Comparative Analysis of Different Grain Configurations for a Multi-thruster Kinetic Warhead

N. Ananthkrishnan,Hyun Ko,K. Sreesankar,R. Chakravarty,V.S. Renganathan 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5

The S-DACS multi-thruster warhead consists of 4 divert and 6 attitude thrusters fed from a common gas generator. Successful S-DACS intercept requires careful selection of the internal ballistics (grain configuration, chamber pressure, etc.), the sensors (seeker range, guidance law, etc.) as well as the external ballistics and sizing (booster diameter, S-DACS release velocity, flight time, maneuverability, etc.). These requirements and constraints are inter-dependent making the S-DACS mission analysis and sizing a difficult task. This work explores the connections between the choice of S-DACS grain configuration and sizing with the chamber pressure as a key parameter. Various parameters and center of gravity/ moment of inertia variations are compared for three different S-DACS grain configurations. Keywords: DACS, grain configuration, mission analysis

Propulsion System Modeling and Control of a Warhead with Multi-thruster Configuration

Rajtilok Chakravarty,Nachiket Wadwankar,N. Ananthkrishnan,V.S. Renganathan,Hyun Ko,Ji-Hyung Lee 한국추진공학회 2013 한국추진공학회 학술대회논문집 Vol.2013 No.12

A novel internal pressure controller is developed for a Kinetic Energy Interceptor (KEI) equipped with a multi-thruster configuration. To that end, first the propulsion system model for solid fuel with a tubular grain burning configuration is detailed. Subsequently the internal pressure control logic design and implementation is laid out and a closed loop simulation is successfully demonstrated where varying chamber pressure is demanded and met by the controller by varying the thruster throat areas appropriately.

Frequency of group A rotavirus with mixed G and P genotypes in bovines: predominance of G3 genotype and its emergence in combination with G8/G10 types

Yashpal S. Malik,Kuldeep Sharma,Nirupama Vaid,Somendu Chakravarti,K. M. Chandrashekar,Sanjay S. Basera,Rashmi Singh,Minakshi,Gaya Prasad,Baldev R. Gulati,Kiren N. Bhilegaonkar,Awadh B. Pandey 대한수의학회 2012 JOURNAL OF VETERINARY SCIENCE Vol.13 No.3

The present study describes the genotypic distribution of rotaviruses (RVs) in an Indian bovine population with unexpectedly higher proportions of G3 alone or in combination of G8/G10. PCR-genotyping confirmed that 39.4% (13/33) of the prevalent RVs were the G3 type while 60.6% (20/33) were dual G3G10 or G3G8 types. P typing revealed that 93.9% (31/33) of the samples were P[11] while 6.1% (2/33) possessed a dual P[1]P[11] type. Sequence analysis of the VP7 gene from G3 strains viz. B-46, 0970, and BR-133 showed that these strains had sequence identities of 90.5% to 100% with other bovine G3 strains. The highest identity (98.9% to 100%) was observed with RUBV3 bovine G3 strains from eastern India. The G3 strains (B-46, 0970, and BR-133) showed 97.5% to 98.8% sequence homologies with the Indian equine RV strain Erv-80. Phylogenetic analysis demonstrated that G3 strains clustered with bovine RUBV3 and J-63, and equine Erv-80 G3. Overall, these results confirmed that the incidence of infection by RVs with the G3 genotype and mixed genotypes in the bovine population was higher than previously predicted. This finding reinforces the importance of constantly monitoring circulating viral strains with the G3 genotype in future surveillance studies.

Evaluation of Shungit -A Non-Petro Performance Filler in Tyre Compounds and Studies with Silica filler

( A. Chakravarty ),( S. N. Chakravarty ) 한국고무학회 2007 고무기술 Vol.8 No.2

Shungit are natural composite materials having unusual structure, consist of uniformly distributed highly dispersed crystalline silicate particles in amorphous carbon matrix. It`s main component is fullerene like Shungit carbon (upto 80%). Studies with Shungit, a non petro based performance carbon filler, in additional quantity to Carbon black in typical automotive tyre carcass, bead & apex and tread compounds as well as replacement of silica filler have been carried out and reported here. Rheological / Rheometric studies, Physico-mechanical properties determination, Dynamic Mechanical analysis & Rubber Process Analyzer studies were carried out with different compounds. Compound mixing was carried out in Brabender Plasticoder. Technological properties of rubber compound with Shungit were considerably improved with respect to Mooney viscosity and time of premature vulcanization start (Scorch Safety). DMA analysis shows lower tan delta value with Shungit containing compound. RPA studies also indicate lower heat development and tan delta. Results indicate that Shungit can replace, fully or partly, Silica in tyre tread compounds containing Carbon black.

Genomic Analyses of Toll-like Receptor 4 and 7 Exons of Bos indicus from Temperate Sub-himalayan Region of India

Malik, Y.P.S.,Chakravarti, S.,Sharma, K.,Vaid, N.,Rajak, K.K.,Balamurugan, V.,Biswas, S.K.,Mondal, B.,Kataria, R.S.,Singh, R.K. Asian Australasian Association of Animal Productio 2011 Animal Bioscience Vol.24 No.7

Toll-like receptors (TLRs) play an important role in the recognition of invading pathogens and the modulation of innate immune responses in mammals. The TLR4 and TLR7 are well known to recognize the bacterial lipopolysaccharide (LPS) and single stranded (ssRNA) ligands, respectively and play important role in host defense against Gram-negative bacteria and ssRNA viruses. In the present study, coding exon fragments of these two TLRs were identified, cloned, sequenced and analyzed in terms of insertion-deletion polymorphism, within bovine TLRs 4 and 7, thereby facilitating future TLR signaling and association studies relevant to bovine innate immunity. Comparative sequence analysis of TLR 4 exons revealed that this gene is more variable, particularly the coding frame (E3P1), while other parts showed percent identity of 95.7% to 100% at nucleotide and amino acid level, respectivley with other Bos indicus and Bos taurus breeds from different parts of the world. In comparison to TLR4, sequence analysis of TLR7 showed more conservation among different B. indicus and B. taurus breeds, except single point mutation at 324 nucleotide position (AAA to AAM) altering a single amino acid at 108 position (K to X). Percent identity of TLR7 sequences (all 3 exons) was between 99.2% to 100% at nucleotide and amino acid level, when compared with available sequence database of B. indicus and B. taurus. Simple Modular Architecture Research Tool (SMART) analysis showed variations in the exon fragments located in the Leucine Rich Repeat (LRR) region, which is responsible for binding with the microbial associated molecular patterns and further, downstream signaling to initiate anti-microbial response. Considering importance of TLR polymorphism in terms of innate immunity, further research is warranted.

Tribofilm formation in ultrananocrystalline diamond film

Rani, R.,Sankaran, K.J.,Panda, K.,Kumar, N.,Ganesan, K.,Chakravarty, S.,Lin, I.N. Elsevier 2017 Diamond and related materials Vol.78 No.-

Friction and wear properties of ultrananocrystalline diamond (UNCD) films are found to be superior, and therefore it could be useful for various applications. However, understanding of the tribological properties with respect to boundary phase composition in this material is not yet well understood. Here, the grain boundary phases such as graphite and amorphous carbon (a-C) of UNCD films were tailored during the chemical vapor deposition process by altering the Argon and Nitrogen gases in CH<SUB>4</SUB> plasma medium. The significance of these grain boundary phases in UNCD film was discussed to explain the tribological properties. In run-in, friction coefficient was high in UNCD<SUB>Ar</SUB> film deposited in CH<SUB>4</SUB> (1%)/Ar plasma condition and it was decreased to lower value after longer sliding distance. However, ultrahigh wear resistance of this film was observed. Here, graphite and a-C phases were insignificant in the grain boundary region as evident from high resolution transmission electron microscope (HRTEM). Further, chemical bonding of these phases was quantitatively described by electron energy loss spectroscopy (EELS). In contrast, ultralow value of friction coefficient with significantly shorter run-in high friction regime was observed in UNCD<SUB>N</SUB> film deposited in CH<SUB>4</SUB> (6%)/N<SUB>2</SUB> plasma. Such a unique characteristic was described by the nanographite phase encasing the needle-like diamond grain of UNCD<SUB>N</SUB> film, forming core-shell granular structure. Atomic force microscopy (AFM) showed nucleation of two dimensional (2D) nanographite particles in the deformed wear track after run-in. This was possible due to the presence of core-shell granular structure in UNCD<SUB>N</SUB> film. Graphitic nature of the shell for needle-like diamond grains in the wear track was investigated by micro-Raman spectroscopy. Moreover, graphite and a-C tribofilm phase in the wear track was investigated by X-ray photoelectron spectroscopy (XPS) having spatial resolution micrometer scale. Needle-like diamond grains and graphite phase of tribofilm could be one of the primary reasons for the marked reduction in the friction coefficient.