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611.
Dirac structures appear naturally in the study of certain classes of physical models described by partial differential equations and they can be regarded as the underlying power conserving structures. We study these structures and their properties from an operator-theoretic point of view. In particular, we find necessary and sufficient conditions for the composition of two Dirac structures to be a Dirac structure and we show that they can be seen as Lagrangian (hyper-maximal neutral) subspaces of Kre?n spaces. Moreover, special emphasis is laid on Dirac structures associated with operator colligations. It turns out that this class of Dirac structures is linked to boundary triplets and that this class is closed under composition. 相似文献
612.
We introduce a new class of linear systems, the L
p
-well-posed state/signal systems in continuous time, we establish the foundations of their theory and we develop some tools
for their study. The principal feature of a state/signal system is that the external signals of the system are not a priori
divided into inputs and outputs. We relate state/signal systems to the better-known class of well-posed input/state/output
systems, showing that state/signal systems are more flexible than input/state/output systems but still have enough structure
to provide a meaningful theory. We also give some examples which point to possibilities for further study. 相似文献
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We present our simulation results for the benchmark problem of the flow past a rudimentary landing gear using a General Galerkin FEM, also referred to as adaptive DNS/LES. In General Galerkin, no explicit subgrid model is used; instead, the computational mesh is adaptively refined with respect to an a posteriori error estimate of a quantity of interest in the computation, in this case, the drag force on the rudimentary landing gear. Turbulent boundary layers are modeled using a simple wall‐layer model with the shear stress at walls proportional to the skin friction, which here is assumed to be small and, therefore, can be approximated by zero skin friction. We compare our results with experimental data and other state of the art computations, where we find good agreement in sound pressure levels, surface velocities, and flow separation. We also compare with detailed surface pressure experimental data where we find largely good agreement, apart from some local differences for which we discuss possible explanations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
615.
Characterization of a non‐approved selective androgen receptor modulator drug candidate sold via the Internet and identification of in vitro generated phase‐I metabolites for human sports drug testing
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Jodi Kraus Rupal Gupta Manman Lu Angela M. Gronenborn Mikael Akke Tatyana Polenova 《Chemphyschem》2020,21(13):1436-1443
Chemical shift tensors obtained from solid-state NMR spectroscopy are very sensitive reporters of structure and dynamics in proteins. While accurate 13C and 15N chemical shift tensors are accessible by magic angle spinning (MAS) NMR, their quantum mechanical calculations remain challenging, particularly for 15N atoms. Here we compare experimentally determined backbone 13Cα and 15NH chemical shift tensors by MAS NMR with hybrid quantum mechanics/molecular mechanics/molecular dynamics (MD-QM/MM) calculations for the carbohydrate-binding domain of galectin-3. Excellent agreement between experimental and computed 15NH chemical shift anisotropy values was obtained using the Amber ff15ipq force field when solvent dynamics was taken into account in the calculation. Our results establish important benchmark conditions for improving the accuracy of chemical shift calculations in proteins and may aid in the validation of protein structure models derived by MAS NMR. 相似文献
620.
Helium (He) is present in fusion reactor wall materials, and its effect on radiation damage must be taken into account. The effect of He on displacement cascades in tungsten (W) has been studied using molecular dynamics simulations. Three different W–W potentials were compared and found to differ, especially for the clustering of the vacancies formed in the cascades. While there are differences in the amounts of damage depending on the potential, the overall effect of He in interstitial positions was to increase the amount of damage, while He in substitutional positions reduces it, due to the effect He has on the recombination of tungsten interstititals. 相似文献