Dual-phase evolution

Résumé

Dual phase evolution (DPE) is a process that drives self-organization within complex adaptive systems. It arises in response to phase changes within the network of connections formed by a system's components. DPE occurs in a wide range of physical, biological and social systems. Its applications to technology include methods for manufacturing novel materials and algorithms to solve complex problems in computation. Introduction Dual phase evolution (DPE) is a process that promotes the emergence of large-scale order in complex systems. It occurs when a system repeatedly switches between various kinds of phases, and in each phase different processes act on the components or connections in the system. DPE arises because of a property of graphs and networks: the connectivity avalanche that occurs in graphs as the number of edges increases. Social networks provide a familiar example. In a social network the nodes of the network are people and the network c

Source officielle

https://en.wikipedia.org/wiki/Dual-phase_evolution

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A Study on the Characteristics of Cu-Mn-Dy Alloy Resistive Thin Films

Ho-Yun Lee

Cu-Mn-Dy resistive thin films were prepared on glass and Al2O3 substrates, which was achieved by co-sputtering the Cu-Mn alloy and dysprosium targets. The effects of the addition of dysprosium on the electrical properties and microstructures of annealed Cu-Mn alloy films were investigated. The composition, microstructural and phase evolution of Cu-Mn-Dy films were characterized using field emission scanning electron microscopy, transmission electron microscopy and X-ray diffraction. All Cu-Mn-Dy films showed an amorphous structure when the annealing temperature was set at 300 degrees C. After the annealing temperature was increased to 350 degrees C, the MnO and Cu phases had a significant presence in the Cu-Mn films. However, no MnO phases were observed in Cu-Mn-Dy films at 350 degrees C. Even Cu-Mn-Dy films annealed at 450 degrees C showed no MnO phases. This is because Dy addition can suppress MnO formation. Cu-Mn alloy films with 40% dysprosium addition that were annealed at 300 degrees C exhibited a higher resistivity of 2100 cm with a temperature coefficient of resistance of -85 ppm/degrees C.

2019

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In this study, SiC ceramic substrates were prepared with 99.5% silicon carbide powders which were came from waste silicon mud during the manufacturing process of solar cells. It is found that a SiO2 layer with 50 nm in thickness is present on the SiC surface by TEM analysis. The relative density of the SiC samples is too low after sintering to 1550 degrees C, which is only 60% of the relative density. It will cause a poor mechanical strength at lower relative density of samples. To improve the density of SiC samples, an amorphous SiO2 was introduced as a sintering aid. Different amounts of amorphous SiO2 from 1 wt% to 5 wt% were then added into SIC powders and made into discs. We call this modified-SiC. These samples were sintered at high temperatures from 1350 degrees C to 1500 degrees C. The SiO2 addition and sintering temperature effects on the density, phase evolution, microstructure and mechanical properties of modified-SiC were investigated. A Y-ZrO2 layer was then coated onto the SiC disc. Sintering temperature can be efficiently decreased and the mismatch between ZrO2 coatings and SiC disc can be reduced when SiO2 is added into SiC. It is found that SiC powders with 3 wt% SiO2 addition shows the most optimum outcome with higher density and stronger mechanical properties.

2019

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Limestone reaction in calcium aluminate cement–calcium sulfate systems

Julien Bizzozero, Karen Scrivener

This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

Elsevier2015

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