Fernando Castaño

Revised core-shell domain model for magnetostrictive amorphous wires

The radial, circular, and axial components /spl sigma//sub r/, /spl sigma//sub /spl phi//, and /spl sigma//sub x/, of the residual stress tensor in amorphous wires made by quenching in rotating water are derived from the classical elasticity theory on the assumption that the density decreases from the wire surface (r=r/sub 0/) as r/sup 8//r/sub 0//sup 8/. After a small reduction in /spl sigma//sub x/ and a small rotation of the easy directions in the core, the current widely applied core-shell domain model is revised. In contrast to the current model, which assumes an axially magnetized core and different core radius r/sub c/ for wires with positive and negative magnetostriction, the revised model assumes: 1) a fixed core radius /spl tau//sub c//spl sim/0.75 r/sub 0/ and 2) a helical core magnetization tilting about /spl plusmn/30/spl deg/ from the axial (circular) directions for wires of positive (negative) magnetostriction. This revision is consistent with the existing basic results of domain observations and magnetic measurements and it is further supported by experiments using a new technique described in this paper.

Nd8Fe73Co5Hf2B12 strip cast alloy

Nd8Fe73Co5Hf2B12 alloys were cast as strips (thick continuous ribbons with thickness t=100–160 μm) by a chill disk melt spinning technique (vdisk=3 m/s) from a master alloy prepared by arc melting (A) and from two prealloyed components (B). Samples obtained by the B procedure revealed in the as-cast state, good magnetic properties with an unusually high value of the coercivity, Hc=10.3 kOe, for the substoichiometric Nd2Fe14B system. A high degree of structural refinement and a homogeneous dispersion of the phases are attained in sample B. The strength and type of magnetic interactions between the grains are presented by δM and irreversible susceptibility plots.

Anomalous asymmetric magneto-inductance in amorphous Co68.2Fe4.3Si12.5B15 wire with shifted hysteresis loop

The quasi-saturated hysteresis M (H ) loop of a nearly zero magnetostrictive CoFeSiB wire, annealed at 470 °C and pre-magnetized with a positive field of 16 kA m-1 , is shifted 0.23 A m-1 in the negative field direction. The magneto-inductance L (H ) curve of this wire is extremely asymmetric, exhibiting a few times greater L in the positive than in the negative H . The shifted loop can be logically explained by considering the magnetostatic interaction between positively aligned hard magnetic crystallites and a soft magnetic matrix. However, a similar explanation for the asymmetry of the magneto-inductance is invalid, and therefore this effect can be regarded as an anomalous behaviour in the technical magnetization of some multiphase ferromagnets.

New viscosimeter based on the ac field induced rotation of magnetostrictive amorphous wires

The rotation of amorphous wires under the presence of an alternating magnetic axial field of the order of several kHz is a new phenomenon discovered recently. In this work, we present a new viscosimeter based in the variation of the mechanical rotation frequency of these wires into different liquids. The rotation frequency has been found to decrease linearly with viscosity.

AC field-induced rotation of magnetostrictive wires: operating principle for field positioning microrotor sensors

The effect of a DC magnetic field on the rotation of Fe/sub 77.6/Si/sub 7.5/B/sub 15/ and Co/sub 75/Si/sub 10/B/sub 15/ amorphous wires under an axially applied AC field is investigated. The rotation frequency mainly decreases monotonically with increasing the DC field, Experimental results are exploited to propose a new family of field positioning microrotor sensors.

Ferromagnetic resonance investigation of surface anisotropy distribution in amorphous glass-covered wires

The distribution of the magnetic anisotropy in the surface region of amorphous glass-covered wires with positive and nearly zero magnetostriction is analyzed by means of microwave absorption ferromagnetic resonance (FMR). The surface layer of as-cast positive magnetostrictive amorphous glass-covered wires displays an axial anisotropy, which changes to radial after partial or complete removal of the glass cover. The as-cast nearly zero magnetostrictive amorphous glass-covered wires display a circumferential anisotropy in their surface layer, its direction being maintained even after partial or complete glass removal, but its strength slightly increases with glass removal. The results are explained by taking into account the most recent results on the domain structure of these wires, as well as the skin effect that occurs at microwave frequencies.

Magneto-impedance response in ring shaped amorphous wires

Abstract The field dependence of the high frequency impedance in ring shaped CoFeSiB amorphous wires, has been investigated. Different results were obtained depending on whether the applied dc field was produced by a current from a conductor passing through the middle of the ring, or by a magnetizing coil in which the ring was placed either parallel or perpendicular to the coil’s axis. The most sensitive magneto-impedance response was obtained in the first two cases, with a maximum magneto-impedance ratio (MIR) of about 40%. The impedance behavior in these ring shaped samples can be explained by considering the surface domain structure of the wires investigated, their non-magnetostrictive character, and the changes in the magnetization dynamics determined by the increase of both frequency and dc applied field. The possibility of using such geometrical configuration as a field-sensing device is also discussed.

Obstacle Recognition Based on Machine Learning for On-Chip LiDAR Sensors in a Cyber-Physical System

Collision avoidance is an important feature in advanced driver-assistance systems, aimed at providing correct, timely and reliable warnings before an imminent collision (with objects, vehicles, pedestrians, etc.). The obstacle recognition library is designed and implemented to address the design and evaluation of obstacle detection in a transportation cyber-physical system. The library is integrated into a co-simulation framework that is supported on the interaction between SCANeR software and Matlab/Simulink. From the best of the authors’ knowledge, two main contributions are reported in this paper. Firstly, the modelling and simulation of virtual on-chip light detection and ranging sensors in a cyber-physical system, for traffic scenarios, is presented. The cyber-physical system is designed and implemented in SCANeR. Secondly, three specific artificial intelligence-based methods for obstacle recognition libraries are also designed and applied using a sensory information database provided by SCANeR. The computational library has three methods for obstacle detection: a multi-layer perceptron neural network, a self-organization map and a support vector machine. Finally, a comparison among these methods under different weather conditions is presented, with very promising results in terms of accuracy. The best results are achieved using the multi-layer perceptron in sunny and foggy conditions, the support vector machine in rainy conditions and the self-organized map in snowy conditions.

Low-voltage rail-to-rail bulk-driven CMFB network with improved gain and bandwidth

A rail-to-rail CMOS continuous-time common-mode feedback (CMFB) network is introduced in this paper. The proposed scheme is based on the joint use of bulk-driven MOS transistors, which lead to high signal swing, and a partial positive feedback, which allows achieving enhanced DC gain and gain-bandwidth product. The proposed CMFB circuit is used to control the output voltage of a fully differential operational transconductance amplifier. Simulated results in standard 0.35-µm CMOS technology demonstrate the suitability of the approach.

Coping with Complexity When Predicting Surface Roughness in Milling Processes: Hybrid Incremental Model with Optimal Parametrization

The complexity of machining processes relies on the inherent physical mechanisms governing these processes including nonlinear, emergent, and time-variant behavior. The measurement of surface roughness is a critical step done offline by expensive quality control procedures. The surface roughness prediction using an online efficient computational method is a difficult task due to the complexity of machining processes. The paradigm of hybrid incremental modeling makes it possible to address the complexity and nonlinear behavior of machining processes. Parametrization of models is, however, one bottleneck for full deployment of solutions, and the optimal setting of model parameters becomes an essential task. This paper presents a method based on simulated annealing for optimal parameters tuning of the hybrid incremental model. The hybrid incremental modeling plus simulated annealing is applied for predicting the surface roughness in milling processes. Two comparative studies to assess the accuracy and overall quality of the proposed strategy are carried out. The first comparative demonstrates that the proposed strategy is more accurate than theoretical, energy-based, and Taguchi models for predicting surface roughness. The second study also corroborates that hybrid incremental model plus simulated annealing is better than a Bayesian network and a multilayer perceptron for correctly predicting the surface roughness.