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111.
The ferromagnetic shape memory alloy with nominal composition Ni54Fe19Ga27 is investigated by Ac susceptibility and resistivity measurements. The alloy shows long-range ferromagnetic order below 290 K. The anomaly due to the martensitic transition is observed in the susceptibility and resistivity data in the temperature range around 220 K, which is associated with clear thermal hysteresis. Minor hysteresis loop technique was used to investigate the phase coexistence across the martensitic transition, and our analysis indicate that both martensite and austenite phases mutually coexist in the region of hysteresis. 相似文献
112.
Irvin Roy Hentzel Leslie Hogben 《Journal of Algorithms in Cognition, Informatics and Logic》1981,2(1):44-49
We checked the 107-dimensional alternative algebra constructed by E. Kleinfeld (On centers of alternative algebras, Comm. Algebra8(3) 1980, 289–297) and verified that it was alternative. To straightforwardly check the alternative law for the basis elements proved to be too time consuming for the computer. We developed a new algorithm which is much faster for sparse multiplication tables and which requires much less memory. Instead of testing the identities for all possible choices of basis elements, our algorithm is based on “factoring” the basis elements in all possible ways. The factorization algorithm took 5 minutes of C.P.U. time; it is estimated direct substitution with no consideration for sparseness would take 600 hours. Even when the substitution technique was improved to account for sparseness it is estimated it would take 12 hours of C.P.U. time. Substitution also requires 100 times as much memory space as factorization. 相似文献
113.
Quantum gravity is expected to remove the classical singularity that arises as the end state of gravitational collapse. To investigate this, we work with a toy model of a collapsing homogeneous scalar field. We show that nonperturbative semiclassical effects of loop quantum gravity cause a bounce and remove the black hole singularity. Furthermore, we find a critical threshold scale below which no horizon forms: quantum gravity may exclude very small astrophysical black holes. 相似文献
114.
Since the work of Ebbesen et al. [Nature (London) 391, 667 (1998)], there has been immense interest in the optical properties of subwavelength holes in metal layers. While the enhanced transmission observed is generally associated with surface plasmon polaritons (SPPs), theoretical predictions suggest a similar response with perfectly conducting materials. However, Pendry et al. [Science 305, 847 (2004)] proposed that, if textured on a subwavelength scale, even perfect conductors support surface modes. Here, using microwave radiation incident upon an array of metal waveguides, we observe peaks in the transmissivity below cutoff and confirm the crucial role of these SPP-like modes in the mechanism responsible. 相似文献
115.
M. Manekar S. B. Roy 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(1):19-25
We investigate the electronic structure of
Sr2FeMoO6/SrTiO3 (SFMO/STO) multilayers using the
ab initio Full Potential Linearized Augmented Plane Wave
method in order to study their properties within the GGA and GGA+U methods. We examin more especially the role of the interface
on the magnetic and transport properties of these multilayers taking into account a possible Fe deficiency at the interface
and we show that bulk behaviour is rapidly recovered due to the strong localization of
the interfacial perturbation. For perfect interfaces, the whole structure is found half-metallic within the GGA+U method;
the situation
being ambiguous within the GGA method where SFMO is at the limit of being half-metallic depending on the structural deformation
induced by the STO layer. This leads us to the conclusion that such a system could be used as injection electrode and tunnel
barrier in magnetic tunnel junctions with a fully spin polarized injected current.
For Fe deficient interfaces, we show that the interfacial densities of states are nearly unpolarized showing that this kind
of
imperfection has potentially a strong impact on the properties
of the multilayers. 相似文献
116.
The effect of lattice anharmonicity on the resonant modes of dilute impurities for Au-Cu, Au-Ag and W-Cr metallic systems
are studied from the poles of the double time temperature dependent impure Green’s function of these crystals. The third order
force constants used in the present work are derived assuming the systems to obey the Lennard-Jones potential. The inclusion
of lattice anharmonicity has been found to increase the resonant frequency which depends upon the mass defect, force constant
change parameter and the impurity concentration terms. Some interesting features about the phase shift and the change in width
of the vibrational spectrum are reported at room temperature for the isotopic defects and the defects interacting with host
atoms. The results are found to be in qualitative agreement with the experiments on the systems considered. 相似文献
117.
An acoustic backscattering technique for the detection of transient cavitation produced by microsecond pulses of ultrasound 总被引:1,自引:0,他引:1
R A Roy S I Madanshetty R E Apfel 《The Journal of the Acoustical Society of America》1990,87(6):2451-2458
An acoustic backscattering technique for detecting transient cavitation produced by 10-microseconds-long pulses of 757-kHz ultrasound is described. The system employs 10-microseconds-long, 30-MHz center frequency tone bursts that scatter from cavitation microbubbles. Experiments were performed with suspensions of hydrophobic polystyrene spheres in ultraclean water. Transient cavitation threshold pressures measured with the active cavitation detector (ACD) were always less than or equal to those measured using a passive acoustic detection scheme. The measured cavitation thresholds decreased with increasing dissolved gas content and increasing suspended particle concentration. Results also show that ultrasonic irradiation of the polystyrene sphere suspensions by the ACD lowered the threshold pressure measured with the passive detector. A possible mechanism through which suspensions of hydrophobic particles might nucleate bubbles is presented. 相似文献
118.
Atiya MS Chiang I Frank JS Haggerty JS Ito MM Kycia TF Li KK Littenberg LS Stevens A Strand RC Louis WC Akerib DS Marlow DR Meyers PD Selen MA Shoemaker FC Smith AJ Azuelos G Blackmore EW Bryman DA Felawka L Kitching P Kuno Y Macdonald JA Numao T Padley P Poutissou J Poutissou R Roy J 《Physical review letters》1990,65(1):21-24
119.
120.
Epitaxial-Bain-Path and Uniaxial-Bain-Path studies reveal that a B2-CuZr nanowire with Zr atoms on the surface is energetically more stable compared to a B2-CuZr nanowire with Cu atoms on the surface. Nanowires of cross-sectional dimensions in the range of ~20–50 Å are considered. Such stability is also correlated with the initial state of stress in the nanowires. It is also demonstrated here that a more stable structure, i.e., B2-CuZr nanowire with Zr atoms at surface shows improved yield strength compared to B2-CuZr nanowire with Cu atoms at surface site, over range of temperature under both the tensile and the compressive loadings. Nearly 18% increase in the average yield strength under tensile loading and nearly 26% increase in the averaged yield strength under compressive loading are observed for nanowires with various cross-sectional dimensions and temperatures. It is also observed that the B2-CuZr nanowire with Cu atom at the surface site shows a decrease in failure/plastic strain with an increase in temperature. On the other hand, B2-CuZr nanowires with Zr at the surface site shows an improvement in failure/plastic strain, specially at higher temperature as compared to the B2-CuZr nanowires which are having Cu atoms at the surface site. Finally, a possible design methodology for an energetically stable nano-structure with improved thermo-mechanical properties via manipulating the surface atom configuration is proposed. 相似文献