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991.
Mujahid Abbas Safeer Hussain Khan Abdul Rahim Khan Ravi P. Agarwal 《Applied Mathematics Letters》2011,24(2):97-102
In this paper, we introduce a new one-step iterative process to approximate common fixed points of two multivalued nonexpansive mappings in a real uniformly convex Banach space. We establish weak and strong convergence theorems for the proposed process under some basic boundary conditions. 相似文献
992.
The Use of Ultrasound in pipette‐tip solid‐phase extraction based on CuS@ZnS@Fe3O4‐CNTs for pre‐concentration of tartrazine in water samples 下载免费PDF全文
This paper report a novel strategy for synthesis and application of CuS@ZnS@Fe3O4‐CNTs composite which has great potentials as artificial receptor for tartrazine trapping due to its ultrahigh surface area and functionality which is related to application of electrochemical route. A durable and economical pipette‐tip CuS@ZnS@Fe3O4‐CNTs nano‐composite miniaturized solid phase extraction coupled with UV‐Vis spectrophotometry was developed for clean‐up and determination of tartrazine from various water samples. Undoubtedly, presence of mild‐intensity/frequency ultrasound irradiation played a key role for reducing consumption of eluent volume by broking hydrogen bonds between retained analyte and sorbent. The influence of factors including pH, sorbent dosage, sonication time and eluent volume were investigated and optimum conditions were obtained using experimental design methodology. Under optimized conditions, good extraction efficiencies for the analyte were obtained with no matrix interference in the subsequent UV‐Vis. Good linearity for tartrazine in the range of 20‐5000 ng mL‐1 with correlation coefficients of R2 ≥ 0.99 and low detection limit close to 4.76 ng mL‐1 reveals high applicability of method for trace analysis. 相似文献
993.
Mostafa Khoshsefat Abbas Dechal Saeid Ahmadjo S. Mohammad M. Mortazavi Gholamhossein Zohuri Joao B.P. Soares 《应用有机金属化学》2019,33(6)
A series of mononuclear (M1 and M2) and dinuclear (C1–C6) Ni α‐diimine catalysts activated by modified methylaluminoxane were used in polymerization of ethylene. Catalyst C2 bearing the optimum bulkiness showed the highest activity (1.6 × 106 g PE (mol Ni)?1 h?1) and the lowest short‐chain branching (32.5/1000 C) in comparison to the dinuclear and mononuclear analogues. Although the mononuclear catalysts M1 and M2 polymerized ethylene to a branched amorphous polymer, the dinuclear catalysts led to different branched semicrystalline polyethylenes. Homogeneity and heterogeneity in the microstructure of the polyethylene samples was observed. Different trends for each catalyst were assigned to syn and anti stereoisomers. In addition, thermal behavior of the samples in the successive self‐nucleation and annealing technique exhibited different orders and intensities from methylene sequences and lamellae thickness in respect of each stereoisomer behavior. Higher selectivity of hexyl branches obtained by catalyst C2 showed a cooperative effect between the centers. The results also revealed that for catalysts C5 and C6, selectivity of methyl branches led to very high endotherms and crystalline sequences with melting temperatures higher than that of 100% crystalline polyethylene indicating ethylene/propylene copolymer analogues. For catalysts C3 and C4, more vinyl end groups were a result of the long distance between the Ni centers. Kinetic profiles of polymerization along with a computational study of the precatalysts and catalysts demonstrated that there is a direct relation between rate constant, energy interval of catalyst and precatalyst, and interaction energy of Et···methyl cationic active center (Et···MCC or π–Comp.). Based on this, narrow energy interval (activation energy) of precatalyst and catalyst leads to fast and higher activation rate (catalyst M2), and strong interaction of ethylene and catalyst leads to high monomer uptake and productivity (catalyst C2). Moreover, theoretical parameters including electron affinity, Mulliken charge on Ni, chemical potential and hardness, and global electrophilicity showed optimum values for C2. 相似文献
994.
In this paper, a linear viscoelastic system is considered where the viscoelastic force depends on the past history of motion via a convolution integral over an exponentially decaying kernel function. The free‐motion equation of this nonviscous system yields a nonlinear eigenvalue problem that has a certain number of real eigenvalues corresponding to the nonoscillatory nature. The quality of the current numerical methods for deriving those eigenvalues is directly related to damping properties of the viscoelastic system. The main contribution of this paper is to explore the structure of the set of nonviscous eigenvalues of the system while the damping coefficient matrices are rank deficient and the damping level is changing. This problem will be investigated in the cases of low and high levels of damping, and a theorem that summarizes the possible distribution of real eigenvalues will be proved. Moreover, upper and lower bounds are provided for some of the eigenvalues regarding the damping properties of the system. Some physically realistic examples are provided, which give us insight into the behavior of the real eigenvalues while the damping level is changing. 相似文献
995.
Jahede Tekeykhah Seyed Mohsen Hosseini Gholamali Jalali Jalil Alavi Abbas Esmaili Sari 《声与振动》2019,53(6):263-276
Sound pollution is one of the most important urban problems which
endangers mental and physical health of the residents. This study was aimed to
assess the influence of different tree species, including Fraxinus rotundifolia,
Robinia pseudoacacia, Platanus orientalis, Platycladus orientalis, and Pinus
eldarica, in reducing noise pollution in the Abidar Forest Park. A further objective was to identify the contaminated areas of Sanandaj city and to propose suitable noise absorbent tree species in consistent conditions. For each tree stands
the noise measurements were performed during intervals at frequencies of 250,
500 and 1000 Hz, besides an open area with the same topography. With regards
to the second purpose, a total of 50 stations with residential, commercial, residentialcommercial, and green space applications were selected across the city. Equivalent
Continuous Sound Pressure Level (Leq) was determined in five replicates for 30
min. The measurements were performed under stable weather conditions and low
wind velocity at 17:00 (traffic peak) in summer and fall. All of the Leq values were
above the threshold noise level. The highest noise reduction was recorded in summer
(i.e., green season); Platanus and Platycladus species demonstrated the highest and
lowest noise absorption (31.43 dB and 22.28 dB, respectively). Furthermore, a
meaningful difference was observed between Leq values of commercial, residential,
commercial-residential, and green space urban applications, and the central parts of
the city showed noticeable noise pollution. Taken together, due to being exposed to
higher than the acceptable threshold noise level, the residents of Sanandaj will be
endangered to health problems in the near future; thus consideration should be given
to the noise pollution sources. 相似文献
996.
Cellulose - Nanocomposite hydrogel is helpful to provide a moist and ideal environment for wound healing. In this research study, a nanocomposite hydrogel was prepared based on schizophyllan (SPG)... 相似文献
997.
Seyed Ghorban Hosseini Abbas Eslami 《Journal of Thermal Analysis and Calorimetry》2010,101(3):1111-1119
In order to investigate relative reactivity of different oxidants in solid-state reactions of pyrotechnic mixtures, thermal
properties of Sn + Sr(NO3)2, Sn + Ba(NO3)2, and Sn + KNO3 pyrotechnic systems have been studied by means of TG, DTA, and DSC methods and the results compared with those of pure oxidants.
The apparent activation energy (E), ΔG
#, ΔH
#, and ΔS
# of the combustion processes were obtained from the DSC experiments. The results showed that the nature of oxidant has a significant
effect on ignition temperature, and the kinetic of the pyrotechnic mixtures’ reactions, and the relative reactivity of these
mixtures was found to obey in the following order: Sn + Sr(NO3)2 > Sn + Ba(NO3)2 > Sn + KNO3. 相似文献
998.
Abstract
The derivatization of a glassy carbon electrode surface was achieved with and without electrochemical reduction of various diazonium salts in acetonitrile solutions. The surfaces were characterized, before and after their attachment, by cyclic voltammetry and electrochemical impedance spectroscopy to evidence the formation of a coating on the carbon surface. The results were indicative of the presence of substituted phenyl groups on the investigated surface. Also, the effects of diazonium thin films at the surface of a glassy carbon electrode, modification time, and salt concentration on their electrochemical responses in the presence of the Fe(CN)63−/4− probe were investigated. Electrochemical impedance measurements indicated that the kinetics of electron transfer is slowed down when the time and the concentration used to modify the glassy carbon electrode are increased. We therefore modified a glassy carbon surface via its derivatization with and without electrochemical reduction of various diazonium salts in acetonitrile solution. 相似文献999.
Abbas Rahmati 《Tetrahedron letters》2010,51(22):2967-2970
A one-pot, three-component condensation reaction of an aldehyde, 3-amino-5-methylpyrazole and ethyl cyanoacetate in ethanol to give 4-aryl-3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitriles, in high yields, at reflux, using a catalytic amount of p-toluenesulfonic acid, is described. 相似文献
1000.
Abbas Moustafa 《Journal of sound and vibration》2009,325(3):532-360
The problem of modeling earthquake ground motions as design inputs for multi-degree-of-freedom inelastic structures is studied. The earthquake acceleration is expressed as a Fourier series modulated by an envelope function. The coefficients of the series representation are calculated such that the structure inelastic deformation is maximized subjected to predefined constraints. These constraints are taken to reflect known characteristics of recorded earthquakes such as upper bounds on the energy and peak values of the ground acceleration, velocity and displacement and upper and lower limits on the Fourier spectra of the ground acceleration. The material stress-strain behavior is modeled using bilinear and elastic-plastic relations. The resulting nonlinear optimization problem is solved by using the sequential quadratic optimization method. Issues related to various forms of energy dissipated by the inelastic structure are explored. The study also examines the effect of nonlinear damping models and the influence of the strain hardening ratio (ratio of the post-yield stiffness to the pre-yield stiffness) on the derived optimal earthquake and associated inelastic deformation. The formulation is demonstrated for a two-storey inelastic building frame with nonlinear damping. 相似文献