Mechanical Barkhausen noise during fatigue of iron

In this paper, the potentiality for using the mechanical Barkhausen noise (BN) to monitor fatigue tests of ferrous materials is investigated. The fatigue tests are carried out on iron specimens subjected to rotational bending on a standard fatigue bench. The mechanical BN is detected using an encircling coil. The mechanical BN exhibits three main stages during the fatigue life: it increases at the beginning of the test, then a plateau is reached and finally it decreases before rupture. These successive stages can be associated to the classical stages of the fatigue life of metals and alloys: crystalline microstructure changes, a saturation stage, and microcrack nucleation and growth leading to rupture. An early indicator of damage is derived from the results.     

Guiding the Morphology of Amyloid Assemblies by Electrostatic Capping: from Polymorphic Twisted Fibrils to Uniform Nanorods

Peptides that self‐assemble into cross‐β‐sheet amyloid structures constitute promising building blocks to construct highly ordered proteinaceous materials and nanoparticles. Nevertheless, the intrinsic polymorphism of amyloids and the difficulty of controlling self‐assembly currently limit their usage. In this study, the effect of electrostatic interactions on the supramolecular organization of peptide assemblies is investigated to gain insights into the structural basis of the morphological diversities of amyloids. Different charged capping units are introduced at the N‐terminus of a potent β‐sheet‐forming sequence derived from the 20–29 segment of islet amyloid polypeptide, known to self‐assemble into polymorphic fibrils. By tuning the charge and the electrostatic strength, different mesoscopic morphologies are obtained, including nanorods, rope‐like fibrils, and twisted ribbons. Particularly, the addition of positive capping units leads to the formation of uniform rod‐like assemblies, with lengths that can be modulated by the charge number. It is proposed that electrostatic repulsions between N‐terminal positive charges hinder β‐sheet tape twisting, leading to a unique control over the size of these cytocompatible nanorods by protofilament growth frustration. This study reveals the high susceptibility of amyloid formation to subtle chemical modifications and opens to promising strategies to control the final architecture of proteinaceous assemblies from the peptide sequence.     

Effect of Impeller Blade Height on the Drop Size Distribution in Agitated Dispersions

A common method to achieve a contact of two liquid phases – required for many chemical engineering operations – is the dispersion of one into the other by mechanical agitation. The drop size distribution in such an agitated dispersion is a result of the dynamic equilibrium existing between the breaking and coalescing drops. A comparison has been made of drop diameters produced by four disk type impellers differing only in blade height (D_W = 1, 2, 4 and 6 cm). Measurements in situ at 200, 250, 300, 350, 400, 450 rpm and at holdup fractions 0.02, 0.05, and 0.07, showed that the Sauter mean drop diameters increased up to 140 % as the impeller blade height decreased from 6 to 1 cm. Plots of ln α₃₂ vs. ln N, lnα₃₂ vs. ln D_T and ln α₃₂ vs. ln α_max gave straight lines.     

Availability of Cellular Systems Based on Space Domain

Wireless Personal Communications - Ultra-Reliable Communication (URC) is one of the promising features in 5G to provide anytime and anywhere services to the end users. Services related to URC...     

Interference Management for Different 5G Cellular Network Constructions

Wireless Personal Communications - Due to the technology growth in the fifth Generation (5G) in the modern era, there is an urgent need for Ultra-Reliable Communications (URC). It is considered one...