Modern microwave methods in solid state inorganic materials chemistry: from fundamentals to manufacturing

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Integration of Gravitational Torques in Cerebellar Pathways Allows for the Dynamic Inverse Computation of Vertical Pointing Movements of a Robot Arm

Several authors suggested that gravitational forces are centrally represented in the brain for planning, control and sensorimotor predictions of movements. Furthermore, some studies proposed that the cerebellum computes the inverse dynamics (internal inverse model) whereas others suggested that it computes sensorimotor predictions (internal forward model).This study proposes a model of cerebellar pathways deduced from both biological and physical constraints. The model learns the dynamic inverse computation of the effect of gravitational torques from its sensorimotor predictions without calculating an explicit inverse computation. By using supervised learning, this model learns to control an anthropomorphic robot arm actuated by two antagonists McKibben artificial muscles. This was achieved by using internal parallel feedback loops containing neural networks which anticipate the sensorimotor consequences of the neural commands. The artificial neural networks architecture was similar to the large-scale connectivity of the cerebellar cortex. Movements in the sagittal plane were performed during three sessions combining different initial positions, amplitudes and directions of movements to vary the effects of the gravitational torques applied to the robotic arm. The results show that this model acquired an internal representation of the gravitational effects during vertical arm pointing movements.This is consistent with the proposal that the cerebellar cortex contains an internal representation of gravitational torques which is encoded through a learning process. Furthermore, this model suggests that the cerebellum performs the inverse dynamics computation based on sensorimotor predictions. This highlights the importance of sensorimotor predictions of gravitational torques acting on upper limb movements performed in the gravitational field

A Compact UWB Monopole Antenna with Rejected WLAN Band using Split-Ring Resonator and Assessed by Analytic Hierarchy Process Method

Abstract The design of a compact microstrip line-fed Ultra-wideband (UWB) monopole antenna with a notched band characteristic is presented in this paper. The rejection frequency band occurs around 5-6 GHz, which is appropriate for wireless local area network (WLAN) applications and is obtained by a split-ring resonator on the antenna ground plane. The proposed antenna is printed on FR4 substrate material with a dielectric constant of 4.4. The dimension of the proposed antenna is 24×16×0.8 mm3. Radiating patch has a combined geometry realized by a half-circular ring and half-square ring. To achieve a proper impedance matching and increased bandwidth with VSWR ≤ 2, the study made use of an L-shaped element which was connected to the ground plane; moreover, the researchers added a split-ring resonator onto the ground plane to obtain one notched band. The comparison of the proposed antenna performance with previously presented UWB monopole antennas, was performed by using Analytic Hierarchy Process method. A good agreement was observed between simulated and experimental results

Influence of zircon particle size on conventional and microwave assisted reaction sintering of in-situ mullite–zirconia composites

Mullite-zirconia composites were fabricated by reaction sintering of ZrSiO4 and alpha-Al2O3 using conventional heating and microwave processing. The powder mixtures were prepared from sub-micron zircon powders with three different particle sizes and CIPed as coin shaped samples. The samples sintered both in a muffle furnace and microwave furnace. The open porosities, bulk and true densities were measured. Phase transformations were characterized by X-ray diffraction and microstructures were evaluated by scanning electron microscopy. The effects of zircon particle size on the in-situ transformation system and mullitization was evaluated for both methods. As a result, decreasing zircon particle size decreases the in-situ transformation temperature for 25 degrees C (1575 degrees C) in conventional heating. Microwave assisted sintering (MAS) lowers the transformation temperature at least 50 degrees C by lowering the activation energy more efficiently and gives better densification than conventional sintering. Furthermore, milling also produces structures having finer mullite grains. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved