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41.
Nayereh Soltani Elias Saion Maryam Erfani Khadijeh Rezaee Ghazaleh Bahmanrokh Gregor P. C. Drummen Afarin Bahrami Mohd Zobir Hussein 《International journal of molecular sciences》2012,13(10):12412-12427
Zinc sulfide semiconductor nanoparticles were synthesized in an aqueous solution of polyvinyl pyrrolidone via a simple microwave irradiation method. The effect of the polymer concentration and the type of sulfur source on the particle size and dispersion of the final ZnS nanoparticle product was carefully examined. Microwave heating generally occurs by two main mechanisms: dipolar polarization of water and ionic conduction of precursors. The introduction of the polymer affects the heating rate by restriction of the rotational motion of dipole molecules and immobilization of ions. Consequently, our results show that the presence of the polymer strongly affects the nucleation and growth rates of the ZnS nanoparticles and therefore determines the average particle size and the dispersion. Moreover, we found that PVP adsorbed on the surface of the ZnS nanoparticles by interaction of the C–N and C=O with the nanoparticle’s surface, thereby affording protection from agglomeration by steric hindrance. Generally, with increasing PVP concentration, mono-dispersed colloidal solutions were obtained and at the optimal PVP concentration (5%), sufficiently small size and narrow size distributions were obtained from both sodium sulfide and thioacetamide sulfur sources. Finally, the sulfur source directly influences the reaction mechanism and the final particle morphology, as well as the average size. 相似文献
42.
Mohammad Taghi Hamed Mosavian Alireza Bakhtiari Samaneh Sahebian 《Polymer-Plastics Technology and Engineering》2013,52(2):214-219
This study evaluated the effects of alumina (Al2O3) particles on thermal properties of High Density Polyethylene (HDPE). HDPE and HDPE/5, 10 & 15 wt% Al2O3 composites were prepared by compression molding. Differential scanning calorimetery (DSC) was used to analyze the thermal and crystallization behavior of the samples. The results indicated that the alumina particles affected the crystallization behavior of HDPE matrix, significantly. However, the DSC results showed that alumina content did not influence the melting temperature of HDPE in this composite. The results also showed that the incorporation of alumina particles caused the decrease of specific heat capacity coefficient and entropy. 相似文献
43.
44.
Ali Taghvaie Nakhjiri Amir Heydarinasab Omid Bakhtiari Toraj Mohammadi 《中国化学工程学报》2018,26(9):1845-1861
The present paper renders a modeling and a 2D numerical simulation for the removal of CO2 from CO2/CH4 gaseous stream utilizing sodium hydroxide (NaOH), monoethanolamine (MEA) and triethanolamine (TEA) liquid absorbents inside the hollow fiber membrane contactor. Counter-current arrangement of absorbing agents and CO2/CH4 gaseous mixture flows are implemented in the modeling and numerical simulation. Non-wetting and partial wetting modes of operation are considered where in the partial wetting mode, CO2/CH4 gaseous mixture and liquid absorbents fill the membrane pores. The deteriorated removal of CO2 in the partial wetting mode of operation is mainly due to the mass transfer resistance imposed by the liquid in the pores of membrane. The validation of numerical simulation is done based on the comparison of simulation results of CO2 removal using NaOH and experimental data under non-wetting mode of operation. The comparison illustrates a desirable agreement with an average deviation of less than 5%. According to the results, MEA provides higher efficiency for CO2 removal in comparison with the other liquid absorbents. The order for CO2 removal performance is MEA > NaOH > TEA. The influence of non-wetting and partial wetting modes of operation on CO2 removal are evaluated in this article as one of the novelties. Besides, the percentage of CO2 sequestration as a function of gas velocity for various percentages of membrane pores wetting ranging from 0 (non-wetting mode of operation) to 100% (complete wetting mode of operation) is studied in this research paper, which can be proposed as the other novelty. The results indicate that increase in some operational parameters such as module length, membrane porosity and absorbents concentration encourage the removal percentage of CO2 from CO2/CH4 gaseous mixture while increasing in membrane tortuosity, gas velocity and initial CO2 concentration has unfavorable influence on the separation efficiency of CO2. 相似文献
45.
Multimedia Tools and Applications - One of the main challenges in hierarchical object classification is the derivation of the correct hierarchical structure. The classic way around the problem is... 相似文献
46.
SrSO4:Dy,Tb nanocrystalline with crystalline size in the range of 44–54 nm was prepared by co-precipitation method followed by thermal treatment and characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive X-ray spectroscopy(EDX) and UV-visible spectrometry. Our results provided direct evidence of incorporation of impurities into nanocrystalline SrSO4. The thermoluminescence(TL) properties of SrSO4:Dy,Tb nanocrystalline pellets irradiated with gamma rays at different doses were studied. The TL glow curve of SrSO4:Dy,Tb nanocrystalline pellets had a prominent peak at around 490 K and a small peak at around 430 K. The major peak in the TL glow curve was almost resolved from other peaks, which was analyzed using Chen's peak shape method to determine the TL kinetic parameters such as activation energy, E and kinetic order, b. The intensity of main dosimetric peak of SrSO4:Dy,Tb nanocrystalline pellets at around 490 K increased linearly with the increase in gamma dose. The TL response was linear in the range of 0.1–7 kGy. These properties made it a candidate as a dosimeter to be used for estimating the high dose of gamma rays. 相似文献
47.
Ganchev S.I. Qaddoumi N. Bakhtiari S. Zoughi R. 《IEEE transactions on instrumentation and measurement》1995,44(6):1023-1029
The application of open-ended coaxial sensors for dielectric measurement of finite thickness composite sheets is studied. Expressions for calculation of the complex aperture admittance for two geometries are presented. These expressions are used to calculate the dielectric constant of infinite half-space as well as finite thickness slabs. A more efficient method of such calculations, using a personal computer, for low to medium loss dielectrics is demonstrated. The question of when a dielectric layer may be considered as infinitely thick is also addressed, and examples are presented. A different calibration technique (compared to the conventional ones) is described and successfully implemented. This calibration technique utilizes a dielectric sheet with known dielectric properties and thickness. Measurements for different airgaps between the open-ended coaxial line and the dielectric sheet are used to perform and enhance the calibration. The results of this calibration technique and several subsequent measurements are presented and discussed 相似文献
48.
Taher Lotfi Parisa Bakhtiari Alicia Cordero Katayoun Mahdiani Juan R. Torregrosa 《国际计算机数学杂志》2015,92(9):1921-1934
It is attempted to put forward a new multipoint iterative method of sixth-order convergence for approximating solutions of nonlinear systems of equations. It requires the evaluation of two vector-function and two Jacobian matrices per iteration. Furthermore, we use it as a predictor to derive a general multipoint method. Convergence error analysis, estimating computational complexity, numerical implementation and comparisons are given to verify applicability and validity for the proposed methods. 相似文献
49.
Hamed Bakhtiari Mahdi Karimi Sina Rezazadeh 《Journal of Intelligent Manufacturing》2016,27(2):463-473
Recently, twist extrusion has found extensive applications as a novel method of severe plastic deformation for grain refining of materials. In this paper, two prominent predictive models, response surface method and artificial neural network (ANN) are employed together with results of finite element simulation to model twist extrusion process. Twist angle, friction factor and ram speed are selected as input variables and imposed effective plastic strain, strain homogeneity and maximum punch force are considered as output parameters. Comparison between results shows that ANN outperforms response surface method in modeling twist extrusion process. In addition, statistical analysis of response surface shows that twist extrusion and friction factor have the most and ram speed has the least effect on output parameters at room temperature. Also, optimization of twist extrusion process was carried out by a combination of neural network model and multi-objective meta-heuristic optimization algorithms. For this reason, three prominent multi-objective algorithms, non-dominated sorting genetic algorithm, strength pareto evolutionary algorithm and multi-objective particle swarm optimization (MOPSO) were utilized. Results showed that MOPSO algorithm has relative superiority over other algorithms to find the optimal points. 相似文献
50.
Esmail Vessally Khadijeh Didehban Robab Mohammadi Akram Hosseinian 《Journal of Sulfur Chemistry》2018,39(3):332-349
Transition-metal-catalyzed C–S cross-coupling reactions comprise one of the most efficient methods for the synthesis of biologically and synthetically important aryl sulfide derivatives. Among the various solvents used in this cross-coupling reaction (ionic liquids, water, organic, and aqueous biphasic solvents), neat water have attracted notable interest in recent years due to its properties such as non-toxicity, non-flammability, renewability, and widely availability compared with other solvents. Since several catalytic systems for this green synthesis of aryl sulfides have been reported from 2007 to present, a comprehensive review on this interesting field seems to be timely. In this study, we discuss the most representative and interesting reports on the synthesis of aryl sulfides via metal-catalyzed cross-coupling of thiols with aryl halides in water. Mechanistic aspects of the reactions are considered and discussed in detail. 相似文献