Electric-field control of exchange bias in multiferroic epitaxial heterostructures

The magnetic exchange between epitaxial thin films of the multiferroic (antiferromagnetic and ferroelectric) hexagonal YMnO3 oxide and a soft ferromagnetic (FM) layer is used to couple the magnetic response of the FM layer to the magnetic state of the antiferromagnetic one. We will show that biasing the ferroelectric YMnO3 layer by an electric field allows control of the magnetic exchange bias and subsequently the magnetotransport properties of the FM layer. This finding may contribute to paving the way towards a new generation of electric-field controlled spintronic devices.

Electric field control of magnetism in hydrid ferromagnetic / ferroelectric materials

Väisälän palkinnon 2012 saaja.

Proposed dams on Missouri river watershed? Navigation, hydro-electric, flood control, irrigation

Mode of access: Internet.

Uma metodologia para o controle de seguranca dinamica de sistemas de energia eletrica

This work presents an algorithm for the security control of electric power systems using control actions like generation reallocation, determined by sensitivity analysis (linearized model) and optimization by neural networks. The model is developed taking into account the dynamic network aspects. The preventive control methodology is developed by means of sensitivity analysis of the security margin related with the mechanical power of the system synchronous machines. The reallocation power in each machine is determined using neural networks. The neural network used in this work is of Hopfield type. These networks are dedicated electric circuits which simulate the constraint set and the objective function of an optimization problem. The advantage of using these networks is the higher speed in getting the solutions when compared to conventional optimization algorithms due to the great convergence rate of the process and the facility of the method parallelization. Then, the objectives are: formulate and investigate these networks implementations in determining. The generation reallocation in digital computers. Aiming to illustrate the proposed methodology an application considering a multi-machine system is presented.

Market Study of Electric Drive Motion Control Business

Tämän diplomityön tavoitteena oli tutkia älykkäiden paikoituskäyttöjen markkinoita ja liiketoimintamalleja. Työn pääongelmina oli määritellä alalla käytössä olevaa terminologiaa, määrittää markkinoiden koko paikoitusominaisuudet omaaville kolmivaihetaajuusmuuttajille, tutkia viiden alalla toimivan paikoituskäyttötoimittajan liiketoimintarakenteita ja tuotteita teknisestä näkökulmasta sekä esitellä kaksi teollisuuden käyttökohdetta paikoituskäytölle. Työn sisältö voidaan jakaa neljään eri osioon. Terminologian määrittely- ja markkinatutkimusosiot perustuvat pääasiassa kirjallisuustutkimukseen. Paikoituskäyttöjen toimittajia sekä niiden tuotteita käsittelevä osuus perustuu kirjallisuustutkimukseen sekä teknisiin esitteisiin ja manuaaleihin. Paikoituskäyttöjen sovellusesimerkit on selvitetty haastatteluin. Työ painottuu paikoituskäyttötoimittajien tuotteiden, tuoteominaisuuksien ja tuotetarjonnan tarkasteluun. Työn tuloksena on määritelty paikoituskäyttöjen liiketoiminnan tärkeimmät termit, paikoituskäyttöjen markkinoiden koko sekä markkinoiden koko paikoitusominaisuudet omaavalle kolmivaihetaajuusmuuttajalle. Alalla toimivien paikoituskäyttötoimittajien liiketoimintarakenne on selvitetty, jonka mukaan toimittajat on profiloitu komponentti-, komponenttipaketti-, toimialakeskeisiksi tai automaatiotoimittajiksi. Toimittajien paikoituskäyttötuotteet on luokiteltu viiteen eri luokkaan niiden teknisten ominaisuuksien perusteella. Lisäksi paikoituskäyttöjen suorituskyvyt on selvitetty säätimien momentti-, nopeus-, ja paikoituslaskenta-aikatasojen sekä kenttäväyläliityntöjen suhteen. Työssä kuvatut vanerinsorvausprosessi sekä FMS -materiaalinkäsittelyprosessi esittävät paikoituskäyttöjen potentiaalisia sovelluskohteita.

Implementation of a DC-DC converter with variable structure control of switched systems

This paper presents a control method for a class of continuous-time switched systems, using state feedback variable structure controllers. The method is applied to the control of a two-cell dc-dc buck converter and a control circuit design using the software PSpice is proposed. The design is based on Lyapunov-Metzler-SPR systems and the performance of the resulting control system is superior to that afforded by a recently-proposed alternative sliding-mode control technique. The dc-dc power converters are very used in industrial applications, for instance, in power systems of hybrid electric vehicles and aircrafts. Good results were obtained and the proposed design is also inexpensive because it uses electric components that can be easily found for the hardware implementation. Future researches on the subject include the hardware validation of the dc-dc converter controller and the robust control design of switched systems, with structural failures. © 2011 IEEE.

Low-cost PWM speed controller for an electric mini-baja type vehicle

This paperwork presents a Pulse Width Modulation (PWM) speed controller for an electric mini-baja-type car. A battery-fed 1-kW three-phase induction motor provides the electric vehicle traction. The open-loop speed control is implemented with an equal voltage/frequency ratio, in order to maintain a constant amount of torque on all velocities. The PWM is implemented by a low-cost 8-bit microcontroller provided with optimized ROM charts for distinct speed value implementations, synchronized transition between different charts and reduced odd harmonics generation. This technique was implemented using a single passenger mini-baja vehicle, and the essays have shown that its application resulted on reduced current consumption, besides eliminating mechanical parts. Copyright © 2007 by ABCM.

Variable structure control of switched systems based on Lyapunov-Metzler-SPR systems

This paper presents two Variable Structure Controllers (VSC) for continuous-time switched plants. It is assumed that the state vector is available for feedback. The proposed control system provides a switching rule and also the variable structure control input. The design is based on Lyapunov-Metzler (LM) inequalities and also on Strictly Positive Real (SPR) systems stability results. The definition of Lyapunov-Metzler-SPR (LMS) systems and its direct application in the design of VSC for switched systems are introduced in this paper. Two examples illustrate the design of the proposed VSC, considering a plant given by a switched system with a switched-state control law and two linear time-invariant systems, that are not controllable and also can not be stabilized with state feedback. ©2008 IEEE.

Electrical and Magnetic Characterization of BSCCO and YBCO HTS Tapes for Fault Current Limiter Application

Several high temperature superconductor (HTS) tapes have been developed since the late eighties. Due to the new techniques applied for their production, HTS tapes are becoming feasible and practical for many applications. In this work, we present the test results of five commercial HTS tapes from the BSCCO and YBCO families (short samples of 200 mm). We have measured and analyzed their intrinsic and extrinsic properties and compared their behaviors for fault current limiter (FCL) applications. Electrical measurements were performed to determine the critical current and the n value through the V-I relationship under DC and AC magnetic fields. The resistance per unit length was determined as a function of temperature. The magnetic characteristics were analyzed through susceptibility curves as a function of temperature. As transport current generates a magnetic field surrounding the HTS material, the magnetic measurements indicate the magnetic field supported by the tapes under a peak current 1.5 times higher than the critical current, I(c). By pulsed current tests the recovery time and the energy/volume during a current fault were also analyzed. These results are in agreement with the data found in the literature giving the most appropriate performance conductor for a FCL device (I(peak) = 4 kA) to be used in a 220 V-60 Hz grid.

Reconfiguração e desenvolvimento do sistema de controlo de um AGV

O veículo guiado automaticamente (AGV) adquirido pelo Departamento de Engenharia Mecânica (DEM) tem vindo a ficar obsoleto devido ao hardware, que nos dias de hoje começa a dar sinais de falhas bem como falta de peças de substituição, e ao software, sendo o PLC (Programmable Logic Controller) usado muito limitado quanto às suas funções de controlo, ficando as principais tarefas de controlo do AGV a cargo de placas eletrónicas de controlo. Para promover o controlo autónomo do AGV, foi decidido retirar toda a parte de hardware que detinha o controlo do mesmo e passou a ser um novo PLC, com maior capacidade de processamento, a executar todo o tipo de controlo necessário ao funcionamento do mesmo. O hardware considerado apenas incluí, de forma resumida, os motores responsáveis pelo movimento e direção, placa de controlo de potência dos motores, placa de interface entre as saídas digitais do PLC e as entradas da placa de controlo de potência dos motores e os demais sensores necessários à deteção de obstáculos, fins de curso da direção, sensores dos postos de trabalho e avisadores de emergência. Todo o controlo de movimento e direção bem como a seleção das ações a executar passou a ficar a cargo do software programado no PLC assim como a interação entre o sistema de supervisão instalado num posto de controlo e o PLC através de comunicação via rádio. O uso do PLC permitiu a flexibilidade de mudar facilmente a forma como as saídas digitais são usadas, ao contrário de um circuito eletrónico que necessita de uma completa remodelação, tempo de testes e implementação para efetuar a mesma função. O uso de um microcontrolador seria igualmente viável para a aplicação em causa, no entanto o uso do PLC tem a vantagem de ser robusto, mais rápido na velocidade de processamento, existência de software de interface de programação bastante intuitivo e de livre acesso, facilidade de alterar a programação localmente ou remotamente, via rádio, acesso a vários protocolos de comunicação robustos como Modbus, Canbus, Profinet, Modnet, etc., e acesso integrado de uma consola gráfica totalmente programável. iv É ainda possível a sua expansão com adição de módulos de entradas e saídas digitais e/ou analógicas permitindo expandir largamente o uso do AGV para outros fins. A solução está a ser amplamente testada e validada no Laboratório de Automação (LabA) do Departamento de Engenharia Mecânica do ISEP (Instituto Superior de Engenharia do Porto), permitindo a otimização dos sistemas de controlo de direção bem como a interatividade entre o PLC e o programa de interface/supervisão do posto de trabalho.

Rapid assessment of fruit-color selection by birds using artificial fruits at local scale in Central Amazonia

Modeling clays have been used in several ecological experiments and have proved to be an important tool to variables control. The objective of our study was to determine if fruit color in isolated and grouped displays influences the fruit selection by birds in the field using artificial fruits. Data were collected in six plots distributed homogeneously in 3 km long trails with a minimum distance of 0.5 km. We used a paired experimental design to establish our experiments, so that all treatments were available to the local bird community in each plot. Overall, red was more pecked than brown and white. Isolated red and brown displays were significantly more pecked than others display. Even though our study was conducted in small spatial scales, artificial fruits appeared to be efficient in register fruit consumption attempts by bird. Although inconclusive about selective forces that sharp the dynamics of fruit color polymorphisms and choice by frugivorous birds, our findings corroborate recent studies wherein birds showed preferences by high- over low-contrast fruit signals.

Lasikuituputkien kelauslinjan automatisointi

Lasikuituputkien kelaamiseen tarkoitettu automaatio voidaan toteuttaa suorakulmaisen kolmion trigonometrian perusteella. Kelaaminen tapahtuu pyörittämällä muottia ja liikuttamalla samalla muottia sivuttain. Näin tehdessä saadaan kelattavat lasikuitulangat leviämään koko muotin leveydelle. Jos langat halutaan saada kelattua tiiviisti toistensa viereen, on muotin liikuttava tietty matka yhtä muotin pyörähdystä kohden. Matkaa kutsutaan nousuksi. Nousu riippuu lankojen muodostaman kimpun leveydestä, kelauskulmasta ja muotin säteestä. Kelauskulmalla voidaan vaikuttaa kelattavan tuotteen aksiaaliseen ja pitkittäiseen lujuuteen. Kelauskoneen automaatiojärjestelmä koostuu sähkökäytöistä, ohjaavasta yksiköstä, valvomosta ja erilaisista antureista. Eri osat yhdistetään toisiinsa väylätekniikalla. Sähkökäytöt ovat yleensä servokäyttöjä, koska niiltä vaaditaan tarkkuutta ja nopeutta. Ohjaavana yksikkönä toimii yleensä teollisuus logiikka. Anturointia tarvitaan esimerkiksi hartsin lämpötilan säätöön ja lankojen ratakireyden säätöön. Anturoinnilla ja säädöillä pyritään parantamaan kelattavan tuotteen laatua. Koneen ohjelmallinen toteutus vaatii kelauskoneen mekaniikan ja kelausprosessin ymmärtämistä. Lisäksi on huomioitava koneen käyttäjät ja heidän turvallisuus.

Dose-response curves of Lolium multiflorum biotypes resistant and susceptible to clethodim

Chemical control with herbicides, especially glyphosate, is the main method used to control ryegrass. However, the repeated use of glyphosate has selected resistant ryegrass biotypes. Thus, the ACCase inhibitor herbicides have become the main alternative to control glyphosate-resistant biotypes, being widely used by farmers in Rio Grande do Sul. Repeated use of ACCase inhibitors, in turn, have selected ryegrass biotypes resistant to this herbicide mechanism. Thus, the objective of this study was to evaluate the response of ryegrass biotypes to different clethodim rates by dose-response curves. Increasing doses (0, 12, 24, 48, 72, 96, 144 and 192 g a.i. ha-1) of the herbicide clethodim were applied at the 3-4 ryegrass leaf stage. The variables control at 14 and 28 days after treatment (DAT) and shoot dry weight were evaluated. The data were fitted by nonlinear regression log-logistic and C50 and GR50 were calculated based on the equation. The resistance factor was obtained by the ratio of C50 or GR50 of the resistant biotype by matching the susceptible biotype. Based on the equation parameters, the doses of GR50 64.7 and 234.5 g a.i. ha-1 clethodim and C50 11.2 and 172.1 g a.i. ha-1 clethodim were obtained, at 28 DAT for the susceptible and resistant biotypes, respectively. The ryegrass biotype denominated Cotril is resistant to clethodim, being controlled with a dose 15.3 times greater than that of the susceptible biotype, and a 50% reduction of this biotype occurs with a dose 3.62 times higher than that of the susceptible one.

La entrevista cognitiva : avances en psicología del testimonio.

1. Estudiar las diferencias entre los relatos de un mismo suceso obtenidos: a. Cuando los testigos son entrevistados utilizando la entrevista estandar (EE), y b. Cuando lo son, empleando la entrevista cognitiva (EC). 2. Estudiar las diferencias entre declaraciones verdaderas y falsas en relación con los criterios del control de la realidad de los recuerdos en función de la técnica de entrevista (EC-EE) empleada. Estuvo compuesta por 73 estudiantes de psicología. De ellos, 52 eran mujeres y 21 varones. La edad media era de 19 años. Se utilizó un diseño factorial 2x2 con las siguientes variables: variable independiente: 1. Tipo de entrevista, con dos niveles: verdadera y falsa. Variables dependientes: exactitud; errores; confabulaciones; presencia de las categorías: información contextual, detalles sensoriales e información idiosincrática; variables estilométricas; longitud de las declaraciones y explicaciones. Variables control: sexo de los testigos y edad. 1. La entrevista cognitiva se muestra como un amplificador de diferencias entre los relatos verdaderos y falsos, tanto en lo que se refiere al número de detalles exactos que proporcionan, como a las confabulaciones que contienen. 2. Las declaraciones obtenidas con la EC fueron más extensas y con mayor número de explicaciones que las obtenidas con la EE. Sin embargo, las declaraciones verdaderas y falsas no se diferencian significativamente en ninguna de las dos variables estilométricas. 3. Las declaraciones verdaderas contenían más información contextual y más detalles sensoriales que las falsas, a la vez que la EC volvió a comportarse como un amplificador de las diferencias entre ambos tipos de relatos. No obstante, las declaraciones falsas no contenían un número de alusiones a procesos internos significativamente superior que las verdaderas. 1. La entrevista cognitiva es un procedimiento de obtención de información más recomendable que la entrevista estandar, ya que permite obtener información más exacta. 2. Es posible diferenciar las declaraciones verdaderas de las falsas en función de los criterios de control de realidad de los recuerdos, con la excepción de la información interna. 3. La entrevista cognitiva permite una mayor discriminación entre los relatos verdaderos y falsos de los testigos que la entrevista estandar, lo que en su día podría ser beneficioso para la detección de la mentira. 4. La EC, basada en el conocimiento que de la memoria posee la psicología experimental, se presenta como una alternativa a los sistemas tradicionales de entrevistas empleados hasta ahora por los distintos actores del proceso legal.

Aspectos integradores de la teoría de la indefensión aprendida de M.E.P. Seligman.

Conocimiento de aspectos que han influido patológicamente en la historia del hombre y que actualmente no sólo permanecen, sino que se ven agravados por la situación actual. De 200 sujetos de Psicología se seleccionaron 72. Variables independientes: 1) Tipo de tarea. 2) Situación inescapable. 3) Información verbal. Variables dependientes: 1) Rendimiento. 2) Experiencias. Variables control: 1) Sexo. 2) Edad. Cuestionario de atribuciones de Seligman; tarea de recuerdo (dos listas de 30 palabras cada una); anagramas, manómetro, instrucciones, cuestionario MMPI (escala depresión). ANOVAS de dos modos de clasificación, con medidas repetidas; diferencias de medias y estadísticos no paramétricos (prueba de Wilcoxon y de Mann Whitney). La variable dependiente rendimiento medida a través de una tarea de recuerdo fue la que dio lugar a unos rendimientos más claros y significativos. Esta investigación consigue una innovación al incurrir un grupo de 'indefensión grupal' y dar hasta cierto punto la razon a Seligman cuando afirma que en cuestion de rendimiento, un depresivo y una persona sometida a indefensión son similares (Seligman, 1974-75).