Minimizing buffer requirements in video-on-demand servers

23rd Euromicro Conference EUROMICRO 97: 'New Frontiers of Information Technology', Budapest, Hungary, 1-4 Sept 1997Memory management is a key issue when designing cost effective video on demand servers. State of the art techniques, like double buffering, allocate buffers in a per stream basis and require huge amounts of memory. We propose a buffering policy, namely Single Pair of Buffers, that dramatically reduces server memory requirements by reserving a pair of buffers per storage device. By considering in detail disk and network interaction, we have also identified the particular conditions under which this policy can be successfully applied to engineer video on demand servers. Reduction factors of two orders of magnitude compared to the double buffering approach can be obtained. Current disk and network parameters make this technique feasible.Publicad

Photonic molecules for improving the optical response of macroporous silicon photonic crystals for gas sensing purposes

In this paper, we report the benefits of working with photonic molecules in macroporous silicon photonic crystals. In particular, we theoretically and experimentally demonstrate that the optical properties of a resonant peak produced by a single photonic atom of 2.6 µm wide can be sequentially improved if a second and a third cavity of the same length are introduced in the structure. As a consequence of that, the base of the peak is reduced from 500 nm to 100 nm, while its amplitude remains constant, increasing its Q-factor from its initial value of 25 up to 175. In addition, the bandgap is enlarged almost twice and the noise within it is mostly eliminated. In this study we also provide a way of reducing the amplitude of one or two peaks, depending whether we are in the two- or three-cavity case, by modifying the length of the involved photonic molecules so that the remainder can be used to measure gas by spectroscopic methods.Postprint (published version

Pérdida del pulido de diferentes mármoles comerciales en ambientes salinos

Este artículo cuantifica la pérdida de pulido que sufren los mármoles cuando entran en contacto con disoluciones salinas. La pérdida de pulido (cuantificada como el incremento de rugosidad superficial) es debida a la disolución que sufren los cristales de calcita, y se compara esta tasa de disolución con la estabilidad de los mármoles dolomíticos.Este trabajo se enmarca en el Proyecto Maternas (S0505-MAT/000094, Comunidad de Madrid)

Relationship between Emotional Intelligence and Optimism According to Gender and Social Context (Urban vs. Rural)

The aim of the present study was to evaluate the influence of Emotional Intelligence on optimistic-pessimistic attitudes in a sample of 177 people from the Autonomous Community of Andalusia (Spain). The sample consisted of 102 women (57.60%) and 75 men (42.40%), who live in different localities depending on the number of residents (urban and rural context). The instruments used in the study were: The Life Orientation Test Revised (LOT-R), Emotional Quotient Inventory (EQi-C), and Wong-Law Emotional Intelligence Scale (WLEIS-S). The results indicated that Emotional Intelligence was positively related to optimism and negatively related to pessimism (p < 0.01). In addition, pessimism was found to be significantly related to the rural context, but not to the urban context. The multigroup Structural Equations model was developed for the gender variable, and it had good structural validity (chi(2) = 96.485; RMSEA = 0.056; GFI = 0.901; CFI = 0.900; IFI = 0.907), which was greater for the female gender. The practical consequences of this study help to understand the usefulness of EQ on optimism-pessimism as an attribute between urban vs. rural areas and the effect of living in socio-culturally different environments

Study of resonant modes in a 700 nm pitch macroporous silicon photonic crystal

In this study the modes produced by a defect inserted in a macroporous silicon (MP) photonic crystal (PC) have been studied theoretical and experimentally. In particular, the transmitted and reflected spectra have been analyzed for variations in the defect’s length and width. The performed simulations show that the resonant frequency is more easily adjusted for the fabricated samples by length tuning rather than width. The optimum resonance peak results when centered in the PC bandgap. The changes in the defect geometry result in small variations of the optical response of the PC. The resonance frequency is most sensitive to length variations, while the mode linewidth shows greater change with the defect width variation. Several MPS photonic crystals were fabricated by the electrochemical etching (EE) process with optical response in the range of 5.8 µm to 6.5 µm. Results of the characterization are in good agreement with simulations. Further samples were fabricated consisting of ordered modulated pores with a pitch of 700 nm. This allowed to reduce the vertical periodicity and therefore to have the optical response in the range of 4.4 µm to 4.8 µm. To our knowledge, modes working in this range of wavelengths have not been previously reported in 3-d MPS structures. Experimental results match with simulations, showing a linear relationship between the defect’s length and working frequency inside the bandgap. We demonstrate the possibility of tailoring the resonance peak in both ranges of wavelengths, where the principal absorption lines of different gases in the mid infrared are placed. This makes these structures very promising for their application to compact gas sensors.Postprint (author's final draft

A QoS-Driven ISP Selection Mechanism for IPv6 Multi-homed Sites

A global solution for the provision of QoS in IPng sites must include ISP selection based on per-application requirements. In this article we present a new site-local architecture for QoS-driven ISP selection in multi-homed domains, performed in a per application basis. This architecture proposes the novel use of existent network services, a new type of routing header, and the modification of address selection mechanisms to take into account QoS requirements. This proposal is an evolution of current technology, and therefore precludes the addition of new protocols, enabling fast deployment. The sitelocal scope of the proposed solution results in ISP transparency and thus in ISP independency.This research was supported by the LONG (Laboratories Over the Next Generation Networks) project IST-1999-20393.Publicad

Travertine of Baños de Mula. A stone with sedimentological and archaeological interest

Los travertinos coloreados de Baños de Mula fueron utilizados como roca dimensional entre otros sitios, en el Teatro Romano de Cartagena (Travertino Rojo de Mula). Esta roca tiene buenas propiedades mecánicas y buen comportamiento hídrico. Estas propiedades presentan fuerte anisotropía, relacionada con su característica estructura bandeada definida visualmente por cambios en la coloración y en la distribución de los poros. Sus características texturales, muestran el predominio de niveles constituidos por cristales fibrosos y fibroso-radiados, con una fase cementante tardía de oxihidróxidos de Fe, así como morfologías micríticas del tipo de colonias bacterianas. Ambos rasgos pueden relacionarse con actividad bacteriana. Todos estos datos apuntan a favor de una génesis relacionada con aguas termales. Este hidrotermalismo está en relación con fallas activas y se mantiene activo en la actualidad (Balneario de Baños de Mula).The coloured travertine of the Baños de Mula,were used as dimensional stone among other sites in the Roman Theatre in Cartagena (Red Mula Travertine). This rock has good mechanical properties and water behavior. These properties show strong anisotropy related to the characteristic bedding planes visually defined by changes in the color intensity and pore distribution. Their textural features show the prevalence of layers consisting of fibrous and fibrous-radiated crystals with a late stage cementing Fe oxyhydroxides and micritic aggregates following colonial bacterial morphologies. Both features may be related to bacterial activity. All these data point in favor of a genesis related upwelling of thermal waters. These hydrothermal processes are connected with hydrothermal circulation along the active faults, and are manifested at present in the hot springs of Baños de Mula.Este trabajo ha sido parcialmente subvencionado por el proyecto Geomateriales (P2009/MAT-1629) de la Comunidad de Madrid

Thermal emission of macroporous silicon chirped photonic crystals

Postprint (author's final draft

Using Mobile Devices for Improving Learning Outcomes and Teachers’ Professionalization

Teaching in higher education is changing due to the influence of technology. More and more technological tools are replacing old teaching methods and strategies. Thus, mobile devices are being positioned as a key tool for new ways of understanding educational practices. The present paper responds to a systematic review about the benefits that mobile devices have for university students’ learning. Using inclusion and exclusion criteria in theWeb of Science and Scopus databases, 16 articles were selected to argue why Mobile learning (Mlearning) has become a modern innovative approach. The results point to an improvement in students’ learning through Mlearning, factors that encourage the use of mobile devices in universities have been identified, and e ective mobile applications in improving teaching and learning processes have been presented. The inclusion of this methodology requires a new role for teachers, whose characterization is also specified

Distribution and Socio-spatial Segregation of cruise ship workers in Cozumel, Mexico

The cruise industry is one of the most profitable businesses in the world having a constant growth since the 1980’s. However, it is important to mention that this success has been reached in part due to the workforce in the vessels, better known as cruise ship crew members.As well as any other type of tourism, visitors have several effects on ports of call when vessels berth in ports of call. But even when there is knowledge on the effects of cruise tourism in the destinations (mainly caused by tourists), there is a scarcity of literature in terms of issues related to the cruise ship staff on land.In addition to the above, information about the activities and behaviour of the cruise workers, the knowledge of their specific distribution and socio-spatial segregation according to their hierarchies and nationalities during their free time in ports of call is practically null.Therefore, the aim of this research work is to point out the distribution of cruise ship workers in order to demonstrate their segregation in the Island of Cozumel, Mexico, according to the nation they come from and their position at work.Findings demonstrate that there are 79 different sites visited by crew members in Cozumel Island. It has also been identified that their distribution and socio-spatial segregation on the island is related to their hierarchies at work and nationalities, which could lead to a remarkable socioeconomic influence during their free time in the destination.