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Soil Mechanics
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Sedimentation analysis is used to determine grain size distribution of the soil fraction passing through 0.075 mm size sieve. It is based on “Stoke’s Law,” which gives the terminal velocity of a small sphere settling in a fluid of infinite medium. When a small sphere settles in a fluid, its velocity first increases under the action of gravity, but the drag force comes into action and retards the velocity. After an initial adjustment period, steady conditions are attained and the velocity becomes constant. The velocity attained is known as terminal velocity. Terminal velocity is given by V=(γs–γw)D2/18µ
Introduction
Published in Vladimir A. Dobrushkin, Applied Differential Equations, 2018
Velocity is a measure of both the speed and direction that an object is traveling. When we consider only rotational motion, the direction of the object is known and its velocity is defined by its magnitude speed. Therefore, we can drop vector notation and operate only with scalar quantities. The angular velocity (or instantaneous angular speed) of a body rotated about a fixed axis is the ratio of the angle traversed to the amount of time it takes to traverse that angle when the time tends to zero: ω=limΔt→0ΔθΔt=θ˙=dθdt
The role of physical training on G-force tolerance in fighter pilots
Published in Howard M. Hensel, Maria Filomena Fontes Ricco, Culture and Defence in Brazil, 2017
Acceleration is defined as the rate of velocity and is described as a vector with magnitude and direction. In aviation, it is expressed as a multiple of the acceleration due to gravity (9.81 m/s²) (Green, 2006). If a pilot weighing 70kg is subject to an acceleration of 5G, he or she will experience a force that is five times his or her weight (350kg). When a pilot experiences +Gz, the associated force caused by a curving path increases pressure on the buttocks against the surface of the seat. The pilot may feel some discomfort, such as visual changes or hypoxia (Green, 2006). As +Gz increases, a pilot in flight can experience dimming of vision called tunnel vision; +Gz can also affect central vision, known as grey-out and complete loss of vision, or blackout (Banks et al., 2008).
Rotational shot put: a phase analysis of current kinematic knowledge
Published in Sports Biomechanics, 2022
Michael Schofield, John B. Cronin, Paul Macadam, Kim Hébert-Losier
Velocity is a vector quantity that has a magnitude and a direction in three-dimensional space. Speed, on the other hand, is a scalar quantified by magnitude only. All investigations reporting release velocity have also provided release angle (Ariel et al., 2004; Coh & Jost, 2005; Čoh & Štuhec, 2005; Čoh et al., 2008; Lipovesk et al., 2011; Schaa, 2010; Stepanek, 1990) with the exception of Dinu, Natta, Huiban, and Houel (2014) who reported shot speed only with no directional information. Several authors have presented speed, but not velocity, between first double support and second double support phases (Gutierrez-Davila et al., 2009; Luthanen, 1998). A few authors graphically reported x–y and y–z shot movements, providing a direction to the magnitude of velocities (Byun et al., 2008; Čoh et al., 2008; Stepanek, 2009). For simplicity, the magnitudes of velocity metrics are pooled. Therefore, the values reported are representative of shot speed within phases and are not directionally specific.
Spontaneous Combustion Characteristics of Coal by Using the Simultaneous Thermal analysis–Fourier Transform Infrared Spectroscopy Technique
Published in Combustion Science and Technology, 2021
Xiaokun Chen, Teng Ma, Xiaowei Zhai, Changkui Lei, Bobo Song
When the ignition temperature is reached, the DTG curve falls rapidly. This is the result of a rapid and violent reaction causing the benzene ring in the coal macromolecule to fracture and the production of large amounts of gas (Rousset et al. 2017). Ignition temperature should be a transition point from one state to another, so the point used to determine ignition temperature should be a critical point on the curve (Zhang et al. 2018a). However, the T3’s obtained by the tangent method do not exhibit a sudden change in the thermogravimetric curve. Acceleration is a physical quantity that describes how fast an object changes in velocity. Ta is the maximum acceleration point in the combustion stage. The maximum exothermic rate and the maximum rates of CO, CO2, and H2O gas production for coal samples with the same degree of metamorphism is close to point Ta. This indicates that a sudden reaction occurs at temperature Ta, when the acceleration rate of mass loss is the largest, and the rate of heat and gas release is also the largest. Ta is the transition point where the coal reacts with oxygen from one state to another. Therefore, the ignition point indicated by point Ta is considered to be more accurate than the T3 determined by the tangent method. The maximum mass loss rate is indicated by T4. The maximum heat release and CO, CO2, and H2O gas production of the same metamorphic rank are close to temperature point T4. Combined with the TG, DSC, CO, CO2 and H2O curves in the spontaneous combustion process of coal (from Figures 2–5), the temperature Ta and T4 are important for judging the likelihood of the coal spontaneously combusting.
Speed related variables for crash injury risk analysis: what has been used?
Published in International Journal of Crashworthiness, 2022
Speed is a scalar quantity measured in units of distance divided by time (e.g. kilometres per hour) and the magnitude of the velocity, which is the speed with a direction. Although in the literature the term speed is widely used but explored using a variety of measures. Figure 2 shows the different measures used to examine the speed contribution to road injuries. The literature studies aimed at capturing the effect of this risk factor by investigating the average speed, speed limit, speed impact, and speed ratio or delta-V contribution to the CIR.