Improved Interaction Formula for the Plastic Resistance of I- and H-Sections under a Combination of Bending Moments My,Ed, Mz,Ed, and Bimoment BEd

[EN] The resistances of HVH sections (H-horizontal upper flange, V-vertical web, H-horizontal bottom flange) were investigated by the authors in the frame of the large parametrical studies focused on the complete HVH-section categories: channels, Z-sections, I-sections, and H-sections. The three different variants of the approximate formulae for the calculation of the elastic and plastic resistances of I-shaped sections loaded by several internal forces were previously published by the authors. In this paper, the improved approximate formulae are presented for the plastic resistance of I- and H-sections loaded by bending moments M-y,M-Ed, M-z,M-Ed, and bimoment B-Ed. It is shown in the graphical form that the proposed approximate formulae give almost identical values of relative plastic resistances of I-shaped sections to the exact solution, in which Pattern Search Algorithm, offered by MATLAB, is used. It is proven that the proposed approximate formulae are better then previous authors' formulae, which are themselves better than the older Greek proposal and the newer German proposals. The approximate formulae may be used in the CEN Technical Specification (TS) or in Non Contradictory Complementary Information (NCCI) for supporting safe and economical design according to metal (steel and aluminum) Eurocodes.This research, project no. 1/0453/20, is funded by the Slovak Grant Agency VEGA. The APC was funded by the Slovak Grant Agency VEGA, project no. 1/0453/20.Aguero Ramón Llin, A.; Balaz, I.; Koleková, Y. (2022). Improved Interaction Formula for the Plastic Resistance of I- and H-Sections under a Combination of Bending Moments My,Ed, Mz,Ed, and Bimoment BEd. Applied Sciences. 12(15):1-9. https://doi.org/10.3390/app1215788819121

INVESTIGATION OF METAL BUILT-UP COLUMNS PART I: FORMULAE

[EN] Eurocodes give guidance how to design built-up columns having effective bending stiffness, smeared shear stiffness and local bow imperfection amplitude e0 = L/500 under compression. The guidance is valid only for columns supported by hinges at their ends. The second order theory is presented, which allows analysis of the battened and laced built-up columns with initial imperfection under combined compression and bending with the bottom end fixed and the upper one free in the case of in-plane buckling. The application of the theory in several numerical examples is given in Part II.Project No. 1/0453/20 is supported by the Slovak Grant Agency VEGABalaz, I.; Koleková, Y.; Moroczová, L.; Aguero Ramón Llin, A. (2021). INVESTIGATION OF METAL BUILT-UP COLUMNS PART I: FORMULAE. Pollack Periodica (Online). 16(1):65-70. https://doi.org/10.1556/606.2020.00285S657016

Fabrication of bottle-shaped nanochannels in fused silica using a self-closing effect

The spatial control of molecular motor function, using nanostructured surfaces, is of great interest for the development of commercial devices for diagnostics and high-throughput drug screening with molecular motors as targets. In the present study we have fabricated 100-300 nm wide nanochannels, completely subsurfaced on fused silica chips, with the aim to interface them with a microfluidic system. Such a system will allow for changes in the chemical environment surrounding molecular motors, with minimal influence on their directional motion. This will be achieved by changing the chemical environment in a perpendicular direction to the motor motion and allowing the chemical substances to diffuse in and out of the nanochannels via a small slit (5-10 nm) on the top of the nanochannels. To create this slit, and to control its width, we here demonstrate the use of a self-closing effect based on the volume increase (2.27 times) during oxidation of silicon. The details of the fabrication steps (EBL, RIE and oxidation) are discussed. (C) 2012 Elsevier B.V. All rights reserved

Optimization of a self-closing effect to produce nanochannels with top slits in fused silica

The authors report on the fabrication of subsurfaced 100-600 nm wide nanochannels in fused silica with top slit openings in the size range of 5-10 nm. Such nanochannels can be used in combination with a nanofluidics system to guide molecular motors and quickly switch the chemical environment inside the nanochannels through diffusion via the top slits. To realize nanochannel top slits in this size range, the authors here demonstrate the use of a self-closing effect based on the volume expansion of a thin Si layer during oxidation. A high contrast electron beam lithography exposure step in conjunction with dry etching of SiO2 by reactive ion etching (RIE) and Si by inductively coupled plasma-RIE followed by wet etching of a fused silica substrate is used to create the initial slit before oxidation. The details of nanochannel fabrication steps are described and discussed. (C) 2012 American Vacuum Society. [http://dx.doi.org/10.1116/1.4766317

Hallmarks of mechanochemistry: from nanoparticles to technology

Équipe 401 : Nanomatériaux pour la vie et développement durableInternational audienceThe aim of this review article on recent developments of mechanochemistry (nowadays established as a part of chemistry) is to provide a comprehensive overview of advances achieved in the field of atomistic processes, phase transformations, simple and multicomponent nanosystems and peculiarities of mechanochemical reactions. Industrial aspects with successful penetration into fields like materials engineering, heterogeneous catalysis and extractive metallurgy are also reviewed. The hallmarks of mechanochemistry include influencing reactivity of solids by the presence of solid-state defects, interphases and relaxation phenomena, enabling processes to take place under non-equilibrium conditions, creating a well-crystallized core of nanoparticles with disordered near-surface shell regions and performing simple dry time-convenient one-step syntheses. Underlying these hallmarks are technological consequences like preparing new nanomaterials with the desired properties or producing these materials in a reproducible way with high yield and under simple and easy operating conditions. The last but not least hallmark is enabling work under environmentally friendly and essentially waste-free conditions (822 references)

Porous Nb₂O₅ nanofibers prepared via reactive needle-less electrospinning for application in lithium–sulfur batteries

This contribution describes the preparation, coupled with detailed characterization, of Nb2O5 nanofibers and their application in lithium–sulfur batteries for the improvement of electrochemical performance. The utilization of reactive needle-less electrospinning allowed us to obtain, in a single step, amorphous pre-ceramic composite PAN/Nb2O5fibers, which were transformed into porous ceramic Nb2O5 nanofibers via calcination. Thermogravimetric studies defined that calcination at 600 ◦C results in crystalline ceramic fibers without carbon residues. The fibrous morphology and mean diameter (614 ± 100 nm) of the ceramic nanofibers were analyzed via scanning and transmission electron microscopy. A surface area of 7.472 m2/g was determined through nitrogen adsorption measurements, while a combination of X-ray diffraction and Raman spectroscopy was used to show the crystallinity and composition of the fibers after calcination—single T-phase Nb2O5 . Its performance in the cathode of lithium–sulfur batteries was defined through electrochemical tests, and the obtained results were compared to a similar blank electrode. The initial discharge capacity of 0.5 C reached a value of 570 mAh·g−1 , while the reversible capacity of 406 mAh·g−1 was retained after 200 cycles, representing a capacity retention of 71.3%. The presence of Nb2O5 nanofibers in the carbon cathode inhibits the shuttle effect through polysulphide confinement, which originates from porosity and chemical trapping.</p