Sagnac loop in ring resonators for tunable optical filters

General filter architecture using co- and counterpropagation signals are studied. A specific configuration based on a Sagnac loop within a ring resonator is analyzed. Novel tuning, apart from conventional tuning, is achieved by changing the coupling ratio of a coupler through the adjustment of the equivalent loop length. Full equations describing the filter behavior in passive and active configurations, and simple closed-form formulas to compute the tuning, tolerance, and full-width at half-maximum are reported. The performance of these devices is discussed for their application as selective or channel-dropping ultra-narrow-band filters. The effect of losses and their dispersion properties are also discussed. These devices can be conveniently implemented, using silicon- or InP-integrated optic technology, for they have high free spectral ranges.Publicad

Problemática derivada de la aplicación por la Administración tributaria del procedimiento de comprobación de valores.

El procedimiento de comprobación de valores es uno de los procedimientos tributarios que mayor conflictividad está generando en la actualidad, especialmente por la frecuencia en que es utilizado en el Impuesto sobre Transmisiones Patrimoniales y Actos Jurídicos Documentados y en el Impuesto sobre Sucesiones y Donaciones por la Administración tributaria competente para ello. La conflictividad al respecto tiene, a nuestro juicio, causa en dos razones. La primera es el contexto de crisis económica que dificulta la liquidez tanto de Administración como de contribuyente y que obliga a la primera a una especial atención en la medición de la capacidad económica que se refleja en las operaciones gravadas por dichos impuestos. La segunda razón de la conflictividad es el recurso casi exclusivo de la Administración tributaria a métodos objetivos no siempre permeables a la variabilidad de valores de los bienes en el contexto actual. Desde esas premisas, el Trabajo Fin de Grado analiza el procedimiento de comprobación de valores estudiando el grado de discrecionalidad de la Administración en su aplicación y las garantías y medios de defensa del ciudadano en tal procedimiento. Se parte de un ineludible estudio genérico del procedimiento de valores, con especial atención a su evolución histórica que ha cambiado su concepción de un procedimiento parte de otro procedimiento a la de procedimiento autónomo. A partir de ahí, se estudia el concepto de valor y se relaciona con la base imponible para entender el objeto de la comprobación, especialmente complicado en la determinación del valor real. Con esa base teórica, se analiza los dos puntos más importantes del procedimiento de comprobación de valores: los medios de valoración y la tasación pericial contradictoria (en adelante, TPC), como respuesta. De los medios de valoración se discute, en primer lugar, la discrecionalidad de la Administración a la hora de elegir el método y se analizan, en segundo lugar, los métodos más importantes por su aplicación práctica. En segundo lugar, respecto a la tasación pericial contradictoria, se analiza como procedimiento autónomo, comparando las Comprobación de valores y determinación del valor real 4 diferencias que existen entre las distintas normas que se ocupan de ella. Como conjunto, no sólo se expone el régimen jurídico de estas cuestiones, sino que se abordan los principales problemas y se determinan soluciones que ayuden a disminuir la polémica social y la litigiosidad jurídica que este procedimiento viene suscitando

Measurements On Passive Tunable Optical Filters For DWDM

WFOPC 2002 IEEE/LEOS Workshop on Fibre and Optical Passive Components, University of Glasgow, Scotland, on 5th-6th June 2002.Measurements on a passive optical fibre tunable filter are presented. The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a coupler. The novel filter structure allows planar optical integration for having higher free spectral ranges. Novel and simple design equations for the filter parameters and the tuning process are reported. There is a good agreement between measurements and theory.Universidad Carlos III de MadridPublicad

Tunable Optical Filters Using Compound Ring Resonators for DWDM

The device is based on a loop mirror in a ring resonator. The loop mirror allows tuning by changing the coupling coefficient of a directional coupler. The loop mirror is implemented using a Sagnac configuration to have the same optical path between the signals to be interfered (copropagating and counterpropagating ones). The filter structure allows optical integration for having higher free-spectral ranges. Simple design equations for the filter parameters and the tuning are reported. Measurements on a passive optical fiber tunable filter are presented. There is a good agreement between measurements and theory.Publicad

Evaluation of Presence in Virtual Environments: Haptic Vest and User's Haptic Skills

This paper presents the integration of a haptic vest with a multimodal virtual environment, consisting of video, audio, and haptic feedback, with the main objective of determining how users, who interact with the virtual environment, benefit from tactile and thermal stimuli provided by the haptic vest. Some experiments are performed using a game application of a train station after an explosion. The participants of this experiment have to move inside the environment, while receiving several stimuli to check if any improvement in presence or realism in that environment is reflected on the vest. This is done by comparing the experimental results with those similar scenarios, obtained without haptic feedback. These experiments are carried out by three groups of participants who are classified on the basis of their experience in haptics and virtual reality devices. Some differences among the groups have been found, which can be related to the levels of realism and synchronization of all the elements in the multimodal environment that fulfill the expectations and maximum satisfaction level. According to the participants in the experiment, two different levels of requirements are to be defined by the system to comply with the expectations of professional and conventional users

Optical router for optical fiber sensor networks based on a liquid crystal cell

Optical fiber sensor networks are evolving rapidly. They are used because of the inert nature of optical fibers allowing no electromagnetic interference and safe applications in inflammable atmospheres; other relevant characteristics are their low weights and wide bandwidths as a transmission medium. In any case, it is very interesting to have specific components such as optical routers for selecting a certain path in a network with no optical to electrical and electrical to optical conversions. In this paper, we propose an all-optical router based on liquid crystals, polarizers, and a spatial split polarization beam splitter. The implemented device is designed to operate with visible light and it has been tested with plastic optical fibers. It has a crosstalk of 14 dB between selected ON channels and nonoperative OFF channels and 11-dB insertion losses. An average switch time of 100 ms is measured. The device checks the optical power level in each channel and, in case of failure, automatically switches to an operative channel while an alarm is activated.Publicad

Synthesis of asynchronous controllers using integer linear programming

A novel strategy for the logic synthesis of asynchronous control circuits is presented. It is based on the structural theory of Petri nets and integer linear programming. Techniques that are capable of checking implementability conditions, such as complete state coding, and deriving a gate netlist to implement the specified behavior are presented. These techniques can handle Petri net specifications consisting of several thousands of transitions and provide a significant speed-up compared with techniques that have previously been proposed.Peer ReviewedPostprint (published version

Aprendizaje autodirigido y entornos personales de aprendizaje de estudiantes universitarios de Costa Rica

La rápida aparición de nuevas tecnologías y el acceso cada vez más globalizado a internet promueven el uso masivo de las TIC. Al respecto, la construcción y el desarrollo de los entornos personales de aprendizaje (PLE) facilitan las habilidades requeridas para autodirigir el proceso de adquisición de conocimientos. El objetivo de este estudio es analizar cómo perciben el aprendizaje autodirigido los estudiantes universitarios de último año de carrera costarricenses, además de valorar la relación con su PLE y con el rendimiento académico. Se utilizó un diseño no experimental y transaccional de alcance correlacional. Se aplicó un cuestionario con diferentes escalas a una muestra probabilística estratificada (n = 1187) de 51 carreras de la Universidad Nacional. Los resultados muestran un nivel alto de preparación hacia el aprendizaje autodirigido. Sin embargo, aunque se detecta un gran deseo de aprender y capacidad de autocontrol, el estudiantado requiere de mayor orientación para la adquisición de habilidades en torno a la autogestión del aprendizaje. Igualmente, se encuentra una relación moderada y positiva entre este enfoque de formación y los PLE. Por último, se visualizan diferencias significativas en el rendimiento académico del alumnado en función de la preparación hacia el aprendizaje autodirigido.La ràpida aparició de les noves tecnologies i l'accés cada cop més globalitzat a internet promouen l'ús massiu de les TIC. Respecte a aquesta qüestió, la construcció i el desenvolupament dels entorns personals d'aprenentatge (EPA) faciliten les habilitats requerides per autodirigir el procés d'adquisició de coneixements. L'objectiu d'aquest estudi és analitzar com perceben l'aprenentatge autodirigit els estudiants universitaris d'últim any de carrera costa-riquenys, com també valorar la relació amb el seu EPA i amb el rendiment acadèmic. Es va fer servir un disseny no experimental i transaccional d'abast correlacional. Es va aplicar un qüestionari amb diferents escales a una mostra probabilística estratificada (n = 1187) de 51 carreres de la Universitat Nacional. Els resultats mostren un nivell alt de preparació cap a l'aprenentatge autodirigit. Tanmateix, encara que es detecta un gran desig d'aprendre i capacitat d'autocontrol, l'alumnat necessita més orientació per tal d'adquirir habilitats sobre l'autogestió de l'aprenentatge. Igualment, es troba una relació moderada i positiva entre aquest enfocament de formació i els EPA. Per últim, es visualitzen diferències significatives al rendiment acadèmic de l'alumnat en funció de la preparació cap a l'aprenentatge autodirigit.The rapid emergence of new technologies and increasingly widespread access to the internet promote the massive use of ICT. Thus, building and developing personal learning environments (PLEs) provides the skills required to self-direct the learning process. The objective of this study is to analyse how university students in Costa Rica in their final year of study perceive self-directed learning, and to evaluate the relationship between PLEs and academic performance. A non-experimental and transactional correlational approach was used. A questionnaire with different scales was applied to a stratified probabilistic sample (n = 1187) of students on 51 study programs at the Universidad Nacional. The results show a high level of acceptance of self-directed learning. However, although a great desire to learn and a high degree of self-control were identified, the student body requires more guidance in acquiring skills surrounding self-management in learning. At the same time, a slight and positive relationship between this educational approach and the PLE was noted. Last, significant differences were seen in the student body's academic performance depending on their response to self-directed learning

Catechol-O-methyltransferase gene haplotypes in Mexican and Spanish patients with fibromyalgia

Autonomic dysfunction is frequent in patients with fibromyalgia (FM). Heart rate variability analyses have demonstrated signs of ongoing sympathetic hyperactivity. Catecholamines are sympathetic neurotransmitters. Catechol-O-methyltransferase (COMT), an enzyme, is the major catecholamine-clearing pathway. There are several single-nucleotide polymorphisms (SNPs) in the COMT gene associated with the different catecholamine-clearing abilities of the COMT enzyme. These SNPs are in linkage disequilibrium and segregate as 'haplotypes'. Healthy females with a particular COMT gene haplotype (ACCG) producing a defective enzyme are more sensitive to painful stimuli. The objective of our study was to define whether women with FM, from two different countries (Mexico and Spain), have the COMT gene haplotypes that have been previously associated with greater sensitivity to pain. All the individuals in the study were female. Fifty-seven Mexican patients and 78 Spanish patients were compared with their respective healthy control groups. All participants filled out the Fibromyalgia Impact Questionnaire (FIQ). Six COMT SNPs (rs2097903, rs6269, rs4633, rs4818, rs4680, and rs165599) were genotyped from peripheral blood DNA. In Spanish patients, there was a significant association between three SNPs (rs6269, rs4818, and rs4680) and the presence of FM when compared with healthy controls. Moreover, in Spanish patients with the 'high pain sensitivity' haplotype (ACCG), the disease, as assessed by the FIQ, was more severe. By contrast, Mexican patients displayed only a weak association between rs6269 and rs165599, and some FIQ subscales. In our group of Spanish patients, there was an association between FM and the COMT haplotype previously associated with high pain sensitivity. This association was not observed in Mexican patients. Studies with a larger sample size are needed in order to verify or amend these preliminary results

Plant species influence on soil C after afforestation of Mediterranean degraded soils

6 figuras.-- Poster presentado en Geophysical Research Abstracts Vol. 17, EGU2015-12121, 2015Increasing C sequestration in terrestrial ecosystems is one of the main current environmental challenges to mitigate climate change. Afforestation of degraded and contaminated lands is one of the key strategies to achieve an increase in C sequestration in ecosystems. Plant species differ in their mechanisms of C-fixation, C allocation into different plant organs, and interaction with soil microorganisms, all these factors influencing the dynamics of soil C following the afforestation of degraded soils. In this work we examine the influence of different woody plant species on soil C dynamics in degraded and afforested Mediterranean soils. The soils were former agricultural lands that were polluted by a mining accident and later afforested with different native plant species. We analysed the effect of four of these species (Olea europaea var. sylvestris Brot., Populus alba L., Pistacia lentiscus L. and Retama sphaerocarpa (L.) Boiss.) on different soil C fractions, soil nutrient availability, microbial activity (soil enzyme activities) and soil CO2 fluxes 15 years after the establishment of the plantations. Results suggest that the influence of the planted trees and shrubs is still limited, being more pronounced in the more acidic and nutrient-poor soils. Litter accumulation varied among species, with the highest C accumulated in the litter under the deciduous species (Populus alba L.). No differences were observed in the amount of total soil organic C among the studied species, or in the concentrations of phenols and sugars in the dissolved organic C (DOC), which might have indicated differences in the biodegradability of the DOC. Microbial biomass and activity was highly influenced by soil pH, and plant species had a significant influence on soil pH in the more acidic site. Soil CO2 fluxes were more influenced by the plant species than total soil C content. Our results suggest that changes in total soil C stocks after the afforestation of degraded Mediterranean soils are hardly detectable at decadal time-scales, and that more dynamic pools and fluxes must be monitored to determine which plant species should be promote to enhance C sequestration capacity.The RECARE project is funded by the European Commission FP7 Programme, ENV.2013.6.2-4 "Sustainable land care in Europe". EU grant agreement: 603498.Peer reviewe