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排序方式: 共有263条查询结果,搜索用时 15 毫秒
61.
Gray microcrystalline powders of ScTaN(2) were prepared from solid-state reactions of delta-ScN with Ta(3)N(5) powders at T = 1770 K. According to thermal analyses the compound is stable against oxidation by O(2) up to temperatures of T = 800 K. In an Ar atmosphere ScTaN(2) decomposes above T = 1250 K and in a N(2) atmosphere above T = 2000 K under release of N(2) to form delta-ScN and beta-Ta(2)N. The crystal structure (space group P6(3)/mmc, No. 194, a = 305.34(3) pm, c = 1056.85(9) pm, Z = 2) was refined on the basis of X-ray and neutron powder diffraction data. It comprises alternating layers of ScN(6/3) octahedra and trigonal TaN(6/3) prisms, which are also observed in the binary nitrides delta-ScN and theta-TaN, respectively. A small degree of anti-site defects (about 5%) was detected. Only a small solubility of ScN in epsilon-TaN was observed, while the solubility of TaN in delta-ScN is >/=10 mol % at T = 1820 K. ScTaN(2) is a diamagnetic small gap semiconductor or a semimetal, as inferred from magnetization and electrical resistivity measurements, consistent with band structure calculations. Chemical bonding analyses with the COHP method yield significant covalent Ta-Ta interactions. Topological analyses of the electron localization function reveal unexpected Ta-Ta three-center bonding basins within seemingly empty trigonal prisms of the TaN(6/3) layers. 相似文献
62.
A rapid and facile synthesis of N-substituted 2,3,3a,4,7,7a-hexahydroisoindole-l,3-dione derivatives via microwave-promoted Beller three-component domino reaction of α,β,-unsaturated aldehydes, amides and N-substituted maleimides was described. 相似文献
63.
This paper is a continuation of the authors recent work [Beir?o da Veiga, H.and Yang, J., On mixed pressure-velocity regularity criteria to the Navier-Stokes equations in Lorentz spaces, Chin. Ann. Math., 42(1), 2021, 1–16], in which mixed pressure-velocity criteria in Lorentz spaces for Leray-Hopf weak solutions of the three-dimensional NavierStokes equations, in the whole space R~3 and in the periodic torus T~3, are established. The purpose of the present work is to extend the result of mentio... 相似文献
64.
A polynomial expansion is proposed as a new way to discretize the Griffin-Wheeler-Hartree-Fock equations of the Generator Coordinate Hartree-Fock method. The implementation of the polynomial expansion in the Generator Coordinate Hartree-Fock method discretizes the Griffin-Wheeler-Hartree-Fock equations through a numerical mesh which is not equally spaced. This procedure makes the optimization of Gaussian exponents in the Generator Coordinate Hartree-Fock method more flexible and more efficient. The results obtained with the polynomial expansion for atomic Hartree-Fock energies show this technique is very powerful when employed in the design of compact and high accurate Gaussian basis sets used in ab initio non-relativistic (Hartree-Fock) and relativistic (Dirac-Fock) calculations. 相似文献
65.
V. A. Zherebtsov 《Technical Physics》2006,51(7):834-840
The structure of the near-electrode regions of a thermoelectronic laser energy converter filled with a two-component gas mixture (noble gas + easily ionized additive) is investigated under conditions such that the main gas near the electrodes is weakly ionized. Specific features of the distributions of the densities of the main-gas ions and the ions and atoms of the additive, the temperature of the heavy plasma components, and the electric potential near the electrodes are examined at different total densities of the atoms and ions of the additive. The boundary conditions are determined at the near-electrode boundaries of the equilibrium core of a continuous optical discharge in a thermoelectronic laser energy converter filled with a two-component gas mixture. 相似文献
66.
COMPONENT ALLEE EFFECTS AND STAGE‐SPECIFIC PREDATION: A BRIEF INSIGHT INTO CONSERVATION AND BIOLOGICAL CONTROL ISSUES
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In this paper, we propose a two‐stage structured population model subject to component Allee effects in fecundity and maturation, and with two disturbances (predation only and harvest and predation) acting on both stages. It is shown that this combination leads to a demographic Allee effect—a characteristic that could be exploited in pest biological control, but on the other hand, it represents a bane in conservation biology. The analysis is performed for disturbances with functional responses type 2 and 3, and the models show that they yield qualitatively similar results. This characteristic is discussed from the species conservation and biological control point of view, together with possible extensions of this work. 相似文献
67.
A. P. Serebrov O. Zimmer P. Geltenbort A. K. Fomin S. N. Ivanov E. A. Kolomensky I. A. Krasnoshekova M. S. Lasakov V. M. Lobashev A. N. Pirozhkov V. E. Varlamov A. V. Vasiliev O. M. Zherebtsov E. B. Aleksandrov S. P. Dmitriev N. A. Dovator 《JETP Letters》2010,91(1):6-10
The search for CP violating forces between nucleons in the so-called axion window of force ranges λ between 2 × 10?5 m and 0.02 m is interesting because only little experimental information is available there. Axionlike particles would induce a pseudo-magnetic field for neutrons close to bulk matter. A laboratory search investigates neutron spin precession close to a heavy mirror using ultracold neutrons in a magnetic resonance spectrometer. From the absence of a shift of the magnetic resonance we established new constraints on the coupling strength of axion-like particles in terms of the product g s g p of scalar and pseudo-scalar dimensionless constants, as a function of the force range λ, g s g p λ2 ≤ 2 × 10?21 [cm2] (C.L.95%) for 10?4 cm < λ < 1 cm. For 0.1 cm < λ < 1 cm previous limits are improved by 4 to 5 orders of magnitude. 相似文献
68.
69.
S. A. Syutkin V. Yu. Pervushin G. F. Kuznetsov D. G. Kleshchev D. A. Zherebtsov V. A. German V. V. Viktorov A. M. Kolmogorov A. S. Serikov 《Russian Journal of Applied Chemistry》2010,83(7):1209-1214
X-ray diffraction analysis, transmission electron microscopy, IR spectroscopy, mass spectrometry, chemical analysis, and thermogravimetry
were used to study transformations in the course of a hydrothermal treatment (150–240°C of samples of hydrated titanium dioxide
produced by thermal hydrolysis of sulfuric acid solutions of titanium(IV) compounds), in water. The dependences of the dispersion
and chemical composition of the samples obtained on the thermal treatment temperature were determined. 相似文献
70.