Analysis of the performance of a new concept for automatic draping of wide reinforcement fabrics with pre-shear:A virtual prototyping study

The layup process of large composite structures made from dry reinforcement fabrics is considered. One such structure is a wind turbine blade, for which the current draping process is mostly manual. Automating the draping process will, therefore, lower the costs. Based on a literature review, a new concept is synthesized and analyzed using an advanced finite element model with rigid multi-body kinematics and a dedicated material model for the fabric. The material model is calibrated using experimental coupon tests, i.e. the bias-extension test (shear) and Peirce's cantilever test (out-of-plane bending). The concept is analyzed numerically by means of a simple parameter study and draping test cases on a flat mold as well as a general double-curved mold. The simulation results show that the concept is feasible for the draping operation and is thus qualified for the subsequent physical prototyping.</p

Ion-intercalation mechanism and structural relaxation in layered iron phosphate Na3Fe3(PO4)4 cathodes

Layered Na3Fe3(PO4)4 can function as a positive electrode for both Li- and Na-ion batteries and may hold advantages from both classical layered and phosphate-based electrode materials. Using a combination of ex-situ and operando synchrotron radiation powder X-ray diffraction, void space analysis, and Mössbauer spectroscopy, we herein investigate the structural evolution of the Na3Fe3(PO4)4 framework during Li- and Na-ion intercalation. We show that during discharge, Li- and Na-intercalation into Na3Fe3(PO4)4 occurs via a solid solution reaction wherein Na-ions appear to be preferentially intercalated into the intralayer sites. The intercalation causes an expansion of the unit cell volume, however at open circuit conditions after ion-intercalation (i.e., after battery discharge), Na3+xFe3(PO4)4 and LixNa3Fe3(PO4)4 undergo a structural relaxation, wherein the unit volume contracts below that of the pristine material. Rietveld refinement suggests that the ions intercalated into the intra-layer sites diffuse to the sites in the inter-layer space during the relaxation. This behavior brings new perspectives to understanding structural relaxation and deviations between structural evolution observed under dynamic and static conditions

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure