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211.
B.H. Jørgensen J.N. Sørensen M. Brøns 《Theoretical and Computational Fluid Dynamics》2003,16(4):299-317
By applying Proper Orthogonal Decomposition (POD) one is
able to extract a limited amount of data which characterizes a flow of
interest. The modes resulting from the decomposition form a basis in
the phase space on which a Galerkin projection of the equations of
motion can be performed. By carrying out such a procedure one obtains
a low-dimensional model consisting of a reduced set of Ordinary
Differential Equations (ODEs) which models the original equations.
A technique called Sequential Proper Orthogonal Decomposition (SPOD)
is developed to perform decompositions suitable for low-dimensional
models. SPOD is capable of transforming data organized in
different sets separately while still producing orthogonal modes.
A low-dimensional model is constructed and used for analyzing
bifurcations occurring in the flow in the lid-driven cavity with
a rotating rod. The model allows one of the free parameters to appear in
the inhomogeneous boundary conditions without the addition of any
constraints. This is necessary because both the driving lid and the
rotating rod are controlled simultaneously. Apparently, the results
reported for this model are the first to be obtained for
a low-dimensional model based on projections on POD modes for more than
one free parameter.
Received 29 October 2001 and accepted 27 August 2002 Published online 13 January 2003
Communicated by P. Hall 相似文献
212.
213.
G. Huang S. Simoëns I. Vinkovic C. Le Ribault S. Dupont G. Bergametti 《Journal of Turbulence》2016,17(5):518-541
As opposed to the log-region, the roughness sublayer present above rough surfaces is still poorly understood due to the complex interaction between wakes developing behind roughness elements. To investigate the spatially averaged flow velocity in this region, a data-set has been collected from several direct numerical simulations and wind-tunnel experiments available in the literature. A generalised law-of-the-wall has been derived, applicable to a roughness sublayer present over regularly distributed roughness elements. The key roughness parameter of this new law is the effective height ?, which characterises the interaction between the roughness and the outer flow in a temporally and spatially averaged sense. A morphometric study reveals that ? is closely related to a new roughness density parameter, λ2, that accounts for the roughness element shape and the inter-element spacing. This allows ? to be a universal parameter on roughness characterisation. The derived values of the classical roughness length z0 of the log-law compare well with previous experimental data and geometrical model predictions. Finally, the main properties of the roughness sublayer such as its height are discussed using the geometrical and the roughness parameters proposed in the study. 相似文献
214.
Jānis Cīrulis 《Linear and Multilinear Algebra》2017,65(1):192-203
The diamond partial order has been first introduced for matrices, and then discussed also in the general context of *-regular rings. We extend this notion to Rickart rings, and state various properties of the diamond order living on the so-called strong Rickart rings. In particular, it is compared with the weak space preorder and the star order; also existence of certain meets and joins under diamond order is discussed. 相似文献
215.
Måns Ekelöf Erin K. McMurtrie Milad Nazari Suzanne D. Johanningsmeier David C. Muddiman 《Journal of the American Society for Mass Spectrometry》2017,28(2):370-375
High-salt samples present a challenge to mass spectrometry (MS) analysis, particularly when electrospray ionization (ESI) is used, requiring extensive sample preparation steps such as desalting, extraction, and purification. In this study, infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) coupled to a Q Exactive Plus mass spectrometer was used to directly analyze 50-μm thick slices of cucumber fermented and stored in 1 M sodium chloride brine. From the several hundred unique substances observed, three triterpenoid lipids produced by cucumbers, β-sitosterol, stigmasterol, and lupeol, were putatively identified based on exact mass and selected for structural analysis. The spatial distribution of the lipids were imaged, and the putative assignments were confirmed by tandem mass spectrometry performed directly on the same cucumber, demonstrating the capacity of the technique to deliver confident identifications from highly complex samples in molar concentrations of salt without the need for sample preparation. 相似文献
216.
Måns Andréasson Dr. Naresh Bhuma Dr. Nils Pemberton Dr. Erik Chorell 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(65):e202202020
This study aims to deepen the knowledge of the current state of rational G4-ligand design through the design and synthesis of a novel set of compounds based on indoles, quinolines, and benzofurans and their comparisons with well-known G4-ligands. This resulted in novel synthetic methods and G4-ligands that bind and stabilize G4 DNA with high selectivity. Furthermore, the study corroborates previous studies on the design of G4-ligands and adds deeper explanations to why a) macrocycles offer advantages in terms of G4-binding and -selectivity, b) molecular pre-organization is of key importance in the development of strong novel binders, c) an electron-deficient aromatic core is essential to engage in strong arene-arene interactions with the G4-surface, and d) aliphatic amines can strengthen interactions indirectly through changing the arene electrostatic nature of the compound. Finally, fundamental physicochemical properties of selected G4-binders are evaluated, underscoring the complexity of aligning the properties required for efficient G4 binding and stabilization with feasible pharmacokinetic properties. 相似文献
217.
Semra Tan Sylwia Walus Jöns Hilborn Torbjörn Gustafsson Daniel Brandell 《Electrochemistry communications》2010,12(11):1498-1500
This paper presents a novel thin-film electrolyte of a 2:1 blend of polyetheramine (glyceryl poly(oxypropylene)) and cross-linked oligomeric poly(propylene oxide) diacrylate with LiTFSI. The polyetheramine acts as a surfactant, and can thereby be applied as a conformal coating on complex surfaces—here demonstrated for porous LiFePO4 cathodes—making it useful for 3D-microbatteries. The poly(propylene oxide) diacrylate blends with the surfactant and is easily UV cross-linked, thereby ensuring good mechanical stability. Electrolytes, ~ 2 μm thick, were casted onto LiFePO4 cathodes and cycled against metallic lithium, displaying stable discharge capacities of ~ 8 mAh/g at room temperature and ~ 120 mAh/g at 60 °C. The electrolyte showed conductivities of 3.45 × 10? 6 and 5.80 × 10? 5 S cm? 1 at room temperature and 60 °C, respectively. 相似文献
218.
The photoconductivity spectrum of a single crystal of p type of CuGaTe2, has been examined at 300K and 77K. Structural details, which appeared on the high energy side of The band gap transition, are attributed to the valance band structure. Pronounced photoquenching is also observed on the high energy side and it is due to the recombination of holes with the ejected electrons from the inner 3d level of copper atom. Such a photoquenching effect has not been reported so for. 相似文献
219.
In this paper the following two questions are studied: (1) When does an idealI have the property that wheneverA is a family ofk sets there is aσ-ideal which extendsI and measures each element ofA? (2) When does an idealI have the property that whenA is a family ofk sets there is aσ-ideal which extendsI and measures at leastλ elements ofA? 相似文献
220.
O. Grāpis V. Tamužs N. Ohlson J. Andersons U. Vilks 《Mechanics of Composite Materials》1995,31(2):163-173
Conclusions Theoretical analysis and tests performed on rotors with composite shaft show that there is a sufficiently wide rotation stability region in the rotor parameter space despite comparatively high damping of a polymeric composite with respect to steel. Optimum parameters of the shaft (lay-up, thickness) and bearing (radial stiffness, damping) can be found within this region for each given rotor ensuring a low vibration level at critical frequencies.If rotor system parameters are far enough from the instability threshold, maximum vibration level is observed when rotor passes the first eigenfrequency zone. Further increase of rotation frequency leads to a rotor self-centering, and vibration level does not change passing the second eigenfrequency zone. The rotor response is not sensitive to small changes in rotor system parameters. If rotor system parameters are close to the instability threshold, vibration level at the second eigenfrequency dominates, and a small variation of bearing parameters causes significant changes in the vibration level.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 2, pp. 227–240, March–April, 1995. 相似文献