H. B. Reitlinger and the origins of the Efficiency at Maximum Power formula for Heat Engines

Even if not so ancient, the history of the heat engine efficiency at maximum power expression have been yet turbulent. More than a decade after the publication of the seminal article by Curzon and Ahlborn in 1975, one's rediscovered two older works by Chambadal and Novikov, both dating from 1957. Then, some years ago, the name of Yvon arose from a textual reference to this famous relation in a conference article published in 1955. Thanks to an historical study of French written books not anymore published for a long time, and since never translated in other languages, we bring to light in this paper that this relation was actually firstly proposed by Henri B. Reitlinger in 1929.Comment: 6 pages, 3 figure

Representing three-dimensional cross fields using 4th order tensors

This paper presents a new way of describing cross fields based on fourth order tensors. We prove that the new formulation is forming a linear space in $\mathbb{R}^9$. The algebraic structure of the tensors and their projections on \mbox{SO}(3) are presented. The relationship of the new formulation with spherical harmonics is exposed. This paper is quite theoretical. Due to pages limitation, few practical aspects related to the computations of cross fields are exposed. Nevetheless, a global smoothing algorithm is briefly presented and computation of cross fields are finally depicted