2,687 research outputs found

    Transient Propagation and Scattering of Quasi-Rayleigh Waves in Plates: Quantitative comparison between Pulsed TV-Holography Measurements and FC(Gram) elastodynamic simulations

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    We study the scattering of transient, high-frequency, narrow-band quasi-Rayleigh elastic waves by through-thickness holes in aluminum plates, in the framework of ultrasonic nondestructive testing (NDT) based on full-field optical detection. Sequences of the instantaneous two-dimensional (2-D) out-of-plane displacement scattering maps are measured with a self-developed PTVH system. The corresponding simulated sequences are obtained by means of an FC(Gram) elastodynamic solver introduced recently, which implements a full three-dimensional (3D) vector formulation of the direct linear-elasticity scattering problem. A detailed quantitative comparison between these experimental and numerical sequences, which is presented here for the first time, shows very good agreement both in the amplitude and the phase of the acoustic field in the forward, lateral and backscattering areas. It is thus suggested that the combination of the PTVH system and the FC(Gram) elastodynamic solver provides an effective ultrasonic inspection tool for plate-like structures, with a significant potential for ultrasonic NDT applications.Comment: 46 pages, 16 figures, corresponding author Jos\'e Carlos L\'opez-V\'azquez, [email protected]. Changes: 1st, 4th, 5th paragraphs (intro), 3rd, 4th paragraphs (sec. 4); [59-60] cited only in appendixes; old ref. [52] removed; misprints corrected in the uncertainty of c_L (subsec. 3.1), citation to fig. 10 (sec. 4), size of images (caption fig.15); reference to Lam\'e constants removed in subsec. 3.

    Characterizing understory vegetation in Mediterranean forests using full-waveform airborne laser scanning data

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    [EN] The use of laser scanning acquired from the air, or ground, holds great potential for the assessment of forest structural attributes, beyond conventional forest inventory. The use of full-waveform airborne laser scanning (ALSFW) data allows for the extraction of detailed information in different vertical strata compared to discrete ALS (ALSD). Terrestrial laser scanning (TLS) can register lower vertical strata, such as understory vegetation, without issues of canopy occlusion, however is limited in its acquisition over large areas. In this study we examine the ability of ALSFW to characterize understory vegetation (i.e. maximum and mean height, cover, and volume), verified using TLS point clouds in a Mediterranean forest in Eastern Spain. We developed nine full-waveform metrics to characterize understory vegetation attributes at two different scales (3.75¿m square subplots and circular plots with a radius of 15¿m); with, and without, application of a height filter to the data. Four understory vegetation attributes were estimated at plot level with high R2 values (mean height: R2¿=¿0.957, maximum height: R2¿=¿0.771, cover: R2¿=¿0.871, and volume: R2¿=¿0.951). The proportion of explained variance was slightly lower at 3.75¿m side cells (mean height: R2¿=¿0.633, maximum height: R2¿=¿0.470, cover: R2¿=¿0.581, and volume R2¿=¿0.651). These results indicate that Mediterranean understory vegetation can be estimated and accurately mapped over large areas with ALSFW. The future use of these types of predictions includes the estimation of ladder fuels, which drive key fire behavior in these ecosystems.This research was developed mainly in the Integrated Remote Sensing Studio (IRSS) of University of British Columbia (UBC) (Canada) as a result of the Erasmus + KA-107 mobility grant. The authors thank the financial support provided by the Spanish Ministerio de Economia y Competitividad and FEDER, in the framework of the project CGL2016-80705-R.Crespo-Peremarch, P.; Tompalski, P.; Coops, N.; Ruiz Fernández, LÁ. (2018). Characterizing understory vegetation in Mediterranean forests using full-waveform airborne laser scanning data. Remote Sensing of Environment. 217:400-413. https://doi.org/10.1016/j.rse.2018.08.033S40041321

    Method for real-time measurement of the nonlinear refractive index

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    In this work, we propose a novel method for continuous real-time measurement of the dynamics of the nonlinear refractive index n2. This is particularly important for characterizing phenomena or materials (such as biological tissues, gases and other compounds) whose nonlinear behavior or structure varies rapidly with time. The proposed method ingeniously employs two powerful tools: the spectral broadening induced by self-phase modulation and the real-time spectral analysis using the dispersive Fourier transformation. The feasibility of the technique is experimentally demonstrated, achieving high-speed measurements at rates of several MHz

    SPANISH DEEP-SEA FISHERIES IN THE CECAF AREA

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    Deep-seafisheriestakeplaceatgreatdepths(between200-2000meters),oncontinentalslopes,oceanicseamounts,ridgesystemsbanks. Thesefisheriestargetdemersal/benthicspeciesusingarangeofgearsincludingbottomandmid-watertrawls,potsandlonglines. Deep-seafisheriestakeplaceinbothexclusiveeconomiczones(EEZs)andinareasbeyondnationaljurisdiction(ABNJ)

    Brief Results of a Trawl Experimental Survey at NW Atlantic

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    An experimental survey was carried out in NAFO Regulatory Area (Div. 6EFGH and 4XWVs) and adjacent international Southern waters during last Quarter of year 2004, with one polyvalent Spanish trawler, using "Gloria" pelagic gear and bottom gear, with the aim to obtain data on distribution and biology on pelagic and demersal species in non-habitual grounds for the Spanish fleet. A scientific observer was on board to collect the information on fishing activity (effort, depth, etc.) and biological data (length distributions, length-weight relationships, etc.). A total of 119 hauls were carried out. Samplings were conducted in a wide geographical and bathymetrical range. During the survey, Alfonsino (Beryx splendens) was the main caught species

    Ambivalence and innovative moments in grief psychotherapy: the cases of Emily and Rose

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    Several studies have suggested that the process of narrative change in psychotherapy occurs through the emergence and expansion of moments of novelty, known as innovative moments (IMs), that allow changes in the problematic self-narrative responsible for the client’s suffering. However, as these IMs challenge typical (and problematic) ways of acting, feeling, and thinking, they may also generate discrepancy or uncertainty. Clients may reduce uncertainty by returning to the problematic self-narrative immediately after the emergence of an IM, thus ensuring the homeostasis of the previous meaning system. This cyclical movement is a form of ambivalence, which can maintain problematic stability across therapy and lead to therapeutic failure. In this study, we identified return to the problem markers (RPMs), which are empirical indicators of the ambivalence process, for all IMs in two cases of constructivist grief psychotherapy. Both cases evidenced a high percentage of IMs with RPMs, and the evolution of IMs and RPMs along treatment was significantly correlated. We suggest that stability of the ambivalence process in grief psychotherapy may represent a form of self-protection from the anxiety or guilt of releasing pain as a disconnection from the deceased

    Zamia inermis, the more threatened cycad of Mexico

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    Zamia inermis (Zamiaceae) es una cícada rara, endémica y actualmente listada en Peligro Crítico de Extinción. De la misma, sólo se conoce una población compuesta de tres subpoblaciones, que se encuentra distribuido en tan sólo 2,5 km2 de pastizales y bosques estacionalmente secos y fragmentados. Durante la década de los 70's y 80s se sustrajeron ilegalmente muchas plantas para comercio, por lo que su población actual estimada está compuesta entre 300 y 700 ejemplares. Además, debido a la ausencia de su polinizador natural, un escarabajo, esta especie presenta un reclutamiento extremadamente bajo y su diversidad genética está insuficientemente representada en esta singular población. Por todas estas razones se le considera como las cícada mexicana que se encuentra en mayor riesgo de extinción.Zamia inermis (Zamiaceae) is a rare endemic and critically threatened species of cycad, with only one known population, composed of three subpopulations. The total population is distributed in only 2.5 km2 on grassland and fragmented seasonally dry forest. Many plants have been illegally removed for the ornamental plant trade during the 1970´s and 80s and its current population is estimated between 300 and 700 individuals, with extremely poor recruitment due to absence of its natural beetle pollinator. Additionally, its genetic diversity is under represented in this unique population, and for these reasons this species should be considered as the Mexican cycad at greatest extinction risk.A CONACYT por el apoyo financiero brindado al Proyecto de Ciencia Básica 152073
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