Search results for "Bridge"
showing 10 items of 355 documents
The (micro) processes of integration as dialectic of structure and agency : the case of seconded national experts within the European Commission
2008
Masteroppgave i offentlig politikk og ledelse - Universitetet i Agder 2008 Micro-processes of integration – i.e. how agents develop identities, properties and decision-making behaviours preferred by a particular institution – have been a topic of significant scholarly debate. Most previous work builds on one underlying theoretical framework and thereby excludes (potentially important) elements lying outside it. My thesis attempts to contribute to the ongoing debate by developing a more holistic understanding of these processes, based on the dialectics of structure and agency and thereby positions actors’ decision-making behaviour on a continuum between ‘structural idiocy’ and ‘structural en…
Intervention strategies for the enhancement of the Peruvian route of the Inca royal path Qhapaq Ñan
2023
Qhapaq Ñan, a UNESCO World Heritage Site, was a complex administrative communication and transport system that connected the immense territory of the Inca empire for over 30 thousand km, intercepting sites of great historical and cultural interest today, first of all the Sanctuary of Machu Picchu. The consequences of climate change and the high tourist presence, which is mostly concentrated in Machu Picchu, are seriously jeopardizing the survival of this precious asset. The heavy rains that hit the monuments produce dangerous infiltrations of water between the masonry structures, compromising their stability; the transit of people along the paths and stairways erodes the rock and the soil. …
Focal adhesions are hotspots for keratin filament precursor formation
2006
Recent studies showed that keratin filament (KF) formation originates primarily from sites close to the actin-rich cell cortex. To further characterize these sites, we performed multicolor fluorescence imaging of living cells and found drastically increased KF assembly in regions of elevated actin turnover, i.e., in lamellipodia. Abundant KF precursors (KFPs) appeared within these areas at the distal tips of actin stress fibers, moving alongside the stress fibers until their integration into the peripheral KF network. The earliest KFPs were detected next to actin-anchoring focal adhesions (FAs) and were only seen after the establishment of FAs in emerging lamellipodia. Tight spatiotemporal …
Stressing Sequence for Hanger Replacement of Tied-Arch Bridges with Rigid Bars
2022
The construction of bridges with suspenders, such as cable-stayed or tied-arch bridges, needs deep study of the prestressing forces to be applied to stays or hangers in all stages, depending on the construction technique adopted. In these cases, the main issue is the determination of the initial forces and optimization of the prestressing system in terms of stressing values and sequence. When the bridge is already built and suspenders have to be replaced for maintenance, a different problem has to be faced by the engineer, because the sequence of replacements and the values of the axial stresses depend very much on the service conditions of the bridge and on its historical evolution from co…
Mathematical formulation of pulse amplitude modulation selective harmonic elimination in multilevel three phase inverters
2022
In this paper multilevel cascaded H-bridges (CHB) three phase inverters with 2n dc sources, n=1,2,3,... are considered and a mathematical formulation providing both 2n switching angles and dc voltage source to eliminate n+1 harmonics and their respective multiple from their output voltage waveform, is proposed. The computed angles don't depend on modulation index and the source voltages linearly vary with it. The proposed procedure finds the solution through an analytical formula that avoids to solve transcendental systems and presents very low computational cost. A lot of low order harmonics are eliminated, returning a very low total harmonic distortion (THD). Particularly for 9-level conf…
DC Bias Abatement in Dual Active Bridge Converter using Covalent Active and Passive Components
2022
The Dual Active Bridge (DAB) converter is the most attractive bidirectional DC-DC converter topology in the distribution network. However, the DC bias is the most common issue in the dual active bridge converter due to the sudden change in internal or external phase shift angles to regulate the power signal. Consequently, it will increase conduction losses, a core saturation problem of High-Frequency Transformer (HFT), and loss of Zero Voltage Switching (ZVS) operation. Therefore, this paper presents the DC bias abatement in the DAB converter using covalent active and passive components to alleviate these problems. The proposed method employs the series capacitor in the windings of HFT as t…
Current-Based Measurement Technique for High Sensitivity Detection of Resistive Bridges With External Balancing Through Control Voltages
2017
We present a novel approach based on differential measurements of dc currents with very high sensitivity suitable for the detection of very small variations of resistors in Wheatstone full-bridge configurations. External control voltages allow for the compensation of the bridge unbalancing avoiding the need of changing its elements so making the solution suitable for integrated sensor systems. The proposed current-based measurement technique has been implemented through three different circuits, in transimpedance configuration and without the use of any further amplification stage, employing only two active blocks that allow for a very high integration level. The main characteristics of the…
On the sensitivity of bridge seismic response with local soil amplification
1998
The paper presents a numerical sensitivity study of the local site effects on structural response. Following a recently developed model of spatial coherency and a concept of a simple site coefficient the local site effects are modelled as filtrations of excitation processes with a frequency shift. An analysis of a bridge response with supports founded on different soils is carried out. The joint effects of dynamic response and pseudostatic motion are considered. Two types of response are analysed: longitudinal and transverse. The differences between dynamic displacements and force responses are pointed out.