Search results for "conditions"
showing 10 items of 891 documents
Reactions of Alkenes and Alkynes with an Acyclic Silylene and Heavier Tetrylenes under Ambient Conditions
2014
Cycloaddition reactions of the acyclic silylene Si(SAriPr4)2 (AriPr4 = C6H3-2,6(C6H3-2,6-iPr2)2) with a variety of alkenes and alkynes were investigated. Its reactions with the alkynes phenylacetylene and diphenylacetylene and the diene 2,3-dimethyl-1,3-butadiene yielded silacycles (AriPr4S)2tiebar above startSi(CH═tiebar above endCPh) (1), (AriPr4S)2tiebar above startSi(PhC═tiebar above endCPh) (2), and (AriPr4S)2tiebar above startSiCH2CMeCMetiebar above endCH2 (3) at ambient temperature. The compounds were characterized by X-ray crystallography, 1H, 13C, and 29Si NMR spectroscopy, and IR spectroscopy. No reaction was observed with more substituted alkenes such as propene, (Z)-2-butene, te…
Flow resistance law under equilibrium bed-load transport conditions
2018
Abstract The uniform flow resistance equation, in the form due to Manning or Darcy-Weisbach, is often applied to determine the stage-discharge relationship of a river cross-section. The application of this equation, namely the slope-area method, allows to indirectly measure by water level readings the corresponding river discharge. In this paper, a recently deduced flow resistance equation for open channel flow was tested during conditions of equilibrium bed-load transport. First the flow resistance equation was determined by dimensional analysis and applying the condition of incomplete self-similarity for the flow velocity profile. Then the analysis was developed by the following steps: (i…
Infinite games and chain conditions
2015
We apply the theory of infinite two-person games to two well-known problems in topology: Suslin's Problem and Arhangel'skii's problem on $G_\delta$ covers of compact spaces. More specifically, we prove results of which the following two are special cases: 1) every linearly ordered topological space satisfying the game-theoretic version of the countable chain condition is separable and 2) in every compact space satisfying the game-theoretic version of the weak Lindel\"of property, every cover by $G_\delta$ sets has a continuum-sized subcollection whose union is $G_\delta$-dense.
Homotopy limits for 2-categories
2008
AbstractWe study homotopy limits for 2-categories using the theory of Quillen model categories. In order to do so, we establish the existence of projective and injective model structures on diagram 2-categories. Using these results, we describe the homotopical behaviour not only of conical limits but also of weighted limits. Finally, pseudo-limits are related to homotopy limits.
Energy localization in a nonlinear discrete system
1996
International audience; We show that, in the weak amplitude and slow time limits, the discrete equations describing the dynamics of a one-dimensional lattice can be reduced to a modified Ablowitz-Ladik equation. The stability of a continuous wave solution is then investigated without and with periodic boundary conditions; Energy localization via modulational instability is predicted. Our numerical simulations, performed on a cyclic system of six oscillators, agree with our theoretical predictions.
Method of Lines and Finite Difference Schemes with Exact Spectrum for Solving Some Linear Problems of Mathematical Physics
2013
In this paper linear initial-boundary-value problems of mathematical physics with different type boundary conditions BCs and periodic boundary conditions PBCs are studied. The finite difference scheme FDS and the finite difference scheme with exact spectrum FDSES are used for the space discretization. The solution in the time is obtained analytically and numerically, using the method of lines and continuous and discrete Fourier methods.
Optimal Usage of Multiple Network Connections
2008
In the future mobile networks, a mobile terminal is able to select the best suitable network for each data transmission. The selection of a network connection to be used has been under a lot of study. In this paper, we consider a more extensive case in which we do not select a network connection but use several network connections simultaneously to transfer data. When data is transferred using multiple network connections, a network connection has to be selected for each component of the data. We have modelled this problem as a multiobjective optimization problem and developed a heuristic to solve the problem fast in a static network environment. In this paper, we discuss solving the proble…
Short chaotic strings and their behaviour in the scaling region
2008
Coupled map lattices are a paradigm of higher-dimensional dynamical systems exhibiting spatio-temporal chaos. A special case of non-hyperbolic maps are one-dimensional map lattices of coupled Chebyshev maps with periodic boundary conditions, called chaotic strings. In this short note we show that the fine structure of the self energy of this chaotic string in the scaling region (i.e. for very small coupling) is retained if we reduce the length of the string to three lattice points.
Chapter 4</br>Will our children have the chance to do research on today’s digital books?
2016
In this chapter, I will first position my considerations about the sustainability of ebooks for future research in the context of book history; moreover, I will introduce basic concepts of (migration and emulation) as well as challenges to the long-term preservation of digital data in greater generality. After that and taking current research on past (printed) books as an analogy, I shall try to outline which kinds of (digital) material will be indispensable in the future to do research on today's digital book production: published digital materials and unique (digital) artefacts. Finally, I shall present the results of my exemplary studies to find out which precautions for the future avail…
Fiscal Policy Responsiveness, Persistence and Discretion
2008
This paper analyzes the different characteristics of fiscal policy using a two-step estimation procedure. First, we decompose both government spending and government revenue into three components: responsiveness, persistence and discretion. Second, we assess the determinants of these characteristics. Using data from 132 countries, our results show that fiscal policy is more persistent than responsive to economic conditions, which implies that the authorities may have less leeway in the short-run notably to curb spending behavior. In addition, countries characterized by greater fiscal persistence have less discretion and responsiveness. Finally, macroeconomic, institutional and geographic va…