Infrared tracking system for immersive virtual environments

In this paper, we describe the theoretical foundations and engineering approach of an infrared-optical tracking system specially design for large scale immersive virtual environments (VE) or augmented reality (AR) settings. The system described is capable of tracking independent retro-reflective markers arranged in a 3D structure (ar-tefact) in real time (25Hz), recovering all possible 6 Degrees of Freedom (DOF). These artefacts can be ad-justed to the user’s stereo glasses to track his/her pose while immersed in the VE or AR, or can be used as a 3D input device. The hardware configuration consists in 4 shutter-synchronized cameras attached with band-pass infrared filters and the artefacts are illuminated by infrared array-emitters. The system was specially designed to fit a room with sizes of 5.7m x 2.7m x 3.4 m, which match the dimensions of the CAVE-Hollowspace of Lousal where the system will be deployed. Pilot lab results have shown a latency of 40ms in tracking the pose of two ar-tefacts with 4 infrared markers, achieving a frame-rate of 24.80 fps and showing a mean accuracy of 0.93mm/0.52º and a mean precision of 0.08mm/0.04º, respectively, in overall translation/rotation DOFs, fulfill-ing the system requirements initially defined.info:eu-repo/semantics/publishedVersio

Survival estimates of bycatch individuals discarded from bivalve dredges

The fate of released bycatch is an issue of great interest for fisheries research and management. Survival experiments were carried out to assess the survival capacity of animals damaged and discarded during clam dredging operations. Three common bycatch species, two fish (Trachinus vipera; Dicologlossa cuneata) and one crab (Polybius henslowii), were collected during the sorting of catches from a commercial dredging boat. An arbitrary score scale was used to quantify the type and extent of damage to the organisms. Onboard, damaged individuals were placed in tanks containing seawater which were subsequently transferred to the laboratory. Survival experiments were conducted during the subsequent 48h. D. cuneata exhibited the lowest mortality after 48h (54%), followed by P. henslowii (65%) and T. vipera (81%). Despite the magnitude of the percentage mortalities determined, the average number of individuals estimated to die during a 15 minutes tow (standard commercial fishing time) was relatively small: 1.2, 3.24 and 11 for D. cuneata, T. vipera and P. henslowii, respectively. Nevertheless, when these figures are extrapolated to cover all the dredging fleet the impact of this practice on the populations of the species studied can be significant, particulary for D. cuneata

Sustainability of organic and conventional beef cattle farms in SW Spanish rangelands (‘dehesas’): a comparative study

Organic production in Spain has increased substantially in recent years due to several factors, such as the growing interest of the European Union towards preserving sensitive ecosystems; the potential role of organic production in the socio-economic development of rural areas and the growing consumers' demand for safer and higher quality foods. Within this framework, this paper analyzes the beef sector of SW Spanish rangelands (dehesas). These are traditional systems characteristic of the Iberian Peninsula where native herbaceous vegetation and evergreen species of Quercus provide the basis for extensive beef farms. Alt-hough traditional management in dehesa farms is of vital importance for the sustainability of this particular ecosystem, in the last years many farms have turned to organic production, trying to take advantage both of new subsidies and of new market trends.With this study, we try to evalu-ate the sustainability of conventional and organic beef production systems in dehesas in Extre-madura (SW Spain), trying to determine the level these systems are contributing both to the preservation of this sensitive ecosystem and to the socioeconomic development of the region. To this end, we apply a methodological adaptation of the MESMIS methodology to 90 dehesa beef farms located in Extremadura (SW Spain). MESMIS is based on the evaluation of basic attributes of sustainability that allow one to make a simultaneous and comparative analysis of different types of farms. It has been found that organic farms are the most sustainable, obtaining higher scores than con-ventional farms in stability and self-reliance, and similar scores in productivity, adaptability, and equity. Organic dehesa beef farms show little dependence on external products and services and are more adapted to their environment (lower stocking rates for an optimal use of the system's feedstuff production), those being the clues for their enhanced sustainability

Conversión de sistemas de producción caprinos de áreas desfavorecidas a ganadería ecológica

INTRODUCTION: The Spanish goat sector's crisis has led to the abandonment of a large number of farms. At present, sector's expectations are reduced, which threatens farms' permanence. This in turn means a loss of agricultural biodiversity, reduced economic activity and loss of rural population. In this context, it is necessary to implement strategies to ensure farms' continuity . In this sense, the conversion to the organic model is proposed in the farms analyzed. METHODOLOGY: To study the possibility and feasibility of such conversion an analysis of their structure (technical and economic characteristics), an assessment of farms' sustainability (based on social, economic and environmental parameters) has been carried out. For this purpose, the MESMIS Framework was used

Evaluación de la sostenibilidad de explotaciones caprinas extremeñas en áreas desfavorecidas como herramienta de apoyo en la conversión hacia explotaciones ecológicas.

INTRODUCTION: The Ibores-Villuercas region (located in SW Spain) is known for its dairy goat farms producing cheeses of high quality (P.D.O. Queso Ibores). The present study characterizes such farms and assess their sustainability, as a tool to determine which farms present more feasibility to carry out a conversion to the organic system. This conversion could be used as a marketing tool for these farms, and contribute to local development (both economically and socially), ensuring the maintenance of the farms and rural population while enabling the preservation of valuable landscapes. METHODOLOGY: farms where classified using cluster analysis. Later, a sustainability assessment of the clusters (groups of farms) was carried out. Finally, farms' difficulties and advantages producing under the organic model where predicted. RESULTS and DISCUSSION: 3 groups of farms were obtained. Group 1 farms were intensive ones, using highly-productive dairy breeds fed high proportion of concentrates. Group 2 were semi-extensive of higher surface and mixed with sheeps, where autochthonous and allochthonous races are reared, and management is closer to a traditional one. Finally, group 3 was a traditional one, closer to the orgnaic management, with low stocking rates and native breeds feeding local feed resources. Regarding the attributes of sustainability, group 3 showed advantages in terms of self-management, which is important under the organic system and areas of scarcity of feed resources (such as that studied)

Comparative Sustainability Assessment of Extensive Beef Cattle Farms

This chapter analyzes the sustainability of beef cattle systems of the Spanish Rangelands known as “Dehesas”. These are traditional systems of the Iberian Peninsula where native herbaceous vegetation and evergreen species of Quercus provide the basis for extensive livestock farms. These systems are considered as outstanding High Nature Value (HNV) farming systems and the most extensive agroforestry systems in Europe according to CORINE Land Cover. Beef farms in this area show low stocking rates and a small dependence on foodstuff purchases.However, certain changes have occurred in the last decadesdue to the Common Agricultural Policy (CAP). On the one hand, some farms have become more intensified, as a way to maximize the revenues from the CAP subsidies. On the other hand, many farms have turned to organic production, trying to take advantage both of new subsidies and of new market trends. In this regard, the organic livestock farming model is gaining weight as an option for sustainable production since, according to various authors, these systems have advantages over conventional and intensive systems. In fact, organic production in the area has increased substantially in recent years due to several factors, such as the growing interest of the EU towards preserving sensitive ecosystems, the potential role of organic production in the development of rural areas and the growing consumers’ demand for safer and higher quality foods produced under ethical and environmental standards. In this study, we carried out a comparative assessment of the sustainability of different conventional and organic beef production systems located in dehesa rangelands. The systems analyzed were classified as follows. (i) non-organic farms (Conventional); (ii) organic farms that sold calves at weaning age as conventional ones (Organic 1); (iii) organic farms that fattened and sold their calves as organic (Organic 2). An adaptation of the MESMIS multicriteria framework was applied to calculate sustainability indices for each system. The results showed that the Organic 2 farms scored highest on most of the attributes of sustainability, as well as on the environmental and economic dimensions of sustainability. Thus, they were the most sustainable system (66.55%), followed by the Organic 1 (61.04%) and Conventional ones (56.89%). Despite Organic 2 was the most sustainable system, its implementation is complex due to both the high costs of organic inputs and the weak demand for organic beef. The results also showed that all three types of systems need to improve in certain aspects that are crucial in the current and future context of the livestock sector. These aspects are: reducing the dependence on external feed, implementing more environmentally friendly farming practices, and farm diversification

Piezoresistor sensor fabrication by direct laser writing on hydrogenated amorphous silicon

In this paper we report on the 532 nm Nd:YAG laser-induced crystallization of 10 nm thick boron-doped hydrogenated amorphous silicon thin films deposited on flexible polyimide and on rigid oxidized silicon wafers by hot-wire chemical vapor deposition. The dark conductivity increased from ~10-7 -1cm-1, in the as-deposited films, to ~10 and 50 -1cm-1 after laser irradiation, on rigid and flexible substrates, respectively. Depending on type of substrate, laser power and fluence, a Raman crystalline fraction between 55 and 90% was measured in HWCVD films, which was higher than observed in rf-PECVD films (35 - 55%). Crystallite size remained small in all cases, in the range 6-8 nm. Due to a very high conductivity contrast (>7 orders of magnitude) between amorphous and crystallized regions, it was possible to define conductive paths in the a-Si:H matrix, by mounting the sample on a X-Y software-controlled movable stage under the laser beam, with no need for the usual lithography steps. The resistors scribed by direct laser writing had piezoresistive properties, with positive gauge factor ~1. The details of the laser interaction process with the Si film were revealed by scanning electron microscopy imaging.(undefined

The influence of coastal processes on inner shelf sediment distribution : the Eastern Algarve Shelf (Southern Portugal)

This study examines sediment distribution patterns in the Southeastern Algarve inner shelf (southern Portugal), an area characterized by marked variations in its coastal environment and low continental supply of sediments. The specific goals of this study were to identify the principal sediment sources and the factors influencing sediment transport paths and deposition. A total of 199 samples, collected along the shelf from the Guadiana River mouth to Olhos de Água, were analyzed. Grain-size distribution and parameters were measured for all the samples. Terrigenous and biogenic components of sand were identified in 38 samples, and results analyzed using multivariate non-linear multidimension scaling (MDS) and cluster analysis. Patterns of sediment distribution in this area of the inner shelf vary according to water depth and exhibit significant longshore variation, related mainly to coastal processes (littoral drift and storm currents) and to a lower degree to sediment sources. Sand is dominant at all depths, reflecting the influence of littoral drift in the supply and redistribution of shelf sediments. Fine and gravelsized deposits are significant in specific areas and are usually associated with changes in sediment composition. Five sectors have been identified according to sedimentary dynamics. The results, based on geostatistical and multivariate analysis, have allowed detailed sediment distribution maps to be generated, which represent an update of the existing cartography and serve as a tool for the management of coastal and marine resources. They have been furthermore compared with inner shelf sediment dynamics in other regions worldwide, to distinguish between specific regional responses to forcing mechanisms and processes that are more generalized within this type of shelf environments. In this context, the results obtained results in the Algarve study area are of great interest for the understanding of sediment dynamics of sand dominated inner shelves with reduced continental suppl

Reciprocating wear tests of Al–Si/SiCp composites: a study of the effect of stroke length

The aim of the work described here was to find evidence for the influence of stroke length on the reciprocating wear of aluminium matrix composites. For this purpose, two kinds of tests were performed: reciprocating ball-on-plane geometry experiments to apply stroke in the millimetre range, and fretting tests to study the strokes in the micrometer scale. The relationships between the dissipated energy and the wear volume were established to compare these two different scale tests. The results are discussed in terms of energy approach and of the comparison of the wear mechanisms observed on the wear scars resulting from both tests