Study of Different Printing Design Type Polymer Samples Prepared by Additive Manufacturing

3D printing is one of the most progressive additive technologies today. It finds its application also in industry. In terms of mechanical properties, the printing design of the product is an important parameter. The presented study investigates the effects of the printing design of a thin-walled 3D polymer model on the mechanical properties of the model. The material used for printing was acrylonitrile-butadiene-styrene (ABS) and the 3D print method was Fused Deposition Modeling (FDM). ABS was tested at various die temperatures and with various printing designs at a constant 3D print speed and identical print bed temperature. We examined the effect of printing temperature and product printing design on the resulting mechanical properties. We compared theoretical and experimental results by CAE–FEM Advanced Simulation modules. Results tensile deformations at maximum load by experiment and simulations are comparable. The best results of testing the mechanical properties were found in the pattern printed at a 45° angle at temperature 285 °C

Force Distribution Along Tree Branch – Static Analysis

The standard approach of tree stability assessment assumes that wind force is applied in a unique point (centre of gravity). Such a description of the loading brings a significant simplification of the reality, where the tree stem is submitted to multiple forces distributed from higher-order branches to lower order one. The aim of this study is to describe the influence of the simplification by comparison of branch response (deflection curve, bending moment) in the case of singleand the multi-point loading. Four beam-like models were built in ANSYS APDL according to geometry (tapered beams with realistic elliptical cross-sections) and material properties (shear included) of real tested branches. The models were experimentally validated in the case of single-point loading and consequently used for simulations of various loading scenarios. The distribution of force along the branches, by weighted division of total wind force according to different properties of branches, was applied. The branch response differs between singleand multi-point loading in the case of deflection curve, whereas the bending moment at branch anchorage is comparable

Properties of Carbon Nanotubes and Their Use in Potential Applications

Many laboratories in the world are doing research in the field of nanotechnology. Among lot of nanomaterials carbon nanotubes became very popular because of their unique properties which could be used in many applications. But first, lot of problems with their preparation need to be solved

Enantioselective Transition-Metal Catalysis via Anion Binding with Chiral Hydrogen-Bond Donors

Asymmetric transition-metal catalysis represents a powerful strategy for accessing enantiomerically enriched molecules. Here, we report a new approach for inducing enantioselectivity in transition-metal-catalyzed reactions that relies on neutral hydrogen-bond donors (HBDs) that bind anions of transition-metal complexes to achieve enantiocontrol and rate enhancement through ion pairing in concert with other noncovalent interactions. A cooperative anion-binding effect of a chiral bis-thiourea HBD is demonstrated to lead to high enantioselectivity (up to 99% enantiomeric excess) in intramolecular ruthenium-catalyzed propargylic substitution reactions. Experimental and computational mechanistic studies reveal the attractive interactions between electron-deficient arene components of the HBD and the metal complex that underlie enantioinduction and the acceleration effect