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#### Erscheinungsjahr

- 2000 (95) (entfernen)

#### Dokumenttyp

- Preprint (73)
- Wissenschaftlicher Artikel (12)
- Bericht (7)
- Diplomarbeit (1)
- Dissertation (1)
- Teil eines Periodikums (1)

#### Sprache

- Englisch (95) (entfernen)

#### Volltext vorhanden

- ja (95) (entfernen)

#### Schlagworte

- resonances (6)
- Quantum mechanics (5)
- lifetimes (5)
- Wannier-Stark systems (4)
- AG-RESY (3)
- HANDFLEX (3)
- branch and cut (3)
- facets (3)
- facility location (3)
- hub location (3)

#### Fachbereich / Organisatorische Einheit

In this paper we show how Metropolis Light Transport can be extended both in the underlying theoretical framework and the algorithmic implementation to incorporate volumetric scattering.
We present a generalization of the path integral formulation thathandles anisotropic scattering in non-homogeneous media. Based on this framework we introduce a new mutation strategy that is
specifically designed for participating media. It exploits the locality of light propagation by perturbing certain interaction points within the medium. To efficiently sample inhomogeneous media a new ray marching method has been developed that avoids aliasing artefacts and is significantly faster than stratified sampling. The resulting global illumination algorithm provides a physically correct simulation of light transport in the presence of participating media that includes effects such as volume caustics and multiple volume scattering. It is not restricted to certain classes of geometry and scattering models and has minimal memory requirements. Furthermore, it is unbiased and robust, in the sense that it produces satisfactory results for a wide range of input scenes and lighting situations within acceptable time bounds. In particular, we found that it is weil suited for complex scenes with many light sources.

For most applications the used transport service providers are predetermined during the development of the application. This makes it difficult to consider the application communication requirements and to exploit specific features of the network technology. Specialized protocols that are more efficient and offer a qualitative improved service are typically not supported by most applications because they are not commonly available. In this paper we propose a concept for the realization of protocol independent transport services. Only a transport service is predetermined during the development of the application and an appropriate transport service provider is dynamically selected at run time. This enables to exploit specialized protocols if possible, but standard protocols could still be used if necessary. The main focus of this paper is how a transport service could provide a new transport service provider transparently to existing applications. A prototype is presented that maps TCP/IP based applications to an ATM specific transport service provider which offers a reliable and unreliable transport service like TCP/IP.

The photon map provides a powerful tool for approximating the irradiance in global illumination computations independent from geometry. By presenting new importance sampling techniques, we dramatically improve the memory footprint of the photon map, simplify the caustic generation, and allow for a much faster sampling of direct illumination in complicated models as they arise in a production environment.

The quality of freeform surfaces is one of the major topics of CAD/CAM. Aesthetic and technical demands require the construction of high quality surfaces with strong shape conditions. Quality diminishing properties like dents or flat points have to be eliminated while approximation conditions must hold at the same time. Our approach combines quality and approximation criteria to a nonlinear multicriteria optimization problem and achieves an automatic approximation and fitting process.

Given a public transportation system represented by its stops and direct connections between stops, we consider two problems dealing with the prices for the customers: The fare problem in which subsets of stops are already aggregated to zones and "good" tariffs have to be found in the existing zone system. Closed form solutions for the fare problem are presented for three objective functions. In the zone problem the design of the zones is part of the problem. This problem is NP hard and we therefore propose three heuristics which prove to be very successful in the redesign of one of Germany's transportation systems

We examine the feasibility polyhedron of the uncapacitated hub location problem (UHL) with multiple allocation, which has applications in the fields of air passenger and cargo transportation, telecommunication and postal delivery services. In particular we determine the dimension and derive some classes of facets of this polyhedron. We develop some general rules about lifting facets from the uncapacitated facility location (UFL) for UHL and projecting facets from UHL to UFL. By applying these rules we get a new class of facets for UHL which dominates the inequalities in the original formulation. Thus we get a new formulation of UHL whose constraints are all facet–defining. We show its superior computational performance by benchmarking it on a well known data set.

Within this paper we review image distortion measures. A distortion measure is a criterion that assigns a "quality number" to an image. We distinguish between mathematical distortion measures and those distortion measures in-cooperating a priori knowledge about the imaging devices ( e.g. satellite images), image processing algorithms or the human physiology. We will consider representative examples of different kinds of distortion measures and are going to discuss them.

In this short note we prove some general results on semi-stable sheaves on P_2 and P_3 with arbitrary linear Hilbert polynomial. Using Beilinson's spectral sequence, we compute free resolutions for this class of semi-stable sheaves and deduce that the smooth moduli spaces M_{r m + s}(P_2) and M_{r m + r - s}(P_2) are birationally equivalent if r and s are coprime.

Abstract: This paper presents a solution to a problem from superanalysis about the existence of Hilbert-Banach superalgebras. Two main results are derived: 1) There exist Hilbert norms on some graded algebras (infinite-dimensional superalgebras included) with respect to which the multiplication is continuous. 2) Such norms cannot be chosen to be submultiplicative and equal to one on the unit of the algebra.