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فهرست مطالب نویسنده:

s. kumar∗

  • R. Suresh *, A. G. Joshi, M. Manjaiah, S. Kumar, K. N. Bharath

    The microstructure, mechanical and tribological properties of titanium carbide particles reinforced Al2024 metal matrix composites (Al MMCs) were investigated. Fractography analysis of tensile test specimen revealed that debonding was prominent in 3% TiC reinforced Al MMCs, while clevage pattern failure was pronounced in 6% and 9% TiC reinforced MMCs. Tribological property was studied as sliding wear behaviour of MMCs. ANOVA analysis was employed to understand the effect of parameters, interaction effects was studied through response surface plots. Further, regression model was developed to correlate process parameters and wear. The worn surface analysis shown the formation of ridges and parallel furrows on surface in sliding direction. Al/TiC composites exhibited better mechanical properties and wear resistance compared to Al2024 alloy. The optimization of wear for its minimum value was achieved through spotted hyena optimization algorithm. The wear loss at optimized parameter was validated through experimental value and compared with Taguchi’s technique.

    Keywords: Metal Matrix Composite, Sliding Wear, Taguchi, Spotted Hyena Optimization
  • S. Kumar *, M. J. Cervantes, B. K. Gandhi
    The hydraulic turbines, especially Francis turbines, frequently run at part load (PL) conditions to meet the dynamic energy needs. The flow field at the runner exit changes significantly with a change in the operating point. At PL, flow instabilities such as the Rotating Vortex Rope (RVR) form in the draft tube of the Francis turbine. The present paper compares the features of the velocity and vorticity field of the Francis turbine draft tube at the best efficiency point (BEP) and PL operations using the Proper Orthogonal Decomposition (POD) of the 2D-PIV data. The POD analysis decomposes the flow field into coherent and incoherent structures describing the spatiotemporal behavior of the flow field. A visual representation of the coherent structures and the turbulent length scales in the flow field is extracted and analyzed for BEP and PL, respectively. The study highlights the salient features of the draft tube flow field, which differentiate the BEP and PL operation. The fast Fourier transform of the temporal coefficients confirms the presence of RVR frequency (0.29 times the runner frequency) at PL. The phase portraits of different modes elucidate the relationship between different harmonics of the RVR frequency at PL.
    Keywords: POD, Part load, Vortex rope, Dissipation, Francis turbine
  • High Temperature Corrosion Behavior of High Velocity Oxy Fuel Sprayed NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 Composite Coatings on ASTM SA213-T22 Steel in a Coal-fired Boiler Environment
    V. G. Patil *, B. Somasundaram, S. Kandaiah, M. Ramesh, S. Kumar
    High-velocity oxy fuel (HVOF) sprayed coatings can improve the corrosion resistance of bare ASTM SA213-T22 boiler steel. In this report, we have investigated the NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 composite coatings were deposited on bare ASTM SA213-T22 boiler steel for corrosion protection. High-temperature corrosion studies were conducted in a molten salt (Na2SO4-60%V2O5) environment at 700ºC under thermo-cyclic conditions. The as-sprayed composite coatings are characterized for microstructure and mechanical properties. The thermo-gravimetric method was utilized to understand the kinetics of corrosion. Characterization of the corrosion products was examined by using scanning electron microscope (SEM)/ Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The obtained results suggest both the composite coatings are favorable to corrosion resistance over the bare ASTM SA213-T22 boiler steel. The NiCrMoFeCoAl-30%Cr2O3 composite coating was concluded to present a superior corrosion resistance in the high-temperature corrosion environment because of the uniform distribution of the composite coating matrix and the development of protective protection Cr2O3 in the scale. The molten salt heat-treated chromium oxide containing coating shows good corrosion stability than the silica composite. This could be attributed to the high temperature assisted formation metal chromates, chromites and oxide layers.
    Keywords: Hot Corrosion, High-velocity Oxy Fuel, Thermogravimetric analysis, Thermal spraying, oxide scale
  • Dharmendra Yadav, S. R. Singh, S. Kumar, L. E. Cardenas-Barron *
    This research paper builds a manufacturer-retailer integrated inventory model to compute jointly the optimal values for the order quantity, the lead time, the reorder point and the number of shipments taking into consideration the effect of learning-forgetting phenomenon on the setup cost. The fabrication process of manufacturer is not perfect and certain level of product quality can attain with an additional cost. Service level constraint is incorporated into the inventory model to evade the backorder which gives negative impact to company reputation. The lead time is reduced with the help of crashing cost. The proposed inventory model is illustrated with the help of an example. From this example, it is detected that centralized decision is better than decentralized one. It is also observed from the analysis that players have to compromise with their profit if they decide to increment the service level and quality of the product. Due to the effect of learning-forgetting on the setup cost, profit of the centralized system increases.
    Keywords: Integrated inventory model, learning-forgetting, imperfect manufacturing process, lead-time, service level constraint
  • S. Kumar *, Singh M. K., G. Dobhal, D. Saini, G. Bhatnagar
    Security solutions of stereo images are always a major concern during the transmission and communication. In this manuscript, a simple yet efficient framework for encrypting stereo images is formulated using discrete cosine transform (DCT), generalized logistic map, Schur decomposition and magic square method. The framework initiated with the integration of DCT and generalized logistic map to unify both pair of images. This unified image is then encrypted using the Schur decomposition and magic square method. The various experiments and analysis have been done to explore the validity, proficiency and performance of the purport framework.
    Keywords: Stereo Image, Encryption, Decryption, Discrete Cosine Transform, Generalize Logistic Map, Schur Decomposition
  • R. Prasad, M. A. Akyol*, P. K. Singh, S. Kumar

    The paper deals with the notion of quasi bi-slant submersions from almost contact metric manifolds onto Riemannian manifolds. These submersions are generalization of hemi-slant submersions and semi-slant submersions. We study such submersions from Kenmotsu manifolds onto Riemannian manifolds and discuss some examples of it. In this paper, we also study the geometry of leaves of distributions which are involved in the definition of the submersion. Further, we obtain the conditions for such submersions to be integrable and totally geodesic.

    Keywords: Kenmotsu manifold, slant submersion, bislant submersion, quasi bi-slant submersion, vertical distribution
  • K. Jain *, S. Kumar, S. Deswal

    Present work is concerned with the analysis of transient wave phenomena in a piezo-thermoelastic medium with diffusion, fiber reinforcement and two-temperature, when an elastic wave is made incident obliquely at the traction free plane boundary of the considered medium. The formulation is applied under the purview of generalized theory of thermoelasticity with one relaxation time. The problem is solved analytically and it is found that there exists four coupled quasi waves: qP (quasi-P ), qMD (quasi mass diffusion), qT (quasi thermal) and qSV (quasi-SV ) waves propagating with different speeds in a two-dimensional model of the solid. The amplitude ratios, phase velocities and energy ratios for the reflected waves are derived and the numerical computations have been carried out with the help of MATLAB programming. Effect of presence of diffusion is analyzed theoretically, numerically and graphically. The number of reflected waves reduce to three in the absence of diffusion as qMD wave will disappear in that case which is physically admissible. Influence of piezoelectric effect, two temperature and anisotropy is discussed on different characteristics of reflected waves such as phase velocity and reflection coefficients. It has been verified that there is no dissipation of energy at the boundary surface during reflection. Thus, the energy conservation law holds at the surface. Finally, all the reflection coefficients are represented graphically through 3D plots to estimate and highlight the effects of frequency and angle of incidence.

    Keywords: Generalized thermoelasticity, Piezo-thermoelasticity, Fiberreinforcement, Two-temperature, Diffusion, Reflection phenomena
  • S. Kumar, R. Singh, R. Jaiswal, A. Kumar *

    Electron beam welding has shown a remarkable job in the space industry for welding of components. It is performed under a vacuum environment that eliminates foreign matter such as hydrogen, oxygen, and other gases. Joining of similar and dissimilar materials is the main advantage of electron beam welding with high depth to width ratio as well as sharp focus at the point where parts are to be welded. EBW reduces the HAZ (heat affected zone), making it one of the most acceptable welding processes. In this study, evaluation of the effect of joining parameters on the mechanical strength and hardness is conducted using Minitab software. The strength of the electron beam weld varies with welding parameters. Therefore, correct and optimized parameter selection imparted the highest welding strength. Some welding parameters directly affect weld strength; those were judiciously selected for our experiments. Therefore, 3x3 arrays were selected for investigation on the microhardness and ultimate tensile strength of Fe49Co2V. Three levels and four factors are chosen for analysis. The input parameters are selected as Accelerating Voltage (KV), Welding Speed (mm/min), Beam Current (mA), and Focus Current (mA). This study reveals the maximum welding strength obtained at High Voltage (55 KV), High Beam current (7 mA), Moderate Speed (20 mm/min), and moderate focus current (2365 mA). Similarly, the microhardness obtained at a High Voltage (55 KV), High beam current (7 mA), high welding speed (30 mm/min) and minimum focus current (2210 mA). This study reveals the maximum welding strength obtained at High Voltage (55KV), High beam current (7mA), moderate speed (20 mm/min) & moderate focus current (2365mA). Similarly, the micro-hardness obtained at a High Voltage (55KV), High beam current (7mA), and the high welding speed (30 mm/min) & minimum focus current (2210mA).

    Keywords: Electron Beam Welding, Heat affected zone, optimization
  • S. Kumar *, S. Deswal
    This study aims to examine the ability of free floating aquatic plants to remove phosphorus and to predict the reduction of phosphorus from rice mill wastewater using soft computing techniques. A mesocosm study was conducted at the mill premises under normal conditions, and reliable results were obtained. Four aquatic plants, namely water hyacinth, water lettuce, salvinia, and duckweed were used for this study. The growth of all the plants was inhibited in rice mill wastewater due to low pH, high chemical oxygen demand, high conductivity, and high phosphorus concentration. Subsequently, a 1:1 ratio of mill water to tap water was used. A control was maintained to assess the aquatic plant technology. In this study, the aquatic plants reduced the total phosphorus content up to 80 % within 15 days. A comparison between three modeling techniques e.g. Artificial neural network (ANN), Random forest (RF) and M5P has been done considering the reduction rate of total phosphorus as predicted variable. In this paper, the data set has been divided in two parts, 70 % is used to train the model and residual 30 % is used for testing of the model. Artificial neural network shows promising results as compared to random forest and M5P tree modelling. The root mean square error (RMSE) for all the three models is observed as 0.0162, 0.0204 and 0.0492 for ANN, RF and M5P tree, respectively.
    Keywords: aquatic plants, rice mill, modelling, Water hyacinth, Total phosphorus
  • I. Singh, S. Kumar∗

    We present here, three- dimensional Haar wavelet based method for solving well known two- dimensional telegraph equation, by approximating higher order mixed derivatives by a series of higher dimensional Haar wavelet functions, which are integrated subsequently to get wavelet approximation of the solution. Numerical examples have been solved to illustrate the accuracy and efficiency of the proposed Haar wavelet method. High accuracy of the results even in the case of a small number of collocation points have been observed.

    Keywords: Two- dimensional telegraph equation, Haar wavelet, Function approximations, Error analysis
  • S. Kumar *

    The present article serves the purpose of pursuing Geometrization of heat flow on volumetrically isothermal manifold by means of RF approach. In this article, we have analyzed the evolution of heat equation in a 3-dimensional smooth isothermal manifold bearing characteristics of Riemannian manifold and fundamental properties of thermodynamic systems. By making use of the notions of various curvatures, we have discussed different types of heat diffusion equation for our volumetrically isothermal manifold and its isothermal surfaces. Finally, we have delineated a heat diffusion model for such isothermal manifold and by decomposing it into isothermal surfaces we have developed equation for heat diffusion.

    Keywords: Ricci flow
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