Theoretical view on the origin and implications of structural distortions in polyoxometalates

Structural features of polyoxometalates (POMs) —versatile inorganic clusters of academic and technological interest— are discussed in the present article. POMs are, in general, very regular structures presenting a high symmetry in most cases. Distortions are, however, important for some electronic and magnetic properties. We herein discuss some particular geometric features that are crucial for the theoretical treatment and comprehension of well-known experimental phenomena. For instance, we have been able to understand and rationalize the geometrical distortions present in molybdenum POMs. Moreover, we can affirm that these geometrical distortions are caused by a pseudo Jahn Teller effect. In what concerns NMR chemical shifts, we present a discussion on the importance of geometry for the correct description of the signals and the key role played by the interatomic distances. Finally, a study on the adsorption of Keggin clusters on silver surfaces shows how the POM structure looses its regular shape to adapt to that new situation

La descoberta de la torre sepulcral de Vilablareix

En el fons Hernández Sanahuja que es guarda a la Reial Societat Arqueològica de Tarragona es conserven uns interessants originals que aclareixen, per una banda, la història de la identificació com a monument funerari romà de la Torratxa de Vilablareix (Gironès) i, simultàniament, proporcionen dades inèdites realment extraordinàries sobre el mausoleu romà de cal Temple (Aiguaviva, Gironès) situat a poc més d’un quilòmetre a migdia de l’altra tomba

A methodology to introduce sustainability into the Final Year Project to foster sustainable engineering projects

The introduction of sustainability skills into higher education curricula is a natural effect of the increasing importance of sustainability in our daily lives. Topics like green computing, sustainable design or environmental engineering have become part of the knowledge required by today’s engineers. Furthermore, we strongly believe that the introduction of this skill will eventually enable future engineers to develop sustainable products, services and projects. The Final Year Project is the last academic stage facing students and a step towards their future professional engineering projects. As such, it constitutes a rehearsal for their professional future and an ideal opportunity for reflecting on whether their Final Year Project is sustainable or not, and to what extent. It also provides a good tool for reviewing the lessons learned about sustainability during the degree course and for applying them in a holistic and integrated way. In this paper, we present a guide that allows both students and advisors to think carefully about the sustainability of engineering projects, in particular the Final Year Project.Postprint (author’s final draft

Wake-up radio systems for cooperative-intelligent transport systems architecture

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Cooperative-Intelligent Transport systems are new applications developed on top of communications between vehicles and between vehicles and fixed infrastructure. Their architecture envisages devices deployed along the routes and streets, transmitting and receiving different kind of messages belonging to different services. Quite often, these devices will be located in isolated places with very low number of vehicles passing nearby. Being in isolated places, these devices will require to be feed with rechargeable batteries and alternative power sources, the usage of which need to be very efficient. The fact of continuously transmitting messages whenever there is no vehicle to receive them demands a solution. In this paper, we propose to use a well-known saving power strategy already used in Internet of Things, the Wake-up Radio systems. As vehicular communications are based on IEEE 802.11 standard, we propose to use a Wake-up Radio system based on this standard as well, being thus no additional hardware needed for the wake-up transmitter. The paper analyses the feasibility of using this solution on several vehicular applications.Peer ReviewedPostprint (author's final draft

IEEE 802.11g performance in presence of beacon control frames

Most studies of the performance of IEEE 802.11 consider scenarios of ad-hoc topology networks and do not contemplate the network broadcast information contained in beacon frames. The paper presents a study of the performance of a WLAN whose infrastructure's topology is such that the access point is in charge of broadcasting the beacon frames. Thus, it is more realistic than previous studies, because beacon frames are usually transmitted in order to announce control information and network identity. Furthermore, in the coverage area, user stations are likely to be working at different data rates, depending on their signal quality. Because beacon frames must be received by all stations, they are transmitted at the lowest data rate operating in the coverage area. The article introduces a mathematical method to calculate the influence of beacon frames on the total throughput, collision probability and delays of the IEEE 802.11g protocol. The model is validated by simulation analysis.Peer Reviewe

Integration of wireless communications in a GIS platform

This paper presents a new developed platform for the Commercialisation of Advanced Services of Geographical Information, focussed in portables devices, and that makes use of the telecommunication networks available today: Internet as the backbone and cellular networks (GSM + GPRS) as access networks. The platform implements a system for commercialising cartographic information in form of vectorial maps for different amount of time, guarantying property rights of the provided information. The problem with vectorial maps is that they have additional information, as points of interest or street names, that is very important to have them updated. So it is more interesting, for both the provider and the customer, to rent the maps for a small period of time, and also for a low fee, than selling them for ever and for a big amount of money. The client accesses to the service using a vectorial map player, that runs over PC or PDA (Personal Digital Assistant) platforms, and using a GPS receiver, it has navigation facilities. Before accessing to the information the player will request authorization to the server. Mobile devices will access Internet, where the server is connected, using WLAN, circuit switched cellular network (GSM) or packet switched cellular network (GPRS). The server side will control user access and download required maps. The platform includes also a system to improve GPS localization (Differential GPS). The communication between the client and the server uses SMS messages of GSM system, one for the request and another for the answer. This operation is very sensitive to response delay and it has been optimised in order to work properly.Peer Reviewe

Study of asymmetric traffic influence on IEEE 802.11 WLAN family, enhancement proposals

This paper is focused on the study of WLAN performance in IEEE 802.11 networks that are in a situation of asymmetric traffic, where the access point (AP) transmits much more than the user stations (US). This situation is very different from the symmetric one, wherein all the stations have the same traffic load. The paper also presents a discussion of the different mechanisms in order to increase AP priority under the asymmetric traffic situation.Peer Reviewe