1,721,174 research outputs found
Analysis of critical situations in the evaluation of human exposure to magnetic fields with complex waveforms
No full textIn-field assessment of bridge pier scour by means of Fiber Bragg Gratings: System and algorithms
Full text linkBLESS (Bed LEvel Seeking System) is a sedimeter that measures riverbed level around bridge pier in water. It is based on Fiber Bragg Gratings and the working principle is based on the measurement of the different heat dissipation behaviour in the saturated soil compared to the flowing water. It is an innovative part of a complex monitoring system installed on a road bridge over the Po river (Italy). After two years of data storage, a comparison of two different methods to detect the riverbed level can be performed. One of them showed results in satisfactory agreement with those provided by a traditional reference device, i.e., an echo sounder. Furthermore, coupling the two different proposed bed level estimation methods allows deriving significant information about the health status of the sedimeter. The device is reliable enough to operate and survive in very harsh environments and it is ready for further engineering applications
P. Crotti, G. Pignat, A.M. Rachoud-Schneider (dir.) : Premiers hommes dans les Alpes, de 50 000 à 5 000 avant Jésus-Christ.
No full textMorel Alain. P. Crotti, G. Pignat, A.M. Rachoud-Schneider (dir.) : Premiers hommes dans les Alpes, de 50 000 à 5 000 avant Jésus-Christ.. In: Revue de géographie alpine, tome 90, n°3, 2002. p. 112
Scour at river bridge piers: real-time vulnerability assessment through the continuous monitoring of a bridge over the river Po, Italy
No full textBridge failures are not uncommon during floods. Therefore, the assessment of bridge vulnerability is crucial to help a bridge's administration take the best decisions during emergencies (i.e. closing the bridge). The first step to achieve this is to implement a monitoring system providing needed information to develop scenarios based on administration response time. The proposed system seeks a real-time evaluation of the loads acting on the bridge. Wind and water contributions, debris accumulation upstream of piers and river bed level are evaluated by specific devices. The most difficult measurement is the identification of the riverbed position in close proximity to piers. Scour model predictions are still far from robust and accurate and no standard devices are available to measure it. Unfortunately, the main reason for bridge failure is scour around bridge piers, called local scour. A monitoring system was developed for this purpose and installed on a critical bridge over the river Po in Italy, as a result of the cooperation between the Politecnico di Milano and the Province of Mantova. The aim was to measure the main parameters for a proper evaluation of the bridge's vulnerability. The paper's focus is twofold: to show long-term data and all the phases needed to assess bridge safety. The first aspect, not so common in the literature, is useful to understand the temporal evolution of the environment around the bridge. The second one provides a roadmap for risk assessment and management decisions relying on the widely available database. With regard to this second topic, another paper describing the overall strategy has already been published. The main focus here is on potential implementation, with an emphasis on the available data
P. Crotti, G. Pignat, A.M. Rachoud-Schneider (dir.) : Premiers hommes dans les Alpes, de 50 000 à 5 000 avant Jésus-Christ.
No full textMorel Alain. P. Crotti, G. Pignat, A.M. Rachoud-Schneider (dir.) : Premiers hommes dans les Alpes, de 50 000 à 5 000 avant Jésus-Christ.. In: Revue de géographie alpine, tome 90, n°3, 2002. p. 112
Impact of DC Transient Disturbances on Harmonic Performance of Voltage Transformers for AC Railway Applications
Full text linkThis paper analyzes the impact of typical DC transient events occurring in railway grids on the frequency performance of instrument transformers (ITs) installed onboard trains and in AC substations for power quality (PQ) applications. PQ monitoring in railway systems is an issue of great interest because it plays a key role in the improvement of energy efficiency. The measurement chain for the PQ measurements, at 15 kV at 16.7 Hz and 25 kV at 50/60 Hz, commonly includes ITs to scale the voltage to levels fitting the input of the measurement units. Nevertheless, the behavior of ITs in the presence of PQ phenomena represents an open issue from a normative point of view, even for those installed in conventional AC power supply systems. In this context, the paper presents a possible definition of DC transient disturbances test waveforms, a measurement procedure, and a setup to assess the impact of these disturbances on the harmonic performances of ITs for railway systems. Preliminary experimental tests carried out on two commercial ITs under wide ranges of variation for the amplitude and the time duration of DC disturbances show that, in some cases, the error introduced in harmonic measurements can exceed 100%
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