1,206 research outputs found
LIPIcs, Volume 251, ITCS 2023, Complete Volume
LIPIcs, Volume 251, ITCS 2023, Complete Volum
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
Holonomic Bessel modules and generating functions
We have solved a number of holonomic PDEs derived from the Bessel modules
which are related to the generating functions of classical Bessel functions and
the difference Bessel functions recently discovered by Bohner and Cuchta. This
-module approach both unifies and extends generating functions of the
classical and the difference Bessel functions. It shows that the algebraic
structures of the Bessel modules and related modules determine the possible
formats of Bessel's generating functions studied in this article. As a
consequence of these -modules structures, a number of new recursion
formulae, integral representations and new difference Bessel polynomials have
been discovered. The key ingredients of our argument involve new transmutation
formulae related to the Bessel modules and the construction of -linear maps
between different appropriately constructed submodules. This work can be viewed
as -module approach to Truesdell's -equation theory specialised to Bessel
functions. The framework presented in this article can be applied to other
special functions.Comment: 97 pages including one blank pag
Integrated Geophysical Analysis of Passive Continental Margins: Insights into the Crustal Structure of the Namibian Margin from Magnetotelluric, Gravity, and Seismic Data
Passive continental margin research amalgamates the investigation of many broad topics, such as the emergence of oceanic crust, lithospheric stress patterns and plume-lithosphere interaction, reservoir potential, methane cycle, and general global geodynamics. Central tasks in this field of research are geophysical investigations of the structure, composition, and dynamic of the passive margin crust and upper mantle. A key practice to improve geophysical models and their interpretation, is the integrated analysis of multiple data, or the integration of complementary models and data. In this thesis, I compare four different inversion results based on data from the Namibian passive continental margin. These are a) a single method MT inversion; b) constrained inversion of MT data, cross-gradient coupled with a fixed structural density model; c) cross-gradient coupled joint inversion of MT and satellite gravity data; d) constrained inversion of MT data, cross-gradient coupled with a fixed gradient velocity model. To bridge the formal analysis of geophysical models with geological interpretations, I define a link between the physical parameter models and geological units. Therefore, the results from the joint MT and gravity inversion (c) are correlated through a user-unbiased clustering analysis. This clustering analysis results in a distinct difference in the signature of the transitional crust south of- and along the supposed hot-spot track Walvis Ridge. I ascribe this contrast to an increase in magmatic activity above the volcanic center along Walvis Ridge. Furthermore, the analysis helps to clearly identify areas of interlayered massive, and weathered volcanic flows, which are usually only identified in reflection seismic studies as seaward dipping reflectors. Lastly, the clustering helps to differentiate two types of sediment cover. Namely, one of near-shore, thick, clastic sediments, and one of further offshore located, more biogenic, marine sediments
Towards an integrated vulnerability-based approach for evaluating, managing and mitigating earthquake risk in urban areas
Tese de doutoramento em Civil EngineeringSismos de grande intensidade, como aqueles que ocorreram na Turquía-Síria (2023) ou México (2017)
deviam chamar a atenção para o projeto e implementação de ações proativas que conduzam à identificação
de bens vulneráveis. A presente tese propõe um fluxo de trabalho relativamente simples para
efetuar avaliações da vulnerabilidade sísmica à escala urbana mediante ferramentas digitais. Um modelo
de vulnerabilidade baseado em parâmetros é adotado devido à afinidade que possui com o Catálogo Nacional
de Monumentos Históricos mexicano. Uma primeira implementação do método (a grande escala)
foi efetuada na cidade histórica de Atlixco (Puebla, México), demonstrando a sua aplicabilidade e algumas
limitações, o que permitiu o desenvolvimento de uma estratégia para quantificar e considerar as incertezas
epistémicas encontradas nos processos de aquisição de dados. Devido ao volume de dados tratado, foi
preciso desenvolver meios robustos para obter, armazenar e gerir informações. O uso de Sistemas de
Informação Geográfica, com programas à medida baseados em linguagem Python e a distribuição de
ficheiros na ”nuvem”, facilitou a criação de bases de dados de escala urbana para facilitar a aquisição de
dados em campo, os cálculos de vulnerabilidade e dano e, finalmente, a representação dos resultados.
Este desenvolvimento foi a base para um segundo conjunto de trabalhos em municípios do estado de
Morelos (México). A caracterização da vulnerabilidade sísmica de mais de 160 construções permitiu a
avaliação da representatividade do método paramétrico pela comparação entre os níveis de dano teórico
e os danos observados depois do terramoto de Puebla-Morelos (2017). Esta comparação foi a base para
efetuar processos de calibração e ajuste assistidos por algoritmos de aprendizagem de máquina (Machine
Learning), fornecendo bases para o desenvolvimento de modelos de vulnerabilidade à medida (mediante
o uso de Inteligência Artificial), apoiados nas evidências de eventos sísmicos prévios.Strong seismic events like the ones of Türkiye-Syria (2023) or Mexico (2017) should guide our attention
to the design and implementation of proactive actions aimed to identify vulnerable assets. This work is
aimed to propose a suitable and easy-to-implement workflow for performing large-scale seismic vulnerability
assessments in historic environments by means of digital tools. A vulnerability-oriented model based
on parameters is adopted given its affinity with the Mexican Catalogue of Historical Monuments. A first
large-scale implementation of this method in the historical city of Atlixco (Puebla, Mexico) demonstrated its
suitability and some limitations, which lead to develop a strategy for quantifying and involving the epistemic
uncertainties found during the data acquisition process. Given the volume of data that these analyses involve,
it was necessary to develop robust data acquisition, storing and management strategies. The use
of Geographical Information System environments together with customised Python-based programs and
cloud-based distribution permitted to assemble urban databases for facilitating field data acquisition, performing
vulnerability and damage calculations, and representing outcomes. This development was the
base for performing a second large-scale assessment in selected municipalities of the state of Morelos
(Mexico). The characterisation of the seismic vulnerability of more than 160 buildings permitted to assess
the representativeness of the parametric vulnerability approach by comparing the theoretical damage estimations against the damages observed after the Puebla-Morelos 2017 Earthquakes. Such comparison is
the base for performing a Machine Learning assisted process of calibration and adjustment, representing
a feasible strategy for calibrating these vulnerability models by using Machine-Learning algorithms and the
empirical evidence of damage in post-seismic scenarios.This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit
Institute for Sustainability and Innovation in Structural Engineering (ISISE), reference UIDB/04029/2020.
This research had financial support provided by the Portuguese Foundation of Science and Technology
(FCT) through the Analysis and Mitigation of Risks in Infrastructures (InfraRisk) program under the PhD
grant PD/BD/150385/2019
Backcasting for transformative water management
This thesis reports on a study on the use of backcasting for climate adaptation in water management. It offers new insights and recommendations for the further development of backcasting approaches for transformative climate adaptation
(b2023 to 2014) The UNBELIEVABLE similarities between the ideas of some people (2006-2016) and my ideas (2002-2008) in physics (quantum mechanics, cosmology), cognitive neuroscience, philosophy of mind, and philosophy (this manuscript would require a REVOLUTION in international academy environment!)
(b2023 to 2014) The UNBELIEVABLE similarities between the ideas of some people (2006-2016) and my ideas (2002-2008) in physics (quantum mechanics, cosmology), cognitive neuroscience, philosophy of mind, and philosophy (this manuscript would require a REVOLUTION in international academy environment!
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