Bond graph formulation of an optimal control problem for linear time invariant systems

A recent communication has proposed a conjectural procedure for representing a category of optimal control problems in bond graph language [W. Marquis-Favre, B. Chereji, D. Thomasset, S. Scavarda, Bond graph representation of an optimal control problem: the dc motor example, in: ICBGM’05 International Conference of Bond Graph Modelling and Simulation, New Orleans, USA, January 23-27, 2005, pp. 239-244]. This paper aims at providing a fundamental theory for proving the effectiveness of this procedure. The class of problem that the procedure can deal with has been extended. Its application was formerly restricted to linear time invariant siso system. The systems considered now are linear time invariant mimo systems. The optimization objective is the minimization of dissipation and input. The developments concerning the optimal control problem are based on the Pontryagin maximum principle and the proof of the effectiveness of the procedure makes a broad use of the port-Hamiltonian concept. As a result, the bond graph representation of the given optimization problem enables the analytical system, which provides the optimal solution, to be derived. The work presented in this paper is the first step in research with perspectives towards formulating dynamic optimization problems in bond graph and, towards coupling this formulation with a sizing methodology using bond graph language and a state-space inverse model approach. This sizing methodology, however, is not the topic of this paper and thus is not presented here.     

The LRXs-RALFs-FER module controls plant growth and salt stress responses by modulating multiple plant hormones

Salt stress is a major environmental factor limiting plant growth and productivity. We recently discovered an important new salt tolerance pathway, where the cell wall leucine-rich repeat extensins LRX3/4/5, the RAPID ALKALINIZATION FACTOR (RALF) peptides RALF22/23 and receptor-like kinase FERONIA (FER) function as a module to simultaneously regulate plant growth and salt stress tolerance. However, the intracellular signaling pathways that are regulated by the extracellular LRX3/4/5-RALF22/23-FER module to coordinate growth, cell wall integrity and salt stress responses are still unknown. Here, we report that the LRX3/4/5-RALF22/23-FER module negatively regulates the levels of jasmonic acid (JA), salicylic acid (SA) and abscisic acid (ABA). Blocking JA pathway rescues the dwarf phenotype of the lrx345 and fer-4 mutants, while disruption of ABA biosynthesis suppresses the salt-hypersensitivity of these mutants. Many salt stress-responsive genes display abnormal expression patterns in the lrx345 and fer-4 mutants, as well as in the wild type plants treated with epigallocatechin gallate (EGCG), an inhibitor of pectin methylesterases, suggesting cell wall integrity as a critical factor that determines the expression pattern of stress-responsive genes. Production of reactive oxygen species (ROS) is constitutively increased in the lrx345 and fer-4 mutants, and inhibition of ROS accumulation suppresses the salt-hypersensitivity of these mutants. Together, our work provides strong evidence that the LRX3/4/5-RALF22/23-FER module controls plant growth and salt stress responses by regulating hormonal homeostasis and ROS accumulation.     

Pre-service teachers’ difficulties in reasoning about sampling variability

Educational Studies in Mathematics - Past studies have documented some pre-service teachers’ (PSTs) difficulties in reasoning about sampling variability. This study adds to the body of...     

Scale of spectators’ motivations at soccer events

There are motivation sports events attending measuring tools, although so far these instruments have only been able to provide a limited explanation for attendance, which means that more sophisticated, useful scales are required. The aim of this research is to provide more efficient tool to measure the motivations of soccer events attendance. With this aim, a 14-item scale has been developed to measure the motivations that have been identified in a comprehensive review of specialized marketing literature. This scale, was used during a soccer event, showed a good global adjustment, internal consistency and validity, and found the following four dimensions explained 67% of variance in attendance: excitement, aesthetics, escape and connections to the team and its environment.     

Comprensión lectora: Modelos,entrenamiento y evaluación

Resumen

En el presente artículo se examinan las bases cognitivas de la comprensión lectora y las implicaciones de los conocimientos actuales sobre esta habilidad para la investigación, la enseñanza y la evaluación. En particular se examinan tres tipos de modelos que pretenden explicar tanto el proceso de comprensión lectora como las diferencias individuales en esta capacidad. Se describen los distintos niveles en que la información debe ser procesada durante la lectura y los tipos de información que sujetos con distinta capacidad de comprensión lectora utilizan para inferir el significado de las palabras a partir del contexto. Finalmente se comentan las implicaciones que los hechos descritos y analizados tienen para el entrenamiento y la evaluación de la capacidad estudiada.     

Actitudes de los maestros hacia la integración escolar de niños con necesidades especiales

Resumen

Se hace un estudio de las variables que afectan a las actitudes de los maestros hacia la integración escolar de niños con necesidades especiales en dieciséis centros educativos normales de la provincia de Guipúzcoa.

No se encuentran relaciones entre las actitudes de los maestros y el sexo, la lengua materna, tipo de centro, nivel de apoyo administrativo o técnico, tiempo de contacto con los niños (tiempo de integración). Sí que se observan relaciones significativas entre las variables actitudes y las variables número de alumnos por aula, actividades extraescolares, información, diagnóstico, nivel educativo, edad de los maestros.

En general, no obstante, las actitudes tienden a ser positivas.

Se analizan y discuten los resultados y se recoge la importancia de una consideración multidimensional del estudio de las actitudes de los maestros hacia la integración escolar de niños con necesidades especiales.     

«¿Cómo conseguir que Juan realice su tarea?» Algunas ideas generales sobre la motivación de logro y su modificación

Resumen

En este artículo se describen los conceptos y mecanismos motivacionales básicos relacionados con el logro y el aprendizaje. Se explican losiconceptos de motivación extrínseca e intrínseca. Se exponen los determinantes básicos de la motivación de logro, de acuerdo con la teoría de Atkinson, y su significación para la intervención. De modo similar, se describe el concepto de atribución y se comenta el papel de las atribuciones en la conducta, así como la significación que puede tener el hecho de iniciar un proceso atribucional tras el fracaso o, por el contrario, iniciar la busqueda activa de los medios para encontrar la solución. Se subraya la necesidad de considerar las posibles repercusiones que el desarrollo cognitivo y social puede tener sobre la motivación de logro, así como la importancia de diseñar procedimientos para la identificación de los sujetos que presenten patrones atribucionales maladaptativos.     

Students’ assessment of interactive distance experimentation in nuclear reactor physics laboratory education

Laboratory experiments develop students’ skills in dealing with laboratory instruments and physical processes with the objective of reinforcing the understanding of the investigated subject. In nuclear engineering, where research reactors play a vital role in the practical education of students, the high cost and long construction time of research reactors limit their accessibility to few educational programmes around the world. The concept of the Internet Reactor Laboratory (IRL) was introduced earlier as a new approach that utilises distance education in nuclear reactor physics laboratory education. This paper presents an initial assessment of the implementation of the IRL between the PULSTAR research reactor at North Carolina State University in the USA and the Department of Nuclear Engineering at Jordan University of Science and Technology (JUST) in Jordan. The IRL was implemented in teaching the Nuclear Reactor laboratory course for two semesters. Feedback from surveyed students verifies that the outcomes attained from using IRL in experimentation are comparable to that attainable from other on-campus laboratories performed by the students.