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Gamma double prime (γ"): This phase typically is Ni 3 Nb or Ni 3 V and is used to strengthen Ni-based superalloys at lower temperatures (<650 °C) relative to γ'. The crystal structure of γ" is body-centered tetragonal (BCT), and the phase precipitates as 60 nm by 10 nm discs with the (001) planes in γ" parallel to the {001} family in γ.
In age-hardening or precipitation-strengthening varieties, small amounts of niobium combine with nickel to form the intermetallic compound Ni 3 Nb or gamma double prime (γ″). Gamma prime forms small cubic crystals that inhibit slip and creep effectively at elevated temperatures. The formation of gamma-prime crystals increases over time ...
In these alloys the volume fraction of the γ' precipitates is as high as 80%. [7] Because of this high volume fraction, the evolution of these γ' precipitates during the alloys' life cycles is important: a major concern is the coarsening of these γ' precipitates at high temperature (800 to 1000 °C), which greatly reduces the alloys ...
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period.
The Gathering Hypothesis is a view that states men provided the evolution of the current human through hunting while women contributed via gathering. [5] Though criticized by many, it provides clues that both hunting and gathering were patterns of acquiring food and resources.
As evolution can produce highly optimised processes and networks, it has many applications in computer science. Here, simulations of evolution using evolutionary algorithms and artificial life started with the work of Nils Aall Barricelli in the 1960s, and was extended by Alex Fraser , who published a series of papers on simulation of ...
The theory of recapitulation, also called the biogenetic law or embryological parallelism—often expressed using Ernst Haeckel's phrase "ontogeny recapitulates phylogeny"—is a historical hypothesis that the development of the embryo of an animal, from fertilization to gestation or hatching (), goes through stages resembling or representing successive adult stages in the evolution of the ...
Professor of animal physiology and experienced scuba and freediver Erika Schagatay researches human diving abilities and oxygen stress. She suggests that such abilities are consistent with selective pressure for underwater foraging during human evolution, and discussed other anatomical traits speculated as diving adaptations by Hardy/Morgan. [72]