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991.
Dursun?Ali?KoseEmail author Hacali?Necefo?lu Onur??ahin Orhan?Büyükgüng?r 《Journal of chemical crystallography》2011,41(3):297-305
Abstract
The compound has been formed by mononuclear [Cu(C9H7O4)2(C6H6N2O)2(H2O)] units in which the metal ion as well as the water ligand lies on a twofold symmetry axis, so that only one acetylsalicylate ligand and one nicotinamide ligand are independent. The distortion from ideal five-coordinate geometries can be described best by the degree of trigonality τ. For a regular square-pyramidal (SQP) geometry the trigonality parameter is 0 and for a trigonal–bipyramidal (TBP) structure it increases to 1. The copper coordination geometry is that of a square pyramid (τ = 0.23), with the N atoms from nicotinamide ligands and the bonded carboxylate O atoms from acetylsalicylate ligands defining the quasi-planar square base. The apical site is occupied by the aqua ligand, a bond which coincides with the twofold symmetry axis and is thus exactly perpendicular to the basal plane. The thermal decomposition takes place in four steps: removing of moisture, dehydration of aqua ligand, the elimination of the nicotinamide (na) ligand and the decomposition of acetyl-groups and oxidation of salicylate ion ligands. In complex, all ligands are coordinated to the metal ion as monodendate. The IR spectra of the intermediate products showed similar results. 相似文献992.
Mahmoud Al-Refai Mohanad H. Masad Rajab Abu-El-Halawa Jamal N. Dawoud Mohammad M. Ibrahim Zaher Judeh Basem F. Ali 《Journal of chemical crystallography》2011,41(9):1335-1341
Abstract
The title compound crystallizes in the monoclinic space group C2/c space group, with unit cell dimensions of a = 15.6684(3) ?, b = 7.3974(2) ?, c = 21.2669(5) ?; β = 106.7770(10)° (Z = 8). In the title compound, NH4 +·C5HClNO2S4 –·1.5 H2O, the 1,4,2-dithiazine ring adopts a distorted half-chair conformation. The structure displays several cooperative intermolecular N/O–H···N/O/S hydrogen-bonding interactions, giving rise to a two-dimensional layers packing motif. The layers are built up from seven component entities formed via extensive intermolecular N/O–H···N/O/S hydrogen bonds involving 6-chlorothieno[2,3-e]-1,4,2-dithiazine-3(2H)-thione-1,1-dioxide anions, ammonium cations and water molecules. The geometry of the title compound was fully optimized using a Density functional B3LYP/6-31G(d) and B3LYP/6-31+G(d) methods and the results were consistent with experimental values. The binding energy and associated basis set superposition as well as the thermodynamic quantities were calculated. 相似文献993.
In this article, we studied the specific heat data of iron-based superconductors LaO1? x F x FeAs (x?=?0.1) and SmO1? x F x FeAs (x?=?0.13,?0.12, and 0.1). (i) The contribution of phonons in specific heat above Tc depends exponentially on temperature. (ii) The specific heat has different contributions, and they change differently at Tc . This change must be the effect of a physical function on heat capacity. Therefore, transition temperature is defined by thermal parameters. For LaO0.9F0.1FeAs and SmO0.87F0.13FeAs, a transition point was evaluated at 22.11 and 26.32?K, respectively. This is in close agreement with the midpoint transition temperatures obtained from dc resistivity and magnetization experiments, where the modified electronic heat capacity led to the approximate value of the transition point in two samples. The jump, ΔC/γT c, and the electronic and lattice heat capacity coefficients, γ and β, respectively, were evaluated. 相似文献
994.
M. M. Rashad M. Rasly H. M. El-Sayed A. A. Sattar I. A. Ibrahim 《Applied Physics A: Materials Science & Processing》2013,112(4):963-973
Polycrystalline Co2Z hexaferrite (Ba3Co2Fe24O41) powders have been prepared via two wet chemical routes: sol gel auto-combustion (SGA) and co-precipitation (CP) methods. The effects of synthesis conditions on the crystal structure, crystallite size, morphology, and magnetic properties were systematically studied. The results revealed that single Co2Z hexaferrite phase was obtained at relatively low temperature 1250 °C for 5 h via the SGA method whereas it was formed at 1300 °C for 6 h using the CP pathway. The microstructures of the pure powders appeared as a hexagonal platelet-like structure. The particle size of the pure Co2Z powders by CP method was higher than as obtained by the SGA method. The soft characteristic loops were obtained for single Co2Z hexaferrite phase synthesized using both routes. High saturation magnetization (M s =53.7 emu/g) was achieved for the Co2Z powder synthesized via the CP method compared with the formed single phase synthesized via the SGA method (M s =47.0 emu/g). Good dielectric and dynamic magnetic properties were obtained for the Co2Z powder synthesized via the SGA method in comparison with the sample synthesized via CP method. The results obtained are discussed on the basis of electromagnetic theory. 相似文献
995.
Cenk Ulu Mujde Guzelkaya Ibrahim Eksin 《International Journal of Approximate Reasoning》2013,54(9):1421-1433
In this study, a new centroid type reduction method is proposed for piecewise linear interval type-2 fuzzy sets based on geometrical approach. The main idea behind the proposed method relies on the assumption that the part of footprint of uncertainty (FOU) of an interval type-2 fuzzy set (IT2FS) has a constant width where the centroid is searched. This constant width assumption provides a way to calculate the centroid of an IT2FS in closed form by using derivative based optimization without any need of iterations. When the related part of FOU is originally constant width, the proposed method finds the accurate centroid of an IT2FS; otherwise, an enhancement can be performed in the algorithm in order to minimize the error between the accurate and the calculated centroids. Moreover, only analytical formulas are used in the proposed method utilizing geometry. This eliminates the need of using discretization of an IT2FS for the type reduction process which in return naturally improves the accuracy and the computation time. The proposed method is compared with Enhanced Karnik–Mendel Iterative Procedure (EKMIP) in terms of the accuracy and the computation time on seven test fuzzy sets. The results show that the proposed method provides more accurate results with shorter computation time than EKMIP. 相似文献
996.
We show how to compute the low Hochschild cohomology groups of a partial relation extension algebra. 相似文献
997.
A finite dimensional algebra A (over an algebraically closed field) is called triangular if its ordinary quiver has no oriented cycles. To each presentation (Q I) of A is attached a fundamental group π1(Q I), and A is called simply connected if π1(Q I) is trivial for every presentation of A. In this paper, we provide tools for computations with the fundamental groups, as well as criteria for simple connectedness. We find relations between the fundamental groups of A and the first Hochschild cohomology H 1 (A A). 相似文献
998.
Kira V. Khmelnytskaya Ibrahim Serroukh 《Mathematical Methods in the Applied Sciences》2013,36(14):1878-1891
A method for studying the one‐dimensional heat transfer process within an inhomogeneous spatially bounded medium in the presence of an external heat source is presented. It is based on a recently introduced technique for solving problems related to Sturm–Liouville equations that consists in the representation of solutions in the form of a spectral parameter power series. We consider a heat transfer model linked to photoacoustic and show that the introduced method, besides its relative simplicity and analytical nature, offers an efficient numerical algorithm as well as a convenient way to work separately with different physically meaningful components of the temperature distribution function. Detailed explanations and numerical examples are given. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
999.
Existence of a ground state and scattering for a nonlinear Schrödinger equation with critical growth
Takafumi Akahori Slim Ibrahim Hiroaki Kikuchi Hayato Nawa 《Selecta Mathematica, New Series》2013,19(2):545-609
We study the energy-critical focusing nonlinear Schrödinger equation with an energy-subcritical perturbation. We show the existence of a ground state in the four or higher dimensions. Moreover, we give a sufficient and necessary condition for a solution to scatter, in the spirit of Kenig and Merle (Invent Math 166:645–675, 2006). 相似文献
1000.
In this paper, we address the problem of determining the optimum antenna configuration for a multi‐input multi‐output (MIMO) system at any given signal‐to‐noise ratio (SNR). We used two‐level differential evolution (DE) algorithm that finds both an appropriate expression among a set of candidate expressions within the list of the optimization software used, and the parameter values (coefficients) belonging to the selected expression. The results of the proposed expression are compared with the results of high SNR approximation, asymptotic approach and optimum antenna number ratios. It is shown that the numerical outcomes produced by the new expression exhibit very good agreement with the optimum antenna number ratios, and this agreement is almost independent of the specific value of SNR. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献