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11.
Hassan Keypour Ahmad Ali Dehghani-Firouzabadi Majid Rezaeivala Sadegh Salehzadeh 《合成通讯》2013,43(7):1136-1142
A new Schiff base cryptand (L) has been prepared via [2 + 2] condensation of 1,3,5-tris(2-formylphenoxymethyl)benzene (1) with 1,3,5-tris(aminomethyl)benzene trishydrochloride (2) in the presence of Ba(II) ion. The analytical data show that the Ba(II) cation is not retained by the product. Thus it seems that the role of the Ba(II) ion is to organize the transition state preceding the formation of the cryptand. 相似文献
12.
Sadeghi Mohamad Sadegh Anadalibkhah Naghmeh Ghasemiasl Ramin Armaghani Taher Dogonchi Abdul Sattar Chamkha Ali J. Ali Hafiz Asadi Amin 《Journal of Thermal Analysis and Calorimetry》2022,147(1):1-22
Journal of Thermal Analysis and Calorimetry - The ultimate goal of the present review paper is to summarize and discuss the findings of the most recently published literature on natural convection... 相似文献
13.
Use of citric acid as a chelating agent and fuel, ammonium nitrate as fuel, boric acid as flux material and silica as supports, CaWO4:Ln3+@SiO2 (Ln = Er and Tm) nanoparticles were synthesized via a combustion reaction at 800 °C. Characterization of the samples was performed by X-ray diffractometer (XRD), reflectance UV–Vis spectrophotometer, fluorescence spectrophotometer (PL) and transmission electron microscope (TEM). XRD patterns showed that tetragonal crystalline structure of scheelite and silica supports were formed, and that the formation of a silica support could enhance the luminescence intensity of CaWO4:Ln3+. The reflectance UV–Vis and PL spectra indicated the broad absorption band of WO4 2? groups about 240 nm, the WO4 2? wide excitation band with maximum at 240 nm, a broad emission band of WO4 2? with maximum about 420 nm, and characteristic emissions of Ln3+ ions. According to the TEM analysis, CaWO4:Er3+@SiO2 and CaWO4:Tm3+@SiO2 nanoparticles have almost the same morphology with average particle sizes about 50 nm. 相似文献
14.
Fakhari Amir Hossein Shafaghat Rouzbeh Jahanian Omid Ezoji Hossein Motallebi Hasankola Seyed Sadegh 《Journal of Thermal Analysis and Calorimetry》2020,139(4):2455-2464
Journal of Thermal Analysis and Calorimetry - Due to global concerns about the emissions, limited hydrocarbon fuel resources and high fuel prices, a lot of researches have been done to improve the... 相似文献
15.
Kouroush Sadegh Zadeh 《Journal of computational physics》2011,230(3):664-679
Numerical solutions of flow equation in fluid content-based form or in fluid pressure head-based form are often tradeoffs between speed, accuracy, and convenience. The fluid-content based form can be solved quite rapidly with low CPU time and perfect mass balance. However, it cannot be used in saturated regions (as diffusivity function becomes infinite) and strictly becomes invalid in composite, layered, and real heterogeneous porous materials, due to singularity and discontinuity in fluid content profile. This formulation also gives misleading impression that gradient in fluid content causes the flow of fluid in porous materials, where in reality gravity and fluid pressure potential gradient produce the motion. The pressure head-based form, on the other hand, is more flexible but due to its highly nonlinear nature is much more time-consuming and produces poor global mass balance for dry initial conditions. Very fine spatial and temporal discretizations are needed to maintain mass balance property for these scenarios. The mixed form of the flow equation partially solves these issues as it maintains acceptable mass balance and is applicable to layered, heterogeneous, and composite fractured foundations. However, it is only applicable in unsaturated zones. In this study, a switching algorithm was proposed and implemented in which the mass conservative mixed form and the pressure head-based form were, respectively, used in the unsaturated and saturated zones of an initial-boundary value flow problem involving a variably saturated porous medium. The algorithm showed excellent agreement with a reference solution, obtained on a very fine spatiotemporal mesh. The simulator was then calibrated with several real-world large-scale experimental datasets. In all cases, the proposed algorithm exhibited close agreements with the experimental time–space series. The algorithm poses excellent mass balance property and can easily be used in both saturated and unsaturated regions without special treatment of fluid content discontinuities in heterogeneous and layered porous media. The proposed algorithm can also be extended to simulate multiphase and multidimensional flow problems. 相似文献
16.
We show that the nonlinear equation that describes nonparaxial Kerr propagation, together with the already reported bright-soliton solutions, admits of (1 + 1)D dark-soliton solutions. Unlike their paraxial counterparts, dark solitons can be excited only if their asymptotic normalized intensity u2infinity is below 3/7; their width becomes constant when u2infinity approaches this value. 相似文献
17.
In this paper, a new channel drop filter in two dimensional photonic crystals with mirror cavities is proposed. In the structure,
three cavities are used. One is used for a resonant tunneling-based channel drop filter. The others are used to realize reflection
feedback in the bus waveguide, which consists of a point defect micro-cavity side-coupled to a waveguide. The simulation results
by using the finite-difference time-domain method conclude 98% output efficiency. 相似文献
18.
Synthesis, characterization and properties of novel thermally stable poly(urethane-oxazolidone) elastomers 总被引:2,自引:0,他引:2
Oxazolidone-incorporated polyurethane elastomers based on hydroxyl terminated polycaprolactone, were synthesized and characterized. Reaction of epoxy-terminated polyurethane with isocyanate librated from a blocked polyisocyanate was the strategy followed. The reaction condition was optimized through preparation of model oxazolidones. Epoxy-terminated polyurethanes were prepared from reaction of glycidol with NCO-terminated polyurethane prepolymers and curing agent was synthesized from the reaction of trimethylol propane, toluene diisocyanate and N-methyl-aniline. Incorporation of heterocyclic oxazolidone groups into the polyurethane backbone caused improvements in thermal and mechanical properties. Investigation of structure-property relationship for prepared elastomers showed that the main determining factors for observed properties were crosslink density, crystallinity and content of oxazolidone rings. 相似文献
19.
S. Sadegh Hassani F. Salehirad H. R. Aghabozorg Z. Sobat 《Crystal Research and Technology》2010,45(2):183-187
AFM is a powerful tool for imaging nanoscale surface features; it provides two and three dimensional crystal structure images and other information about actual surface of zeolite crystallites. In this paper, nanosized zeolite L is synthesized in different crystallization times and a study of crystal growth of zeolite L is reported using atomic force microscopy (AFM). X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques are used for characterization of the as synthesized samples. TEM and two‐dimensional AFM images indicate that the zeolite particles are in a nano‐range and they have hexagonal structure. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
S. Kimiagar M. Sadegh Movahed S. Khorram M. Reza Rahimi Tabar 《Journal of statistical physics》2011,143(1):148-167
Using the Markovian method, we study the stochastic nature of electrical discharge current fluctuations in the Helium plasma.
Sinusoidal trends are extracted from the data set by the Fourier-Detrended Fluctuation analysis and consequently cleaned data
is retrieved. We determine the Markov time scale of the detrended data set by using likelihood analysis. We also estimate
the Kramers-Moyal’s coefficients of the discharge current fluctuations and derive the corresponding Fokker-Planck equation.
In addition, the obtained Langevin equation enables us to reconstruct discharge time series with similar statistical properties
compared with the observed in the experiment. We also provide an exact decomposition of temporal correlation function by using
Kramers-Moyal’s coefficients. We show that for the stationary time series, the two point temporal correlation function has
an exponential decaying behavior with a characteristic correlation time scale. Our results confirm that, there is no definite
relation between correlation and Markov time scales. However both of them behave as monotonic increasing function of discharge
current intensity. Finally to complete our analysis, the multifractal behavior of reconstructed time series using its Keramers-Moyal’s
coefficients and original data set are investigated. Extended self similarity analysis demonstrates that fluctuations in our
experimental setup deviates from Kolmogorov (K41) theory for fully developed turbulence regime. 相似文献