Search results for " travel"
showing 10 items of 196 documents
Smooth and non-smooth traveling wave solutions of some generalized Camassa–Holm equations
2014
In this paper we employ two recent analytical approaches to investigate the possible classes of traveling wave solutions of some members of a recently-derived integrable family of generalized Camassa-Holm (GCH) equations. A recent, novel application of phase-plane analysis is employed to analyze the singular traveling wave equations of three of the GCH NLPDEs, i.e. the possible non-smooth peakon, cuspon and compacton solutions. Two of the GCH equations do not support singular traveling waves. The third equation supports four-segmented, non-smooth $M$-wave solutions, while the fourth supports both solitary (peakon) and periodic (cuspon) cusp waves in different parameter regimes. Moreover, sm…
News about the Aragonese Botanist Martín Sessé Lacasta
2018
Se dan noticias del paso por la Universidad de Zaragoza y por América del médico y naturalista aragonés Martín Sessé Lacasta, que impulsó desde América la Expedición Botánica de Nueva España, así como la creación del Jardín botánico de México. Se trata de una de las personalidades que más han prestigiado la labor científica de España en América. / News about the stay of the Aragonese doctor and naturalist Martín Sessé Lacasta both in the Universidad de Zaragoza and Central America. He was part of the Botanical Expedition in Nueva España where he promoved Botanical studies and helped creating the Botanical Garden in Mexico. He is one of the most important Spanish scientist who spread Science…
Probing the origin of cosmic-rays with extremely high energy neutrinos using the IceCube Observatory
2013
We have searched for extremely high energy neutrinos using data taken with the IceCube detector between May 2010 and May 2012. Two neutrino induced particle shower events with energies around 1 PeV were observed, as reported previously. In this work, we investigate whether these events could originate from cosmogenic neutrinos produced in the interactions of ultra-high energy cosmic-rays with ambient photons while propagating through intergalactic space. Exploiting IceCube's large exposure for extremely high energy neutrinos and the lack of observed events above 100 PeV, we can rule out the corresponding models at more than 90% confidence level. The model independent quasi-differential 90% …
Multi-scale analysis of the European airspace using network community detection
2014
We show that the European airspace can be represented as a multi-scale traffic network whose nodes are airports, sectors, or navigation points and links are defined and weighted according to the traffic of flights between the nodes. By using a unique database of the air traffic in the European airspace, we investigate the architecture of these networks with a special emphasis on their community structure. We propose that unsupervised network community detection algorithms can be used to monitor the current use of the airspaces and improve it by guiding the design of new ones. Specifically, we compare the performance of three community detection algorithms, also by using a null model which t…
The General Routing Problem polyhedron: Facets from the RPP and GTSP polyhedra
1998
[EN] In this paper we study the polyhedron associated with the General Routing Problem (GRP). This problem, first introduced by Orloff in 1974, is a generalization of both the Rural Postman Problem (RPP) and the Graphical Traveling Salesman Problem (GTSP) and, thus, is NP -hard. We describe a formulation of the problem such that from every non-trivial facet-inducing inequality for the RPP and GTSP polyhedra, we obtain facet-inducing inequalities for the GRP polyhedron, We describe a new family of facet-inducing inequalities for the GRP, the honeycomb constraints, which seem to be very useful for solving GRP and RPP instances. Finally, new classes of facets obtained by composition of facet-i…
Insensitivity of Tree-Ring Growth to Temperature and Precipitation Sharpens the Puzzle of Enhanced Pre-Eruption NDVI on Mt. Etna (Italy)
2017
On Mt. Etna (Italy), an enhanced Normalized Difference in Vegetation Index (NDVI) signature was detected in the summers of 2001 and 2002 along a distinct line where, in November 2002, a flank eruption subsequently occurred. These observations suggest that pre-eruptive volcanic activity may have enhanced photosynthesis along the future eruptive fissure. If a direct relation between NDVI and future volcanic eruptions could be established, it would provide a straightforward and low-cost method for early detection of upcoming eruptions. However, it is unclear if, or to what extent, the observed enhancement of NDVI can be attributed to volcanic activity prior to the subsequent eruption. We conse…
Visioni dell’America. Viaggio, spazialità e narrazione in De Amicis e Amado
2021
Nella prospettiva della geografia culturale l’odeporica offre l’opportunità di studiare alcune dinamiche di (ri)produzione simbolica relative al modo di concepire e rappresentare concetti chiave quali lo spazio, il paesaggio e le interazioni umane. Questo lavoro, partendo dall’analisi di alcuni brani significativi di due raccolte di scritti, In America (1897) di Edmondo De Amicis e In giro per le Americhe (2001) di Jorge Amado, studia, con un approccio geografico-culturale e semiotico, le modalità di costruzione e descrizione dello spazio fisico e simbolico comprese le «frontiere», nonché le interazioni e la socialità attraverso la testualizzazione di esperienze diverse. La comparazione fra…
Social isolation and physical activity mediate associations between free bus travel and wellbeing among older adults in England
2019
Background: Aims of this study were: (i) to examine relationships between free bus travel and wellbeing, and (ii) to assess the extent to which these associations can be explained by two key potential mediators: social isolation and physical activity. Methods: Data were from the English Longitudinal Study of Ageing (n = 5861). Linear regression models tested associations between (i) concessionary bus pass (CBP) ownership and (ii) frequency of CBP use and three measures of wellbeing (quality of life, life satisfaction, depressive symptoms), adjusting for age, sex, marital status, socioeconomic status and limiting long-standing illness. Mediation analyses tested the role of (i) social isolati…
Active Travel and Mild Cognitive Impairment among Older Adults from Low- and Middle-Income Countries
2021
Active travel may be an easily achievable form of physical activity for older people especially in low- and middle-income countries (LMICs), but there are currently no studies on how this form of physical activity is associated with a preclinical state of dementia known as mild cognitive impairment (MCI). Therefore, we aimed to investigate the association between active travel and MCI among adults aged ≥50 years from six LMICs. Cross-sectional, community-based data from the World Health Organization’s Study on Global Ageing and Adult Health were analyzed. The definition of MCI was based on the National Institute on Ageing-Alzheimer’s Association criteria. Active travel (minutes/week) was as…
La GTT, metodologia non invasiva per caratterizzare lo strato esterno degradato dei manufatti lapidei
2008
In questo lavoro viene descritta una metodologia non invasiva ne, tanto meno, distruttiva per studiare il degrado degli strati superficiali dei manufatti lapidei, correlandolo ai parametri di resistenza meccanica. La metodologia adopera come strumento diagnostico la propagazione delle onde elastiche nel mezzo in esame. In particolare, considerando che l'ordine di grandezza degli spessori ricercati è compreso tra le frazioni di millimetro e pochi centimetri, le frequenze delle onde elastiche utilizzabili sono quelle ultrasoniche, dalle decine di kHz ai MHz (e quindi, con velocità di propagazione dell'ordine di 4000 m/s, con lunghezze d'onda dai centimetri alle frazioni di millimetro). Questa…