Observation of the Relationship between Ocean Bathymetry and Acoustic Bearing-Time Record Patterns Acquired during a Reverberation Experiment in the Southwestern Continental Margin of the Ulleung Basin, Korea

We observed a distinct drop-off region in the bearing-time record of acoustic reverberation data acquired from the south-western continental margin of the Ulleung Basin, East Sea, in the summer of 2015. 3 kHz continuous waves with pulse lengths of 0.1, 0.3, and 1.0 s were used as source pulses, with an R/V Cheonghae vessel towing a variable depth source and a triplet towed array toward the deep sea from shallow water. The observed pattern changed as the R/V Cheonghae moved across the continental slope further into the sea. This pattern arises as a result of the downward-refracted beams in the 1/2 convergence zone interacting with the soft bottom. In addition, the boundary of the drop-off region was modeled with the two-way maximum travel time of the first bottom-reflected rays using the bathymetry model of the General Bathymetric Chart of the Oceans, 2020. Some discrepancies were observed when comparing the modeled curve to the measured results, and the inaccuracy of the bathymetry model on the continental slope could be the main cause of these discrepancies. This pattern could be useful for bathymetry mapping, as well as estimations of source and receiver configurations.

Marineda Footbridge in A Coruña (Spain)

<p>Designed with smooth and slender forms, Marineda footbridge in A Coruña (Spain) is a composite structure for pedestrians and cyclists that solves the access to one of the largest shopping centers in Spain, flying above a high-traffic highway.</p><p>The maximum deck height and the geometry in plan were established by the necessary vertical clearance over the highway and the situation of the starting and end points. In this way, and with the idea of avoiding structural elements over the deck to minimize visual impact, a three-span curved slender beam was designed. The main span is 85.8 meters long and comprises a composite airtight box-girder deck with variable depth from 1.75 meters near piers to 1.00 meter in midspan section. The two lateral spans, one on each side, are formed by a post-tensioned voided slab rigidly connected to pier and abutment, and with a strut element underground forming a rigid frame. In these spans the maximum deck height is 1.90 meters and the minimum is 1.00 meter. The deck width is 4.00 meters to accommodate both cyclists and pedestrians and has a transverse slope of 1.5% from the centerline to each side.</p><p>The curved geometry in plan, with a radius of 55 meters, and the stiffness of the lateral spans allow for an integral structure design without joints, that, along with the slenderness of the main span, give an unique appearance to the footbridge.</p>

Free flexural vibrations of homogeneous beams with symmetrically variable depths

The subject of the paper are homogeneous beams of symmetrically variable depth and bisymmetrical cross sections. Free flexural vibrations of these beams are analytically and numerically studied. Based on Hamilton’s principle, the differential equations of motion of these beams are obtained. The equations of motion are analytically solved with consideration of the bending lines of these beams subjected to their own weight. The fundamental natural frequency for exemplary beams is derived and presented in Tables and Figures.

Development and Laboratory Evaluation of an Online Controlling Algorithm for Precision Tillage

Soil compaction management relies on costly annual deep tillage. Variable-depth tillage or site-specific tillage modifies the physical properties of the soil at the required zones for the growth of crops. In this study, a depth control system was designed for the subsoiler of the tillage at various depths. For this purpose, an algorithm was written to investigate the subsoiler location and soil compaction. A program was also developed to implement this algorithm using Kinco Builder Software to control the subsoiler depth, which was evaluated on the experimental platform. In this study, four compression sensors were used at a distance of 10 cm up to a depth of 40 cm on the blade mounted at the front of the tractor. The data of these sensors were used as the input and compared with the pressure baseline limit (2.07 MPa), and with the priority to select the greater depth, the depth of subsoiler was determined. At all three modes of sensor activation (single, collective, and combined), this system was able to operate the hydraulic system of the tractor and place the subsoiler at the desired depth through the use of the position sensors.