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Gangal A.C.,Indian Institute of Technology Bombay | Edla R.,Indian Institute of Technology Bombay | Iyer K.,Indian National Environmental Engineering Research Institute | Biniwale R.,Indian National Environmental Engineering Research Institute | And 2 more authors.
International Journal of Hydrogen Energy | Year: 2012

Chemical hydrides due to their light weight and high storage capacity are considered to be promising hydrogen storage materials for both mobile and stationary applications. Ammonia Borane (AB) is a novel material with very high hydrogen content (19.6 wt %) per mass. The decomposition of AB takes place in three steps at desorption temperatures of about 100 °C, 140 °C and above 1000 °C respectively releasing 1 mol of hydrogen in each step. The major obstacle towards the use of AB as a hydrogen store is its irreversibility and slow kinetics. With the additives the decomposition temperature could be reduced and the kinetics can be improved. Effect of addition of Zeolites on decomposition of Ammonia Borane at different temperatures is reported in this paper. It was observed that the kinetics behaviour is greatly affected by addition of Zeolites with considerable reduction in the induction or warm-up period. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Gupta A.,Indian Institute of Technology Bombay | Vashistha M.,Pillais Institute of Information Technology | Sharma P.,Indian Institute of Technology Bombay
Thin Solid Films | Year: 2014

A single junction hydrogenated amorphous silicon (a-Si:H) solar cell with incorporating hydrogenated nanocrystalline silicon (nc-Si:H) and a-Si:H (nc-Si:H/a-Si:H) multiple quantum wells (MQW) in the intrinsic region is proposed. Its theoretical realization has been made on the basis of existing quantum well solar cell models to determine the influence of the incorporated MQW over the conversion efficiency of a-Si:H solar cell. The atomic energy states and density of states of nc-Si:H/a-Si:H quantum wells (QW) are simulated at various QW widths. Based on the simulated results the absorption coefficient of nc-Si:H/a-Si:H QW is estimated and these values along with the evaluated atomic energy states of QW are used to optimize the QW width for the designed quantum well solar cell. The optimum well width is found to be 10 nm, where the absorption coefficient increases in three steps starting from 1.0 × 104 cm- 1 to 3.0 × 104 cm- 1 for photon energy of 1.2 eV to 1.4 eV, respectively, and thereafter remained constant for higher energies. The estimated absorption coefficient of 10 nm QW is involved in the calculations of photocurrent density to study the effect of number of incorporated QW on short circuit current density (JSC), open circuit voltage (VOC) and efficiency (η) of a-Si:H solar cell. The JSC, VOC, and η are presented for up to 100 QW incorporated a-Si:H solar cell. The results show that the conversion efficiency of a-Si:H solar cell is directly related to the number of incorporated QW, which is mainly due to the growing short circuit current density with increasing number of QW. The current-voltage plot for 100-QW a-Si:H solar cell with intrinsic region of 5.5 μm showed a peak power of 13.3 mW/cm2. © 2013 Elsevier B.V.

Manna J.,Indian Institute of Technology Bombay | Roy B.,Indian Institute of Technology Bombay | Vashistha M.,Pillais Institute of Information Technology | Sharma P.,Indian Institute of Technology Bombay
International Journal of Hydrogen Energy | Year: 2014

Cobalt boride is known to act as a catalyst to facilitate the hydrolysis reaction of sodium borohydride. The catalytic nature of cobalt boride is immensely dependent upon the synthesis procedure and reaction conditions used, especially on the relative amount of Co(II) and borohydride used for catalyst preparation. In the current work a set of catalysts were prepared by varying the cobalt(II) and borohydride ratio in the reactant solution. The prepared catalysts were well characterized using different characterizing tools like XRD, FTIR, FEG-SEM, FEG-TEM, ICP-AES and XPS. The effect of the catalyst on the hydrolysis of sodium borohydride was thoroughly studied and reported in the current work. The catalytic activity of the catalyst was observed to be highly dependent on the reduced cobalt content. It was observed that the excess amount of borohydride used to synthesize the catalyst, was not increasing the catalytic activity after the complete reduction of cobalt. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ranade S.R.,SAMEER | Nair D.U.,Pillais Institute of Information Technology
2011 IEEE Applied Electromagnetics Conference, AEMC 2011 | Year: 2011

Short range radar sensors for automotive radar applications are operating in the frequency range of 22GHz to 29 GHz band in the United States. UWB sensors in the frequency domain of 24 GHz based on GaAs technology are already established in the automotive radar market. Recently automotive radar sensors based on SiGe technology chipset have also been reported in this frequency band. Thus our effort is to design a substrate integrated waveguide (SIW) based H plane Horn antenna on a PTFE substrate, with an end-fire beam, which would be better suited for automotive radar applications. Rectangular dielectric loaded substrate integrated waveguide (SIW) H-plane sectoral horn antennas, operating at various frequencies in the range of 21 GHz to 28 GHz have been fabricated and tested. These antennas have been simulated and fabricated on a substrate of thickness 3.2mm and the dielectric material used is PolyTetraFluoroEthylene (PTFE). The SIW H plane horn antenna with dielectric loading resulted in improved gain and beamwidth. The length of the H Plane sectoral horn antenna was reduced further after optimizing the dielectric loading which resulted in further increase of gain and also narrow beam widths in the E-plane and H-plane. The results from the simulation and those from the measurement which are in good agreement are presented in the paper. The antenna prototypes that have been fabricated are not only compact but also low cost and they can be integrated with the high speed digital technology required for all the other subsystems of the automotive radar on the same PTFE substrate. © 2011 IEEE.

Krishnan D.,Pillais Institute of Information Technology | Chatterjee M.,Pillais Institute of Information Technology
Communications in Computer and Information Science | Year: 2012

Cloud Computing is the recent buzz word in computing which has enormous potential to revolutionize the IT industry. Cloud opened up new computing scenarios coupled with many significant benefits, however they also turned to become new avenues of attacks and exploits. This paper proposes a unique Distributed Intrusion Detection System (DIDS) based on a novel combination of two variant trends in intrusion detection-the behavior based and knowledge based intrusion detection mechanisms. The behavior based approach facilitates improved detection in the dynamic cloud environment and the knowledge based approach supports the detection scheme with its definitive rule base. The functionality of both these approaches has been improved by the addition of an adaptive approach which helps to significantly assist in lowering the false positives. In addition to this, another novel and the striking advantage of the proposed detection scheme is the alert clustering and analyzing facility thereby helping all cooperating nodes in detecting false alarms from any malicious nodes. DOS attacks in one node can be sent as alerts to help other cooperating nodes in updating themselves about new attack patterns leading to early detection and prevention of attacks. This scheme collectively helps to make the underlying cloud infrastructure more immune to attacks and continue to provide services to users. © 2012 Springer-Verlag.

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