An Optimization method for the Configuration of Inter Array Cables for Floating Offshore Wind Farm.

International audienceIFP Energies nouvelles (IFPEN) is involved for many years in various projects for the development of floating offshore wind turbines. The commercial deployment of such technologies is planned for 2020. The present paper proposes a methodology for the numerical optimization of the inter array cable configuration. To illustrate the potential of such an optimization, results are presented for a case study with a specific floating foundation concept [1]. The optimization study performed aims to define the least expensive configuration satisfying mechanical constraints under extreme environmental conditions. The parameters to be optimized are the total length, the armoring, the stiffener geometry and the buoyancy modules. The insulated electrical conductors and overall sheath are not concerned by this optimization. The simulations are carried out using DeepLines TM , a Finite Element software dedicated to simulate offshore floating structures in their marine environment. The optimization problem is solved using an IFPEN in-house tool, which integrates a state of the art derivative-free trust region optimization method extended to nonlinear constrained problems. The latter functionality is essential for this type of optimization problem where nonlinear constraints are introduced such as maximum tension, no compression, maximum curvature and elongation, and the aero-hydrodynamic simulation solver does not provide any gradient information. The optimization tool is able to find various local feasible extrema thanks to a multi-start approach, which leads to several solutions of the cable configuration. The sensitivity to the choice of the initial point is demonstrated, illustrating the complexity of the feasible domain and the resulting difficulty in finding the global optimum configuration

Continuation vs Discontinuation of Renin-Angiotensin System Inhibitors Before Major Noncardiac Surgery

ImportanceBefore surgery, the best strategy for managing patients who are taking renin-angiotensin system inhibitors (RASIs) (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) is unknown. The lack of evidence leads to conflicting guidelines.ObjectiveTo evaluate whether a continuation strategy vs a discontinuation strategy of RASIs before major noncardiac surgery results in decreased complications at 28 days after surgery.Design, setting, and participantsRandomized clinical trial that included patients who were being treated with a RASI for at least 3 months and were scheduled to undergo a major noncardiac surgery between January 2018 and April 2023 at 40 hospitals in France.InterventionPatients were randomized to continue use of RASIs (n = 1107) until the day of surgery or to discontinue use of RASIs 48 hours prior to surgery (ie, they would take the last dose 3 days before surgery) (n = 1115).Main outcomes and measuresThe primary outcome was a composite of all-cause mortality and major postoperative complications within 28 days after surgery. The key secondary outcomes were episodes of hypotension during surgery, acute kidney injury, postoperative organ failure, and length of stay in the hospital and intensive care unit during the 28 days after surgery.ResultsOf the 2222 patients (mean age, 67 years [SD, 10 years]; 65% were male), 46% were being treated with angiotensin-converting enzyme inhibitors at baseline and 54% were being treated with angiotensin receptor blockers. The rate of all-cause mortality and major postoperative complications was 22% (245 of 1115 patients) in the RASI discontinuation group and 22% (247 of 1107 patients) in the RASI continuation group (risk ratio, 1.02 [95% CI, 0.87-1.19]; P = .85). Episodes of hypotension during surgery occurred in 41% of the patients in the RASI discontinuation group and in 54% of the patients in the RASI continuation group (risk ratio, 1.31 [95% CI, 1.19-1.44]). There were no other differences in the trial outcomes.Conclusions and relevanceAmong patients who underwent major noncardiac surgery, a continuation strategy of RASIs before surgery was not associated with a higher rate of postoperative complications than a discontinuation strategy.Trial registrationClinicalTrials.gov Identifier: NCT03374449

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