Fine spatial pattern of an epiphytic lichen species is affected by habitat conditions in two forest types in the Iberian Mediterranean region

Persistence and abundance of species is determined by habitat availability and the ability to disperse and colonize habitats at contrasting spatial scales. Favourable habitat fragments are also heterogeneous in quality, providing differing opportunities for establishment and affecting the population dynamics of a species. Based on these principles, we suggest that the presence and abundance of epiphytes may reflect their dispersal ability, which is primarily determined by the spatial structure of host trees, but also by host quality. To our knowledge there has been no explicit test of the importance of host tree spatial pattern for epiphytes in Mediterranean forests. We hypothesized that performance and host occupancy in a favourable habitat depend on the spatial pattern of host trees, because this pattern affects the dispersal ability of each epiphyte and it also determines the availability of suitable sites for establishment. We tested this hypothesis using new point pattern analysis tools and generalized linear mixed models to investigate the spatial distribution and performance of the epiphytic lichen Lobaria pulmonaria, which inhabits two types of host trees (beeches and Iberian oaks). We tested the effects on L. pulmonaria distribution of tree size, spatial configuration, and host tree identity. We built a model including tree size, stand structure, and several neighbourhood predictors to understand the effect of host tree on L. pulmonaria. We also investigated the relative importance of spatial patterning on the presence and abundance of the species, independently of the host tree configuration. L. pulmonaria distribution was highly dependent on habitat quality for successful establishment, i.e., tree species identity, tree diameter, and several forest stand structure surrogates. For beech trees, tree diameter was the main factor influencing presence and cover of the lichen, although larger lichen-colonized trees were located close to focal trees, i.e., young trees. However, oak diameter was not an important factor, suggesting that bark roughness at all diameters favoured lichen establishment. Our results indicate that L. pulmonaria dispersal is not spatially restricted, but it is dependent on habitat quality. Furthermore, new spatial analysis tools suggested that L. pulmonaria cover exhibits a distinct pattern, although the spatial pattern of tree position and size was random.

Fabrication of sub-100 nm IDT SAW devices on insulating, semiconducting and conductive substrates

This work describes the electron-beam (e-beam) lithography process developed to manufacture nano interdigital transducers (IDTs) to be used in high frequency (GHz) surface acoustic wave (SAW) applications. The combination of electron-beam (e-beam) lithography and lift-off process is shown to be effective in fabricating well-defined IDT finger patterns with a line width below 100 nm with a good yield. Working with insulating piezoelectric substrates brings about e-beam deflection. It is also shown how a very thin organic anti-static layer works well in avoiding this charge accumulation during e-beam lithography on the resist layer. However, the use of this anti-static layer is not required with the insulating piezoelectric layer laying on a semiconducting substrate such as highly doped silicon. The effect of the e-beam dose on a number of different layers (of insulating, insulating on semiconducting, semiconducting, and conductive natures) is provided. Among other advantages, the use of reduced e-beam doses increases the manufacturing time. The principal aim of this work is to explain the interrelation among e-beam dose, substrate nature and IDT structure. An extensive study of the e-beam lithography of long IDT-fingers is provided, in a wide variety of electrode widths, electrode numbers and electrode pitches. It is worthy to highlight that this work shows the influence of the e-beam dose on five substrates of different conductive nature

Fine spatial pattern of an epiphytic lichen species is affected by habitat conditions in two forest types in the Iberian Mediterranean region

Persistence and abundance of species is determined by habitat availability and the ability to disperse and colonize habitats at contrasting spatial scales. Favourable habitat fragments are also heterogeneous in quality, providing differing opportunities for establishment and affecting the population dynamics of a species. Based on these principles, we suggest that the presence and abundance of epiphytes may reflect their dispersal ability, which is primarily determined by the spatial structure of host trees, but also by host quality. To our knowledge there has been no explicit test of the importance of host tree spatial pattern for epiphytes in Mediterranean forests. We hypothesized that performance and host occupancy in a favourable habitat depend on the spatial pattern of host trees, because this pattern affects the dispersal ability of each epiphyte and it also determines the availability of suitable sites for establishment. We tested this hypothesis using new point pattern analysis tools and generalized linear mixed models to investigate the spatial distribution and performance of the epiphytic lichen Lobaria pulmonaria, which inhabits two types of host trees (beeches and Iberian oaks). We tested the effects on L. pulmonaria distribution of tree size, spatial configuration, and host tree identity. We built a model including tree size, stand structure, and several neighbourhood predictors to understand the effect of host tree on L. pulmonaria. We also investigated the relative importance of spatial patterning on the presence and abundance of the species, independently of the host tree configuration. L. pulmonaria distribution was highly dependent on habitat quality for successful establishment, i.e., tree species identity, tree diameter, and several forest stand structure surrogates. For beech trees, tree diameter was the main factor influencing presence and cover of the lichen, although larger lichen-colonized trees were located close to focal trees, i.e., young trees. However, oak diameter was not an important factor, suggesting that bark roughness at all diameters favoured lichen establishment. Our results indicate that L. pulmonaria dispersal is not spatially restricted, but it is dependent on habitat quality. Furthermore, new spatial analysis tools suggested that L. pulmonaria cover exhibits a distinct pattern, although the spatial pattern of tree position and size was random.

Sputter optimization of AlN on diamond substrates for high frequency SAW resonators

The AlN/diamond structure is an attractive combination for SAW devices and its application at high frequencies. In this work, the synthesis of AlN thin films by reactive sputtering has been optimized on diamond substrates in order to process high frequency devices. Polished microcrystalline and as-grown nanocrystalline diamond substrates have been used to deposit AlN of different thickness under equal sputtering conditions. For the smoother substrates, the FWHM of the rocking curve of the (002) AlN peak varies from 3.8° to 2.7° with increasing power. SAW one port resonators have been fabricated on these films, whose electrical characterization (in terms of S11 parameters) is reported.

Fabrication of high frequency SAW resonators using AlN/Diamond/Si technology

The synthesis of AlN on diamond is a great challenge, not only because of the between an AlN/diamond interface, but also because of the high surface roughness of the diamond layers [8, 9]. In the case of microcrystalline diamond, the last problem was solved by polishing. However, polishing nanocrystalline diamond is not straightforward. For the diamond synthesis by CVD, silicon was used as a substrate. The diamond/Si interface presents a smoother diamond than the diamond/air interface. This paper reports on the fabrication of high frequency SAW resonators using AlN/Diamond/Si technology.

Use of DFOT Heat Pulse Method ForWetting Pattern Determination in Drip Irrigation Emitters

Although there are numerous accurate measuring methods to determine soil moisture content in a spot, until very recently there were no precise in situ and in real time methods that were able to measure soil moisture content along a line. By means of the Distributed Fiber Optic Temperature Measurement method or DFOT, the temperature in 0.12 m intervals and long distances (up to 10,000 m) with a high time frequency and an accuracy of +0.2º C is determined. The principle of temperature measurement along a fiber optic cable is based on the thermal sensitivity of the relative intensities of backscattered photons that arise from collisions with electrons in the core of the glass fiber. A laser pulse, generated by the DTS unit, traversing a fiber optic cable will result in backscatter at two frequencies. The DTS quantifies the intensity of these backscattered photons and elapsed time between the pulse and the observed returned light. The intensity of one of the frequencies is strongly dependent on the temperature at the point where the scattering process occurred. The computed temperature is attributed to the position along the cable from which the light was reflected, computed from the time of travel for the light.

Proposal of a dynamic performance index to analyze driving pattern effect on car emissions

The contributions of driver behaviour as well as surrounding infrastructure are decisive on pollutant emissions from vehicles in real traffic situations. This article deals with the preliminary study of the interaction between the dynamic variables recorded in a vehicle (driving pattern) and pollutant emissions produced over a given urban route. It has been established a “dynamic performance index”-DPI, which is calculated from some driving pattern parameters, which in turn depends on traffic congestion level and route characteristics, in order to determine whether the driving has been aggressive, normal or calm. Two passenger cars instrumented with a portable activity measurement system -to record dynamic variables- and on-board emission measurement equipment have been used. This study has shown that smooth driving patterns can reduce up to 80% NOX emissions and up to 20% of fuel in the same route

Signal analysis and feature generation for pattern identification of partial discharges in high-voltage equipment

This paper proposes a method for the identification of different partial discharges (PDs) sources through the analysis of a collection of PD signals acquired with a PD measurement system. This method, robust and sensitive enough to cope with noisy data and external interferences, combines the characterization of each signal from the collection, with a clustering procedure, the CLARA algorithm. Several features are proposed for the characterization of the signals, being the wavelet variances, the frequency estimated with the Prony method, and the energy, the most relevant for the performance of the clustering procedure. The result of the unsupervised classification is a set of clusters each containing those signals which are more similar to each other than to those in other clusters. The analysis of the classification results permits both the identification of different PD sources and the discrimination between original PD signals, reflections, noise and external interferences. The methods and graphical tools detailed in this paper have been coded and published as a contributed package of the R environment under a GNU/GPL license.

Analysis of pattern recognition techniques for in-air signature biometrics

As a result of advances in mobile technology, new services which benefit from the ubiquity of these devices are appearing. Some of these services require the identification of the subject since they may access private user information. In this paper, we propose to identify each user by drawing his/her handwritten signature in the air (in-airsignature). In order to assess the feasibility of an in-airsignature as a biometric feature, we have analysed the performance of several well-known patternrecognitiontechniques—Hidden Markov Models, Bayes classifiers and dynamic time warping—to cope with this problem. Each technique has been tested in the identification of the signatures of 96 individuals. Furthermore, the robustness of each method against spoofing attacks has also been analysed using six impostors who attempted to emulate every signature. The best results in both experiments have been reached by using a technique based on dynamic time warping which carries out the recognition by calculating distances to an average template extracted from several training instances. Finally, a permanence analysis has been carried out in order to assess the stability of in-airsignature over time.

Ultra high frequency thin film saw devices

Durante los últimos años el flujo de datos en la transmisión que tiene lugar en los sistemas de comunicación ha aumentado considerablemente de forma que día a día se requieren más aplicaciones trabajando en un rango de frecuencias muy alto (3-30 GHz). Muchos de estos sistemas de comunicación incluyen dispositivos de onda acústica superficial (SAW) y por tanto se hace necesario el aumento de frecuencia a la que éstos trabajan. Pero este incremento de frecuencia de los dispositivos SAW no sólo es utilizado en los sistemas de comunicación, varios tipos de sensores, por ejemplo, aumentan su sensibilidad cuando la frecuencia a la que trabajan también lo hace. Tradicionalmente los dispositivos SAW se han fabricado sobre cuarzo, LiNbO3 y LiTaO3 principalmente. Sin embargo la principal limitación de estos materiales es su velocidad SAW. Además, debido a la alta temperatura a la que se depositan no pueden ser integrados en la tecnología de fabricación CMOS. El uso de la tecnología de capa delgada, en la que un material piezoeléctrico es depositado sobre un substrato, se está utilizando en las últimas décadas para incrementar la velocidad SAW de la estructura y poder obtener dispositivos trabajando en el rango de frecuencias requerido en la actualidad. Por otra parte, esta tecnología podría ser integrada en el proceso de fabricación CMOS. Durante esta tesis nos hemos centrado en la fabricación de dispositivos SAW trabajando a muy alta frecuencia. Para ello, utilizando la tecnología de capa delgada, hemos utilizado la estructura nitruro de aluminio (AlN) sobre diamante que permite conseguir velocidades SAW del sustrato que no se pueden alcanzar con otros materiales. El depósito de AlN se realizó mediante sputtering reactivo. Durante esta tesis se han realizado diferentes experimentos para optimizar dicho depósito de forma que se han obtenido los parámetros óptimos para los cuales se pueden obtener capas de AlN de alta calidad sobre cualquier tipo de sustrato. Además todo el proceso se realizó a baja temperatura para que el procesado de estos dispositivos pueda ser compatible con la tecnología CMOS. Una vez optimizada la estructura AlN/diamante, mediante litografía por haz de electrones se fabricaron resonadores SAW de tamaño nanométrico que sumado a la alta velocidad resultante de la combinación AlN/diamante nos ha permitido obtener dispositivos trabajando en el rango de 10-28 GHz con un alto factor de calidad y rechazo fuera de la banda. Estás frecuencias y prestaciones no han sido alcanzadas por el momento en resonadores de este tipo. Por otra parte, se han utilizado estos dispositivos para fabricar sensores de presión de alta sensibilidad. Estos dispositivos son afectados altamente por los cambios de temperatura. Se realizó también un exhaustivo estudio de cómo se comportan en temperatura estos resonadores, entre -250ºC y 250ºC (rango de temperaturas no estudiado hasta el momento) diferenciándose dos regiones una a muy baja temperatura en la que el dispositivo muestra un coeficiente de retraso en frecuencia (TCF) relativamente bajo y otra a partir de los -100ºC en la que el TCF es similar al observado en la bibliografía. Por tanto, durante esta tesis se ha optimizado el depósito de AlN sobre diamante para que sea compatible con la tecnología CMOS y permita el procesado de dispositivos trabajando a muy alta frecuencia con altas prestaciones para comunicaciones y sensores. ABSTRACT The increasing volume of information in data transmission systems results in a growing demand of applications working in the super-high-frequency band (3–30 GHz). Most of these systems work with surface acoustic wave (SAW) devices and thus there is a necessity of increasing their resonance frequency. Moreover, sensor application includes this kind of devices. The sensitivity of them is proportional with its frequency. Traditionally, quartz, LiNbO3 and LiTaO3 have been used in the fabrication of SAW devices. These materials suffer from a variety of limitations and in particular they have low SAW velocity as well as being incompatible with the CMOS technology. In order to overcome these problems, thin film technology, where a piezoelectric material is deposited on top of a substrate, has been used during the last decades. The piezoelectric/substrate structure allows to reach the frequencies required nowadays and could be compatible with the mass electronic production CMOS technology. This thesis work focuses on the fabrication of SAW devices working in the super-high-frequency range. Thin film technology has been used in order to get it, especially aluminum nitride (AlN) deposited by reactive sputtering on diamond has been used to increase the SAW velocity. Different experiments were carried out to optimize the parameters for the deposit of high quality AlN on any kind of substrates. In addition, the system was optimized under low temperature and thus this process is CMOS compatible. Once the AlN/diamond was optimized, thanks to the used e-beam lithography, nanometric SAW resonators were fabricated. The combination of the structure and the size of the devices allow the fabrication of devices working in the range of 10-28 GHz with a high quality factor and out of band rejection. These high performances and frequencies have not been reached so far for this kind of devices. Moreover, these devices have been used as high sensitivity pressure sensors. They are affected by temperature changes and thus a wide temperature range (-250ºC to 250ºC) study was done. From this study two regions were observed. At very low temperature, the temperature coefficient of frequency (TCF) is low. From -100ºC upwards the TCF is similar to the one appearing in the literature. Therefore, during this thesis work, the sputtering of AlN on diamond substrates was optimized for the CMOS compatible fabrication of high frequency and high performance SAW devices for communication and sensor application.

High precision pressure sensors based on SAW devices in the GHz range

In this paper, an AlN/free-standing nanocrystalline diamond (NCD) system is proposed in order to process high frequency surface acoustic wave (SAW) resonators for sensing applications. The main problem of synthetic diamond is its high surface roughness that worsens the sputtered AlN quality and hence the device response. In order to study the feasibility of this structure, AlN films from 150 nm up to 1200 nm thick have been deposited on free-standing NCD. We have then analysed the influence of the AlN layer thickness on its crystal quality and device response. Optimized thin films of 300 nm have been used to fabricate of one-port SAW resonators operating in the 10–14 GHz frequency range. A SAW based sensor pressure with a sensibility of 0.33 MHz/bar has been fabricated.

Modelling the spatio-temporal pattern of primary dispersal in stone pine (Pinus pinea L.) stands in the Northern Plateau (Spain)

Natural regeneration in stone pine (Pinus pinea L.) managed forests in the Spanish Northern Plateau is not achieved successfully under current silviculture practices, constituting a main concern for forest managers. We modelled spatio-temporal features of primary dispersal to test whether (a) present low stand densities constrain natural regeneration success and (b) seed release is a climate-controlled process. The present study is based on data collected from a 6 years seed trap experiment considering different regeneration felling intensities. From a spatial perspective, we attempted alternate established kernels under different data distribution assumptions to fit a spatial model able to predict P. pinea seed rain. Due to P. pinea umbrella-like crown, models were adapted to account for crown effect through correction of distances between potential seed arrival locations and seed sources. In addition, individual tree fecundity was assessed independently from existing models, improving parameter estimation stability. Seed rain simulation enabled to calculate seed dispersal indexes for diverse silvicultural regeneration treatments. The selected spatial model of best fit (Weibull, Poisson assumption) predicted a highly clumped dispersal pattern that resulted in a proportion of gaps where no seed arrival is expected (dispersal limitation) between 0.25 and 0.30 for intermediate intensity regeneration fellings and over 0.50 for intense fellings. To describe the temporal pattern, the proportion of seeds released during monthly intervals was modelled as a function of climate variables – rainfall events – through a linear model that considered temporal autocorrelation, whereas cone opening took place over a temperature threshold. Our findings suggest the application of less intensive regeneration fellings, to be carried out after years of successful seedling establishment and, seasonally, subsequent to the main rainfall period (late fall). This schedule would avoid dispersal limitation and would allow for a complete seed release. These modifications in present silviculture practices would produce a more efficient seed shadow in managed stands.

Kinematic pattern of the drag-flick: a case study

The drag-flick is more efficient than hits or pushes when a penalty corner situation is in effect in field hockey. Previous research has studied the biomechanical pattern of the drag-flick, trying to find the cues for an optimal performance. On the other hand, some other studies have examined the most effective visual pick-up of relevant information in shots and goalkeeper anticipation. The aim of this study was to analyse the individual differences in the drag-flick pattern in order to provide relevant information for goalkeepers. One female skilled drag-flicker participated in the study. A VICON optoelectronic sy stem (Oxford Metrics, Oxford, UK) was used to capture the drag-flicks with six cameras. The results showed that the main significant differences between right and left shots (p<0.05) in the stick angles, stick minimum angular velocity and front foot-ball distance were when the front foot heel contacted the floor(T1) and at the minimum velocity of the stick, before the dragging action (T3). The findings showed that the most relevant information might be picked up at the ball-and-stick location before the dragging action.

Optimization of AlN thin layers on diamond substrates for high frequency SAW resonators

AlN/diamond heterostructures are very promising for high frequency surface acoustic wave (SAW) resonators. In their design, the thickness of the piezoelectric film is one of the key parameters. On the other hand, the film material quality and, hence, the device performance, also depend on that thickness. In this work, polished microcrystalline diamond substrates have been used to deposit AlN films by reactive sputtering, from 150 nm up to 3 μm thick. A high degree of the c-axis orientation has been obtained in all cases. SAW one port resonators at high frequency have been fabricated on these films with a proper combination of the film thickness and transducer size.

Super-high-frequency SAW resonators on AlN/Diamond

This letter describes the procedure to manufacture high-performance surface acoustic wave (SAW) resonators on AlN/diamond heterostructures working at frequencies beyond 10 GHz. In the design of SAW devices on AlN/diamond systems, the thickness of the piezoelectric layer is a key parameter. The influence of the film thickness on the SAW device response has been studied. Optimized thin films combined with advanced e-beam lithographic techniques have allowed the fabrication of one-port SAW resonators with finger width and pitch of 200 nm operating in the 10–14 GHz range with up to 36 dB out-of-band rejection.