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Sleeper contact modelling in asphalt overlayment trackbeds
Published in Inge Hoff, Helge Mork, Rabbira Garba Saba, Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields, Volume 3, 2022
P. Jørgensen, R.N.H. Perslev, E. Levenberg*
The problem considered hereafter deals with a single loaded sleeper, having a geotextile at the bottom, and resting on the surface of an asphalt pavement system. A plan view of this arrangement is shown in Figure 1a, and a cross-sectional view is shown in Figure 1b. As can be seen, the sleeper is a rectangular cuboid hosting a pair of rail pads. Train axle loads applied to the rails are transferred to the sleeper via these rail pads. The pavement system has three layers: asphalt concrete, aggregate base, and subgrade soil (or rock) extending to a large depth. The geotextile is a thin layer with an area that identically covers the sleeper’s bottom.
Introduction to Robotic Manipulators
Published in Kevin Russell, Qiong Shen, Raj S. Sodhi, Kinematics and Dynamics of Mechanical Systems Implementation in MATLAB® and Simmechanics®, 2018
Kevin Russell, Qiong Shen, Raj S. Sodhi
The global path point coordinates 0{p3} should be prescribed from within the workspace of the P-P-P robotic manipulator. This ensures that the prescribed points will be achieved by the robotic manipulator. As shown in Figure 11.11, the P-P-P robotic manipulator has a cubic (or a rectangular cuboid) workspace with outer x, y, and z dimensions of Δ1xmax, Δ2ymax and Δ3zmax, respectively (the maximum prismatic joint translations).
Functional Magnetic Resonance Imaging (fMRI)
Published in Ioannis Tsougos, Advanced MR Neuroimaging, 2018
Spatial resolution of an fMRI study refers to the minimum discrimination ability between adjacent locations. As in any MRI study, it is measured by the size of a three-dimensional rectangular cuboid, the voxel. The voxel dimensions are determined by the slice thickness, and the area of the slice, as well as the matrix of the slice set by the scanning protocol. Excluding some specialized high-resolution studies, the voxel size will be typically in the 2–4 mm range dependent on the chosen contrast and the main magnetic field strength (Norris, 2015). The smaller the voxel, the fewer the neurons included, the less the blood flow, and hence, the lower the number of signals compared to larger voxels. Moreover, since scanning time is proportional to the number of voxels per slice and to the number of slices, smaller voxels are also more time consuming. In general, higher times in an MRI procedure lead to patient discomfort and loss of signal and should be avoided if possible. It is useful to realize that a 2–4-mm voxel would approximately contain a few million neurons and tens of billions of synapses, while the ideal neural activity signal would arise from the deoxyhemoglobin contribution to the BOLD phenomenon form the capillaries near the area of activity (Huettel et al., 2009). Obviously, a precise relationship between the voxel size and contrast cannot be simply calculated since it is largely dependent on the shimming outcome. Generally, matching the voxel volume to the cortical thickness—about 3 mm—can be considered a safe common practice (Bandettini et al., 1993).
Procedure for determining design accidental loads in liquified-natural-gas-fuelled ships under explosion using a computational-fluid-dynamics-based simulation approach
Published in Ships and Offshore Structures, 2022
The gas cloud geometric data are important parameters since the CFD code models fuel as vapour. In a study, the gas dispersion analysis generated 50 different gas clouds as a Q9 equivalent gas cloud volume (Nubli and Sohn 2020). The gas cloud is required for re-processing because of its inhomogeneous shape. Therefore, a Q9 equivalent gas cloud could be used to obtain a homogeneous shape gas cloud with uniform stoichiometric concentration (Hansen et al. 2013; Tam et al. 2021) and it has been standardised according to NORSOK Z-013 for a CFD-based probabilistic explosion simulation approach (NORSOK 2001). Hence, the dimensions of a gas cloud are difficult to determine. In some previous studies, the actual gas clouds were converted to equivalent gas clouds with a uniform shape such as a cube or a rectangular cuboid (Hansen et al. 2013; Kim 2016; Jin and Jang 2020). A different geometric ratio may be considered in an equivalent gas cloud (Jin and Jang 2020). In this work, a cube-shaped gas cloud was applied in the CFD simulation. Figure 3 illustrates the equivalent gas cloud shapes. The equivalent gas cloud dimensions can be determined using a cubical root as follows: where DGC denotes a gas cloud dimension such as length, width, or height. VGC is the equivalent gas cloud volume in cubic metres obtained from the Kameleon FireEx (KFX) software results.
Wood blockage and sediment transport at inclined bar screens
Published in Journal of Hydraulic Research, 2022
Isabella Schalko, Volker Weitbrecht
Natural wooden logs were used to model LW (LW is defined as logs with a diameter > 0.1 m and length > 1 m; Keller & Swanson, 1979) with a log diameter of dL = 0.01 m and log length LL = 0.15–0.20 m. The logs were irregular in shape and without branches. They were not watered prior to the test and the log density ρL amounted to 500 kg m–3 (“in-stream wood”, see Ruiz-Villanueva et al., 2016). The model LW was scaled based on recommendations by Schalko et al. (2018). LW was added in 10–50 g packages with a total mass of 200 g (≈20 logs). The amount of added LW is normalized as the relative LW volume Vs,rel, required to block an idealized rectangular cuboid of B × ho × ho: The solid LW volume Vs can be determined based on the mass of the LW accumulation with ρL = 500 kg m–3 (multiplied with λ3 for prototype conditions).
Evaluation of two low-cost PM monitors under different laboratory and indoor conditions
Published in Aerosol Science and Technology, 2020
Ruikang He, Taewon Han, Daniel Bachman, Dominick J Carluccio, Rudolph Jaeger, Jie Zhang, Sanjeevi Thirumurugesan, Clinton Andrews, Gediminas Mainelis
The AEC setup is shown in Figure 1. The AEC was retrofitted with the appropriate plumbing and wiring for calibration applications. The testing was performed under ambient conditions at the outdoor test facility of CH Technologies. The AEC is constructed of 316 stainless steel sidewalls and polycarbonate door panels. It has a shape of a rectangular cuboid with a pyramid-shaped expansion space at its bottom. The cuboid's internal dimensions are 0.6 m wide x 1.2 m deep x 1.2 m high (860 L), while the total internal volume is 1000 L. The chamber was operated at a negative pressure of ∼1-inch H2O. One horizontal end of a T-connector, equipped with a HEPA filter, provided filtered dilution air for the chamber. A 4-jet Blaustein Atomizer (BLAM) was mounted to the opposite horizontal end of the T-connector, and the resulting aerosol was mixed with the dilution air and delivered into the chamber. The BLAM was operated at 5 L/min aerosolization flow. A uniform aerosol mixing was assured with a Stairmand disk positioned below the inlet (Moss and Briant 1983). Aerosol mixing was further enhanced with two 5-inch computer fans on opposing sides of the chamber. The aerosol was exhausted by a vacuum pump and passed through a filter before being vented to outside. Here, a variable DC supply and centrifugal blower were set to deliver a 135 L/min flow rate.