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991.
A. Bianconi Y. Busby M. Fratini V. Palmisano L. Simonelli M. Filippi S. Sanna F. Congiu A. Saccone M. Giovannini S. De Negri 《Journal of Superconductivity and Novel Magnetism》2007,20(7-8):495-501
Here we report synthesis and characterization of high quality samples of the superconducting system Mg1−x
Al
x
B2, with a novel optimized preparation method, in a wide range of Al concentration. All the physical properties of the samples
can be tuned continuously with increasing Al content. We have characterized the samples for their structural, morphological
and magnetic properties with high resolution XRD, SEM-EDS and susceptibility measurements. We have prepared a large number
of Al doped MgB2 in the range 0<x<0.57. All the samples are bulk superconductors and the critical temperature show a smooth and regular behavior as a function
of x.
This work was supported by European project 517039 “Controlling Mesoscopic Phase Separation” (COMEPHS) (2005).
An erratum to this article can be found at 相似文献
992.
J. Okabayashi M. Watanabe H. Toyao T. Yamaguchi J. Yoshino 《Journal of Superconductivity and Novel Magnetism》2007,20(6):443-446
We have investigated the current pulse width dependence on current-driven magnetization reversal in double-barrier structures
using GaMnAs-based magnetic tunneling junctions (MTJ) in order to clarify the origin of low threshold current density for
current-driven magnetization reversal. Comparing with the case of single-barrier MTJ, the pulse-width dependence reveals that
threshold current density is reduced by double-barrier MTJ. We confirmed that the threshold current density in the order of
104 A/cm2 is estimated considering the effect of current pulse width. 相似文献
993.
A Novel Inverse-Magnetostrictive Force Sensor 总被引:1,自引:0,他引:1
The change in magnetic permeability of a material under stress (inverse magnetostriction) offers the potential for a high-performance, low-cost force sensor capable of being used in harsh real-world environments. The existing force sensor technologies are limited in their use in commercial products by either cost issues or susceptibility to electromagnetic noise. Inverse Magnetostriction has been used to measure strain in controlled environments since its discovery by Joule in 1847, but not in practical applications due to a lack of data on how magnetic material properties change with environmental conditions such as temperature. Utilizing an innovative noise-reducing self-inductance design, this paper presents the basis for an inverse-magnetostrictive compressive load sensor. A lumped-parameter model for the change in sensor inductance under load, due to both mechanical and magnetic effects, is derived. The material properties of a magnetostrictive iron alloy are empirically determined over a broad range of loads and temperatures. The model and material properties are confirmed by testing a prototype force sensor. The prototype measures compressive forces from 100 to 25 000 N over a temperature range of 20 degC to 120 deg with a typical error of +/-2% (4% max). The sensor does experience significant thermal hysteresis for which the model does not currently account. This work was motivated by the need for a force sensor in an automobile electric brake system and used a single iron alloy (50% Ni), but the model and testing procedure provide a roadmap for future research to improve the performance and capabilities of such a sensor 相似文献
994.
O. A. Neucheva A. A. Evstrapov Yu. B. Samsonenko G. E. Cirlin 《Technical Physics Letters》2007,33(11):923-925
We have studied the reflectivity spectra of doped GaAs nanowhiskers (NWs) with various morphologies, which were grown by molecular-beam epitaxy. It is established that the character of the reflectivity spectra of NWs is determined by the shape of nanocrystals. NWs with droplike and pointlike vertices differently interact with electromagnetic radiation. Laser radiation produces a spectraly selective action on the NW array, which leads to a change in the NW height and induces “caking” of their vertices, thus modifying the reflectivity of the sample. This phenomenon can be used for the creation of local microstructures with preset characteristics in large NW arrays. 相似文献
995.
We study the long-term strength of long cylindrical shells placed in aggressive media under the conditions of complex stressed
states. The influence of these states on the long-term strength of the shells is described with the help of equivalent scalar
stresses. The time to fracture of the shell is found according to the Rabotnov kinetic theory by using two parameters, namely,
the degree of damage to the material and the concentration of the medium in the material of the shell. As the boundary condition
on the fracture front, we use the condition of mass exchange. We study the interaction between the diffusion and fracture
fronts. The time to fracture of the shell is found by using the solution of a system of integrodifferential equations. Under
the assumption of mean level of concentration of the medium, we deduce explicit relationships between the times to fracture
of the shell in aggressive and neutral media.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 2, pp. 17–24, March–April, 2007. 相似文献
996.
K M Cooper L Ribeiro P Alves V Vozikis S Tsitsamis G Alfredsson T L?vgren M Tuomola H Takalo A Iitia S S Sterk M Blokland D G Kennedy 《Food Additives & Contaminants》2003,20(9):804-812
Many zeranol immunoassay test kits cross-react with toxins formed by naturally occurring Fusarium spp. fungi, leading to false-positive screening results. This paper describes the evaluation and application of recently published, dry reagent time-resolved fluoroimmunoassays (TR-FIA) for zeranol and the toxin alpha-zearalenol. A ring test of bovine urine fortified with zeranol and/or alpha-zearalenol in four European Union National Reference Laboratories demonstrated that the TR-FIA tests were accurate and robust. The alpha-zearalenol TR-FIA satisfactorily quantified alpha-zearalenol in urine fortified at 10-30 ng ml(-1). The specificity-enhanced zeranol TR-FIA accurately quantified zeranol in the range 2-5 ng ml(-1) and gave no false-positive results in blank urine, even in the presence of 30 ng ml(-1) alpha-zearalenol. Zeranol TR-FIA specificity was demonstrated further by analysing incurred zeranol-free urine samples containing natural Fusarium spp. toxins. The TR-FIA yielded no false-positive results in the presence of up to 22 ng ml(-1) toxins. The performance of four commercially available zeranol immunoassay test kits was more variable. Three kits produced many false-positive results. One kit produced only one potential false-positive using a protocol that was longer than that of the TR-FIA. These TR-FIAs will be valuable tools to develop inspection criteria to distinguish illegal zeranol abuse from contamination arising from in vivo metabolism of Fusarium spp. toxins. 相似文献
997.
998.
Reconstruction of the radiation situation in areas subjected to nuclear accidents was done with an example of the Chernobyl accident (1986) on the basis of the radionuclidic composition of soil samples. The radionuclidic composition of γ-emitters was determined 19 years after the accident in a pulverescent sandstone sample collected in July 1986 at a distance of 1.5 km from the 4th block. Using reference data and data from original papers, reconstruction of the radionuclidic composition of the sample is done on the first ten days after the accident, and possible variations of the γ-radiation dose rate were determined within the framework of the thin film model. Based on the results obtained, variations of the absorbed dose of γ-radiation in 10 days are estimated, which is necessary for making urgent decisions in the initial period after the accident. The results are well consistent with the published data on the dose rates, validating the decision on evacuation of the people from Pripyat town and from the 30-km exclusion zone. 相似文献
999.
The field evaporation of carbidized tungsten (ribbed crystals) was studied by the atom probe method at various temperatures of the sample in the regions of cryogenic, room, and elevated (1300–1600 K) temperatures. For a high pulsed (not less than 40%) component in the evaporating field, the room-temperature field evaporation mass spectra correctly reflect the surface composition of the evaporated sample. The mass spectra reveal a large number of molecular and polymerized (cluster) ions. Data from field ion desorption microscopy indicate that high-temperature field evaporation of a ribbed crystal proceeds via ion emission from walking and merging thermal-field microroughnesses. 相似文献
1000.
Jean Poerre 《钢铁》2003,38(Z1):101-103
全球变暖给钢铁工业带来了巨大的挑战,挑战涉及使用碳的多少和能量利用率.低强度生产可以短期内达到减轻排放,使处于京都协议要求的水平.从中期看,更多地使用废钢也有助于减轻排放.但是为了实现更多地减少温室气体GHG的排放,也即等于实现京都协议之后的排放目标,钢铁工业必须设想有一个新的生产面貌,这形成了未来时期对它的最大挑战.碳的收集和吸收,碳使用中的代用剂,工艺流程中绿色来源的电和氢的应用,这些在未来10年中是必须要发展的,希望通过广泛地国际合作加以实现. 相似文献