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101.
Abdollah Omrani Mousa Ghaemy Abbas A. Rostami 《Journal of Thermal Analysis and Calorimetry》2009,98(2):477-483
The kinetics and mechanism of cure reaction of DGEBA using a chelate of Ni(II) with diethylenetriamine (dien), Ni(dien)2I2, as a curing agent was studied by DSC. TG curve of the complex curing agent showed mass loss in two region of temperature: 200–320 and 450–550 °C. Dynamic DSC measurements showed only one exothermic peak with a maximum about 250 °C depending on the heating rate. According to the methods of KAS and Ozawa–Flynn–Wall the values of E a were 92.5 and 96.2 kJ/mol, respectively. The isoconversional kinetic analysis in whole range of conversion, α = 0.02–0.95, showed small changes in the E a values in the region of α = 0.04–0.6 and most likely represent some average values (E a = 110 kJ/mol) between the values of E a of non-autocatalyzed and autocatalyzed reactions. Using the sole dependence of E a on α, the time required to reach fully cured materials under isothermal conditions were also predicted and compared with the experimental results. 相似文献
102.
Summary Let X ∼ Np(μ,σ2Ip) and let s/σ2 ∼ χ
n
2
, independent ofX, where μ and σ2 are unknown. This paper considers the estimation of μ (by δ) relative to a convex loss function given by (δ−μ)′[(1−α)Ip/σ2+αQ](δ−μ)/[(1−α)p/σ2+α tr (Q)], whereQ is a knownp×p diagonal matrix and 0≦α≦1. Two classes of minimax estimators are obtained for μ whenp≦3; the first is a new result and the second is a generalization of a result of Strawderman (1973,Ann. Statist.,1, 1189–1194). A proper Bayes estimator is also obtained which is shown to satisfy the conditions of the second class of minimax
estimators. The paper concludes by discussing the estimation of μ relative to another convex loss function.
This work was supported by the Army, Navy and Air Force under Office of Naval Research Contract No. N00014-80-C-0093. Reproduction
in whole or in part is permitted for any purpose of the United States Government. 相似文献
103.
Ali M. Mousa 《Applied Surface Science》2007,254(4):1215-1219
A simple and cheap method has been developed for the deposition of lead telluride thin films on glass substrates by pulsed Nd:YAG laser evaporation of lead telluride pellets made of high purity Pb and Te powders.Preliminary characterization of the crystallographic and optical properties of the films has been performed as a function of the substrate temperature.The influence of deposition conditions on the sheet resistance of these thin films has been studied. Both deposition temperature, nitrogen pressure during deposition, and addition of Ga and As impurities in the source pellets have been considered. 相似文献
104.
Kaolin-filled polypropylene (PP) composites with various kaolin content, processing temperature and shear histories were compounded
using a heated two roll-mill. Prior to thermal analysis, the samples were subjected to extrusion process via capillary rheometer.
The influences of kaolin content, processing temperature and shear stress on crystallization of all samples, including isothermal
and nonisothermal crystallization behaviour were investigated by differential scanning calorimetry (DSC). The results showed
that the increasing kaolin content, processing temperature and shear stress have shifted the crystallization exothermic peak
to higher temperature and reduced the overall crystallization time. 相似文献
105.
Michael E. Deary Salem M. Mousa D. Martin Davies 《Journal of inclusion phenomena and macrocyclic chemistry》2012,74(1-4):77-86
This paper presents a thermodynamic study of the rate and equilibria processes involved in the α-cyclodextrin mediated reaction of a range of 4-substituted phenyl methyl sulfides with two peroxyacids of different binding affinities. The results for the inclusion processes show that the formation of 1:1 and 2:1 (host:guest) complexes between α-cyclodextrin and phenyl methyl sulfides are generally enthalpically controlled, particularly so for the 2:1 complexes, as might be expected for a ternary complex. The data from this series of sulfides is presented as enthalpy-entropy compensation plots, yielding slopes of unity for each inclusion process. The formation of a 1:1 complex between cyclodextrin and the strongly associating 3-chloroperbenzoic acid (MCPBA) is also enthapically controlled. The other peroxyacid used, peroxomonosulfate, does not bind to α-cyclodextrin to any measurable degree. As described in our original study of this reaction system (Davies and Deary in J Chem Soc Perkin Trans 2:2423–2430, 1996), catalysis by α-cyclodextrin is effected by activation of the peroxide as a result its inclusion within the cyclodextrin cavity; hence for reactions of phenyl methyl sulfides with MCPBA, catalysis is observed, but is absent for PMS. In this study the reaction rates are analysed using the transition state pseudo-equilibrium approach of Tee (Carbohydr Res 192:181–195, 1989), whereby the transition state pseudoequilibrium constant K TS reflects the stabilisation imparted to the transition state by the association with one molecule of cyclodextrin. Enthalpy- entropy compensation plots for K TS give slopes close to unity; this is the first reported example of such plots being applied to transition state pseudoequilibrium constants. 相似文献
106.
107.
Waheed A. Al-Masry Emad M. Ali Saleh A. Alshebeili Fouad M. Mousa 《Journal of Saudi Chemical Society》2010,14(3):269-280
This paper deals with application of non-invasive electrical capacitance tomography to study the hydrodynamics of shallow bed bubble columns. Two bubble columns with different height to diameter ratio were used. Air–kerosene system that represents dielectric two-phase mixture was investigated. The ECT provided good measurement of the gas holdup at different gas velocities compared to the classical pressure measurements. The ECT was able to provide the gas hold up and the bubble velocities distribution across the column diameter at different gas velocities. The study revealed that spatial gas holdup and bubble velocity distributions are sharp with parabolic shape in the small bubble column (HD/DC = 5). However, in the large bubble column (HD/DC = 4) the gas holdup and bubble velocity profiles were flatter indicating improvement in the mixing homogeneity and leading to well-mixed reactor. 3D graphical visualization of the flow regimes and transition points were also examined using the ECT. In the small bubble column flow regimes were heterogeneous to slugs flow especially at high flow rate, resulted in downward flow near the walls and imperfect mixing. 相似文献
108.
Novel fluorescent polyetherimides containing bulky triaryl imidazole pendant and ether linkage in the main chains were prepared from a diamine, 2,2-phenoxy-bis[4-amino-2(4,5-diphenyl-2H-imidazole-2-yl)]propane, and commercially available dianhydrides. All the resulting polymers were amorphous with inherent viscosities ranged from 0.45 to 0.75 dl/g and were readily soluble in many organic solvents which could be solution-cast into transparent and tough films. They had useful levels of thermal stability associated with relatively high T g (245?C254°C), 10% weight loss temperatures in excess of 500°C, and char yields at 600°C in air up to 62%. These polymers exhibited strong UV-vis absorption maxima in solution and in solid state. Photoluminescence efficiency of the polyetherimides was affected by their chemical structure with quantum yields in the range 10?C28%. 相似文献
109.
We study the dynamics of the von Neumann entropy, Wehrl entropy, and Wehrl phase distribution for a single four-level ladder-type atom interacting with a one-mode cavity field taking into account the atomic motion. We obtain the exact solution of the model using the Schr¨odinger equation under specific initial conditions. Also we investigate the quantum and classical quantifiers of this system in the nonresonant case. We examine the effects of detuning and the atomic motion parameter on the entropies and their density operators. We observe an interesting monotonic relation between the different physical quantities in the case of nonmoving and moving atoms during the time evolution. We show that both the detuning and the atomic motion play important roles in the evolution of the Wehrl entropy, its marginal distributions, entanglement, and atomic populations. 相似文献
110.
Mahmoud Jourabian Mousa Farhadi Ahmad Ali Rabienataj Darzi 《Applied Mathematical Modelling》2013,37(20-21):8813-8825
Heat transfer enhancement of water-(Ice) as a phase change material (PCM) through dispersion of Cu-nanoparticles is the centerpiece of this research study. The nanoparticle-enhanced phase change material (NEPCM) demonstrates increased thermal conductivity and decreased melting time in comparison with the conventional PCM. An enthalpy-based lattice Boltzmann method (LBM) with a double distribution function (DDF) model is implemented to trace phase change front in a cylindrical-horizontal annul. The subcooling case is neglected and Prandtl number, Stefan number and Rayleigh number are fixed to 6.2, 1 and 105, respectively. In addition, the effects of varying the position of heated cylinder and nanoparticle volume fractions on the transient isotherms and liquid fractions are discussed. 相似文献