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861.
Khan KM Maharvi GM Khan MT Perveen S Choudhary MI Atta-Ur-Rahman 《Molecular diversity》2005,9(1-3):15-26
862.
Khalid Rashid 《Zeitschrift für Physik A Hadrons and Nuclei》1970,232(4):342-347
The ground state radiative widths of the 1.56 MeV (3/2+) and the 1.35 MeV (5/2?) levels in19F were determined by inelastic electron scattering. The measured cross sections have been analysed using DWBA calculations. The resultsΓ y 0 (5/2?→1/2?,E3)=(8.1±1.7)·10?10eV andΓ y 0 (3/2+→1/2+,E2=(1.76±0.15)·10?4eV are in agreement with, but more accurate than, former measurements. 相似文献
863.
Khalid Masood 《Proceedings of the Japan Academy. Series B, Physical and biological sciences》2006,82(7):224-231
We investigate the inverse problem associated with the heat equation involving recovery of initial temperature distribution in a two-layer cylinder with perfect thermal contact at the interface. The heat equation is solved backward in time to obtain a relationship between the final temperature distribution and the initial temperature profile. An integral representation for the problem is found, from which a formula for initial temperature is derived using Picard’s criterion and the singular system of the associated operators. The known final temperature profile can be used to recover the initial temperature distribution from the formula derived in this paper. A robust method to regularize the outcome by introducing a small parameter in the governing equation is also presented. It is demonstrated with the help of a numerical example that the hyperbolic model gives better results as compared to the parabolic heat conduction model. 相似文献
864.
The TRA estimates are introduced in the case of a moving average model in the presence of additive outliers. We establish, under some hypothesis, the consistency of these estimates. To cite this article: N. Berrahou, K. El Himdi, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 549–552. 相似文献
865.
Deliberate activation of the reaction vessel surface leads to the domination of chain termination in ethane pyrolysis by the reaction As a result, chains are dramatically reduced in length, methane yields are entirely primary and larger in proportion to other products, and values of k1 can be directly determined from methane yield data without ambiguity. Experiments carried out in the temperature range of 841–913K at initial ethane pressures of 1–20 torr, without and with added nitrogen, yield the infinite pressure Arrhenius equation It is shown that most previously published data can be combined with those of this study to yield Fall-off curves for k1 as a function of pressure are in good agreement with those from other laboratories. From these the relevant data for k?1 can be extracted for use in other kinetic studies. 相似文献
866.
It is shown that, by deliberate activation of the reaction vessel, heterogeneous reaction at the wall can be made to dominate chain termination in a complex gas-phase reaction. For a homogeneous process, characterized, as is often the case, by multiple terminations, this has the effect of simplifying the mechanism and allowing explicit solution of the relevant steady-state equations so that the rate constants of some individual steps can be evaluated without assumption as to the values of those of others. The pyrolysis of propane, in the vicinity of 500°C, has been used as an example of this approach. Enhancement of the wall activity leads to the reaction (1) providing, almost exclusively, chain termination. As a result, rate constants for the initiation step (2) can be directly determined. The results of this study provide the Arrhenius equation In combination with current thermochemical values this result gives k?1 = 1013.40 cm3/mol·s which, in turn, implies, via the geometric mean rule, kEt-Et = 1012.9 cm3/mol·s for ethyl–ethyl recombination, in good accord with the most recent determinations and compatible with the newly proposed value of the enthalpy of formation of ethyl. The first-order wall constant k8 has been evaluated as k8<104.2 s?1. This appears to be the first occasion on which a wall constant has been evaluated from data for a high-temperature complex gas reaction. 相似文献
867.
Khalid A. Al-Farhan 《Journal of chemical crystallography》1992,22(6):687-689
The crystal structure of Triphenylphosphine Oxide, C18H15PO, was reinvestigated using Mo-K radiation =0.71069 Å,(Mo-K)=1.36 cm–1.M
r=278.1, orthohombic,Pbca,a=29.089(3),b=9.1347(9),c=11.261(1) Å,V=2992.2 Å3,Z=4,D
x=1.235 Mg m–3. The structure was refined by full-matrix least-squares toR=0.040 andR
w=0.036 for 1848 unique reflections and 182 variables. Improved bond lengths and angles were obtained; O-P is 1.479(2) Å, weighted means of P-C is 1.803(1) Å, O-P-C is 112.6(1)° and C-P-C is 106.2(1)°. 相似文献
868.
Chun Yik Wong Kee Shyuan Loh Wan Ramli Wan Daud Kean Long Lim Mohammad Khalid 《高分子科学杂志,C辑:聚合物评论》2020,60(1):171-202
AbstractPoly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive proton exchange membrane (PEM) alternative to NafionTM. However, the pristine PVA membrane is a poorer proton conductor than the NafionTM membrane due to the absence of negatively charged ions. Hence, modification of PVA matrixes whilst complying with the requirements of projected applications has been examined extensively. Generally, three modification methods of PVA membranes have been highlighted in previous reports, and these are (1) grafting copolymerization, (2) physical and chemical crosslinking, and (3) blending of polymers. The use of each modification method in different applications is reviewed in this study. Although the three modification methods can improve PVA membranes, the mixed method of modification provides another attractive approach. This review covers recent studies on PVA-based PEM in different fuel cell applications, including (1) proton-exchange membrane fuel cells and (2) direct-methanol fuel cells. The challenges involved in the use of PVA-based PEM are also presented, and several approaches are proposed for further study. 相似文献
869.
The volumetric and viscometric study of three allopathic drugs (sodium valporate, benzalkonium chloride, and losartan potassium) in ethanol solvent is reported here. This study was carried out at four different temperatures that is, from 288.15 to 318.15 K. The accurately measured density values were used to calculate partial molar volume at infinite dilution, solute–solute interaction parameter, Hepler's constant, partial molar expansivity constant, and isobaric thermal expansion coefficient. The viscosity measurements were carried out for the calculation of constants of Jones–Dole equation and to calculate different thermodynamic parameters of viscous flow which include standard free energy change, standard enthalpy change, and standard entropy change of viscous flow. All these viscometric and volumetric parameters are useful for understanding the different types of interactions of drugs in solution and to study the drug action in body. The results of both volumetric and viscometric studies showed that all drugs had structure promoting effect on solvent, existing of strong solute–solvent interaction, and very weak solute–solute interaction. For all these drugs, solvophobic interaction was found to be dominant over electrostriction. Viscometric studies also showed the existing of stronger solute–solvent interaction in ground state as compared to that in transition state. 相似文献
870.
Agha Khalid A. Abo-Dya Nader E. Ibrahim Tarek S. Abdel-Aal Eatedal H. Abdel-Samii Zakaria K. 《Monatshefte für Chemie / Chemical Monthly》2020,151(4):589-598
Monatshefte für Chemie - Chemical Monthly - An efficient green route for monoacylation of aromatic diamines, namely o-phenylenediamine and p-phenylenediamine and aliphatic diamines... 相似文献