Subodh Kumar
@sru.edu.in
Assistant Professor
SR University
EDUCATION
Technical Education:
Qualification University/Institution Year of Passing Specialization % Marks
Ph.D. IIT (ISM) Dhanbad 2020 Mechanical Design --
M.E. BIT Mesra, Ranchi 2012 Applied Mechanics 80.00%
B.E. OIST, Bhopal 2010 Automobile Engineering 77.19%
RESEARCH, TEACHING, or OTHER INTERESTS
Mechanical Engineering, Aerospace Engineering, Mechanics of Materials, Civil and Structural Engineering
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Saurabh Rai, Subodh Kumar, Rajesh Singh, and Ankit gupta
Springer Science and Business Media LLC
Subodh Kumar, Ankit Gupta, V R Shanmukhasundaram, Jay Prakash Srivastava, and Prashant Choudhary
IOP Publishing
Subodh Kumar and Prasun Jana
Elsevier BV
Saurabh Rai, Subodh Kumar, and Ankit Gupta
CRC Press
Subodh Kumar and Prasun Jana
Elsevier BV
Subodh Kumar, Vinayak Ranjan, and Prasun Jana
Elsevier BV
Ram Kishor Singh, Subodh Kumar, and R.P. Sharma
Wiley
We propose a theoretical model for the generation of electromagnetic waves in the terahertz (THz) frequency range by the optical rectification of a Gaussian laser pulse in a plasma with an applied static electric field transverse to the direction of propagation. A Gaussian laser pulse can exert a transverse component of the quasi‐static ponderomotive force on the electrons at a frequency in the THz range by a suitable choice of the laser pulse width. This nonlinear force is responsible for the density oscillation. The coupling of this oscillation with the drift velocity acquired by electrons due to the applied static electric field leads to the generation of a nonlinear current density. A spatial Gaussian intensity profile of the laser beam enhances the generated THz yield by many folds as compared to a uniform spatial intensity profile.
Ram K. Singh, Subodh Kumar, and Ram P. Sharma
Institute of Electrical and Electronics Engineers (IEEE)
This paper presents an investigation of terahertz (THz) wave generation by optical rectification of a Gaussian laser pulse propagating in plasma having periodic density perturbation in the presence of an externally applied static magnetic field in the axial direction. The nonuniform intensity of laser pulse leads to the generation of quasi-static ponderomotive force. The electrons acquire nonlinear oscillatory velocity under the influence of the force. This velocity, on coupling with the density perturbation, induces a nonlinear current density in the radial direction. This nonlinear current density drives a wave, the frequency of which depends on the pulse duration of the laser. The frequency falls in the THz range if the pulse duration of the laser is chosen thoughtfully. For the resonant excitation of the radiation, phase matching is required, which is provided by the periodic density perturbation. Axially applied external magnetic field can be utilized as a controlling parameter to enhance the nonlinear coupling and the yield of the generated wave. The effect of the axial magnetic field on the generated THz intensity is investigated. Variations in THz radiation intensity as functions of the density ripple amplitude and background plasma density have also been studied.
Md. Imran Ali, Subodh Kumar, and Vinayak Ranjan
IEEE
This study is concerned with the effect of volume fraction index and mass ratio on natural frequency of clamped functionally graded plate having different aspect ratio with point mass attached at the center using Rayleigh-Ritz method. According to the power law distribution, the mechanical properties of the functionally graded plate are continuously varying along the thickness of the plate. Rayleigh-Ritz procedure of energy variation formulation is used to obtain the eigen equation. Some of the results of natural frequencies associated with functionally graded plates are validated with the published results.
Subodh Kumar, Ram Kishor Singh, and R. P. Sharma
IOP Publishing
Terahertz (THz) generation by optical rectification of a laser beam having spatially super-Gaussian and temporally Gaussian intensity profile is investigated when it is propagating in a pre-formed rippled density plasma. The quasi-static ponderomotive force which is generated due to the variation in intensity of laser pulse leads to a nonlinear current density in the direction transverse to the direction of propagation which drives a radiation. The frequency of this radiation falls in the THz range if the pulse duration of the laser is chosen suitably. The density ripple provides the phase matching. The yield of generated THz has been compared when the phase matching is exact and when there is slight mismatch of phases. The variation in the intensity of the generated THz with the index of super-Gaussian pulse has also been studied.
Subodh Kumar, Ram K. Singh, and Ram P. Sharma
Institute of Electrical and Electronics Engineers (IEEE)
THz generation by nonlinear mixing of two coaxial Super-Gaussian laser beams, propagating in rippled density plasma with an axially applied static magnetic field, is investigated. The ponderomotive force which arises due to nonuniform spatial intensity profiles of laser beams, imparts a nonlinear oscillatory velocity at beat wave frequency to electrons. This oscillatory velocity couples with the preformed density ripple to generate a nonlinear current density driving a radiation. Frequencies of lasers are chosen such that the beat frequency lies in the terahertz region. The density ripple provides the phase matching for resonant excitation and the axial static magnetic field is utilized to enhance the nonlinear coupling. Numerical results show that the yield of the generated THz amplitude enhances with increase in index of super-Gaussian lasers as well as the magnitude of the axially applied static magnetic field.
Subodh Kumar, Ram K. Singh, and Ram P. Sharma
Institute of Electrical and Electronics Engineers (IEEE)
Terahertz (THz) generation by an intense femtosecond Gaussian laser pulse (Gaussian in space and time) in rippled density plasma has been investigated in the relativistic regime. A component of ponderomotive force is exerted on electrons due to the variation in intensity in the direction transverse to the laser propagation that results in a transient current driving a radiation. If the pulsewidth of the laser is suitably chosen, the frequency of this generated radiation falls in the THz region. The necessary condition for phase matching is provided by the density ripple. The effects of transient focusing of the laser pulse on the generated THz amplitude have also been studied. Numerical simulations show a significant increase in the THz field strength with occurrences of relativistic ponderomotive self-focusing.
Subodh Kumar, Ram Kishor Singh, and R. P. Sharma
AIP Publishing
Terahertz (THz) generation by beating of two co-axial Gaussian laser beams, propagating in ripple density plasma, has been studied when both ponderomotive and relativistic nonlinearities are operative. When the two lasers co-propagate in rippled density plasma, electrons acquire a nonlinear velocity at beat frequency in the direction transverse to the direction of propagation. This nonlinear oscillatory velocity couples with the density ripple to generate a nonlinear current, which in turn generates THz radiation at the difference frequency. The necessary phase matching condition is provided by the density ripple. Relativistic ponderomotive focusing of the two lasers and its effects on yield of the generated THz amplitude have been discussed. Numerical results show that conversion efficiency of the order of 10−3 can be achieved in the terahertz radiation generation with relativistic ponderomotive focusing.
Subodh Kumar, Ram Kishor Singh, Monika Singh, and R. P. Sharma
Cambridge University Press (CUP)
AbstractThe effect of self-focusing and defocusing on terahertz (THz) generation by amplitude-modulated Gaussian laser beam in rippled density plasma is investigated. A stronger transient transverse current is generated by transverse component of ponderomotive force exerted by laser on electrons that drives radiation at the modulation frequency (which is chosen to be in the THz domain) because of the variation in intensity in the direction transverse to the laser propagation. Numerical simulations indicate the enhancement of THz yield by many folds due to self-focusing of laser beam in comparison with that without self-focusing. The transient focusing of laser beam and its effect on the generated THz amplitude has also been studied.
Shobhana Singh and Subodh Kumar
Informa UK Limited
An analytical moisture diffusion model which considers the influence of external resistance to mass transfer is developed. The methodology to determine constant and variable moisture diffusion coefficients, Deff is proposed. A laboratory model of mixed-mode solar dryer is constructed to perform 16 experiments for different performance dependent variables under simulated indoor conditions. The potatoes (Solanum tuberosum) of Kufri Safed variety have been chosen as the test food product. The range of variables investigated is absorbed thermal energy (150–750 W/m2); air mass flow rate (0.009–0.022 kg/s); loading density (1.08–4.33 kg/m2) and sample thickness (5–18 mm). The efficiency results have been analysed to identify the value of each process variable leading to optimal operation of dryer. The study reveals that dryer with sample thickness of 8 mm and loading density of 4.33 kg/m2 can operate optimally for absorbed energy of 450 W/m2 and air mass flow rate of 0.017 kg/s.
Shobhana Singh and Subodh Kumar
Elsevier BV
Shobhana Singh and Subodh Kumar
Elsevier BV
Shobhana Singh and Subodh Kumar
Elsevier BV
Shobhana Singh and Subodh Kumar
Elsevier BV
Subodh Kumar and Shobhana Singh
IEEE
In present experimental investigation, a modest attempt is made to study the influence of load density and size of food product on drying efficiency of solar dryer. In order to achieve this objective, the laboratory model of mixed-mode solar dryer is fabricated and tested under indoor simulated conditions. Experiments have been performed on dryer with cylindrical potato samples of different thicknesses (5, 8 10 and 18 mm) and loading density (1.08, 2.16, 3.24 and 4.33 kg/m2 of food sample tray area) under forced air circulation. The air mass flow through dryer system is kept constant at 0.011 kg/s (1.3 m/s). Experimental variation of food product moisture content with drying time data have been plotted and analyzed for a wide range of product size and loading density. Results of experimental investigation reveal that the load density and food product size have significant effect on drying efficiency. It is also found that load density has an increasing influence on efficiency whereas the opposite trend is observed for food product size. Sensitivity analysis results indicate that both the variables are equally sensitive to overall efficiency of the dryer.
Shobhana Singh and Subodh Kumar
IEEE
In present study, the simple test procedure is proposed for thermal performance evaluation of solar dryers in general and mixed mode dryer in particular. Steady state heat balance concept has been applied to the absorber surface of collector-dryer assembly for identification of a dimensionless parameter called Dryer Performance Ratio (DPR) representing the effectiveness of a dryer. No-load experiments on mixed mode dryer have been performed for natural and forced air circulation under indoor controlled conditions. The dryer is tested for a wide range of operating conditions of absorbed thermal energy (300–800W/m2) and air mass flow rate (0.009–0.026 kg/s). Comparison of DPR values obtained for natural and forced air circulations indicates a significant performance improvement of 94% at the minimum air flow rate of 0.009 kg/s. It is also found that there is sharp rise in DPR by 31% is observed when airflow is increased from 0.009 to 0.017 kg/s and thereafter a marginal increase of 4% can be noticed for air flow enhancement of ∼ 53%. Another important finding of present study relates to invariable DPR values obtained for a wide range of absorbed energy and ambient air temperature data irrespective of air circulation mode adopted for a dryer.
P. P. Tripathy and Subodh Kumar
Informa UK Limited
Rehydration experiments at the temperatures of 40°, 50°, and 60°C were performed with potato samples dried simultaneously under mixed-mode solar dryer and open air sun. Results of the investigation reveal that the ability of water absorption of dried product is influenced most by the rehydration temperature, followed by sample geometry and method of drying. Higher rehydration temperature causes faster moisture absorption in dried product. The present analysis also indicates that both cylindrical samples and mixed-mode solar drying exhibit larger values of proposed rehydration indices, better color retention during drying, and greater texture hardness, demonstrating the higher acceptability of these samples by the consumers.
G.N. Tiwari, Om Prakash, and Subodh Kumar
Elsevier BV