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    How fractal complexity distorts distance and elevation gain in trail and mountain running: The case for course measurement standardization
    (SAGE Publications, 2025-05-21)
    Raimundo Sanchez
    ;
    Pascal E Egli
    ;
    Kilian Jornet
    ;
    Michael Duggan
    ;
    Manuela Besomi  
    This study investigates how fractal complexity affects Trail and mountain running (TMR) race course measurements at varying GPS resolutions and emphasizes the need for standardized course measurement protocols. GPX files from 34 UTMB World Series race courses, including final events in Chamonix, were analyzed. Horizontal distance, elevation gain, km-effort, and fractal complexity were computed at varying GPS spatial resolutions (0.2–100 m). Elevation data were refined using a 20-cm resolution Digital Elevation Model (DEM) to ensure consistency across the dataset. The courses were systematically resampled and compared to assess the effects of spatial resolution on race measurements and classifications. The findings reveal that a decrease in GPS spatial resolution significantly reduces measured distances and elevation gains. Discrepancies in kilometer-effort reached up to 14% (mean = 7.0%, SD = 3.8%), horizontal distance up to 6.3% (mean = 2.9%, SD = 1.5%), and elevation gain up to 32% (mean = 14.0%, SD = 9.5%). Adopting a 1-m resolution, chosen for its practical balance between capturing terrain complexity at a human scale and computational efficiency, would enhance the reliability of distance, elevation gain, and km-effort calculations, ensuring fairer race classifications and improved comparability across events.
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    Transmission dynamics and control of COVID-19 in Chile, March-October, 2020
    (2021)
    Amna Tariq
    ;
    Eduardo A. Undurraga
    ;
    CASTILLO LABORDE, CARLA CECILIA  
    ;
    Katia Vogt-Geisse
    ;
    Ruiyan Luo
    <jats:p>Since the detection of the first case of COVID-19 in Chile on March 3<jats:sup>rd</jats:sup>, 2020, a total of 513,188 cases, including ~14,302 deaths have been reported in Chile as of November 2<jats:sup>nd</jats:sup>, 2020. Here, we estimate the reproduction number throughout the epidemic in Chile and study the effectiveness of control interventions especially the effectiveness of lockdowns by conducting short-term forecasts based on the early transmission dynamics of COVID-19. Chile’s incidence curve displays early sub-exponential growth dynamics with the deceleration of growth parameter,<jats:italic>p</jats:italic>, estimated at 0.8 (95% CI: 0.7, 0.8) and the reproduction number,<jats:italic>R</jats:italic>, estimated at 1.8 (95% CI: 1.6, 1.9). Our findings indicate that the control measures at the start of the epidemic significantly slowed down the spread of the virus. However, the relaxation of restrictions and spread of the virus in low-income neighborhoods in May led to a new surge of infections, followed by the reimposition of lockdowns in Greater Santiago and other municipalities. These measures have decelerated the virus spread with<jats:italic>R</jats:italic>estimated at ~0.96 (95% CI: 0.95, 0.98) as of November 2<jats:sup>nd</jats:sup>, 2020. The early sub-exponential growth trend (<jats:italic>p</jats:italic>~0.8) of the COVID-19 epidemic transformed into a linear growth trend (<jats:italic>p</jats:italic>~0.5) as of July 7<jats:sup>th</jats:sup>, 2020, after the reimposition of lockdowns. While the broad scale social distancing interventions have slowed the virus spread, the number of new COVID-19 cases continue to accrue, underscoring the need for persistent social distancing and active case detection and isolation efforts to maintain the epidemic under control.</jats:p>
    Scopus© Citations 45  1
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    A simplified and versatile element model for elastomeric seismic isolation bearings
    (2021)
    Sebastián Miranda
    ;
    Eduardo Miranda
    ;
    Juan Carlos de la Llera
    A novel approach for two-dimensional modeling of elastomeric bearings using three springs in parallel is presented. This simplified element model considers as follows: (1) an elastoplastic spring with a smooth transition between branches; (2) a linear elastic spring; and (3) a non-linear elastic spring, and is fully defined by only six parameters. The main advantages of the simplified model are twofold: (1) versatility, as a single model is capable of accurately reproducing the main characteristics of the hysteretic behavior of different types of rubber-based seismic isolators, including low damping rubber bearings (LDRBs), high damping rubber bearings (HDRBs), and lead-core rubber bearings (LRBs) and (2) simplicity, as it requires fewer parameters and it is easier to calibrate from experimental cyclic test results than most currently available models. Model parameters’ identification is illustrated using quasi-static cyclic and earthquake simulator tests of HDRBs and LRBs, demonstrating that the model shows a good agreement between the test-measured and model-predicted hysteretic behavior. Different objective functions are evaluated in the optimization procedure, and their effect on the identified parameters is studied and discussed. This practitioner-oriented model is particularly amenable for implementation in general-purpose structural analysis software. Its usage is strongly recommended as an initial-stage design tool to select the optimal isolation system for a specific project.
      11Scopus© Citations 8