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51.
Rana Shafia Nawaz M. Alharbi Sayer Obaid 《Journal of Thermal Analysis and Calorimetry》2021,143(1):421-429
Journal of Thermal Analysis and Calorimetry - Theoretical investigation about the role of hybrid nanoparticles to enhance the effective thermal conductivity of working micropolar fluid over a... 相似文献
52.
Foiad Sobhi Obaid 《Ukrainian Mathematical Journal》1998,50(3):498-506
We show that a solution of the Dirichlet problem for an elliptic equation of the fourth order with constant coefficients,
whose right-hand side is periodic in all variables except one and exponentially decreases, converges at infinity to a certain
polynomial of the first degree in the nonperiodic variable. Coefficients of this polynomial are determined.
Institute of Mathematics, Ukrainian Academy of Sciences, Kiev. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50,
No. 3, pp. 437–444, March, 1998. 相似文献
53.
El-Sayed H. El-Mossalamy Fawzia M. Al-Nowaiser Shaeel A. Al-Thabaiti Abdul O. Al-Youbi Suliman N. Baschel Abdulla Y. Obaid 《Monatshefte für Chemie / Chemical Monthly》2007,10(4):853-857
The new polymer containing cyano groups was synthesized by γ-irradiation. The oximated polymer was prepared using hydroxylamine
hydrochloride in basic medium. The characterization of monomer, polymer, and oximated ones was confirmed by infrared and nuclear
magnetic resonance spectroscopy. The complex formation of the amidoxime salt towards ZnII, CuII, and ZnII/CuII mixture in aqueous solution was studied by atomic absorption spectroscopy, energy dispersive spectroscopy, and electron spin
resonance spectrometry. The significant binding capacity of these metal ions revealed its selectivity to Zinc(II) ion. The
thermal stability of polymers and complexed ones was investigated using thermogravimetry analysis. The change in their morphology
was observed by scanning electron microscopy (SEM). 相似文献
54.
Aromatic nitrations by tetranitromethane are shown to be photo-chemically initiated and are believed to proceed via trinitromethyl nitrite. 相似文献
55.
We obtain some new trigonometric identities and find the corresponding Chebyshev polynomials identities. We also indicate their applications to certain boundary value problems which arise in Mechanics. 相似文献
56.
We investigate the flow of a generalised Newtonian liquid between two contra-rotating cylinders of equal size — the so called two-roll mill problem. A finite element method is used to obtain solutions for the case of a Carreau model and for a power law model. Consideration is given to the influence of shearthinning on the flow pattern around the cylinders. Results are presented for different speeds of rotation of the cylinders and for various values of fluid parameters. A comparison is made with the analytical solution of Jeffrey. 相似文献
57.
In a previous paper consideration was given to the flow of a generalised Newtonian liquid between contra-rotating cylinders — the so-called two-roll mill problem. We present here an extension to that work in which we consider the effect of elasticity on the flow. An Oldroyd three-constant model is used to characterize the fluid properties and a finite-element method used to solve the relevant equations. Results are presented for different speeds of rotation of the cylinders and for various values of the fluid parameters. A comparison is made between the effects of elasticity and of shear-thinning on the flow patterns around the cylinders. 相似文献
58.
Combinatorial identities, trigonometric formulas, together with complex variable techniques are used to derive exact and closed expressions for the six flexure functions of certain isotropic cylinders under flexure. The cross sections are bounded either by the closed curvesr=a cosn (/n) (–<) or the closed curvesr=asin(/n)n(–<), wheren isa positive integer (n>1).
Résumé Des identiteés combinatoires et des formules trigonométriques avec des techniques de variables complexes sont utilisées pour dériver des expressions exactes et simples pour les six fonctions de flexion de quelques cylindres isotropiques. Les sections sont limitées par les courbes ferméesr=a cosn /n(–) et les courbesr=asin/nn(–) où est un entier positif (n>1).相似文献
59.
The reaction between biscyclopentadienyl titanium dichloride and aluminium alkyls and alkyl chlorides has been examined by ESR spectroscopy, and by the abilities of the various resulting complexes to initiate the polymerization of ethylene at 1 atm and ambient temperature. In general, it is concluded that the active initiating species is a Ti(IV) complex, and not the paramagnetic Ti(III) complexes. Accordingly, the development of an ESR spectrum is accompanied by a fall off in initiating efficiency, decrease in polymerization rate and increased molecular weight of the polymers produced. The reduction of Ti(IV) to Ti(III) during the polymerization accounts for the fall in rate with conversion; addition of an oxidizing agent (1:2-dichloroethane) to the polymerization converts Ti(III) to Ti(IV), as observed by the disappearance of the ESR signal, and increases the efficiency of the polymerization. Block copolymers of ethylene with propylene and butadiene have been prepared with this initiator; the efficiency in producing blocks has been used to study the decomposition of the active sites by a first order reduction process. 相似文献
60.
F. A. Al-Newaiser S. A. Al-Thabaiti A. O. Al-Youbi A. Y. Obaid M. A. Gabal 《Chemical Papers》2007,61(5):370-375
The thermal decomposition behavior in air of SrC2O4 · 1.25H2O was studied up to the formation of SrO using DTA-TG-DTG techniques. The decomposition proceeds through four well-defined
steps. The first two steps are attributed to the dehydration of the salt, while the third and fourth ones are assigned to
the decomposition of the anhydrous strontium oxalate into SrCO3 and the decomposition of SrCO3 to SrO, respectively. The exothermic DTA peak found at around 300°C is ascribed to the recrystallization of the anhydrous
strontium oxalate. On the other hand, the endothermic DTA peak observed at 910°C can be attributed to the transition of orthorhombic-hexagonal
phase of SrCO3. The kinetics of the thermal decomposition of anhydrous strontium oxalate and strontium carbonate, which are formed as stable
intermediates, have been studied using non-isothermal TG technique. Analysis of kinetic data was carried out assuming various
solid-state reaction models and applying three different computational methods. The data analysis according to the composite
method showed that the anhydrous oxalate decomposition is best described by the two-dimensional diffusion-controlled mechanism
(D2), while the decomposition of strontium carbonate is best fitted by means of the three-dimensional phase boundary-controlled
mechanism (R3). The values of activation parameters obtained using different methods were compared and discussed. 相似文献