A Chaotic Approach of Differential Evolution Optimization Applied to Loudspeaker Design Problem

Over the past few years, the field of global optimization has been very active, producing different kinds of deterministic and stochastic algorithms for optimization in the continuous domain. These days, the use of evolutionary algorithms (EAs) to solve optimization problems is a common practice due to their competitive performance on complex search spaces. EAs are well known for their ability to deal with nonlinear and complex optimization problems. Differential evolution (DE) algorithms are a family of evolutionary optimization techniques that use a rather greedy and less stochastic approach to problem solving, when compared to classical evolutionary algorithms. The main idea is to construct, at each generation, for each element of the population a mutant vector, which is constructed through a specific mutation operation based on adding differences between randomly selected elements of the population to another element. Due to its simple implementation, minimum mathematical processing and good optimization capability, DE has attracted attention. This paper proposes a new approach to solve electromagnetic design problems that combines the DE algorithm with a generator of chaos sequences. This approach is tested on the design of a loudspeaker model with 17 degrees of freedom, for showing its applicability to electromagnetic problems. The results show that the DE algorithm with chaotic sequences presents better, or at least similar, results when compared to the standard DE algorithm and other evolutionary algorithms available in the literature.

Non-Dominated Sorting Genetic Algorithm Based on Reinforcement Learning to Optimization of Broad-Band Reflector Antennas Satellite

This paper aims to provide an improved NSGA-II (Non-Dominated Sorting Genetic Algorithm-version II) which incorporates a parameter-free self-tuning approach by reinforcement learning technique, called Non-Dominated Sorting Genetic Algorithm Based on Reinforcement Learning (NSGA-RL). The proposed method is particularly compared with the classical NSGA-II when applied to a satellite coverage problem. Furthermore, not only the optimization results are compared with results obtained by other multiobjective optimization methods, but also guarantee the advantage of no time-spending and complex parameter tuning.

Bat-Inspired Optimization Approach for the Brushless DC Wheel Motor Problem

This paper presents a metaheuristic algorithm inspired in evolutionary computation and swarm intelligence concepts and fundamentals of echolocation of micro bats. The aim is to optimize the mono and multiobjective optimization problems related to the brushless DC wheel motor problems, which has 5 design parameters and 6 constraints for the mono-objective problem and 2 objectives, 5 design parameters, and 5 constraints for multiobjective version. Furthermore, results are compared with other optimization approaches proposed in the recent literature, showing the feasibility of this newly introduced technique to high nonlinear problems in electromagnetics.

Multiobjective Biogeography-Based Optimization Based on Predator-Prey Approach

Biogeography is the science that studies the geographical distribution and the migration of species in an ecosystem. Biogeography-based optimization (BBO) is a recently developed global optimization algorithm as a generalization of biogeography to evolutionary algorithm and has shown its ability to solve complex optimization problems. BBO employs a migration operator to share information between the problem solutions. The problem solutions are identified as habitat, and the sharing of features is called migration. In this paper, a multiobjective BBO, combined with a predator-prey (PPBBO) approach, is proposed and validated in the constrained design of a brushless dc wheel motor. The results demonstrated that the proposed PPBBO approach converged to promising solutions in terms of quality and dominance when compared with the classical BBO in a multiobjective version.

Using Equivalent Emission Sources to Evaluate the Coupling Between Components

The electromagnetic interference between the electronic systems or their components influences the performance of the systems. For that reason, it is important to model these interferences in order to optimize the position of the systems or their components. In this paper, a method is proposed to construct the equivalent emission source models of systems. The proposed method is based on the multipolar expansion by representing the radiated emission of generic structures in a spherical reference (r, theta, phi). Some results are presented illustrating our method.

Magnetic Properties of γ - Fe2O3 Nanoparticles at the Verge of Nucleation Process.

A low-energy new method based in a one-step synthesis at room temperature produces very small maghemite nanopar ticles. The fast neutralization reaction (co-precipitation) of a ferric solution (FeCl3 aqueous) in a basic medium (NH4OH concentrated) produces an intermediate phase, presumably two-line ferrihydrite, that in oxidizing conditions is transformed to maghemite nanopar ticles. That “primordial soup” is characterized by small atom arrangements that are the base for maghemite tiny crystals. The final product of the reaction was characterized by X-ray diffraction, high-resolution transmission electron microscopy, X-ray absorption fine structure, Mössbauer spectroscopy, and magnetometry.

Investigations on maar-diatreme volcanoes by inversion of magnetic and gravity data from the Eifel area, Germany

A study of maar-diatreme volcanoes has been perfomed by inversion of gravity and magnetic data. The geophysical inverse problem has been solved by means of the damped nonlinear least-squares method. To ensure stability and convergence of the solution of the inverse problem, a mathematical tool, consisting in data weighting and model scaling, has been worked out. Theoretical gravity and magnetic modeling of maar-diatreme volcanoes has been conducted in order to get information, which is used for a simple rough qualitative and/or quantitative interpretation. The information also serves as a priori information to design models for the inversion and/or to assist the interpretation of inversion results. The results of theoretical modeling have been used to roughly estimate the heights and the dip angles of the walls of eight Eifel maar-diatremes — each taken as a whole. Inversemodeling has been conducted for the Schönfeld Maar (magnetics) and the Hausten-Morswiesen Maar (gravity and magnetics). The geometrical parameters of these maars, as well as the density and magnetic properties of the rocks filling them, have been estimated. For a reliable interpretation of the inversion results, beside the knowledge from theoretical modeling, it was resorted to other tools such like field transformations and spectral analysis for complementary information. Geologic models, based on thesynthesis of the respective interpretation results, are presented for the two maars mentioned above. The results gave more insight into the genesis, physics and posteruptive development of the maar-diatreme volcanoes. A classification of the maar-diatreme volcanoes into three main types has been elaborated. Relatively high magnetic anomalies are indicative of scoria cones embeded within maar-diatremes if they are not caused by a strong remanent component of the magnetization. Smaller (weaker) secondary gravity and magnetic anomalies on the background of the main anomaly of a maar-diatreme — especially in the boundary areas — are indicative for subsidence processes, which probably occurred in the late sedimentation phase of the posteruptive development. Contrary to postulates referring to kimberlite pipes, there exists no generalized systematics between diameter and height nor between geophysical anomaly and the dimensions of the maar-diatreme volcanoes. Although both maar-diatreme volcanoes and kimberlite pipes are products of phreatomagmatism, they probably formed in different thermodynamic and hydrogeological environments. In the case of kimberlite pipes, large amounts of magma and groundwater, certainly supplied by deep and large reservoirs, interacted under high pressure and temperature conditions. This led to a long period phreatomagmatic process and hence to the formation of large structures. Concerning the maar-diatreme and tuff-ring-diatreme volcanoes, the phreatomagmatic process takes place due to an interaction between magma from small and shallow magma chambers (probably segregated magmas) and small amounts of near-surface groundwater under low pressure and temperature conditions. This leads to shorter time eruptions and consequently to structures of smaller size in comparison with kimberlite pipes. Nevertheless, the results show that the diameter to height ratio for 50% of the studied maar-diatremes is around 1, whereby the dip angle of the diatreme walls is similar to that of the kimberlite pipes and lies between 70 and 85°. Note that these numerical characteristics, especially the dip angle, hold for the maars the diatremes of which — estimated by modeling — have the shape of a truncated cone. This indicates that the diatreme can not be completely resolved by inversion.

Paleomagnetic and rock magnetic properties of IODP Expedition 318 cores

The Integrated Ocean Drilling Program Expedition 318 to the Wilkes Land margin of Antarctica recovered a sedimentary succession ranging in age from lower Eocene to the Holocene. Excellent stratigraphic control is key to understanding the timing of paleoceanographic events through critical climate intervals. Drill sites recovered the lower and middle Eocene, nearly the entire Oligocene, the Miocene from about 17 Ma, the entire Pliocene and much of the Pleistocene. The paleomagnetic properties are generally suitable for magnetostratigraphic interpretation, with well-behaved demagnetization diagrams, uniform distribution of declinations, and a clear separation into two inclination modes. Although the sequences were discontinuously recovered with many gaps due to coring, and there are hiatuses from sedimentary and tectonic processes, the magnetostratigraphic patterns are in general readily interpretable. Our interpretations are integrated with the diatom, radiolarian, calcareous nannofossils and dinoflagellate cyst (dinocyst) biostratigraphy. The magnetostratigraphy significantly improves the resolution of the chronostratigraphy, particularly in intervals with poor biostratigraphic control. However, Southern Ocean records with reliable magnetostratigraphies are notably scarce, and the data reported here provide an opportunity for improved calibration of the biostratigraphic records. In particular, we provide a rare magnetostratigraphic calibration for dinocyst biostratigraphy in the Paleogene and a substantially improved diatom calibration for the Pliocene. This paper presents the stratigraphic framework for future paleoceanographic proxy records which are being developed for the Wilkes Land margin cores. It further provides tight constraints on the duration of regional hiatuses inferred from seismic surveys of the region.

Petrography and geochemical composition of the Atlantis II Fracture Zone

SeaBeam echo sounding, seismic reflection, magnetics, and gravity profiles were run along closely spaced tracks (5 km) parallel to the Atlantis II Fracture Zone on the Southwest Indian Ridge, giving 80% bathymetric coverage of a 30- * 170-nmi strip centered over the fracture zone. The southern and northern rift valleys of the ridge were clearly defined and offset north-south by 199 km. The rift valleys are typical of those found elsewhere on the Southwest Indian Ridge, with relief of more than 2200 m and widths from 22 to 38 km. The ridge-transform intersections are marked by deep nodal basins lying on the transform side of the neovolcanic zone that defines the present-day spreading axis. The walls of the transform generally are steep (25°-40°), although locally, they can be more subdued. The deepest point in the transform is 6480 m in the southern nodal basin, and the shallowest is an uplifted wave-cut terrace that exposes plutonic rocks from the deepest layer of the ocean crust at 700 m. The transform valley is bisected by a 1.5-km-high median tectonic ridge that extends from the northern ridge-transform intersection to the midpoint of the active transform. The seismic survey showed that the floor of the transform contains up to 0.5 km of sediment. Piston-coring at two locations on the transform floor recovered more than 1 m of sand and gravel, which appears to be turbidites shed from the walls of the fracture zone. Extensive dredging showed that more than two-thirds of the crust exposed in the transform valley and its walls were plutonic rocks, principally gabbros and residual mantle peridotites. In contrast, based on dredging and seafloor morphology, only relatively undisrupted pillow basalt flows have been exposed on crust of the same age spreading away from the transform. Magnetic anomalies are well defined out to 11 m.y. over the flanking transverse ridges and transform valley, even where layer 2 appears to be absent. The total opening rate is 1.6 cm/yr, but the arrangement of the anomalies indicates that the spreading for each ridge is asymmetric, with the ridge flanks facing the transform spreading at a rate of 1.0 cm/yr. Such an asymmetric spreading pattern requires that both the northern and southern ridges migrate away from each other at 0.2 cm/yr, thus lengthening the transform at 0.4 cm/yr for the last 11 m.y. To the north, the fracture zone valley is oriented differently from the present-day transform, indicating a paleospreading direction change at 17 m.y. from N10°E to due north-south. This change placed the transform into extension for the 11-m.y. period required for simple orthogonal ridge-transform geometry to be reestablished and produced a large transtensional basin within the transform valley. This basin was split by continued transform slip after 11 m.y., with the larger half moving to the north with the African Plate.