52 research outputs found
Windowed Green function method for the Helmholtz equation in the presence of multiply layered media
This paper presents a new methodology for the solution of problems of two- and three-dimensional acoustic scattering (and, in particular, two-dimensional electromagnetic scattering) by obstacles and defects in the presence of an arbitrary number of penetrable layers. Relying on the use of certain slow-rise windowing functions, the proposed windowed Green function approach efficiently evaluates oscillatory integrals over unbounded domains, with high accuracy, without recourse to the highly expensive Sommerfeld integrals that have typically been used to account for the effect of underlying planar multilayer structures. The proposed methodology, whose theoretical basis was presented in the recent contribution (Bruno et al. 2016 SIAM J. Appl. Math. 76, 1871â1898. (doi:10.1137/15M1033782)), is fast, accurate, flexible and easy to implement. Our numerical experiments demonstrate that the numerical errors resulting from the proposed approach decrease faster than any negative power of the window size. In a number of examples considered in this paper, the proposed method is up to thousands of times faster, for a given accuracy, than corresponding methods based on the use of Sommerfeld integrals
Design and control of a bio-inspired soft wearable robotic device for ankle-foot rehabilitation
Abstract We describe the design and control of a wearable robotic device powered by pneumatic artificial muscle actuators for use in ankle-foot rehabilitation. The design is inspired by the biological musculoskeletal system of the human foot and lower leg, mimicking the morphology and the functionality of the biological muscle-tendon-ligament structure. A key feature of the device is its soft structure that provides active assistance without restricting natural degrees of freedom at the ankle joint. Four pneumatic artificial muscles assist dorsiflexion and plantarflexion as well as inversion and eversion. The prototype is also equipped with various embedded sensors for gait pattern analysis. For the subject tested, the prototype is capable of generating an ankle range of motion of 27 âą (14 âą dorsiflexion and 13 âą plantarflexion). The controllability of the system is experimentally demonstrated using a linear time-invariant (LTI) controller. The controller is found using an identified LTI model of the system, resulting from the interaction of the soft orthotic device with a human leg, and model-based classical control design techniques. The suitability of the proposed control strategy is demonstrated with several angle-reference following experiments
She\u27s So Bubbly
We introduce the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker, an astronomical alert broker designed to provide a rapid and self-consistent classification of large etendue telescope alert streams, such as that provided by the Zwicky Transient Facility (ZTF) and, in the future, the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST). ALeRCE is a Chilean-led broker run by an interdisciplinary team of astronomers and engineers working to become intermediaries between survey and follow-up facilities. ALeRCE uses a pipeline that includes the real-time ingestion, aggregation, cross-matching, machine-learning (ML) classification, and visualization of the ZTF alert stream. We use two classifiers: a stamp-based classifier, designed for rapid classification, and a light curveâbased classifier, which uses the multiband flux evolution to achieve a more refined classification. We describe in detail our pipeline, data products, tools, and services, which are made public for the community (see https://alerce.science). Since we began operating our real-time ML classification of the ZTF alert stream in early 2019, we have grown a large community of active users around the globe. We describe our results to date, including the real-time processing of 1.5 Ă 10âž alerts, the stamp classification of 3.4 Ă 10â· objects, the light-curve classification of 1.1 Ă 10ⶠobjects, the report of 6162 supernova candidates, and different experiments using LSST-like alert streams. Finally, we discuss the challenges ahead in going from a single stream of alerts such as ZTF to a multistream ecosystem dominated by LSST
Desenvolvimento de um roteiro conceitual para a gestĂŁo da biodiversidade e dos serviços ecossistĂȘmicos no Caribe mexicano
Coral reefs and mangroves support rich biodiversity and provide ecosystem services that range from food, recreational benefits and coastal protection services, among others. They are one of the most threatened ecosystems by urbanization processes. In this context, we developed a conceptual framework for the management of biodiversity and ecosystem services for these coastal environments. We based our workflow on two sections: âInformation baseâ and âGovernanceâ and use the Puerto Morelos Coastal region as a case study for coastal protection. Puerto Morelos is between two of the most touristic destinations of Mexico (Playa del Carmen and Cancun) that has experienced an increase of population in the past four decades resulting in an intensification of multiple threats to its ecosystems. We characterized the two ecosystems with a âManagement Unitsâ strategy. An expert-based ecosystem services matrix was also described in order to connect mangroves and coral reef ecosystems with the multiple beneficiaries. Then an ecosystem model (conceptual model and Global Biodiversity model) was developed. The conceptual model was useful in understanding the interplay processes between systems regarding the ecosystem service of âCoastal Protectionâ. The Global Biodiversity model evidenced the human-induced shifts in the biodiversity for mangrove and coral reefs ecosystems. Also, a projection for 2035 of âbestâ and âworstâ scenarios was applied using GLOBIO3. A DPSIR conceptual framework was used to analyze environmental problems regarding ecosystem services maintenance. Finally, we evaluated a set of policies associated with these ecosystems that favor coastal protection integrity. This framework facilitates the identification of the most relevant processes and controls about the provision of coastal protection service. It can also be useful to better target management actions and as a tool to identify future management needs to tackle the challenges preventing more effective conservation of coastal environments.Recifes de coral e manguezais possuem rica biodiversidade e fornecem serviços ecossistĂȘmicos, tais como, alimento, recreação, proteção costeira, entre outros. Esses ecossistemas encontram-se entre os mais ameaçados pelos processos de urbanização. Nesse contexto, desenvolvemos um roteiro conceitual para a gestĂŁo da biodiversidade e dos serviços ecossistĂȘmicos desses ambientes costeiros. Organizamos nossa sequĂȘncia de passos de trabalho em duas seçÔes: âBase de informaçÔesâ e âGovernançaâ e usamos a regiĂŁo costeira da cidade de Puerto Morelos (MĂ©xico) como um estudo de caso para analisar o serviço de proteção de costa. Puerto Morelos encontra-se entre dois dos destinos mais turĂsticos do MĂ©xico (Playa del Carmen e CancĂșn), e portanto sua população vem aumentando nas Ășltimas quatro dĂ©cadas, resultando na intensificação de mĂșltiplas ameaças para os ecossistemas. Primeiramente, caracterizamos os dois ecossistemas identificando-os como âUnidades de GestĂŁoâ, detalhando seus principais componentes e processos. AtravĂ©s de uma âMatriz de serviços ecossistĂȘmicosâ, construĂda com base na opiniĂŁo de especialistas, foram sistematizados os principais serviços ecossistĂȘmicos prestados pelos manguezais e recifes de corais aos mĂșltiplos beneficiĂĄrios. Em seguida, foi desenvolvida uma modelagem do sistema (e ecossistemas) atravĂ©s de sua representação na forma de um modelo conceitual e um modelo numĂ©rico de Biodiversidade Global. O modelo conceitual facilitou a compreensĂŁo dos processos de interação entre sistemas em relação ao serviço âProteção Costeiraâ. O modelo numĂ©rico evidenciou as mudanças induzidas pelo homem na biodiversidade dos ecossistemas de manguezal e recifes de coral. AlĂ©m disso, uma projeção dos cenĂĄrios âmelhorâ e âpiorâ foi desenvolvida para 2035 usando GLOBIO3. A Estrutura conceitual DPSIR foi aplicada para analisar problemas ambientais relacionados Ă manutenção dos serviços ecossistĂȘmicos. Finalmente, avaliamos um conjunto de polĂticas pĂșblicas associadas a esses ecossistemas e que favorecem a integridade da proteção costeira. Portanto, o roteiro facilitou a identificação dos principais processos e controles para a provisĂŁo de um serviço ecossistĂȘmico. AlĂ©m disso, pode ser Ăștil para direcionar melhor as açÔes de gerenciamento, bem como, uma ferramenta para identificar necessidades futuras de planejamento e gestĂŁo para enfrentar desafios que permitam uma conservação mais eficaz dos ambientes costeiros.Fil: SĂĄnchez Quinto, AndrĂ©s. Universidad Nacional AutĂłnoma de MĂ©xico; MĂ©xicoFil: Costa, Julliet Correa da. Universidade Federal de Santa Catarina; BrasilFil: Zamboni, Nadia Selene. Universidade Federal do Rio Grande do Norte; BrasilFil: Sanches, FĂĄbio H. C.. Universidade Federal de Sao Paulo; BrasilFil: Principe, Silas C.. Universidade de Sao Paulo; BrasilFil: Viotto, Evangelina del Valle. Provincia de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Universidad AutĂłnoma de Entre RĂos. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Santa Fe. Centro de Investigaciones CientĂficas y Transferencia de TecnologĂa a la ProducciĂłn; ArgentinaFil: Casagranda, Maria Elvira. Universidad Nacional de TucumĂĄn. Instituto de EcologĂa Regional. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - TucumĂĄn. Instituto de EcologĂa Regional; ArgentinaFil: Lima, Francisco A. da Veiga. Universidade Federal de Santa Catarina; BrasilFil: Possamai, Bianca. Universidade Federal Do Rio Grande.; BrasilFil: Faroni Perez, Larisse. Universidade Federal de Juiz de Fora; Brasi
KâAr and <sup>40</sup>Ar/<sup>39</sup>Ar geochronology of supergene processes in the Atacama Desert, Northern Chile: tectonic and climatic relations
<p>New KâAr and <sup>40</sup>Ar/<sup>39</sup>Ar data obtained for 29 samples of supergene alunite-, jarosite- and hollandite-group minerals from the Central Depression
of Northern Chile document almost continuous supergene oxidation from 33 to 9 Ma. The downward migration of supergene oxidation
zones is used to calculate maximum denudation rates of 16â35 m Ma<sup>â1</sup>. These calculated rates are sensitive to pre-existing topography and show that the present relief observed in the Central
Depression represents a modified Miocene landscape. The results presented here are in good agreement with previously published
geochronological data for the Atacama Desert. The combination of all published data, including the results presented here,
defines a continuous skewed distribution, with a maximum between 21 and 14 Ma. The relative paucity of ages greater than 30
Ma reflects the removal of supergene profiles by erosion during and immediately after the Incaic compressive deformation.
From 29 to 9 Ma, supergene oxidation profiles were generated under semi-arid conditions throughout the Atacama region. Ages
between 9 and 5 Ma on the northern and southern margins of the desert mark the end of supergene oxidation processes, consistent
with a Pliocene onset of present-day hyperaridity.
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Implantable Audiologic devices and Facial Plastic Surgery in elderly patients.
[eng] Introduction: The goal of this paper is to describe a previously unreported etiology for audiologic implant extrusion. It is necessary to place the implant closer to the cochlea for the correct conduction of the sound. This paper represents the first reported case of audiologic device extrusion secondary to previous rhytidectomy. Material and Methods: We present a case report of a 69-year-old patient with a history of rhytidectomy for aesthetic reasons 15 years ago. He was underwent transcutaneous active osseointegrated insertion, approximately 5 months later developed a 2 cm post-auricular soft tissue necrosis and partial extrusion. It was required a surgical intervention to solve the problem. Results: Exposure of otological implants requires medical/surgical intervention with antibiotic therapy, with or without replacement of such devices as well as the realization of rotational flaps to cover the skin defects. Conclusion: Previous periauricular surgery such as a parotidectomy or a rhytidectomy should be considered when select a patient to implant an otological device. In the case of osseointegrated implants, the percutaneous device could cause more skin problems than the transcutaneous one, which would lead us to choose one over another. In case of cochlear implants, should be located more posterior, away from the conflicting retroauricular area. Obviously as older as our patients get, higher are the chances to suffer those kind of complications. This complication has not been described previously, and should be analyzed in the preoperatory time in order to avoid bad results
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