Elucidation of role of graphene in catalytic designs for electroreduction of oxygen

Graphene is, in principle, a promising material for consideration as component (support, active site) of electrocatalytic materials, particularly with respect to reduction of oxygen, an electrode reaction of importance to low-temperature fuel cell technology. Different concepts of utilization, including nanostructuring, doping, admixing, preconditioning, modification or functionalization of various graphene-based systems for catalytic electroreduction of oxygen are elucidated, as well as important strategies to enhance the systems' overall activity and stability are discussed

Correlation Between Friction and Wear of Cubic Borone Nitride Cutting Tools in Precision Hard Machining

In this paper, the contribution of tool wear to friction was determined for precision hard turning using Cubic Borone Nitride (CBN) cutting tools. The tool nose wear VB C and the corresponding changes of component forces F c , F f , and F p resulting from tool wear evolution were continuously measured during wear tests. Based on the mechanics of nonorthogonal cutting, the normal and friction forces acting on rake and flank faces were calculated for all measuring points, and as a result, relevant changes of the friction coefficient were determined. Additionally, friction changes resulting from tool wear under different feed rate, depth of cut, and tool nose radius were discussed in terms of the plowing energy produced by the tool nose

A ligand discovery toolbox for the WWE domain family of human E3 ligases

The WWE domain is a relatively under-researched domain found in twelve human proteins and characterized by a conserved tryptophan-tryptophan-glutamate (WWE) sequence motif. Six of these WWE domain-containing proteins also contain domains with E3 ubiquitin ligase activity. The general recognition of poly-ADP-ribosylated substrates by WWE domains suggests a potential avenue for development of Proteolysis-Targeting Chimeras (PROTACs). Here, we present novel crystal structures of the HUWE1, TRIP12, and DTX1 WWE domains in complex with PAR building blocks and their analogs, thus enabling a comprehensive analysis of the PAR binding site structural diversity. Furthermore, we introduce a versatile toolbox of biophysical and biochemical assays for the discovery and characterization of novel WWE domain binders, including fluorescence polarization-based PAR binding and displacement assays, 15N-NMR-based binding affinity assays and 19F-NMR-based competition assays. Through these assays, we have characterized the binding of monomeric iso-ADP-ribose (iso-ADPr) and its nucleotide analogs with the aforementioned WWE proteins. Finally, we have utilized the assay toolbox to screen a small molecule fragment library leading to the successful discovery of novel ligands targeting the HUWE1 WWE domain

Energy-based characterization of precision hard machining using partially worn CBN cutting tools

This paper highlights the performance of precision hard turning with CBN cutting tools from energy point-of-view with additional tool wear effect. For this purpose several wear tests were performed during which the tool nose wear VBC and the corresponding changes of component forces Fc, Ff and Fp were continuously measured. Based on the measured forces and geometrical characteristic of the uncut layer, specific cutting and ploughing energy were determined for several combinations of cutting parameters. Consequently, changes of energy consumption resulting from tool wear evolution for variable feed rate, depth of cut and tool nose radius were presented

Characteristics of geometric structure of the surface after grinding

This paper presents the technological and functional capabilities of surface textures produced by cutting and grinding operations on hardened steel of about 54 HRC hardness. Special focus was placed on surface textures generated by hard turning and grinding operations which are characterized by the Sz roughness parameter of about 3 - 4 μm and distinctly similar values of the Sa parameter. A set of 3D surface roughness parameters was used to characterize the superficial effects of precision grinding operations and their influence on the parts functionality

Characteristics of geometric structure of the surface after grinding

This paper presents the technological and functional capabilities of surface textures produced by cutting and grinding operations on hardened steel of about 54 HRC hardness. Special focus was placed on surface textures generated by hard turning and grinding operations which are characterized by the Sz roughness parameter of about 3 - 4 μm and distinctly similar values of the Sa parameter. A set of 3D surface roughness parameters was used to characterize the superficial effects of precision grinding operations and their influence on the parts functionality

Investigation of Friction and Wear Mechanisms of TiAlV Coated Carbide Against Ti6Al4V Titanium Alloy Using Pin-On-Disc Tribometer

The tribological behavior of the PVD-TiAlN coated carbide inserts in dry sliding against two-phase (α-β) titanium alloy,Ti6Al4V grade, was investigated. A modified pin-on-disc device was used to conduct experiments under variable normal load and sliding speed. Scanning electron microscopy (SEM) and X-ray micro-analyses by EDS were applied for observations of wear scars and wear products. It was revealed that the increase of sliding speed contributes to decreasing the friction coefficient under a low normal force, whereas the increase of the normal loading causes the friction coefficient is less sensitive to changes in the sliding speed and its values are equal to μ = 0.26-0.34. The adhesive nature of wear along with severe abrasive action of the Ti alloy were documented

Redesign of the Disribution System Based on Simulation Technique and MCDA* Methodology

The heuristic/intuitive redesign of the distribution system is considered in the paper. The redesign process is based on simulation techniques and MCDA methods. Seven different variants (development scenarios) of the distribution system have been designed. The values of ten characteristics (criteria) of the distribution system have been simulated by Taylor ED simulation package. The variants of the distribution system have been ranked from the best to the worst with an application of five MCDA methods: ELECTRE III, ORESTE, AHP, UTA and MAPPAC. The comparative analysis of final rankings led authors to the conclusions on the quality of the generated results and a suitability of the MCDA methods to the redesign of the distribution system

Tool life of ceramic wedges during precise turning of tungsten

Properties, application and machinability of tungsten and its alloys have been demonstrated. The comparison of the tool life and wear of the wedges made of SiAlON and whisker ceramics during the precise turning at different cutting parameters have been presented. The CNC lathe DMG CTX 310 Ecoline and tungsten of 99.7 % purity were used during the experiments. Only the wedge of whisker ceramics has proved to be sufficiently suitable and only for relatively low cutting speeds