Reduced order models for control of fluids using the Eigensystem Realization Algorithm

In feedback flow control, one of the challenges is to develop mathematical models that describe the fluid physics relevant to the task at hand, while neglecting irrelevant details of the flow in order to remain computationally tractable. A number of techniques are presently used to develop such reduced-order models, such as proper orthogonal decomposition (POD), and approximate snapshot-based balanced truncation, also known as balanced POD. Each method has its strengths and weaknesses: for instance, POD models can behave unpredictably and perform poorly, but they can be computed directly from experimental data; approximate balanced truncation often produces vastly superior models to POD, but requires data from adjoint simulations, and thus cannot be applied to experimental data. In this paper, we show that using the Eigensystem Realization Algorithm (ERA) \citep{JuPa-85}, one can theoretically obtain exactly the same reduced order models as by balanced POD. Moreover, the models can be obtained directly from experimental data, without the use of adjoint information. The algorithm can also substantially improve computational efficiency when forming reduced-order models from simulation data. If adjoint information is available, then balanced POD has some advantages over ERA: for instance, it produces modes that are useful for multiple purposes, and the method has been generalized to unstable systems. We also present a modified ERA procedure that produces modes without adjoint information, but for this procedure, the resulting models are not balanced, and do not perform as well in examples. We present a detailed comparison of the methods, and illustrate them on an example of the flow past an inclined flat plate at a low Reynolds number.Comment: 22 pages, 7 figure

Amyloidogenic Regions and Interaction Surfaces Overlap in Globular Proteins Related to Conformational Diseases

Protein aggregation underlies a wide range of human disorders. The polypeptides involved in these pathologies might be intrinsically unstructured or display a defined 3D-structure. Little is known about how globular proteins aggregate into toxic assemblies under physiological conditions, where they display an initially folded conformation. Protein aggregation is, however, always initiated by the establishment of anomalous protein-protein interactions. Therefore, in the present work, we have explored the extent to which protein interaction surfaces and aggregation-prone regions overlap in globular proteins associated with conformational diseases. Computational analysis of the native complexes formed by these proteins shows that aggregation-prone regions do frequently overlap with protein interfaces. The spatial coincidence of interaction sites and aggregating regions suggests that the formation of functional complexes and the aggregation of their individual subunits might compete in the cell. Accordingly, single mutations affecting complex interface or stability usually result in the formation of toxic aggregates. It is suggested that the stabilization of existing interfaces in multimeric proteins or the formation of new complexes in monomeric polypeptides might become effective strategies to prevent disease-linked aggregation of globular proteins

Snapshot-based balanced truncation for linear time-periodic systems

Abstract We introduce an algorithm based on a method of snapshots for computing approximate balanced truncations for discrete-time, stable, linear time-periodic systems. By construction, this algorithm is applicable to very high-dimensional systems, even with very high-dimensional outputs (or, alternatively, very highdimensional inputs). An example is shown to validate the method

A serious pulmonary infection secondary to disseminated Strongyloidiasis in a patient with Nephrotic syndrome

We report a case involving infection with Strongyloides stercoralis found in the sputum of a 66-year-old male patient who had a medical history of nephrotic syndrome and was treated with methylprednisolone and monthly intravenous cyclophosphamide therapy 3 months previously. This patient presented with stubborn pulmonary symptoms and signs, which was the mechanical destruction caused by larval migration. We found strongyloides in his sputum that provided diagnostic proof

Investigation of the Mechanical Properties and Microstructure of the Co40NiCrMo Alloy Used for STACERs and Prepared by the CSPB Process and the Winding and Stabilization Method

The Co40NiCrMo alloy, used for STACERs fabricated by the CSPB (compositing stretch and press bending) process (cold forming) and the winding and stabilization (winding and heat treatment) method, was investigated with regard to its tensile property, residual stress, and microstructure. The Co40NiCrMo STACER prepared by the winding and stabilization method was strengthened with lower ductility (tensile strength/elongation: 1562 MPa/5%) compared to that prepared by CSPB (tensile strength/elongation: 1469 MPa/20.4%). The residual stress of the STACER prepared by winding and stabilization (τxy = −137 MPa) showed consistency with that obtained through CSPB (τxy = −131 MPa). Combined with the driving force and pointing accuracy performances, the optimum heat treatment parameters for the winding and stabilization method were determined as 520 °C + 4 h. The HABs in the winding and stabilization STACER (98.3%, of which 69.1% were Σ3 boundaries) were much higher than those in the CSPB STACER (34.6%, of which 19.2% were Σ3 boundaries), while deformation twins and h.c.p ε-platelet networks were present in the CSPB STACER, and many more annealing twins appeared in the winding and stabilization STACER. It was concluded that the strengthening mechanism in the CSPB STACER is the combined action of deformation twins and h.c.p ε-platelet networks, while for the winding and stabilization STACER, annealing twins play the dominant role

Application of WOA–SVR in Seed Vigor of High-Voltage Electric Field Treatment on Aged Cotton (<i>Gossypium</i> spp.) Seeds

When seeds are treated with a high-voltage electric field (HVEF) to improve seed vigor, due to the large differences in the biological electromagnetic effects on different types of seeds, the methods of variance analysis and regression analysis based on data statistics are generally used to construct the optimal electric field dose prediction model; however, the generalization performance of the prediction model tends to be poor. To solve this problem, the electric intensity, frequency and treatment time were taken as the input variables for hybrid support vector regression (SVR) analysis to establish the prediction model of the seed comprehensive germination index. The whale optimization algorithm (WOA) was used to optimize the kernel parameters of the SVR. The optimized hybrid WOA–SVR model predicted the optimal comprehensive germination index of aged cotton (Gossypium spp.) seeds to be 329, the optimal HVEF dosage was 3.64 kV/cm × 99 s, and the frequency was 1.4 Hz. The aged cotton seeds were treated with the optimal HVEF and the germination test was carried out. Compared with the check (CK), the comprehensive germination index of seeds increased by 48%. The research results provided a new method and new idea for the optimal design of parameters for seed treatment with HVEF

Effects of the shape distribution of aerosol particles on their volumetric scattering properties and the radiative transfer through the atmosphere that includes polarization

International audienc