1,480 research outputs found
Influence of temperature and sliding speed on the subsurface microstructure evolution of EN AW-6060 under sticking friction conditions
No full textThis article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in AIP Conference Proceedings 1896, 140012 (2017) and may be found at https://doi.org/10.1063/1.5008168.The microstructure evolution of the friction boundary layer of the aluminum alloy EN AW-6060 was investigated. Sticking friction tests at different temperatures and sliding speeds were carried out. A severe deformation below the friction surface was observed by means of LOM and EBSD mapping. Thus, the thickness variation and the grain structure of the high deformation zone could be described. Fibrous structure was observed at 300 °C and 400 °C, while equiaxed grains with high misorientation angle (>15°) were generated at higher temperatures. Additionally, abnormal grain growth and coarse grains were detected at high sliding speeds (10 mm/s, 42 mm/s) at 450°C and 500 °C respectively
Author-Suggested, Weighted Citation Index: A Novel Approach for Determining the Contribution of Individual Researchers
No full textA novel scientometric index, named ‘author-suggested, weighted citation index’ (Aw-index) is proposed to indicate the scientific contribution of any individual researcher. For calculation of the Aw-index, it is suggested that during the submission of a scholarly article, the corresponding author would provide a statement, agreed upon by all the authors, containing weightage factors against each author of the article. The author who contributed more to the article would secure a higher weightage factor. The summation of the weightage factors of all the authors of an article should be unity. The citation points a researcher receives from a scholarly publication is the product of his/her weightage factor for that article and the total number of citations of the article. The Aw-index of any individual researcher is the summation of the citation points he/she receives for all his/her publications as an author. The Aw-index provides the opportunity to the group of authors of a multi-authored article to determine the quantum of partial citations to be attributed to each of them. Through an illustrative example, a comparison of the proposed index with the major scientometric indexes is presented to highlight the advantages of the Aw-index
Acceleration statistics in thermally driven superfluid turbulence
No full textNew methods of flow visualization near absolute zero have opened the way to directly compare quantum turbulence (in superfluid helium) to classical turbulence (in ordinary fluids such as air or water) and explore analogies and differences. We present results of numerical simulations in which we examine the statistics of the superfluid acceleration in thermal counterflow. We find that, unlike the velocity, the acceleration obeys scaling laws similar to classical turbulence, in agreement with a recent quantum turbulence experiment of La Mantia et al
Decay of homogeneous two-dimensional quantum turbulence
No full textWe numerically simulate the free decay of two-dimensional quantum turbulence in a large, homogeneous Bose-Einstein condensate. The large number of vortices, the uniformity of the density profile, and the absence of boundaries (where vortices can drift out of the condensate) isolate the annihilation of vortex-antivortex pairs as the only mechanism which reduces the number of vortices, Nv, during the turbulence decay. The results clearly reveal that vortex annihilation is a four-vortex process, confirming the decay law Nv ∼ t−1/3 where t is time, which was inferred from experiments with relatively few vortices in small harmonically trapped condensates
Vortex-density fluctuations in quantum turbulence
No full textTurbulence in the low-temperature phase of liquid helium is a complex state in which a viscous normal fluid interacts with an inviscid superfluid. In the former vorticity consists of eddies of all sizes and strengths; in the latter vorticity is constrained to quantized vortex lines. We compute the frequency spectrum of superfluid vortex density fluctuations and obtain the same f(-5/3) scaling that has been recently observed. We show that the scaling can be interpreted in terms of the spectrum of reconnecting material lines. To perform this calculation we have developed a vortex tree algorithm which considerably speeds up the evaluation of Biot-Savart integrals
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