172,193 research outputs found
Integration of non-linear behavioural models within the TLM - receiver input and supply ports
No full textTowards performance-based design of MDOF structures with explicit consideration of residual deformations
No full textSpecial Issue on Performance Based Seismic DesignMost structures designed according to current code provisions will sustain residual deformations in
the event of a design-level earthquake, even if they perform exactly as expected. Despite this reality, little
consideration is currently given to residual deformations when assessing the seismic performance or in
the design of seismic resistant structures. Parameters influencing residual deformations are first identified
and a framework for evaluating performance based on a combination of maximum and residual response
indices is proposed. Non-linear residual displacement spectra are computed for a number of SDOF
hysteretic systems and design spectra, based on residual/maximum displacement ratios, are suggested as a
function of effective secant period. Analyses are then extended to the response of MDOF systems through
a series of non-linear time history analyses. The direct displacement based design method is then
modified to include an explicit consideration of residual deformations in the early stages of the design
procedure. A discussion on design decisions affecting residual deformations is also presented
A TLM approach for the modelling of high and low frequency EMC problems in power systems
No full textThe EMC analysis of complex systems, as the electrified railway where trainset, power supply systems, telecommunication network and train detection and control systems are closely coupled by a variety of mechanisms, requires a detailed knowledge of the internal coupling relationships of the system components.
The lack of information preclude any rigorous deterministic prediction of EMI and it requires a test campaigns in order to verify compliance with the limits fixed by international standards on EMI.
Nevertheless, the difficulty in carrying out measurement in reproducible way and the cost of a possible system re-design, if a violation of the EM emission is found, suggest the need for a characterisation of EM environment right from the start of the project phase. For this purpose it is necessary, starting from the models of the main noise source and victims, to provide of a methodology capable of describing in an easy way the main coupling mechanisms between the noise sources and the susceptible victims, taking into account both low frequency and high frequency phenomena.
On this basis in this paper a new methodology is proposed for the electromagnetic characterisation of the electrified railway systems. In particular a method is presented based on Transmission Line Modelling (TLM) able to model the electromagnetic interaction between electrical circuits which model the sources and the victims of the EMI.
A software tool which implements these algorithms is presented and the results of some simulations are discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Codifying and commodifying nature: Narratives on forest property rights and the implementation of tenure regularization policies in Northwestern Argentina
No full textEnvironmental resource management requires negotiation among state and non-state actors with conflicting goals and different levels of influence. In northwestern Argentina, forest policy implementation is described as weak, due to governance structure and ambiguities in the law. We studied how policy actors’ attitudes and their positions in the forest governance network relate to the implementation of land tenure regularization in a context where land tenure regularization is at the core of struggles over environmental policies. We focused on the Chaco Salteño part of the Gran Chaco ecosystem, one of the world’s major deforestation frontiers. We argue that the presence of weak advocacy coalitions requires an analysis of agency to understand this policy process. Our policy network analysis revealed a lack of clear contrasting factions, due to a core–periphery structure. The core of the network brings together all core beliefs but not all of the most influential actors. Assessing network centrality and reputational influence enabled us to identify actors with exceptional agency. We contribute to the debates on advocacy coalitions and on land tenure by distinguishing between attitudes toward tenure regularization policies and their actual implementation in a context where actors have diverging interests and objectives
Collaborative governance networks: A case study of argentina’s forest law
No full textDeforestation causes biodiversity loss and the eviction of small-scale ranchers and indigenous people. Accordingly, it is a global issue in environmental politics. This article analyzes a participatory governance system associated with the implementation of Argentina’s forest law in a hotspot of deforestation: the province of Salta in the Gran Chaco ecoregion. Specifically, this article investigates policy actors’ core beliefs, how they match with policy network clusters, and how this affects the implementation of the forest law. The study is based on a unique data set derived from extensive fieldwork and a network survey among all actors who participate in the policy forums. After defining three main core beliefs that describe policy actors’ motivations, we systematically analyze all key actors’ beliefs as well as their interactions in the various policy networks. This analysis shows that it is necessary to empirically identify coalitions based on both behavior and core beliefs to understand the limited implementation of the law. Our methodological approach holds promise for the analysis of other governance systems where multiple stakeholders engage in consensus-oriented decision-making
Electromagnetic coupling inside enclosures with closely coupled electric monopoles and conducting planes
No full textThe efficiency and reliability of the multiple-mode transmission line theory applied to predict the electromagnetic coupling between electric monopoles with conducting planes inside a metallic enclosure is assessed in this paper. The planes are represented with an equivalent impedance through a transmission line analogy. Particularly critical coupling configurations, such as close monopole-to-plane and plane-to-plane configurations are tested. The results obtained with the proposed method are compared to experimental measurements and transmission-line modelling method (TLM) numerical simulations. The proposed model is attractive due to its rapidity and good accuracy in predicting the coupling configurations examined
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