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1

Thermal stresses due to non-uniform internal heat generation in functionally graded hollow cylinder

Rani P., Singh K., Muwal R.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 2

186--200

EN

Thermal stresses of a functionally graded hollow thick cylinder due to non-uniform internal heat generation are studied in this paper. Analytical solutions are obtained with radially varying properties by using the theory of elasticity. Thermal stresses distribution for different values of the powers of the module of elasticity and varying power law index of heat generation are studied. The results have been computed numerically and illustrated graphically.

2

Two dimensional deformation of a multilayered thermoelastic half-space due to surface loads and heat source

Vashishth A. K., Rani K., Singh K.

International Journal of Applied Mechanics and Engineering

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2020

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Vol. 25, no. 1

177--197

EN

This article deals with a 2-D problem of quasi-static deformation of a multilayered thermoelastic medium due tovsurface loads and heat source. The propagator matrix is obtained for the multilayered formalism of thermoelastic layers. Analytical solutions, in terms of the displacements, stresses, heat flux and temperature function, are obtained for normal strip and line loads, shear strip and line loads and strip and line heat sources. Numerical computation of the obtained analytical expressions is also done. The effects of layering have been studied. For the verification of the results, results of earlier studies have been obtained as particular cases of the present study.

3

Optimization and performance evaluation of microbial fuel cell by varying agar concentration using different salts in salt bridge medium

Singh K., Dharmendra

Archives of Materials Science and Engineering

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2020

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Vol. 101, nr 2

79--84

EN

Purpose: Comparative study of various agar-agar (C14H24O9) percentage and different salts concentration in the salt bridge is carried out to check the efficiency of microbial fuel cell. Design/methodology/approach: Dual chambered microbial fuel cell was used for the overall experiments. Anode and cathode chambers were made of 500 ml plastic jar. Salt bridge was fabricated with agar-agar technical and 3 M NaCl in a PVC pipe of 2 cm long. Chemical Oxygen Demand, pH and electrical conductivity of wastewater were examined. Oxygen was supplied in the cathode chamber using the aquarium pump. Voltage (open circuit voltage) was observed using digital multimeter. Graphite rods were used as anode and cathode electrodes. Findings: Salt bridge was constructed of 3 M NaCl with 5, 7.5, 10 and 12 percent variation of agar amounts in MFC. The maximum outputs were observed 301, 306, 325 and 337.25 mV with the variation of agar 5, 7.5, 10 and 12 percentages respectively as well as chemical oxygen demand (COD) removal efficiency was observed 47.92, 56.25, 52.08 and 64.58 percentages respectively. The optimum agar concentration was found to be 12 percent and a maximum voltage of 337.25 mV and COD removal of 64.58 percent was achieved. After the optimization of agar percentage two salts i.e., Sodium chloride and potassium chloride were analysed. This study also reveals that the NaCl salt bridge is more efficient than KCl salt bridge for the same agar concentration. The maximum voltage for NaCl and KCl were 319 and 312 mV respectively. Research limitations/implications: The amount of electricity production is low and field scale implementation is difficult using microbial fuel cell. The research is still on progress in this field. Originality/value: here is very little research with salt bridge and MFC. Comparative study of different mole of salt is available but agar variation is not yet studied.

4

BSIM3v3 to EKV2.6 Model Parameter Extraction and Optimisation using LM Algorithm on 0.18μ Technology node

Singh K., Jain P.

International Journal of Electronics and Telecommunications

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2018

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Vol. 64, No. 1

5--11

EN

The industry standard BSIM3v3 and BSIM4.0 have been replaced by BSIM6.0 compact MOSFET model for deep submicron technology node. The BSIM6.0 is next generation, defacto industry standard model for bulk MOSFET. This model is charge based which is continuous from weak to strong inversion of operation. The core of analytical and physical BSIM6 model[3] is charge, with drain current equation expressed in form of source(qs) and drain charge(qd). This model has all its governing equations continuous and can be used to develop design methodology using IC based approach. But its method of computing qs and qd is complicated which is different from Vittoz traditional charge calculation method. The continuous interpolation equation of drain current as adopted by EKV2.6 although is empirical but its compact expression is preferred by analog designer to get intuitive design guidance. BSIM6 is a combined effort by BSIM and EKV modeling groups based on charge based continuous equations. Although EKV2.6 model is not valid for deep submicron process as it only includes submicron short channel effects like velocity saturation (VS), vertical field mobility reduction (VFMR), Drain induced barrier lowering (DIBL), channel length modulation (CLM) etc. But it still offers some benefits to have first cut design methodology because of its much simplified analytical equations. The inversion coefficient (IC) has found extensive acceptance in designer community as it offers enhanced design elegance in EKV then more complicated BSIM model. This paper discuses first step in analog design process by extracted core EKV2.6 intrinsic model parameters from industry standard BSIM3v3 model on 0.18μ technology node. The 0.18μ technology is chosen as it is still more common technology node in analog circuit design. The model parameters are extracted for different bins and optimisation is done using nonlinear optimisation LM algorithm. The optimised EKV2.6 parameters are validated with current-voltage (I-V), intrinsic voltage gain (Avi) and Early voltage circuit parameter (VA) with BSIM3v3 model.

5

Experimental and analytical study of the side cutting ability of drill bits

Tellez C., Singh K., Miska S., Ozbayoglu E., Ziaja M.

AGH Drilling, Oil, Gas

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2018

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Vol. 35, no. 1

139--155

EN

Side cutting ability of a drill bit is an important factor to ensure successful directional/horizontal drilling. In this study, a mathematical model of a drill bit has been developed to investigate the side cutting ability of a drill bit. In addition to the theoretical model, the study is also supported by experimental work. Experiments have been conducted for both PDC and tri-cone rotary roller drill bits. Equilibrium equations for BHA in a curved wellbore were established. The expression of internal forces and moments along the drill-string, which are the state variables, are derived. Because of the simplicity and fast computation capability, transfer matrix method (TMM) was adopted to determine these variables. Experiments were conducted on an indoor Tulsa University Drilling Research Projects (TUDRP) full-scale drilling rig. Tests have been conducted using 6 inch and 8.5 inch PDC drill bits. In addition, 8.5 inch tri-cone bit were tested as well. Bent sub was installed above the drill bit to enhance the side force at the bit. During the experiments, weight on bit (WOB) and flow rate were kept constant. The torque was recorded by torque gage. It was observed that RPM has little influence on torque. As expected, the bit side cutting abilities, also referred to as bit steer-ability, were different for different bits. For quantitative comparisons, a dimensionless quantity has been introduced that measures the relative difference in torque with bent sub and without with respect to torque without bent sub. In all tests, the torque with bent subs was found to be greater than those without. Hence, the relative difference is always positive. The higher the relative difference, the poorer the side cutting ability. For drill bits with side cutting ability equal to that of face cutting, the dimensionless quantity becomes zero. In conclusion, the main outcome of this paper is a new method of measuring face and side cutting ability for PDC and tri-cone bits. A similar approach has been applied to the analysis of data from offset wells using a computer program to predict side forces and the corresponding torques. This in turn permitted us to calculate the relative difference in torque and assess the side cutting ability of the drill bits. A comprehensive study of the side cutting ability of a drill bits missing in the current literature. Considering the important role side cutting ability plays in directional drilling, a very innovative mathematical model has been proposed to study the same. Experimental tests have been conducted to verify the model. The model can be used to analyze directional data and obtain useful information from offset wells to enhance future drilling projects.

6

Measurement of 222Rn and 220Rn exhalation rate from soil samples of Kumaun Hills, India

Semwal P., Singh K., Agarwal T. K., Joshi M., Pant P., Kandari T., Ramola R. C.

Acta Geophysica

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2018

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Vol. 66, no. 5

1203--1211

EN

The source terms, i.e., exhalation and emanation from soil and building materials are the primary contributors to the radon ( 222Rn)/thoron ( 220Rn) concentration levels in the dwellings, while the ecological constraints like ventilation rate, temperature, pressure, humidity, etc., are the influencing factors. The present study is focused on Almora District of Kumaun, located in Himalayan belt of Uttarakhand, India. For the measurement of 222Rn and 220Rn exhalation rates, 24 soil samples were collected from different locations. Gamma radiation level was measured at each of these locations. Chamber technique associated with Smart Rn Duo portable monitor was employed for the estimation of 222Rn and 220Rn exhalation rates. Radionuclides ( 226Ra, 232Th and 40K) concentrations were also measured in soil samples using NaI(Tl) scintillation based gamma ray spectrometry. The mass exhalation rate for 222Rn was varying between 16 and 54 mBq/kg/h, while the 220Rn surface exhalation rate was in the range of 0.65–6.43 Bq/m2/s. Measured gamma dose rate for the same region varied from 0.10 to 0.31 µSv/h. Inter-correlation of exhalation rates and intra-correlation with background gamma levels were studied.

7

Color image encryption using affine transform in fractional Hartley domain

Singh P., Yadav A. K., Singh K.

Optica Applicata

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2017

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Vol. 47, nr 3

421--433

EN

A novel scheme for color image encryption using the fractional Hartley and affine transforms is proposed. An input color image is first decomposed in its RGB (red, green and blue) components. Each component is bonded with a random phase mask and then subjected to a fractional Hartley transform followed by affine transform. Thereafter, a second random phase mask is applied to each component before the final transformation by fractional Hartley transform resulting in a component-wise encrypted image. Finally, all three components are combined to give a single channel encrypted image. The scheme is validated with numerical simulations performed on a color image of size 256 × 256 × 3 pixels using MATLAB 7.14. The use of affine transform along with fractional Hartley transform adds to the security. The scheme is evaluated for its sensitivity to the parameters of the fractional Hartley and affine transforms. On analysing the plots of correlation coefficient and mean-squared-error, the scheme is found to be highly sensitive to the encryption parameters. Also, it is evaluated for its robustness against the usual noise and occlusion attacks. The proposed scheme is secure and robust owing to multiplicity of encryption parameters introduced through the type of transforms used.

8

Thermoelastic strain and stress fields due to a spherical inclusion in an elastic half-space

Singh K., Muwal R.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 4

1369--1380

EN

In this paper, closed form analytical expressions for thermoelastic strain and stress components due to a spherical inclusion in an elastic half-space are obtained. These expressions are derived in the context of steady-state uncoupled thermoelasticity using thermoelastic displacement potential functions. The thermal strain and stress fields are generated due to differences in the coefficients of linear thermal expansion between a subregion and the surrounding material. The strain and stress components for exterior points of the spherical inclusion are same as those of the center of dilatation. Variations of strain and stress components for exterior and interior points of the spherical inclusion are shown graphically.

9

Quasi-static Planar Deformation in av Medium Composed of Elastic and Thermoelastic Solid Half Spaces Due to Seismic Sources in an Elastic Solid

Vashisth A. K., Rani K., Singh K.

Acta Geophysica

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2015

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Vol. 63, no. 3

605--633

EN

A two-dimensional problem of quasi static deformation of a medium consisting of an elastic half space in welded contact with thermoelastic half space, caused due to seismic sources, is studied. Source is considered to be in the elastic half space. The basic equations, governed by the coupled theory of thermoelasticity, are used to model for thermoelastic half space. The analytical expressions for displacements, strain and stresses in the two half spaces are obtained first for line source and then for dip slip fault. The results for two particular cases, adiabatic conditions and isothermal conditions, are also obtained. Numerical results for displacements, stresses and temperature distribution have also been computed and are shown.

10

Response due to concentrated force in micropolar elastic solid with voids

Singh R., Singh K.

International Journal of Applied Mechanics and Engineering

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2014

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Vol. 19, no. 4

755--769

EN

The eigen value approach, following Laplace and Fourier transforms has been employed to find the general solution of the field equation in a micropolar elastic solid with voids for the plane strain problem. An application of an infinite space with impulsive force has been taken to illustrate the utility of the approach. The integral transformations have been inverted by using a numerical inversion technique to get result in physical domain. The result in the form of normal displacement, volume fraction, normal force stress, tangential force stress and tangential couple stress components has been obtained numerically and illustrated graphically to depict the effect of micropolarity and voids.

11

Eigen value approach in micropolar elastic medium with voids

Singh R., Singh K.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 2

521--536

EN

The eigen value approach, following the Laplace and Hankel transformation has been employed to find a general solution of the field equations in a micropolar elastic medium with voids for an axisymmetric problem. An infinite space with the mechanical source has been applied to illustrate the utility of the approach. The integral transformations has been inverted by using a numerical inversion technique to get the result in physical domain. The results in the form of normal displacement, volume fraction, normal force stress, tangential force stress and tangential couple stress components have been obtained numerically and illustrated graphically.

12

A modified convolution and product theorem for the linear canonical transform derived by representation transformation in quantum mechanics

Goel N., Singh K.

International Journal of Applied Mathematics and Computer Science

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2013

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Vol. 23, no. 3

685--695

EN

The Linear Canonical Transform (LCT) is a four parameter class of integral transform which plays an important role in many fields of signal processing. Well-known transforms such as the Fourier Transform (FT), the FRactional Fourier Transform (FRFT), and the FreSnel Transform (FST) can be seen as special cases of the linear canonical transform. Many properties of the LCT are currently known but the extension of FRFTs and FTs still needs more attention. This paper presents a modified convolution and product theorem in the LCT domain derived by a representation transformation in quantum mechanics, which seems a convenient and concise method. It is compared with the existing convolution theorem for the LCT and is found to be a better and befitting proposition. Further, an application of filtering is presented by using the derived results.

13

Simulation and sensitivity analysis for biodiesel production in a reactive distillation column

Agarwal M., Singh K., Chaurasia S. P.

Polish Journal of Chemical Technology

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2012

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Vol. 14, nr 3

59-65

EN

The conventional process for biodiesel production by transesterification is still expensive due to a need of high excess of alcohol required and its recovery by distillation. The use of a reactive distillation process can reduce the amount of alcohol in the feed stream as it works on a simultaneous reaction and separation. In the present study, a mathematical model has been developed for biodiesel production from triglycerides in a reactive distillation column, which has been validated with the reported data and CHEMCAD results. The effects of process parameters such as methanol to oil feed ratio, feed temperature, and reaction time have been investigated. The sensitivity analysis shows that yield of ester increases with methanol to oil ratio and number of stages, however, it decreases with fl ow rate. The MATLAB simulated results show that methanol to oil molar ratio of 5:1 produces 90% (by wt.) of methyl ester in a residence time of 4.7 minutes.

14

Response due to mechanical and thermal sources in micropolar generalized thermoelastic medium

Singh R., Singh K., Kumar V.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 1

107-128

EN

The eigen value approach, following the Laplace and Fourier transformation, is employed to find the general solution of the field equation in a micropolar generalized thermoelastic medium for a plane strain problem. An application of an infinite space with an impulsive mechanical source and thermal source is taken to illustrate the utility of the approach. The integral transformation is inverted by using a numerical inversion technique to get a result in the physical domain. The result in the form of normal displacement, normal force stress, tangential force stress, tangential couple stress and temperature field components is obtained numerically and illustrated graphically. A special case of a thermoelastic solid also deduced.

15

Parametric studies and simulation of PSA process for oxygen production from air

Beeyani A., Singh K., Vyas R., Kumar S., Kumar S.

Polish Journal of Chemical Technology

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2010

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Vol. 12, nr 2

18-28

EN

A numerical simulation and parametric studies for the separation of air using 5A zeolite for the production of oxygen are presented for a basic two bed pressure swing adsorption (PSA) process. The simulation is based on an in-house program 'PSASOL' developed in MATLABŽ. The transient process of PSA has been described by a set of partial differential equations, which were solved using a finite difference method. Simulation results have been validated with the experimental data from literature. Based on the simulation results, an optimal set of operational parameter values has been obtained for the PSA bed. The values of the optimal parameters, viz. adsorption pressure, cycle time, feed rate, and product rate have been found to be 2.5 atm, 150 s, 15 cm3/s, and 2.55 cm3/s, respectively. For the optimal conditions, purity of 95.45% and recovery of 77.3% have been achieved. It has also been found that a longer tubular unit with the length to diameter (L/D) ratio of 10.5 is advantageous. The estimated pressure drop across the bed has been found to be negligible. Power consumption and productivity have also been computed.

16

Hisslers observed during daytime in a low latitude ground station

Singh K., Patel R., Kumar B., Altaf M., Ganai P., Singh A., Singh R., Lalmani

Acta Geophysica

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2009

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Vol. 57, no. 2

536-547

EN

The observation of hisslers during daytime at low latitude station Jammu, India, is reported. The hissler elements are quasi-periodic falling tones observed during the period of hiss activity and appear in minutelong sequences with average spacing between individual elements of the order of 0.15 s. Hissler elements exhibit almost no dispersion and no complex internal structure in slope and intensity, and successive hissler elements do not overlap in time. It seems that the reported hisslers might have propagated in prolongitudinal mode.