortages are approved and also partially backlogged. Optimum inventory level, the optimal length of a cycle and the expressions for profit function under various cost considerations are obtained using differential equations. These are illustrated graphically with the help of numerical examples. The sensitivity analysis of the standards of the parameters has been performed tostudy the effect on inventory optimizations.

    • An integrated framework for software vulnerability detection, analysis and mitigation: an autonomic system


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      Nowadays, the number of software vulnerabilities incidents and the loss due to occurrence of software vulnerabilities are growing exponentially. The current existing security strategies, the vulnerability detection and remediating approaches are not intelligent, automated, self-managed and not competent to combat against the vulnerabilities and security threats, and to provide secured self-managed software environment to the organizations. Hence, there is a strong need to devise an intelligent and automated approach to optimize security and prevent the occurrence of vulnerabilities or mitigate the vulnerabilities. The autonomic computing is a nature-inspired and self-management-based computational model. In this paper, an autonomic-computing-based integrated framework is proposed to detect, fire the trigger of alarm, assess, classify, prioritize, mitigate and manage the software vulnerability automatically. The proposed framework uses a knowledge base and inference engine, which automatically takes the remediating actions on future occurrence of software security vulnerabilities through self-configuration, self-healing, self-prevention and self-optimization as per the needs. The proposed framework is beneficial to industry and society in various aspects because it is an integrated, crossconcern and intelligent framework and provides more secured self-managed environment to the organizations. The proposed framework reduces the security risks and threats, and also monetary and reputational loss. It canbe embedded easily in existing software and incorporated or implemented as an inbuilt integral component of the new software during software development.

    • A non-linear ductile damage growth law at elevated temperature


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      Continuum damage mechanics (CDM) model is commonly used for the prediction of ductile fracture. For numerical simulation of ductile fracture in impact or high-temperature problems, the damage growth law that incorporates the effect of high temperature is needed. Experimentally, it has been observed that damage growth decreases with temperature. However, the damage growth law at high temperature is not easily available in the literature. In the present work, a damage growth law at high temperature is proposed for steel, based on the experimental measurement of damage carried out at IIT Kanpur.

    • Parametric analysis of axial wall conduction in a microtube subjected to two classical thermal boundary conditions


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      Heat transfer in laminar flow microtube is numerically explored with an objective of discriminating conjugate heat transfer process experienced in a microtube under two different thermal conditions. Two classical thermal conditions – constant heat flux and constant wall temperature – are imposed separately on the outersurface of a microtube. Wide parametric variations are considered in this study, for the two thermal conditions, albeit the problem under consideration being very classical from both geometry and thermal condition point of view. The parametric variations considered in this work include wall thickness, wall conductivity and coolant flow rate. An expression for Nusselt number in terms of radial (or transverse) and axial conduction number is presented and validated against existing theoretical correlation as well as reported experimental data for bothcircular and non-circular channels. Dominance of axial conduction over radial (or transverse) conduction is explored and it is found that the effect of wall material on conjugate heat transfer plays an important role. Additionally, it is also observed that with the increase in coolant flow rate, the ratio of radial to axial conductionnumber increases for both thermal boundary conditions.

    • Writer identification using graphemes


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      This paper is presenting a handwriting strokes and grapheme-based offline writer identification framework. This framework works by firstly measuring the hand pressures during script writing using identical grapheme and writing strokes and then generates the pressure descriptors which are rotation as well as scaleinvariant. The descriptors are used to present different hand pressure distribution accuracies which are defined according to approximation-coefficients of the grapheme zone, perpendicular lines average over the handwritten script skeleton, stroke-width, and handwritten script skeleton grapheme. Discrete-Cosine Transform and Principal- Component-Analysis methods are used to evaluate the descriptors execution accuracy. The performance of the proposed method is assessed with the help of one-versus-all strategy and the k-fold validation is done with the help of Structural Support Vector Machine (S-SVM). Whereas heuristic enhancement calculation based simulated annealing is used to identify the S-SVM hyper parameters. The performance assessment of the handwriting strokes and grapheme based offline writer identification framework with single character gives the encouraging results. Also the combination of the characters enhances the accuracy as well as overall performance of personality identification up to 99.99%.

    • Testing and debugging: an empirical evaluation of integrated approaches


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      Software development is a continuous process. Among all phases of software development, testing and debugging are the most essential phases. The main intention of testing is to detect maximum faults as soon as possible. After a fault is detected, it must be removed through appropriate debugging approach. Both phases are performed one after another and require different information. Hence, it is arduous to merge them. In fault detection, such test cases are required that are able to detect all the faults with less effort whereas in faultlocalization such test cases are required that are able to reproduce faults and locate them with accuracy. For enhancing the performance of testing, the integration of these two phases with consideration of multi-objective selection of test cases is to be conducted before regression testing. In the current work, an approach for multiobjective test case selection based on statement and diversified mutant coverage has been proposed and compared with existing approaches. For empirical study, SPEA-2, NSGA-2 and VEGA algorithms have been used and experiments were conducted on three applications of the Defects4j database. Outcomes of the study specify that the proposed approach has the ability to detect more faults compared to existing approaches. It is also able to locate all faults that have been detected with fault localization score better or comparable to existing approaches.

    • Investigations on microstructural and microhardness developments in sintered iron–coal fly ash composites


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      The present work is aimed to explore the microstructural and mechanical characteristics of coal-fly ash reinforced iron metal-matrix composites (IMMCs), synthesized through powder metallurgy technique. Coalfly ash wt%, compacting load and sintering temperature were considered as the input variables, whereas sintered density and microhardness of the composites were taken as the output responses. Flowability and compressibility of the starting materials were demonstrated using Hausner ratio and Carr’s index. Decorous morphological,crystallographic and elemental characteristics of the starting materials and IMMCs were deliberated using Scanning electron microscopy, X-ray diffraction and Energy-dispersiveX-ray spectroscopy investigations respectively. A significant improvement in the microhardness of IMMCs by 50% and drop in density by 35% were found at 15 wt% as compared to 0 wt% reinforcement. The substantial increase in the microhardness eventually resulted in an increase in their specific microhardness by a factor of two. Significant improvements inthe microhardness of IMMCs at 15 wt % of reinforcement, compacted at 10 ton and sintered at 1150°C were found to be prompted by the strengthening mechanisms like load transfer, Hall–Petch effect and Taylor strengthening. The analytically calculated microhardness in the light of strengthening mechanisms was found smaller than the corresponding experimental values as a function of wt % of reinforcement. Further, statistical analysis of the obtained results was carried out using response surface methodology

    • Novel realizations of digitally controlled low power current controlled current conveyor for tuning filter outputs with constant power consumption


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      This paper presents a dual output resistance tunable current controlled current conveyor (DORTCCCII). In the existing current conveyor the change in bias current is required to alter the design parameter Rx which is the intrinsic resistance of input X terminal. This variation changes the internal dc bias conditions such as saturation margins as well as total power consumption of the block. A resistance trimming block is added at X terminal which is controlled by some programmable bits. The usage of programmable bits helps to achieve the desired response without changing bias current, dc operating point and total power consumption. The port relationships of the DO-RTCCCII block are checked and the circuit and design parameters of current follower, voltage follower are analyzed. The operation of filter circuit is also included to illustrate usefulness ofthe proposal. The circuit has been designed and simulated using 28 nm CMOS bulk technology model parameters on Cadence Virtuoso/AMS environment (eldo simulator) using 0.75 V supply voltage and results have been verified with post layout netlist.

    • Retraction Note to: Writer identification using graphemes


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    • Effect of conjugate heat transfer in single-phase laminar flow through partially heated microtubes


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      To analyze conjugate effect under partially heated condition, two-dimensional numerical study is performed for single-phase laminar flow through microtubes. Constant heat flux is applied on outer surface along the heating length of the microtube. For partial heating, the microtube is divided into three parts of 6 mm (L1), 48 mm (L2) and 6 mm (L3). Three cases are considered for partial heating: (a) insulated across 1 and L3 and heating across L2, (b) insulated across L1 and heating across L2 and L3 and (c) insulated across L3 and heating across L1 and L2. For direct comparison, heating across full length of the microtube is also considered. Parametric variations include microtube wall thickness to inner radius ratio (dsf), and solid to fluid conductivity, ratio (ksf) and flow Re. Presence of axial wall conduction is assessed in terms of dimensionless wall temperature and heat flux at the solid–fluid interface, dimensionless bulk fluid temperature, and local and average Nusselt number. The results indicate that there exists an optimal value of average Nusselt number for certain value of ksf at which dominance of axial wall conduction is smaller. Additionally, to highlight the effect of axial wall conduction, local heat flux distribution at the solid–fluid interface is also explored

    • A study on machining performance of wire electric discharge grinding (WEDG) process during machining of tungsten alloy micro-tools


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      In this experimental study, tungsten alloy micro-tools of high aspect ratio are machined through wire electric discharge grinding (WEDG) method using the step machining technique on a hybrid micro-electro discharge machine to achieve high productivity and finish. Tungsten alloy micro-tools are widely used in the fabrication of miniature products. The precise and economical machining of the tungsten material with an optimum level of accuracy and surface properties is a challenge because of its exceptional characteristics like hot hardness, high strength, low wear, and corrosion rate. The material removal rate (MRR) and surface roughness (Ra) responses are studied during machining of micro-tools, selecting the variability of applied voltage, circuit capacitance, and spindle speed during machining for a constant-aspect-ratio micro-tool. Both voltage and capacitance are found to be influencing parameters for MRR and surface roughness. Higher voltage and capacitance values tend to increase MRR and roughness values on the machined micro-tool. Further, the parametric conditions are also identified for higher MRRs and lower surface roughness (Ra) values after employing the hybrid Taguchi design of experimentation methodology. Surface topography of the machined surface studied by energy-dispersive spectroscopy (EDS) reveals the presence of pyrolytic carbon and oxygenelements. Field emission scanning electron microscopy (FESEM) images show a little waviness across the machined surface. A mathematical model is developed to evaluate the correlation among governing parameters for machining response and validated by confirmation experiments. The machining procedure can be further developed to fabricate more predominant fluted micro-tools for difficult-to-machine tungsten material.

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