Escalado de actuadores piezoléctricos: comparación con los tradicionales y otras nuevas tecnologías

[EN] Miniaturization is not a logical trend in actuator systems. Unlike actuators, sensors intrinsically perform more efficiently upon miniaturization. This is a logical consequence of the exchange of energy in the transduction process when applying sensors: measurement ideally should not influence the system being measured, thus the minimum exchange of energy is necessary and this intrinsically leads to miniaturization. In actuators, a transduction process is likewise established but the aim is to impose a mechanical state on a system. It is of particular interest not having this state influenced by perturbations, thus there are strong requirements on power delivered by the actuator. In view of current trends towards miniaturization, it is worth inquiring how the performance of piezoelectric actuators is affected by reducing their size. We are not concerned here with the domain of micro-actuators, i.e. actuators with sizes in the micrometer range. The analysis in this paper focuses on studying how four useful parameters for describing the performance of actuators are influenced by miniaturization: resonance frequency, force density, response time (bandwidth), stroke and energy density per cycle. In so doing, the analysis is restricted to non resonant piezoelectric actuators, i.e. stack, multimorph and inchworm actuators, but reference to other piezoelectric, emerging and traditional actuators is included for comparison.[ES] La miniaturización de los dispositivos actuadores no es una tendenca lógica de su naturaleza de operación. Al contrario que los actuadores, los sensores si presentan esta tendencia a la miniaturización fundamentada en la naturaleza de su operación: dado que en el proceso de medida el intercambio energético debe ser mínimo para no afectar el proceso de medida, cuanto menor sea el sensor menor será también su efecto sobre la medición. En el caso de los actuadores el objetivo es el opuesto, se pretende imponer el estado mecánico de un sistema y que este estado no sea perturbado por agentes externos de forma que los requisitos sobre la potencia del actuador son estrictos. En vista de la tendencia actual a la miniaturización de las aplicaciones, conviene preguntarse como se ven afectadas las características de operación de los actuadores cuando son miniaturizados. El análisis presentado en este trabajo se centra en determinar como evolucionan las características principales de los actuadores (frecuencia de resonancia, densidad de fuerza, tiempo de respuesta, máximo desplazamiento y densidad de energía por ciclo) al ser miniaturizados. El análisis se restringe a actuadores piezoelectricos no resonantes, en concreto multicapa, multimorfos y cíclicos, pero se ponen en contexto con otros actuadores piezoeléctricos, con otras tecnologías emergentes y con tecnologías tradicionales.Peer reviewe

‘Ethik und Drama bei Melanchthon’

In der vorliegenden Untersuchung über die Ethik und das Drama bei Melanchthon wird Klarheit darüber erlangt, was Melanchthon eigentlich als Tugenden sieht und wie diese gestaltet sein sollten, damit ein gutes Leben geführt werden kann. Melanchthons Reflexionen über das Drama resultieren aus seinem Interesse an der aristotelischen Tugendethik, und er vertritt den Standpunkt, dass das antike Drama dem Leser und Zuschauer die Möglichkeit gibt, sich mit Tugendethik auseinander zu setzen. Es existieren Quellen, die wenig erschlossen sind, z. B. Melanchthons Terenz-Vorwort von 1545 und seine Prologe zu Sophokles. Das als Brief an Camerarius verfasste Terenz-Vorwort von 1545 ‘De Legendis Tragoediis et Comoediis’ ist abgedruckt in dem von HEINZ SCHEIBLE herausgegebenen Briefwechsel. STEFAN RHEIN verweist in seinem Aufsatz ‘Melanchthon and Greek Literature’ auf die neu entdeckten Prologe Melanchthons in dessen ‘Interpretatio Tragoediarum’

Space Shuttle Program: Automatic rendezvous, proximity operations, and capture (category 3)

The NASA Johnson Space Center is actively pursuing the development and demonstration of capabilities for automatic rendezvous, proximity operations, and capture (AR&C) using the Space Shuttle as the active vehicle. This activity combines the technologies, expertise, tools, and facilities of the JSC Tracking and Communications Division (EE), Navigation, Control and Aeronautics Division (EG), Automation and Robotics Division (ER), and Structures and Mechanics Division (ES) of the Engineering Directorate and the Flight Design and Dynamics Division (DM) of the Mission Operations Directorate. Potential benefits of AR&C include more efficient and repeatable rendezvous, proximity operations, and capture operations; reduced impacts on the target vehicles (e.g., Orbiter RCS plume loads); reduced flight crew work loads; reduced ground support requirements; and reduced operational constraints. This paper documents the current JSC capabilities/tools/facilities for AR&C and describes a proposed plan for a progression of ground demonstrations and flight tests and demonstrations of AR&C capabilities. This plan involves the maturing of existing technologies in tracking and communications; guidance, navigation and control; mechanisms; manipulators; and systems management and integrating them into several evolutionary demonstration stages

Autonomous docking ground demonstration

The Autonomous Docking Ground Demonstration is an evaluation of the laser sensor system to support the docking phase (12 ft to contact) when operated in conjunction with the guidance, navigation, and control (GN&C) software. The docking mechanism being used was developed for the Apollo/Soyuz Test Program. This demonstration will be conducted using the 6-DOF Dynamic Test System (DTS). The DTS simulates the Space Station Freedom as the stationary or target vehicle and the Orbiter as the active or chase vehicle. For this demonstration, the laser sensor will be mounted on the target vehicle and the retroflectors will be on the chase vehicle. This arrangement was chosen to prevent potential damage to the laser. The laser sensor system, GN&C, and 6-DOF DTS will be operated closed-loop. Initial conditions to simulate vehicle misalignments, translational and rotational, will be introduced within the constraints of the systems involved

Autonomous docking ground demonstration (category 3)

The NASA Johnson Space Center (JSC) is involved in the development of an autonomous docking ground demonstration. The demonstration combines the technologies, expertise and facilities of the JSC Tracking and Communications Division (EE), Structures and Mechanics Division (ES), and the Navigation, Guidance and Control Division (EG) and their supporting contractors. The autonomous docking ground demonstration is an evaluation of the capabilities of the laser sensor system to support the docking phase (12ft to contact) when operated in conjunction with the Guidance, Navigation and Control Software. The docking mechanism being used was developed for the Apollo Soyuz Test Program. This demonstration will be conducted using the Six-Degrees of Freedom (6-DOF) Dynamic Test System (DTS). The DTS environment simulates the Space Station Freedom as the stationary or target vehicle and the Orbiter as the active or chase vehicle. For this demonstration the laser sensor will be mounted on the target vehicle and the retroreflectors on the chase vehicle. This arrangement was used to prevent potential damage to the laser. The sensor system. GN&C and 6-DOF DTS will be operated closed-loop. Initial condition to simulate vehicle misalignments, translational and rotational, will be introduced within the constraints of the systems involved. Detailed description of each of the demonstration components (e.g., Sensor System, GN&C, 6-DOF DTS and supporting computer configuration) including their capabilities and limitations will be discussed. A demonstration architecture drawing and photographs of the test configuration will be presented

Billion-atom Synchronous Parallel Kinetic Monte Carlo Simulations of Critical 3D Ising Systems

An extension of the synchronous parallel kinetic Monte Carlo (pkMC) algorithm developed by Martinez {\it et al} [{\it J.\ Comp.\ Phys.} {\bf 227} (2008) 3804] to discrete lattices is presented. The method solves the master equation synchronously by recourse to null events that keep all processors time clocks current in a global sense. Boundary conflicts are rigorously solved by adopting a chessboard decomposition into non-interacting sublattices. We find that the bias introduced by the spatial correlations attendant to the sublattice decomposition is within the standard deviation of the serial method, which confirms the statistical validity of the method. We have assessed the parallel efficiency of the method and find that our algorithm scales consistently with problem size and sublattice partition. We apply the method to the calculation of scale-dependent critical exponents in billion-atom 3D Ising systems, with very good agreement with state-of-the-art multispin simulations

Leaves and fruits preparations of Pistacia lentiscus L.: A review on the ethnopharmacological uses and implications in inflammation and infection

There is an increasing interest in revisiting plants for drug discovery, proving scientifically their role as remedies. The aim of this review was to give an overview of the ethnopharmacological uses of Pistacia lentiscus L. (PlL) leaves and fruits, expanding the search for the scientific discovery of their chemistry, anti-inflammatory, antioxidative and antimicrobial activities. PlL is a wild-growing shrub rich in terpenoids and polyphenols, the oil and extracts of which have been widely used against inflammation and infections, and as wound healing agents. The more recurrent components in PlL essential oil (EO) are represented by α-pinene, terpinene, caryophyllene, limonene and myrcene, with high variability in concentration depending on the Mediterranean country. The anti-inflammatory activity of the oil mainly occurs due to the inhibition of pro-inflammatory cytokines and the arachidonic acid cascade. Interestingly, the capacity against COX-2 and LOX indicates PlL EO as a dual inhibitory compound. The high content of polyphenols enriching the extracts provide explanations for the known biological properties of the plant. The protective effect against reactive oxygen species is of wide interest. In particular, their anthocyanins content greatly clarifies their antioxidative capacity. Further, the antimicrobial activity of PlL oil and extracts includes the inhibition of Staphylococcus aureus, Escherichia coli, periodontal bacteria and Candida spp. In conclusion, the relevant scientific properties indicate PlL as a nutraceutical and also as a therapeutic agent against a wide range of diseases based on inflammation and infections

The study of nearest- and next-nearest-neighbour magnetic interactions in seven tetragonal compounds V(IV) containing linear chains and square lattices

A new crystal chemical method was used to calculate the sign and strength not only of the nearest-neighbor (NN)interactions, but also of the next-nearest-neighbor (NNN) ones in tetragonal compounds Zn2(VO)(PO4)2 (I),(VO)(H2PO4)2 (II), (VO)SiP2O8 (III), (VO)SO4 (IV), (VO)MoO4 (V), Li2(VO)SiO4 (VI) and Li2(VO)GeO4 (VII) with similar sublattices of V4+ ions on the basis of the room-temperature structural data. The reason for difference between respective magnetic interactions characteristics of these compounds was established. It is shown that the characteristic feature of these compounds is a strong dependence of the strength of magnetic interactions and the magnetic moments ordering type on slight displacements of XO4 (X = P, Mo, Si or Ge) groups even without change of the crystal symmetry. In addition to extensively studied square lattice, other specific geometrical configurations of V4+ were discovered. These configurations can result in frustration of magnetic interactions, namely linear chains along the c-axis with competing nearest- and next-to-nearest-neighbor interactions; rectangular (in I) and triangular (in II-VII) lattices with non-equivalent nearest-to-neighbor interactions, which can be also considered as n-leg ladders; one extra square lattice in the ab-plane with longer range interactions. It was concluded that virtually all magnetic interactions in these compounds were frustrated.Comment: 16 pages, 5 figure, 1 table; numerous grammatical change