Search results for "bound"
showing 10 items of 2948 documents
Rotationally symmetric p -harmonic maps fromD2toS2
2013
We consider rotationally symmetric p-harmonic maps from the unit disk D2⊂R2 to the unit sphere S2⊂R3, subject to Dirichlet boundary conditions and with 1<p<∞. We show that the associated energy functional admits a unique minimizer which is of class C∞ in the interior and C1 up to the boundary. We also show that there exist infinitely many global solutions to the associated Euler–Lagrange equation and we completely characterize them.
Unsteady Separation for High Reynolds Numbers Navier-Stokes Solutions
2010
In this paper we compute the numerical solutions of Navier-Stokes equations in the case of the two dimensional disk impulsively started in a uniform back- ground flow. We shall solve the Navier-Stokes equations (for different Reynolds numbers ranging from 1.5 · 10^3 up to 10^5 ) with a fully spectral numerical scheme. We shall give a description of unsteady separation process in terms of large and small scale interactions acting over the flow. The beginning of these interactions will be linked to the topological change of the streamwise pressure gradient on the disk. Moreover we shall see how these stages of separation are related to the complex singularities of the solution. Infact the ana…
Urban Surface Energy Balance Models: Model Characteristics and Methodology for a Comparison Study
2009
Many urban surface energy balance models now exist. These vary in complexity from simple schemes that represent the city as a concrete slab, to those which incorporate detailed representations of momentum and energy fluxes distributed within the atmospheric boundary layer. While many of these schemes have been evaluated against observations, with some models even compared with the same data sets, such evaluations have not been undertaken in a controlled manner to enable direct comparison. For other types of climate model, for instance the Project for Intercomparison of Land-Surface Parameterization Schemes (PILPS) experiments (Henderson-Sellers et al., 1993), such controlled comparisons hav…
BIBO Stability Analysis for Delay Switched Systems with Nonlinear Perturbation
2013
Published version of a paper from the journal:Abstract and Applied Analysis. Also available from Hindawi:http://dx.doi.org/10.1155/2013/738653 The problem of bounded-input bounded-output ( BIBO) stability is investigated for a class of delay switched systems with mixed time-varying discrete and constant neutral delays and nonlinear perturbation. Based on the Lyapunov-Krasovskii functional theory, new BIBO stabilization criteria are established in terms of delay-dependent linear matrix inequalities. The numerical simulation is carried out to demonstrate the effectiveness of the results obtained in the paper.
Fuzzy Sliding Mode Controller Design Using Takagi-Sugeno Modelled Nonlinear Systems
2013
Published version of an article in the journal: Mathematical Problems in Engineering. Also available from the publisher at: http://dx.doi.org/10.1155/2013/734094 Open access Adaptive fuzzy sliding mode controller for a class of uncertain nonlinear systems is proposed in this paper. The unknown system dynamics and upper bounds of the minimum approximation errors are adaptively updated with stabilizing adaptive laws. The closed-loop system driven by the proposed controllers is shown to be stable with all the adaptation parameters being bounded. The performance and stability of the proposed control system are achieved analytically using the Lyapunov stability theory. Simulations show that the …
Stability of Flow with Viscous Dissipation in a Horizontal Porous Layer with an Open Boundary Having a Prescribed Temperature Gradient
2010
Published version of an article in the journal: Transport in Porous Media. The original publication is available at www.springerlink.com, http://dx.doi.org/10.1007/s11242-010-9588-6 A buoyancy-induced stationary flow with viscous dissipation in a horizontal porous layer is investigated. The lower boundary surface is impermeable and subject to a uniform heat flux. The upper open boundary has a prescribed, linearly varying, temperature distribution. The buoyancy-induced basic velocity profile is parallel and non-uniform. The linear stability of this basic solution is analysed numerically by solving the disturbance equations for oblique rolls arbitrarily oriented with respect to the basic velo…
Adaptive Tracking Control of Nonlinear Time-Varying Systems with Unknown Control Coefficients and Unknown Time-Varying Parameters
2019
This paper investigates the tracking control of a class of strict-feedback uncertain nonlinear systems in the presence of unknown signs of control coefficients and unknown time-varying parameters as well as unknown disturbances. A robust adaptive controller and a new decoupled backstepping approach to stability analysis are developed by constructing a new compensation scheme. By introducing a Nussbaum function and a new type of hyperbolic tangent function, the effects of unknown time-varying parameters and unknown control coefficients are effectively compensated. By using the decoupled backstepping technique, it is proved that under the proposed control, all closed-loop states are uniform u…
Semantiskā telpa un robežas attēlošana Žana Bodrijāra esejā "Amerika"
2015
Bakalaura darba tēma ir semantiskās telpas un robežas attēlošana Žana Bodrijāra esejā „Amerika”, kas balstās uz semiotiķa Jurija Lotmaņa sižeta teorijas. Lai sekmīgi veiktu izpēti, tika izvirzīts mērķis, izmeklēt un izanalizēt semantisko telpu tekstā, to attēlot un starp to noteikt robežu. Galvenā darba sastāvdaļa ir analīze, kas ar Lotmaņa teorijas palīdzību ļauj izanalizēt sižeta veidošanās pamatprincipus un trīs jomas, kuras nosaka semantisko lauku. Izanalizējot un aprakstot trīs jomas, ir iespējams noteikt robežu un tās nozīmi. Nosauktie elementi ir cieši saistīti, jo tie veido sižeta teorijas jēdzienu. Izstrādātā analīze ir parādījusi, ka dotajā esejā var noteikt pilsētas un tuksneša t…
From corona virus to corona crisis : the value of an analytical and geographical understanding of crisis
2020
Abstract The term ‘crisis’ is omnipresent. The current corona virus pandemic is perceived as the most recent example. However, the notion of crisis is increasingly deployed as a signifier of relevance, rather than as an analytical concept. Moreover, human geography has so far little contributed to the interdisciplinary crisis research field which is fixated on the temporal aspects of crisis but neglects its spatiality. Against this background, the first aim of the paper is to demonstrate the value of thinking about crisis analytically. Therefore, we introduce theoretical knowledge developed within a recently emerging literature on crisis management. Second, we demonstrate the relevance of i…
Reconstructing social spaces: The rhetoric of the public/ private split
1996
Abstract The article deals with the public/private distinction as a hidden spatialization that regulates the social. It looks at restructurations of the distinction; at changes and their political consequences in terms of ongoing rhetorical boundary work. The naming or coding of something as public or private is in itself a cultured process. The distinction is used in various meanings and within multiple discursive repertoires. What is named as public or private also varies in time and in space. Although variable and contextual, the coding always carries social value; it structures the societal positions of people. Furthermore, the coding also carries meanings that are not translatable. “Th…