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71.
Jiong Zhou Hongliang Ma Minjian Zhong Guoqing Xu Zhongyue Yue Zhengming He 《Journal of magnetism and magnetic materials》2006
Polycrystalline BaCoxZrxFe11.5−2xO18.25 samples with 0?x?0.6 ions per formula units were prepared by modified citrate precursor method with the initial ratio of Ba:Fe equal to 1:11.5. The cationic site preferences of Co2+ and Zr4+ in Co–Zr substituted Ba ferrite were investigated by magnetic measurements and X-ray diffractometer (XRD) analysis. The coercivity Hc was decreasing with increasing Co–Zr substitution. The datum showed that the max coercive force (Hc) was obtained when substitution of 0.2, while the best saturation magnetizations (Ms) was obtained when substitution of 0.4. 相似文献
72.
W. Wang K.Y. Li J. Wang W. Han F. Wang Y. Xiang F.Q. Li H.T. Jia L.Q. Wang W. Zhong X.M. Zhang S.Z. Zhao B. Feng 《Optics & Laser Technology》2011,43(3):683-686
The dependence of the phase matching (PM) angle on temperature in type-I second harmonic generation (SHG) and type-II third harmonic generation (THG) of KDP is experimentally investigated. The experimental results show that as the crystal temperatures vary by 1 °C, the external PM angles of the KDP doubler and tripler change 100 μrad and 220 μrad, respectively. The PM angle of KDP tripler is more sensitive to temperature variation than is that of the KDP doubler. Comparing the numerical calculations and the previous reports, a discrepancy has been found among the different reported results. Based on the analytical solution of the temperature dependence of the SHG process it is shown that a small error in the thermo-optic coefficients of the crystal is the main factor source of the discrepancy. 相似文献
73.
Riguang ZhangHongyan Liu Huayan ZhengLixia Ling Zhong LiBaojun Wang 《Applied Surface Science》2011,257(11):4787-4794
The adsorption and dissociation of O2 on the perfect and oxygen-deficient Cu2O(1 1 1) surface have been systematically studied using periodic density functional calculations. Different kinds of possible modes of atomic O and molecular O2 adsorbed on the Cu2O(1 1 1) surface are identified: atomic O is found to prefer threefold 3Cu site on the perfect surface and Ovacancy site on the deficient surface, respectively. CuCUS is the most advantageous site with molecularly adsorbed O2 lying flatly over singly coordinate CuCUS-CuCSA bridge on the perfect surface. O2 adsorbed dissociatively on the deficient surface, which is the main dissociation pathway of O2, and a small quantity of molecularly adsorbed O2 has been obtained. Further, possible dissociation pathways of molecularly adsorbed O2 on the Cu2O(1 1 1) surface are explored, the reaction energies and relevant barriers show that a small quantity of molecularly adsorbed O2 dissociation into two O atoms on the deficient surface is favorable both thermodynamically and kinetically in comparison with the dissociation of O2 on the perfect surface. The calculated results suggest that the presence of oxygen vacancy exhibits a strong chemical reactivity towards the dissociation of O2 and can obviously improve the catalytic activity of Cu2O, which is in agreement with the experimental observation. 相似文献
74.
With the application of the topological upgrade, more and more experts are interested in the problems concerning the mathematical
structure’s upgrade to its power set. This paper is a further study on the structure and interrelationship of a power group.
By revealing the nature of relationship between the power group and a regular one, the present paper proves some theorems
of the structure of the power group and constructs some theorems on its homomorphism and isomorphism as well, proposing an
expression form and isomorphism replacement construct methods of the power group. 相似文献
75.
We investigate the relationship between the Gröbner-Shirshov bases in free associative algebras, free left modules and “double-free” left modules (that is, free modules over a free algebra). We first give Chibrikov’s Composition-Diamond lemma for modules and then we show that Kang-Lee’s Composition-Diamond lemma follows from it. We give the Gröbner-Shirshov bases for the following modules: the highest weight module over a Lie algebra sl 2, the Verma module over a Kac-Moody algebra, the Verma module over the Lie algebra of coefficients of a free conformal algebra, and a universal enveloping module for a Sabinin algebra. As applications, we also obtain linear bases for the above modules. 相似文献
76.
Tongde Zhong 《中国科学A辑(英文版)》1997,40(8):817-824
The homotopy formulas of (r, s) differential forms and the solution of $\bar \partial $ -equation of type (r, s) on localq-convex domains in Stein manifolds are obtained. The homotopy formulas on localq-convex domains have important applications in uniform estimates of $\bar \partial $ -equation and holomorphic extension of CR-manifolds. 相似文献
77.
We propose a new and simple estimating equation for the parameters in median regression models with designed censoring variables, and then apply the empirical log likelihood ratio statistic to construct confidence region for the parameters. The empirical log likelihood ratio statistic is shown to have a standard chi-square distribution, which makes this method easy to implement. At the same time, another empirical log likelihood ratio statistic is proposed based on an existing estimating equation and the limiting distribution of the empirical likelihood ratio statistic is shown to be a sum of weighted chi-square distributions. We compare the performance of the empirical likelihood confidence region based on the new estimating equation, with that based on the existing estimating equation and a normal approximation method by simulation studies. 相似文献
78.
79.
Dr. Rong-Lin Zhong Dr. Feng-Wei Gao Dr. Hong-Liang Xu Prof. Zhong-Min Su 《Chemphyschem》2019,20(14):1879-1884
The nature of the 2e/12c bond and its conversion to a carbon-carbon single bond in phenalenyl dimers have prompted a great deal of interests recently. In this work, we theoretically investigated a series of π-stacking phenalenyl derivatives with 2e/12c bonding character by density functional theory (DFT) calculations to elucidate origin of this unusual bond conversion. Results show that bond-conversion of the phenalenyl dimer easily occurs at room-temperature both dynamically and thermodynamically. However, bond-conversion of hetero π-stacking adducts, in which the two center carbon atoms were substituted by boron and nitrogen atoms, respectively, is much more difficult, because the 2e/12c bond is stabilized by its charge transfer character. Consequently, the bond-conversion is an endothermic process, albeit with a low conversion barrier. Interestingly, Lewis acid-base interactions would be induced by substitution of the center nitrogen atom to phosphorus atom. The 2e/12c bond is further stabilized by 5.9 kcal mol−1 and its conversion is also thermodynamically unfavorable. 相似文献
80.
High-order curvilinear mesh generation technique based on an improved radius basic function approach
A high-order curvilinear hybrid mesh generation technique is developed for high-order numerical method (eg, discontinuous Galerkin method) applications to improve the accuracy for problems with curve boundary. The grid generation technique is based on an improved radius basic function (RBF) approach by which the straight-edge mesh is converted into high-order curve mesh. Firstly, an initial straight-edge mesh is prepared by traditional grid generation software. Then, high-order interpolation points are inserted into the mesh entities such as edges, faces, and cells according to the final demand of mesh order. To preserve the original geometry, the inserted points on solid wall are then projected onto the CAD model using an open source tool “Open Cascade.” Finally, other inserted points in the field near the solid wall are moved to appropriate positions by the improved RBF approach to avoid tangled cells. If we use the original RBF approach, then the inserted points on the edge and face entities normal to the solid boundary in the region of boundary layer will move to improper positions. To overcome this problem, a weighting based on the local grid aspect ratio between normal direction and tangential direction is introduced into the baseline RBF approach. Three typical configurations are tested to validate the mesh generator. Meanwhile, a third-order solution of subsonic flow over an analytical 3D body of revolution in the second International Workshop on High-Order CFD Methods is supplied by a discontinuous Galerkin solver. These numerical tests demonstrate the potential capability of present technique for high-order simulations of complex geometries. 相似文献