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991.
Mohammad Mahdavi Mehdi Asadi Mahsa Khoshbakht Mina Saeedi Mohammad Bayat Alireza Foroumadi Abbas Shafiee 《Helvetica chimica acta》2016,99(5):378-383
A series of novel quinazolin‐4(3H)‐one derivatives were efficiently synthesized starting from isatoic anhydride. First, reaction of isatoic anhydride and amines in H2O at room temperature afforded 2‐aminobenzamides. Then, CuBr/Et3N promoted reaction of 2‐aminobenzamides and different aryl isothiocyanates in DMF at 80° afforded the title compounds in good yield. 相似文献
992.
Aboozar Taherizadeh Daniel E. Green Abbas Ghaei Jeong-Whan Yoon 《International Journal of Plasticity》2010
In this paper an anisotropic material model based on non-associated flow rule and mixed isotropic–kinematic hardening was developed and implemented into a user-defined material (UMAT) subroutine for the commercial finite element code ABAQUS. Both yield function and plastic potential were defined in the form of Hill’s [Hill, R., 1948. A theory of the yielding and plastic flow of anisotropic metals. Proc. R. Soc. Lond. A 193, 281–297] quadratic anisotropic function, where the coefficients for the yield function were determined from the yield stresses in different material orientations, and those of the plastic potential were determined from the r-values in different directions. Isotropic hardening follows a nonlinear behavior, generally in the power law form for most grades of steel and the exponential law form for aluminum alloys. Also, a kinematic hardening law was implemented to account for cyclic loading effects. The evolution of the backstress tensor was modeled based on the nonlinear kinematic hardening theory (Armstrong–Frederick formulation). Computational plasticity equations were then formulated by using a return-mapping algorithm to integrate the stress over each time increment. Either explicit or implicit time integration schemes can be used for this model. Finally, the implemented material model was utilized to simulate two sheet metal forming processes: the cup drawing of AA2090-T3, and the springback of the channel drawing of two sheet materials (DP600 and AA6022-T43). Experimental cyclic shear tests were carried out in order to determine the cyclic stress–strain behavior and the Bauschinger ratio. The in-plane anisotropy (r-value and yield stress directionalities) of these sheet materials was also compared with the results of numerical simulations using the non-associated model. These results showed that this non-associated, mixed hardening model significantly improves the prediction of earing in the cup drawing process and the prediction of springback in the sidewall of drawn channel sections, even when a simple quadratic constitutive model is used. 相似文献
993.
Dr. Muhammad Humayun Prof. Mohamed Bououdina Dr. Muhammad Usman Prof. Dr. Abbas Khan Prof. Wei Luo Prof. Chundong Wang 《Chemical record (New York, N.Y.)》2024,24(3):e202300350
Gas sensors are crucial in environmental monitoring, industrial safety, and medical diagnostics. Due to the rising demand for precise and reliable gas detection, there is a rising demand for cutting-edge gas sensors that possess exceptional sensitivity, selectivity, and stability. Due to their tunable electrical properties, high-density surface-active sites, and significant surface-to-volume ratio, nanomaterials have been extensively investigated in this regard. The traditional gas sensors utilize homogeneous material for sensing where the adsorbed surface oxygen species play a vital role in their sensing activity. However, their performance for selective gas sensing is still unsatisfactory because the employed high temperature leads to the poor stability. The heterostructures nanomaterials can easily tune sensing performance and their different energy band structures, work functions, charge carrier concentration and polarity, and interfacial band alignments can be precisely designed for high-performance selective gas sensing at low temperature. In this review article, we discuss in detail the fundamentals of semiconductor gas sensing along with their mechanisms. Further, we highlight the existed challenges in semiconductor gas sensing. In addition, we review the recent advancements in semiconductor gas sensor design for applications from different perspective. Finally, the conclusion and future perspectives for improvement of the gas sensing performance are discussed. 相似文献
994.
Muhammad Zahid SyedRaziullah Husani Muhammad Abbas Yuanjiang Pan AmirReza Jassbi Muhammad Asim Masood Parvez Wolfgang Voelter ViqarUddin Ahmad 《Helvetica chimica acta》2001,84(7):1980-1988
A reinvestigation of Euphorbia decipiens with a modified extraction procedure resulted in the isolation and structure elucidation of eight new myrsinane‐type diterpene esters (see 3 – 10 ). Moreover, revised structures are proposed for decipinone B ( 1 ) and C ( 2 ) on the basis of X‐ray‐diffraction analyses. The structures of the compounds were elucidated by means of different spectroscopic methods, including 1D‐ and 2D‐NMR studies. 相似文献
995.
Structure and Magnetic Properties of Bis{3‐amino‐1,2,4‐triazolium(1+)}pentafluoromanganate(III): (3‐atriazH)2[MnF5] The crystal structure of (3‐atriazH)2[MnF5], space group P1, Z = 4, a = 8.007(1) Å, b = 11.390(1) Å, c = 12.788(1) Å, α = 85.19(1)°, β = 71.81(1)°, γ = 73.87(1)°, R = 0.034, is built by octahedral trans‐chain anions [MnF5]2–∞ separated by the mono‐protonated organic amine cations. The [MnF6] octahedra are strongly elongated along the chain axis (<Mn–Fax> 2.135 Å, <Mn–Feq> 1.842 Å), mainly due to the Jahn‐Teller effect, the chains are kinked with an average bridge angle Mn–F–Mn = 139.3°. Below 66 K the compound shows 1D‐antiferromagnetism with an exchange energy of J/k = –10.8 K. 3D ordering is observed at TN = 9.0 K. In spite of the large inter‐chain separation of 8.2 Å a remarkable inter‐chain interaction with |J′/J| = 1.3 · 10–5 is observed, mediated probably by H‐bonds. That as well as the less favourable D/J ratio of 0.25 excludes the existence of a Haldene phase possible for Mn3+ (S = 2). 相似文献
996.
A convenient synthesis of 26‐ to 28‐membered thiamacrocyclic dilactams 8 was achieved via base‐catalyzed condensation reaction of bis‐2‐cyanoacetamides 4 with dialdehyde derivatives 7 . The reaction was assumed to be geometrically stereoselective, affording E, E′‐configuration as the only isolable isomer. N, N′‐[Alkanediylbis(thia‐2,1‐phenylene)]bis[2‐cyanoacetamides] 4 were obtained by the reaction of cyanoacetic acid with the corresponding diamine hydrochlorides 3 . © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:249–254, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20292 相似文献
997.
Ibrahim A. Abbas 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(1):41-50
In this paper, we constructed the equations of generalized magneto-thermoelasticity in a perfectly conducting medium. The
formulation is applied to generalizations, the Lord–Shulman theory with one relaxation time, and the Green–Lindsay theory
with two relaxation times, as well as to the coupled theory. The material of the cylinder is supposed to be nonhomogeneous
isotropic both mechanically and thermally. The problem has been solved numerically using a finite element method. Numerical
results for the temperature distribution, displacement, radial stress, and hoop stress are represented graphically. The results
indicate that the effects of nonhomogeneity, magnetic field, and thermal relaxation times are very pronounced. In the absence
of the magnetic field or relaxation times, our results reduce to those of generalized thermoelasticity and/or classical dynamical
thermoelasticity, respectively. Results carried out in this paper can be used to design various nonhomogeneous magneto-thermoelastic
elements under magnetothermal load to meet special engineering requirements.
An erratum to this article can be found at 相似文献
998.
This paper presents the analytic solution for flow of a magnetohydrodynamic (MHD) Sisko fluid through a porous medium. The
non-linear flow problem in a porous medium is formulated by introducing the modified Darcy’s law for Sisko fluid to discuss
the flow in a porous medium. The analytic solutions are obtained using homotopy analysis method (HAM). The obtained analytic
solutions are explicitly expressed by the recurrence relations and can give results for all the appropriate values of material
parameters of the examined fluid. Moreover, the well-known solutions for a Newtonian fluid in non-porous and porous medium
are the limiting cases of our solutions. 相似文献
999.
Abbas‐Ali Shaik Martin Richter Hans R. Kricheldorf Ralph‐P. Krüger 《Journal of polymer science. Part A, Polymer chemistry》2001,39(19):3371-3382
Copolyesters with an alternating sequence of terephthalic acid and aliphatic dicarboxylic acids were prepared with three different methods. First, dicarboxylic acid dichlorides were reacted with bis(2‐hydroxyethyl)terephthalate (BHET) in refluxing 1,2‐dichlorobenzene. Second, the same monomers were polycondensed at 0–20 °C in the presence of pyridine. Third, dicarboxylic acid dichlorides and silylated BHET were polycondensed in bulk. Only this third method gave satisfactory molecular weights. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry revealed that the copolyesters prepared by the pyridine and silyl methods might have contained considerable fractions of cyclic oligoesters and polyesters despite the absence of transesterification and backbiting processes. The alternating sequences and thermal properties were characterized with 1H NMR spectroscopy and differential scanning calorimetry measurements, respectively. In agreement with the alternating sequence, all copolyesters proved to be crystalline, but the crystallization was extremely slow [slower than that of poly(ethylene terephthalate)]. A second series of alternating copolyesters was prepared by the polycondensation of silylated bis(4‐hydroxybut‐ yl)terephthalate with various aliphatic dicarboxylic acid dichlorides. The resulting copolyesters showed significantly higher rates of crystallization, and the melting temperatures were higher than those of the BHET‐based copolyesters. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3371–3382, 2001 相似文献
1000.
Total and full-energy peak efficiencies, coincidence correction factors and the source self-absorption of a p-type coaxial HPGe detector for cylindrical sources have been calculated using direct analytical expressions. In the experiments gamma aqueous sources containing several radionuclides covering the energy range from 60 to 1836 keV were used. By comparison, the theoretical and experimental full-energy peak efficiency values are in good agreement. 相似文献