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991.
Development (and Evolution) of the Universe 总被引:2,自引:2,他引:0
Stanley N. Salthe 《Foundations of Science》2010,15(4):357-367
I distinguish Nature from the World. I also distinguish development from evolution. Development is progressive change and
can be modeled as part of Nature, using a specification hierarchy. I have proposed a ‘canonical developmental trajectory’
of dissipative structures with the stages defined thermodynamically and informationally. I consider some thermodynamic aspects
of the Big Bang, leading to a proposal for reviving final cause. This model imposes a ‘hylozooic’ kind of interpretation upon
Nature, as all emergent features at higher levels would have been vaguely and episodically present primitively in the lower
integrative levels, and were stabilized materially with the developmental emergence of new levels. The specification hierarchy’s
form is that of a tree, with its trunk in its lowest level, and so this hierarchy is appropriate for modeling an expanding
system like the Universe. It is consistent with this model of differentiation during Big Bang development to view emerging
branch tips as having been entrained by multiple finalities because of the top-down integration of the various levels of organization
by the higher levels. 相似文献
992.
SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from the ladles, mould, and slabs. Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions, morphology, and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al2O3 inclusions, but they turn to fine irregular CaS-CaO-Al2O3 compound inclusions after the treatment, then become fine globular CaO-Al2O3 inclusions in the mould, and finally change to a few larger irregular CaS-CaO-Al2O3 complex inclusions in the slabs. Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca, Al2O3, and S and the precipitation of S in CaO-Al2O3 inclusions with high sulfur capacity. New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling, and the calcium process was studied and optimized. 相似文献
993.
To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites, CNTs were coated by molybdenum layers using metal organic chemical vapor deposition, and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering. The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated. The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders. The electrical conductivity of the composites decreases with increasing Mo-CNT content. When the Mo-CNT content is 0.5wt%, the tensile strength and hardness of Mo-CNT/Al reach their maximum values. The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%, while the electrical conductivity only decreases by 7.1%, relative to sintered pure Al. The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites. 相似文献
994.
The spout-fluidizing characteristics of high-carbon ferromanganese powders with different sizes and masses were studied via a plexiglass spout-fluidized bed with an inner diameter of 30 mm and a height of 1000 mm. The relationships between bed voidage and such parameters as bed height, particle size, fluidizing air velocity, and air flow were obtained. Experimental results show that the powder material with high density can be fluidized in the spout-fluidized bed where the particle size is a key factor influencing the quality of fluidization. 相似文献
995.
The hydrogen absorption kinetics of TA15 titanium alloy at 973–1123 K was studied using a tube-type hydrogen treatment furnace. The hydrogen absorption kinetic curves obtained were analyzed according to a series of mechanism equations to reveal the kinetic parameters and mechanism of the hydrogen absorption process. The results show that both the hydrogen absorption rate and the equilibrium hydrogen pressure increase and the time to reach equilibrium is shortened with increasing temperature. It is found that only the second hydrogen absorption period exists in the hydrogen absorption process of TA15 alloy between 973 and 1123 K, and the activation energy is 54.889 kJ/mol for hydrogen absorption. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results demonstrate that δ hydride forms between 973 and 1123 K, and β phase decreases with the increase of temperature. Orthorhombic α″ martensite is generated at 1073-1123 K, and their amount increases with increasing temperature. 相似文献
996.
In order to get the controlled methods of microstructure homogenization and high strengthening-toughening combination by compact strip production (CSP) rolling, the dynamic recrystallization characteristics of each pass were obtained during CSP rolling using a Gleeble-1500 thermal mechanical simulator. Then, the CSP process was simulated by laboratory rolling experiment. Through thermal mechanical simulation experiment and laboratory rolling experiment, a design idea of Nb-bearing pipeline steel by CSP can be obtained as the following: the level of dynamic recrystallization behavior should be increased through the reasonable balance of high deformation temperature and deformation amount in F1 and F2 passes, and F3-F7 passes should be controlled in the austenite non-recrystallization zone. Finally, X65 pipeline steel with microstructure uniformity and good properties was produced by CSP. The yield strength is up to 497 MPa, the tensile strength is up to 563 MPa, the elongation is 30% on average, and the toughness is very good whose Charpy impact value is 110 J on average and drop-weight tear test shearing areas are all 100% at -60, -40, -20, 0, and 20℃. 相似文献
997.
Constituent phases of the passive film formed on 2205 stainless steel by dynamic electrochemical impedance spectroscopy
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The passive film formed on 2205 duplex stainless steel (DSS) in 0.5 M NaHCO3+0.5 M NaCl aqueous solution was characterized by electrochemical measurements, including potentiodynamic anodic polarization and dynamic electrochemical impedance spectroscopy (DEIS). The results demonstrate that there is a great difference between the passive film evolutions of ferrite and austenite. The impedance values of ferrite are higher than those of austenite. The impedance peaks of ferritic and austenitic phases correspond to the potential of 0.15 and 0.25 V in the low potential range and correspond to 0.8 and 0.75 V in the high potential range. The evolutions of the capacitance of both phases are reverse compared to the evolutions of impedance. The thickness variations obtained from capacitance agree well with those of impedance analysis. The results can be used to explain why pitting corrosion occurs more easily in austenite phase than in ferrite phase. 相似文献
998.
Effects of Si on the stability of retained austenite and temper embrittlement of ultrahigh strength steels
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Effects of silicon (Si) content on the stability of retained austenite and temper embrittlement of ultrahigh strength steels were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and other experimental methods. The results show that Si can suppress temper embrittlement, improve temper resistance, and hinder the decomposition of retained austenite. Reversed austenite appears gradually with the increase of Si content during tempering. Si has a significant effect on enhancing carbon (C) partitioning and improving the stability of retained austenite. Si and C atoms are mutually exclusive in lath bainite, while they attract each other in austenite. ?-carbides are found in 1.8wt% Si steel tempered at 250℃, and they get coarsened obviously when tempered at 400℃, leading to temper embrittlement. Not ?-carbides but acicular or lath carbides lead to temper embrittlement in 0.4wt% Si steel, which can be inferred as cementites and composite compounds. Temper embrittlement is closely related to the decomposition of retained austenite and the formation of reversed austenite. 相似文献
999.
Effects of deoxidizing degree on the pitting corrosion behavior of carbon and manganese steels
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Nine steels with different deoxidizing degrees and two comparative steels were selected. Their pitting initiation susceptibility was compared by means of potentiodynamic polarization tests in 3wt% NaCl solution. The pit propagation rate was evaluated in artificial sea water and 3wt% sea salt solution by simulating occluded corrosion cell (SOCC) test and hanging plate test, respectively. The composition of inclusions and corrosive feature were studied by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and optical microscopy (OM). The results indicate that sulfide inclusions in steel are the sites for pit nucleation. The sulphide inclusions vary in shape from short spindle-like to long strip-like with increasing deoxidizing degree. Under the same conditions, the lower the deoxidizing degree gets, the lower the pitting initiation susceptibility becomes, and the stronger the resistance to pit propagation exhibits. For steels with different deoxidizing degrees, their pitting initiation susceptibility is mainly influenced by thermodynamic stability, while the pit propagation rate is primarily subject to the characteristics of inclusions in steel. 相似文献
1000.
Danda Srinivas Rao Tadiparthi Venkata VijayaKumar Sripada Subba Rao Swarna Prabhakar Guntamadugu Bhaskar Raju 《矿物冶金与材料学报》2011,18(5):515-522
The recovery of iron from the screw classifier overflow slimes by direct flotation was studied. The relative effectiveness of sodium silicates with different silica-to-soda mole ratios as depressants for silica and silicate bearing minerals was investigated. Silica-to-soda mole ratio and silicate dosage were found to have significant effect on the separation efficiency. The results show that an increase of Fe content in the concentrate is observed with concomitant reduction in SiO2 and Al2O3 levels when a particular type of sodium silicate at a proper dosage is used. The concentrate of 58.89wt% Fe, 4.68wt% SiO2, and 5.28wt% Al2O3 with the weight recovery of 38.74% and the metal recovery of 41.13% can be obtained from the iron ore slimes with 54.44wt% Fe, 6.72wt% SiO2, and 6.80wt% Al2O3, when Na2SiO3 with a silica-to-soda mole ratio of 2.19 is used as a depressant at a feed rate of 0.2 kg/t. 相似文献