Pt-impregnated catalysts on powdery SiC and other commercial supports for the combustion of hydrogen under oxidant conditions

We report the study of the catalytic hydrogen combustion over Pt-impregnated powdery silicon carbide (SiC) using H2PtCl6 as precursor. The reaction was conducted in excess of oxygen. β-SiC was selected for the study because of its thermal conductivity, mechanical properties, chemical inertness and surface area. The obtained Pt particles over SiC were medium size (average particle diameter of 5 nm for 0.5 wt% Pt). The activity of the Pt-impregnated catalyst over SiC was compared to those obtained in oxidized form over TiO2 and Al2O3 commercial supports (Pt particles very small in size, average particle diameter of 1 nm for 0.5 wt% Pt in both cases). The case of a SiO2 support was also discussed. Those Pt/SiC particles were the most active because of their higher contribution of surface Pt0, indicating that partially oxidized surfaces have better activity than those totally oxidized in these conditions. SiC was modified with an acid treatment and thus bigger (average particle diameter of 7 nm for 0.5 wt% Pt) and more active Pt particles were obtained. Durability of the SiC and TiO2 supported catalysts was tested upon 5 cycles and both have shown to be durable and even more active than initially. Exposure to the oxidative reaction mixture activates the catalysts and the effect is more pronounced for the completely oxidized particles. This is due to the surface oxygen chemisorption which activates catalystś surface.Junta de Andalucía PE2012-TEP862Ministerio de Economía y Competitividad CTQ2012-32519, CTQ2015-65918-RConsejo Superior de Investigaciones Científicas PIE-201460E01

Automating SLA-Driven API Development with SLA4OAI

The OpenAPI Specification (OAS) is the de facto standard to describe RESTful APIs from a functional perspective. OAS has been a success due to its simple model and the wide ecosystem of tools supporting the SLA-Driven API development lifecycle. Unfortunately, the current OAS scope ignores crucial information for an API such as its Service Level Agreement (SLA). Therefore, in terms of description and management of non-functional information, the disadvantages of not having a standard include the vendor lock-in and prevent the ecosystem to grow and handle extra functional aspects. In this paper, we present SLA4OAI, pioneering in extending OAS not only allowing the specification of SLAs, but also supporting some stages of the SLA-Driven API lifecycle with an open-source ecosystem. Finally, we validate our proposal having modeled 5488 limitations in 148 plans of 35 real-world APIs and show an initial interest from the industry with 600 and 1900 downloads and installs of the SLA Instrumentation Library and the SLA Engine.Ministerio de Economía y Competitividad TIN2015-70560-RMinisterio de Ciencia, Innovación y Universidades RTI2018-101204-B-C21Ministerio de Educación, Cultura y Deporte FPU15/0298

Fostering SLA-Driven API Specifications

Software architecture tendencies are shifting to a microservice paradigm. In this context, RESTful APIs are being established the standard of integration. API designer often identifies two key issues to be competitive in such growing market. On the one hand, the generation of accurate documentation of the behavior and capabilities of the API to promote its usage; on the other hand, the design of a pricing plan that fits into the potential API user’s needs. Besides the increasing number of API modeling alternatives is emerging, there is a lack of proposals on the definition of flexible pricing plans usually contained in the Service Level Agreements (SLAs). In this paper we propose two different modeling techniques for the description of SLA in a RESTful API context: iAgree and SLA4OAI.Ministerio de Economía y Competitividad TIN2015-70560-RJunta de Andalucía P12-TIC-1867Ministerio de Economía y Competitividad TIN2014-53986-RED

Governing the service-chain: Challenges ahead

As Information Systems are evolving into an ecosystem of services, organizations face the persistent challenge of IT governance. In such a context, Cloud Computing shift has supported a growing service chain that has transformed the business model from industry. In this position paper we outline the dimensions of this service chain reality and the role of Service Level Agreement as a foundation to support its governance challenge

Single-Board-Computer Clusters for Cloudlet Computing in Internet of Things

The number of connected sensors and devices is expected to increase to billions in the near future. However, centralised cloud-computing data centres present various challenges to meet the requirements inherent to Internet of Things (IoT) workloads, such as low latency, high throughput and bandwidth constraints. Edge computing is becoming the standard computing paradigm for latency-sensitive real-time IoT workloads, since it addresses the aforementioned limitations related to centralised cloud-computing models. Such a paradigm relies on bringing computation close to the source of data, which presents serious operational challenges for large-scale cloud-computing providers. In this work, we present an architecture composed of low-cost Single-Board-Computer clusters near to data sources, and centralised cloud-computing data centres. The proposed cost-efficient model may be employed as an alternative to fog computing to meet real-time IoT workload requirements while keeping scalability. We include an extensive empirical analysis to assess the suitability of single-board-computer clusters as cost-effective edge-computing micro data centres. Additionally, we compare the proposed architecture with traditional cloudlet and cloud architectures, and evaluate them through extensive simulation. We finally show that acquisition costs can be drastically reduced while keeping performance levels in data-intensive IoT use cases.Ministerio de Economía y Competitividad TIN2017-82113-C2-1-RMinisterio de Economía y Competitividad RTI2018-098062-A-I00European Union’s Horizon 2020 No. 754489Science Foundation Ireland grant 13/RC/209

Multiwavelength optical observations of chromospherically active binary systems V. FF UMa (2RE J0933+624): a system with orbital period variation

This is the fifth paper in a series aimed at studying the chromospheres of active binary systems using several optical spectroscopic indicators to obtain or improve orbital solution and fundamental stellar parameters. We present here the study of FF UMa (2RE J0933+624), a recently discovered, X-ray/EUV selected, active binary with strong H_alpha emission. The objectives of this work are, to find orbital solutions and define stellar parameters from precise radial velocities and carry out an extensive study of the optical indicators of chromospheric activity. We obtained high resolution echelle spectroscopic observations during five observing runs from 1998 to 2004. We found radial velocities by cross correlation with radial velocity standard stars to achieve the best orbital solution. We also measured rotational velocity by cross-correlation techniques and have studied the kinematic by galactic space- velocity components (U, V, W) and Eggen criteria. Finally, we have determined the chromospheric contribution in optical spectroscopic indicators, from Ca II H & K to Ca II IRT lines, using the spectral subtraction technique. We have found that this system presents an orbital period variation, higher than previously detected in other RS CVn systems. We determined an improved orbital solution, finding a circular orbit with a period of 3.274 days. We derived the stellar parameters, confirming the subgiant nature of the primary component and obtained rotational velocities (vsini), of 33.57 km/s and 32.38 km/s for the primary and secondary components respectively. From our kinematic study, we can deduce its membership to the Castor moving group. Finally, the activity study has given us a better understanding of the possible mechanisms that produce the orbital period variation.Comment: Latex file with 16 pages, 18 figures. Available at http://www.ucm.es/info/Astrof/invest/actividad/actividad_pub.html Accepted for publication in: Astronomy & Astrophysics (A&A

ELeCTRA: Induced Usage Limitations Calculation in RESTful APIs

As software architecture design is evolving to microservice paradigms, RESTful APIs become the building blocks of applications. In such a scenario, a growing market of APIs is proliferating and developers face the challenges to take advantage of this reality. For example, third-party APIs typically define different usage limitations depending on the purchased Service Level Agreement (SLA) and, consequently, performing a manual analysis of external APIs and their impact in a microservice architecture is a complex and tedious task. In this demonstration paper, we present ELeCTRA, a tool to automate the analysis of induced usage limitations in an API, derived from its usage of external APIs. This tool takes the structural, conversational and SLA specifications of the API, generates a visual dependency graph and translates the problem into a constraint satisfaction optimization problem (CSOP) to obtain the optimal usage limitations.Ministerio de Economía y Competitividad TIN2015-70560-RJunta de Andalucía P12–TIC–1867Ministerio de Economía y Competitividad TIN2014-53986-REDTMinisterio de Educación, Cultura y Deporte FPU15/0298

Origen de la radiodifusión pirata comercial

La importancia de las estaciones piratas comerciales en el contexto europeo fue tan grande que sus emisiones hicieron cambiar toda la programación de la radiodifusión de nuestro continente, pasando a una programación basada en la música ligera. Analizaremos el origen de este fenómeno para obtener una tipología y las repercusiones que tuvo este fenómeno en los modelos radiofónicos contemporáneos.The relevance of commercial pirate radio stations in Europe has been so far-reaching that its broadcasts have totally transformed all radio programming on this continent. The present article analyses the origin of this phenomenon in order to obtain a typology and see the repercussions this phenomenon has had on contemporary radio models