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971.
The effect of a gas dissolved in a liquid on the variation of the refractive index of the compressed mixture was studied.
The compression process was monitored with the aid of a holographic interferometer. The sensitivity of this method allows
the compressibility of water and the solubility of helium and nitrogen to be studied at pressures below 4 atm. A procedure
for obtaining qualitative and quantitative data on the solubility of gases in liquids is proposed. 相似文献
972.
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
973.
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
974.
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
975.
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
976.
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
977.
The ideal uniform two-dimensional (2D) Fermi and Bose gases are considered both in the thermodynamic limit and the finite case. We derive May's Theorem, viz. the correspondence between the internal energies of the Fermi and Bose gases in the thermodynamic limit. This results in both gases having the same heat capacity. However, as we shall show, the thermodynamic limit is never truly reached in two dimensions and so it is essential to consider finite-size effects. We show in an elementary manner that for the finite 2D Bose gas, a pseudo-Bose–Einstein condensate forms at low temperatures, incompatible with May's Theorem. The two gases now have different heat capacities, dependent on the system size and tending to the same expression in the thermodynamic limit. 相似文献
978.
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
979.
The methods of X-ray photoelectron spectroscopy and Auger spectroscopy are used to study surface films formed on zinc and zinc-plated steel in the process of holding in aqueous extracts of mixtures of phosphate and calcium-containing pigments. It is shown that protective films formed mainly of zinc and calcium phosphates of different chemical structure are deposited in inhibited solutions on specimens of pure zinc and zinc-plated steel. The protective properties of these films are much better than the protective properties of the surface layers formed on the metal in the extracts of a single phosphate (or calcium-containing) pigment. The mixture of these pigments may serve as a promising substitution of chromate inhibitors in anticorrosive organic coatings. 相似文献
980.
A. Pizzinat B.S. Marks L. Palmieri C.R. Menyuk A. Galtarossa 《Photonics Technology Letters, IEEE》2003,15(6):819-821
We consider the two Wai-Menyuk models of birefringence in periodically spun fibers, and we show that the differential group delay differs significantly for the two models when the spin period approaches or exceeds the fiber beat length. When the fiber correlation length is large, we explain this difference quantitatively, and we explain it qualitatively for any fiber correlation length. 相似文献