Effect of laser-scan strategy on microstructure and fatigue properties of 316L additively manufactured stainless steel

The particular roles of grain morphology and defects, controlled using laser-scan strategies, on the mechanical properties and the fatigue behavior of 316L stainless steel are investigated. Microstructural characterization and X-ray tomography analysis was performed to understand the genesis of polycrystalline microstructure and defects. Tensile and fatigue tests were performed to analyze the effect of defect population and microstructural properties on plasticity and damage mechanisms during monotonic and cyclic loading. The effect of the grain-size and shape and type of defect was carefully investigated to evaluate the mechanisms driving the mechanical behavior under quasi-static and fatigue loading. It is shown that the laser-scan strategy determines the anisotropy in the plane perpendicular to the building direction. Moreover, contrary to the existing literature, for 316L obtained by AM, the grain size and shape does not affect the mechanical properties, and LoF defects drive the fatigue life, independent of the defect/grain size ratio.     

3D Printable Gelatin Methacryloyl (GelMA)-Dextran Aqueous Two-Phase System with Tunable Pores Structure and Size Enables Physiological Behavior of Embedded Cells In Vitro

The restricted porosity of most hydrogels established for in vitro 3D tissue engineering applications limits embedded cells with regard to their physiological spreading, proliferation, and migration behavior. To overcome these confines, porous hydrogels derived from aqueous two-phase systems (ATPS) are an interesting alternative. However, while developing hydrogels with trapped pores is widespread, the design of bicontinuous hydrogels is still challenging. Herein, an ATPS consisting of photo-crosslinkable gelatin methacryloyl (GelMA) and dextran is presented. The phase behavior, monophasic or biphasic, is tuned via the pH and dextran concentration. This, in turn, allows the formation of hydrogels with three distinct microstructures: homogenous nonporous, regular disconnected-pores, and bicontinuous with interconnected-pores. The pore size of the latter two hydrogels can be tuned from ≈4 to 100 µm. Cytocompatibility of the generated ATPS hydrogels is confirmed by testing the viability of stromal and tumor cells. Their distribution and growth pattern are cell-type specific but are also strongly defined by the microstructure of the hydrogel. Finally, it is demonstrated that the unique porous structure is sustained when processing the bicontinuous system by inkjet and microextrusion techniques. The proposed ATPS hydrogels hold great potential for 3D tissue engineering applications due to their unique tunable interconnected porosity.     

A Reframed Watermark Extraction Approach Using the ABC Algorithm

The fast development and the rapid spread of information technology have raised the issue of digital-image copyright protection,which was mostly addressed through robust watermarking.To ensure the survival of the watermark after attacks,most works have been making use of an additional step at the embedding phase,and by so making the scheme unsuitable for real-time implementation.However,to be effective and secure,it is recommended to combine the watermarking algorithm and the capture sensor in one device.In this paper,we brought the extra stage to the detection side.We firstly studied the effect of some signal processing operations on a watermarked image,then we proposed a general model for watermark extraction whose parameters were determined using the artificial bee colony.The efficacy of the proposed method was validated by comparing its robustness with two state-of-art schemes focusing on the watermark extraction.     

Synthesis of some additives from upgraded petroleum residues of lubricant oil refineries

Aromatic extract residues occur as by‐products in petroleum refineries, through the process of refining lubricant oil. These residues are considered as having low economic value, and their disposal may even cause problems for the refineries. The present work looks at upgrading these residues by using them to synthesise different petroleum additives, e.g., antioxidants, ashless dispersants, pour‐point depressants, and flow improvers for lubricating crankcase oils and for fuels. The antioxidants were synthesised by reacting mono‐aromatics with phosphorus pentasulphide (P₂S₅) in the presence of zinc oxide (ZnO). Ashless dispersant additives were synthesised by reacting alkylated mono‐aromatics (using chlorinated paraffin wax as an alkylating agent) with formaldehyde solution (37%) in the presence of polyisobutylene succinimide. Fuel pour‐point depressants and flow improvers can be synthesised by acylating di‐aromatics via a Friedel‐Crafts reaction. Comparative evaluation of the synthesised products with commercial additives showed them to have good comparative performance properties.