Data-driven Balanced Truncation for Predictive Model Order Reduction of Aeroacoustic Response

Rapid prediction of the aeroacoustic response is a key component in the design of aircraft and turbomachinery. While it is possible to achieve accurate predictions using direct solution of the compressible Navier-Stokes equations, applications of such solvers is not feasible in design optimization due to the high cost of resolving wave phenomena in an Eulerian setting. In this work, we propose a technique for highly accelerated predictions of aeroacoustic response using a data-driven model reduction approach based on the eigensystem realization algorithm (ERA), as a non-intrusive balanced truncation method. Specifically, we create and compare ERA ROMs based on the training data generated by solving the linearized and nonlinear Euler equations with Gaussian pulse inputs, and use them for prediction of the aeroacoustic response of an airfoil subject to different types of gust loading. The results show that both ROMs are in good agreement with the full-order model (FOM) solution in a purely predictive setting, while achieving orders of magnitude reduction in the online computation time. Using ERA for prediction of the acoustic response requires activating each input channel separately in the FOM for training ROMs, and operating on a large Hankel matrix, that can become computationally infeasible. We address this bottleneck in two steps: first, we propose a multi-fidelity gappy POD method to identify the most impactful input channels based on a coarser grid. Therefore, we reduce the computation cost on the FOM and ROM levels as we build the Markov sequence by querying the high-resolution FOM only for the input channels identified by gappy POD. Second, we use tangential interpolation at the ROM level to reduce the size of the Hankel matrix. The proposed methods enable application of ERA for highly accurate online acoustic response prediction and reduce the offline computation cost of ROMs

Non-intrusive Balancing Transformation of Highly Stiff Systems with Lightly-damped Impulse Response

Balanced truncation (BT) is a model reduction method that utilizes a coordinate transformation to retain eigen-directions that are highly observable and reachable. To address realizability and scalability of BT applied to highly stiff and lightly-damped systems, a non-intrusive data-driven method is developed for balancing discrete-time systems via the eigensystem realization algorithm (ERA). The advantage of ERA for balancing transformation makes full-state outputs tractable. Further, ERA enables balancing despite stiffness, by eliminating computation of balancing modes and adjoint simulations. As a demonstrative example, we create balanced ROMs for a one-dimensional reactive flow with pressure forcing, where the stiffness introduced by the chemical source term is extreme (condition number $10^{13}$), preventing analytical implementation of BT. We investigate the performance of ROMs in prediction of dynamics with unseen forcing inputs and demonstrate stability and accuracy of balanced ROMs in truly predictive scenarios whereas without ERA, POD-Galerkin and Least-squares Petrov-Galerkin projections fail to represent the true dynamics. We show that after the initial transients under unit impulse forcing, the system undergoes lightly-damped oscillations, which magnifies the influence of sampling properties on predictive performance of the balanced ROMs. We propose an output domain decomposition approach and couple it with tangential interpolation to resolve sharp gradients at reduced computational costs

キノロン系抗菌剤 Ofloxacinにより誘発されたイヌ関節症の臨床病理学的研究

Veranda as one of the main elements of spatial hierarchy in the traditional Iranian architecture is responsible for providing visual and thermal comfort and energy saving, in the interior and to some extent exterior besides enhancing both the privacy and accessibility as a transition space all around the building. In the Solar Decathlon China 2013 (SDC 2013) house of Team Iran, the roof of veranda has been designed to be a functional part of the above goals. It is composed of several reflector pieces gathered in each veranda frame forming a traditional Iranian pattern. In the southern veranda roof, the reflector pieces are able to rotate on a daily basis, based on the amount of interior light intensity and optimal function of the water wall located in the southern facade. Through the current article this particular veranda design and its detailed mechanisms are thoroughly discussed. Lighting simulations have been performed for the interior of the house, with and without the veranda, in addition to covering different states through the day during distinct seasonal conditions for five specified geometrical layouts in the former case. Meanwhile, a data reduction procedure has been applied and validated by the obtained data in order to get an overall numerical interpretation of each case. The results confirm that the original width between the pattern elements in the traditional layout forms the optimum configuration and the rotation mechanism in the southern veranda roof further enhances the interior visual comfort

Atorvastatin versus Placebo in ICU Patients with COVID-19: Ninety-day Results of the INSPIRATION-S Trial

BACKGROUND: In the INSPIRATION-S trial, atorvastatin versus placebo was associated with a nonsignificant 16% reduction in 30-day composite of venous/arterial thrombosis or death in intensive care unit (ICU) patients with COVID-19. Thrombo-inflammatory response in coronavirus disease 2019 (COVID-19) may last beyond the first 30 days. METHODS: This article reports the effects of atorvastatin 20 mg daily versus placebo on 90-day clinical and functional outcomes from INSPIRATION-S, a double-blind multicenter randomized trial of adult ICU patients with COVID-19. The main outcome for this prespecified study was a composite of adjudicated venous/arterial thrombosis, treatment with extracorporeal membrane oxygenation (ECMO), or all-cause mortality. Functional status was assessed with the Post-COVID-19 Functional Scale. RESULTS: In the primary analysis, 587 patients were included (age: 57 [Q1-Q3: 45-68] years; 44% women). By 90-day follow-up, the main outcome occurred in 96 (33.1%) patients assigned to atorvastatin and 113 (38.0%) assigned to placebo (hazard ratio [HR]: 0.80, 95% confidence interval [CI]: 0.60-1.05, p = 0.11). Atorvastatin in patients who presented within 7 days of symptom onset was associated with reduced 90-day hazard for the main outcome (HR: 0.60, 95% CI: 0.42-0.86, p $_{interaction}$ = 0.02). Atorvastatin use was associated with improved 90-day functional status, although the upper bound CI crossed 1.0 (OR$_{ordinal}$: 0.64, 95% CI: 0.41-1.01, p = 0.05). CONCLUSION: Atorvastatin 20 mg compared with placebo did not significantly reduce the 90-day composite of death, treatment with ECMO, or venous/arterial thrombosis. However, the point estimates do not exclude a potential clinically meaningful treatment effect, especially among patients who presented within 7 days of symptom onset (NCT04486508)