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      Volume 44, Issue 1

      January 2019

    • General Editorial on Publication Ethics

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    • Improvements on the hybrid Monte Carlo algorithms for matrix computations


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      In this paper, we present some improvements on the Markov chain Monte Carlo and hybrid Markov chain Monte Carlo algorithms for matrix computations. We discuss the convergence of the Monte Carlo method using the Ulam–von Neumann approach related to selecting the transition probability matrix. Specifically, we show that if the norm of the iteration matrix T is less than 1 then the Monte Carlo Almost Optimal method is convergent. Moreover, we suggest a new technique to approximate the inverse of the strictly diagonally dominant matrix and we exert some modifications and corrections on the hybrid Monte Carlo algorithm to obtain the inverse matrix in general. Finally, numerical experiments are discussed to illustrate the efficiency of the theoretical results.

    • PCA based hybrid Taguchi philosophy for optimization of multiple responses in EDM


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      The present study is aimed at a multi-response optimization problem by applying Principal Component Analysis (PCA) combined with Taguchi method. The investigation has been carried out through a case study in Electric Discharge Machining (EDM) of D2 steel by using copper, brass and Direct Metal LaserSintered (DMLS) electrode produced by direct metal laser sintering using Directmetal20. The research work has been carried out to evaluate the best parametric combination which could fulfill multiple responses like lowerTool Wear Rate (TWR), higher Material Removal Rate (MRR) and lower Surface Roughness (Ra). Unlike the use of single-objective optimization problem in traditional Taguchi method, a hybrid Taguchi method has beendeveloped in combination with PCA to solve multi-objective problem. Taguchi method assumes that the quality characteristics should be uncorrelated or independent which is not always fulfilled in actual condition. PCA isapplied to remove response correlation and to calculate independent (uncorrelated) quality indices known as principal components. These principal components combined with weighted principal component analysis(WPCA) are used to calculate overall quality index denoted as Multi-response Performance Index (MPI). This investigation combines WPCA and Taguchi method for forecasting optimal setting. The predicted result by this method was validated through confirmatory test proving the efficacy of the process. Out of five input process parameters considered, tool electrode has been found to be the most significant factors through the Analysis of Variance (ANOVA).

    • Expected return time to the initial state for biochemical systems with linear cyclic chains: unidirectional and bidirectional reactions


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      Biochemical systems are robust in nature. We define robustness of a biochemical system as the property where during time evolution, a closed system returns to its initial state. In this study, we propose some mathematical formulations to analyse the robustness of a closed biochemical system. We have provided a tentative guideline towards applying the theory to a non-closed system. We know that a biochemical system evolves with time as a continuous-time Markov process. When this Markov chain is irreducible, it can be proved theoretically that the system will always return to its initial state, and also the expected time of return can bedetermined. This return time depends upon the stationary probability distribution, which is determined as the solution of an eigenvalue equation xQ = 0 where Q is the transition rate matrix. We calculate this expected return time for five different closed systems: unidirectional cyclic linear chains, bidirectional cyclic linear chainsand three real biological systems, and verify the theoretical results against the average return time obtained by stochastic simulation.

    • Design of inductively degenerated common source RF CMOS Low Noise Amplifier


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      The Low Noise Amplifier (LNA) is the first stage in RF CMOS receivers. The Common Gate (CG) LNA and Inductively Degenerated Common Source (CS) LNA are one of the widely used topologies for realizing RF CMOS receivers. The present work emphasizes a simple and exhaustive search procedure for thesynthesis and analysis of CMOS CG and Inductively Degenerated CS LNA circuits. The width (W), gate source voltage (Vgs) and drain source voltage (Vds) of the transistors constitute the design space in the circuit design. The design first involves the use of a circuit simulator (HSPICE) to obtain the small signal parameters of the circuit for various W, Vgs, and Vds of the transistors and then to generate a Look-Up Table (LUT) for all design points using the obtained values. This LUT is used to meet the target performance specifications along with appropriate analytical expressions derived from the circuit in a numerical simulator (MATLAB). This will enable one to explore the whole design space quickly and fastly for arriving at the optimal values for the device dimensions, bias voltages and bias currents of the two LNA circuits. The design methodology is demonstrated by designing CG and Inductively Degenerated CS LNA circuits using 90 nm CMOS technology library in which Inductively Degenerated CS LNA gets high gain and low noise figure than CG LNA.

    • Effect of downstream cylinder rotation on wake dynamics of two inline circular cylinders


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      Two-dimensional numerical investigations have been carried out to study flow past two inline circular cylinders with stationary upstream and rotating downstream cylinder. Computations are performed using commercial software ANSYS Fluent 16.0 for a fixed Reynolds number (Re) of 150 to study wake characteristics unsteady laminar flow. Optimal values of spacing between cylinders and downstream cylinder rotation speed have been identified, confirming the suitability of such an arrangement for drag reduction and flow control. Steady and unsteady features of the wake have been examined with the help of vorticity contours,lift and drag coefficients, their signals and spectra. Interesting phenomena that include multiple transitions in the temporal behavior of the flow and appearance of circulation zone, its development, stabilization, and transformationhave been elaborated in this study.

    • Kernel Optimized-Support Vector Machine and Mapreduce framework for sentiment classification of train reviews


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      Sentiment analysis is one of the popular techniques gaining attention in recent times. Nowadays, people gain information on reviews of users regarding public transportation, movies, hotel reservation, etc., by utilizing the resources available, as they meet their needs. Hence, sentiment classification is an essential processemployed to determine the positive and negative responses. This paper presents an approach for sentiment classification of train reviews using MapReduce model with the proposed Kernel Optimized-Support Vector Machine (KO-SVM) classifier. The MapReduce framework handles big data using a mapper, which performsfeature extraction and reducer that classifies the review based on KO-SVM classification. The feature extraction process utilizes features that are classification-specific and SentiWordNet-based. KO-SVM adopts SVM for theclassification, where the exponential kernel is replaced by an optimized kernel, finding the weights using a novel optimizer, self-adaptive lion algorithm. In a comparative analysis, the performance of KO-SVM classifier is compared with SentiWordNet, Naive Bayes, neural network, and LSVM, using the evaluation metrics, specificity, sensitivity, and accuracy, with train review and movie review database. The proposed KO-SVM classifier could attain maximum sensitivity of 93.46% and 91.249%, specificity of 74.485% and 70.018%; and accuracy of84.341% and 79.611%, respectively, for train review and movie review databases.

    • Ranking cloud render farm services for a multi criteria recommender system


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      Recommender systems that recommend ideal services or items to the online users are a very useful tool for both the users and the businesses. Usually for recommending services, multiple attributes of the services are evaluated and these types of recommender systems that evaluate multiple attributes are called multi criteria recommender systems. In these types of multi criteria recommender systems the ranking of services plays a major role. This work is focused on ranking the cloud render farm services which are of the PaaS (Platform-as-a-Service) type of cloud services that provide the entire platform for the animators to render the files using the cloud resources. This work identifies the Quality of Service (QoS) attributes that are important for the animators for selecting a cloud render farm service. The QoS values of four different real time cloud render farm services were collected by conducting real time experiments using the files of the ‘‘Big Buck Bunny’’, an open-source animated film project and were ranked using three Multi-Criteria Decision Making (MCDM) methods, namely the AHP (Analytical Hierarchical Process), TOPSIS (Technique for Order Preference by Similarity to the Ideal Solution) and SAW (Simple Additive Weighting). The analysis of the ranks obtained using the three different MCDM methods provide many useful insights and conclusions.

    • Development of an auto-synchronization technique for improving the power stability of copper vapour laser oscillator and amplifier configuration


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      A technique to synchronize multiple copper vapour laser (CVL) systems in master oscillator power amplifier configuration to obtain long-duration power stability is discussed in this manuscript. The technique utilizes optoelectronic interconversion of the current pulses of CVL oscillator and amplifiers units as a feedbacksignal. The signal processing of the current pulses was performed using a monostable multivibrator, R–S flipflop and passive low pass filter. The DC voltage generated corresponding to the quantum of temporal mismatch between the oscillator and the amplifier modules is sampled, averaged and compared to the set point voltage using a Programmable Logic Controller. The timing signal of the respective amplifiers could be accordingly adjusted to synchronize with the CVL oscillator optical pulses to obtain long-duration power stability.

    • Effect of tool pin geometry and weld pass number on microstructural, natural aging and mechanical behaviour of SiC-incorporated dissimilar friction-stir-welded aluminium alloys


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      The aim of this investigation was to study the effect of tool pin geometry and pass number on mechanical and microstructural behaviour of SiC-incorporated dissimilar friction stir welding of 6-mm-thick plates of AA6061-T6 and AA2024-T351. Two tool pin geometries, square and triangle frustum, were used. Itwas found that the weld made by square frustum pin and two passes with rotation in the same direction produces more homogenized and finer distribution of SiC particles. Also, the grain size of stir zone in the weld made by two passes is finer than that made by one pass. The weld made by triangle frustum pin shows higher thermomechanically affected zone hardness, natural aging kinetics and tensile strength than the others.

    • Application of an in-wheel direct drive motor based on switched reluctance motors for low-power electric vehicles


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      This paper presents application of a switched reluctance motor with exterior rotor as an in-wheel direct drive motor for low-power electric vehicles (EVs). A prototype system is realized for experimental studies. Both analytical method and finite-element analysis (FEA) are used in this research to obtain characteristics of the motor. The results of the FEA and analytical calculations are presented, and compared to experimental results. The obtained test and simulation results show that the proposed system is suitable for lowpower and low-cost EVs.

    • A data envelopment analysis approach for resource allocation with undesirable outputs: an application to home appliance production companies


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      Traditional data envelopment analysis (DEA) models use all multiple inputs and outputs to estimate efficiency scores of decision-making units (DMUs). Each unit may consist of several subunits in cases such as manufacturing systems, and each subunit may produce both desirable and undesirable outputs. Providinginformation about the proportion of resources for each subunit could assist managers in making better decisions for increasing the efficiency of production systems. The current study proposes a new approach for resourceallocation and efficiency estimation of production units by considering partial impacts among inputs and outputs in the DEA framework. A weak disposable technology is used in these evaluations, and an empirical applicationof the proposed approach for obtaining performance of home appliances production companies is provided for illustration purposes.

    • Bio-molecular event extraction by integrating multiple eventextraction systems


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      Event extraction from biomedical text is a very important task in text mining and natural language processing. The overall task involves finding event-related expressions, classifying these into predefined categories and attaching arguments to these events. We perform event detection and event classification in one stepusing an ensemble of classifiers. For event argument extraction, we also use an ensemble of classification models. Our base models are developed using supervised machine learning that makes use of statistical, contextualand syntactic features. Our experimental result on the benchmark datasets of BioNLP-2011 shared task shows the recall, precision and F-measure values of 51.20%, 65.78% and 57.58%, respectively.

    • Space-time Gaussian models for evaluating corrosion-induced damages in reinforcing bars


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      Chloride-induced steel reinforcing bars corrosion is a problem of worldwide importance because, in addition to massive industrialization, a majority of human population inhabit marine atmosphere zones where salinity is the main source of built infrastructure deterioration. Reinforced concrete structures vulnerable tochloride-induced corrosion potentially experience two stages of damage, namely non-structural and structural. Till date, with regard to non-uniform corrosion, there is very limited information regarding the significant role played by the non-structural stage of damage in influencing the progression of structural damage. The present work examines the process of non-uniform chloride ingress into concrete due to the existence of the steel bars and its influence on the spatial and temporal variations in the depth of corrosion penetration. Mathematicalmodels in the form of Gaussian functions are proposed to represent space-time variation in corrosion initiation, spatial spread of corrosion penetration depth and corroded bar morphologies, and are compared with literature data. A numerical inverse analysis procedure is introduced to predict space-time evolution of non-structural damage from experimentally observed spatial spread of structural damage. Further, applicability of superposition approach for the evaluation of corrosion-induced stresses around the steel–concrete interface of a cornerreinforcing bar is explored and shown to introduce spatial and temporal errors while evaluating structural damages.

    • CAD modeling and finite elemental design of indigenous knee brace


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      Walking problems aggravate with the advent of old age. One of the treatments for the walking problems is the use of knee brace. This paper reviews the existing designs of knee braces, assesses their merits and demerits and proposes an efficient, cost-effective, light-weight and attractive design of knee brace for Indianpopulation. This paper models design of knee brace and analyzes stress shielding capacity of the knee brace using Finite elemental analysis. This paper discusses how this knee brace can overcome difficulties faced by other knee braces in market.

    • The development of spectral features in the speech of Indian children


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      Indian children represent a unique population of bilinguals who learn two or more languages of different isochrony. Most of their native languages are syllable-timed, whereas in school the language of learning is English, which is a stress-timed language. Exposure to multiple languages with different types of rhythmic patterns as stimulus during the development stage differentiates these children from monolinguals acquiring rhythms of a single language. Thus, to partially fill this gap, a comparative study in 115 children (aged four to eight years) and 18 adults was carried out. We investigated the frequencies around the pitch and firstformant which encodes prosodic information in speech. It was found that the harmonic content in speech increases even after four years (where children exhibit or possess intelligent speech) and the spectra of adults were more distributed and had more peaks at higher frequencies as compared to the power spectra of children, where energy in higher frequency was less. This study has implications in finding speech abnormalities in Indian children with speech disorders.

    • A review of microstructure, mechanical properties and wear behavior of hybrid aluminium matrix composites fabricated via stir casting route


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      This article focuses on the mechanical and wear properties of the Al-based hybrid composites fabricated by stir casting route. A wide range of literature has been consulted in this regard and it has been revealed that processing conditions can be tailored to obtain homogeneous structure of the Al-composites. The addition of ceramic particles has been found to be essential to provide requisite strength and hardness to these composites. Also, use of agro/industrial waste materials such as fly ash, red mud and rice husk ash as a complementary reinforcement reduces the density of the hybrid composites without compromising the mechanical properties. The literature review also indicates that addition of soft reinforcements along with hard reinforcements reduces the brittleness of the hybrid composites. Moreover, the presence of solid lubricants like graphite significantly improves the wear resistance of these materials. It has been noticed that incorporation ofsolid lubricants also helps in the formation of a protective tribolayer at the interface thereby reducing the wear rate and plastic deformation of these composites. In overall, study concludes that Al-based hybrid composites have great promise to serve as a substitute to the ceramic reinforced composites and the unreinforced Al-alloys in various automotive applications requiring low cost, high strength-to-weight ratio and superior wear resistance.

    • Failure rate analysis of Jaw Crusher: a case study


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      Failure of crusher components has considerable influence on the productivity of a crushing plant. In order to improve performance and operational reliability, its critical components are needed to be identified to make replacement in time before any catastrophic failure happens. Though traditional maintenance practicesexist in crushing plants, a methodical analysis of failure trend is imperative to improve operational reliability of this critical equipment. The present paper deals with failure analysis of rock crusher and its critical components using total time on test (TTT)-plot and other statistical tools. TTT-plot has proven to be a useful tool inreliability analysis.

    • Design variability verification in Software Product Lines


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      This paper proposes a novel notion called variability verification applicable to Software Product Lines (SPL). Variability is central to SPL and we have observed that variability is expressed differently at different levels of abstraction in the development flow of SPL. A natural problem in this context is theconformance of variability information expressed at different levels. Design variability verification, in particular, checks whether the variability expressed at the design level conforms to that at the requirement level. Unlike many existing approaches to SPL modelling, our work does not assume a single global view of variation points, even within the same level of abstraction. In our view, an SPL is a concurrent composition of features, where each feature exhibits independent variability. This enables incremental addition of variability. The procedure iscompositional in the sense that the verification of an entire SPL consisting of multiple features is reduced to the verification of the individual features. Feature level verification essentially involves standard model checking while, in the second step, a Quantified Boolean Formula (QBF) is synthesized and solved. The method has been implemented and demonstrated in a tool SPL Engine for Design Verification (SPLEnD) on a couple of fairly large case studies. SPLEnD uses SPIN tool for the feature level conformance, while the state-of-the-art QBFsolver CirQit is used for the SPL level conformance. SPLEnD easily handles the evolution of SPL by addition of new features and modification of existing features. Experimental results with SPLEnD look very promising.

    • Bacterial based admixed or spray treatment to improve properties of concrete


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      The capability of calcite precipitation by microbes is a well-known natural phenomenon and is now successfully employed to improve properties of concrete. The calcite precipitation by microbes will be affected by the process in which bacteria is introduced into concrete. The present study highlights different ways ofmicrobial incorporation into concrete and its effect on the properties of resultant concrete. The bacteria were introduced into concrete either during casting or curing of concrete. The efficiency of the proposed microbial treatment was monitored in terms of strength development, water impermeability, pH of the pore solution, microstructure and level of CaCO3 precipitated. It was observed that both admixed treatment or spray treatment during curing were effective in calcite precipitation. The procedure involving spraying of bacterial culture onto concrete surface was efficient as well as economical.

    • Simulation of free surface flows with non-hydrostatic pressure distribution


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      In this work, a free surface flow simulator is developed in which Navier–Stokes equations using Marker and Cell (MAC) method in the framework of finite difference methodology have been solved. The free surface is tracked by the volume of fluid (VOF) method. The numerical code without free-surface is validated against the flow past a square cylinder. Three different free surface flows, i.e., dam break flow, two-dimensional cavity filling and undular bore, are studied to demonstrate the efficacy of the developed numerical model to simulate free surface flow. The numerical model used in the present work involves tracking of free surface of a single fluid in a two-fluid system. The parameters which can affect the interface orientation of the fluid is given as boundary condition at the interface. The inherent advantage of such numerical models is its ability to trackfree surface for high density and viscosity ratio fluids like air–water. The numerical model used in the present work is capable of solving such high density ratio two-fluid systems for which the effects due to surface tension are negligible. Results from all the problems are compared with earlier results available in literature.

    • Negative lift characteristics of NACA 0012 aerofoil at low Reynolds numbers


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      Numerical investigations on the flow over NACA 0012 aerofoil are carried out to provide better understanding of the unusual lift characteristics exhibited by this aerofoil at low Reynolds numbers. Computations are carried out at Re = 10,000–100,000, for different values of angles of attack and freestream turbulenceintensity. There exists a narrow range of these parameters where the net circulation around this symmetrical aerofoil is negative, leading to the generation of negative lift at positive angles of attack. Different flow regimes are identified and physical explanations are given for this unusual behaviour of negative lift, andthe influence of different flow parameters is discussed.

    • In-plane anisotropy and tensile deformation behaviour of aluminium alloy AA 2014 forge plates


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      Plastic flow behaviour and fracture mechanism of aluminium alloy AA 2014 forged plates under tensile loading conditions are investigated and the results obtained are presented and discussed in the present study. The effects of heat treatment (namely, solution treatment and artificial ageing) on micro-structural homogeneity,tensile behaviour and nature of fracture were studied using hardness, tensile, optical and scanning electron microscopy methods. Experimental engineering stress–engineering strain and true stress–true strain data of the aluminium alloy AA 2014 in different ageing conditions have been analysed using Hollomon, Ludwik and Ludwigson plastic flow relationships. The alloy is found to exhibit moderate degree of in-plane anisotropy and anisotropic index. Further, the alloy in both solution-treated and aged conditions exhibits three different stages ofstrain-hardening rate and the highest strain-hardening rate occurs at regions of lower strain both in solution-treated and peak-aged conditions. It is also observed that the longitudinal specimen (L parallel to forging direction) exhibitshigher strain hardening, while the specimen with T orientation exhibits lowest strain-hardening rates both in solution-treated and aged conditions. The alloy under study in all the heat treatment conditions exhibits ductile fracture mechanism with higher density of uniformly distributed macro- and micro-dimples.

    • Performance assessment of evacuated U-tube solar collector: a numerical study


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      This paper presents a finite element method based three-dimensional thermal model for predicting the performance of evacuated U-tube solar collector. Numerically predicted working fluid outlet temperature is compared with the experimental data available in the literature and a good agreement is observed between them. The influence of average solar irradiance on efficiency and useful heat gain rate of the solar collector is studied for two different evacuated tube configurations. Employing water and air as working fluid, copper, aluminiumand brass as U-tube material, and graphite, magnesium oxide and aluminium oxide as filler material and the performance of the evacuated tube solar collector is investigated in detail.

    • Voltage minimization control of vector controlled interior permanent magnet motor


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      Maximum Torque Per Voltage trajectory has been utilized only during field weakening operation of Interior Permanent Magnet (IPM) motor. In this paper, the voltage minimization control from zero-speed is proposed. Voltage minimization results in maximum torque per voltage control of IPM motor. The control implementation is also simple in comparison to current minimization, as the operation is always along the current-limit locus irrespective of operation in field-weakening. Voltage minimization technique minimizes the core losses whereas current minimization would minimize the copper losses. The mathematical model of IPM motor following voltage minimization is derived and the solution to the 4th order quartic equations is obtained using Ferrari’s method. The solution obtained is utilized to develop a look-up table for vector control of IPM motor. A comparative analysis of voltage minimization and current minimization is established which is supported by simulation results and demonstrated by detailed experimental results.

    • Shock structures of underexpanded non-circular slot jets


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      Flow visualization studies using shadowgraph technique are carried out to investigate the shock evolution from non-circular slot jets at various under-expansion levels. The non-circular topologies considered are triangular, square and elliptic, and the circular jet is taken as the baseline case for the study. These jets are underexpanded in the pressure ratio (R) range of 2–6 corresponding to a fully expanded jet Mach number up to 1.85. Results indicate that the shock cell structures of non-circular jets strongly depend upon the initial shape ofthe topology. The shock structures of triangular jet have additional secondary oblique shocks that are distinct from those of other non-circular jets. Mach disk is almost absent in a shock cell structure of triangular jet, which is unlike the case of other jets used in the study. The study suggests that square jet undergoes faster diffusion process compared with the triangular jet. Axis-switching phenomenon is predicted for the elliptical jet at a distance of 3–7 equivalent diameters.

    • The calculate of optical gap energy and urbach energy of Ni1-xCoxO thin films


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      The effect of Co doping on optical, structural and electrical properties of Ni1-xCoxO thin films has been successfully deposited on glass substrate by Sol–Gel Sping coating technique. The main objective of this research is to study the Ni1-xCoxO thin films to determine the optical gap energy by various methods and compare of calculated values. The transmission spectra show that the Ni1-xCoxO thin films have a good optical transparency in the visible region. The optical gap energy was varied between 3.8 and 4.05 eV, which was determined by various methods and equations. These are found in the drawn of A, A ², α, α ² (Ah ν) ² and (α h ν) ² as a function of the photon energy h ν, the suitable method to calculate the optical energy was observed for (Ah ν) ² versus h ν, but this method can not be related to the film thickness. The urbach energy of the Ni1-xCoxO thin films also was determined by the curves of LnA and Ln α as a function of photon energy h ν. The deduce by LnA versus h ν is also suitable to estimate the urbach energy. However, the Ni ₀.₉₆ Co ₀.₀₄ O thin films have a few defects with minimum value of urbach energy. XRD patterns of the Ni1-xCoxO thin films indicate that some films are polycrystalline with cubic structure. The electrical conductivity of our films is in the order of 8.2*10 ⁻³ (Ω.cm) ¹.

© 2017 Indian Academy of Sciences, Bengaluru.