Editorial overview: Reaction and catalysis engineering — Fundamental innovation across length scales

2015 ◽  
Vol 9 ◽  
pp. vi-viii
Author(s):  
Marc-Olivier Coppens ◽  
Theodore T Tsotsis
2012 ◽  
Vol 40 (2) ◽  
pp. 124-150
Author(s):  
Klaus Wiese ◽  
Thiemo M. Kessel ◽  
Reinhard Mundl ◽  
Burkhard Wies

ABSTRACT The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.


Impact ◽  
2018 ◽  
Vol 2018 (1) ◽  
pp. 48-50
Author(s):  
Toralf Scharf ◽  
Paul Urbach ◽  
Carsten Rockstuhl ◽  
Frank Setzpfand

Author(s):  
Christopher Cullen

We look first at the situation in the early years of the restored Han dynasty. Liu Xin’s system continued in use for more than half a century. Then, in 85 CE, Liu Xin’s system was replaced. We have records of the practical and theoretical grounds on which the old system was rejected, and of the creation and implementation of a new system. Next we follow the story of how c. 92 CE Jia Kui advocated a fundamental innovation in both theory and practice: he insisted on the ecliptic as being central to astronomical observation and calculation. The richness of records from this period makes it easy to tell a detailed story of technical innovation in its fullest context, leading up to the work of Zhang Heng (78–139 CE), for whom astronomical calculation was just one of several fields in which he gained a reputation for exceptional originality.


2020 ◽  
Vol 22 (36) ◽  
pp. 20914-20921 ◽  
Author(s):  
Rajmohan Muthaiah ◽  
Jivtesh Garg

We report novel pathways to significantly enhance the thermal conductivity at nanometer length scales in boron phosphide through biaxial strain.


Author(s):  
Mathaeus Tschaikowsky ◽  
Tanja Neumann ◽  
Sofia Brander ◽  
Heiko Haschke ◽  
Bernd Rolauffs ◽  
...  

The Analyst ◽  
2021 ◽  
Vol 146 (1) ◽  
pp. 69-74
Author(s):  
Elizabeth Kautz ◽  
John Cliff ◽  
Timothy Lach ◽  
Dallas Reilly ◽  
Arun Devaraj

235U enrichment in a metallic nuclear fuel was measured via NanoSIMS and APT, allowing for a direct comparison of enrichment across length scales and resolutions.


2021 ◽  
Vol 126 (7) ◽  
Author(s):  
Adbhut Gupta ◽  
J. J. Heremans ◽  
Gitansh Kataria ◽  
Mani Chandra ◽  
S. Fallahi ◽  
...  

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