15,285 research outputs found
A hierarchical approach to multi-project planning under uncertainty
We survey several viewpoints on the management of the planning complexity of multi-project organisations under uncertainty. A positioning framework is proposed to distinguish between different types of project-driven organisations, which is meant to aid project management in the choice between the various existing planning approaches. We discuss the current state of the art of hierarchical planning approaches both for traditional manufacturing and for project environments. We introduce a generic hierarchical project planning and control framework that serves to position planning methods for multi-project planning under uncertainty. We discuss multiple techniques for dealing with the uncertainty inherent to the different hierarchical stages in a multi-project organisation. In the last part of this paper we discuss two cases from practice and we relate these practical cases to the positioning framework that is put forward in the paper
Transverse instability of dunes
The simplest type of dune is the transverse one, which propagates with
invariant profile orthogonally to a fixed wind direction. Here we show
numerically and with a linear stability analysis that transverse dunes are
unstable with respect to along-axis perturbations in their profile and decay on
the bedrock into barchan dunes. Any forcing modulation amplifies exponentially
with growth rate determined by the dune turnover time. We estimate the distance
covered by a transverse dune before fully decaying into barchans and identify
the patterns produced by different types of perturbation.Comment: 4 pages, 3 figures; To appear in Physical Review Letter
Potential of Interplanetary Torques and Solar Modulation for Triggering Terrestrial Atmospheric and Lithospheric Events
The Sun is forced into an orbit around the barycenter of the solar system
because of the changing mass distribution of the planets. Solar-planetary-lunar
dynamic relationships may form a new basis for understanding and predicting
cyclic solar forcing functions on the Earth's climate.Comment: Invited Paper at the Fourth UN/ESA Workshop on Basic Space Science,
Cairo, Egypt, July 1994. 7 pages LaTeX. Accepted for publication in the
journal Earth, Moon, and Planet
A Concept for Attribute-Based Authorization on D-Grid Resources
In Germany's D-Grid project numerous Grid communities are working together to provide a common overarching Grid infrastructure. The major aims of D-Grid are the integration of existing Grid deployments and their interoperability. The challenge lies in the heterogeneity of the current implementations: three Grid middleware stacks and different Virtual Organization management approaches have to be embraced to achieve the intended goals. In this article we focus oil the implementation of an attribute-based authorization infrastructure that not only leverages the well-known VO attributes but also campus attributes managed by a Shibboleth federation
Geometric scaling in high-energy QCD at nonzero momentum transfer
We show how one can obtain geometric scaling properties from the
Balitsky-Kovchegov (BK) equation. We start by explaining how, this property
arises for the b-independent BK equation. We show that it is possible to extend
this model to the full BK equation including momentum transfer. The saturation
scale behaves like max(q,Q_T) where q is the momentum transfer and Q_T a
typical scale of the target.Comment: 4 pages, 2 figures. Talk given by G. Soyez at the "Rencontres de
Moriond", 12-19 March 2005, La Thuile, Ital
The Higgs Mechanism in Heterotic Orbifolds
We study spontaneous gauge symmetry breaking in the framework of orbifold
compactifcations of heterotic string theory. In particular we investigate the
electroweak symmetry breakdown via the Higgs mechanism. Such a breakdown can be
achieved by continuous Wilson lines. Exploiting the geometrical properties of
this scheme we develop a new technique which simplifies the analysis used in
previous discussions.Comment: 38 pages, 10 figure
Bloch oscillations of Bose-Einstein condensates: Quantum counterpart of dynamical instability
We study the Bloch dynamics of a quasi one-dimensional Bose-Einstein
condensate of cold atoms in a tilted optical lattice modeled by a Hamiltonian
of Bose-Hubbard type: The corresponding mean-field system described by a
discrete nonlinear Schr\"odinger equation can show a dynamical (or modulation)
instability due to chaotic dynamics and equipartition over the quasimomentum
modes. It is shown, that these phenomena are related to a depletion of the
Floquet-Bogoliubov states and a decoherence of the condensate in the
many-particle description. Three different types of dynamics are distinguished:
(i) decaying oscillations in the region of dynamical instability, and (ii)
persisting Bloch oscillations or (iii) periodic decay and revivals in the
region of stability.Comment: 12 pages, 14 figure
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