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Nicholas Biery Marc De Graef Jack Beuth Rafel Raban Andrew Elliott Tresa M. Pollock Curt Austin 《Metallurgical and Materials Transactions A》2002,33(10):3127-3136
Tensile experiments have been performed on specimens of four different investment-cast TiAl-based alloys with variations in
casting conditions. The average ductilities obtained in these experiments vary between approximately 0.8 to 2.0 pct plastic
strain to failure in tension. By using the three-parameter form of the Weibull relation, with the 0.2 pct offset yield strength
as the minimum failure strength, the resulting variability in the data can be quantified and is found to be similar for those
alloys with similar microstructural scale (grain size). Large variations in lamellar volume fraction, segregation, and phase
distribution have a minor influence on property variability, compared to changes in the scale of the grain structure caused
by either variations in cooling rate during casting or the addition of grain refiners. 相似文献
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裂缝性油气藏采收率:100个裂缝性油气田实例的经验总结 总被引:5,自引:2,他引:3
通过对世界上100个裂缝性油气藏的综合评价,研究储集层及流体本身的性质(包括孔隙度、渗透率、黏度、可动油比例、含水饱和度、润湿性及裂缝分布特征等)和驱动机制及油藏管理战略(优化日产量和采用不同类型的提高采收率技术)对其最终采收率的影响。将裂缝性油气藏分为4类:I类的基质几乎没有孔隙度和渗透率,裂缝是储存空间和流体流动的通道;Ⅱ类的基质有较低的孔隙度和渗透率,基质提供储存空间,裂缝提供流动通道;Ⅲ类(微孔隙)的基质具有高孔隙度和低渗透率,基质提供储存空间,裂缝提供流动通道;Ⅳ类(大孔隙)的基质具有高的孔隙度和渗透率,基质提供储存空间和流动通道,裂缝仅增加渗透率。对26个Ⅱ类油气藏和20个Ⅲ类油气藏的开采历史的研究表明:Ⅱ类油气藏的采收率受水驱强度和最优日产量控制,日产量过高会很容易破坏Ⅱ类油气藏,一些Ⅱ类油气藏如果管理得当,采收率可以很高,不需要二次或三次采油;Ⅲ类油气藏的采收率主要受岩石和流体本身性质的影响,特别是基质渗透率、流体重度、润湿性以及裂缝强度等,不进行二次或三次采油不可能完全开采,往往需要采用一些提高采收率的专门技术。以往将Ⅱ类和Ⅲ类裂缝性油气藏归为一类,认识它们的区别将有助于选择更好的开发策略。 相似文献
5.
Jost John T.; Glaser Jack; Kruglanski Arie W.; Sulloway Frank J. 《Canadian Metallurgical Quarterly》2003,129(3):383
A meta-analysis by J. T. Jost, J. Glaser, A. W. Kruglanski, and F. J. Sulloway (2003) concluded that political conservatism is partially motivated by the management of uncertainty and threat. In this reply to J. Greenberg and E. Jonas (2003), conceptual issues are clarified, numerous political anomalies are explained, and alleged counterexamples are incorporated with a dynamic model that takes into account differences between "young" and "old" movements. Studies directly pitting the rigidity-of-the-right hypothesis against the ideological extremity hypothesis demonstrate strong support for the former. Medium to large effect sizes describe relations between political conservatism and dogmatism and intolerance of ambiguity; lack of openness to experience; uncertainty avoidance; personal needs for order, structure, and closure; fear of death; and system threat. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
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W. Chen S. -H. Wang R. Chu F. King T. R. Jack R. R. Fessler 《Metallurgical and Materials Transactions A》2003,34(11):2601-2608
A study was carried out to understand the effect of precyclic loading on stress-corrosion-crack initiation in an X-65 pipeline
steel exposed to a near-neutral-pH soil environment. The test specimens were precyclically loaded before corrosion exposure
to represent a service history of up to about 20 years, depending on the severity of pressure fluctuation. Microcracks had
initiated on the polished surface of the X-65 pipeline steel after long-time exposure at open-circuit potential (OCP) in a
near-neutral-pH synthetic soil solution. These microcracks were mostly initiated from pits at metallurgical discontinuities
such as grain boundaries, pearlitic colonies, and banded phases in the steel. Strong preferential dissolution was observed
along planes of the banded structures in the steel. The selective corrosion attack at these metallurgical discontinuities
is attributed to the galvanic nature of those areas to their neighbors. Cyclic loading prior to corrosion exposure had significant
effects on microcrack initiation and propagation during subsequent corrosion exposure. Cyclic loading prior to corrosion exposure
either reduced or increased the probability of crack initiation and the rate of crack propagation, depending upon the magnitude
of the stress cycles. The largest reduction was seen at a peak cyclic stress of about 0.8 of the yield strength. This cyclic-loading-dependent
cracking behavior might be related to the alteration of the substructures and the residual stress in the steel as a result
of precyclic loading. 相似文献
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The majority of Ss included in studies of psychopathology are typically receiving psychoactive medication. In view of concerns regarding the confounding effects of psychoactive medication, it appears that researchers should provide information regarding at least the drug status of the Ss studied. A review of the articles on adult psychopathology that appeared in the Journal of Abnormal Psychology during a 5-yr period, however, revealed that nearly 50% of reports on Ss presumably receiving psychoactive medications failed to specify the medication status of those Ss. Few studies (15%) provided adequate information regarding the types and dosages of psychoactive drugs received by the Ss. It is argued that researchers should provide a full report of the psychoactive drugs received by research participants and, when participants are unmedicated, to indicate the reasons for drug-free status. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
New climate change scenarios for the Netherlands. 总被引:4,自引:0,他引:4
B van den Hurk A K Tank G Lenderink A van Ulden G J van Oldenborgh C Katsman H van den Brink F Keller J Bessembinder G Burgers G Komen W Hazeleger S Drijfhout 《Water science and technology》2007,56(4):27-33
A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future. 相似文献