Effective Chorin–Temam algebraic splitting schemes for the steady Navier–stokes equations

This paper continues some recent work on the numerical solution of the steady incompressible Navier–Stokes equations. We present a new method, similar to the one presented in Rebholz et al., but with superior convergence and numerical properties. The method is efficient as it allows one to solve the same symmetric positive‐definite system for the pressure at each iteration, allowing for the simple preconditioning and the reuse of preconditioners. We also demonstrate how one can replace the Schur complement system with a diagonal matrix inversion while maintaining accuracy and convergence, at a small fraction of the numerical cost. Convergence is analyzed for Newton and Picard‐type algorithms, as well as for the Schur complement approximation

A Penalty-projection based Efficient and Accurate Stochastic Collocation Method for Magnetohydrodynamic Flows

We propose, analyze, and test a penalty projection-based efficient and accurate algorithm for the Uncertainty Quantification (UQ) of the time-dependent Magnetohydrodynamic (MHD) flow problems in convection-dominated regimes. The algorithm uses the Els\"asser variables formulation and discrete Hodge decomposition to decouple the stochastic MHD system into four sub-problems (at each time-step for each realization) which are much easier to solve than solving the coupled saddle point problems. Each of the sub-problems is designed in a sophisticated way so that at each time-step the system matrix remains the same for all the realizations but with different right-hand-side vectors which allows saving a huge amount of computer memory and computational time. Moreover, the scheme is equipped with ensemble eddy-viscosity and grad-div stabilization terms. The stability of the algorithm is proven rigorously. We prove that the proposed scheme converges to an equivalent non-projection-based coupled MHD scheme for large grad-div stabilization parameter values. We examine how Stochastic Collocation Methods (SCMs) can be combined with the proposed penalty projection UQ algorithm. Finally, a series of numerical experiments are given which verify the predicted convergence rates, show the algorithm's performance on benchmark channel flow over a rectangular step, and a regularized lid-driven cavity problem with high random Reynolds number and magnetic Reynolds number.Comment: 28 pages, 13 figure

Highly efficient blue OLED

Based on our work on deep blue OLED, very recently, we have synthesized a deep blue emitter TPEA. The anthracene groups are twisted from the central TPE moiety, which effectively prevents bathochromic shift of emission as shown in its crystallographic structure. In addition, a D-A structure was built by using methoxy and cyano to improve the charge balance in the devices. In addition, the material possesses high thermal stability with a Tg of 155 °C. The non-doped device achieved the high performance with a Von of 2.6 V at a luminance of 1 cd rrr2, a 77PE, max Of 11.1 lm W~1, a TJCE, max of 9.9 cd A '1, and a low 77ce roll-off. The doped device based on TPEA was fabricated to acquire deep blue emission with CIE coordinates of (0.15, 0.09), showing a tje x t, max up to 8.0% and the highest t j p e, max of 7.3 lm W"1 among all the TTF and HLCT deep-blue emitters. Inspired by these preliminary results, we believe that the combination of the merits of TTF-HLCT and AIE would be a promising molecular design principle for exploring highly efficient deep blue emitters

Genomic monitoring of SARS-CoV-2 uncovers an Nsp1 deletion variant that modulates type I interferon response

The SARS-CoV-2 virus, the causative agent of COVID-19, is undergoing constant mutation. Here, we utilized an integrative approach combining epidemiology, virus genome sequencing, clinical phenotyping, and experimental validation to locate mutations of clinical importance. We identified 35 recurrent variants, some of which are associated with clinical phenotypes related to severity. One variant, containing a deletion in the Nsp1-coding region (D500-532), was found in more than 20% of our sequenced samples and associates with higher RT-PCR cycle thresholds and lower serum IFN-beta levels of infected patients. Deletion variants in this locus were found in 37 countries worldwide, and viruses isolated from clinical samples or engineered by reverse genetics with related deletions in Nsp1 also induce lower IFN-beta responses in infected Calu-3 cells. Taken together, our virologic surveillance characterizes recurrent genetic diversity and identified mutations in Nsp1 of biological and clinical importance, which collectively may aid molecular diagnostics and drug design.Peer reviewe

Efficient nonlinear iteration schemes based on algebraic splitting for the incompressible Navier-Stokes equations

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