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51.
Sharma Neeraj Bose B. Kaistha Atul Bhatt Sarvjeet S. Chaudhry Subhash C. 《Transition Metal Chemistry》2002,27(7):736-740
Niobium(V) chloride aryloxides [NbCl3(OAr)2] and [NbCl2(OAr)3] (Oar = —OC6H4Bu
t
-4 and —OC6H4OMe-4) have been prepared by reacting NbCl5 with two and three equivalents of the respective phenol in CCl4. The complexes have been characterized by elemental analysis, molecular weight determination, i.r., 1H-n.m.r., u.v.–vis. and MS techniques. Thermal behaviour (t.g.–d.t.) of the complexes has also been studied and decomposition schemes proposed. The kinetic and thermodynamic parameters namely, the activation energy 'E
*', the frequency factor 'A', entropy of activation 'S' and specific rate constant 'kr' etc. have been calculated employing the Coats–Redfern equation. The non-isothermal t.g. data has also been utilized to determine the most probable mechanism and corresponding activation energy for the decomposition of niobium(V) complexes by testing seven different theoretically possible decomposition mechanisms. 相似文献
52.
Theoretical study of molecular and electronic structure of 2‐Se‐(2‐methyl‐2‐propenyl)‐1‐benzoic acid
Ali Jameel Hameed Abraham F. Jalbout Bartosz Trzaskowski 《International journal of quantum chemistry》2007,107(1):152-158
A theoretical study of 2‐Se‐(2‐methyl‐2‐propenyl)‐1‐benzoic acid was carried out to investigate the molecular and electronic structure of this molecule, using the B3LYP density functional theory (DFT) method with the 6‐311+G** basis set. The optimized geometry of the molecule was obtained for the ortho, meta, and para isomers of the complex. In addition, the theoretical vibrational spectrum is presented, and thermal corrections in the limit of 100–1,000 K are discussed using the Shomate thermodynamic equations. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
53.
Abraham F. Jalbout Ali Jameel Hameed Bartosz Trzaskowski 《Journal of organometallic chemistry》2007,692(5):1039-1047
A series of 1-(4, 5 and 6-selenenyl derivatives-3-formyl-phenyl) pyrrolidinofullerenes molecules C60-C2H4N-[3-(CHO)C6H3SeX] were investigated theoretically by performing Density Functional Theory calculations at the B3LYP/3-21G∗ level of the theory. The substituents include: X = CN, CH2CH(NH2)CO2H and CH2CH2CH(NH2)CO2H. We have selected these substituents to be in ortho, meta and para positions with relation to formyl group in order to show the effect of such structural change on the electronic properties of the molecules. The theoretical IR spectra, physical, chemical and thermodynamics properties of the molecules studied are obtained and discussed. 相似文献
54.
The amount of heat released in a volume whose extent can be ignored as compared with the dimensions of the surroundings of interest, may be classified as (i) the point-heat source, (ii) the line-heat source, and (iii) the plane-heat source. The temperature solutions of these transient conduction problems in an extended, homogeneous, and isotropic medium, are discussed in closed form. These analytical solutions are presented for the case of time-dependent, continuously operating heat source of the form
, wherev is a positive real number. The dimensionless temperature solutions for all the problems are presented in terms of the Whittaker function. It is found that the present analysis covers well known (classical) solutions as well as some new solutions.
Einige analytische Lösungen für zeitabhängige, kontinuierlich wirkende Wärmequellen
Zusammenfassung Der Betrag an freigesetzter Wärme in einem Volumenbereich, dessen Ausdehnung vernachlässigbar ist gegenüber den Abmessungen des interessierenden Umgebungsbietes, läßt sich wie folgt klassifizieren: (i) punktförmige Wärmequelle, (ii) Linienquelle und (iii) ebene Wärmequelle. Die Temperaturfeld — Lösung für diese instationäre Wärmeleitungsproblem in einem ausgedehnten, homogenen und isotropen Medium lassen sich in geschlossener Form angeben, und zwar für den Fall zeitabhängiger, kontinuierlich wirkender Wärmequellen mit dem Zeitgesetz , wobeiv eine positive ganze Zahl ist. In jedem der o.g. Fälle wird das normierte Temperaturfeld durch die Whittaker — Funktion beschrieben. Die hier vorgelegte Untersuchung liefert sowohl die bekannten klassischen, wie auch einige neue Lösungen.相似文献
55.
B. R. Madill M. L. Chaudhry P. G. Buckholtz 《The Journal of the Operational Research Society》1985,36(6):531-535
This paper considers the solution of a deterministic queueing system. In this system, the single server provides service in bulk with a threshold for the acceptance of customers into service. Analytic results are given for the steady-state probabilities of the number of customers in the system and in the queue for random and pre-arrival epochs. The solution of this system is a prerequisite to a four-point approximation to the model GI/G a,b /1. The paper demonstrates that the solution of such a system is not a trivial problem and can produce interesting results. The graphical solution discussed in the literature requires that the traffic intensity be a rational number. The results so generated may be misleading in practice when a control policy is imposed, even when the probability distributions for the interarrival and service times are both deterministic. 相似文献
56.
57.
Jan Skramstad Arne Garvang Mohammed Shoaib Chaudhry 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Recent studies on the reaction of thiophenes in the lowtemperature plasma of glow discharges have disclosed the formation of thioketene and carbon monosulfide. Alkylthiophenes, on the other hand, undergo a complex series of reactions leading to benzene whereas phenylthiophenes mainly give naphtalene. 相似文献
58.
A novel design of Multiplexer–Demultiplexer (MUX–DEMUX) based on index guiding soft glass nematic liquid crystal (NLC) based
photonic crystal fiber coupler is proposed and analyzed. The simulation results are obtained using the full vectorial finite
difference method as well as the full vectorial finite difference beam propagation method. The numerical results reveal that
the proposed MUX–DEMUX of length 3.265 mm can provide low crosstalk better than −20dB with great bandwidths of 40 and 24 nm
around the wavelengths of 1.3 and 1.55 μm, respectively. In addition, the reported MUX–DEMUX has a tolerance of ±3% in its
length which makes the design more robust to the perturbation introduced during the fabrication process. 相似文献
59.
B3LYP and MP2 calculations with the commonly-used 6-31+G(d) basis set predict qualitatively different structures for the Tyr–Gly conformer book1, which is the most stable conformer identified in a previous study. The structures differ mainly in the ψtyr Ramachandran angle (138° in the B3LYP structure and 120° in the MP2 structure). The causes for the discrepant structures are attributed to missing dispersion in the B3LYP calculations and large intramolecular BSSE in the MP2 calculations. The correct ψtyr value is estimated to be 130°. The MP2/6-31+G(d) profile identified an additional conformer, not present on the B3LYP surface, with a ψtyr value of 96° and a more folded structure. This minimum is, however, likely an artefact of large intramolecular BSSE values. We recommend the use of basis sets of at least quadruple-zeta quality in density functional theory (DFT), DFTaugmented with an empirical dispersion term (DFT-D) and second-order Møller-Plesset perturbation theory (MP2 ) calculations in cases where intramolecular BSSE is expected to be large. 相似文献
60.
Abdul Karim‐Talaq Mohammad Abdullah Thamer Hameed Mohammed Affan Alhamdany Khaldun Mohammad Al Azzam Gaidaa Abd Alkareem Talk 《Biomedical chromatography : BMC》2019,33(4)
A method for digestion of light and medium Iraqi crude oils (Basrah and Khanaken oils) using microwave‐induced combustion (MIC) in closed vessels is described for the determination of Hg, Au, Cu, Al, Ca, Co, K, Mg, Si and Sr by inductively coupled plasma optical emission spectrometry (ICP–OES) and Mo, Ti, Mn, Li, Se?1, Rb, Ag, Ba, Pb, As, Cd, Cr, Fe, Ni, V and Zn by inductively coupled plasma mass spectrometry (ICP–MS). Upon using MIC it was possible to obtain lower limits of detection by ICP–MS and also by ICP–OES compared with those obtained by microwave‐assisted digestion. The MIC was the best choice with regard to the possibility of using dilute nitric acid as an absorbing solution, which is important to minimize the interference encountered by ICP–MS and ICP–OES.The physicochemical parameters and some contaminants of crude oil samples were analyzed to classify and assess the quality of the crude oils. This study determines the viability of the use of Fourier transform infrared spectroscopy as an alternativee to traditional petroleum geochemical methods for crude oil characterization. The infrared fingerprints agree with the results obtained from GC–MS analysis. 相似文献