University of Mannheim

About: University of Mannheim is a education organization based out in Mannheim, Germany. It is known for research contribution in the topics: Population & European union. The organization has 4448 authors who have published 12918 publications receiving 446557 citations. The organization is also known as: Uni Mannheim & UMA.

Relations Between Regularization and Diffusion Filtering

Abstract: Regularization may be regarded as diffusion filtering with an implicit time discretization where one single step is used. Thus, iterated regularization with small regularization parameters approximates a diffusion process. The goal of this paper is to analyse relations between noniterated and iterated regularization and diffusion filtering in image processing. In the linear regularization framework, we show that with iterated Tikhonov regularization noise can be better handled than with noniterated. In the nonlinear framework, two filtering strategies are considered: the total variation regularization technique and the diffusion filter technique of Perona and Malik. It is shown that the Perona-Malik equation decreases the total variation during its evolution. While noniterated and iterated total variation regularization is well-posed, one cannot expect to find a minimizing sequence which converges to a minimizer of the corresponding energy functional for the Perona–Malik filter. To overcome this shortcoming, a novel regularization technique of the Perona–Malik process is presented that allows to construct a weakly lower semi-continuous energy functional. In analogy to recently derived results for a well-posed class of regularized Perona–Malik filters, we introduce Lyapunov functionals and convergence results for regularization methods. Experiments on real-world images illustrate that iterated linear regularization performs better than noniterated, while no significant differences between noniterated and iterated total variation regularization have been observed.

Price Competition and Product Differentiation when Consumers Care for the Environment

Abstract: Increasing environmental awareness may affect the pleasure of consuming a good for which an environmental friendly substitute is available. When deciding to buy differentiated products, a compromise is sometimes made between preferred characteristics of the good and its environmental properties. In this paper we investigate the market implication of product differentiation when customers are concerned about environmental aspects of the good. We use the spatial duopoly model to determine how environmental concern affects prices, product characteristics and market shares of the competing firms. Our analysis is based on a two-stage game where at the first stage each firm chooses the characteristic of its product. At the second stage each firm chooses its price. The unique equilibrium prices and market shares are affected by consumer awareness of the environment and by the higher costs for producing those goods. As for the Nash equilibria in the characteristics we find three equilibria depending on the parameter constellation. In order to find out whether the market functions in an optimal way we determined the choice of environmental characteristics by a welfare maximizing authority. The result of this analysis is that characteristics differ under private decision making and social one. It can be shown, however, that it is possible to choose environmental policy instruments in order to stimulate private firms to produce the social optimal qualities.

Outcome after lumbar sequestrectomy compared with microdiscectomy: a prospective randomized study.

Abstract: Object. Microdiscectomy currently constitutes the standard treatment for herniated lumbar discs. Although limiting surgery to excision of fragments has occasionally been suggested, prospective data are lacking. Therefore, the objective of this study was to compare early outcome and recurrence rates after sequestrectomy and microdiscectomy. Methods. Eighty-four consecutive patients 60 years of age or younger who harbored free, subligamentary, or transanular herniated lumbar discs refractory to conservative treatment were randomized to one of two treatment groups. Intraoperative parameters and findings were documented as well as pre- and postoperative symptoms such as pain, Patient Satisfaction Index (PSI), Prolo Scale score, and Short Form (SF)—36 subscale results. Follow up of at least 12 months was available in 73 patients (87%). Preoperative intergroup symptoms did not differ significantly. Surgery was significantly shorter in the sequestrectomy-treated group. Overall, low-back pain and sciatica were dr...