Der Enzyklopädist der Technischen Mechanik des 19. Jahrhunderts – Zum 200. Geburtstag von Julius Weisbach (1806–1871)

Encyclopaedist of 19th century applied mechanics – Commemorating Julius Weisbach's 200th birthday. With his two‐volume “Lehrbuch der Ingenieur‐ und Maschinen‐Mechanik” (Textbook of engineering and machine mechanics) (1845–1887), his handbook “Der Ingenieur” (The Engineer) und the journal “Der Civilingenieur” (The Civil Engineer), Julius Weisbach (1806–1871) created an image of applied mechanics reflecting the state of the industrial revolution in Germany in content and form. For the first time, he subjected the whole ‘artefact world’ of the contemporary engineer to a simple and comprehensible analysis based on applied mechanics. With his encyclopaedic publication system Weisbach succeeded in providing a valid representation of the historical/logical middle of the discipline formation period of applied mechanics (1825–1900).     

Hydraulischer Grundbruch und Versagen des Erdwiderlagers von Baugrubenwänden

Failure by heave and failure of the earth support of excavation walls. The present article deals with the phenomenon of heave at the earth support of excavation walls. It is restricted to a homogeneous subsoil in the area of the bottom of the excavation. Starting with some questions, which result from the required verifications of limit states, two mechanical models are described, which differ on the stability of the skeleton of grains. The possible failure mechanisms for hydraulically stressed earth supports of excavation walls are discussed. With two exemplary deep excavations, one of it wide, the other narrow, the respective verifications of limit states in the classical form as well as on basis of Finite Element calculations are carried out. Finally the results are discussed and some conclusions are drawn from it. Also requirements for verifications of limit states on basis of FEM calculations are formulated.     

Condition Evolution in Bridge Management Systems and Corrosion-Induced Deterioration

Condition assessment in the Swiss bridge management system (KUBA-MS) is performed on the element level. Five condition states are defined based on visual appearance. In order to forecast the condition states of any given element at any given time a relationship must be established between the element age and its condition state. This relationship, which describes the condition evolution, can be obtained empirically from statistical analysis of pairs of consecutive condition assessments (inspections). Markov chains are used in KUBA-MS to represent condition evolution and the transition probabilities are determined using regression analysis of pairs of inspections. Unfortunately there are almost no inspection data for the worst and second worst condition states. The forecasts made using Markov chains are therefore not always reliable. In this paper an alternative approach is suggested, which takes into consideration the physical phenomena underlying element deterioration. This alternative approach is applied to chloride-induced corrosion of steel reinforcement, by far the most common deterioration mechanism in Switzerland. The chloride-induced corrosion is modeled mathematically and numerical simulations of the condition evolution for different values of model parameters are performed. The simulation results have been mapped to condition states as defined in KUBA-MS and Markov transition matrices have been calibrated to fit simulation results.     

Characterization of the ozone zero phenomenon by infrared spectroscopy

The presence of a small amount of nitrogen in the feed gas is necessary to generate ozone efficiently out of oxygen. Operating an ozone generator with ultra-pure oxygen for extended periods results in highly deteriorated ozone generation efficiency. In extreme cases, when the nitrogen levels in the feed gas are in the lower ppm range, the efficiency of the ozone generation process even drops to zero. In this article, we present our results concerning the correlation between the N₂O₅ concentration in the off-gas and the ozone generation efficiency. After the ozone generator is run for a well-defined amount of time with an oxygen–nitrogen mixture, the N₂ supply is shut off, and the behavior of the system is monitored by near-infrared spectroscopy. Different surface materials lead to different temporal behavior of both the nitrogen oxide levels and the ozone concentration after shutting down the nitrogen supply. The measurements show a good correlation between the evolution of ozone generation efficiency and the changes of the N₂O₅ concentration in the off-gas.     

Intelligent framework for radio access network design

Wireless Networks - The evolution of 5G networks over the last few years has introduced a variety of technologies for more efficient radio access networks (RANs), which end up in ultra-dense...