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Mehta, R.C. Techno-Press 2020 Advances in aircraft and spacecraft science Vol.7 No.4
A forward-facing aerospike attached to a payload fairing of a satellite launch vehicle significantly alters its flowfield and decreases the aerodynamic drag in transonic and low supersonic speeds. The present payload fairing is an axisymmetric configuration and consists of a blunt-nosed body along with a conical section, payload shroud, boat tail and followed by a booster. The main purpose of the present numerical simulations is to evaluate flowfield and assess the performance of aerodynamic drag coefficient with and without aerospike attached to a payload fairing of a typical satellite launch vehicle in freestream Mach number range 0.8 ≤ M<sub>∞</sub> ≤ 3.0 and freestream Reynolds number range 33.35 × 10<sup>6</sup>/m ≤ Re<sub>∞</sub> ≤ 46.75 × 10<sup>6</sup>/m whichincludes the maximum aerodynamic drag and maximum dynamic conditions during ascent flight trajectory of the satellite launch vehicle. A numerical simulation has been carried out to solve time-dependent compressible turbulent axisymmetric Reynolds-averaged Navier-Stokes equations. The closure of the system of equations is achieved using the Baldwin-Lomax turbulence model. The aerodynamic drag reduction mechanism is analysed employing numerical results such as velocity vector plots, density and Mach contours in conjunction with the experimental flow visualization pictures. The variations of wall pressure coefficient over the payload fairing with and without aerospike are exhibiting different kind of flowfield characteristics in the transonic and low supersonic speeds. The numerically computed results are compared with schlieren pictures, oil flow patterns and measured wall pressure distributions and exhibit good agreement between them.
A micromachined electrochemical sensor for free chlorine monitoring in drinking water
Mehta, A.,Shekhar, H.,Hyun, S.H.,Hong, S.,Cho, H.J. IWA Publishing 2006 Water Science & Technology Vol.53 No.4
<P>In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification.</P>
Analysis of payload compartment venting of satellite launch vehicle
Mehta, R.C. Techno-Press 2017 Advances in aircraft and spacecraft science Vol.4 No.4
The problem of flow through the vent is formulated as an unsteady, nonlinear, ordinary differential equation and solved using Runge-Kutta method to obtain pressure inside payload faring. An inverse problem for prediction of the discharge coefficient is presented employing measured internal pressure of the payload fairing during the ascent phase of a satellite launch vehicle. A controlled random search method is used to estimate the discharge coefficient from the measured transient pressure history during the ascent period of the launch vehicle. The algorithm predicts the discharge coefficient stepwise with function of Mach number. The estimated values of the discharge coefficients are in good agreement with differential pressure measured during the flight of typical satellite launch vehicle.
An Energy-Efficient MAC Protocol in Wireless Sensor Networks: A Game Theoretic Approach
Mehta, S.,Kwak, K. S. Hindawi Publishing Corporation 2010 Eurasip Journal on Wireless Communications and Net Vol.2010 No.-
<P>Game Theory provides a mathematical tool for the analysis of interactions between the agents with conflicting interests, hence it is well suitable tool to model some problems in communication systems, especially, to wireless sensor networks (WSNs) where the prime goal is to minimize energy consumption than high throughput and low delay. In this paper, we use the concept of incomplete cooperative game theory to model an energy efficient MAC protocol for WSNs. This allows us to introduce improved backoff algorithm for energy efficient MAC protocol in WSNs. Finally, our research results show that the improved back off algorithm can improve the overall performance as well as achieve all the goals simultaneously for MAC protocol in WSNs.</P>
Graphene quantum dot modified screen printed immunosensor for the determination of parathion
Mehta, J.,Bhardwaj, N.,Bhardwaj, S.K.,Tuteja, S.K.,Vinayak, P.,Paul, A.K.,Kim, K.H.,Deep, A. Academic Press 2017 Analytical biochemistry Vol.523 No.-
<P>The widespread use of pesticides has immense effect on increased crop productions. However, they are also responsible for posing detrimental health hazards and/or for contaminating the environment with chemical residues. A routine and an on-field detection of pesticide residues in different food, water, and soil samples has become a need of the hour for which biosensors can offer a viable alternative. The present work reports a functionalized graphene quantum dot (GQD) based screen printed electro-chemical immunosensor for the detection of parathion. The application of GQDs has permitted the realization of a sensitive, robust, and reproducible sensor unlike those carried out earlier for the similar purposes. This immunosensor exhibited a dynamic linear response for parathion within the range of 0.01 -10(6) ng/L with a very low detection limit of 46 pg/L. According to the analysis of potential interferences, the proposed sensor was specifically detecting parathion even in the presence of its metabolite, paraoxon. The investigations of the proposed sensing approach with respect to stability, response reproducibility, and regeneration have fully supported its potential practical applicability. (C) 2017 Elsevier Inc. All rights reserved.</P>
Mehta, Dhaval Tushar,Annamalai, Thangavelu,Ramanathan, Arvind Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.11
Background: The epidermal growth factor receptor (EGFR) plays a vital role in the activation and inactivation of receptor tyrosine kinases. Mutations in exons 19 and 21 of EGFR are commonly found to be associated with non small cell lung carcinoma and triple negative breast cancer, enhancing sensitivity to EGFR targeting chemotherapeutic agents. Since amplification and prolonged activation of EGFR molecules have been identified in oral squamous cell carcinomas (OSCC), we investigated whether OSCCs carried mutations in exons 19 and 21 of EGFR to their incidence. Materials and Methods: Tumor chromosomal DNA isolated from forty surgically excised oral squamous cell carcinoma tissues was subjected to PCR amplification with intronic primers flanking exons 19 and 21 of the EGFR gene. The PCR amplicons were subsequently subjected to direct sequencing to elucidate the mutation status. Results: Data analysis of the EGFR exon 19 and 21 coding sequences did not show any mutations in the forty OSCC samples that were analyzed. Conclusions: To the best of our knowledge, this is the first study to have investigated the genetic status of exons 19 and 21 of EGFR in Indian OSCCs and identified that mutation in EGFR exon 19 and 21 may not contribute towards their genesis. The absence of mutations also indicates that oral cancerous lesions may not be as sensitive as other cancers to chemotherapeutic agents targeting EGFR.
Mehta, Sanjay,Saadeghvaziri, M.A. Techno-Press 1998 Structural Engineering and Mechanics, An Int'l Jou Vol.6 No.7
An overview of an analytical model to predict mortar joint failure in unreinforced masonry (URM) structures is presented. The validity of the model is established by comparison with experimental results at element level as well as structure level. This model is then used to study the behavior of URM walls and two commonly used retrofitting schemes. Finally, effectiveness of the two retrofitting schemes in increasing strength and stiffness of existing URM walls is discussed.
Recent advances in enzyme immobilization techniques: Metal-organic frameworks as novel substrates
Mehta, J.,Bhardwaj, N.,Bhardwaj, S.K.,Kim, K.H.,Deep, A. Elsevier Publishing Company 2016 Coordination chemistry reviews Vol.322 No.-
<P>In the past few years, metal organic frameworks (MOFs) have drawn increasing research interest as bioimmobilization support materials. The unique properties of MOFs, including tunable porosity, desirable functionality, extremely high surface area, and chemical/thermal stability, have motivated a considerable interest in exploiting them as a potential matrix for enzyme immobilization. Improvements in the biocatalyst efficiency, promising recyclability, enhanced accessibility to active sites, and a high loading capacity are the main features of the novel MOF-enzyme supports. This review aims to cover the recent progress in the application of MOFs as enzyme immobilization supports. We discuss different approaches used in the development of MOF-enzyme biocatalytic supports, such as surface adsorption, diffusion, and in-situ encapsulation. The trends in current developments and the significance of each strategy are critically reviewed in this paper. (C) 2016 Elsevier B.V. All rights reserved.</P>