88 research outputs found

    Dinámica eólica y sedimentaria en el sistema dunar de Cala Tirant (costa N de Menorca)

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    [spa]El sistema dunar de Cala Tirant presenta hoy un estado de conservación en recuperación. Su alto dinamismo hace que del análisis fotométrico sea difícil la precisa identificación de morfologías blowout. No obstante, a lo largo de 350 m de frente se pueden apreciar un total de 7 morfologías erosivas. En este artículo, correspondiente a la salida de campo, se comentarán las tipologías de las distintas morfologías erosivas, así como el funcionamiento de un blowout: su dinámica eólica y el transporte sedimentario en condiciones de fuerte viento de Tramuntana.[eng]The dune system of Cala Tirant today presents a state of conservation in recovery. Its high dynamism makes accurate photometric identification of blowout morphologies difficult. However, along 350 m of dune front, a total of 7 erosive morphologies can be detected. In this article, corresponding to the field output, the typologies of the different erosive morphologies will be discussed, as well as the operation of a blowout: its aeolian dynamics and sedimentary transport in conditions of strong Tramuntana wind

    Identification of volatile organic compounds (VOC) emitted from three European orchid species with different pollination strategies : two deceptive orchids (Himantoglossum robertianum and Ophrys apifera) and a rewarding (Gymnadenia conopsea)

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    Volatile organic compounds (VOC) emission was evaluated in the inflorescences of three species of the family Orchidaceae: Himantoglossum robertianum, Ophrys apifera and Gymnadenia conopsea, that comprise three different pollination strategies: non-rewarding food deceptive, non-rewarding sexually deceptive and nectar rewarding, respectively. VOC were dynamically sampled in custom packed glass multi-sorbent cartridge tubes (Carbotrap, Carbopack X and Carboxen 569). A modified Tedlar® gas sampling bag was placed in vivo covering the inflorescence of the studied orchid, a design that prevents the dilution of the VOC mixture emitted by the flower. Multi-sorbent bed tubes were analysed through automatic thermal desorption coupled with a capillary gas chromatography/mass spectrometry detector. A total of 106 different VOC were found in the scents emitted by the three different studied orchids. A 54% of these compounds had already been identified in floral scents. Generally, only 3 compounds were highly abundant in each species: α-pinene, β-pinene and limonene in Himantoglossum robertianum; 1-butanol, butyl ether and caryophyllene in Ophrys apifera; and phenethyl acetate, eugenol and benzaldehyde in Gymnadenia conopsea. The employment of the presented methodologyPostprint (published version

    Les enquestes a pescadors com a instrument per a detectar processos erosius al litoral rocallós de Menorca (Illes Balears)

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    En aquest article s’ha realitzat una enquesta de percepció sobre processos de caigudes de blocs i esllavissades a la població de pescadors professionals i recreatius de l’illa de Menorca. Els resultats indiquen els indrets de la costa on els pescadors aprecien fenòmens geomorfològics de caigudes de blocs. A l’hora, ens permet tenir un punt de partida per a l’estudi dels processos inestables a la costa rocosa de Menorca. S’ha pres una mostra representativa de 48 enquestes a pescadors professionals i 88 enquestes a pescadors recreatius delimitant 39 zones amb processos actius. En el cas dels pescadors professionals s’han pres com a zones de mostreig els ports base de: Maó, sa Nitja, Macaret, Fornells, Ciutadella, Biniancolla, es Grau, Alcalfar, Canutells i cales Fonts. Amb el resultat de les enquestes es troben algunes respostes associades a la manca de blocs de tempesta o tsunami a les costes rocoses que ens han animat a explorar tot el perímetre de la costa de Menorca

    Les enquestes a pescadors com a instrument per a detectar processos erosius al litoral rocallós de Menorca (Illes Balears)

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    En aquest article s'ha realitzat una enquesta de percepció sobre processos de caigudes de blocs i esllavissades a la població de pescadors professionals i recreatius de l'illa de Menorca. Els resultats indiquen els indrets de la costa on els pescadors aprecien fenòmens geomorfològics de caigudes de blocs. A l'hora, ens permet tenir un punt de partida per a l'estudi dels processos inestables a la costa rocosa de Menorca. S'ha pres una mostra representativa de 48 enquestes a pescadors professionals i 88 enquestes a pescadors recreatius delimitant 39 zones amb processos actius. En el cas dels pescadors professionals s'han pres com a zones de mostreig els ports base de: Maó, sa Nitja, Macaret, Fornells, Ciutadella, Biniancolla, es Grau, Alcalfar, Canutells i cales Fonts. Amb el resultat de les enquestes es troben algunes respostes associades a la manca de blocs de tempesta o tsunami a les costes rocoses que ens han animat a explorar tot el perímetre de la costa de Menorca

    Mantos eólicos en la costa septentrional de Menorca: naturaleza y distribución

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    [spa]Han sido analizados un total de 11 mantos eólicos de Menorca (Islas Baleares). Su principal característica es que todos ellos están ubicados en la costa norte de la isla. Pueden agruparse en tres tipos principales: los relacionados con los acantilados verticales, los relacionados con lechos de torrentes, y un tercer tipo intermedio con características de ambos grupos anteriores, que corresponde a torrentes colgados. La génesis y la evolución pueden estar relacionadas con la erosión mecánica y/o movimientos verticales asociados con el nivel del mar eustático en el Holoceno.[eng]Eleven aeolian sand sheets have been studied on the island of Menorca (Balearic Islands). Their principal feature is that they are all located on the north coast of the island. They can be grouped into three main types: those related to vertical cliffs, those related to stream channels, and a third intermediate type with characteristics of both previous groups, which corresponds to hanging channels in the mouths. The genesis and evolution can be related to mechanical erosion and/or vertical movements associated with eustatic sea levels in the Holocene

    Implementing opportunistic spectrum access in LTE-Advanced

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    Long term evolution advanced (LTE-A) has emerged as a promising mobile broadband access technology aiming to cope with the increasing traffic demand in wireless networks. However, the enhanced spectral efficiency offered by LTE-A may become futile without a better management of scarce and overcrowded electromagnetic spectrum. In this sense, cognitive radio (CR) has been proposed as a potential solution to the problem of spectrum scarcity. Among all the mechanisms provided by CR, opportunistic spectrum access (OSA) aims at a dynamic and seamless use of certain licensed bands provided the licensee is not harmfully affected. This operation requires spectral awareness in order to avoid interferences with licensed systems. In spite of implementing some spectrum sensing mechanisms, LTE-A technology lacks other tools that are needed in order to improve the knowledge of the radio environment. This work studies the adoption of a Geo-located data base (Geo-DB) that cooperatively retrieves and maintains information regarding the location of unutilized portions of spectrum potentially available for OSA. Moreover, the potential benefit of this LTE-compliant OSA solution is evaluated using a calibrated simulation tool, by which numerical results allow us to optimally configure the system and show that the proposed opportunistic system is able to significantly improve its performance.The authors would like to thank the funding received from the Ministerio de Ciencia e Innovacion within the Project number TEC2011-27723-C02-02 and from the Ministerio de Industria, Turismo y Comercio TSI-020100-2011-266 funds. This article had been written in the framework of the CELTIC project CP08-001 COMMUNE. Study by X. Gelabert is funded by the BP-DGR 2010 scholarship (ref. 00192). The authors would like to acknowledge the contributions of their colleagues.Osa Ginés, V.; Herranz Claveras, C.; Monserrat Del Río, JF.; Gelabert, X. (2012). Implementing opportunistic spectrum access in LTE-Advanced. EURASIP Journal on Wireless Communications and Networking. 2012(99):1-17. https://doi.org/10.1186/1687-1499-2012-99S117201299Martín-Sacristán D, Monserrat JF, Cabrejas-Peñuelas J, Calabuig D, Garrigas S, Cardona N: On the way towards fourth-generation mobile: 3GPP LTE and LTE-Advanced. EURASIP J Wirel Commun Netw 2009, 2009: 1-10.Ratasuk R, Tolli D, Ghosh A: Carrier aggregation in LTE-Advanced. In IEEE 71st Vehicular Technology Conference (VTC 2010-Spring). Taipei; 2010:1-5.Wang H, Rosa C, Pedersen K: Performance of uplink carrier aggregation in LTE-advanced systems. In IEEE 72nd Vehicular Technology Conference Fall (VTC 2010-Fall). Ottawa; 2010:1-5.Tandra R, Sahai A, Mishra S: What is a spectrum hole and what does it take to recognize one? Proc IEEE 2009, 97(5):824-848.Mitola IJ, Maguire JGQ: Cognitive radio: making software radios more personal. IEEE Personal Commun 1999, 6(4):13-18. 10.1109/98.788210Haykin S: Cognitive radio: brain-empowered wireless communications. IEEE J Sel Areas Commun 2005, 23(2):201-220.IEEE 802.22 Working Group on Wireless Regional Area Networks. [ http://www.ieee802.org/22/ ]ITU-R BT1368: Planning criteria for digital terrestrial television services in the VHF/UHF bands.ITU-R BT1786: Criterion to assess the impact of interference to the terrestrial broadcasting service (BS).Kawade S, Nekovee M: Cognitive radio-based urban wireless broadband in unused TV bands. In 20th International Radioelektronika Conference. Brno; 2010:1-4.Modlic B, Sisul G, Cvitkovic M: Digital dividend--Opportunities for new mobile services. In International Symposium ELMAR 2009 (ELMAR'09). Zadar; 2009:1-8.Zhao X, Guo Z, Guo Q: A cognitive based spectrum sharing scheme for LTE advanced systems. In International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT). Moscow; 2010:965-969.Hussain S, Fernando X: Spectrum sensing in cognitive radio networks: Up-to-date techniques and future challenges. In IEEE Toronto International Conference on Science and Technology for Humanity (TIC-STH). Toronto; 2009:736-741.Xu Y, Sun Y, Li Y, Zhao Y, Zou H: Joint sensing period and transmission time optimization for energy-constrained cognitive radios. EURASIP J Wirel Commun Netw 2010, 2010: 1-16.Yucek T, Arslan H: A survey of spectrum sensing algorithms for cognitive radio applications. IEEE Commun Surv Tutor 2009, 11: 116-130.Cabric D, Mishra S, Brodersen R: Implementation issues in spectrum sensing for cognitive radios. In Conference Record of the Thirty-Eighth Asilomar Conference on Signals, Systems and Computers. Volume 1. Pacific Grove; 2004:772-776.Zeng Y, Liang YC, Hoang A, Peh E: Reliability of spectrum sensing under noise and interference uncertainty. In IEEE International Conference on Communications Workshops, 2009. ICC Workshops. Dresden; 2009:1-5.Bixio L, Ottonello M, Raffetto M, Regazzoni CS: Comparison among cognitive radio architectures for spectrum sensing. EURASIP J Wirel Commun Netw 2011, 2011: 1-18.Mustonen M, Matinmikko M, Mammela A: Cooperative spectrum sensing using quantized soft decision combining. In 4th International Conference on Cognitive Radio Oriented Wireless Networks and Communications, 2009 (CROWNCOM'09). Hannover; 2009:1-5.Xiao L, Liu K, Ma L: A weighted cooperative spectrum sensing in cognitive radio networks. In International Conference on Information Networking and Automation (ICINA). Volume 2. Kunming; 2010:45-48.Pan Q, Chang Y, Zheng R, Zhang X, Wang Y, Yang D: Solution of information exchange for cooperative sensing in cognitive radios. In IEEE Wireless Communications and Networking Conference, 2009 (WCNC'2009). Budapest; 2009:1-4.Masri A, Chiasserini CF, Perotti A: Control information exchange through UWB in cognitive radio networks. In 5th IEEE International Symposium on Wireless Pervasive Computing (ISWPC). Modena; 2010:110-115.Celebi H, Arslan H: Utilization of location information in cognitive wireless networks. IEEE Wirel Commun 2007, 14(4):6-13.FCC: Notice of Proposed Rulemaking, in the Matter of Unlicensed Operation in the TV Broadcast Bands (ET Docket no. 04-186) and Additional Spectrum for Unlicensed.Marcus MJ, Kolodzy P, Lippman A: Reclaiming the vast wasteland: why unlicensed use of the white space in the TV bands will not cause interference to DTV viewers. New America Foundation: wireless future program, tech rep 2005.Nam H, Ghorbel M, Alouini M: Proc. of the Fifth International Conference on Cognitive Radio Oriented. In Proc of the Fifth International Conference on Cognitive Radio Oriented Wireless Networks Communications (CROWNCOM). Cannes; 2010:1-5.IEEE Std 80221-2008: IEEE Standard for Local and Metropolitan Area Networks-Part 21: Media Independent Handover. 2009.3GPP TS 36133: Evolved Universal Terrestrial Radio Access (E-UTRA); Requirements for support of radio resource management.Sesia S, Baker M, Toufik I: LTE, the UMTS long term evolution: from theory to practice. Wiley, New Haven; 2009.Digham FF, Alouini MS, Simon MK: On the energy detection of unknown signals over fading channels. In IEEE International Conference on Communications, 2003 (ICC'03). Volume 5. Anchorage; 2003:3575-3579.Ghasemi A, Sousa ES: Collaborative spectrum sensing for opportunistic access in fading environments. In First IEEE International Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN). Baltimore; 2005:131-136.Gelabert X, Akyildiz IF, Sallent O, Agustí R: Operating point selection for primary and secondary users in cognitive radio networks. Comput Netw 2009, 53(8):1158-1170. 10.1016/j.comnet.2009.02.009Taniuchi K, Ohba Y, Fajardo V, Das S, Tauil M, Cheng YH, Dutta A, Baker D, Yajnik M, Famolari D: IEEE 802.21: media independent handover: features, applicability, and realization. IEEE Commun Mag 2009, 47: 112-120.3GPP TS 36305: Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Stage 2 functional specification of User Equipment (UE) positioning in E-UTRAN.3GPP TS 36355: Evolved Universal Terrestrial Radio Access; LTE Positioning Protocol (LPP).3GPP TS 36455: Evolved Universal Terrestrial Radio Access; LTE Positioning Protocol A (LPPa).Ren W, Zhao Q, Swami A: Power control in cognitive radio networks: how to cross a multi-lane highway. IEEE J Sel Areas Commun 2008, 27(7):1283-1296.3GPP R1-084424: Control Channel Design Issues for Carrier Aggregation in LTE-A.Dajie J, Haiming W, Malkamaki E, Tuomaala E: Principle and performance of semi-persistent scheduling for VoIP in LTE system. In International Conference on Wireless Communications, Networking and Mobile Computing, 2007 (WiCom 2007). Shanghai; 2007:2861-2864.Rajbanshi R, Wyglinski AM, Minden GJ: An efficient implementation of NC-OFDM transceivers for cognitive radios. In Proc of 1st Conf on Cognitive Radio Oriented Wireless Networks and Commun. Mykonos; 2006:1-5.Wellens M, Riihijarvi J, Mahonen P: Modeling primary system activity in dynamic spectrum access networks by aggregated ON/OFF-processes. In 6th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks Workshops, 2009. SECON Workshops'09. Rome; 2009:1-6.3GPP TS 36214: Physical layer; Measurements.Ofuji Y, Morimoto A, Abeta S, Sawahashi M: Comparison of packet scheduling algorithms focusing on user throughput in high speed downlink packet access. In 13th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications. Volume 3. Lis-boa; 2002:1462-1466.ITU-R ITU M2135: Guidelines for evaluation of radio interface technologies for IMT-Advanced 2008

    Secure Virtual Mobile Small Cells: A Stepping Stone Towards 6G

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    YesAs 5th Generation research reaches the twilight, the research community must go beyond 5G and look towards the 2030 connectivity landscape, namely 6G. In this context, this work takes a step towards the 6G vision by proposing a next generation communication platform, which aims to extend the rigid coverage area of fixed deployment networks by considering virtual mobile small cells (MSC) that are created on demand. Relying on emerging computing paradigms such as NFV (Network Function Virtualization) and SDN (Software Defined Networking), these cells can harness radio and networking capability locally reducing protocol signalling latency and overhead. These MSCs constitute an intelligent pool of networking resources that can collaborate to form a wireless network of MSCs providing a communication platform for localized, ubiquitous and reliable connectivity. The technology enablers for implementing the MSC concept are also addressed in terms of virtualization, lightweight wireless security, and energy efficient RF. The benefits of the MSC architecture towards reliable and efficient cell-offloading are demonstrated as a use-case.This project has received funding from the European Union's H2020 research and innovation program under grant agreement H2020-MCSAITN- 2016-SECRET 722424 [2]

    Tsunami hazards in the Catalan Coast, a low-intensity seismic activity area

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    The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-017-2918-zThe potential impacts of tsunamis along the Catalan Coast (NW Mediterranean) are analysed using numerical modelling. The region is characterized by moderate to low seismic activity and by moderate- to low-magnitude earthquakes. However, the occurrence of historical strong earthquakes and the location of several active offshore faults in front of the coast suggest that the possibility of an earthquake-triggered tsunami is not negligible although of low probability. Up to five faults have been identified to generate tsunamis, being the highest associated possible seismic magnitudes of up to 7.6. Coastal flooding and port agitation are characterized using the Worst-case Credible Tsunami Scenario Analysis approach. The results show a multiple fault source contribution to tsunami hazard. The shelf dimensions and the existence of submerged canyons control the tsunami propagation. In wide shelves, waves travelling offshore may become trapped by refraction causing the wave energy to reach the coastline at some distance from the origin. The free surface water elevation increases at the head of the canyons due to the sharp depth gradients. The effects of potential tsunamis would be very harmful in low-lying coastal stretches, such as deltas, with a high population concentration, assets and infrastructures. The Ebro delta appears to be the most exposed coast, and about the 20% of the delta surface is prone to flooding due to its extremely low-lying nature. The activity at Barcelona port will be severely affected by inflow backflow current at the entrance of up to 2 m/s.Peer ReviewedPostprint (author's final draft
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