introduction: presence of surface defects in endodontic instruments can lead to unwanted complications such as instrument fracture and incomplete preparation of the canal. the current study was conducted to evaluate the effect of autoclave cycles on surface characteristics of s-file by scanning electron microscopy (sem). methods and materials: in this experimental study, 17 brand new s-files (#...

Characteristic curves like isophotes, reflection lines and reflection circles are well–established concepts which have been used for automatic fairing of both parametric and piecewise linear surfaces. However, the result of the fairing strongly depends on the choice of a particular family of characteristic curves: isophotes or reflection lines may look perfect for a certain orientation of viewi...

A method of solving the eikonal equation, in either flat or curved space-times, with arbitrary Cauchy data, is extended to the case of data given on a characteristic surface. We find a beautiful relationship between the Cauchy and characteristic data for the same solution, namely they are related by a Legendre transformation. From the resulting solutions, we study and describe the wave-front si...

The Miller-Morita-Mumford classes associate to an oriented surface bundle E → B a class κi(E) ∈ H 2i(B;Z). In this note we define for each prime p and each integer i ≥ 1 a secondary characteristic class λi(E) ∈ H2i(p−1)−2(B;Z)/Zκi(p−1)−1. The mod p reduction λi(E) ∈ H∗(B;Fp) has zero indeterminacy and satisfies pλi(E) = κi(p−1)−1(E) ∈ H ∗(B;Z/p2).

3D modeling of Pd/α-Al2O3 hollow fiber membrane by using computational fluid dynamic for hydrogen separation from H2/N2 mixture was considered in steady and unsteady states by using the concept of characteristic time. Characteristic time concept could help us to design and calculate surface to volume ratio and membrane thickness, and adjust the feed conditions. The contribution of resistance be...