Optimization of filament antennas using the Gauss-Newton method

The project of the Yagi-Uda antenna was optimized using the Gauss-Newton method. The optimization consisted of specifying value interval for directivity, front-to-back ratio and beamwidth and, starting from a pre-defined initial model, the best values for the length and spacing of the elements were determined. For the direct modeling, the method of moments on the integral Pocklington equation was used, which consisted of obtaining the values of directivity, front-to-back ratio and beamwidth from the length and spacing between known elements. The procedure was applied to the synthesis of Yagi-Uda antennas with five and six elements and the results were found to be as good as those obtained in the literature using other optimization methods.

Dynamic load simulation of the machine nodes containing interacting rollers

The article presents a dynamic model of interaction of rollers on the example of printing cylinders of an offset machine. Based on the solution of the contact problem, the interaction forces of the cylinders are determined, direct modeling of dynamic loads and vibrations is carried out, the amplitudes of vibrations and pressure changes are determined. Options for reducing loads are considered. The disadvantages of existing models of printing machines are analyzed and taken into account.

Equilibrium Charge Distribution in a Finite Chain with a Trapping Site

The paper considers the problem of the distribution of a quantum particle in a classical one-dimensional lattice with a potential well. The cases of a rigid chain, a Holstein polaron model, and a polaron in a chain with temperature are investigated by direct modeling at fixed parameters. As is known, in the one-dimensional case, a particle is captured by an arbitrarily shallow potential well with an increase of the box size. In the case of a finite chain and finite temperatures, we have quite the opposite result, when a particle, being captured in a well in a short chain, turns into delocalized state with an increase in the chain length. These results may be helpful for further understanding of charge transfer in DNA, where oxoguanine can be considered as a potential well in the case of hole transfer when for excess electron transfer it is thymine dimer.

Continuous learning of emergent behavior in robotic matter

One of the main challenges in robotics is the development of systems that can adapt to their environment and achieve autonomous behavior. Current approaches typically aim to achieve this by increasing the complexity of the centralized controller by, e.g., direct modeling of their behavior, or implementing machine learning. In contrast, we simplify the controller using a decentralized and modular approach, with the aim of finding specific requirements needed for a robust and scalable learning strategy in robots. To achieve this, we conducted experiments and simulations on a specific robotic platform assembled from identical autonomous units that continuously sense their environment and react to it. By letting each unit adapt its behavior independently using a basic Monte Carlo scheme, the assembled system is able to learn and maintain optimal behavior in a dynamic environment as long as its memory is representative of the current environment, even when incurring damage. We show that the physical connection between the units is enough to achieve learning, and no additional communication or centralized information is required. As a result, such a distributed learning approach can be easily scaled to larger assemblies, blurring the boundaries between materials and robots, paving the way for a new class of modular “robotic matter” that can autonomously learn to thrive in dynamic or unfamiliar situations, for example, encountered by soft robots or self-assembled (micro)robots in various environments spanning from the medical realm to space explorations.

Deep structure of the Grenada Basin from wide-angle seismic, bathymetric and gravity data

<p>Studying back-arc basins, where sedimentation is less deformed than in the forearc, provides complementary information about formation and tectonic evolution of subduction zones. At the Lesser Antilles subduction zone, the North and South American plates are subducting underneath the Caribbean plate at a velocity of 2 cm per year. The crescent-shaped Grenada back-arc basin is located between the Aves Ridge, which hosted the remnant Early Paleogene “Great Caribbean Arc”, and the Eocene to present Lesser Antilles Arc. In this study, based on wide-angle data, we provide constraints about lateral variations in basement thickness and velocity structure in the Lesser Antilles back-arc, and to a lesser extend in the arc and forearc domain, constraining for the first time the extent of oceanic crust in the Grenada Basin and shed light on the structure and compositions of the basin’s margins.</p><p>Three combined wide-angle and reflection seismic profiles, together with gravity and bathymetric data, were acquired in the Lesser Antilles back-arc basin. Direct modeling techniques were applied to the wide-angle seismic data in order to include shallow structures imaged by the coincident reflection seismic data. The resulting velocity models were additionally constrained by gravity modeling and synthetic seismogram calculation. The final models from direct modeling image variations in thickness and velocity structure of the sedimentary and crustal layers to a depth of up to 35 km. The sedimentary cover has a variable thickness from less than a kilometer on top of the ridges to nearly 10 km in the basin. North of Guadeloupe Island, the crust is ~20 km thick from back-arc to forearc, without significant change between the Aves Ridge, the Eocene and present Lesser Antilles volcanic arc. While based on the seismic velocities, the southern part of the basin is underlain by a 6.5-7 km thick crust of of mainly magmatic origin over a width of ~80 km, the northern part is underlain by thinned continental crust. At the western flank of the Lesser Antilles Arc, the crust is 17.5-km thick, about 5 km thinner than north of Martinique island. The velocity structure is typical of volcanic arcs or oceanic plateaus. Between Aves Ridge and the Grenada basin the crust thins in a 80-100 km wide transition zone. No anomalous high velocities indicating the presence of exhumed upper mantle material were detected at the transition zone. This narrow E-W arc-ocean transition zone suggests that opening might have proceeded in a direction highly oblique to the main convergence.</p>

Optimal Dummy Pattern Design Method for PWB Warpage Control Using the Human-Based Genetic Algorithm

In this work, a method that minimizes printed wiring board (PWB) warpage by dummy pattern design is proposed. This work suggests that dummy patterns are placed on a preset discretized location in the PWB to reduce the warpage. On each discretized candidate area, the dummy pattern can be set or unset. The warpage is numerically simulated based on direct modeling of the as-is PWB patterns to evaluate the warpage alongside the dummy pattern design set. The optimal pattern that minimizes warpage is determined using the human-based genetic algorithm where the objective function is evaluated by the structural simulation. The optimization method is realized in a spreadsheet that allows scripting language with which the input and output files of the simulation tool can be modified and read. Two different cases have been tested and the results show that the method can determine the optimal dummy patterns. The measured and simulated deflections agree well with each other. Moreover, it has been shown that certain dummy pattern designs that should reduce the warpage can be sought by the optimization.