Non-dimensional design approach for electrodynamic bearings

Electrodynamic bearings (EDBs) are passive magnetic bearings that exploit the interaction between eddy currents developed in a rotating conductor and a static magnetic field to generate forces. Similar to other types of magnetic suspensions, EDBs provide contactless support, thus avoiding problems with lubrication, friction and wear. The most interesting aspect of EDBs is that levitation can be obtained by passive means, hence, no electronic equipment, such as power electronics or sensors, are necessary. Despite their promising characteristics, rotors running on EDBs are still lacking a design procedure; furthermore, at present the static behavior of a bearing can only be defined by means of finite element analyses. The aim of the present paper is to present a methodology that allows performing a first approximation design without resorting to detailed FE analyses. The methodology is based on the use of non-dimensional parameters, similar to the analysis of fluid bearings (Sommerfeld number). The non-dimensional quantities are derived using dimensional analysis, and contain the main geometrical and physical parameters determining the EDBs' performance. The relation between the non-dimensional quantities characterizing the static performance of the EDB is derived using FE simulations and is presented in the form of graphs

A multi-purpose control and power electronic architecture for active magnetic actuators

This paper shows the results related with the design and implementation of a multi-purpose electronic architecture used to drive magnetic actuators by means of a three-phase independent-legs module in place of the commonly used H-bridge modules. The typical application is the magnetic actuators drive used in active magnetic bearings. The architecture is composed of a control unit with a floating point Digital Signal Processor (DSP), a power board with six independent phase legs and a carrier board to interconnect them. When more than one module is required by the application, the communication between them is guaranteed by means of CAN bus interconnection. The proposed system allows to drive two pairs of opposite electromagnets, such as those typically used to control active magnetic bearings. The study is motivated by the opportunity of reducing the amount of power and control electronic components resulting in a more straightforward, efficient and cost reduction design

Stability of a 4 degree of freedom rotor on electrodynamic passive magnetic bearings

Electrodynamic bearings exploit repulsive forces due to eddy currents to produce positive stiffness by passive means without violating the Earnshaw stability criterion. This remarkable characteristic makes this type of bearing a suitable alternative to active magnetic bearings in fields such as kinetic energy storage flywheels, turbo pumps, high speed compressors, among others. However, the suspension can become unstable due to rotating damping. To obtain deeper understanding of this instability phenomenon this paper presents the analysis of stability of a four degree of freedom (4dof) rotor supported by electrodynamic bearings. The 4dof rotor model is coupled to the dynamic model of the eddy current forces generated by the electrodynamic bearing and the stability of the complete system is analyzed. This model is used to study the stability of both cylindrical and conical whirling motion of the rotor. In addition to the well known cylindrical whirl instability the possible occurrence of conical instability is demonstrated. Finally the effects of two stabilization strategies are analyze

Model and Design of a Power Driver for Piezoelectric Stack Actuators

A power driver has been developed to control piezoelectric stack actuators used in automotive application. An FEM model of the actuator has been implemented starting from experimental characterization of the stack and mechanical and piezoelectric parameters. Experimental results are reported to show a correct piezoelectric actuator driving method and the possibility to obtain a sensorless positioning control

New products made with lignocellulosic nanofibers from Brazilian amazon forest.

Made available in DSpace on 2018-09-01T00:42:45Z (GMT). No. of bitstreams: 1 NewproductsmadewithlignocellulosicnanofibersfromBrazilianamazonforest..pdf: 1412435 bytes, checksum: dfe1edbe148c5e545ca394e9f283429e (MD5) Previous issue date: 2015-02-0

Proteomic profiling reveals the transglutaminase-2 externalization pathway in kidneys after unilateral ureteric obstruction

Increased export of transglutaminase-2 (TG2) by tubular epithelial cells (TECs) into the surrounding interstitium modifies the extracellular homeostatic balance, leading to fibrotic membrane expansion. Although silencing of extracellular TG2 ameliorates progressive kidney scarring in animal models of CKD, the pathway through which TG2 is secreted from TECs and contributes to disease progression has not been elucidated. In this study, we developed a global proteomic approach to identify binding partners of TG2 responsible for TG2 externalization in kidneys subjected to unilateral ureteric obstruction (UUO) using TG2 knockout kidneys as negative controls. We report a robust and unbiased analysis of the membrane interactome of TG2 in fibrotic kidneys relative to the entire proteome after UUO, detected by SWATH mass spectrometry. The data have been deposited to the ProteomeXchange with identifier PXD008173. Clusters of exosomal proteins in the TG2 interactome supported the hypothesis that TG2 is secreted by extracellular membrane vesicles during fibrosis progression. In established TEC lines, we found TG2 in vesicles of both endosomal (exosomes) and plasma membrane origin (microvesicles/ectosomes), and TGF-β1 stimulated TG2 secretion. Knockout of syndecan-4 (SDC4) greatly impaired TG2 exosomal secretion. TG2 coprecipitated with SDC4 from exosome lysate but not ectosome lysate. Ex vivo, EGFP-tagged TG2 accumulated in globular elements (blebs) protruding/retracting from the plasma membrane of primary cortical TECs, and SDC4 knockout impaired bleb formation, affecting TG2 release. Through this combined in vivo and in vitro approach, we have dissected the pathway through which TG2 is secreted from TECs in CKD

Therapeutical innovations and medical responsibility: What's new in oto-laryngology

On one hand the incessant and constant technological and instrumental progress in the medical fieldhas allowed to increase knowledge and to reach new objectives. On the other hand, however, it has also raised the risk linked to professional responsibility, regarding informed consent and law 24/2017 of the Italian Republic, better known as Gelli Bianco. In this work an analysis of relevant literature will be presented, followed by a study on the role of new devices on responsibility profiles in otolaryngology. According to the analysis of the Italian law and considering the weaknesses ofthe above mentioned guidelines, pending legal administrative clarifications, we believe an operational protocol can be proposed in case of application of therapeutical innovations, especially about experimental introductions. Consequently, in our opinion, the risk of incrimination persists in case of use of innovative procedures in the absence of a formal shared opinion expressed in guidelines or in good practices, which still need a satisfactory definition

Silicates as alternative pretreatment for cellulose pulp to obtain nanofibrils for application in biodegradable packaging: a technical review.

ABSTRACT Background: The production of cellulose microfibrils/nanofibrils (CMF/CNF) has attracted increasing attention in recent decades due to their excellent barrier, mechanical, and surface chemistry properties. However, large-scale industrial production of CMF/CNF has been a major challenge due to their high energy consumption, limiting their application. In this context, in recent years many studies have focused on developing pre-treatments designed to facilitate the fibrillation of CMF/CNF by reducing energy consumption during their production. This review highlights the latest advances in the use of silicates as chemical pre-treatments for CMF/CNF production, covering the main aspects related to the effects of chemical modification on the production and the properties of materials for application in biodegradable packaging. Results: Energy consumption reductions of up to 30% were achieved by pretreating cellulose pulps using silicates. In addition, the pre-treatments resulted in smaller CMF/CNF diameters and greater individualization of the nanofibrils. Studies evaluating the thermal stability, hydrophobicity, mechanical properties, and porosity of CMF/CNF pre-treated with silicates have reported promising results. The application of CMF/CNF pretreated with calcium and magnesium silicates in cardboard coating resulted in packaging with low water vapor permeability and high ductility. Conclusion: Silicates interact well with cellulose surfaces, making them a promising material for the chemical pre-treatment of CMF/CNF. Furthermore, the modification by silicates could be an interesting strategy for expanding the use of CMF/CNF in the development of new products

A role for hemopexin in oligodendrocyte differentiation and myelin formation.

Myelin formation and maintenance are crucial for the proper function of the CNS and are orchestrated by a plethora of factors including growth factors, extracellular matrix components, metalloproteases and protease inhibitors. Hemopexin (Hx) is a plasma protein with high heme binding affinity, which is also locally produced in the CNS by ependymal cells, neurons and glial cells. We have recently reported that oligodendrocytes (OLs) are the type of cells in the brain that are most susceptible to lack of Hx, as the number of iron-overloaded OLs increases in Hx-null brain, leading to oxidative tissue damage. In the current study, we found that the expression of the Myelin Basic Protein along with the density of myelinated fibers in the basal ganglia and in the motor and somatosensory cortex of Hx-null mice were strongly reduced starting at 2 months and progressively decreased with age. Myelin abnormalities were confirmed by electron microscopy and, at the functional level, resulted in the inability of Hx-null mice to perform efficiently on the Rotarod. It is likely that the poor myelination in the brain of Hx-null mice was a consequence of defective maturation of OLs as we demonstrated that the number of mature OLs was significantly reduced in mutant mice whereas that of precursor cells was normal. Finally, in vitro experiments showed that Hx promotes OL differentiation. Thus, Hx may be considered a novel OL differentiation factor and the modulation of its expression in CNS may be an important factor in the pathogenesis of human neurodegenerative disorders