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1.
Structure and magnetic properties of the Zr1−xMnxCo2+δ alloys were studied for 0 x <0.7, δ=0, 0.45. The cubic C15 Laves phase structure shows Mn solubility up to x≈0.4. The other Laves phase with the hexagonal C36 structure found for x0.5 apparently has a small region of Mn solubility in the vicinity of Zr0.4Mn0.6Co2. Though the parent Mn-free compounds are known to be paramagnetic, the Mn-substituted alloys show ferromagnetic behavior with the Curie temperatures up to 625 K and the room-temperature saturation magnetization of about 100 emu/g. The onset of ferromagnetism with the Mn substitution for Zr may be caused by polarization of itinerant 3d electrons, like it was earlier supposed for the off-stoichiometric ZrCo2+δ. The universal composition dependencies of the intrinsic magnetic properties for different δ can be obtained, if plotted against the amount of zirconium atoms missing in its sublattice. The room-temperature anisotropy with the noticeable anisotropy field of 24 kOe and the 1 1 0 easy magnetization direction laying in a basal plane was found in the hexagonal Zr0.5Mn0.5Co2. 相似文献
2.
A. Biedunkiewicz N. Gordon J. Straszko S. Tamir 《Journal of Thermal Analysis and Calorimetry》2007,88(3):717-722
Results of research work on oxidation of TiC/C nano-composites in air and under non-isothermal conditions are presented.
The oxidation of nano-crystalline titanium carbide as well as its carbon composites were studied using TG-DSC method in dry
air atmosphere. The investigated samples were as follows: commercial TiC nano-powders from Alfa Aesar (80 nm) and carbon composites
including nano-crystalline TiC (30 nm and 50, 10, 3 mass% of carbon in matrix). The measurements were executed in the Setaram
thermoanalyser TG-DSC 92-15 in non-isothermal conditions, with mass samples of 30±0.2 mg and constant heating rate in the
range 2–10 K min−1. 相似文献
3.
4.
Arie Tamir 《Mathematical Programming》1993,62(1-3):475-496
In the classicalp-center location model on a network there is a set of customers, and the primary objective is to selectp service centers that will minimize the maximum distance of a customer to a closest center. Suppose that thep centers receive their supplies from an existing central depot on the network, e.g. a warehouse. Thus, a secondary objective is to locate the centers that optimize the primary objective as close as possible to the central depot. We consider tree networks and twop-center models. We show that the set of optimal solutions to the primary objective has a semilattice structure with respect to some natural ordering. Using this property we prove that there is ap-center solution to the primary objective that simultaneously minimizes every secondary objective function which is monotone nondecreasing in the distances of thep centers from the existing central depot.Restricting the location models to a rooted path network (real line) we prove that the above results hold for the respective classicalp-median problems as well. 相似文献
5.
The lateral shift of both the reflected and the transmitted beams are examined for incidence on layered configurations. In particular, beam displacements are evaluated at a layer placed between two different semi-infinite media. We find that the reflected beam may undergo a large displacement, which occurs in either a forward or a backward direction. The transmitted beam is also substantially displaced, but its shift occurs in a forward direction only. 相似文献
6.
7.
T. Tamir 《Applied Physics A: Materials Science & Processing》1981,25(3):201-210
Guided-wave methods used in the past to treat electromagnetic problems and applications in the microwave area have recently
been extended to cover work in fiber and integrated optics. The basic principles of these methods are reviewed briefly and,
in particular, the “open” properties of optical configurations are contrasted to the “closed” characteristics that describe
most microwave applications. These aspects are illustrated in the context of beam couplers of uniform and periodic varieties,
which are shown to lend themselves to rigorous treatment by microwave guided-wave methods that include both theoretical and
experimental facets. 相似文献
8.
At room temperature and below, the proton NMR spectrum of N-(trideuteriomethyl)-2-cyanoaziridine consists of two superimposed ABC patterns assignable to two N-invertomers; a single time-averaged ABC pattern is observed at 158.9°C. The static parameters extracted from the spectra in the temperature range from –40.3 to 23.2°C and from the high-temperature spectrum permit the calculation of the thermodynamic quantities ΔH0 = ?475±20 cal mol?1 (?1.987 ± 0.084 kJ mol?1) and ΔS0 = 0.43±0.08 cal mol?1 K?1 (1.80±0.33 J mol?1 K?1) for the cis ? trans equilibrium. Bandshape analysis of the spectra broadened by non-mutual three-spin exchange in the temperature range from 39.4–137.8°C yields the activation parameters ΔHtc≠ = 17.52±0.18 kcal mol?1 (73.30±0.75 kJ mol?1), ΔStc≠ = ?2.08±0.50 cal mol?1 K?1 (?8.70±2.09 J mol?1 K?1) and ΔGtc≠ (300 K) = 18.14±0.03 kcal mol?1 (75.90±0.13 kJ mol?1) for the trans → cis isomerization. An attempt is made to rationalize the observed entropy data in terms of the principles of statistical thermodynamics. 相似文献
9.
M. Boazi J. Gabay S. Devir C. Shenberg 《Journal of Radioanalytical and Nuclear Chemistry》1978,45(2):395-406
Aerosol samples from urban, industrial and traffic areas were collected and analyzed for various elements. The correlation
between the multielement content of the samples and their sources was studied. It was found necessary to anlayze samples before
and after ashing because, while ashing improves the peak-to-background ratio, volatile elements may be lost. Samples collected
at heights of 1.5 and 15 m were found to have the same elemental composition. Samples collected on consecutive filters showed
sharp elemental fractionation An example of source identification is given for a high traffic area as compared with an area
in which a large bromine plant is located. In both cases different Pb∶Br ratios were observed, with high bromine concentration
in the latter. The analytical method used was based on the detection of characteristic K and L X-rays induced by a241Am-I source-target assembly. 相似文献
10.
Costa et al. (Oper. Res. Lett. 31:21–27, 2003) presented a quadratic O(min (Kn,n
2)) greedy algorithm to solve the integer multicut and multiflow problems in a rooted tree. (n is the number of nodes of the tree, and K is the number of commodities). Their algorithm is a special case of the greedy type algorithm of Kolen (Location problems
on trees and in the rectilinear plane. Ph.D. dissertation, 1982) to solve weighted covering and packing problems defined by general totally balanced (greedy) matrices. In this communication
we improve the complexity bound in Costa et al. (Oper. Res. Lett. 31:21–27, 2003) and show that in the case of the integer multicut and multiflow problems in a rooted tree the greedy algorithm of Kolen
can be implemented in subquadratic O(K+n+min (K,n)log n) time. The improvement is obtained by identifying additional properties of this model which lead to a subquadratic transformation
to greedy form and using more sophisticated data structures.
相似文献