The propagation of high peak-power laser beams in real atmospheres will be affected at long range by both linear and nonlinear effects contained therein. Arguably, J. H. Marburger is associated with the mathematical characterization of this phenomenon. This paper provides a validated set of engineering equations for characterizing the self-focusing distance from a laser beam propagating through non-turbulent air with, and without, loss as well as three source configurations: (1) no lens, (2) converging lens and (3) diverging lens. The validation was done against wave-optics simulation results. Some validated equations follow Marburger completely, but others do not, requiring modification of the original theory. Our results can provide a guide for numerical simulations and field experiments.
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http://dx.doi.org/10.1364/OE.26.003974 | DOI Listing |
Sensors (Basel)
December 2024
Department of Electronic and Electrical Engineering, Hongik University, Seoul 04066, Republic of Korea.
We analyze the communication link of an LEO satellite considering interference sources moving along various parabola-curved paths. In this situation, the location of the ground station, airborne interference source paths, and the satellite's trajectory were expressed in the East-North-Up (ENU) coordinate system. The airborne interference source path is designed using a parabola equation with a directrix parallel to the satellite's trajectory to analyze the interference situation for more diverse interference source paths, rather than using a straight path.
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December 2024
Graduate School of Information Science and Electrical Engineering, Kyushu University, Fukuoka 819-0395, Japan.
Understanding the factors that contribute to slope failures, such as soil saturation, is essential for mitigating rainfall-induced landslides. Cost-effective capacitive soil moisture sensors have the potential to be widely implemented across multiple sites for landslide early warning systems. However, these sensors need to be calibrated for specific applications to ensure high accuracy in readings.
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December 2024
Geophysical Division of China Oilfield Services Ltd., Tianjin 300451, China.
Towed streamer positioning is a vital and essential stage in marine seismic exploration, and accurate hydrophone coordinates exert a direct and significant influence on the quality and reliability of seismic imaging. Current methods predominantly rely on analytical polynomial models for towed streamer positioning; however, these models often produce significant errors when fitting to streamers with high curvature, particularly during turning scenarios. To address this limitation, this study introduces a novel multi-streamer analytical positioning method that uses a hybrid harmonic function to model the three-dimensional coordinates of streamers.
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December 2024
Laboratory of Reinforced Concrete and Seismic Design, Department of Civil Engineering, Democritus University of Thrace, 67100 Xanthi, Greece.
One of the most critical components of reinforced concrete structures are beam-column joint systems, which greatly affect the overall behavior of a structure during a major seismic event. According to modern design codes, if the system fails, it should fail due to the flexural yielding of the beam and not due to the shear failure of the joint. Thus, a reliable tool is required for the prediction of the failure mode of the joints in a preexisting population of structures.
View Article and Find Full Text PDFPolymers (Basel)
December 2024
Department of Mechanical Engineering, Federal University of Campina Grande, Campina Grande 58429-900, PB, Brazil.
Recently, the liquid composite molding technique (LCM) has been used for producing fiber-reinforced polymer composites, since it allows the molding of complex parts, presenting good surface finishing and control of the mechanical properties of the product at the end of the process. Studies in this area have been focused on resin transfer molding (RTM), specifically on the resin rectilinear infiltration through the porous preform inserted in the closed cavity neglecting the sorption effect of the polymeric fluid by the reinforcement. Thus, the objective of this work is to predict resin radial flow in porous media (fibrous preform), including the effect of resin sorption by fibers considering a one-dimensional approach.
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