Navegando por Assunto "Velocidade"

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Acesso aberto (Open Access)
Cálculo de velocidades em acidentes de trânsito: um software para investigação em física forense
(Universidade Federal do Pará, 2015-12) GURGEL, Walldiney Pedra; GOMES, Luiz Moreira; FERREIRA, Fernanda Carla Lima; GESTER, Rodrigo do Monte
In this paper we present and evaluate the Speed Calculations software for Traffic Accidents (SCTA). This application is designed for forensic studies and follows a protocol that allows the expert in crime scene analysis, even one that has no knowledge of physics, to estimate vehicle speeds involved in collisions and pedestrian accidents. SCTA uses basic concepts of classical mechanics, employs different coefficients of friction and takes into account the damage and the characteristics of the vehicles involved. This allows to determine the speeds in various accident situations. The software follows an open source philosophy, allowing implementation of new accident scenarios. Finally, as input data, SCTA needs only a few measurements performed by an expert. This avoids unnecessary scene observation and, optimizes and ensures reliability of forensic expertise.
Acesso aberto (Open Access)
Efeito da suplementação aguda de guaraná (Paullinia Cupana) e de uma dose equivalente de cafeína sobre parâmetros de potência muscular na execução do exercício supino reto
(Universidade Federal do Pará, 2024) COLAÇO, Fernando Sampaio; PENNA, Eduardo Macedo; http://lattes.cnpq.br/3746450308327976; https://orcid.org/0000-0003-0058-7967
Introduction: Guarana (Paullinia Cupana) is a natural substance rich in caffeine and other bioactive components. It is known that its acute ingestion can improve cognitive performance and effort perception parameters, but it is still unclear whether this ingestion can be efficient as an ergogenic substance in the production of muscular power, and whether this possible ergogenic effect is due to its caffeine concentration Objective: The objective of the present research was to compare the effect of acute ingestion of Guaraná (Paullinia Cupana) with an equivalent dose of caffeine on muscle power parameters. Methods: 34 individuals (18 to 35 years old) practicing resistance training were recruited and randomized into three experimental situations: PLACEBO (PLA); 500mg of guarana (GUA-500, containing 130mg of caffeine) and 130mg of caffeine (CAF-130). The individuals underwent a familiarization session with the bench press exercise performed on the Smith machine, in which the individuals' 1RM value and the optimal load for power production were measured. After a minimum interval of 48 hours from the 1RM test and optimal load, the individuals performed, on different days, the three experimental sessions in a randomized order: acute ingestion of caffeine, placebo or Guarana. Each experimental situation had a minimum washout interval of two days. A percentage of optimal load for power production was estimated through a progressive test on the bench press using only the bar, 30%, 40%, 50% and 60% of 1RM in order to identify the best load to perform 3 sets up to 40% of the loss of movement speed, with a 5-minute break between sets. Before performing the physical task, the individuals performed two sets of five repetitions using the load identified as optimal, with a 3-minute break between each set. warm-up series. Participants performed the concentric phase of movement performed at maximum intentional speed, and the eccentric phase lasting 2 seconds, in which the following variables were measured: average power (Watts), peak power (Watts), peak speed (m/s), and average propulsive speed (m/s). Results: Regarding the number of repetitions achieved between the experimental situations, no statistically significant difference was identified between the factors capsule ingested (F(2, 264) = 1.4689, P = 0.2320; partial η² = 0.01); between the three series performed (F(2, 264 = 0.5775, P = 0.5620) and in relation to Capsule: Series (F = 0.2937, P = 0.8819), in relation to Peak Power, the analyzes did not detect any significant effect on the values Capsule (F (2,264) = 0.0908; P = 0.7479), Series (F (2, 264) = 1.5053; P = 0.2238) and for the interactions Capsule: Series (F (4, 264) = 0.7674; P = 0.5453), regarding Average Power, the analysis did not detect significant effects for the Capsule factors (F (2, 264) = 0.028; P = 0.972; partial η² < 0.01), Series (F (2, 264) = 1.187; P = 0.306; partial η² < 0.01), and for the Capsule interaction: series (F (4,264) = 1.266; P = 0.283; partial η² = 0.02), as for Peak Speed, the analysis indicated no effect for the Capsule factor (F (2,263) = 1.162; P = 0.314; partial η² < 0.01), a significant effect for the factor Series (F (2, 263) = 3, 479; P = 0.03; partial η² = 0.03), in the Capsule:series interaction analysis (F (4, 263) = 1, 337; P = 0.256 ; partial η² = 0.02), no significant effect was identified. With regard to Average propulsive speed, no significant differences were identified for the factors Capsule (F (2, 264) = 0.401; P = 0.669; partial η² = 0.01), Series (F (2,264) = 1 , 327; P = 0.266; partial η² < 0.01) and for the Capsule: series interaction (F (4, 264) = 1.199; P = 0.311; partial η² < 0.01). Conclusion: Supplementation with 500mg of Guarana containing 130mg and 130mg of caffeine alone did not trigger any ergogenic effect on muscle power parameters and bench press speed.
Acesso aberto (Open Access)
Estimativa de parâmetros em meios VTI usando aproximações de sobretempo não hiperbólicas
(Universidade Federal do Pará, 2015-09-30) PEREIRA, Rubenvaldo Monteiro; CRUZ, João Carlos Ribeiro; http://lattes.cnpq.br/8498743497664023
Transversely isotropic (TI) media is a more realistic model for processing seismic data, for example, fractured media with preferred fracture direction, or composite by periodic thin layers. In particular, TI media with vertical symmetry axis (VTI) are widely used as models for P-wave propagation in shales, abundant rock in hydrocarbon reservoirs. However, the P-wave propagation in homogeneous media VTI have as their main characteristics, depend on four parameters of rigidity and also to possess: complicated algebraically phase velocity equation, difficult group velocity equation to explain and moveout equation nonhyperbolic. Therefore, several authors have presented parameterization and obtained approximations to these equations depending on three parameters only. Among these, the moveout approximations have been widely used in inverse methods to estimate lithological parameters in homogeneous media VTI. Such methods have generally been successful in estimated stacking velocity vn and the anellipticity parameter η, since these are the only ones required for generating initial models for the steps of seismic processing in the time domain. One of the most used methods for estimating parameters is the basedsemblance velocity analysis, though, because this method is limited to sections with small offset-depth ratio, adaptations for anisotropic media, considering nonhyperbolic moveout approximatios are required. In this paper, based on anelliptical approximation shifted hyperbola, anelliptical rational approximations are presented for: phase velocity, group velocity and moveout nonhyperbolic in homogeneous VTI horizontally layered media. The validity of these approximations is made by calculating their relative errors by comparing with other known approximations in the literature. To semblance-based velocity analysis is performed to measure the accuracy of the rational moveout approximations to estimate parameters in VTI media. The results demonstrate the great potential of rational approximations in inverse problems. In order to adapt to VTI media, we modify two coherence measurements by semblance which are sensitive to amplitude and phase variations. The accuracy and robustness of the adapted coherence measurements are validated by estimation of in anisotropic parameters in VTI media.
Acesso aberto (Open Access)
Numerical Study of Wake Characteristics in a Horizontal-Axis Hydrokinetic Turbine
(Universidade Federal do Pará, 2016-12) SILVA, Paulo Augusto Strobel de Freitas e; OLIVEIRA, Taygoara Felamingo de; BRASIL JUNIOR, Antonio Cesar Pinho; VAZ, Jerson Rogério Pinheiro
Over the years most studies on wake characteristics have been devoted to wind turbines, while few works are related to hydrokinetic turbines. Among studies applied to rivers, depth and width are important parameters for a suitable design. In this work, a numerical study of the wake in a horizontal-axis hydrokinetic turbine is performed, where the main objective is an investigation on the wake structure, which can be a constraining factor in rivers. The present paper uses the Reynolds Averaged Navier Stokes (RANS) flow simulation technique, in which the Shear-Stress Transport (SST) turbulent model is considered, in order to simulate a free hydrokinetic runner in a typical river flow. The NREL-PHASE VI wind turbine was used to validate the numerical approach. Simulations for a 3-bladed axial hydrokinetic turbine with 10 m diameter were carried out, depicting the expanded helical behavior of the wake. The axial velocity, in this case, is fully recovered at 12 diameters downstream in the wake. The results are compared with others available in the literature and also a study of the turbulence kinetic energy and mean axial velocity is presented so as to assess the influence of proximity of river surface from rotor in the wake geometry. Hence, even for a single turbine facility it is still necessary to consider the propagation of the wake over the spatial domain.