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991.
V. A. Kagadei E. V. Nefyodtsev D. I. Proskurovsky S. V. Romanenko 《Technical Physics Letters》2003,29(11):897-900
Using one-or two-layer films of transition metals, it is possible to determine the atomic hydrogen flux density under reduced
gas pressure conditions (10−1–10−3 Pa). The method consists in monitoring a change in the film resistance caused by selective dissolution of atomic hydrogen
in the metal during exposure of the film in a mixed atomic-molecular flow, followed by determining a characteristic time τ
required for the hydrogen concentration in the film to reach 63% of the maximum possible level. The hydrogen flux density
is then calculated within the framework of a simple mathematical model of the film saturation with hydrogen described by a
relaxation law. The proposed method is characterized by a high selective sensitivity to atomic hydrogen. The atomic hydrogen
flux density in a mixed atomic-molecular flow can be determined in a range from 5×1013 to 1016 cm−2 s−1. 相似文献
992.
X. X. Xi X. H. Zeng A. V. Pogrebnyakov A. Soukiassian S. Y. Xu Y. F. Hu E. Wertz Q. Li Y. Zhong C. O. Brubaker Z.-K. Liu E. M. Lysczek J. M. Redwing J. Lettieri D. G. Schlom W. Tian H. P. Sun X. Q. Pan 《Journal of Superconductivity and Novel Magnetism》2003,16(5):801-806
The recently discovered superconductor MgB2 with T c at 39 K has great potential in superconducting electronics. In this paper, we review the deposition techniques used for MgB2 thin films in the light of a thermodynamic study of the Mg-B system with the calculation of phase diagrams (CALPHAD) modeling technique. This thermodynamic study identifies a growth window in the pressure–temperature phase diagram, in which the magnesium pressure is very high for likely in situ growth temperatures. A Hybrid Physical–Chemical Vapor Deposition (HPCVD) technique that successfully achieves such a high Mg pressure is shown to produce in situ epitaxial MgB2 thin films with bulk superconducting properties. 相似文献
993.
Shuman Daniel W.; Cunningham Mark D.; Connell Mary A.; Reid William H. 《Canadian Metallurgical Quarterly》2003,34(3):233
Forensic psychology has made important gains in professional recognition and stature in the courts, resulting in increasing demands for mobility of expertise. Current regulations regarding the interjurisdictional temporary forensic practice of psychology, however, are characterized by variability of regulations, ambiguity and inaccessibility, and continuing total barriers. A uniform, well-reasoned policy is needed. A conceptual basis for such a policy is provided by a discussion of licensing rationales and the application of these to forensic practice. Uniformity, public and professional protection, and practicability are identified as fundamental regulatory criteria. A Model Rule Regarding the Temporary Forensic Practice of Psychology is proposed for adoption by state licensing boards on a nationwide basis. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Koenen Karestan C.; Stellman Jeanne Mager; Stellman Steven D.; Sommer John F. Jr. 《Canadian Metallurgical Quarterly》2003,71(6):980
Risk factors affecting the course of posttraumatic stress disorder (PTSD) are poorly understood. As part of a larger study on characterizing exposure to herbicides in Vietnam, the authors investigated this issue in a random sample of 1,377 American Legionnaires who had served in Southeast Asia during the Vietnam War and were followed over a 14-year period. High combat exposure, perceived negative community attitudes at homecoming, minority race, depression symptoms at Time 1, and more anger at Time 1 predicted a more chronic course. Community involvement at Time 1 was protective and associated with decreased risk at Time 2. Discomfort in disclosing Vietnam experiences was associated with an increased risk for developing PTSD but did not predict its course. Combat exposure predicted PTSD course more strongly than any other risk factor. Findings suggest recovery from PTSD is significantly influenced by perceived social support. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
Nickel-rich β-NiAl alloys, which are potential materials for high-temperature shape-memory alloys, show a thermoelastic martensitic transformation,
which produces their shape memory effect. However, the transformation to Ni5Al3 phase during heating of NiAl martensite can interrupt the reversible martensitic transformation; consequently, the shape
memory effect in NiAl martensite might not appear after heating. The phase transformation process in binary Ni-(34 to 37)Al
martensite was investigated by differential thermal analysis (DTA) method, and we found that the condition of reversible martensitic
transformation was not the β → Ni5Al3 transformation, but rather the M → Ni5Al3 transformation occurring at 250 °C to 300 °C. Therefore, the transformation temperature of M → Ni5Al3 determined the highest operating temperature for the shape memory effect. For verifying the critical temperature, the phase
transformation process was investigated for eight ternary Ni-33Al-X alloys (X=Cu, Co, Fe, Mn, Cr, Ti, Si, and Nb). Only Ti,
Si, and Nb additions were found to be effective in dropping the M
s temperature, and they facilitated the shape memory effect in Ni-33Al-X alloys. In particular, the addition of Si and Nb raised
the transformation temperature of M → Ni5Al3, a potentially beneficial effect for shape memory at higher temperatures.
This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented
at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint
Committee on Mechanical Behavior of Materials. 相似文献
996.
Richard F. D.; Bond Charles F. Jr.; Stokes-Zoota Juli J. 《Canadian Metallurgical Quarterly》2003,7(4):331
This article compiles results from a century of social psychological research, more than 25,000 studies of 8 million people. A large number of social psychological conclusions are listed alongside meta-analytic information about the magnitude and variability of the corresponding effects. References to 322 meta-analyses of social psychological phenomena are presented, as well as statistical effect-size summaries. Analyses reveal that social psychological effects typically yield a value of r equal to .21 and that, in the typical research literature, effects vary from study to study in ways that produce a standard deviation in r of .15. Uses, limitations, and implications of this large-scale compilation are noted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
997.
This paper tests the assertion that experienced contractors are more competitive than inexperienced contractors by measuring the effect of experience on bidding competitiveness for building contracts procured by a regular client. Contractors are grouped into experienced and inexperienced contractors, and two levels of contractors’ experience are identified: (1) bidding experience only and (2) bidding plus construction experience. Results of two-sample t tests show that experienced contractors are more competitive than inexperienced contractors. Contractors’ competitiveness in respect of school contracts and other contracts are further compared in evaluating the relationship between the project type and experience effect. Experienced contractors are, on average, more competitive in competing for school contracts. It emerges that the factor of project type familiarity amplifies the experience effect. A comparison of experienced contractors’ competitiveness in bidding for (1) new building works and (2) alteration and extension works shows that the effect of experience would be more significant when contract works packages are highly standardized. 相似文献
998.
D. V. V. Satyanarayana G. Malakondaiah D. S. Sarma 《Metallurgical and Materials Transactions A》2003,34(11):2579-2590
The effect of prior oxidation at 1473 K on the creep behavior of an Fe-Ni-Cr-Al alloy, hardened by ordered NiAl precipitates,
has been investigated at 873 K over a stress range of 275 to 450 MPa. The alloy in the as-electroslag remelted (ESR) as well
as the ESR-plus-hot-worked conditions was considered. Prior oxidation causes creep strengthening in the Fe-Ni-Cr-Al alloy,
resulting in a decrease in minimum creep rate and increase in time to rupture, in contrast to the observations reported on
nickel-based superalloys. Creep strengthening is, however, accompanied by a significant reduction in creep ductility. Oxidation-induced
creep strengthening in the current alloy can be attributed to the improved adherence of surface oxide caused by the presence
of yttrium. An effective stress that incorporates the contributions of load transfer as well as substructural strengthening
is used to account for the observed oxidation-induced creep strengthening. While creep strengthening is more pronounced in
the ESR cast alloy, the loss in creep ductility is more intense in the ESR wrought alloy. Increasing the oxidation time beyond
1 hour has a minimal effect on creep strengthening of both the alloys, though it lowers significantly the creep ductility
of the wrought alloy. The observed differences in creep behavior of the alloy in the two different conditions could be attributed
to the differences in grain size as well as morphology and related oxidation-induced damage. 相似文献
999.
K. Lefmann B. Lake G. Aeppli S.-W. Cheong N. B. Christensen K. N. Clausen S. Hayden T. E. Mason D.F. McMorrow H. A. Mook H. M. Rønnow H. Takagi 《Journal of Low Temperature Physics》2004,135(5-6):621-664
One important area of modern condensed matter research is the investigation of the nature of the superconducting cuprates. Much progress in this field has been obtained with the technique of neutron scattering. We here present a review of neutron scattering studies of the high-temperature superconductor La2?xSrxCuO4, performed at Risø National Laboratory. We review the work on the mapping of the incommensurate spin fluctuations, the investigation of the gap in the fluctuation spectrum, the magnetic properties of the vortices appearing in an applied field, and the quantum critical behaviour of the system. We discuss our findings in the light of results of neutron scattering from other groups, on other cuprate systems, and results from other experimental methods, e.g. NMR, μSR, STM, X-ray diffraction, and ARPES. We end with a discussion on the implications of the experimental results for the progress in the general understanding of high-temperature superconductivity. PACS numbers: 61.12.Ex, 74.20.Mn, 74.72.Dn, 75.25.+z, 78.70.Nx. 相似文献
1000.
Today, with the increasing popularity of multicore processors, one approach to optimizing the processor's performance is to reduce the execution times of individual applications running on each core by designing and implementing more powerful cores. Another approach, which is the polar opposite of the first, optimizes the processor's performance by running a larger number of applications on a correspondingly larger number of cores, albeit simpler ones. The difference between these two approaches is that the former focuses on reducing the latency of individual applications or threads (it optimizes the processor's single-threaded performance), whereas the latter focuses on reducing the latency of the applications' threads taken as a group (it optimizes the processor's multithreaded performance). The panel, from the 2007 Workshop on Computer Architecture Research Directions, discusses the relevant issues. 相似文献