North Eastern Regional Institute of Science and Technology
Itanagar, India

North Eastern Regional Institute of Science and Technology is a science and technology oriented higher education institute in Nirjuli, Itanagar, in the Indian state of Arunachal Pradesh. Established in 1984, it is a deemed university, autonomous, fully funded and controlled by the Ministry of Human Resource Development, Department of Education, Government of India. Wikipedia.

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Giri A.,North Eastern Regional Institute of Science and Technology | Das B.,North Eastern Regional Institute of Science and Technology
International Journal of Thermal Sciences | Year: 2012

A computational study of laminar mixed convection over a shrouded vertical rectangular fin array attached to a vertical base has been performed. Maintaining the base-fin system above the surrounding temperature, a fan velocity is imposed to enhance the heat transfer through the mixed convection process. Present study finds the effects of clearance spacing, fin spacing, fin length, Reynolds number and Grashof number on the thermal performance of the base-fin system. Mixed convection inlet velocity is decoupled to forced and natural convection velocity components and the resulting pressure drop across the duct length arises purely due to the forced convection velocity component. Thus, Reynolds number is estimated based on forced convection velocity component as the inlet velocity does not vanish even in pure natural convection. Computed local Nusselt number shows sharp drop near the entrance and reaches a fully developed value after a certain streamwise distance from the entrance. Further, fully developed local Nusselt number shows a clear maximum at the clearance spacing of 0.075 and 0.15 for the inter-fin spacing of 0.3 and 0.5 respectively. Pressure drop across the duct, induced natural convection velocity and overall Nusselt number are well correlated with the governing parameters of the problem. © 2012 Elsevier Masson SAS. All rights reserved.

Jhajharia D.,North Eastern Regional Institute of Science and Technology | Singh V.P.,Texas A&M University
International Journal of Climatology | Year: 2011

Trends in maximum (Tmax), minimum (Tmin) and mean (Tmean) temperatures; diurnal temperature range (DTR = Tmax - Tmin); and sunshine duration at eight sites in Northeast (NE) India were investigated. Three sites observed decreasing trends in DTR corresponding to annual, seasonal (pre-monsoon and monsoon) and monthly (September) time scales. On the other hand, DTR increases were also observed at other three sites in monsoon and post-monsoon seasons as well as in the months of June, October and December. The sites showing DTR decreases (increases) witnessed either increasing trends in Tmin (Tmax) or decreasing trends in Tmax (Tmin), with Tmax (Tmin) showing either no trend or increasing at a smaller rate than Tmin (Tmax). Temperature remained practically trendless in winter and pre-monsoon seasons over NE India. However, temperature increases were observed in monsoon and post-monsoon seasons. Decreasing trends in sunshine duration were observed mainly on annual, seasonal (winter and pre-monsoon) and monthly (January, February and March) time scales. Concomitant decreases in sunshine duration may be one of the potential causes of the observed DTR decreases over NE India. © 2010 Royal Meteorological Society.

Devi T.G.,North Eastern Regional Institute of Science and Technology
Journal of Raman Spectroscopy | Year: 2010

The vibrational relaxation and molecular reorientational processes in liquids have been studied in some carbonyl-containing molecules using the acetonitrile (ACN) solvent. The vibrational and reorientational processes have been studied in correspondence with correlation times. The screening effect due to dielectric has been studied and the Onsager reaction field model has been tested. The study shows that repulsive types of intermolecular forces play an important role in complex systems. Copyright © 2010 John Wiley & Sons, Ltd.

The bimetallic and heterometallic coordination oxalate precursors uranyl(II)diaquatris(oxalato)lanthanate(III)octahydrate (UOLa) and cobalt(II)uranyl(II)pentaquatris(oxalato) lanthanate(III)octahydrate (CoUOLa) have been synthesized and characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that UOLa ultimately decomposed mainly to a mixture of U2O5, U3O8, La2O3 and La6UO12 at 1000 °C through the formation of several intermediates at 190, 496, and 770 °C. The presence of a trace of UO2, carbon and carbides of both uranium and lanthanum were also identified at end products. The precursor, CoUOLa lost all crystal and coordinated water molecules up to 235 °C, followed by slow decomposition of anhydrous species to a mixture of CoC2O4 and (UO2)2[La(C2O4)2.4]2 at 330 °C. The end products identified at 1000 °C is a mixture of CoO, LaO and U2O5 along with a trace of La2O3, LaCoO3, La2C3 and carbon. The unstable intermediate phases at 340 and 515 °C were also attributed during the fragmentation path of the precursor. The crystal structures of the major oxides identified in the end products in the mixture form of both the precursors are inferred from the powder XRD data. The kinetic parameters, E*, ln ko, ΔH and ΔS of all the dehydration and decomposition steps of the precursors are explored and discussed from DSC study in nitrogen. © 2010 Elsevier B.V. All rights reserved.

Das B.,North Eastern Regional Institute of Science and Technology | Giri A.,North Eastern Regional Institute of Science and Technology
Applied Thermal Engineering | Year: 2014

A numerical simulation of laminar mixed convection in a shrouded vertical non-isothermal fin array has been investigated. Convective medium is treated as non-Boussinesq fluid with temperature dependent properties. Computations are performed for the parametric range: Grashof number = 5.3 × 104 to 2.3 × 106, Reynolds number = 100 to 2200, dimensionless fin spacing = 0.1 to 0.5, and dimensionless clearance = 0.0 to 0.4. Computations demonstrate substantial deviation in heat transfer, as high as 18%, resulting from variable property non-Boussinesq fluid flow over non-isothermal fin compared to constant property Boussinesq fluid flow over isothermal fin. Optimum heat transfer coefficient is found to exist in a range of fin height from 0.04 m to 0.05 m, while dimensionless optimum fin spacing lies in a range from 0.2 to 0.3. Finally, induced natural convection velocity component and overall Nusselt number are well correlated with the governing parameters of the problem. © 2013 Elsevier Ltd. All rights reserved.

Bhuyan J.,North Eastern Regional Institute of Science and Technology
Dalton Transactions | Year: 2015

An overview of the chemistry of isoporphyrin, the tautomer of porphyrin, whose existence was predicated by the Noble laureate Woodward, is presented with emphasis on hydroxy-isoporphyrins of tetra-aryl derivatives. The chemistry of metalloisoporphyrin has been discussed since the discovery of the first metallo-isoporphyrin by Dolphin and co-workers, as no comprehensive article is available on this beautiful macrocycle. Attention is paid to the possible applications of metalloisoporphyrins as photosensitizers in photodynamic therapy, as a near infra-red dye and as a reactive agent for different atom transfer reactions. Some important findings about reactivity and theoretical results of hydroxy-isoporphyrins are discussed. Furthermore, the approaches of heme oxidation via isoporphyrin as an intermediate to understand the heme oxygenase mechanism are discussed. The metalloisoporphyrins are discussed reviewing coordination modes, structural changes, electronic properties and biological relevance. This journal is © The Royal Society of Chemistry.

Subadar R.,North Eastern Regional Institute of Science and Technology | Singh A.D.,North Eastern Regional Institute of Science and Technology
IEEE Wireless Communications Letters | Year: 2013

Performance of selection combining (SC) receiver has been derived over two-wave diffused power (TWDP) fading channels with arbitrary and non-identical fading parameters. An expression of cumulative distribution function (CDF) of signal-to-noise ratio (SNR) for TWDP fading channel has been derived, which is used to obtain the probability density function (PDF) of SNR at the output of SC receiver. The PDF of output SNR has been used to derive expressions of outage probability and average bit error rate for coherent and non-coherent modulation schemes. Effect of total number of branches M and the fading parameters K and Δ on the system performance has been studied. The obtained results are verified with the special case results available in literature and by Monte Carlo simulation. © 2012 IEEE.

Bhuyan J.,North Eastern Regional Institute of Science and Technology
Dalton Transactions | Year: 2016

The reactions of iron(iii) hydroxyisoporphyrin, chloro[5-(hydroxy)-5,10,15,20-tetrakis(4-methyl)-5,21H-porphinato]iron(iii) [Fe(4-Me-HTPI)(Cl)]-, 1 and chloro[5-(hydroxy)-5,10,15,20-tetrakis(4-methoxy-5,21H-porphinato]iron(iii) [Fe(4-OMe-HTPI)(Cl)]-, 2 with different O-, N- and S- nucleophiles have been performed to understand the reactivity of iron isoporphyrins with nucleophiles. The treatment of iron(iii) hydroxy isoporphyrin with alcohols is found to form ring opened 19-benzoyl-1-alkoxy-bilin iron complexes. When alkyl amines were used the formation of ring opened 19-benzoyl-1-alkylamine-bilin iron complexes was observed, but heterocyclic N-nucleophiles such as pyridine and imidazole form benzoyl bilinone iron complexes. No role of oxygen was found in these nucleophilic ring opening reactions. The treatment of a S-nucleophile such as PhSH is found to reduce iron(iii)-hydroxyisoporphyrin in the parent iron(iii) porphyrin compound. The ring opening products were characterized using electronic and ESI-mass spectroscopy. The mechanism for the formation of ring opening products is based on the formation of a tetrahedral intermediate at the carbon atom near the saturated meso carbon atom similar to the hydrolytic pathway of verdoheme conversion to biliverdin. © The Royal Society of Chemistry 2016.

Two heterobimetallic oxalate coordination compounds, zinc(II) tetraaquatris(oxalato)lanthanate(III)hexahydrate (ZnOLa) and cadmium(II)heptaaquatris(oxalato)lanthanate(III)tetrahydrate (CdOLa) were synthesized and characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. Both the compounds were found to have monoclinic structure. Thermal decomposition studies by TG, DTG and DTA in air have proved that the aqua ligands are associated with metals in a stronger coordination mode. The temperatures for pyrolysis were adopted from the TG results chosen from the stable range of thermograms. In case of ZnOLa, it decomposes through two steps and the end product at 1000 C was found to be consisting of mainly, La2O3, ZnO and La2ZnO x through the intermediate formation of several oxycarbonates of lanthanum at ca. 525 C. In case of cadmium analogue, three steps decomposition were observed and the final products were confirmed as CdO2, La 2O3, LaCO and La2CdO x via the formation of several intermediates at 340 and 590 C. The La2C 3 and carbon are also found as part of the end product. The kinetic parameters, E *, lnk o, â̂†H # and â̂†S # of all the deaquated and decomposition steps are investigated and discussed from the DSC study in nitrogen. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Heterobimetallic oxalato complex precursors, manganese(II) tetraaquatris(oxalato)lanthanate(III)hexahydrate (MnOLa), cobalt(II) pentaaquatris(oxalato)lanthanate (III)trihydrate (CoOLa), nickel(II) pentaaquatris(oxalato) lanthanate(III)hexahydrate (NiOLa) and copper(II)diaaquatris( oxalato)lanthanate(III)monohydrate (CuOLa) of the type, M3[La(C2O4)3(H2O)m] 2.nH2O have been synthesized in aqueous medium. The precursors were characterized by elemental analysis, IR, electronic spectral and powder X-ray diffraction studies. The good crystalline nature with monoclinic structures predominates in MnOLa and NiOLa whereas triclinic structures were found in Co- OLa and CuOLa. The solid-state thermal behaviour of the precursors was explored using TG, DTG and DTA in air. The MnOLa generated a mixture species consisting mainly of MnO2, Mn3 O4, Mn 5 O8, La2 O3 and LaMn7O12 at 1000 °C through the formation of several intermediate species at 380 and 570 °C. The studies revealed that Co- OLa led mainly to LaCoO3 and La2CoO4 along with some oxides of both the cobalt and lanthanum at 1000 °C. In case of nickel analogue the mixture species identified at 1000 °C are mainly of La2NiO4, La 2O3, Ni2O3 and NiO2. In case of CuOLa the product at 1000 °C consisted of La2CuO 4, La2Cu2O5 and oxides of copper and lanthanum. The nature of decomposition of the precursors in nitrogen were seen from DSC study and the kinetic parameters i.e., E*, lnk0, δH#, δS # and order of reaction of all the steps were evaluated and discussed. © Akademiai Kiado, Budapest, Hungary 2011.

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