Growth, characterization and applications of metal oxides on graphitic systems

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física Aplicada. Fecha de lectura: 03-10-201

PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented

The reproducibility crisis in science from the perspective of thin film deposition: an unexpected approach

The publication of scientific results in all disciplines, and in particular in Material Science, has geometrically increased in the last decades. Although the quality of the published results seems to follow the same trend, the feeling that we could be facing a reproducibility crisis has become extended within the scientific community. We discuss this issue in relation to thin film deposition techniques such as atomic layer deposition, which should not present deviations on the reported results due to its self-limiting nature. In particular, we put the focus on the necessity of a multipolar approach that takes into account also the global environment in which researchers perform their wor

Are you ready for retirement? The influence of values on membership in voluntary organizations in midlife and old age

Membership in voluntary organizations is associated with individual and social benefits. Due to the negative consequences of the global pandemic on older people, and the governmental challenges posed by population aging, voluntary membership is of great importance to society. To effectively promote volunteering among older people, it is necessary to understand the determinants of voluntary membership. This study analyses the influence of individual values—secular/traditional and survival/selfexpression– on voluntary membership among European adults (N = 31,985). Specifically, it examines which values orient two age groups (middle age: 50–64 and old age: 65–79), as well as men and women toward a certain type of association (Social Awareness; Professional and Political; Education and Leisure; Religion). The sample of 31,985 comprises 60% of adults aged 50–64 and 40% aged 65–79; of which 56% are women and 44% men. The empirical estimation considers different levels of data aggregation: individual, national and welfare system, therefore multilevel analysis is used as an analytical strategy. Individual-level variables from the Integrated Values Survey (2005/09, 2010/14, and 2017/20) and nationallevel variables (Gini Index and Gross Domestic Product Per Capita) from the World Bank and Eurostat are used. The results indicate that traditional and self-expression values promote membership in voluntary organizations in general more than secular and survival values. However, there are differences according to the type of organization. Furthermore, values are found to moderate the effect of age and gender on voluntary membership.Gobierno de Aragon CSO2017-82110-RSpanish Government PRE2018-083981State Research Agency BYCS S16_17

USJ Herbarium of Costa Rica: history and contributions

En 2011 el Herbario USJ de Costa Rica cumplió 80 años y llegó a 100 000 especímenes de todos los taxa que estudia la botánica. Se anotan datos y cifras sobre historia, fundadores y contribuciones de USJ al conocimiento florístico de Costa Rica.In 2011 the Herbarium USJ of the University of Costa Rica became 80 years old and came up with 100 000 specimens of all the taxa that traditional botany studies. Data and figures on the history, the founders, and contributions of USJ to the knowledge of Costa Rican flora are summarized.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Sobre un opus magnum de la orquideología neotropical: Hágsater, E. & L. Sánchez Saldaña (Eds.). (2004). Icones Orchidacearum, Fasc. 7, The genus Epidendrum, part 4. “A fourth century of new species in Epidendrum”

Se analiza brevemente la obra referida y se compara con otras de su mismo tipo. Se incluyen reflexiones sobre el uso del latín y del griego en botánica, así como sobre el futuro de la orquideología neotropical.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

The flowering of Australia’s Rainforests; a plant and pollination miscellany

Se comenta y describe el libro "The flowering of Australia’s Rainforests; a plant and pollination miscellany" (2010), principalmente sobre la ecología de la polinización en los bosques lluviosos australianos.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

En busca de Karl Hoffmann

Se comenta y analiza el libro biográfico escrito por Luko Hilje "Karl Hoffmann: naturalista, médico y héroe nacional" (Heredia, Costa Rica: INBio, 2006).UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Seed dormancy and germination of Enterolobium cyclocarpum (Fabaceae): Results of an unpublished work and an unsuccessful experiment

En Costa Rica, se determinó que para reproducir la especie arbórea Enterolobium cyclocarpum (Fabaceae), las semillas seleccionadas deben tener una masa de 0,7 a 1,0 g. En general, mayor masa del fruto implica mayor masa de semillas viables, de modo que frutos más grandes podrán contener las mejores semillas. Algunas semillas de esta especie germinaron después de 13 años en reposo. Ahora existe evidencia de que las semillas de una cosecha dada están programadas para germinar en tiempos diferentes, lo que revela una estrategia reproductiva ventajosa a mediano y largo plazo.In Costa Rica, it was determined that in order to reproduce the tree species E. cyclocarpum, selected seeds might weigh 0,7 to 1,0 g. In general, the weightiest fruits have the greatest mass of viable seeds, so that these fruits might contain the better seeds to be selected. Some seeds of this species germinated after 13 years of dormancy. Now there is evidence that the seeds of a particular crop are predeterminate to germinate in different times, this fact revealing a mid- and long-term advantageous reproductive strategy.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de BiologíaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Jardín Botánico Lankester (JBL