Nonlinear analysis of the buckling and vibration of a rotating elasticum

We investigate the static and dynamic behaviour of an elasticum which is clamped radially to the inside of a rotating ring and carries a mass at the free end. A nonlinear model for buckling and vibration of the structure in the plane of the ring is established and a subsequent Galerkin procedure leads to a system of two first order ODEs, accessible to a bifurcation and phase plane analysis. It will be shown that these results can only claim limited validity. Afterwards, more adequate results are obtained by a Poincaré-Lindstedt perturbation method. This approach is possible, since the linearized model equation can be solved analytically. Regarding the angular velocity of the ring as a bifurcation parameter, the analysis shows the existence of a supercritical bifurcation for any length of the elasticum. Finally, the case of out-of-plane buckling is shortly investigated, with the result that no buckling occurs for a sufficiently long elasticum.     

Satellite‐PCS channel simulation in mobile user environments using photogrammetry and Markov chains

In this paper, we present a system that models the land‐mobile satellite communication channel with a Markov chain approach supported by images of the mobile Earth station's (MES) environment. Our method employs a video camera with a fish‐eye lens capturing image sequences of the user environment from the position of the moving MES, image and signal processing algorithms to recognize propagation path states and extract their duration and transition probabilities, and modeling of the communication channel characteristics using the theory of Markov stochastic processes combined with statistical fade distributions appropriate for given path states. The results demonstrate that the procedure provides a full statistical characterization of the narrow‐band land‐mobile satellite propagation channel in several environments. This revised version was published online in June 2006 with corrections to the Cover Date.     

Praxis und Wissen – Aus der Industrie – Neues von der Montanuniversität – Personalnachrichten – Tagungsankündigungen – Neues von der ASMET – Hinweise auf Neuerscheinungen

BHM Verbandsnachrichten

Praxis und Wissen – Aus der Industrie – Neues von der Montanuniversit?t – Personalnachrichten – Tagungsankündigungen – Neues von der ASMET – Hinweise auf Neuerscheinungen     

Photooxidation von Linolsäuremethylester - Identifizierung eines Sensibilisators

Photooxidation of Methyl Linoleate - Identification of a Sensibilizer Methyl linoleate samples are oxidized when irradiated with fluorescence lamps of the daylight type much faster than in the dark. Model experiments with different additives gave the following results: Photooxidation is initiated by fatty acids having a conjugated oxodiene system. These compounds, after irradiation, act as start radicals in the autoxidation of methyl linoleate (type 1 photooxidation). Fatty acids having a conjugated triene system, which absorbs in the same region of UV light as the oxodiene compounds, do not act as sensibilizers. A light-induced decomposition of linoleic acid hydroperoxides did not occur under the experimental conditions chosen.