Browsing by Tema "Acceleration"

Now showing 1 - 8 of 8

Acceleration Output Prediction of Buildings Using a Polynomial Artificial Neural Network
(Springer Nature, 2007) F.J. Rivero-Angeles; E. Gómez-Ramı́rez
Determination of maximum leaf velocity and acceleration of a dynamic multileaf collimator: Implications for 4D radiotherapy
(Wiley, 2005) K. Wijesooriya; C Bartee; Jeffrey V. Siebers; Sastry Vedam; Paul Keall
The dynamic multileaf collimator (MLC) can be used for four-dimensional (4D), or tumor tracking radiotherapy. However, the leaf velocity and acceleration limitations become a crucial factor as the MLC leaves need to respond in near real time to the incoming respiration signal. The aims of this paper are to measure maximum leaf velocity, acceleration, and deceleration to obtain the mechanical response times for the MLC, and determine whether the MLC is suitable for 4D radiotherapy. MLC leaf sequence files, requiring the leaves to reach maximum acceleration and velocity during motion, were written. The leaf positions were recorded every 50 ms, from which the maximum leaf velocity, acceleration, and deceleration were derived. The dependence on the velocity and acceleration of the following variables were studied: leaf banks, inner and outer leaves, MLC-MLC variations, gravity, friction, and the stability of measurements over time. Measurement results show that the two leaf banks of a MLC behave similarly, while the inner and outer leaves have significantly different maximum leaf velocities. The MLC-MLC variations and the dependence of gravity on maximum leaf velocity are statistically significant. The average maximum leaf velocity at the isocenter plane of the MLC ranged from 3.3 to 3.9 cm/s. The acceleration and deceleration at the isocenter plane of the MLC ranged from 50 to 69 cm/s2 and 46 to 52 cm/s2, respectively. Interleaf friction had a negligible effect on the results, and the MLC parameters remained stable with time. Equations of motion were derived to determine the ability of the MLC response to fluoroscopymeasured diaphragm motion. Given the present MLC mechanical characteristics, 4D radiotherapy is feasible for up to 97% of respiratory motion. For the largest respiratory motion velocities observed, beam delivery should be temporarily stopped (beam hold).
Efectos sísmicos de la componente vertical en edificios aporticados de acero
(Universidad Autónoma del Estado de México, 2008) Lucila Vilera; Pedro J. Rivero; William Lobo Quintero
"Este trabajo evalúa la influencia de la componente vertical del movimiento sísmico del terreno, en la respuesta dinámica de estructuras regulares de acero. Para un grupo de estructuras de planta regular, simétrica, de tres vanos de 6¡metros de longitud en cada dirección, con alturas de entrepiso de 3 metros y de tres, nueve y dieciocho pisos. Estas edificaciones se someten a la acción de cinco registros acelerográficos provenientes de distancias epicentrales cortas, obtenidos sobre material rocoso y con diferentes relaciones entre las aceleraciones máximas verticales y horizontales (V/H). Se realizan análisis tridimensionales de historia de aceleraciones, considerando comportamiento no lineal según lo prescrito por la ATC-40 y la FEMA 273. Los resultados muestran que la componente vertical tiene marcada influencia sobre la demanda de fuerza axial en las columnas internas de las edificaciones. Además se nota como la historia de aceleraciones verticales en la base se mantiene prácticamente igual en la altura. Sobre las columnas se produce una mayor cantidad de ciclos de carga axial que cuando se considera solo la componente horizontal. Los desplazamientos laterales y las derivas de piso no se ven mayormente afectadas cuando se incluye la componente vertical del sismo. En general, los análisis muestran que el efecto de la componente vertical en la respuesta dinámica de estas estructuras depende principalmente de la cercanía a la fuente y de la relación entre la aceleración máxima vertical y la horizontal."
Nonlinear Civil Structures Identification Using a Polynomial Artificial Neural Network
(Springer Science+Business Media, 2005) F.J. Rivero-Angeles; E. Gómez-Ramı́rez; R. Garrido
Physics of ion acceleration in the solar flare on 2005 September 7 determines γ-ray and neutron production
(Elsevier BV, 2009) K. Watanabe; R. P. Lin; Säm Krucker; R. J. Murphy; G. H. Share; Mark Harris; M. Gros; Y. Muraki; T. Sako; Y. Matsubara
Set-membership state estimation of autonomous surface vehicles with a partially decoupled extended observer
(2022) Luís Orihuela; Christophe Combastel; Guillermo Bejarano
This work presents a set-membership state estimator for autonomous surface vehicles, based on an augmented state including lumped disturbances. The position and orientation are assumed to be measured subject to bounded noises. A novel dynamical decomposition decouples the estimation problem into two simpler subproblems, for the rotational and positional dynamics. Then, under physically motivated assumptions about the vessel maximum velocities and acceleration rates, the estimator computes sets enclosing the positions, velocities, and lumped generalised disturbances gathering several kinds of modelling uncertainties. The sets are described by zonotopes. A set-based estimation of the lumped generalised disturbances paves the way toward an enhanced motion control scheme, where low-level controllers could compensate them, depending on the estimation accuracy. Several simulations with a well-known test-bed craft compare the performance of the proposed algorithm with a previous one from the literature under realistic environmental conditions.
Simultaneous Observation of Solar Neutrons from the International Space Station and High Mountain Observatories in Association with a Flare on July 8, 2014
(Springer Science+Business Media, 2016) Y. Muraki; D. Lopez; K. Koga; F. Kakimoto; T. Goka; L. X. González; S. Masuda; Y. Matsubara; H. Matsumoto; P. Miranda
Trapping and acceleration of relativistic electrons by uniform radially polarized Bessel-Gauss beams
(Optica Publishing Group, 2025) Haixian Ye; Leifeng Cao; Xiaojuan Wang; Teng-Hui You; Cangtao Zhou; Hua Zhang; Yuanlong Deng
This paper presents an efficient method for trapping and accelerating a 50 MeV relativistic electron beam in vacuum using radially polarized cylindrical vector Bessel-Gauss (BG) beams. Unlike conventional Laguerre-Gaussian (LG) beams, the non-diffracting property of BG beams extends the laser-electron interaction length, while their uniform field distribution enhances beam quality. The unique electric field structure of radially polarized light, featuring a strong longitudinal component, provides superior transverse confinement compared to circularly polarized beams, significantly reducing electron beam divergence. Three-dimensional particle-in-cell (PIC) simulations performed with the code EPOCH demonstrate that the electron energy increases from 50 MeV to 800 MeV, exhibiting less than 10.2% energy spread and a divergence angle below 1.5°. Further investigations reveal that higher laser intensity boosts electron energy without compromising beam collimation, while injection duration critically influences microbunch formation and maximum momentum. This approach offers a promising solution for compact high-energy electron accelerators, with potential applications in free-electron lasers and medical radiotherapy.