Search results for "Condition"
showing 10 items of 2530 documents
The initial boundary value problem for free-evolution formulations of General Relativity
2017
We consider the initial boundary value problem for free-evolution formulations of general relativity coupled to a parametrized family of coordinate conditions that includes both the moving puncture and harmonic gauges. We concentrate primarily on boundaries that are geometrically determined by the outermost normal observer to spacelike slices of the foliation. We present high-order-derivative boundary conditions for the gauge, constraint violating and gravitational wave degrees of freedom of the formulation. Second order derivative boundary conditions are presented in terms of the conformal variables used in numerical relativity simulations. Using Kreiss-Agranovich-Metivier theory we demons…
Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory
2013
The Pierre Auger Observatory in Malargue, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18) eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, lo…
On vibrating thin membranes with mass concentrated near the boundary: an asymptotic analysis
2018
We consider the spectral problem \begin{equation*} \left\{\begin{array}{ll} -\Delta u_{\varepsilon}=\lambda(\varepsilon)\rho_{\varepsilon}u_{\varepsilon} & {\rm in}\ \Omega\\ \frac{\partial u_{\varepsilon}}{\partial\nu}=0 & {\rm on}\ \partial\Omega \end{array}\right. \end{equation*} in a smooth bounded domain $\Omega$ of $\mathbb R^2$. The factor $\rho_{\varepsilon}$ which appears in the first equation plays the role of a mass density and it is equal to a constant of order $\varepsilon^{-1}$ in an $\varepsilon$-neighborhood of the boundary and to a constant of order $\varepsilon$ in the rest of $\Omega$. We study the asymptotic behavior of the eigenvalues $\lambda(\varepsilon)$ and the eige…
Multiplicity of Solutions for Second Order Two-Point Boundary Value Problems with Asymptotically Asymmetric Nonlinearities at Resonance
2007
Abstract Estimations of the number of solutions are given for various resonant cases of the boundary value problem 𝑥″ + 𝑔(𝑡, 𝑥) = 𝑓(𝑡, 𝑥, 𝑥′), 𝑥(𝑎) cos α – 𝑥′(𝑎) sin α = 0, 𝑥(𝑏) cos β – 𝑥′(𝑏) sin β = 0, where 𝑔(𝑡, 𝑥) is an asymptotically linear nonlinearity, and 𝑓 is a sublinear one. We assume that there exists at least one solution to the BVP.
What Flow Conditions are Conducive to Banner Cloud Formation?
2016
Abstract Banner clouds are clouds that are attached to the leeward slope of a steep mountain. Their formation is essentially due to strong Lagrangian uplift of air in the lee of the mountain. However, little is known about the flow regime in which banner clouds can be expected to occur. The present study addresses this question through numerical simulations of flow past idealized orography. Systematic sets of simulations are carried out exploring the parameter space spanned by two dimensionless numbers, which represent the aspect ratio of the mountain and the stratification of the flow. The simulations include both two-dimensional flow past two-dimensional orography and three-dimensional fl…
Design, construction and commissioning of the Braunschweig Icing Wind Tunnel
2018
Beyond its physical importance in both fundamental and climate research, atmospheric icing is considered as a severe operational condition in many engineering applications like aviation, electrical power transmission and wind-energy production. To reproduce such icing conditions in a laboratory environment, icing wind tunnels are frequently used. In this paper, a comprehensive overview on the design, construction and commissioning of the Braunschweig Icing Wind Tunnel is given. The tunnel features a test section of 0.5 m × 0.5 m with peak velocities of up to 40 m s−1. The static air temperature ranges from −25 to +30 °C. Supercooled droplet icing with liquid water contents up to 3 g m−3 c…
A reexamination of the equilibrium conditions in the theory of water drop nucleation
1975
The thermodynamic equations necessary to describe the conditions for equilibrium between a highly curved surface of a liquid and its vapour are re-examined. The complete equilibrium behaviour is reduced to one single differential equation for each component in an arbitrary c -component system. It is shown that this general formulation can be specialized to describe the conditions for equilibrium between water vapour and a pure water drop, the drop carrying an electric charge, containing a water soluble substance and/or containing a water insoluble nucleus. In the light of the present formulation, some incorrect physical statements of treatments by various authors reported in literature are …
Boghossian's Reductio of Compatibilism
1998
Según Boghossian, la compatibilidad entre el externismo respecto del contenido y el autoconocimiento implica el absurdo según el cual es posible conocer a priori verdades substantivas sobre el mundo, como que existe agua. El argumento de Boghossian descansa crucialmente en dos supuestos: en primer lugar, que el carácter composicional o atómico son propiedades internas de los conceptos; en segundo lugar, que el externalismo no puede dar cuenta de conceptos atómicos con extensión vacía. Ambos supuestos se ponen en cuestión en este artículo. Por una parte, el externismo puede concebir plausiblemente el carácter composicional o atómico de los conceptos como dependiente de la naturaleza real de …
Institutional Autonomy and the Attractiveness of the European Higher Education Area – Facts or Tokenistic Discourse?
2012
In the discourse of the Bologna Process, the notion of competitiveness as the focal goal of Bologna Process, and university autonomy as one of its founding principles are consistently linked. Autonomy is framed as a precondition of competitiveness, while competitiveness is framed in terms of attractiveness of European higher education and higher education institutions. This paper examines their relationship, discussing whether there is ground for the repeated policy argument of their going hand in hand. Do the more attractive countries have higher autonomy, are the countries with higher autonomy more attractive? Or are these phenomena linked only in the simplified arguments of the policy di…
Variation in Great Tit Nest Mass and Composition and Its Breeding Consequences: A Comparative Study in four Mediterranean Habitats
2013
Bird nests are structures whose properties affect breeding performance. Thus, the vast majority of bird species build their own characteristic nests, selecting appropriate materials to do so. However, in habitats where the availability of "ideal" materials is low, some ability to use alternative ones would be necessary, even at the cost of having breeding success reduced. The Great Tit (Parus major) breeds under widely different environmental conditions. Its nests are althought to be composed mainly of moss, although very few studies have quantified nest composition. Our target here was describing Great Tit nest mass and composition in four different Mediterranean habitats, and exploring th…