1,721,037 research outputs found
Data for Foreground Speech Analysis with Smartwatches in Unconstrained Daily Living Environments
No full textA dataset for foreground speech analysis with smartwatches in unconstrained daily living environments. Please cite:
Liang, Dawei, et al. "A Dataset for Foreground Speech Analysis With Smartwatches In Everyday Home Environments." 2023 IEEE International Conference on Acoustics, Speech, and Signal Processing Workshops (ICASSPW). IEEE, 2023
Data and tested models for AudioIMU
No full textData and weights of the tested models for paper "AudioIMU: Enhancing Inertial Sensing-Based Activity Recognition with Acoustic Models". Liang et al. 202
Data for Automated Face-To-Face Conversation Detection on a Commodity Smartwatch with Acoustic Sensing
No full textA dataset for conversation modelin
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
High-efficiency solar laser pumping by a ring-array concentrator
Full text linkAiming to significantly improve solar laser efficiency, in this thesis, a 20 mm length 5.5 mm diameter Nd:YAG single-crystal rod can be efficiently pumped by highly concentrated solar radiation through a modified ring-array concentrator. Composed of six coaxial parabolic reflective rings and a small diameter Fresnel lens, the 1500 mm diameter modified ring-array concentrator can tightly focus incoming solar radiation into a 5.0 mm full width at half maximum focal spot.
An innovative aspherical fused silica concentrator allows further pump light concentration into the Nd:YAG rod at the focal zone. A simple but effective water-cooling scheme within the aspherical concentrator constitutes another highlight of this assembly. Strong dependency of solar laser power on the rim angle of the ring-array concentrator was found through ZEMAX™ and LASCADTM analyses.
A continuous-wave solar laser power of 67.8 W at 1064 nm and 38.4 W/m2 collection efficiency was numerically calculated, being 1.22 times more than the previous record. Also, 1.29, 1.03 and 1.85 times improvements in conversion, slope efficiencies and brightness figure of merit, respectively, were numerically achieved.
The tracking error influence on solar laser output power was numerically calculated. A simple 1:7 scale model of the ring-array concentrator was also built to verify how the primary focusing performs in direct sunlight
Advances in solar-pumped laser efficiency and brightness
Full text linkAdvances in both solar-pumped laser efficiency and brightness are herein presented. Several solar laser prototypes with both end-side-pumping and side-pumping configurations were studied and developed to efficiently pump small diameter Nd:YAG laser rods, leading to substantial increase in solar laser collection efficiency and brightness, which have gained international recognitions.
All the design parameters were optimized in ZEMAX© non-sequential ray-tracing software. LASCAD© laser cavity analysis software was then used to optimize the laser resonator parameters. Based on the numerically optimization of the solar laser system, the solar laser prototypes were designed and built in Lisbon. Solar energy collection and concentration were achieved through the PROMES-CNRS heliostat-parabolic system, NOVA Fresnel lens system, and the recently new NOVA heliostat-parabolic system. Measurements of the solar input / laser output performance, beam quality M2 factors, and laser beam profiles for both multimode and fundamental mode regime
were performed and compared with that of the numerical results.
13.9 W/m2 solar laser collection efficiency was achieved in 2013, through PROMES heliostatparabolic mirror system, by end-side-pumping a 5 mm diameter, 25 mm length Nd:YAG laser rod. This result was further increased to 21.1 W/m2, in 2015, within the same solar facility. In 2016, 25 W/m2 collection efficiency was reported, by end-side-pumping a thinner laser rod through NOVA heliostat-parabolic mirror system. In addition to the enhancement of solar laser collection efficiency, the thermal performance of end-side-pumped solar laser was also substantially improved. In 2017, record solar laser collection efficiency of 31.5 W/m2 was reported by end-sidepumping a 4 mm diameter, 35 mm length Nd:YAG laser rod in PROMES-CNRS heliostatparabolic mirror system. Also, record slope efficiency of 8.9% was achieved.
A substantial progress in solar laser beam brightness with Fresnel lens was reported in 2013, through the first TEM00-mode solar laser. 1.9 W solar laser brightness was registered, being 6.6 times more than the previous record. The adoption of an asymmetric laser resonator, for maximum extraction of TEM00-mode solar laser, was also essential for improving significantly the solar laser brightness. By side-pumping a 3 mm diameter, 30 mm length Nd:YAG rod with a double-stage rectangular light guide / 2D-CPC concentrator, 4.0 W solar laser brightness was reported in 2015, doubling the previous record with Fresnel lens. TEM00-mode solar laser collection efficiency of
4.0 W/m2 was obtained by side-pumping a Nd:YAG grooved rod in 2016. Most recently, by endside-pumping a 4 mm diameter, 35 mm length, Nd:YAG rod, the TEM00 mode solar laser collection efficiency was almost doubled, reaching 7.9 W/m2. Record-high solar laser brightness of 6.5 W was also achieved.
Advances in solar laser beam stability were also achieved by developing sculptured twisted light guides for efficient uniform redistribution of pump light into a thin and long laser rod. In addition to this, we were also able to demonstrate the first emission of doughnut shaped solar laser beam, which may widen the applications areas of solar-pumped lasers. The research efforts performed during this work for enhancing both solar laser efficiency and beam brightness are explained. Experimental results are discussed and future suggestions are proposed
Desenvolvimento de um laser solar para aplicações médicas
Full text linkA cirurgia solar refere-se ao uso de luz solar concentrada para induzir transformações nos tecidos biológicos obtidas com sistemas laser cirúrgicos, com um custo significativamente menor. Porém, a diversidade de comprimentos de onda caraterísticos da radiação solar à superfície terrestre não promove uma interação seletiva com o tecido, contrariamente às técnicas com radiação laser.
A radiação solar concentrada pode ser utilizada também para produção de um feixe laser com densidades de potência semelhantes às utilizadas pelos lasers cirúrgicos. Neste projeto, foi desenvolvido um protótipo laser solar end-pump com meio ativo Nd:YAG (1at.% Nd3+). Este mostrou-se funcional sendo capaz de produzir até 22 W de potência laser com 1064 nm de comprimento de onda.
De forma a comparar o efeito em termos de espetro da radiação solar concentrada e radiação laser produzida pelo protótipo no tecido biológico, realizaram-se testes em amostras de peito de frango com semelhante distribuição de energia, divergência e área irradiada. Para tal, foram desenvolvidos 2 sistemas homogeneizadores de baixo custo e grande adaptabilidade. Estes mostram-se funcionais, verificando-se uniformização na área afetada em todas as amostras.
Os resultados mostram efeitos diferentes para a exposição à radiação laser e solar. Verificando-se menor absorção na superfície e maior penetração, sem carbonização, para a radiação laser. A tecnologia laser solar pode então conferir maior diversidade de tratamentos à cirurgia solar, mantendo um custo reduzido.
Desta forma, o presente trabalho consiste num avanço no sentido de democratização de tecnologias médicas modernas, com possibilidade de tratamento de patologias comuns em países com economias precárias
Forno solar com lentes de Fresnel e aplicações em laser solar
Full text linkDissertação para obtenção do Grau de Mestre em Engenharia FísicaCom este trabalho pretendeu-se estudar a eficácia de dois tipos de fornos solar com lentes de Fresnel e compará-los com os fornos solares parabólicos já existentes. Foi desenvolvido um protótipo para um dos fornos solares estudados.
Ao longo deste trabalho foram feitas simulações computacionais no software de simulação ótica ZEMAX© para encontrar o esquema do forno solar ideal, com o objetivo de obter o maior fluxo e potência solar no foco. Os esquemas de forno solar baseiam-se na redirecção e focagem de luz com lentes de Fresnel para uma região focal comum.
A melhor configuração para forno solar foi encontrada para um esquema de 6 lentes de Fresnel e 6 espelhos planos. Este esquema foi também simulado para bombeamento de um disco de Nd:YAG, com um concentrador secundário e respetivo sistema de arrefecimento, para produção de laser. A potência do laser e qualidade de feixe foram analisadas através do software LASCAD©.
Com a ajuda do Professor Dawei Liang e Msc. Joana Almeida foi realizada a construção do forno solar com 21 espelhos planos e 21 lentes de Fresnel
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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