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941.
A. V. Ramesh Kumar R. Singh R. K. Nigam 《Journal of Radioanalytical and Nuclear Chemistry》1999,242(1):131-137
Corrosion products of mild steel exposed to four different cultures of sulfur reducing bacteria (SRB) grown in a synthetic medium have been studied by transmission Mössbauer spectroscopy (TMS). Cultures of SRB studied are two hydrogenase positive strains,Desulfovibrio desulfuricans (DD) andDesulfovibrio vulgaris (DV) and two hydrogenase negative strainsDesulfotomaculum orientis orientis (DO) andDesulfotomaculum nigrificans (DN). The corrosion products generated on the coupons as well as in the broth were studied. In all the cases, the corrosion products removed from coupons showed the presence of green rust 2 (GR2), ferrous sulfides, γ-FeOOH and superparamagnetic (SPM) α-FeOOH in different proportions. The corrosion products from the broth showed a symmetrical central doublet, which indicates the presence of γ-FeOOH and SPM α-FeOOH along with ferrous sulfides. The corrosion products from coupons suspended in sewage water also showed the presence of GR 2 and ferrous sulfides together with oxyhydroxides. FTIR spectrum supports the presence of these phases in corrosion products. The formation of GR 2 on coupons seems to be the first step for the SRB induced corrosion. The corrosion rate has been found in the order of DO>DN>DV>DD. 相似文献
942.
It is shown that a locally symmetric contact strongly pseudo-convex integrableCR manifold of dimension greater than 3 and other than 7 is locally isometric to a unit sphere or the Riemannian product of an (n + 1)-dimensional Euclidean space and a sphere. A conformally flat contact strongly pseudo-convex integrableCR manifold is locally isometric to a unit sphere, provided the characteristic vector field is an eigenvector of the Ricci tensor at each point. 相似文献
943.
Poly(butylene terephthalate-co-cyclohexylene dimethylene terephthalate) copolymers PBTCT, were synthesized by melt condensation with compositions ranging from 94/08 to 23/77. 13C NMR spectroscopy was used to study the microstructure of the copolyesters and was found to be completely random. The melting temperature, crystallization temperature on cooling, enthalpy of melting and crystallization followed an eutectic behaviour. Thermal and x-ray diffraction studies indicated that the copolyesters in all composition could crystallize. The XRD studies further indicated that PBT rich copolyesters in the range 75 to 100% BT, crystallized in the PBT lattice while the copolyesters rich in PCT having 38 to 100% CT, crystallized in the PCT lattice. 相似文献
944.
V. Mathivanan T. Raghavalu M. Kovendhan S. Gokul Raj G. Ramesh Kumar R. Mohan K. Suriya Kumar 《Crystal Research and Technology》2007,42(9):895-898
L‐histidinium acetate dihydrate {abbreviated as LHAc; [C6H10 N3O2+ C2H3O2‐ 2H2O], a new nonlinear optical (NLO) material has been grown from aqueous solution. The grown crystals were subjected to X‐ray diffraction, Fourier transform infrared (FTIR) and FT‐Raman analyses. Thermal studies have been carried out for its thermal stability. Optical behaviour such as UV‐Vis‐NIR spectrum and second harmonic generation (SHG) were also investigated. Its SHG efficiency was found as deff = 2.2 deff (KDP). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
945.
The conventional Clauser-chart method for determination of local skin friction in zero or weak pressure-gradient turbulent
boundary layer flows fails entirely in strong pressure-gradient situations. This failure occurs due to the large departure
of the mean velocity profile from the universal logarithmic law upon which the conventional Clauser-chart method is based.
It is possible to extend this method, even for strong pressure-gradient situations involving equilibrium or near-equilibrium
turbulent boundary layers by making use of the so-called non-universal logarithmic laws. These non-universal log laws depend
on the local strength of the pressure gradient and may be regarded as perturbations of the universal log law. The present
paper shows that the modified Clauser-chart method, so developed, yields quite satisfactory results in terms of estimation
of local skin friction in strongly accelerated or retarded equilibrium and near-equilibrium turbulent boundary layers that
are not very close to relaminarization or separation. 相似文献
946.
The Portevin–Le Châtelier (PLC) instability is commonly observed in Al–Mg alloys and is manifested in serrated flow within the stress–strain response. We investigate the persistence of this instability with reduction in grain size by studying an ultrafine-grained (ufg) aluminum alloy (Al5083) and a conventional grain size Al5083. Micro-scale tensile tests combined with digital image correlation (DIC) reveal strength anisotropy and heterogeneity of the deformation in the three material directions (extrusion, rolled, and transverse). For the same applied displacement rate, the PLC effect in ufg-Al5083 is observed only over a small strain range immediately following the yield, while the coarse-grained Al5083 exhibits serrated flow over nearly the entire plastic strain range. These observations are explained using the stability analysis of Hähner (Acta Mater 45:3695–3707, 1997), and implications for nanocrystalline (nc) alloys are discussed. 相似文献
947.
R Rajesh B Ramesh Kumar S K Varshney Manoj Kumar Chhaya Chavda Aruna Thakkar N C Patel Ajai Kumar Aditya Team 《Pramana》2000,55(5-6):733-740
Thomson scattering technique based on high power laser has already proved its superoirity in measuring the electron temperature
(T
e and density (n
e) in fusion plasma devices like tokamaks. The method is a direct and unambiguous one, widely used for the localised and simultaneous
measurements of the above parameters. In Thomson scattering experiment, the light scattered by the plasma electrons is used
for the measurements. The plasma electron temperature is measured from the Doppler shifted scattered spectrum and density
from the total scattered intensity. A single point Thomson scattering system involving a Q-switched ruby laser and PMTs as the detector is deployed in ADITYA tokamak to give the plasma electron parameters. The system
is capable of providing the parameters T
e from 30 eV to 1 keV and n
e from 5 × 1012cm−3−5 × 1013cm−3. The system is also able to give the parameter profile from the plasma center (Z=0 cm) to a vertical position of Z=+22 cm to Z=−14 cm, with a spatial resolution of 1 cm on shot to shot basis. This paper discusses the initial measurements of the plasma
temperature from ADITYA. 相似文献
948.
R. Thirunakaran N. Kalaiselvi P. Periasamy B. Ramesh Babu N. G. Renganathan N. Muniyandi M. Raghavan 《Ionics》2001,7(3):187-191
LiMn2O4 spinel is one of the most promising cathode materials for lithium-ion batteries because of its cheapness and eco-friendliness.
Due to Jahn-Teller distortion, the capacity fades, however, upon repeated cycling. Attempts are being made to improve the
cycle life of the spinel by substitution of manganese with other cations. In this paper we report the effect of partial substitution
of manganese by Mg2+ ions in the LiMn2O4 phase. LiMgyMn2−yO4 (y=0 – 0.3) has been synthesized by a thermal method and characterized using XRD, TG/DTA and FTIR. The electrochemical performance
is correlated with the dopant concentration. 相似文献
949.
S. N. U. A. Kirmani Ramesh C. Gupta 《Annals of the Institute of Statistical Mathematics》2001,53(2):203-216
The proportional odds (PO) model with its property of convergent hazard functions is of considerable value in modeling survival data with non-proportional hazards. This paper explores the structure, implications, and properties of the PO model. Results proved include connections with geometric minima and maxima, ageing characteristics, and bounds on mean and variance of survival times. 相似文献
950.
The impact of household preparations on the residues of pesticides in selected agricultural food commodities available in India. 总被引:1,自引:0,他引:1
Gas chromatographic multiresidue methods for simultaneous determination of organophosphorus, organochlorine, and organonitrogen pesticides were used to study the exposure of the Indian population to pesticide contamination at their actual dietary intakes. Selected agricultural commodities--5 kinds of vegetables (tomato, potato, okra, cabbage, and green beans), 6 kinds of cereals and pulses (rice, maize, wheat, red gram, black gram, and green gram), and 6 kinds of fruits (mango, orange, guava, banana, apple, and grapes)--readily available in Chennai City local markets--were studied for this purpose. Samples were fortified with known concentrations of various pesticides and subjected to household preparation methods commonly used in India. The impact of household preparation is very high, resulting in 65-95% decontamination of pesticides at different stages. Of 512 raw market samples analyzed, the organochlorine and organophosphorus pesticides present in 12 samples were removed during household preparations, resulting in residues well below the toxicologically acceptable limits. 相似文献